Refine
Year of publication
Document Type
- Article (92)
- Doctoral Thesis (56)
Has Fulltext
- yes (148)
Is part of the Bibliography
- no (148)
Keywords
- - (65)
- climate change (17)
- dendrochronology (9)
- paludiculture (7)
- forest ecology (6)
- peatland (6)
- rewetting (6)
- Jahresring (5)
- Moor (5)
- boreal forest (5)
Institute
- Institut für Botanik und Landschaftsökologie & Botanischer Garten (148) (remove)
Publisher
- MDPI (33)
- Wiley (21)
- Frontiers Media S.A. (20)
- Springer Nature (7)
- IOP Publishing (4)
- SAGE Publications (3)
- Nature Publishing Group (2)
- Copernicus (1)
Im Rahmen eines Forschungsprojekts im Bereich der Odermündung wurde ein Pflanzentest für aquatische Verunreinigungen gesucht. Der Test wurde nach einem Testprotokoll von Everiss (1979) etabliert. Als Endpunkte gingen die Frischmasse und die Gesamtsprossen ein. Die Testlösungen wurden aus einer konzentrierten Mischung von 7 Schwermetallen und Arsen (As, Hg, Cd, Cr, Cu, Ni, Pb, Zn) und als Einzelsubstanzlösungen hergestellt. Die Auswertungen erfolgten in Prozent bezogen auf die Kontrolle sowie varianzanalytisch nach OECD (2002). In 100facher NKO (NKO = mittlere Konzentration Oderwasser Oberhalb der Nachweisgrenze) wurde eine schwere Schädigung durch alle Gemische verursacht. Das Gemisch ohne Cr schädigte am stärksten. In 10facher NKO konnte eine Wachstumshemmung nachgewiesen werden. Bei 1facher NKO zeigte sich eine geringe Beeinflussung. Als Einzelstoff war Cu in 100facher NKO am stärksten toxisch, gefolgt von Zn, Ni und Cd. As, Pb, Hg und Cr wirkten nicht eindeutig wachstumshemmend. In 10facher NKO war bei Cd, Cu und Zn noch Schädigung vorhanden. Kupfer wirkte auch in der 1fachen NKO noch schädigend. Bei Cd zeigte sich noch eine Reduktion des Sprosswachstums, aber keine Frischmassereduktion. Der L. minor - Test ist sensitiv und eignet sich als Screeningtest für unbekannte Gewässerproben. Er stellt eine gute Ergänzung zu anderen Biotestverfahren dar. Für eine umwelttoxikologische Einschätzung wird anhand der erzielten Ergebnisse ein Schädigungsmodell vorgeschlagen.
Im Manu Nationalpark im südöstlichen Tieflandregenwald Perus leben die Matsiguenka der Dorfgemeinschaften Tayakome und Yomibato. Zur Erwirtschaftung dringend benötigter Basisgüter begannen sie im Jahr 1997 mit dem Bau einer Touristenherberge. Die vorliegende Studie untersucht das tradierte Wirtschaftssystem dieser Dorfgemeinschaften und die Einflüsse neuer Wirtschaftsformen, insbesondere der Herberge sowie des Nationalparks. Bisher brachte die Herberge nicht die von den Matsiguenka erwünschten wirtschaftlichen Erfolge, so dass sie zur Deckung ihrer Grundbedürfnisse weiterhin auf Spenden verschiedener Organisationen angewiesen sind. Die Einflüsse durch die Herberge auf das sehr traditionelle Wirtschaftssystem der Matsiguenka sind bisher gering. Da Tourismus derzeit die einzige Möglichkeit darstellt, von den Matsiguenka erwünschte Einkommen zu erzielen, und sich gleichzeitig stabilisierend auf das Wirtschaftssystem der Matsiguenka auswirken kann, stellt die Beteiligung im Tourismusgeschäft eine Chance für eine nachhaltige Entwicklung im Nationalpark Manu dar. Um diese Ziele zu erreichen, ist aber die verstärkte Zusammenarbeit mit Tourismusunternehmen und Nationalparkverwaltung erforderlich. Außerdem müssen an den aktuellen Wissensstand der Matsiguenka angepasste Beteiligungsformen gefunden werden. Hierfür bietet sich die Ausbildung eines Co-Managementsystems in der touristischen Zone des Nationalparks an, an dem die Nationalparkverwaltung, die Matsiguenka sowie die Tourismusunternehmen beteiligt sind.
For many years, rangeland ecologists have debated about whether the state of semi-arid and arid rangelands is the expression of an ecological equilibrium or non-equilibrium dynamics reached in response to grazing livestock. Since the problem has been considered at different spatial scales, it is recognised that the competing concepts of equilibrium and non-equilibrium dynamics need to be integrated. Furthermore, the role of environmental variables as vegetation driving factors has long been ignored in the discussion on grazing effects on ecosystems. Present thesis, examines the dependence of plant communities on environmental in particular site-ecological conditions in three ecosystems of Western Mongolia established along a precipitation gradient to detect the vegetation-driving ecological factors involved. Furthermore, grazing impact is exemplary assessed in a desert steppe at additional spatial scales of plant communities and population. At the landscape level, a classification of plant communities in dependence on environmental conditions is carried out. Additionally, the investigations focused on the impact of grazing on soil and on the occurrence of grazing-mediated plant communities. Data were sampled along an altitudinal gradient between 1150 m to 3050 m a.s.l. from arid lowland with desert steppe via semi-arid mountain steppe to humid alpine belt. Within each altitudinal belt, data sampling was carried out along grazing gradients, established from grazing hot spots to areas distant from them. By means of an environmentally based vegetation classification, factors with highest explanation values for largest variation in vegetation were identified and considered as most responsible for vegetation patterns. To validate and affirm the classification, three different statistical methods are applied: environmentally adjusted table work of vegetation relevés supported by cluster analysis of species distribution, detrended correspondence analysis of vegetation data separately from environmental data, and the principle component analysis of only environmental data. Vegetation-driving factors change along the altitudinal gradient from abiotic forces in the desert steppe, as e.g. altitude and soil texture, to abiotic and biotic forces in the alpine belt represented by soil texture, soil nutrients and grazing. Vegetation and soil of all ecosystems respond to grazing but with different patterns and to a different extent. While desert steppe does not indicate grazing communities, mountain steppe demonstrates grazing communities at fertilised sites and alpine belt at nutrients depleted sites. Thus, the grazing sensitiveness of the ecosystems is assumed to be linked with plant productivity and the role of vegetation as site-determining factor (Chapter 2). To examine grazing impact at lower spatial scales on desert steppe as the ecosystem with lowest grazing sensitiveness at the landscape scale, at community scale the total number of species, the total vegetation cover, the percentage of annual species, the cover of annual species, and properties of soil nutrient along gradients of grazing intensity within three different communities were assessed. Vegetation parameters respond to grazing in different ways, and the responses of the same parameters vary between plant communities. Correlations with grazing intensity indicate only partly statistical significance. Significant correlations of grazing intensity with concentrations of soil nutrient point to eutrophication in two communities. A comparison of vegetation and soil properties refers to a greater indirect influence of grazing via increased soil nutrients than the direct effect on vegetation (Chapter 4). At the population level, data about stand density, aboveground biomass, individual plant weight, and the proportion of flowering plants of the dominant dwarf semi-shrub Artemisia xerophytica were collected along a grazing gradient. Soil data were used to distinguish between grazing and edaphic influences. All parameters of Artemisia xerophytica reflect the assumed gradient of grazing intensity up to 800 m distance from the grazing hot spot. As grazing pressure decreases, plant density and total biomass per plot increase. The average shrub weight, an indicator of plant vitality, is related to both: distance from the grazing hot spot and stand density, which may be explained by additional intraspecific competition at higher densities. At a longer distance, these effects are masked by variations in soil parameters determining water availability, leading to quite similar degradation forms. These results are in contrast to other studies carried out at the scale of plant communities which did not detect significant changes along a grazing gradient. One explanation is the different map scale: the study took place only within a single plant community comparing populations of one species (Chapter 3). The comparative study demonstrates that even arid desert steppes of western Mongolia display equilibrial and non-equilibrial properties, depending on the observational scale: while no grazing mediated plant communities could be identified at the landscape scale as predicted by the non-equlilibrium model, at the community level vegetation parameters imply an intermediate position between equilibrium and non-equilibrium system. At the population level, the results clearly reflect the grazing gradient as predicted by the equilibrium model (Chapter 4). As a consequence, the assessment of vegetation dynamics and grazing impact in rangelands requires a multiple-scale approach that duly considers different vegetation properties responding differently to grazing, climatic and edaphic variability at different spatial scales. It is further suggested, that future research should draw comparisons between landscapes that co-evolved with herbivory, and those that did without (Chapter 4).
Vegetation dynamics on abandoned terraces of Sicily: the course and driving factors of succession
(2007)
Secondary succession processes have been widely studied in Europe for some agroecosystems, but not for terraced ones. The first part of the present study focuses on a description of the plant communities involved in secondary succession processes on Sicily (Italy) a) from a floristic and structural point of view and b) from a species diversity point of view. In order to obtain these results, 129 vegetation relevés (sensu Braun-Blanquet) were made on abandoned terraces in five of the main terraced areas of Siciliy: 1) the Aeolian Islands, 2) Pantelleria Island, 3) Mt. Etna, 4) the Palermo Mts. and 5) the Hyblaean Plateau. Only abandoned vineyards or grain crop fields were selected as sample plots, always 50 m2-sized. The results of biodiversity evaluation by t-tests and ANOVA showed that vascular plant diversity is linked to disturbance regime and to abiotic factors (especially geological substrate). Especially grazing increases species richness. Moreover, it was found that on limestone species richness is higher than on volcanic substrates. Vegetation relevés were also analysed with DCA and TWINSPAN. The resulting 14 sample plot groups (= clusters) were then used to check the dynamic relations. From a floristic point of view, plant communities involved in secondary succession processes on Sicilian terraces are quite different between and within the five study areas. This is mainly due to different substrate and bioclimatic conditions. Moreover, vegetation is strongly influenced by abandonment age and disturbance status. If no disturbance biases succession, then plant communities evolve rather rapidly (30-50 years) to maquis communities. If frequent fires or intense grazing occur, secondary succession is blocked in a "steady state". The second part of the present study focuses on the colonization mechanisms of old fields by woody species. In a first section, the existence of 1) the neighbourhood effect and 2) the safe-site effect are checked by analyzing 51 transect relevés, made up of 357 subplot relevés (1x1m). The transects were made in target fields 1) with older neighbour (i.e. old succession stage characterized by maquis communities) and 2) with older neighbour absent within a 100 m-distance. All woody species individuals were counted, recording if they grew within the influence of a potential safe site (former crop plants of vine and the terrace wall base). Data evaluation by Kruskal-Wallis ANOVA and Mann-Whitney Rank Sum confirmed the existence of the two effects. Moreover, it was shown that animals as dispersal vectors strongly influence these effects. For the neighbourhood effect, seed dispersal distance is the crucial point, while for the safe site effect 1) passive facilitation (i.e. animals tend to create heterogeneous seed rain patterns because they frequent certain microhabitats more often than others) and 2) active facilitation (i.e. the positive influence of an existing woody or herbaceous plant individual on the establishment or the growth of another one) are crucial. The second section describes the performance of establishment of Quercus ilex L. in different microsites of terraced old fields. In November 2004, acorns were buried on a North-facing slope and on a South-facing slope in five different microsites: 1) under vine plants, 2) at wall bases, 3) under the canopies of isolated shrubs, 4) between small rock accumulations and 5) in open spaces (i.e. outside of any of the previously named microsites). In monthly checks, seedling emergence, survival, height and leaf number were recorded. Moreover, in April and July were measured air temperature and air humidity in the different microsites. Overall emergence rate was 52.4% (n = 1,020). More seedlings emerged on the South-facing slope (S; 59.8%) than on the North-facing slope (N; 45.0%). Emergence was higher when acorns were buried under vine plants and at the wall base than in other microsites of the old fields. At the end of the experiment (September 2006), 45.3% of all emerged seedlings were still alive (29.2% on N, 58.9% on S). Survival was higher in general on the South-facing slope, and higher under vine plants and at the wall base than in the open spaces of the old fields. From literature, it is known that seed vitality, seed germination and seedling survival of Quercus ilex are favoured by shady, wet and fresh conditions. The temperature and air humidity measurements showed that at the wall base, under vine plants and under isolated shrubs environmental conditions are milder than in open spaces. However, even if temperature and relative air humidity seem to play an important role for Quercus ilex seedling emergence and survival, they did not unambiguously explain the differences between the safe site types. A factor of major importance is probably soil moisture. As a last part, the present study discusses what does the obtained results mean for terrace landscape conservation and biodiversity management.
Anorganische Stickstoffformen, wie Nitrat oder Nitrit, dienen in Pflanzen als Quelle für die enzymatische Bildung des Signalmoleküls Stickstoffmonoxid (NO). In Wurzeln wird NO an der apoplastischen Seite der Plasmamembran (PM) durch die Nitrit:NO-Reduktase (NI-NOR) gebildet, die für Nitrit eine hohe Affinität aufweist. Die dafür benötigten Elektronen stammen aus der Oxidation von Succinat, wobei in vitro auch Elektronen aus reduziertem Cytochrom c akzeptiert werden. Zur fluoreszenzmikroskopischen Lokalisierung der NI-NOR (in planta) innerhalb der Tabakwurzeln (Nicotiana tabacum cv. Samsun) wurden DAF-Farbstoffe (Diaminofluoresceine) eingesetzt, die sich jedoch aufgrund zahlreicher NO-unspezifische Reaktionen zum Nachweis der NI-NOR unter den gegebenen experimentellen Bedingungen nicht eigneten. Die Bestimmung und Quantifizierung der NI-NOR-Aktivität in vitro, an isolierten PM-Vesikeln, solubilisierten PM-Proteinen und partiell gereinigten PM-Proteinen, erfolgte mittels Chemilumineszenzanalyse. Neben NO wurde unter Anwendung der Membran-Inlet-Massenspektrometrie an PM-Vesikeln außerdem die Bildung von N2O und NO2 nachgewiesen. In Abhängigkeit von der externen Nitraternährung der Tabakpflanzen bestand ein Zusammenhang zwischen der NI-NOR-Aktivität und der Kolonisierungsrate der Wurzeln mit dem vesikulär-arbuskulären Mykorrhizapilz Glomus mosseae, wobei geringe NI-NOR-Aktivitäten unter Stickstoffmangelbedingungen mit hohen Kolonisierungsraten und umgekehrt hohe NI-NOR-Aktivitäten bei optimaler Nitraternährung mit geringen Kolonisierungsraten korrelierten. Die NI-NOR-Aktivität wurde konzentrationsabhängig und reversibel durch die Anwesenheit von Sauerstoff gehemmt und erreichte bei einer Luftsauerstoffkonzentration von 21 % noch etwa 22 % ihrer ursprünglichen, unter anoxischen Bedingungen gemessenen Aktivität. Um die Identität dieses Enzyms über massenspektrometrische Analysen zu klären, wurde die NI-NOR ausgehend von isolierten PM-Vesikeln aus Tabakwurzeln durch Solubilisierung sowie über chromatographische und gelelektrophoretische Trennungsmethoden aufgereinigt. Mit Hilfe der Massenspektrometrie wurden vor allem verschiedene Aquaporine und Kanäle sowie einige noch unbekannte Proteine identifiziert, bei denen es sich möglicherweise um die NI-NOR handeln könnte. Eine Oxidoreduktase, als möglicher Kandidat für die NI-NOR, wurde jedoch nicht gefunden.
Kenntnisse über Strukturen und Dynamik natürlicher und naturnaher Wälder sind die Voraussetzung für naturnahe Waldbewirtschaftung. Die Ziele der Arbeit waren deshalb die Rekonstruktion von Waldzusammensetzung und Dynamik sowie die Identifizierung der natürlichen bzw. naturnahen Waldgesellschaften im Ablagerungsgebiet der Grundmoräne des letzten Stadiums der Weichselvereisung in Mitteleuropa. Das Untersuchungsgebiet, der Eldenaer Wald, ist ein 407 ha großes Naturschutzgebiet nahe Greifswald und liegt in einer flachwelligen Grundmoränenlandschaft mit nährstoff- und basenreichen Böden. Die Vegetation wird heute vom Eschen-Buchenwald (Fraxino excelsioris-Fagetum sylvaticae) dominiert, in dem auch Acer pseudoplatanus und A. platanoides, Prunus avium, Ulmus glabra, Carpinus betulus und als Nutzungsrelikt Quercus robur vorkommen. Für die Vegetationsrekonstruktion wurden an sechs Bohrkernen aus sechs im Untersuchungsgebiet verteilt liegenden Senken Mikrofossilien und z. T. Makrofossilien analysiert sowie der Glühverlust bestimmt. Die zeitliche Einordnung erfolgte mit 25 14C-AMS-Datierungen. Für die untersuchten Proben wurden Altersangaben inter- und extrapoliert. Weiterhin wurden historische Akten und Karten ausgewertet. Für die Rekonstruktion der Vegetation in der nahen Umgebung der Untersuchungspunkte (UP) wurde eine Methode zur Trennung von (extra)lokalen und regionalen Signalen der Mikrofossil-Typen entwickelt. Dabei werden Mikrofossil-Werte der UP mit den regionalen Daten eines Bohrkerns aus dem Greifswalder Bodden (Bucht der südlichen Ostsee) verglichen. (Extra)lokale Anteile zeigen sich in Form von überhöhten Werten im Vergleich zu den regionalen Werten. Der Vergleich wurde getrennt für Mikrofossil-Typen, die sich schlecht bzw. gut erhalten, durchgeführt, um die Unterbewertung der ersteren zu verringern. Mit Hilfe von Korrekturfaktoren (ANDERSEN 1970, 1984) wurden aus dem (extra)lokalen Anteil der Gehölz-Pollen die etwaigen Anteile der Gehölze an der gehölzbestandenen Fläche der frischen bis trockenen Standorten im Umkreis von etwa 100 m um den UP rekonstruiert. Der Offenheitsgrad der Vegetation wurde aus dem Auftreten indikativer Mikrofossil-Typen abgeleitet. Die rekonstruierte Vegetation innerhalb der Senken bildeten hauptsächlich nasse Erlenwälder. Durch anthropogene Entwässerungen und andere Eingriffe bildeten sich Röhrichte, Birken- und Weidengehölze sowie Erlen-Eschenwälder. Die Vegetation der frischen bis trockenen Standorte im Umkreis der Hohlformen war sehr unterschiedlich ausgebildet und wechselte auch an den verschiedenen UP sehr stark. Der Vergleich der UP zeigte, dass im Zeitabschnitt von AD 200 - 700, außer an einem UP, keine Hinweise auf Nutzungseinflüsse auftraten. Trotzdem waren die Gehölzbestände als Folge früherer menschlicher Aktivitäten z. T. noch sehr stark von Zwischenwaldarten (Acer, Fraxinus, Ulmus) geprägt. Nur an zwei Standorten traten auch über diesen Zeitabschnitt hinaus relativ stabile, von Tilia bzw. Fagus dominierte und nicht nachweisbar von menschlicher Aktivität beeinflusste Gehölzspektren auf. Ab AD 1100 sind nach und nach an allen UP massive Veränderungen im Gehölzspektrum nachweisbar, die mit dem wachsenden Nutzungsdruck infolge der slawischen Besiedlung, der Klostergründung (AD 1199) und den Dorfgründungen (ab AD 1250) einhergingen. Erst im Zeitraum AD 1820 - 2000 stellten sich mit der Einführung der geregelten Forstwirtschaft an fast allen Standorten ähnliche, von Fraxinus und Fagus dominierte Gehölzspektren ein. Mit Hilfe von Cluster-Analyse und Detrended Correspondence Analysis aller rekonstruierten Gehölzbestände wurden vier typische Gesellschaften der Gehölzvegetation der letzten 2000 Jahre herausgearbeitet. Fraxinus-Acer-Quercus-Bestände und Carpinus-Fagus-Quercus-Bestände stellen Vor- und/oder Zwischenwälder dar, die sich mit der Wiederbewaldung von Offenflächen einstellten und aus denen sich Schlusswälder entwickelten. (Betula-)Corylus-Tilia-Bestände beinhalten Schlusswälder, die noch bis etwa AD 1500 im Untersuchungsgebiet existierten. Die Fraxinus-Fagus-Bestände sind ebenfalls Schlusswälder, die fast im gesamten Untersuchungszeitraum nachgewiesen wurden. Aus den Untersuchungen wurde deutlich, dass die Entwicklung der Waldbestände stark durch anthropogene Einflüsse geprägt war. Das Verschwinden der Tilia-bestimmten Bestände und die Ausbreitung von Fagus wurden durch menschliche Aktivitäten ausgelöst. Das Gattungsspektrum der heute dominierenden Waldgesellschaft, des Eschen-Buchenwaldes (Fraxino excelsioris-Fagetum sylvaticae), konnte am Standort EXB bis ins 1. Jh. AD auch in nutzungsfreien Phasen zurückverfolgt werden, so dass es als natürlich gelten kann.
To uncover the genetic structure of Populus euphratica forests along the Tarim River in Xinjiang, China, a PCR set of eight microsatellite markers was established. 18 primer pairs originally developed for P. tremuloides and P. trichocarpa were screened for amplification in P. euphratica. The eight most variable loci were selected for further genotyping experiments. Subsequently, two multiplex PCR assays, each containing four loci, were set up and optimized. Three populations containing altogether 436 trees were used to characterize the selected loci. The set was found to be moderately polymorphic (mean expected heterozygosity = 0.57). The resolution was sufficient to discriminate even siblings with high confidence (PID = 1.81x10-5). Cumulative exclusion probabilities were 0.89 (single parent), 0.98 (paternity), and 1.00 (parent pair) and proved the set’s suitability for parentage analysis. Practical and theoretical analysis of consequences of genotyping errors in this semi-clonal plant showed that the vast majority of errors (62.1%) lead to division of identical genotypes. Merging of different genotypes was found to be a very rare case (0.4%). This always leads to an overestimation of genotypes. A similarity threshold of one allele difference between two genotypes to be regarded as being identical lead to an underestimation of clonal richness and genotype number of one per cent compared to an overestimation of more than 20 per cent without such a threshold. Allowing a certain amount of variation is therefore expected to reflect the clonal structure better than an analysis that considers exact matches only. Using a combination of morphological and molecular analyses, a first study demonstrated that root suckers are clearly distinguished from seedlings in their root architecture. Root suckering starts when trees are 10–15 years old and bridges distances of up to 40 m at a time. Root suckers depend on their parent tree for at least five years and are expected to have a higher mortality than generatively grown trees. Molecular analysis of old growth stands revealed a highly variable proportion of clonal growth between different stands. In the study area, the proportion of clonality decreases with distance to the main river bed (R = 0.31 at the site closest to the main river, R = 0.97 at the site farthest away from the river). An analysis of the history of river movements at different sites indicates a dependency of clonal growth on the frequency of ground water replenishment by the yearly floods. Genetic differentiation among the stands in the study area is low (FST = 0.055), and isolation by distance was not detectable (P = 0.058). Also, the river does not function as a vector for directed gene flow in downstream direction (P > 0.11). The forests are therefore considered to be one large panmictic metapopulation with unrestricted gene flow. Clonal growth does not lead to higher final stand densities (P = 0.99) and is obviously not of crucial importance for stand survival. Furthermore, analysis of vitality measures and size differences indicate that root suckers are in disadvantage both in vitality and in survival rate compared to seedlings. In this light, a possible function of clonal growth as a luxury strategy to enhance a genetic individual’s reproduction success under good site conditions can be discussed. The genetic structure of the (meta)population bears direct implications for management and conversation of the Tugai forest in Xinjiang. Due to the low degree of differentiation and the unhindered gene flow even small, fragmented, or isolated populations have conservational value, thereby clearly answering the SLOSS question (a single large or several small protected areas) in the latter sense. More than that, non-clonal stands with the highest amount of genotypic diversity can be easily identified on satellite and aerial images. Selection of such stands for conservation is therefore possible without expensive and time-consuming molecular analyses.
Vegetation dynamics and carbon sequestration of Holocene alder (Alnus glutinosa) carrs of NE Germany
(2010)
Erlenwälder auf Moorstandorten werden oft als Zeichen von Moordegradation und Torfoxidation gewertet, aber erlenholzreiche Moorablagerungen (teilweise mehrere Meter tief) sind unter anderem in Nordostdeutschland weit verbreitet. Die Genese von Erlen-Holztorfen wurde bisher überwiegend durch das Konzept der „Verdrängungstorfbildung“ erklärt. Hierbei wird ein von gehölzfreier Vegetation akkumulierter Torf nach einer Grundwasserabsenkung durch nachträglich einwachsende Baumwurzeln verändert. Dieses Prinzip ist aber auf tiefgründige Erlen-Holztorfe nicht übertragbar, da Alnus glutinosa auf naturnahen Moorstandorten meist nur wenige Dezimeter tief wurzelt. Anliegen der vorliegenden Dissertation mit dem Titel „Vegetation dynamics and carbon sequestration of Holocene alder (Alnus glutinosa) carrs in NE Germany“ war die Identifizierung torfbildender Erlenwälder. Die torfbildende Vegetation, die Wasserstände während der Torfbildung und die Vegetationsdynamik dieser bewaldeten Niedermoore wurden durch Analysen von Makrofossilien, Pollen und sonstigen Mikrofossilien (u.a. Pilz-, Pflanzen-, und tierische Reste) rekonstruiert. Hierbei wurden in enger Kooperation mit dem Promotionsvorhaben von Frau Anja Prager (Non-pollen palynomorphs [NPPs] from modern alder carrs [NE Germany] - Tools for reconstructing past vegetation and site conditions) ca. 150 bisher unbekannte Mikrofossilien beschrieben und teilweise identifiziert. Die Datenauswertung wurde anhand von Fossilien-Diagrammen und statistischen Methoden (DCA, Clusteranalysis; Broken Stick Analysis) durchgeführt. Zur Altersbestimmung erfolgten 14C-AMS-Datierungen und der Kohlenstoffgehalt wurde über die Bestimmung der Trockenrohdichte ermittelt, wobei ein durchschnittlicher Kohlenstoffanteil von 56% angenommen wurde. Die untersuchten Erlen-Holztorfe wurden überwiegend direkt in Erlenwäldern abgelagert („Echter Bruchwaldtorf“); sind aber auch teilweise als Verdrängungstorfe aus vorherigen Seggentorfen entstanden oder in von Weiden dominierten Gehölzen gebildet worden. Die jährlichen Medianwasserstände der torfbildenden Erlenwälder lagen einerseits über Flur („sehr nass“-„very wet“) und zum anderen 0 bis 10 cm unter Flur („nass“ - „wet“). Die Vegetationszusammensetzung der sehr nassen Erlenwälder ähnelte teilweise dem Wasserfeder-Erlen-Wald und in einem Fall dem Zweizahn-Erlen-Bruchgehölz. Die nassen Erlenwälder konnten nicht auf der Ebene von Vegetationsformen rekonstruiert werden; charakteristisch war das häufige Auftreten von Urtica und eine Carex-dominierte Krautschicht. Über einen Vergleich der Mikrofossilien der Erlenholz-Tofe mit Mikrofossilien von Oberflächenproben aus rezenten Erlenwäldern konnten die Medianwasserstände nasser, torf-akkumulierender Erlenwälder auf 0-10 cm unter Flur festgelegt werden. Alle untersuchten Profile zeigten eine zyklische Bewaldung mit Zwischenphasen von Offenvegetation (meist Seggenriede). Als Bindeglieder zwischen Erlenwald und Seggenried traten teilweise Weidengebüsche auf, welche sich mitunter auch langfristiger etablieren konnten. Die zyklische Vegetationsentwicklung von Seggenrieden, Weidengebüschen und Erlenwäldern basierte fast ausschließlich auf einem schwankenden Wasserangebot im Moor. Dieses war fast immer die Folge von zyklischen Ent- und Wiederbewaldungen der umliegenden, grundwasserfernen Standorte durch den Menschen. Die „Echten Bruchwaldtorfe“ sind unter verschiedenen hydrologischen Bedingungen entstanden (Verlandungs-, Versumpfungs-, Überrieselungs- und Überflutungsmoor). Die Kohlenstoff-Akkumulationsraten („LORCA“-long-term apparent rate of carbon accumulation) liegen zwischen 31-44 g C m-2 yr-1 in sehr nassen und 50-81 g C m-2 yr-1 in nassen Erlenwäldern. Die höheren Akkumulationsraten in nassen Erlenwäldern können durch die deutlich steigende Produktivität von Erlen-Wäldern schon bei leicht sinkenden mittleren Wasserständen erklärt werden. Eine Verringerung der durchschnittlichen Wasserstände von über Flur zu leicht unter Flur führt annähernd zu einer Verdopplung der Primärproduktion von oberirdischem Holz und Wurzelholz. Dadurch gelangt auch ein größerer Anteil von Wurzelholz in den dauerhaft wassergesättigten Bereich. Da mit sinkenden Wasserständen auch die oxidative Zersetzung zunimmt, ist für die teilweise sehr hohen Torfakkumulationsraten in Erlenwäldern die Zersetzungsresistenz von Holz (Lignin) von zentraler Bedeutung. Die Akkumulationsraten nasser Erlenwälder übersteigen die borealer Waldmoore deutlich und erreichen die Größenordnung der Kohlenstoffakkumulation in den tropischen Waldmooren Süddostasiens. Die vorliegende Dissertation belegt die weitverbreitete und oft umfangreiche Torf- bzw. Kohlenstoffakkumulation in Holozänen Erlen-Wäldern Nordostdeutschlands.
This dissertation evaluates the effects of site conditions and livestock grazing on the vegetation of Azerbaijan’s winter pastures. We improved methods to estimate grazing intensity in vast rangelands and enhanced an approach to detect discontinuities in vegetation changes along environmental gradients. All analyses use field data from the semi-arid rangelands of Gobustan and Jeiranchel, at the foothills of the Greater Caucasus mountains. The data set comprises 313 vegetation relevés, each sized 100 m², based on a pre-stratification using topographical parameters. Additionally, we included data from farm transects and exclosure experiments. For each plot, selected site and soil variables were determined. VEGETATION AND SITE CONDITIONS: By means of cluster analysis, we derived 16 vegetation types with a total of 272 vascular plant species. Our vegetation classification, which is closely linked to site conditions, is an important groundwork for adapted rangeland management and monitoring. The study areas are dominated by semi-deserts with a high coverage of dwarf shrubs, and the mean number of vascular plant species was found to be about 28 per 100 m². According to ordination analysis (NMDS), species composition changes primarily along the altitudinal gradient, gradually proceeding from the Salsola nodulosa semi-deserts of the lowest parts (below 300 m a.s.l.) to the Salsola ericoides and Artemisia lerchiana semi-deserts of the upper regions (300–650 m a.s.l.). Soil salinity and carbonate concentration decrease as altitude increases. A second gradient reflects grazing intensity. One plant community that is typically found on intensively grazed sites in the vicinity of farmyards stands apart from the rest, which are subject to lower grazing and trampling pressures. A third factor that differentiates plant communities is the sand concentration of the soils. Additionally, communities that occur on steep slopes differ from communities that occur on level terrain. EXCLOSURE EXPERIMENTS: Exclosure experiments revealed that short-time abandonment of grazing leads to an increase in the number of annual species, in vegetation coverage, and in the heights of forbs and grasses. Clipping experiments indicated that the herbaceous species show hardly any compensatory growth in response to grazing. ESTIMATING GRAZING INTENSITY: A recurrent theoretical problem in rangeland research is the spatial modelling of grazing intensity around grazing hotspots like farms or watering places, the so called piospheres. In a widely used approach, grazing intensity is assumed to decrease in direct proportion to the distance from a hotspot. The resulting response patterns, which relate characteristics of the vegetation or site conditions to grazing intensity, are often nonlinear, and have been interpreted as indicating threshold changes or diff erent state-and-transitions along grazing gradients. However, we show that these ‘thresholds’ are usually geometrical artefacts. Taking into account the concentric structure of grazing hotspots, we suggest a new approach that approximates grazing intensity as the ratio of the total number of livestock kept at the farm to the distance between a given plot and the hotspot centre. Our approach is a simple yet significant improvement over current approaches because it enables us to merge or compare data from different sampling sites and because the approximation is in direct proportion to other grazing indicators like dung density or soil salinity. SPECIES TURNOVER PATTERNS: Combining our new grazing pressure model with species presence/absence data, we modelled vascular plant species responses, patterns of species richness and species turnover along grazing gradients on farm transects in Gobustan. The derived typical species response pattern along the finite grazing gradient is a sigmoid decrease. Species richness declines monotonically with increasing grazing intensity and thus conforms to generally acknowledged assumptions on the relationship between species richness and grazing pressure in semi-arid rangelands. Species turnover along the gradient was calculated using the slopes of species response curves. At first sight, the resulting pattern gives evidence for a discontinuous change. However, it ranges within the 95 % confidence interval of a null model based on assumptions of the individualistic continuum concept. Thus, species composition seems to change continuously along grazing gradients in Gobustan. This new null model approach can probably be adapted and applied to all ecological gradients and is useful for the validation of individualcontinuum or community concepts.
Peatlands cover only about 3% of the terrestrial surface but are significant players in the global carbon (C) cycle and the climate system, since they store roughly one quarter of the global soil carbon (C) and are among the largest natural sources of methane (CH4). Since the resulting feedbacks on the climate system are uncertain, research efforts aim at identifying key processes and quantifying the C exchange from ecosystem to regional and global scales. To identify peatland ecosystem dynamics requires analysis of yet different scales. The key scale for their C dynamics is the microform scale, which is the smallest entity of the system. To estimate ecosystem dynamics, up-scaling from the microform scale is needed. Up-scaling demands (1) a correct estimation of the spatial heterogeneity and (2) the correct aggregation. In this thesis, the traditional spatial weighting of microform fluxes by the microform distribution is evaluated by (1) analyzing the flux calculation procedure, (2) investigating the effect of the resolution of the landcover maps on the up-scaling and by (3) cross-evaluating the up-scaling result with the directly measured ecosystem flux. Eventually, it is evaluated how these dynamics are considered in a mechanistic ecosystem model (LPJ-WHyMe). CH4 fluxes were measured on the microform scale with the closed chamber technique and on the ecosystem scale with the eddy covariance (EC) technique. The quantification of microform fluxes relies on the correct flux calculation. Since only few gas samples are taken during the closure period, traditionally the linear regression is applied when calculating CH4 fluxes from chamber measurements. Still, the chamber itself affects the diffusion gradient between peat and chamber atmosphere resulting in a theoretically non-linear concentration increase in the chamber. Using data with six data points per measurement from different microform types it is tested whether the linear or exponential regression fits the data better. In the majority of cases, the linear regression fits best. However, the exponential concentration change might still not be detectable resulting in an underestimation of the ’real‘ flux and the test of different techniqes to estimate the slope of a non-linear function with small sample amounts is recommended. To define the spatial heterogeneity of the peatland surface, the application of remote sensing techniques offer the advantage of supplying area-wide information with less uncertainty when compared to vegetation mapping along transects. However, the required resolution to resolve the microform distribution is <1m which in this study was derived from near-aerial photography. Besides for up-scaling, the resulting high-resolution landcover map was used in combination with a footprint model to analyze (1) the effect of landcover on the directly measured ecosystem flux and (2) its spatial representativeness. It was shown that fluctuations of the measured ecosystem flux over periods of several days could be explained by changes of the landcover composition in the source area of the EC measurements. The estimated budget was slightly biased towards the higher emissions from lawns which could be corrected. Still, the seasonal ecosystem CH4 budget was higher than the estimate derived from the up-scaling of microform fluxes. This is most likely due to an underestimation of microform fluxes by the chamber technique. Generally, the budget estimate derived from EC measurements was more accurate, i.e., characterized by less uncertainty than the up-scaled estimate. The developed approach depends on (1) identification and accurate measurements of all relevant microform types and (2) on spatial information which should be smaller than the footprint size of the EC measurements and available on the scale relevant for the studied process, i.e., the microform scale. The demonstrated effect of microform dynamics on the ecosystem flux highlights the importance of dealing with spatial heterogeneity of ecosystems in mechanistic modelling. For example, in LPJ-WHyMe, the ecosystem flux is simulated with mean input variables as water table level. To investigate its model performance, flux data from the rather homogeneous peatland margin and the more heterogeneous peatland centre were compared with the model output. At the homogeneous peatland margin, the ecosystem flux was clearly dominated (with a contribution of 91%) by one microform flux. In this case, one water table level as input variable could be used to estimate the ecosystem flux. However, for a heterogeneous site such as the peatland centre in this study, only one mean water table would simulate a mean microform flux but not the ecosystem flux. Consequently, it is recommended to incorporate at least one high-emitting and one low-emitting microform type in the model to increase the model performance.
Carbon dioxide (CO2) is one of the most important factors of the Earth’s carbon cycle. Peatlands are well-known to be a long term sink for atmospheric carbon dioxide. Under changing environmental conditions, the carbon balance and hence the CO2 fluxes can be significantly changed, and peatlands may even become a significant atmospheric carbon source. To be able to predict the changes in climatic conditions and their effects on ecosystems, it is important to understand the contemporary CO2 exchange of the ecosystems. Many studies on peatland CO2 fluxes have been conducted in the boreal zone of North America and Scandinavia. Still little scientific evidence is available from peatland ecosystems of boreal Russia. This dissertation presents the detailed investigation of CO2 dynamics and the relevant processes and environmental factors from the boreal peatland site Ust-Pojeg (61°56'N, 50°13'E) in Komi Republic, northwest Russia. On the small spatial scale (microform), the investigated peatland was characterised by high variability in vegetation composition and coverage as well as in water table level which resulted in large variability in CO2 fluxes not only between the microform types but also within one microform type. The cumulative flux over the investigation period for the different microforms ranged from strong CO2 sources to CO2 sinks. An area-weighted estimate for the entire peatland showed that it was a CO2 source for the investigation period, which was characterised by average conditions in terms of precipitation and temperature. The CO2 fluxes were measured at different scales: by the closed chamber method at the microform scale and by the eddy covariance technique at the ecosystem scale. Three different upscaling methods were used to compare the fluxes. Irrespective of the upscaling methods, the discrepancies between the estimates based on the upscaled chamber measurements and estimates based on measurements by the eddy covariance technique were high. The high spatial heterogeneity of the vegetation and the water table level and thus of the CO2 fluxes were recognised as reasons for high potential errors when upscaling CO2 fluxes from the microform to the ecosystem level. Large discrepancies were also observed in comparison between measured CO2 fluxes and CO2 estimates based on the mechanistic ecosystem model LPJ-GUESS. Insufficient model forcing may have led to errors in the timing of the onset and the end of the growing season, and the modelled vegetation did not always reproduce the observed vegetation. These two factors may have led to the discrepancies in the model-measurement comparison. Although the closed chamber technique is widely used for measurements of CO2 fluxes between ecosystems and the atmosphere, the errors which might occur during the measurement itself or which are associated with the used measurement devices as well as the flux calculation from chamber-based CO2 concentration data are still under discussion. The study showed that the CO2 fluxes measured by the closed chamber method can be overestimated during low-turbulence nighttime conditions and can be seriously biased by inappropriate application of linear regression for the flux calculation. The methodological studies were conducted at the boreal peatland Salmisuo in eastern Finland (62°46'N, 30°58'E). The methods developed in this dissertation could contribute significantly to improved CO2 flux estimates. VI
Northern peatlands are ecosystems with unique hydrological properties, storing about 400-500 Gt of carbon. As the production rate of organic material is higher than its decomposition, which is slowed down in the wet and cold environment, peatlands store a great amount of carbon. Carbon assimilated from the atmosphere during photosynthesis by plants is partly lost due to autotrophic and heterotrophic respiration as carbon dioxide (CO2), as methane (CH4) or/and as dissolved organic carbon. The proportion of each carbon component is strongly controlled by environmental conditions as temperature, radiation, precipitation and subsequent water table changes and active role of vegetation. With predicted changes in the global climate, changes in the influence of environmental parameters on peatland ecology are expected. Thus thorough research is essential for a better understanding of mechanisms which influence carbon cycling in peatlands. In this thesis, various components of the carbon cycle were studied at two boreal peatland sites (Ust Pojeg in Komi Republic in Russian Federation and Salmisuo in Eastern Finland) using the micrometeorological eddy covariance method. The focus was placed on the temporal changes of the controlling parameters, ranging from a few days during short snow thawing through the rest of the year. At the Salmisuo site, two measurement seasons allowed to address possible inter-annual variation. We observed that diurnal variations in methane emissions which are typically controlled by vegetation during the growing season, might appear during snow melt as a result of the influence of physical factors rather than biological factors. The diurnal pattern in methane emissions was caused by the interaction of the freeze-thaw cycle and near urface turbulence. During the night time, when surface temperatures fell below zero and caused formation of the ice layer, methane emissions were only around 0.8 mg m-2 h-1, however after the increase in temperature and melting of the ice layer they reached peak values of around 3 mg m-2 h-1. The near surface turbulence had a significant influence on methane emissions, however only after the thawing of the ice layer. The effect of changing environmental parameters over the year was further elaborated on a carbon dioxide time series from the Ust Pojeg site. The generally accepted effects of temperature on ecosystem respiration during the night are not stable throughout the year and can change rapidly during the growing season. Using moving window regression analysis I could show that the strength of the exponential relationship between ecosystem respiration and temperature is changing during the year. This was in correspondence with recent publications elaborating on sub-seasonal changes of the controlling parameters. In general, measurements from the Ust Pojeg site represent estimates of annual CO2 and CH4 fluxes with an annual carbon balance of -94.5 g C m-2 and a new contribution to the quantification of trace gases emissions from a Russian boreal peatland. The inter-annual comparison of net ecosystem exchange (NEE) measurements with previously published data on CH4 and DOC flux from the Salmisuo site showed that the NEE of CO2 is the most important component of the carbon balance at this site. However, primary production was not responsible for the inter-annual changes in NEE. Rather, the effects of water table position during the year had a strong influence on ecosystem respiration, which was probably due to the influence on soil respiration, and higher NEE was observed during the year with smaller primary production, but higher water table levels. The effects of higher precipitation and higher water table during the wet year were shown to increase CH4 flux and the export of DOC, but their effects could not compensate for changes in ecosystem respiration. In the presented thesis intra- and inter- annual changes in carbon flux components and their controls, in our case attributed mostly to hydrological conditions in combination with other environmental parameters as temperature and the role of peatland vegetation, are discussed.
Recent climate change has affected the forest system comprehensively. Northern hemisphere elevational treelines are considered as a key environment for monitoring the effects of current anthropogenic climate change. Moreover, trees from these areas are also widely employed in paleo-climate reconstructions. The stability of the tree growth climate relationship under current scenario is crucial for all tree ring based climate researches. It is important to investigate how trees respond to this rapid environmental change at altitudinal treelines. Tree cores from 21 treeline sites of three species (Pinus tabulaeformis, Picea crassifolia, and Sabina przewalskii) from Northeastern Tibetan have been conducted in this thesis. The instable correlations between tree growth and climate are the general response pattern of trees from all study sites in NE Tibetan Plateau. Picea crassifolia shows the most instable response to climate factors (mean monthly temperature and total monthly precipitation). Pinus tabulaeformis and Sabina przewalskii just showed instable and divergent responses to their main limiting climate factors but no clear trend was found which is limited by the few sample sites. Corresponding to divergent responses of Picea crassifolia to mean monthly temperature, most radial growth of Picea crassifolia were inhibited by this climate change type drought, only few trees within same sites grew faster due to temperature increasing during recent decades. The divergence response mainly started in last 30 years in six of eleven sample sites over the Northeastern Tibetan Plateau. North-westerly drier sites showed a large percentage of trees per site with a negative correlation to temperature and mostly southerly moister sites showed more mixed responses with both negatively and positively responding trees within site. Concurrent with the regional pattern, low elevation sites show mostly negative correlations with temperature and high elevation sites show more mixed responses. As the hydrothermal conditions of the investigation area changed to a drier and warmer combination, drought stress on tree growth have been intensifying over time and expanding spatially from the middle to most of our study area during the last half century. The Picea crassifolia tree growth climate relationship conducted on an elevational gradient with four different levels from upper treeline to lower treeline at the NE Tibetan Plateau. Results show that upper treeline trees show divergent growth trends and divergent responses in recent decades. Trees from lower treeline show a strengthening drought stress signal over time and no divergent growth trends within sites. This potential ecological reaction of tree populations to changing environmental conditions shows an implications for using trees to reconstruct climate, since the indiscriminate use of tree ring data from sites showing opposite responses to increasing warming could cause mis-calibration of tree ring based climate reconstructions, and over- or underestimation of carbon sequestration potential in biogeochemical models. The physiological response of Sabina przewalskii tree growth to major limiting climate factors based on the Vaganov-Shashkin (VS) model indicated that precipitation during the early growing season, especially in May and June, has significant effect on tree growth, while temperature mainly affects tree growth by warming-induced drought and by extending the growing season in the NE Tibetan Plateau. Under current and projected climate scenarios, modeling results predict an increase in radial growth of Sabina przewalskii around the Qaidam Basin, with the potential outcome that regional forests will increase their capacity to sequester carbon. However, most Picea crassifolia trees growing at lower elevations than Sabina przewalskii might be continue stressed by the warming induced drought and might decrease radial growth in future.
Charakterisierung plasmamembrangebundener Proteasen von Nicotiana tabacum und Hordeum vulgare
(2012)
Es wurden erstmals zwei plasmamembrangebundene Proteaseformen in den Wurzeln der Gerste massenspektrometrisch identifiziert und den Metalloaminopeptidasen der Peptidasefamilien M17 und M24 zugeordnet. Ausgehend von Enzymaktivitätstests mit verschiedenen Substraten und gelelektrophoretischer Fraktionierungen existieren darüber hinaus weitere PM-Proteasen des Aminopeptidase-, Carboxypeptidase- und Endoproteasetyps an der pflanzlichen Plasmamembran (PM). Die untersuchten PM-Proteasen stellen Triton X-114-resistente Proteine dar, die erfolgreich mit Octylglucosid solubilisiert wurden und sowohl an der inneren als auch an der apoplastischen Seite der PM lokalisiert sein könnten. Durch endogene Proteolyse werden andere PM-Proteine wie Aquaporine und P-Typ-H+-ATPasen durch die PM-Proteasen reguliert. Dabei zeigen einige dieser Proteolyseprodukte Proteaseaktivität, die für vier Proteaseformen der Gerste erst nach der Abtrennung von der PM nachweisbar war.
Abstract
In the 21st century, most of the world’s glaciers are expected to retreat due to further global warming. The range of this predicted retreat varies widely as a result of uncertainties in climate and glacier models. To calibrate and validate glacier models, past records of glacier mass balance are necessary, which often only span several decades. Long-term reconstructions of glacier mass balance could increase the precision of glacier models by providing the required calibration data. Here we show the possibility of applying shrub growth increments as an on-site proxy for glacier summer mass balance, exemplified by Salix shrubs in Finse, Norway. We further discuss the challenges which this method needs to meet and address the high potential of shrub growth increments for reconstructing glacier summer mass balance in remote areas.
The pollen record is a powerful proxy to reconstruct past terrestrial vegetation, but quantifying plant abundances is strongly limited because plants produce pollen in different amounts and pollen is dispersed differently. Further complications arise from the use of percentage data. Finally, a pollen grain deposited at a site may have arrived from proximate or distant sources, which implies that a single pollen sample may reflect very different vegetation scenarios. Present thesis suggests improving quantitative reconstructions of past vegetation by refined calibration of the pollen-vegetation relationship (paper I) and application of the downscaling approach (papers II-IV). Paper I primarily addresses the questions of pollen production and dispersal by calibrating the pollen-vegetation relationship. Data analysis employs the common extended R-value (ERV) approach and a new data-model comparison method, which appears more suitable than the ERV approach. For the first time PPEs have been calculated using three contrasting pollen dispersal options, including a Lagrangian stochastic (LS) model. The study proves that the underlying pollen dispersal model is a crucial parameter in PPE calculations and that the calculations with the LS model produce more reliable and realistic PPEs. Papers II to IV address quantitative reconstructions of past vegetation. Using the newly developed downscaling approach, the three studies explore fine scaled vegetation patterns in NE Germany during the Late Glacial and early Holocene. The main assumption of the downscaling approach is that the present day pattern of abiotic site conditions (e.g. the pattern of soil substrates) existed, at least to a large extend, also during the study periods. The basic principle of the approach is to test, whether pollen deposition in sites across a landscape is correlated to that site pattern. The first application of the approach (paper II) has shown a close correlation between PINUS pollen percentages and the distance weighted abundance of sandy soils and between BETULA pollen percentages and the distance weighted abundance of morainic till during the Allerød period, indicating that pine and birch formed rather separate stands on either substrate type. The cooling of the Younger Dryas induced significant changes in the vegetation of NE Germany. By combining pollen percentage and pollen accumulation rate data paper III identified a sharp vegetation boundary between the Mecklenburg and Brandenburg area at about 53 °N. The downscaling approach, here used with pollen accumulation rate data, suggests that in the North small tree stands could only exist in sheltered positions. The sharp vegetation boundary is possibly related to a climatic gradient and the southern permafrost limit, which itself may result from the formation of sea ice on the North Atlantic north of 53°N during winter. The warming of the Holocene again allowed the expansion of forests in the study area. Paper IV uses high resolution pollen (accumulation rate) data to study the successive forest formation, including the immigration of hazel, and explores vegetation patterns and composition during these successive stages using the extended downscaling approach. This approach addresses the problems related to differential pollen production, dispersal and the use of percentage data by applying simulations. It reveals that initially pine and birch established, as during the Allerød period, in largely separate stands with pine dominating on sandy soils and birch dominating on fine grained soils. Also open rich vegetation persisted, possibly due to seasonal drought, mainly on fine grained soils. Hazel later mainly spread on sites that received additional wetness from ground or surface water; it did not enter pine dominated forests on well drained sandy soils. Overall, the early Holocene vegetation of the study area was sharply differentiated by soil humidity and fertility. To conclude, present thesis has revealed vegetation patterns and species site preferences in NE Germany during three periods of the Lateglacial and early Holocene. The results improve our understanding of vegetation history in northern Central Europe, specifically for periods of rapid climate change. The approaches applied are flexible with respect to the type and quality of pollen data used and may be implemented using standard software packages.
In terms of climate change and climate change mitigation, the quantitative knowledge of global carbon pools is important information. On the one hand, knowledge on the amount of carbon cycling among – and stored in – global pools (i.e. Atmosphere, Biosphere, Cryosphere, Hydrosphere, and Lithosphere) may improve the reliability of models predicting atmospheric CO2 concentrations in terms of fossil fuel combustion. On the other hand, the carbon sequestration potential of specific ecosystems allows for estimating their feasibility regarding carbon trade mechanisms such as the Clean Development Mechanism or the Reducing Emissions from Deforestation and Degradation Program (REDD+). However, up to date, the majority of terrestrial carbon assessments have focused on forests and peatlands, leaving a data gap open regarding the remaining ecosystems. This data gap is likely to be explained by the relatively high carbon densities and/or productivities of forests and peatlands. Nevertheless, to get a precise as possible global picture, information on carbon pools and sequestration of other ecosystems is needed. Although desert ecosystems generally express low carbon densities, they may absolutely store a remarkable amount of carbon due to their large areal extent. In this context, Central Asian Deserts (in particular within the Turanian Deserts, i.e. Karakum, Kysylkum, Muyunkum) likely inhibit comparably high carbon pools as they express a sparse vegetation cover due to an exceptionally high annual precipitation if compared to the World’s deserts. In this dissertation, three important woody plant species – Populus euphratica and Haloxylon aphyllum and Haloxylon persicum – of Central Asian Deserts were investigated for their carbon pools and carbon sequestration potential. These species were chosen as they I) locally express high carbon densities, II) are dominant species, III) have a rather large spatial distribution, and IV) have experienced a strong degradation throughout the 20th century. Thus, they likely show a remarkable potential for carbon re-sequestration through restoration and thus for an application of carbon trade mechanisms (CHAPTER I). P. euphratica was investigated in the nature reserve Kabakly at the Amu Darya, Turkmenistan and in Iminqak at the Tarim He, Xinjiang, China. The assessment of Haloxylon species was restricted to the Turanian deserts west of the Tain Shan. To achieve a first scientific basis for large scale estimates, different methodologies, ranging from allometric formulas, over dendrochronology to remote sensing were combined (CHAPTERS II-V). In CHAPTER II allometric formulas were successfully developed for Haloxylon aphyllum and Haloxylon persicum and applied to six study sites distributed over the Turanian Deserts to represent the allometric variability of Haloxylon species in Central Asia. CHAPTER III derives another allometric formula (only based on canopy area) for H. aphyllum and combines it with a remote sensing analysis from the nature reserve Repetek. Thereby, a first large scale estimate covering the Northeastern Karakum Desert of carbon pools related to mono specific H. aphyllum stands is achieved. CHAPTER IV describes the wood structure of Populus euphratica forests in the nature reserve Kabakly (Turkmenistan) and in Iminqak (Xinjiang, China). In CHAPTER V a dendrochronological approach derives models for predicting the Net Primary Productivity (NPP) and the age of P. euphratica in the nature reserve Kabakly. Thereby, a first feasibility assessment regarding remote sensing analyses and the upscaling of the obtained NPP results is carried out. First estimates based on these local studies (CHAPTER VI), reveal carbon densities ranging from 0.1 – 26.3 t C ha 1 for the three investigated species. Highest maximum and median carbon densities were found for P. euphratica, but Haloxylon aphyllum expressed remarkable maximum carbon densities (13.1 t C ha-1), too. The total carbon pools were estimated at 6480 kt C for P. euphratica, 520 kt C for H. aphyllum stands and 6900 kt C for Haloxylon persicum shrubland. Accounting for the extent of degraded areas, the total re-sequestration potentials of the respective species were estimated at 4320 kt C, 1620 kt C and 21900 kt C, this highlighting the remarkable absolute re-sequestration potential of H. persicum shrubland despite its low average carbon densities. In the end, the main results were put into a broader context (CHAPTER VI), discussing the general feasibility of reforestations both in ecological terms as well as in terms of carbon trade mechanisms. A short example highlights the strong connection between the feasibility of reforestations and the global carbon market. Finally, open research questions are brought forth revealing the yet large research potential of Central Asian Desert ecosystems in general and in terms of carbon sequestration.
Abstract: The Arctic has experienced a pronounced increase in air temperature over the last four decades, with an average increase of 0.4 °C per decade and thus an increase of almost the double rate than that of temperate regions. Remote sensing studies and repeat photography of historical images have shown large-scale increases of plant productivity in tundra ecosystems over the same time period. A pronounced size, abundance and biomass increase of shrubs has been observed. This so called shrub expansion has important repercussions for the vegetation, the animals, the soil, the energy and the carbon balance of the Arctic tundra and on regional and global climate. As the comparison of historical photographs with recent photographs has shown, this shrub expansion occurs on different temporal and spatial scales with areas of strong increase in shrub cover (expanding patches) and areas without noticeable changes in shrub vegetation (stable patches). While remote sensing approaches for the detection of changes in vegetation are limited in their temporal coverage and so far also in their resolution, historical photographs with high resolution are often not available. Experimental studies have shown that an increase in nutrients or temperature often resulted in increased shrub biomass, but findings were partly contradictory, referred to short term observations and usually confined to small areas. To bridge the gap between spatially limited plot-scale experiments and global large-scale assessment of plant productivity by satellite derived pictures, dendrochronology was used in this thesis to analyze the drivers for and the rate of shrub growth of different widespread evergreen and deciduous shrub species in alpine and arctic tundra and to reconstruct historic environmental conditions. In detail, this doctoral thesis was conducted to study shrub growth and to assess the applicability of traditional dendrochronological methods on shrubs that had been so far mainly applied to trees and to test whether shrubs differed morphologically from trees. Further, I was determined to look for evidence for a possible Scandinavian shrub range expansion and to assess which climatic factors – temperature, precipitation or snow – influenced shrub growth significantly. Moreover, we aimed to find the reason for the observed heterogeneity of the shrub expansion on the landscape and its relevance for the three most common shrubs on the Alaskan tundra. The methods applied followed the routines usually applied for dendrochronological analyses of treerings, with the exception that usually several stem discs of the main stem were analyzed and frequently had to be prepared with help of a microtome as thin-sections, that were stained and sealed on a coverglass before annual shrubrings were measured. The averaged shrubring widths were then compared with environmental factors through correlation and regression methods. This thesis gives first a general introduction to climate change in the Arctic, shrub expansion on the tundra, the scientific discipline of dendrochronology or -ecology on shrubs and its development, the main research questions and the thesis outline. Then seven research papers are presented and the main results and conclusions are synthesized and discussed and finally possible venues of future research are outlined. The most important insights gained from this thesis are the following: I) Dendroecological methods can be applied to shrubs. Insights into shrub morphology have been gained by detecting an interesting mechanism for coping with adverse environmental conditions of both, trees and shrubs that can save resources by confining the production of wood to the upper parts of the stem. II) Further, I found evidence for a shrub expansion in Scandinavia. III) I could establish the causal link between the current climate warming and increased radial and vertical shrub growth by identifying summer temperature as main driver for shrub growth. IV) Results from the Alaskan tundra indicate a strongly adverse role of snow for shrub growth in stable patches, refuting the popular snow-shrub-microbe hypothesis for this extensive area across species. The differing influence of snow is likely linked to the presence of permafrost and shallow active layers and the snow’s contribution to moist or even anoxic conditions in Alaska. V) Furthermore, we found that the different rates and the spatial heterogeneity of shrub expansion are accompanied by strong differences in the surrounding vegetation composition and the soil parameters of expanding (accustomed to more favorable conditions) and stable shrub patches. VI) These differences are predisposed by shrub patch position within the landscape, comprising different levels and rates of disturbance. VII) Additionally, shrub ring records were successfully used as natural archives to model past temperature dynamics respectively summer glacier mass balance with high accuracy. VIII) Finally, a synthesis of the climate-growth relationships of shrubs of more than 25 sites around the Arctic as joined effort together with other leading shrub researchers supports the presence of a circumpolar shrub expansion, gives recommendations for methods used in shrub dendroecology and lays out future research directions. The findings of my dissertation research show that the analysis of shrubs by dendroecological methods yields highly interesting results, and they greatly improved our understanding of factors that influence individual shrub growth, the reconstruction of earlier environmental conditions as well as the reconstruction and assessment of plant population dynamics.
Many ethicists consider the rule of nonmaleficence – Do no harm! – to be the most fundamental ethical rule and key to ethics. This rule is taken as the foundation of the present work. I argue that any entity, that can be harmed, ought to be morally considered. Only those entities can be harmed that are inherently goal-directed or striving – in other words, that possess a telos. The reason is that by constantly acting in ways to preserve their being and to prevent their own not-being, goal-directed entities express that they value their own good. To harm such a goal-directed entity therefore means to act against the values and the good of it. The argument so far supports ethical biocentrism, that is, the view that all living, goal-directed beings are harmable, possess interests, and are, thus, morally considerable, while non-living beings are not. Yet, I digress from classical biocentrism since I conclude, based on analysis of evolutionary and biological findings, that the locus of goal-directedness and potential harm is also, if not foremost, situated in genes. Within many species, individual organisms sacrifice themselves for the betterment of their descendants like in praying mantises where males sacrifice themselves and are eaten by the female during copulation. This shows that it is not necessarily the organism as an individual which follows its own interests and goals. Individual organisms are – to a high degree – “directed” by their genes. Even in highly developed animals, genes play a significant role in the goal-directedness of the individuals. An adult human organism, for example, consists of trillions of individual cells. However, all these cells are derived from a single cell – the fertilized egg. Each of our lives begins with a single cell that contains almost all information to finally form our functioning body. Where do all the instructions, the goal-directedness come from to finally form an adult organism if not from the genes contained in this first cell, the zygote? It is the genes of each zygote that contain a set of information for making the appropriate adult. Organisms are largely programmed to do everything necessary to stay in existence, to survive, and finally to pass on their genes successfully – either by reproducing or by helping close relatives that carry a similar set of genes. The main interests of genes lie in their continued existence. This necessitates reproduction since the gene-carrying organisms will inevitably die. Single genes, though, are difficult to morally consider directly since they perform entirely in and through individual organisms. Without the individual organisms, genes cannot survive. The good news for ethics is that the interests of genes and organism usually converge: individual organisms try to survive – as do their genes. In practice, it thus makes much more sense to give moral attention to entire organisms instead of single genes. An advantage of the gene-centric ethical theory proposed here is that the moral relevance of future generations and species can be “directly” justified: Since genes have an interest in their continued existence (in the form of identical copies), they would be harmed if future generations were doomed to inexistence. Within a species with many individuals, each gene is likely to be represented in many organisms. The smaller the gene pool of a species gets, the less likely is the existence of the same gene and, therefore, the less likely is the fulfillment of its fundamental interests. Hence, saving one of the last individuals of an endangered species would be ethically preferable to saving an individual of a populous species. Unfortunately, moral conflicts are abundant – not only concerning biodiversity conservation. We often have to choose between harming either entity A or entity B – for example in the daily questions of food and eating. In such cases, a strictly egalitarian theory (especially an egalitarian biocentric one) would be no real help and without any guiding power. Therefore, on a second level of morality, we have to include additional criteria that help to minimize the overall harm. For these criteria to be objective, universalizable, and thus moral ones, I apply a number of widely accepted ethical principles like the principle of proportionality, impartiality, self-defense, and universalizability. By recurring to these principles, I identify a set of morally relevant criteria for a fair resolution of moral conflict situations which help to minimize the overall harm done. The identified criteria are: (phylogenetic) nearness, endangerment, r- or K-selected species, evolutionary distinctiveness, ability to regrow and to regenerate, pain-susceptibility, and ecosystematic role. In sum, my gene-centric environmental ethical theory provides numerous reasons and arguments for biodiversity conservation – for protecting genes, organisms, species, and ecosystems alike – without neglecting the needs of humans.
The globally threatened Aquatic Warbler (Acrocephalus paludicola) is the rarest migratory songbird in Europe. Before the population declined dramatically after 1960, the Aquatic Warbler was a common species in European mires and river flood¬plains. Today, the global population is estimated to count 27 600 individuals, of which approx. 90 % are concentrated in only three countries during the breeding season: Belarus, Poland and Ukraine. Despite numerous conservation efforts mainly under¬taken in European countries, the population decline has not been stopped. Although the Aquatic Warbler is considered a “European” bird species because of the location of its breeding grounds, it spends up to six months on migration and on the wintering grounds on the African continent. A comprehensive species conservation strategy must therefore include the preservation of African resting and wintering grounds. This study analyses the ecol¬ogy of Aquatic Warbler in its wintering grounds using the example of the Djoudj National Park area in north-western Senegal. The study aims, first, to close knowledge gaps regarding the behaviour and the habitat requirements of Aquatic Warblers during their stay on the wintering grounds to provide a scientific base for long-term species conservation management; second, to assess the importance of the wintering site in the Djoudj area is in a global perspec¬tive; and third, to identify threats to the Djoudj area as a suitable Aquatic Warbler habitat. In a fourth step, science-based management recommendations are formu¬lated to support the ongoing practical conservation work of the Djoudj National Park administration with regard to the Aquatic Warbler. The main outcomes of the study are the following: (I) We confirmed the presence of Aquatic Warblers in the Djoudj area between mid-December and the end of March. (II) The connection between the wintering ground “Djoudj National Park area” and the breeding ground “Biebrza valley” (eastern Poland) was confirmed by the resighting of a ringed Aquatic Warbler individual. (III) The remiges moult of the species was observed under natural conditions for the first time. We confirmed that the Aquatic Warbler undergoes a complete moult on its wintering grounds, following the typical sequence of passerine moult. (IV) Aquatic Warblers occur in shallowly inundated vegetation with dominant stands of Oryza longistaminata, Eleocharis mutata, Scirpus maritimus, Scirpus litto¬ralis and Sporobulus robustus interspersed with small (1–2 m²) areas of open water. The afore mentioned herbaceous species form a homogenous wetland vegetation of approximately 0.6–1.5 m height, with a coverage of 80 % to 100 %. Wild rice (Oryza longistaminata) may provide the most suitable habitat conditions as suggested by the very high density of Aquatic Warblers at sites dominated by this species. Preferential habitat may include a few solitary trees, but open woodland or scrublands are unsuit-able for Aquatic Warbler. Pure stands of cattail (Typha australis) are avoided. The water level in the habitat areas varies between 0 (humid soil) and 40 cm above the ground. Constant inundation seems to be essential, as Aquatic Warblers were never encountered in dry parts of the study area. All known Aquatic Warbler habitats in the study area are influenced by brackish or salty water. (V) During winter Aquatic Warblers use a home range of 3.9 ha (± 1.9) in aver¬age, which is shared with other individuals and species. No territorial behaviour was observed in the winter quarters. (VI) The vegetation and land cover map prepared distinguishes six classes of her¬baceous vegetation and five general land cover classes. (VII) There are 4 729 ha of potential Aquatic Warbler habitat within the study area. (VIII) We estimate the density of the Aquatic Warbler population in the study area to range between 0 and 2.26 individuals per hectare with a total population size of 776 individuals, or 260–4 057 individuals in a 95 % credibility interval. Hence we conclude that 1.1–3.8 % (0.37–19.8 % within the 95 % credibility interval) of the global Aquatic Warbler wintering population are found in the Djoudj area. (VIII) The Aquatic Warbler habitats in the Djoudj area are affected by the inun¬dation regime, water circulation, changes in salinity, grazing, the spread of cattail (Typha australis), the encrustation of vegetation, the protection status of passerine migrator habitats and the expansion of rice cultivation a. Our management proposals for the preservation of existing and the development of new Aquatic Warbler habitats were formulated and incorporated into the Management Plan of the Djoudj National Park 2014–2018.
Late Quaternary evolution and carbon cycling of tropical peatlands in equatorial Southeast Asia
(2014)
Peatlands are an important component in the global carbon cycle as they act as both long-term sinks for carbon dioxide and significant sources for methane. Over the Holocene period (the past 11,700 years) continuous CO2 uptake by peat accumulation exceeded methane emissions in northern peatlands and resulted in a net-radiative cooling effect on the global climate.Although 11% of the global peatland area is located in the tropics, the role of tropical peatlands in the global carbon cycle and in influencing the Earth’s radiative budget has not been resolved. Climate-carbon cycle models have thus far not included tropical peatlands because reliable data on their past rates of carbon uptake and release are not available. In this thesis this problem has been approached by reconstructing peatland expansion and rates of carbon storage and release over the Late Quaternary (Latest Pleistocene and Holocene) for the largest tropical peatland area, which is located in equatorial SoutheastAsia (i.e. Sumatra, Borneo, Peninsular Malaysia). Peat accumulation in the tropics remains an enigmatic phenomenon, because the constantly high temperatures of 26-27°C should theoretically drive rapid soil carbon turnover and thus not enable the accumulation of peat. Therefore this thesis also explores the mechanisms that cause peat formation in the SoutheastAsian tropics as well as the drivers behind changing rates of carbon accumulation. Carbon dynamics were analyzed at the regional scale (103–105 km2) of SoutheastAsia over millennial timescales (paper, I, II) and at the local scale (101–102 m2) of a peatland site on annual to centennial timescales (paper III, IV). Paper I presents the first systematic classification of the nearly 160,000 km2 SoutheastAsian lowland peatlands (below 70 m a.s.l.) into geographic peatland types. The peatlands were divided into 1) coastal peatlands of PeninsularMalaysia, Sumatra, and Borneo (~130,000 km2) and into inland peatlands (~30,000 km2) of 2) Central Kalimantan (southern Borneo), 3) the Kutai basin (eastern Borneo), and 4) the Upper Kapuas basin (western Borneo). Coastal peatlands formed by primary mire formation directly on freshly exposed marine or mangrove soils with the lowering of the sea level during the Late Holocene. In contrast, inland peatlands formed via paludification on either terrestrial sand soils (Central Kalimantan) or by both paludification and terrestrialization (Kutai basin, Upper Kapuas basin). The sequence of peatland initiation was established by applying the common cumulative basal date frequency approach (paper I). This method revealed clear differences in the timing of peatland initiation: 1) the Upper Kapuas peatlands are the oldest postglacial peat formations and date from 20,000-13,000 cal BP (calendar years before present), 2) inland Central Kalimantan peatlands date from 14,500-9000 cal BP, 3) the Kutai peatlands date from 8300-4900 cal BP, and 4) and the coastal peatlands date from 7700-200 cal BP. Coastal peatlands have a Holocene average carbon accumulation rate of 77 g C m-2 yr-1, being recognized as the globally most effective terrestrial ecosystems in terms of long-term carbon sequestration. Except for the Kutai peatlands, the Holocene average carbon accumulation rates of inland peatlands are significantly lower (20-30 g C m-2 yr-1) and very similar to the average long-term rates of northern peatlands. Fluctuations in past rates of carbon accumulation of SoutheastAsian peatlands could for the first time be linked to paleoclimatic changes, primarily variations in moisture availability (paper I, II). Hydroclimatic influences on carbon accumulation rates were related to shifts in the mean position of the Intertropical Convergence Zone, changes in the intensity of theAustral-Asian monsoon system, and variations in the frequency of the El Niño- Southern Oscillation. In contrast, peatland initiation and expansion was driven by sea-level change (paper I, II). The deglacial rise in sea-level is identified as the primary driver for inland peatland formation in Borneo, because the rising sea-level 1) lowered the hydrological gradients in the SoutheastAsian island archipelago inducing rising ground and surface water levels on these islands, and 2) led to higher atmospheric moisture availability due to the associated expansion of marine water masses on the shelf floor. Paper II shows that inland peatland initiation and expansion was most extensive during deglacial meltwater pulses, when the rate of sea-level rise exceeded 10 mm yr-1. Only when the rate of sea-level rise had slowed down to a threshold of 2.4 mm yr-1 by ~7000 cal BP could peat accumulation along the coasts keep up with the sea-level rise and coastal peatlands could form. Hydro-isostatic adjustment of the Sunda Shelf led to a sea-level lowering by ca. 5 m over the past 4500 years. Falling sea levels exposed extensive marine areas that were rapidly colonized by peat swamp forests.Anewly 140 developed method for the reconstruction of past peatland area based on transfer functions (paper II) reveals that 70%of the peatlands of Sumatra and Kalimantan only formed during the past 4000 years.Moreover, this new transfer function approach shows that the common basal dates approach overestimated the extent of peatlands in the past. This method, in general, leads to higher rates of reconstructed cumulative peat carbon uptake for the past. By combining reconstructed peatland areas and mean rates of carbon accumulation over millennial timescales from each peatland type the carbon uptake of all peatlands from Sumatra and Kalimantan could be quantified for the past 15,000 years (paper II). Carbon uptake remained below 1 Teragram (Tg) C yr-1 from 15,000-5000 cal BP because the total area of peatlands was less than 30,000 km2. Rapid peatland expansion driven by the lowering of sea-level over the past 5000 years increased carbon uptake on Sumatra and Kalimantan to over 7 Tg C yr-1 and resulted in an exponential growth of the regional peat-carbon reservoir to a size of over 20 Pg C. SoutheastAsian peatlands therefore had no significant role in the Late Pleistocene and Early Holocene global carbon cycle. However, because of their rapid expansion after 5000 cal BP by over 100,000 km2 the peatlands of SoutheastAsia became a globally important carbon sink during the Late Holocene and likely caused an atmospheric CO2 drawdown of 1-2 ppm (paper II). This previously unrecognized biospheric carbon sink partly compensated for contemporaneous terrestrial carbon losses associated with the desertification of Northern Africa. The mechanisms that enable high rates of carbon accumulation of coastal peatlands were explored in a peat core study presented in paper III. Here the use of a new coring technique for the tropics and the application of noninvasive geophysical measurements were employed to derive a high-resolution record of carbon accumulation rates. This study provides the first description of peatland pools for SoutheastAsia, which form as tip-up pools from falling trees such as Shorea albida. Based on a pollen and macrofossil record a fossil tip-up pool could be identified in the core and an associated carbon accumulation rate of 100 to over 900 g C m-2 yr-1 determined. Thus tip-up pools function as local hot spots for carbon accumulation, fundamentally different from northern hemisphere peatland pools, which act as net-carbon sources. From a time-series of aerial photographs the rate of tree fall and thus pool formation was determined at 0.4 tree ha-1 yr-1 (paper III).Asimulation model indicates that up to 60%of the peat deposited in peat domes of Borneo is derived from filled up fossil pools – changing the paradigm that Southeast Asian peatlands mainly form from belowground biomass and providing an explanation for the rapid carbon accumulation of these ecosystems. The climate impact of peatlands is, however, not only related to their capacity to rapidly store carbon, because peatlands also release the strong greenhouse gas methane – a by-product of anaerobic decomposition.Ametaanalysis of methane emission data from SoutheastAsian peatlands (paper IV) shows that their average annual methane release of 3 g CH4 m-2 yr-1 is lower than the average annual release of ~9 g CH4 m-2 yr-1 from northern peatlands, although the higher tropical soil temperatures should lead to significantly higher emissions. The limited degree of anaerobic decay is explained by the recalcitrance of the deposited biomass, which contains high amounts of lignin and tannin, providing another explanation for rapid carbon accumulation. Low anaerobic decomposition together with high rates of carbon accumulation imply that limits to vertical peat bog growth in SoutheastAsia are not set by cumulative anaerobic decay as in northern raised bogs. Instead peat bog growth is limited by aerobic decomposition related to water-table lowering as shown by a derived linear relationship between the amount of released CO2 from aerobic peat decomposition and the mean annual depth of the peatland water-table (paper IV). The climatic effect of Southeast Asian peatlands was determined by the global warming potential (GWP) method, which compares carbon uptake with methane emissions in terms of CO2-equivalents. The low methane emissions and high carbon accumulation rates of coastal peatlands result in a net annual uptake of 1340 kg CO2- equiv. ha-1 yr-1 over a 100 year GWP time-horizon. Under natural conditions coastal Southeast peatlands exert a significant net cooling effect on the global climate in contrast to northern peatlands, which have a warming effect or act climatic neutral on this time frame. It can be concluded that the tropical peatlands of SoutheastAsia are the strongest carbon sinks among all peatlands globally with a notable influence on the Earth’s radiative budget. However, today an estimated 90,000 km2 of peatlands in SoutheastAsia is drained for agriculture (e.g. oil palm plantations) and deforestation. These drained peatlands release annually over 140 Tg C yr-1 from aerobic peat 141 decomposition. Drainage also facilitates the regular spread of peat fires in this region, which on average release around 75 Tg C yr-1. Ongoing total carbon losses (~220 Tg C yr-1) exceed the natural carbon uptake by a factor of 25 and demonstrate that the entire SoutheastAsian peatland region has recently switched from a globally important carbon sink to a globally significant source of atmospheric CO2 (paper II, IV).
Against the background of post-socialist transition and nationwide economic growth in Azerbaijan this dissertation analyses the utilisation of rangeland resources by mobile pastoralists in Azerbaijan. The study was motivated by the initially scarce knowledge about pastoralism in Azerbaijan and concerns about declining pasture condition due to growing livestock numbers. The study was guided by three research objectives, which were addressed cumulatively in five publications. The first objective aims at analysing the development of pastoralism in the transition period in comparison to developments in the pastoral sectors of other post-socialist countries. Secondly, the study addresses socio-economic causes of inappropriate pasture management by pastoralists. Finally, in an application-oriented research process recommendations for improving the management of pastoral farms and pasture governance were developed in order to mitigate inappropriate pasture management. For addressing these objectives the study frames the management of rangelands as a complex natural resource management system, in which the environment, users, governance structures, and the socio-political context are closely linked. Within this framework, the study focused especially on pastoral farms using a farm economics approach and on pasture governance with employing institutional economic theories. Regarding the methodology, a case study approach in four study regions was chosen in order to deal with the ex-ante limited information about Azerbaijani pastoralism and the explanatory aim of research.
Da Feuchtgebiete nicht wie reguläres Ackerland genutzt werde können, werden sie oft als Ödland betrachtet und daher für Ackerbau trockengelegt. Diese sehr einseitige Perspektive auf Feuchtgebiete übersieht die vielfältigen Ökosystemleistungen, die es Menschen und Natur zur Verfügung stellt. Einige dieser Leistungen sind das Speichern und die Reinigung von Abwasser, die Bereitstellung von Lebensmitteln und Rohmaterialien, die lokale Klimaregulierung und die Nutzung als Habitat. Viele dieser Leistungen werden von der Natur „umsonst“ bereitgestellt und haben keinen monetären Wert auf traditionellen Märkten. In China bedecken Feuchtgebiete 8% der Gesamtfläche, sind aber in einer bedrohlichen Situation, auch wenn in den letzten Jahren einige Teile erfolgreich restauriert werden konnten. In den vergangenen 50 Jahren gingen mehr als 20% der Feuchtgebiete durch Verschmutzung, Wasserableitung und -aufstauung, Nutzbarmachung, Trockenlegung und Übernutzung der Resourcen verloren. Die Wasserressourcen und Feuchtgebiete – besonders in Nord- und Nord-Ost-China sind bedroht, da sie in ariden oder semi-ariden Regionen liegen. Feuchtgebiete stellen gleichwohl wichtige Ökosystemdienstleistungen für die genannte Region zur Verfügung und tragen signifikant und in vielfältiger Weise zu lokalem Lebensunterhalt bei, z. B. durch Nahrungs- und Rohstoffbereitstellung. Ziel dieser Arbeit war es, zu einer ökonomisch-ökologischen Bewertung des Gemeinen Schilfs (Phragmites australis) am Wuliangsuhai See zu kommen, in dem Schilf in großen Mengen vorkommt und lokal relevant ist. Schilf wurde an einem Fallbeispiel in der Inneren Mongolei, China, untersucht, ein Teil des Forschungsprojektes “Sustainable Water Management and Wetland Restoration in Settlement of Arid Central Asia” war, welches in der Inneren Mongolei, China, durchgeführt wurde. Meine Arbeit beeinhaltete vielfältige Apsekte: Zuerst wurde eine detaillierte Literaturanalyse durchgeführt, um die kommerzielle Nutzung von Schilf weltweit zu untersuchen. Es konnten vielfältige Verwertungen ausgemacht werden, viele lokal und nur in kleinem Maßstab (z. B. Nahrung), einige andere innovativ und/oder noch im Experimentierstadium (z. B. Ethanol). Im Bezug auf den Wuliangsuhai See kann geschlussfolgert werden, dass nur große, “einfache” Lösungen in Frage kommen. Besonders der Einsatz als Rohstoff zur Verfeuerung und als Baumaterial scheint erfolgversprechend. Daran anschließend wurde die Biomasseproduktivität am Wuliangsuhai See mit Hilfe zweier Feldkampagnen erhoben und dann auf den gesamten See projiziert. Diese Daten waren entscheidend, da sie Basis waren, um die totale verfügbare Biomasse sowie auch den Einfluss der Schilfernte auf das Nährstoff-Budget abzuschätzen, da ein erheblicher Anteil an Nährstoffen jährlich durch die Ernte dem See entzogen wird. Nach der Bestimmung der verfügbaren Schilfressourcen wurde deren Verwendung durch qualitative Interviews untersucht und mit dem „Netchain Approach“ dargestellt. Die verschiedenen Interessengruppen, die in das Schilfgeschäft involviert sind, sowie deren Einkommen wurden skizziert. Es wurde deutlich, dass die Verwertung zur Papierproduktionen aus einer Vielzahl von Gründen kaum profitabel ist. Basierend auf dieser Erkenntnis wurden vier verschiedene Szenarien für eine innovative Schilfenergienutzung am Wuliangsuhai See analysiert und bewertet. Die Schilfenergienutzung ist unter bestimmten Voraussetzungen profitabel, aber nur schwer wettbewerbsfähig gegenüber günstiger und lokal verfügbarer Kohle. Abschließend wurde der Wuliangsuhai See in einen umfassenderen Ausblick eingeordnet, welche auch das Bewässerungssystem stromaufwärts miteinschloss. Vier Szenarien beleuchteten, wie heutige Entscheidungen die Zukunft des Sees beeinflussen. Diese Arbeit präsentiert die folgenden Haupteinsichten und Empfehlungen für das Management des Wuliangsuhai Sees: 1. Ein übergreifendes Konzept für den Wuliangsuhai See ist nötig, welches auch das gesamte Hetao Bewässerungsgebiet miteinbezieht. 2. Der See ist in dieser sehr trockenen Gegend einzigartig und sollte nicht nur für die Bereitstellung von Marktgütern, sondern auch für „Nicht-Markt-Leistungen“, wie die Abwasserreinigung, beachtet werden. 3. Die Restorationsleistung der Schilfernte konnte in dieser Publikation gezeigt werden und sollte bei zukünftigen Managemententscheidungen berücksichtigt werden. 4. Die lokale Schilfökonomie wird von verschiedenen Seiten herausgefordert. Dennoch scheint auch die lokale Schilfenergienutzung kaum profitabel. 5. Aufgrund der hohen Relevanz der Schilfökonomie für die lokale Ökonomie und Ökologie sollte die Regierung die Seeverwaltung unterstützen. Zusammenfassend konnten die vielfältigen sozialen, ökologischen und ökonomischen Werte von Schilf am Wuliangsuhai See aufgezeigt werden. Da nur geringe Informationen vorhanden waren, stellt dies den ersten umfassenden Überblick dar und soll Entscheidungsträgern ermöglichen, auf diesen Informationen basierend Entscheidungen für die Zukunft des Sees zu treffen.
Global change, amongst others characterized by increasing temperatures, altered precipitation patterns, an increase of extreme climatic events and continued atmospheric depositions of pollutants, is expected to severely impact forest ecosystems worldwide. The complex interplay between different factors acting upon tree growth, combined with regional patterns in climatic change calls for a region specific evaluation of the possible consequences on forest ecosystems. For northeastern Germany regional climate models identify a rise in temperatures and a change in precipitation patterns. Drier summers and wetter winters together with an increase in extreme weather events are seen as the most pronounced changes that will occur during the 21st century. In this thesis I analysed past growth rates and climate-growth relationships in different stands of beech (Fagus sylvatica L.) and oak (Quercus robur L.) along a gradient of decreasing precipitation in a space for time approach. Special attention was paid to the influence of summer drought, soil waterlogging and the importance of site conditions in modulating the reactions to these climatic stressors. Departing from these retrospective analyses, future growth trends are modelled for beech, oak and Scots pine (Pinus sylvestris L.), based on projections of a regional climate model until the year 2100. Furthermore, I studied the influence of sudden and extreme shifts in hydrological conditions on the growth of oaks in a drained peatland that was subject to catastrophic rewetting. All analyses of this thesis are based on ring-width and wood anatomical features applying a variety of dendrochronological methods. The gradient approach revealed similar climate-growth relationships for beech and oak on drought exposed, sandy sites, where water availability during early summer was the main growth-limiting factor for both species. Decreasing precipitation rates towards the East are associated with higher drought susceptibility, especially for beech. As a result, competitive superiority of beech over oak decreases. In a drier future the competitive balance between the two species may shift (rank reversal). During the past decades beech has shown larger interannual growth variability and a higher number of growth depressions. These changes might indicate that increasing temperatures and climatic variability are already affecting its growth patterns and climate sensitivity. This is in line with the prospective modelling approach. According to our models, growth trends will turn negative for beech and oak towards the end of the 21st century, with beech showing the highest growth reduction (23% compared to the reference period 1971-2000). For pine, modelled growth rates show only minor changes. Whereas beech and oak shared a high common signal on the dry sites, the two species differed in high frequency ring patterns on the wet sites. On poorly drained, loamy soils beech, with its superficial root system, suffered from summer droughts. In contrast, on these sites ring-width of pedunculate oak was not correlated to summer moisture conditions resulting in differing interannual ring patterns between dry and wet sites. Wet periods with high soil water saturation did not have a negative influence on the growth of either species. Such a lack of response is not surprising for oak, which is generally known as rather tolerant to soil waterlogging, but it indicates an unexpectedly high tolerance of beech to stagnating wetness. Using the natural laboratory of an oak forest that suffered a catastrophic flooding I could show that slower grown trees that had likely been suppressed displayed a higher adaptive capacity compared with bigger, dominant trees. Many of the previously dominant individuals died within 18 years after the event. Trees that survived the groundwater rise displayed a typical ring pattern: growth was suppressed for a few years, but afterwards recovered and even surpassed previous growth rates, most likely as a result of competition release. The sudden hydrological change left a clear imprint in ring patterns and wood anatomical features in both the dying and the surviving trees. This differentiated imprint may be helpful for a better interpretation of growth patterns found in subfossil bog oaks, an important climate proxy of the Holocene. The insights gained from this thesis support existing concerns about drought induced growth decline for oak, but especially for beech. Changes in precipitation patterns might lead to wetter conditions during winter, but these will likely have only little effect on growth. Both s show rather high resilience to stagnating wetness. More likely, it are extreme events like prolonged droughts or heavy rainfalls that might breach thresholds in the ability of the two species to cope with too much or too little water. Such extreme events thus pose a strong risk to the future growth performance of both oak and beech.
Myxomycetes are fungus-like protists of the supergroup Amoebozoa found to be abundant in all terrestrial ecosystems. Mainly based on its macroscopically visible fruit bodies, our knowledge on ecology and diversity of myxomycetes is better than for most other protistean groups, but there is still a lacking knowledge about global diversity patterns since tropical regions, especially the old world tropics, are still understudied. In this thesis a combination of classical ecological analyses and modern molecular methods were used to expand the current knowledge on myxomycete diversity and biogeography in the Paleotropics. A number of surveys in the Philippine archipelago are conducted to provide and to add information about the distribution of myxomycetes in the Southeast Asian region. A combination of field collecting and ca. 2500 moist chamber cultures from four unexplored areas in the Philippines, namely, the Bicol Peninsula (746 records, 57 taxa), Puerto Galera (926 records, 42 taxa), Quezon National Park (205 records, 35 taxa), and Negros Province (193 records, 28 taxa), now brings the number of species recorded for Philippines to 150; with one record, Stemonaria fuscoides, noted as new for the Asian Paleotropics. Collecting localities that have more diverse plant communities showed as well higher species diversity of myxomycetes. In congruence with studies from the Neotropical forests, it seems also that anthropogenic disturbances and the type of forest structure affect the occurrence of myxomycetes for the Philippines. Another survey carried out in another paleotropical region, the highlands of Ethiopia, revealed a total of 151 records, with all 39 species found as new for the country. Three records of Diderma cf. miniatum with a strong bright red peridium and one record of Didymium cf. flexuosum with a conspicuous broad reticulation in the spore ornamentation were described and barcoded, since both may represent morphospecies new to science. A number of rarely recorded species, like Didymium saturnus, Metatrichia floripara, Perichaena areolata, and Physarina echinospora showed that resembling to its unique flora, the east African mountain ranges harbor a diverse and distinctive myxomycete assemblage. One incentive of this study was to compile a solid large dataset for the Paleotropical region that is comparable to data obtained from comprehensive studies performed in the Neotropical areas a decade ago. A total of eight surveys (with four comprehensive regional surveys, two from lowland and two from highland, for each region, the Neo- and the Paleotropics) were used, to compare the myxomycete assemblages of both regions. Each survey comes from a region with fairly homogenous vegetation, and includes specimens from both field and moist chamber cultures component. A statistical analysis of species accumulation curves revealed that only between 70 and 95% of all species to be expected have been found. Even for >1000 specimens per survey these figures seem hardly to increase with increasing collection effort, since a high proportion of species is always represented by a single or a few records only. Both ordination and cluster analysis suggests that geographical separation explains differences in species composition of the myxomycete assemblages much better than elevational differences. 5 The molecular component of this thesis is a phylogeographic study of the widely distributed tropical myxomycete Hemitrichia serpula. It is a morphologically distinct species with golden-yellow fructifications forming a reticulum. However, subtle variation in spore ornamentation points to cryptic speciation within this myxomycete. Using two independent molecular markers, 135 partial sequences of the small subunit (SSU) rRNA (a nuclear but extrachromosomal gene) and 30 partial sequences of the elongation factor 1 alpha gene (EF1A) (a nuclear gene), a study of 135 Hemitrichia serpula specimens collected worldwide revealed the existence of four clades that are likely to represent reproductively isolated biospecies, since each clade shows a unique combination of SSU and EF1A genotypes. A Mantel test with the partial SSU sequences indicated geographical differentiation, giving a correlation coefficient of 0.467 between the pairwise computed geographic and genetic distances, compared with the 95% confidence interval from 999 permutations (-0.013 to 0.021). Biogeographical analysis of the 40 SSU ribotypes showed clear intraspecific variation and geographic differentiation demonstrating a limited gene flow among the world population. We argue that the distribution of cryptic species in the different clade can be explained by ongoing, but still incomplete speciation. An event-based ancestral area reconstruction using the software S-DIVA employed in RASP showed that the probable origin of the ribotypes was a global dispersal event in the Neotropics. Additional species distribution models that were implemented for the three most prominent clades show different putative ranges. As such H. serpula supports the moderate endemicity hypothesis for protists. In summary, myxomycete assemblages in the Paleotropics (1) displayed a higher diversity than for Neotropical forests, (2) harbor unique taxa that differentiates those assemblages in spite of the expected similar macroecological all over the Tropics, (3) are affected by geographical barriers that likely causes speciation both at a morphospecies and biospecies level, and (4) follow the ubiquitous model in the sense that gene flow mediated by long-distance dispersal of spores is high enough that a species can fill out its entire putative range, but (5) the gene flow is not high enough to prevent variation in regional gene pools, which may lead to speciation and is better explained by the moderate endemicity model. Our data are still too limited to draw a comprehensive picture of the diversity of tropical myxomycetes, but the baseline information compiled with the aid of both classical ecology and molecular approaches from this study are first major steps towards this goal.
Myxomycetes (Amoebozoa, plasmodial slime molds) are one of the last larger groups of organisms where the biodiversity is not yet investigated by molecular methods, except for a very few cultivable model species. Based on the first phylogenies for the group produced in 2012 and 2013, this thesis work explores the genetic diversity of wild populations of myxomycetes, addressing two questions: 1. Does diversity and phylogenetic trees found with barcode markers fit the current morphological species concept, and do barcode markers reveal a lower or higher diversity than found by morphological characters? In the first case, morphological characters seen as decisive for species differentiation would be plastic (shaped by the environment), in the second case we must assume the existence of cryptic species. 2. Can genetic markers be used to see if natural populations of myxomycetes reproduce mainly sexual or asexual? Sexuality is proven to occur in the Amoebozoa, but asexual reproduction should be advantageous for habitat colonization. Experiments with cultivable species have shown that both reproductive modes occur in the myxomycetes. Two species complexes were chosen for an in-depth investigation. The first species is the common wood-inhabiting myxomycete Trichia varia (Pers. ex J.F. Gmel.) Pers., one of the first myxomycetes to be described and always seen as a variable, yet single, species. The second example involves a snowbank species so far known as Lamproderma atrosporum Meyl., which was recently transferred to a genus on its own, Meriderma Mar. Mey. & Poulain, and a morphological species concept, including several taxa, was proposed. Trichia varia belongs to the bright-spored myxomycetes. Partial sequences of three independent markers (nuclear small-subunit ribosomal RNA gene, SSU, extrachromosomal; protein elongation factor 1 alpha gene, EF1A, chromosomal; cytochrome oxidase subunit 1 gene, COI, mitochondrial) from 198 specimens resulted in a three-gene phylogeny containing three groups, within each group combinations of the single-marker genotypes occurred exclusively. Complete SSU sequences were generated for 66 specimens, which revealed six positions that can carry group I introns and putatively functional or degenerated homing endonuclease genes in two groups. All observations (genotypic combinations of the three markers, signs of recombination, intron patterns) fit well into a pattern of three cryptic biological species that reproduce predominantly sexual but are reproductively isolated. The pattern of group I introns and inserted homing endonuclease genes mounts evidence that the Goddard-Burt intron life cycle model applies to naturally occurring myxomycete populations. A total of 89 specimens of the dark-spored myxomycete genus Meriderma from five European mountain ranges were sequenced for partial genes of SSU and EF1A. The latter gene includes an extremely variable spliceosomal intron. Three clades, the two morphologically recognizable taxa M. fuscatum, M. aggregatum, and the morphologically complicated complex species M. atrosporum agg., were recovered. The EF1A-based phylogeny of the 81 specimens of M. atrosporum agg. resulted in seven subclades, with the two EF1A-haplotypes of a sequence sharing always one subclade for each of the 50 heterozygous specimens, a pattern consistent with the existence of several independent but sexually reproducing biospecies. Identical EF1A genotypes occurred more often within a regional population than in between. A simulation assuming panmixis within a biospecies but not in between, and isolation between mountain ranges suggested that similar numbers of shared genotypes can be created by chance through sexual reproduction alone. Numbers of haplotypes shared between mountain ranges correlate with geographical distance, suggesting occasional long-distance dispersal by spores. An enlarged data set containing 227 partial SSU sequences of Meriderma spp. identified 53 ribotypes, with a ribotype accumulation curve indicating 68.4±14.5 ribotypes to expect according to the Chao2 estimator. The topology of the SSU phylogeny generally confirms results from the partial SSU and EF1A data set of 89 specimens, where several putative biospecies could be recognized. A novel method for automated analyses of SEM images allows to derive quantitative descriptors for spore ornamentation, which were subjected to multivariate analyses. Spore ornamentation provided traits with the highest explanatory power in a multivariate statistics, whereas spore size and stalk length were much less significant. For some but not all putative biospecies a unique combination of morphological characters was found, which is in accordance with the hypothesis of instant sympatric 8 speciation via mutations creating incompatible strains splitting from existing biospecies. The morphologically recognizable taxa of the genus are described and a key for the genus Meriderma is given. To compare morphological and molecular diversity in lignicolous myxomycetes, all specimens found in a study covering the late-autumn aspect were sequenced, using partial SSU gene as a barcode marker. A total of 161 logs in the old-growth forest Eldena, northeastern Germany, was surveyed, resulting in 530 collections representing 27 taxa from 14 genera. Bright-spores species were far more abundant than dark-spored taxa. A phylogeny based on partial SSU sequences for bright-spored myxomycetes revealed morphospecies to be largely consistent with phylogenetic groups. Most but not all morphospecies may contain multiple ribotypes that cannot be differentiated by light microscopy. This first study backing up a traditional morphology-based survey by a full molecular component demonstrates that partial SSU sequences can function as reliable barcode markers for myxomycetes, but reveals as well a significant, yet not infinite, amount of hidden diversity. The main conclusions of this work, set up in the frame of a project funded by the German Research Council (DFG), are the following: 1. Sexual reproduction seems to be an important, if not the dominating mode (apart from clonal myxamoebal populations built up by binary fission) of reproduction in naturally occurring populations of myxomycetes. 2. From the two investigated species complexes we can expect many, if not most, morphopecies to be composed of reproductively isolated, sexually reproducing, biospecies. 3. Partial SSU sequences, as most widely used in this study, seem to represent suitable barcode markers for the group and can be used to distinguish the (usually cryptic) biospecies, although they alone do not allow any conclusions about reproductive isolation and speciation processes. 4. We have to expect a significant amount of hidden diversity in myxomycetes, which will increase the number of taxa from ca. 1000 recognized morphologically by a factor between two and ten.
Generally, all works dealt primarily with the biodiversity and phylogeny of leaf-inhabiting fungi of three Ficus species (F. benjamina, F. elastica and F. religiosa) with the exception of the bioprospecting which focused on discovering antimicrobial activities and secondary metabolite production. Investigations took place in natural and urban forests in the Philippines and in tropical greenhouse gardens in Germany.
Observed recent and expected future increases in frequency and intensity of climatic extremes in central Europe may pose critical challenges for domestic tree species. Continuous dendrometer recordings provide a valuable source of information on tree stem radius variations, offering the possibility to study a tree's response to environmental influences at a high temporal resolution. In this study, we analyze stem radius variations (SRV) of three domestic tree species (beech, oak, and pine) from 2012 to 2014. We use the novel statistical approach of event coincidence analysis (ECA) to investigate the simultaneous occurrence of extreme daily weather conditions and extreme SRVs, where extremes are defined with respect to the common values at a given phase of the annual growth period. Besides defining extreme events based on individual meteorological variables, we additionally introduce conditional and joint ECA as new multivariate extensions of the original methodology and apply them for testing 105 different combinations of variables regarding their impact on SRV extremes. Our results reveal a strong susceptibility of all three species to the extremes of several meteorological variables. Yet, the inter-species differences regarding their response to the meteorological extremes are comparatively low. The obtained results provide a thorough extension of previous correlation-based studies by emphasizing on the timings of climatic extremes only. We suggest that the employed methodological approach should be further promoted in forest research regarding the investigation of tree responses to changing environmental conditions.
Die mitteleuropäischen Flachbärlappe (Gattung Diphasiastrum) sind in Deutschland alle hochgradig gefährdet und können ohne geeignete Artenhilfsmaßnahmen hier nicht dauerhaft überleben. In der vorliegenden Arbeit werden die Grundlagen für ein Artenhilfsprogramm geschaffen, indem die Reproduktionsbiologie untersucht worden ist und die ökologischen Ansprüche und Gefährdungsursachen ermittelt wurden, um entsprechende Hilfsmaßnahmen für die Arten zu entwickeln.
Um Rückschlüsse auf das Reproduktionssystem der Eltern- und Hybridarten zu erhalten, wurde die genetische Diversität ermittelt. Dabei kam das fingerprinting-Verfahren AFLP zum Einsatz, womit Arten und genetisch verschiedene Individuen voneinander abgegrenzt werden können. Verwendet wurden die beiden Primer-Kombinationen EcoRI-AAG / VspI-CT und EcoRI-ACT / VspI-CAG. Die größte genetische Diversität der Elternarten weist D. complanatum auf, die überwiegend durch echte Fremdbefruchtung (outcrossing) entsteht, während die genetische Diversität der beiden anderen Elternarten D. alpinum und D. tristachyum gering ist und nur knapp oberhalb einer definierten Fehlerrate liegt. Die Proben der Hybridarten unterscheiden sich so stark voneinander, dass davon ausgegangen werden muss, dass dies immer wieder neu entstehende F1-Hybriden sind, wenngleich die Unterschiede bei D. oellgaardii vergleichsweise gering aufgrund der geringen genetischen Diversität der Elternarten D. alpinum und D. tristachyum ist.
Die Sporenproduktion in den Sporenständen wurde unter anderem direkt durch Zählung von Sporen in den Sporangien unterm Stereomikroskop und Zählung der Sporangien in den Sporenständen ermittelt. Sporangien von L. clavatum enthalten demnach 27735 (± 7492) Sporen pro Sporangium, 105,2 (± 3,7) Sporangien pro Sporenstand und hochgerechnet etwa 2,1 bis 3,8 Millionen Sporen pro Sporenstand.
Die terminale Fallgeschwindigkeit liegt für L. clavatum bei 2,16 (± 0,11) cm*s-1 und für D. complanatum bei 2,25 (± 0,10) cm*s-1. Die Sporen haben einen Durchmesser von 29,5 (± 2,0) μm bzw. 32,3 (± 2,5) μm. Die gemessene Geschwindigkeit liegt deutlich unter der theoretischen und lässt sich damit erklären, da Sporen keine perfekten Kugeln sind und aufgrund ihrer stark reliefierten Oberfläche Turbulenzen erzeugt werden, die den Fall verlangsamen.
Die Anzahl der in Entfernungen bis 200 m zu einer sporenbildenden Population fliegenden Sporen wurde mithilfe von vertikalen klebenden Sporenfallen bei D. complanatum, D. tristachyum und L. clavatum bestimmt. Nur für die Population von L. clavatum mit 11358 reifen Sporenständen auf kleiner Fläche wurden weitere Berechnungen durchgeführt. Folgende Funktion beschreibt die Anzahl der durch die Luft fliegenden Sporen in einer Höhe von etwa 40 cm über dem Boden in Abhängigkeit zur Entfernung x: f(x) = 45878*x-2,302 (R² = 0,9979). Es konnten selbst in 200 m Entfernung noch einzelne Sporen an den Sporenfallen nachgewiesen werden. Da die maximale theoretische Ausbreitungsdistanz bei nur knapp 130 m liegt, selbst wenn ein konstant horizontal wehender Wind von 100 km/h angenommen wird, müssen aufwärtsgerichtete Luftströmungen eine entscheidende Rolle bei der Fernausbreitung spielen.
Die Ansiedlungsversuche wurden im Thüringer Schiefergebirge am Grünen Band bei Brennersgrün (D. alpinum und D. tristachyum) und im Pöllwitzer Wald (D. complanatum) durchgeführt. Als Vergleichsart wurde wieder L. clavatum verwendet. Die Sprossverpflanzungen verliefen insgesamt erfolgreich mit einer Überlebensrate von 8% für D. alpinum, 17% für D. complanatum, 8% für D. tristachyum und 22% für L. clavatum. Der jährliche Rhizomzuwachs liegt bei 0,5 cm, 13,3 (± 1,8) cm, 7,5 cm bzw. 9,1 (± 4,0) cm für die entsprechenden Arten.
Die Vegetationsbedeckung vorher abgeplaggter Flächen liegt zwischen 39 und 53% nach zwei Jahren, jedoch mit großen Unterschieden selbst zwischen benachbarten Flächen und wird hauptsächlich durch ein schnelles Mooswachstum bestimmt.
Nach etwa fünf Monaten sind keine Sporen auf sterilem Nährstoffmedium gekeimt, obwohl diese unterschiedlich behandelt wurden, zum Beispiel mit Rauchgas, Hitze, konzentrierter Schwefelsäure oder durch Mörsern. Auch die Keimungsversuche an den Wuchsorten waren nach 2,5 Jahren erfolglos. Eine Erklärung kann ein Dormanzstadium unbekannter Dauer vor der Keimung sein.
Der Anzahl der jährlich gebildeten vertikalen Sprossbüschel wurde indirekt für je eine Population für D. zeilleri (2,5/Jahr) und D. issleri (2,0/Jahr) bestimmt, indem der Quotient aus der Anzahl der Sprossbüschel an der längsten Rhizomverbindung und dem bekannten Alter des Standorts ermittelt worden ist. Die Zugehörigkeit von Rhizomstücken zu einem Klon wurde mit der AFLP-Methode abgesichert. Die meisten Populationen in Deutschland werden demnach mehrere Jahrzehnte alt, jedoch ohne beobachtete Verjüngung über Prothallien. Eine Erklärung könnten die immer noch sehr geringen pH-Werte in den Unterböden von 3,6 (± 0,24) sein, die giftige Al3+-Ionen pflanzenverfügbar machen.
The “East German National Park Programme” of 1989/1990 was considered a coup de main, resulting in the immediate protection of 4.5% of the GDR’s territory. The authors of this programme later described the approach and its success as “using a window of opportunity during the transition phase of state and nation.” This leads to the question whether a state’s transformation period constitutes a preferred time frame and momentum for spatial conservation success.
Conservation efforts in Azerbaijan showed a similar success as the East German National Park Programme. In a country with the highest biodiversity in Europe, increasing the share of protected land from 5.0 % in 2001 to 10.3% in 2015 constitutes a remarkable achievement. Thus, the country became an interesting case study regarding the question whether “hot moments for conservation” exist in times of political and governmental changes, and if spatial success in nature conservation can be linked to political transformation. This thesis attempts to identify how the protected area (PA) network in Azerbaijan could be expanded by 100%, what achievements were made, and what conditions still need to be met for the quantitative and qualitative improvement of the PA network. To this end, I consider this increase under landscape-ecological, historical and institutional aspects. The local culture and political pre-sets in the country present additional issues for analysing the past 25 years of nature conservation in Azerbaijan.
Stoffflüsse in Makrophytensystemen: Ein Vergleich zwischen Küstenlagunen der südlichen Ostsee
(2017)
In früheren Jahrzehnten verschlechterte sich der ökologischen Zustand von zahlreichen inneren Küstengewässern der Ostsee durch die Eutrophierung, was z. B. zu intensiven Algenblüten führte. Submerse Makrophyten können den ökologischen Zustand von Süßgewässern verbessern, denn sie unterstützen z. B. die Sedimentation von suspendiertem Material und verringern die Resuspension. Zudem reduzieren sie indirekt das Phytoplankton, weil sie Zooplankton einen Prädationsschutz bieten und somit die Beweidung des Phytoplanktons durch das Zooplankton fördern. Es ist möglich, dass diese Rückkopplungsmechanismen in Brackgewässern weniger effektiv sind. Das Zooplankton ist anders zusammengesetzt und beweidet dadurch weniger effektiv das Phytoplankton. Außerdem wird es selbst, innerhalb der Makrophyten, durch bestimmte Fische und Invertebraten gefressen. In der vorliegenden Arbeit, wurden die Interaktionen zwischen submersen Makrophyten und ihrer abiotischen und biotischen Umgebung in zwei verschiedenen Küstengewässern der südlichen Ostsee untersucht: Vitter Bodden (mesotroph, Makrophyten-dominiert) und Darß-Zingster Boddenkette (DZBK, eutroph bis stark eutroph, Phytoplankton-dominiert). Die folgenden Parameter wurden von Juni bis September 2013 (Vitter Bodden) und von März bis November 2014 (DZBK) gemessen: Lichtattenuation, Konzentration von Gesamt-suspendiertem Material (TSM), von Chlorophyll a (Chl a), von Gesamt-Phosphor (TP) und von Gesamt-Stickstoff (TN). Zudem wurden die Verhältnisse TP zu TN und Chl a zu TP bestimmt. Der Beweidungsdruck des Zooplanktons auf das Phytoplankton wurde sowohl für den Tag als auch für die Nacht berechnet, in dem das jeweilige Zooplankton ausgezählt, die Biomasse und die Beweidungsrate berechnet wurde. Im Vitter Bodden wurde die Zusammensetzung der Makrophyten bestimmt, sowie ihr Bedeckungsgrad und ihr Anteil an der Wassersäule (PVI) in einer Wassertiefe <1 m geschätzt. In der DZBK wurde die Biomasse der Makrophyten bis in eine Wassertiefe von 1,9 m bestimmt. Die Tiefenverbreitung der Makrophyten war im Vitter Bodden nicht Licht-limitiert, aber in der DZBK, da sich dort der Hauptanteil der Makrophytenbiomasse nur bis in eine Wassertiefe von 1 m befand. In der DZBK hatte das Phytoplankton einen großen Anteil an der Lichtattenuation und limitierte dadurch vermutlich die Lichtverfügbarkeit nicht nur für die Makrophyten sondern auch für sich selbst. Aufgrund der TN zu TP Verhältnisse war das Phytoplankton in der DZBK P-limitiert, während es im Vitter Bodden durch beide Nährstoffe gleichzeitig limitiert war. Die Beweidung durch das Zooplankton konnte zeitweise vermutlich das Phytoplankton im Vitter Bodden reduzieren, aber nicht in der DZBK. Der Bedeckungsgrad der Makrophyten war hoch, aber sie hatten eine flache Wachstumsform und daher nur einen geringen PVI. Zusammenfassend kann gesagt werden, dass der vermutlich hohe Wasseraustausch mit der Ostsee und der fehlende Eintrag aus Fließgewässern verantwortlich für die hohe Lichtverfügbarkeit im Vitter Bodden sind. Ein möglicher Einfluss der Makrophyten auf Wassertrübung, Nährstoffe, Phytoplankton und Zooplankton wurde vermutlich durch diesen Wasseraustausch maskiert. Im Gegensatz dazu gab es keine Effekte der Makrophyten auf Nährstoffe in der Wassersäule, sowie auf Phytoplankton und Zooplankton in der DZBK, da die Makrophyten nur auf die Randbereiche der Bodden beschränkt sind. Da Sedimentation und Resuspension hauptsächlich die Wassertrübung beeinflussen, wurde in einem weiteren Teil der vorliegenden Arbeit ermittelt, in wie weit Wind-induzierte Wellen die Sedimentationsraten beeinflussen, wenn sie unmittelbar sedimentiertes Material wieder resuspendieren. Zu diesem Zweck wurden zwei verschiedene Sedimentationsfallen verwendet: Zylinderfallen (ZF) und Tellerfallen (TF). Die TF wurden in dieser Studie das erste Mal an einem Wellen-exponiertem Standort verwendet. Sie erlaubten, dass unmittelbar sedimentiertes Material wieder resuspendiert werden konnte, was die ZF nicht konnten. Sedimentationsraten wurden mit beiden Fallentypen in einer Wassertiefe zwischen 0,9 m und 1,6 m bestimmt. Die Wellenexposition wurde berechnet, indem die halbe Oberflächenwellenlänge (λ/2) durch die Wassersäule oberhalb der Fallen (dF) dividiert wurde. Eine hohe Wellenexposition war definiert als (λ/2) / dF >1. Die Sedimentationsraten in beiden Fallentypen waren von der Wellenexposition beeinflusst. Jedoch in gegensätzlicher Weise. Bei hoher Wellenexposition sedimentierte ein geringerer Anteil des TSM pro Stunde auf den TF als bei geringer Wellenexposition, während in den ZF ein größerer Anteil sedimentierte. Daher wurde die Sedimentationsrate bei hoher Wellenexposition mit den ZF überbestimmt. Die verwendeten TF sind ein viel versprechendes Mittel um Sedimentationsraten in flachen, Wellen-exponierten Orten abzuschätzen, denn sie reflektieren den unmittelbaren Einfluss von Wellenbewegungen auf die Sedimentation von suspendiertem Material.
Leaf-inhabiting fungi are a hyperdiverse group of microbiota found in all terrestrial habitats. Comparative studies targeting the drivers of endophytic fungal biodiversity are rare and identified multiple effectors, such as plant chemistry, climate and seasonal attributes. Our project aimed to study the pattern of the leaf-associated mycobiome of European beech (Fagus sylvatica) at altitudinally distinct sites to reveal diversity, composition and seasonal dynamics of fungal endophytes by a combination of metabarcoding, cultivation and subsequent ecological analyses. This thesis also intended to study the fungal relationship with biotic and abiotic factors: elevation, local site conditions, leaf biochemistry and leaf status. Metabarcoding and cultivation were applied for same leaf samples to trace both environmental drivers and method-dependent signals of the detected fungi. An experimental field site consisting of 100 (2-years old beech) trees was established called ‘beech phytometer’ system at two altitudes (517 and 975 m a.s.l.) in a German mountain forest. Beech trees were randomly selected from both sites as well as from neighboring beech trees. Ten trees from each site were chosen and 10 leaves per tree were sampled. Climatic and leaf biochemistry (Chlorophyll, flavonoid and nitrogen) data were seasonally (Autumn, Spring and Summer) investigated for two continuous years (Oct 2013 to Oct 2015) at these two elevations. In the first year (autumn, 2013) of the project (chapter 3.1), the leaf-inhabiting fungi of natural beech trees were investigated by using high-throughput sequencing (metabarcoding) at three altitudinally distinct sites (with timberline at 1381 m a.s.l.) in the German Alps. This paper focuses on a detailed description and evaluation of metabarcoding amplicon library preparation and a subsequent analytical workflow. Fungal diversity and community composition were compared as a function of different elevated sites and leaf status (i.e., vital or senescent). However, three investigation sites resulted in 969 OTUs (operational taxonomic units) from 820441 sequences. Taxonomic compositions (order) of beech fungi differed strongly among the three sites but were less distinct between the vital and the senescence leaves. Fungal community composition at valley site clearly differed from those of mountain and timberline where differences between mountain and timberline were less prominent. Vital and senescence leaf differed in fungal community structures indicating a strong dynamics of leaf fungi in autumn. Elevation and leaf status were found to be the main explaining factors, which affected the fungal richness and compositions. Another survey (Chapter 3.2) was conducted just after the establishment of the ‘beech phytometer’ trees in the same period (autumn 2013) where leaf mycobiome of the phytometer trees (trees originally came from Northern Germany and grown in nursery) were compared with the fungi of surrounding natural beech habitat at valley (517 m a.s.l.) and mountain site (975 m a.s.l.) in the same location “Untersberg”. Fungal diversity was lowest in the managed habitat in the nursery and was highest in natural habitat. Fungal diversity and compositions significantly associated the origin of the trees. Under natural conditions, the fungi were more diverse at lower altitudes than at higher altitudes. Additionally, leaf chlorophyll and flavonoid contents showed negative correlations with fungal richness in natural stands. In the second year (autumn 2014), another survey (chapter 3.3) was conducted on leaf endophytes of phytometer trees with metabarcoding and cultivation approaches to trace the environmental drivers and method-dependent indications. Metabarcoding resulted in 597 OTUs from 170480 curated ITS1 reads and cultivation revealed 70 OTUs from 438 culture-based Sanger sequences. Both approaches resulted in non-overlapping community compositions and pronounced differences in taxonomic classification and trophic stages. However, both methods revealed similar correlations of the fungal communities with local environmental conditions. Our results indicate undisputable advantages of metabarcoding over cultivation in terms of representation of the major functional guilds, rare taxa and diversity signals of leaf-inhabiting fungi. This stressed out the importance of cultivation for complementing sequence databases with good quality reference data and encouraged the use of both approaches in future microbial biodiversity assessment studies. Phytometer and natural trees were intensively investigated in this study (chapter 3.4) to assess the influence of site characteristics (altitudes, local microclimate), seasonality, leaf biochemistry and leaf age on fungal diversity and composition. In total, our analytical Illumina workflow resulted in 15703599 demultiplexed and ITS1 reads from 165 samples. Clustering at 97% similarity resulted in 1199 OTUs. Climatic parameters were significantly differed between valley and mountain on daily basis but were insignificantly differed on monthly basis. The compositional difference between phytometer and natural mycobiome was significant for combined data as well as for the seasonal data (Oct 2013-Oct 2014). We observed a strong seasonal turnover in phyllosphere fungi in both habitats over the two years of investigation, suggesting that the plant-fungal system not only responds to cyclic climatic conditions but depends as well on various parameters, e.g., geographic position, substrates age and surrounding vegetation. A side (chapter 3.5) study was done to see the connection between the foliar endophytes and foliar phenolic compounds of European aspen (Populus tremula) in the presence and absence of specialist beetles (Chrysomela tremula). A distinct pattern of the leaf endophytes was found to be associated with aspen genotype and chemotype, but this specificity disappeared in the presence of herbivorous beetles. This suggested that leaf endophytes responded to the herbivory in aspen. In general, the altitudinal difference is the most important explaining factor for fungal community differences, which shapes many dependent abiotic and biotic habitat factors. Regarding cost and time per sequence, metabarcoding is superior to cultivation approaches and offers surprisingly profound insights by yielding much more data, allowing to test at once multiple hypotheses in fungal ecology.
Water Consumption of Agriculture and Natural Ecosystems along the Ili River in China and Kazakhstan
(2017)
Whether mice are an appropriate model for S. aureus infection and vaccination studies is a matter of debate, because they are not considered as natural hosts of S. aureus. We previously identified a mouse-adapted S. aureus strain, which caused infections in laboratory mice. This raised the question whether laboratory mice are commonly colonized with S. aureus and whether this might impact on infection experiments. Publicly available health reports from commercial vendors revealed that S. aureus colonization is rather frequent, with rates as high as 21% among specific-pathogen-free mice. In animal facilities, S. aureus was readily transmitted from parents to offspring, which became persistently colonized. Among 99 murine S. aureus isolates from Charles River Laboratories half belonged to the lineage CC88 (54.5%), followed by CC15, CC5, CC188, and CC8. A comparison of human and murine S. aureus isolates revealed features of host adaptation. In detail, murine strains lacked hlb-converting phages and superantigen-encoding mobile genetic elements, and were frequently ampicillin-sensitive. Moreover, murine CC88 isolates coagulated mouse plasma faster than human CC88 isolates. Importantly, S. aureus colonization clearly primed the murine immune system, inducing a systemic IgG response specific for numerous S. aureus proteins, including several vaccine candidates. Phospholipase C emerged as a promising test antigen for monitoring S. aureus colonization in laboratory mice. In conclusion, laboratory mice are natural hosts of S. aureus and therefore, could provide better infection models than previously assumed. Pre-exposure to the bacteria is a possible confounder in S. aureus infection and vaccination studies and should be monitored.
Forests are and have been of major importance to cover a variety of societal needs. Today the demands on forests are ever increasing with sequestering carbon and balancing the climate, to name only a few. To cover those requirements forests need vital, productive, and sustainable. A difficult concept as such as the understanding of a healthy forest varies greatly. Nevertheless, forests still have to produce a sufficient amount of yield while threatened by changing climate conditions. These are predicted to bring extended and more intense drought periods as well as a higher frequency of storms and the promotion of secondary disturbances like insects calamities to also rise. In this complex situation of high and versatile demand the focus is on the allocation of the “right” forest. Forest management is requested to balance the needs of humans against those of wildlife against those of the trees themselves. To gain the respective knowledge on species responses and provenance growth, now and in the future research gaps need to be closed. All factors influencing tree growth and therefore ultimately yield need to be understood and special focus needs to be on the interactions within the forest ecosystem. One of the parameters in understanding aggregated tree growth is the dynamic of growth. This can be visualised by dendroecological methods, providing a picture of growth within the individual years. Growth dynamics are dependent on multiple factors, some, like soil being preconditioning and other like climate causing short-term responses. In this thesis I focus on the influence of climate on annual tree growth using a new approach of daily climate data to calculate climate-growth correlations. This method has the advantage of representing tree processes better than the former approach of using monthly means. Furthermore the program enables the user to feed climate scenarios and therefore estimate future growth. To gather information on species as well as provenance differences to provide advice to foresters I used different trials in Britain and Germany. On the British site different oak species were planted while the German sites are stocked with various spruce provenances. For the latter we additionally used stable carbon isotope analysis to calculate intrinsic water use efficiency. The climate-growth correlations revealed differences between the oak species with a generally higher linkage to precipitation than temperature. While the differences are clear, the question of thresholds and the role of extreme events became apparent in this work. VII Abstract Assessing the impact of extreme events using dendrometer data revealed little differences in the response to short term events of the three investigated species, oak, beech, and pine. We were able to pick up stimulus-response-relationships and as a novel result no species-specific responses were found when focusing on such a small time frame. The provenance trials offered the opportunity to investigate the potential of the use of daily climate data more closely. The two contrasting sites planted with six spruce provenances each gave an insight on the adaptive potential of provenances as well as an indication on the response times. Depending on the proceeding environmental and the local climate conditions decisions have to be made on the species or provenance selection. This thesis provides a method as well as insight on the behaviour of the important European species beech, oak, pine, and spruce. It, however, highlights the limitations such methods have for large scale estimates. While general trends on the response to specific soil factors can be used, the climatic responses, be it thresholds or climate-growth correlations can only be seen within the ecological context of their sampling region.
Zusammenfassung
Der Iran besitzt zwölf UNESCO-Biosphärenreservate, die reich an einmaligen Natur- und Kulturschätzen und hohem menschlichen Potenzial aus verschiedenen ethnischen Gruppen sind. Die ersten neun Biosphärenreservate wurden frühzeitig mit den ersten Biosphärenreser-vaten der Welt im Jahr 1976 gegründet, die auch gleichzeitig andere Kategorien der Schutz-gebiete im Iran wie Nationalparks, geschützte Lebensräume für Wildtiere und Naturschutzge-biete beinhalten und bis heute unter ihrem alten Status verwaltet werden. Damit entsprechen sie nicht den aktuellen internationalen Anforderungen an Biosphärenreservate und besteht die Gefahr, dass diese Gebiete in baldiger Zukunft ihre natürlichen und kulturellen Werte verlie-ren und irreversibel beschädigt werden.
Diese Studie untersucht und bewertet die zwei exemplarisch ausgewählten iranischen Bio-sphärenreservate Golestan und Dena unter Berücksichtigung der UNESCO-Kriterien, unter anderem die Ziele und Grundlagen der Sevilla-Strategie und der Internationalen Leitlinien für das Weltnetz der Biosphärenreservate (1995). Das Biosphärenreservat Golestan wurde im Jahr 1976 gegründet und ist somit eines der ältesten Biosphärenreservate des Irans. Bei dem im Jahre 2010 gegründeten Biosphärenreservat Dena, handelt es sich um das jüngste Biosphä-renreservat im Iran zu Beginn der Studie.
Beide Schutzgebiete sind gebirgig und beinhalten die wichtigsten Waldökosysteme mit einer großen Biodiversität. Das Biosphärenreservat Golestan befindet sich im Nordosten des Irans im östlichsten Teil des Elburs-Gebirge und Dena liegt im zentralen Zagros-Gebirge im Westiran.
Für den methodischen Ansatz dieser Studie wurde ein Methodenmix aus qualitativen Elemen-ten: Oral History, Interviews, offenen Fragen und Teilnehmender Beobachtung und quantita-tiven Elementen: SWOT-Analyse (engl. Akronym für Strengths (Stärken), Weaknesses (Schwächen), Opportunities (Chancen) und Threats (Bedrohungen) und Auswertung der Fra-gebögen mit Hilfe des statistischen Programms SPSS20 angewendet.
Die untersuchten Gruppen bestanden gemäß der jeweiligen Analyse aus Experten des De-partments für Umwelt (DoE) in Teheran, den Provinz-Umweltschutzbehörden von Golestan und Kohgiluye und Boyer Ahmad, Akademikern, der Nationale Commission for UNESCO in Teheran, Zeitzeugen, lokaler Bevölkerung, Rangern, Umwelt-NGOs (engl. Non-Governmental Organization), dem Tourismus-Sektor und den Umwelt-Medien.
Die Ergebnisse in dieser Studie zeigen, dass die Entwicklung der iranischen Biosphärenreser-vate seit ihrer Gründung 1976 bis heute von den Veränderungen der wirtschaftlichen, politi-schen und gesellschaftlichen Situation des Irans und demzufolge von den Veränderungen in der Organisationsstruktur des Departemants für Umwelt (DoE) und der Prioritätensetzung in Bezug auf die Gesetze zu Umwelt- und Naturschutz beeinflusst wurden.
Überdies stellen die Ergebnisse dar, dass in den beiden untersuchten Biosphärenreservaten Golestan und Dena hinsichtlich der internationalen UNESCO-Kriterien und Richtlinien ver-gleichsweise ähnliche Defizite und Mängel bestehen:
• fehlende nationale Rechtsstruktur für die Biosphärenreservate im Iran,
• fehlender Managementplan für Biosphärenreservate und somit auch schwaches Mana-gementsystem der Biosphärenreservate,
• Mangel an Kenntnissen über Biosphärenreservate,
• beschränkte Beteiligung an den Angelegenheiten der Biosphärenreservate seitens aller untersuchten Gruppen – von der lokalen Bevölkerung bis hin zu den staatlichen Ent-scheidungsträgern und
• ungenügende Zusammenarbeit zwischen Staat und Interessengruppen in diesen Gebie-ten.
Ebenso wurde in dieser Studie versucht, konkrete Lösungsansätze zur Verwirklichung der Ziele der Biosphärenreservate bzw. der Verbesserung ihrer aktuellen Situation zu empfehlen.
In diesem Zusammenhang ist es erforderlich, dass Gesetze für die Biosphärenreservate auf nationaler Ebene definiert und die vorhandenen Biosphärenreservate im Iran gründlich nach internationalen Kriterien untersucht und mit einem systematischen Managementplan auf wis-senschaftlicher Grundlage verwaltet werden. Des Weiteren benötigen diese Gebiete für ihre Funktionalität eine Erhöhung und Verbesserung der Kenntnisse über die Biosphärenreservate der aktiven Personen, sowie der Kooperation und Kommunikation zwischen allen zuständigen Behörden und Interessengruppen. Hiermit soll allen sozialen, kulturellen, geistigen und wirt-schaftlichen Anliegen der Interessengruppen, vor allem aber der lokalen Bevölkerung, Rech-nung getragen werden, entsprechend dem weltweiten Ansatz der UNESCO-Biosphärenreservate.
The rapid anthropogenic climate change that is projected for the 21st century is predicted to have severe impacts on ecosystems and on the provision of ecosystem services. With respect to the longevity of trees, forestry in particular has to adapt now to future climate change. This requires profound multidisciplinary knowledge on the direct and indirect climate sensitivity of forest ecosystems on various spatial scales. Predictions on growth declines due to increasing drought exposition during climate change are widely recognized for European beech (Fagus sylvatica L.), which is the major forest tree in European temperate deciduous forests. However, research from other continents or other biomes has shown that winter climate change may also affect forest growth dynamics due to declining snow cover and increased soil cooling. So far, this winter cold sensitivity is largely unexplored in Europe. Thus, particularly focussing on forest growth dynamics and winter cold sensitivity, the goal of this PhD-project was to explore how climate sensitivity of forest ecosystems differs regionally. By doing so, the project aimed to deliver insights about possibilities and limits of upscaling regional knowledge to a global understanding of climate sensitivity. To achieve these goals, this PhD-project integrated five studies (Manuscripts 1–5) that investigated the climate sensitivity of biogeochemical cycles, plant species composition in forests, and forest growth dynamics across spatial scales. In particular, a large-scale gradient-design field experiment simulated the influence of winter climate change on forest ecosystems by snow cover and soil temperature manipulations (Manuscript 1). This study indicated that soil cooling and decreased root nutrient uptake may indirectly reduce growth of adult forest trees. Moreover, this study indicated uniform ecological sensitivity to soil temperature changes across sites along a large winter temperature gradient (ΔT = 4 K across 500 km), irrespective of the site-specific history of snow cover conditions, which motivates upscaling from local winter climate change studies to the regional scale. Although regional climate drives growth of adult forest trees, local factors, such as site-specific edaphic conditions, might control plants in the forest understory. This assumption was tested by mapping the forest understory composition along the same winter temperature gradient as introduced above (Manuscript 2). Across sites, this study found that edaphic conditions explained the spatial turnover in the forest understory composition more than climate, which might moderate direct climate change impacts on the forest understory composition. However, edaphic conditions, forest structure, and climate are linked by triangular interactions. Thus, climate change might still indirectly affect the forest vegetation dynamics. Moreover, a dendroecological study focussed on the same winter temperature gradient from central to cold-marginal beech populations as above in order to identify gradual changes in summer drought and winter cold sensitivity in tree growth (Manuscript 3). Towards the cold distribution margin, the influence of drought on tree growth gradually decreased, while growth reductions were increasingly related to winter cold due to harsher winter climate. By a large-scale dendroecological network study assessed the relationship of growth dynamics to climate and reproductive effort in beech forests across Europe (Manuscript 4). Indeed, this study found the general pattern across the distribution range of beech that high temperature controlled growth indirectly via resource allocation to reproduction. However, the strong, direct drought signal that could be generally detected from dry-marginal to central populations vanished towards the cold-marginal populations, where the more focussed study of Manuscript 3 identified a stronger relationship of tree growth to winter cold. Further extending the scope of this PhD-thesis to global scales, litter decomposition rates were assessed across biomes (Manuscript 5). This study found a robust relationship between climate and decomposition rates, but it also demonstrated large within-biome variability on a local scale. These local scale differences might depend on habitat conditions that, in turn, could be modulated by climate change, which calls for a better exploration of indirect climate sensitivity. In conclusion, this PhD-thesis highlighted that multidisciplinary research can advance the understanding of ecological interactions in forest ecosystems under changing climate scenarios. In this PhD-project, a winter climate change experiment, where site-representative target trees were selected by means of dendroecology, contributed to a mechanistic understanding of winter cold sensitivity in forest growth dynamics. Dendroecological investigations then put the findings in a broader temporal and spatial context by describing local climate sensitivity of tree growth on different spatial scales. This thesis further shows that global generalizations about the relationship of climate and ecological processes in ecosystem models have to be critically reviewed for the need of local and regional adjustment because these processes might experience considerable regional- or local-scale variation. However, this thesis reports uniform sensitivity of ecological processes to altered winter soil temperature regimes across a large winter temperature gradient. Thus, upscaling from insights of previous winter climate change experiments to regional scales is encouraged.
Myxomycetes are protists belonging to the super-group Amoebozoa. The traditional taxonomic system, which is now largely outdated by molecular studies, recognizes five orders: Liceales, Trichiales, Physarales, Stemonitales and Echinosteliales. Molecular phylogenies revealed two basal clades: Physarales and Stemonitales (the so-called dark-spored myxomycetes) are the first; the other above-mentioned orders form the second (the bright-spored myxomycetes). However, except for Echinosteliales none of the traditional orders appears to be monophyletic in the traditionally used delimitation. The dark-spored myxomycetes encompass the majority of the described morphospecies. Due to the high genetic divergence in DNA sequences between the bright- and dark-spored myxomycetes, only the latter are considered in this dissertation. Historically myxomycetes have been described as fungi, due to their macroscopically visible fructifications which, though considerably smaller, resemble those of fungi. These fruit bodies provide enough morphological traits to support a morphological species concept with currently ca. 1000 species described. Therefore diversity studies of myxomycetes have been conducted for over 200 years and a substantial body of data on ecology and distribution of these fructifications exist. From these studies myxomycetes are known to form often distinct communities across terrestrial ecosystems with highly specific habitat requirements, such as snowbanks (nivicolous), herbivore dung (coprophilous) or decaying wood (xylophilous). However knowledge on the myxamoebae – the trophic life stage of the myxomycetes – is very scarce. Only recent advances in molecular techniques such as direct species identification based on DNA sequences from environmental samples (ePCR), have made studies of myxamoebae (and other microbes) possible. From these first molecular based studies myxomycetes are currently estimated to account for between 5 to almost 50% of all soil amoebae, and have been shown to be present in a wide variety of soils. To fully take advantage of these new methods, a molecular DNA marker needs to be established as well as a reference sequence database. The usability of a DNA marker gene depends on its ability to separate species by a distinction between intra- and interspecific divergence between sequences of the same and related species, the so-called ‘barcoding gap’.
The first part of this thesis (article I and II) deals with the subject of establishing such a DNA marker and database, and in doing so touches upon the subject of ‘what is a myxomycetes species?’
A total of 1 200 specimens were compiled into a reference database (the largest database to date of dark-spored myxomycetes). The genetic distance from sequence-to-sequence was used to assess genetic clade structures within morphospecies and putative biospecies (sexually isolated linages) were identified. The result was an estimate of hidden diversity, exceeding that of described morphospecies by 99%. The optimum sequence similarity threshold for OTU-picking (genetic species differentiation, denoted Operational Taxonomic Unit) with the used SSU marker was identified as 99.1% similarity.
The second part of this thesis (article III and IV) presents ecological studies conducted with NGS (ePCR) in which the established threshold and database are applied and are demonstrated to provide reliable and novel insights into the soil myxamoebae community. It is investigated whether the occurrence of fruit bodies reflects the distribution of soil myxamoebae, and the research questions ‘do myxomycetes show broader realized niches as soil amoebae than as fructifications?’ and ‘are myxamoebae distributions correlated to potential prey organisms (fungi and bacteria)?’ are investigated.
In the ecological study presented in article III parallel metabarcoding of bacteria, fungi and dark-spored myxomycete was used for the first time in a joint approach to analyze the communities from an elevational transect in the northern limestone German Alps (48 soil samples). Illumina sequencing of the soil samples revealed 1.68 Mio sequences of a section of the rRNA gene, which were assigned to 578 operational taxonomic units (OTU) from myxomycetes. These show a high similarity (>98%) to 42 different morphospecies (the respective figures for bacteria and fungi were 2.16/5710/215 and 3.68/6133/260, respectively). Multivariate analyses were carried out to disentangle microbial interplay and to identify the main environmental parameters determining the distribution of myxamoebae and thus setting the boundaries for their ecological niches. Potential interactions between the three target organisms were analysed by integrating community composition and phylogenetic diversity with environmental parameters. We identified niche differentiation for all three communities (bacteria, fungi and myxamoebae) which was strongly driven by the vegetation. Bacteria and fungi displayed similar community responses, driven by symbiont species and plant substrate quality. Myxamoebae showed a more patchy distribution, though still clearly stratified among genera, which seemed to be a response to both structural properties of the habitat and specific bacterial taxa. In addition we find an altitudinal species turn-over for all three communities, most likely explained by adaptation to harsh environmental conditions. Finally a high number of myxomycetes OTUs (associated with the genus Lamproderma) not currently represented in our reference database were found, representing potentially novel species. This study is the first to report niche differentiation between the guild of nivicolous (“snowbank”) myxomycetes and thus fine-scale niche differentiation among a predatory soil protist; identifying both potential food preferences and antagonistic interactions with specific bacterial taxa.
Finally, the second ecological study (article IV) focuses on comparing the distribution of myxamoebae revealed by ePCR of soil samples with fructifications collected from the same area (714 specimens determined to 30 morphospecies, which form 70 unique ribotypes that can be assigned to 45 ribotype clusters using a 99.1% similarity threshold). The study found a strong coherency between the two inventories, though with species specific relative differences in abundance, which can in part be attributed to the visibility of the fructifications. In addition, a year to year comparison of fructification records gives support to the hypothesis that the abundance of fructifications depends strongly on the onset of snowfall in the previous autumn and the soil temperature regime throughout the winter.
Because Moringa is rich in secondary metabolites and phenolics, we faced a challenge in extracting a pure DNA required for AFLP (the first proposed genotyping method). Later, different DNA isolation methods were tested to overcome the obstacles caused by phenolics and sugars, an AFLP protocol that worked well with the cultivated seedlings at the botanical garden in Greifswald. The markers for the Internal Transcribed Spacer (ITS) were as well tested that showed a monomorphic structure between all samples. Finally, SSR (microsatellite) markers were established. To optimize DNA extraction, the method of Doyle and Doyle was modified and optimized. This is an ideal method for obtaining a non-fragmented DNA that could be used for AFLP. In addition, two other DNA extraction methods; (KingFisher Flex robot using Omega M1130 extraction Kits, and spin columns and 96-plates using Stratec kits). Although we achieved similar results for both Robot kits (Omega) and Stratec kits, the amplification for most of the samples extracted with Robot did not work, therefore the Stratec kit was the method of choice as it has also a lower cost, combined with a high quality of DNA. For ITS, no polymorphism was found for 28 samples of M. peregrina from Sinai (sequences submitted to GenBank). However, since microsatellite markers of M. peregrina were not known, it was a challenge to try a cross amplification from other species with well-known microsatellite primers. Cross-amplification of 16 primers known from the related species M. oleifera was tested, and three multiplex PCR reactions were established after testing different annealing temperatures and different primers concentrations. This included 13 primers out of the 16 investigated markers which gave a reliable band. All methods used for genetic assessments for the different Moringa species are compiled in a comparative review to look for connections between the different Moringa species. For Moringaceae, M. oleifera and M. peregrina are closely related to each other. Both species have slender trunks, with thick, tough bark and tough roots and bilaterally symmetrical flowers with a short hypanthium. All but one SSR markers used in this study are highly informative However, the degree of polymorphy varied considerably within the 13 markers used. The Probability of Identity (PI) for all loci was 2.6 x 10-9 with high resolution. The percentage of polymorphic loci for all populations was 88.5±2.2; figures for single populations were 92.3%, 84.6%, 84.6%, and 92.3% for the wadis WM, WA, WF, and WZ, respectively. The genotype accumulation curve as well demonstrated that 7–8 markers were necessary to discriminate between 100% of the multilocus genotypes. Significant departures from HWE were detected for eight loci (P < 0.001), probably due a high degree of inbreeding within population. The observed (HO) and expected (HE) heterozygosities ranged from 0 to 0.86 and from 0 to 0.81, respectively. However, for the pooled population, excluding the monomorphic locus MO41, HO and HE ranged from 0.069 to 0.742 and from 0.126 to 0.73 with averages of 0.423 and 0.469, respectively. The mean of FST was 0.133, indicating that, due to the long generation time of M. peregrina, there is still relatively little differentiation between the four remaining populations. An analysis of molecular variance (AMOVA) revealed that the old populations of M. peregrina are still genetically diverse where 75% of variance was recorded within individuals and 83% within populations. An analysis with STRUCTURE, varying the parameter K between 1 and 7, revealed the most pronounced genetic structure for K=3, thus uniting the populations from two neighboured wadis (W. Agala and W. Feiran). The three groups seem to be now genetically isolated. (They may be remainders of a formerly contiguous population, especially when considering the change towards a drier climate in Northern Africa within the last 6000 years). Six clones of each two individuals collected from the same wadi were found, pointing to vegetative dispersal via broken twigs, which may have rooted after flash floods. It may be an alternative mode of reproduction under harsh conditions. Our data reveal a low gene flow between three of the four wadis, suggesting that the trees are relictual populations. In general, conservation of populations from the three genetically most diverse wadis and cross-breeding of trees within a reforestation program is recommended as an effective strategy to ensure the survival of M. peregrina at Sinai, Egypt.
Climate Change-Induced Shift of Tree Growth Sensitivity at a Central Himalayan Treeline Ecotone
(2018)
Planning Modes for Major Transportation Infrastructure Projects (MTIPs): Comparing China and Germany
(2018)
Production-Integrated Compensation in Environmental Offsets—A Review of a German Offset Practice
(2018)
Species of the genus Wolffia are traditionally used as human food in some of the Asian countries. Therefore, all 11 species of this genus, identified by molecular barcoding, were investigated for ingredients relevant to human nutrition. The total protein content varied between 20 and 30% of the freeze-dry weight, the starch content between 10 and 20%, the fat content between 1 and 5%, and the fiber content was ~25%. The essential amino acid content was higher or close to the requirements of preschool-aged children according to standards of the World Health Organization. The fat content was low, but the fraction of polyunsaturated fatty acids was above 60% of total fat and the content of n-3 polyunsaturated fatty acids was higher than that of n-6 polyunsaturated fatty acids in most species. The content of macro- and microelements (minerals) not only depended on the cultivation conditions but also on the genetic background of the species. This holds true also for the content of tocopherols, several carotenoids and phytosterols in different species and even intraspecific, clonal differences were detected in Wolffia globosa and Wolffia arrhiza. Thus, the selection of suitable clones for further applications is important. Due to the very fast growth and the highest yield in most of the nutrients, Wolffia microscopica has a high potential for practical applications in human nutrition.
Quantitative reconstructions of past vegetation cover commonly require pollen productivity estimates (PPEs). PPEs are calibrated in extensive and rather cumbersome surface-sample studies, and are so far only available for selected regions. Moreover, it may be questioned whether present-day pollen-landcover relationships are valid for palaeo-situations. We here introduce the ROPES approach that simultaneously derives PPEs and mean plant abundances from single pollen records. ROPES requires pollen counts and pollen accumulation rates (PARs, grains cm−2 year−1). Pollen counts are used to reconstruct plant abundances following the REVEALS approach. The principle of ROPES is that changes in plant abundance are linearly represented in observed PAR values. For example, if the PAR of pine doubles, so should the REVEALS reconstructed abundance of pine. Consequently, if a REVEALS reconstruction is “correct” (i.e., “correct” PPEs are used) the ratio “PAR over REVEALS” is constant for each taxon along all samples of a record. With incorrect PPEs, the ratio will instead vary. ROPES starts from random (likely incorrect) PPEs, but then adjusts them using an optimization algorithm with the aim to minimize variation in the “PAR over REVEALS” ratio across the record. ROPES thus simultaneously calculates mean plant abundances and PPEs. We illustrate the approach with test applications on nine synthetic pollen records. The results show that good performance of ROPES requires data sets with high underlying variation, many samples and low noise in the PAR data. ROPES can deliver first landcover reconstructions in regions for which PPEs are not yet available. The PPEs provided by ROPES may then allow for further REVEALS-based reconstructions. Similarly, ROPES can provide insight in pollen productivity during distinct periods of the past such as the Lateglacial. We see a potential to study spatial and temporal variation in pollen productivity for example in relation to site parameters, climate and land use. It may even be possible to detect expansion of non-pollen producing areas in a landscape. Overall, ROPES will help produce more accurate landcover reconstructions and expand reconstructions into new study regions and non-analog situations of the past. ROPES is available within the R package DISQOVER.
Tree growth at northern boreal treelines is generally limited by summer temperature, hence tree rings serve as natural archives of past climatic conditions. However, there is increasing evidence that a changing summer climate as well as certain micro-site conditions can lead to a weakening or loss of the summer temperature signal in trees growing in treeline environments. This phenomenon poses a challenge to all applications relying on stable temperature-growth relationships such as temperature reconstructions and dynamic vegetation models. We tested the effect of differing ecological and climatological conditions on the summer temperature signal of Scots pine at its northern distribution limits by analyzing twelve sites distributed along a 2200 km gradient from Finland to Western Siberia (Russia). Two frequently used proxies in dendroclimatology, ring width and maximum latewood density, were correlated with summer temperature for the period 1901–2013 separately for (i) dry vs. wet micro-sites and (ii) years with dry/warm vs. wet/cold climate regimes prevailing during the growing season. Differing climate regimes significantly affected the temperature signal of Scots pine at about half of our sites: While correlations were stronger in wet/cold than in dry/warm years at most sites located in Russia, differing climate regimes had only little effect at Finnish sites. Both tree-ring proxies were affected in a similar way. Interestingly, micro-site differences significantly affected absolute tree growth, but had only minor effects on the climatic signal at our sites. We conclude that, despite the treeline-proximal location, growth-limiting conditions seem to be exceeded in dry/warm years at most Russian sites, leading to a weakening or loss of the summer temperature signal in Scots pine here. With projected temperature increase, unstable summer temperature signals in Scots pine tree rings might become more frequent, possibly affecting dendroclimatological applications and related fields.