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Abstract
The role of future forests in global biogeochemical cycles will depend on how different tree species respond to climate. Interpreting the response of forest growth to climate change requires an understanding of the temporal and spatial patterns of seasonal climatic influences on the growth of common tree species. We constructed a new network of 310 tree‐ring width chronologies from three common tree species (Quercus robur, Pinus sylvestris and Fagus sylvatica) collected for different ecological, management and climate purposes in the south Baltic Sea region at the border of three bioclimatic zones (temperate continental, oceanic, southern boreal). The major climate factors (temperature, precipitation, drought) affecting tree growth at monthly and seasonal scales were identified. Our analysis documents that 20th century Scots pine and deciduous species growth is generally controlled by different climate parameters, and that summer moisture availability is increasingly important for the growth of deciduous species examined. We report changes in the influence of winter climate variables over the last decades, where a decreasing influence of late winter temperature on deciduous tree growth and an increasing influence of winter temperature on Scots pine growth was found. By comparing climate–growth responses for the 1943–1972 and 1973–2002 periods and characterizing site‐level growth response stability, a descriptive application of spatial segregation analysis distinguished sites with stable responses to dominant climate parameters (northeast of the study region), and sites that collectively showed unstable responses to winter climate (southeast of the study region). The findings presented here highlight the temporally unstable and nonuniform responses of tree growth to climate variability, and that there are geographical coherent regions where these changes are similar. Considering continued climate change in the future, our results provide important regional perspectives on recent broad‐scale climate–growth relationships for trees across the temperate to boreal forest transition around the south Baltic Sea.
Introduction: At the cellular level, acute temperature changes alter ionic conductances, ion channel kinetics, and the activity of entire neuronal circuits. This can result in severe consequences for neural function, animal behavior and survival. In poikilothermic animals, and particularly in aquatic species whose core temperature equals the surrounding water temperature, neurons experience rather rapid and wide-ranging temperature fluctuations. Recent work on pattern generating neural circuits in the crustacean stomatogastric nervous system have demonstrated that neuronal circuits can exhibit an intrinsic robustness to temperature fluctuations. However, considering the increased warming of the oceans and recurring heatwaves due to climate change, the question arises whether this intrinsic robustness can acclimate to changing environmental conditions, and whether it differs between species and ocean habitats.
Methods: We address these questions using the pyloric pattern generating circuits in the stomatogastric nervous system of two crab species, Hemigrapsus sanguineus and Carcinus maenas that have seen a worldwide expansion in recent decades.
Results and discussion: Consistent with their history as invasive species, we find that pyloric activity showed a broad temperature robustness (>30°C). Moreover, the temperature-robust range was dependent on habitat temperature in both species. Warm-acclimating animals shifted the critical temperature at which circuit activity breaks down to higher temperatures. This came at the cost of robustness against cold stimuli in H. sanguineus, but not in C. maenas. Comparing the temperature responses of C. maenas from a cold latitude (the North Sea) to those from a warm latitude (Spain) demonstrated that similar shifts in robustness occurred in natural environments. Our results thus demonstrate that neuronal temperature robustness correlates with, and responds to, environmental temperature conditions, potentially preparing animals for changing ecological conditions and shifting habitats.
Many of the world’s most biodiverse regions are found in the poorest and second most populous continent of Africa; a continent facing exceptional challenges. Africa is projected to quadruple its population by 2100 and experience increasingly severe climate change and environmental conflict—all of which will ravage biodiversity. Here we assess conservation threats facing Africa and consider how these threats will be affected by human population growth, economic expansion, and climate change. We then evaluate the current capacity and infrastructure available to conserve the continent’s biodiversity. We consider four key questions essential for the future of African conservation: (1) how to build societal support for conservation efforts within Africa; (2) how to build Africa’s education, research, and management capacity; (3) how to finance conservation efforts; and (4) is conservation through development the appropriate approach for Africa? While the challenges are great, ways forward are clear, and we present ideas on how progress can be made. Given Africa’s current modest capacity to address its biodiversity crisis, additional international funding is required, but estimates of the cost of conserving Africa’s biodiversity are within reach. The will to act must build on the sympathy for conservation that is evident in Africa, but this will require building the education capacity within the continent. Considering Africa’s rapidly growing population and the associated huge economic needs, options other than conservation through development need to be more effectively explored. Despite the gravity of the situation, we believe that concerted effort in the coming decades can successfully curb the loss of biodiversity in Africa.
Abstract
Climate change may force organisms to adapt genetically or plastically to new environmental conditions. Invasive species show remarkable potential for rapid adaptation. The ovoviviparous New Zealand mud snail (NZMS), Potamopyrgus antipodarum, has successfully established across Europe with two clonally reproducing mitochondrial lineages since its arrival in the first half of the 19th century. Its remarkable variation in shell morphology was shown to be fitness relevant. We investigated the effects of temperature on shell morphology across 11 populations from Germany and the Iberian Peninsula in a common garden across three temperatures. We analyzed size and shape using geometric morphometrics. For both, we compared reaction norms and estimated heritabilities. For size, the interaction of temperature and haplotype explained about 50% of the total variance. We also observed more genotype by environment interactions indicating a higher degree of population differentiation than in shape. Across the three temperatures, size followed the expectations of the temperature‐size rule, with individuals growing larger in cold environments. Changes in shape may have compensated for changes in size affecting space for brooding embryos. Heritability estimates were relatively high. As indicated by the very low coefficients of variation for clonal repeatability (CVA), they can probably not be compared in absolute terms. However, they showed some sensitivity to temperature, in haplotype t more so than in z, which was only found in Portugal. The low CVA values indicate that genetic variation among European populations is still restricted with a low potential to react to selection. A considerable fraction of the genetic variation was due to differences between the clonal lineages. The NZMS has apparently not been long enough in Europe to accumulate significant genetic variation relevant for morphological adaptation. As temperature is obviously not the sole factor influencing shell morphology, their interaction will probably not be a factor limiting population persistence under a warming climate in Europe.
Weltweit nimmt der Druck auf die natürlichen Wasserressourcen zu. Dies hat unterschiedliche Gründe, ist jedoch zum größten Teil verursacht durch einen stetig ansteigenden Bedarf. Faktoren wie Bevölkerungswachstum, die In- und Extensivierung landwirtschaftlicher Produktion, veränderte Lebensstile mit gleichzeitiger Erhöhung des individuellen Wasserverbrauchs, tragen regional unterschiedlich zu einer Verknappung bei. Neben dem anthropogenem Einfluss auf Wasserressourcen stellt Klimawandel ein zusätzliches Problem dar. Viele Länder sind sich der begrenzten Verfügbarkeit ihrer Ressourcen zwar bewusst, einfache Lösungen zur nachhaltigen Bewältigung des steigenden Bedarfs existieren jedoch zumeist nicht. Momentan folgen die meisten Länder dem Paradigma des ökonomischen Wachstums, um Ernährungssicherheit, Beschäftigung und sozialen Fortschritt zu gewährleisten. Die exzessive Ausbeutung natürlicher Ressourcen stellt immer noch den Standard dar, um sozio-ökonomische Entwicklung zu ermöglichen. Daher ist bei der Vereinbarung von ökonomischem Wachstum und Umweltnachhaltigkeit nur schwer ein Fortschritt zu erkennen. In diesem Zusammenhang spielt Wasser eine Schlüsselrolle: der Zugang zu und die Nutzung von Wasser war und ist eine wesentliche Voraussetzung für sozio-ökonomische Entwicklung. In den vergangenen Jahrzehnten wurden kritische Wasserlimits trotz wachsenden Bedarfs überschritten. Demnach mangelt es in vielen Ländern an einem angepassten Wassermanagement. Zudem sind Maßnahmen zum Schutz der Wasserressourcen insbesondere im Hinblick auf eine zukünftige Nutzung unzureichend. Nord-Afrika ist eine Region mit schwerwiegenden Problemen bezüglich ausreichender Wasserverfügbarkeit. Die Übernutzung hat bereits zu einem alarmierenden Rückgang vorhandener Frischwasserressourcen geführt. Wasser ist aber gleichermaßen die Schlüsselressource für ökonomisches Wachstum und sozio-ökonomische Entwicklung. Daher ist die Implementierung einer adäquaten Wasserbedarfsteuerung unentbehrlich. Der thematische Fokus dieser Dissertation liegt auf der Analyse der problematischen Wassersituation im nordöstlichen Marokko. In der Region sind Wasserressourcen in hohem Maße vulnerabel durch einen stetig steigenden Bedarf. Dieser ist verursacht durch Bevölkerungswachstum, hohen landwirtschaftlichen Bewässerungsbedarf sowie durch die jüngst erfolgte Etablierung eines wasser-intensiven Tourismussektors. Zusätzlich wirkt sich Klimawandel auf die bereits übernutzten Ressourcen aus. Der momentane Mangel an angepassten Strategien als Antwort auf die Herausforderungen eines steigenden Bedarfs verstärkt durch Klimawandel hat negative Auswirkungen auf die regional angestrebte sozio-ökonomische Entwicklung. Diese Dissertation untersucht die Gründe einer sich verringernden regionalen Wasserverfügbarkeit unter Einbeziehung des menschlichen sowie des klimatischen Einflusses auf das Wasserbudget. Die regionale Ökonomie hängt ab von der ausreichender Wasserverfügbarkeit. Wasserpolitiken sind daher wichtig und sollten die Ursachen der Wasserprobleme realistisch betrachten. Der räumliche Rahmen vorliegender Analyse ist das Einzugsgebiet des Moulouya-Flusses. Dieses stellt eine hydrologische Einheit dar, und umfasst ca. 54.000 km2. Der Fluss selbst hat eine Länge von ca. 600 km und mündet in einem Delta mit einzigartigen Feuchtgebieten an der Küste des Mittelmeers. Der Moulouya-Fluss ist der wichtigste Frischwasserversorger der gesamten nordöstlichen Landesregion. Mit einer jährlichen Niederschlagsumme von ca. 330 mm gehört die Region zu den trockensten des Landes. Ein Ziel der vorliegenden Arbeit ist es, Forschungslücken zu füllen und Information bereitzustellen, die Zusammenhänge der Exponiertheit gegenüber Wasserstress verdeutlichen können. Zudem soll die Etablierung eines verbesserten Wassermanagements als Grundlage sozio-ökonomischer Entwicklung unterstützt werden. In einer interdisziplinären Herangehensweise wird Wasserknappheit in der Region empirisch analysiert. In vier wissenschaftlichen Artikeln werden die Gründe und das Ausmaß von Vulnerabilität sowie der Entwicklungs-Governance-Kontext im Hinblick auf Wasserknappheit untersucht. Artikel I erörtert die spezifischen regionalen Probleme der Küstenzone, die sich unter starkem Entwicklungsdruck befindet und die Auswirkungen des Klimawandels bereits spürt. Artikel II kontrastiert den menschlichen Einfluss auf Frischwasserverfügbarkeit (Indikatoren: Bevölkerungswachstum, Wassernachfrage) mit den möglichen Auswirkungen einer regionalen Klimaveränderung (Indikatoren: Niederschlag, Temperaturen, Evapotranspiration). Artikel III analysiert den zusätzlichen Wasserbedarf in Nord-Ost-Marokko, der durch die Etablierung von Luxustourismusresorts entsteht, die in der Küstenzone errichtet werden. Artikel IV diskutiert die Nachhaltigkeit der regionalen Entwicklungspläne im Lichte des Wasserproblems. Die Ergebnisse zeigen, dass die Wassernachfrage die Wasserverfügbarkeit bereits überschritten hat. Bevölkerungswachstum und wasserbasierte ökonomische Entwicklung werden diesen Trend verstärken, so dass die Region mit hoher Wahrscheinlichkeit unter problematischen Wassermangel leiden wird. Die Analysen regionaler Klimatrends deuten hin auf eine Verschiebung der Niederschlagsmuster bei gleichzeitigem Rückgang der Niederschlagssummen. In Verbindung mit den aktuellen Nachfrageraten ist die Verfügbarkeitsgrenze bereits überschritten. Regierungspläne, die den Ausbau des Luxustourismus fördern, haben zum Ziel, die regionale Ökonomie zu diversifizieren und die Abhängigkeit vom Agrarsektor zu reduzieren. Luxustourismus ist allerdings auf permanente Wasserversorgung angewiesen und wird dadurch eine zusätzliche Belastung für die regionale Wasserverfügbarkeit darstellen. Alle vier Artikel betonen die Notwendigkeit für rasche soziale und institutionelle Antworten auf die beschriebenen Herausforderungen, um die Wasserversorgung zu gewährleisten. Daher werden folgende Empfehlungen formuliert: • Erhöhung der Wassereffizienz (z.B. durch modernisierte Bewässerungstechnologien, “green water management” für regenwasser-gespeiste Bewässerung); • Etablierung moderner Wassertechnologien zum Wasserschutz, oder unkonventioneller Wasserproduktion); • Etablierung urbaner und ländlicher Abwassersammlung und –behandlung, sowie Wiederverwertung; • Einbeziehung von Klimawandel in Berechnungen des zukünftigen Wasserbudgets; • Aufbau von kleinskaligen Wasseraufbereitungsanlagen für wasserintensive Unternehmen, z.B. Tourismusinfrastrukturen. Derartige Maßnahmen sind kostenintensiv. Dennoch ist es das Ziel dieser Dissertation zu betonen, dass natürliche Wasservorräte begrenzt und in Nord-Ost-Marokko bereits stark degradiert sind. Ein besseres Verständnis der jeweiligen Einflussfaktoren, anthropogen oder klimatisch verursacht, ist die Basis für die Implementation problem-ausgerichteter Anpassungsstrategien. Anthropogen verursachte Auswirkungen können durch Politiken beeinflusst werden. Wenn wasserbasierte Volkswirtschaften nicht adäquat auf den zunehmenden Druck auf Wasserressourcen reagieren, riskieren sie ökonomisches Scheitern.
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.
Relative importance of plastic and genetic responses to weather conditions in long-lived bats
(2022)
In the light of the accelerating pace of environmental change, it is imperative to understand how populations and species can adapt to altered environmental conditions. This is a crucial step in predicting current and future population persistence and limits thereof. Genetic adaption and phenotypic plasticity are two main mechanisms that can mediate the process of adaptation and are of particular importance for non-dispersing species. While phenotypic plasticity may enable individuals to cope with short term environmental changes, genetic adaptation will often be required for populations to survive in situ over longer time spans. However, a rapid genetic response is expected particularly in species with fast life histories or large population sizes, leaving species with slow life histories potentially at higher extinction risk. The Bechstein’s bat (Myotis bechsteinii) is a mammal of 10 g weight that - despite its small size - is characterized by a slow life history, with low reproductive output and long lifespan, and is already considered to be of high conservation concern. Past work demonstrated body size to be a highly fitness-relevant trait in Bechstein’s bats. Body size is further known to be a pivotal trait shaping the pace of life histories in numerous species. Simultaneously, many studies reported noteworthy changes in body size as a response to shifting environments across different taxa. This suggested a potential for high plasticity in this trait in Bechstein’s bats as well; however, changes in body size could have vital impacts on demographic rates.
Therefore, this dissertation investigated the following questions: firstly, what shapes the fundamental development of body size in M. bechsteinii, and, specifically, is there an impact of weather conditions on body size? If so, in what form and magnitude? Secondly, how does body size subsequently influence the pace of life in females? What is the cost of a faster or slower pace of life, and how does fitness compare across individuals with slow and fast life histories? And finally, to what extent can changes in body size be attributed to either phenotypic plasticity or genetic adaptation? What is the evolutionary potential of body size in the populations? And, consequently, what implications can we draw regarding population persistence of these colonies?
To answer these questions, we analyzed a long-term dataset of over two decades collected from four wild Bechstein’s bat colonies. We used individual-based data on survival, reproduction and body size, built multi-generational pedigrees, and combined everything with meteorological data. In Manuscript 1 we found that, in contrast to the declining body size observed in many species, body size in Bechstein’s bats increased significantly over the last decades. We demonstrated that ambient temperature was linked to the development of body size and identified a sensitive time period in the prenatal growth phase, in which body size was most susceptible to the impact of temperature. We established that warmer summers resulted in larger bats, but that these large bats had higher mortality risks throughout their lives. Manuscript 2 then revealed the influence of body size on the pace of life in Bechstein’s bats and demonstrated high plasticity in intraspecific life history strategies. Large females were characterized by a faster pace of life and shorter lifespans, but surprisingly, lifetime reproductive success remained remarkably stable across individuals with different body sizes. The acceleration of their pace of life means that larger females compensated for their reduced longevity by an earlier reproduction and higher fecundity to reach similar overall fitness. Ultimately, differences in body size resulted in changes in population growth rate via the impact of size on generation times. Results of Manuscript 3 were then able to clarify the extent to which changes in body size were founded on either phenotypic plasticity or genetic adaptation. We demonstrated a particularly low heritability in hot summers, indicating that variance in body size was mostly driven by phenotypic plasticity, with few genetic constraints. During cold summers, behavioural adaptations by reproducing bats seem to be able to mitigate negative effects of cold temperatures. These behaviours, such as social aggregation or preference for warm roosts, are, however, essentially irrelevant in hot environments. In addition, a low evolvability of forearm length points to a low capacity to respond to selection pressures associated with the trait.
We can conclude that body size in M. bechsteinii has increased over the last two decades as a response to global warming and is only slightly constrained by its genetic underpinnings. We can further demonstrate a direct link between body size and the pace of life histories in the Bechstein’s bat populations and how changes in body size impact demographic rates via this linkage. In the context of climate change and hotter summers, our findings consequently suggest that body size will likely increase further if warm summers continue to become more frequent. Whether this plastic response of body size proves to be adaptive in the long term, however, remains to be seen. While, up to this point, switching to a faster life history has been successful in compensating fitness losses, this strategy requires sufficient habitat quality and is likely risky in times when extreme weather events are becoming more frequent, as predicted by most climate change scenarios.
Dendrochronology, the science of tree-rings is a tool which has been widely used for many years for understanding changes in the environment, as trees react to environmental changes over time. In the contemporary situation, where climate warming in the Arctic is unequivocal and its effects on the Alpine and tundra ecosystems are seen pronouncedly in the past decade, the role of dendro-studies and the use of trees and shrubs alike as proxies of change has become critical. Studies clearly indicate that warming in the Arctic and Alpine tundra has resulted in increased vegetation in recent years. Shrubs, in these sensitive ecosystems, have proven to be highly instrumental as they likely benefit from this warming and hence are good indicators and auditees of this change. Therefore, in this study, we investigate the potential of shrubs in the evolving field of dendro-ecology/climatology.
Studies from classical dendrochronology used annual rings from trees. Further, because of shrub sensitivity to contemporary change, shrub-based dendrochronological research has increased at a notable scale in the last decade and will likely continue. This is because shrubs grow even beyond the tree line and promise environmental records from areas where tree growth is very limited or absent. However, a common limitation noted by most shrub studies is the very hard cross-dating due to asynchronous growth patterns. This limitation poses a major hurdle in shrub-based dendrochronological studies, as it renders weak detection of common signals in growth patterns in population stands. This common signal is traced by using a ‘site-chronology’.
In this dissertation, I studied shrub growth through various resolutions, starting from understanding radial growth within individuals along the length of the stem, to comparison of radial growth responses among male and female shrubs, to comparing growth responses among trees and shrubs to investigation of biome-wide functional trait responses to current warming. Apart from Chapter 4 and Chapter 6, I largely used Juniperus communis sp. for investigations as it is the most widely distributed woody dioecious species often used in dendro-ecological investigations in the Northern Hemisphere.
Primarily, we investigated radial growth patterns within shrubs to better understand growth within individuals by comparing different stem-disks from different stem heights within individuals. We found significant differences in radial growth from different stem-disks with respect to stem heights from same individuals. Furthermore, we found that these differences depending on the choice of the stem-disk affect the resulting site-chronology and hence climate-sensitivity to a substantial extent and that the choice of a stem-disk is a crucial precursor which affects climate-growth relationships.
Secondly, we investigated if gender difference – often reported causing differential radial growth in dioecious trees – is an influential factor for heterogeneous growth. We found that at least in case of Juniperus communis. L and Juniperus communis ssp nana. WILLD there is no substantial gender biased difference in radial growth which might affect the site-chronology. We did find moderate differences between sexes in an overall analysis and attribute this to reproductive effort in females.
In our study to test the potential of shrubs for reconstruction, we used a test case of Alnus viridis ssp crispa. We found a strong correlation between ring-width indices and summer temperature. Initially, the model failed the stability tests when we tested the stability of this relation using a response function model. However, using wood-anatomical analysis we discovered that this was because of abnormal cell-wall formation resulting in very thin rings in the year 2004. Pointer year analysis revealed that the thin rings were caused because of a moth larval outbreak and when corrected for these rings the model passed all stability tests.
Furthermore, to see if trees and shrubs growing in same biomes react to environmental changes similarly, a network analysis with sites ranging from the Mediterranean biome to the Ural Mountains in Russia was carried out. We found that shrubs react better to the current climate warming and have a decoupled divergent temperature response as compared to coexisting trees. This outcome reiterated the importance of shrub studies in relation to contemporary climate change. Even though trees and shrubs are woody forms producing annual rings, they have very different growth patterns and need different methods for analysis and data treatment.
Finally, in a domain-wide network analysis from plant-community vegetation survey, we investigated functional relationships between plant traits (leaf area, plant height, leaf nitrogen content, specific leaf area (SLA), and leaf dry matter content (LDMC)) and abiotic factors viz. temperature and soil moisture. We found a strong relation between summer temperature and community height, SLA and LDMC on a spatial scale. Contrarily, the temporal-analysis revealed SLA and LDMC lagged and did not respond to temperature over the last decade. We realized that there are complex interactions between intra-specific and inter-specific plant traits which differ spatially and temporally impacting Arctic ecosystems in terms of carbon turn over, surface albedo, water balance and heat-energy fluxes. We found that ecosystem functions in the Arctic are closely linked with plant height and will be indicative of warming in the short term future becoming key factors in modelling ecosystem projections.
In a changing world, phytoplankton communities face a large variety of challenges including altered light regimes. These alterations are caused by more pronounced stratification due to rising temperatures, enhanced eutrophication, and browning of lakes. Community responses toward these effects can emerge as alterations in physiology, biomass, biochemical composition, or diversity. In this study, we addressed the combined effects of changes in light and nutrient conditions on community responses. In particular, we investigated how light intensity and variability under two nutrient conditions influence (1) fast responses such as adjustments in photosynthesis, (2) intermediate responses such as pigment adaptation and (3) slow responses such as changes in community biomass and species composition. Therefore, we exposed communities consisting of five phytoplankton species belonging to different taxonomic groups to two constant and two variable light intensity treatments combined with two levels of phosphorus supply. The tested phytoplankton communities exhibited increased fast reactions of photosynthetic processes to light variability and light intensity. The adjustment of their light harvesting mechanisms via community pigment composition was not affected by light intensity, variability, or nutrient supply. However, pigment specific effects of light intensity, light variability, and nutrient supply on the proportion of the respective pigments were detected. Biomass was positively affected by higher light intensity and nutrient concentrations while the direction of the effect of variability was modulated by light intensity. Light variability had a negative impact on biomass at low, but a positive impact at high light intensity. The effects on community composition were species specific. Generally, the proportion of green algae was higher under high light intensity, whereas the cyanobacterium performed better under low light conditions. In addition to that, the diatom and the cryptophyte performed better with high nutrient supply while the green algae as well as the cyanobacterium performed better at low nutrient conditions. This shows that light intensity, light variability, and nutrient supply interactively affect communities. Furthermore, the responses are highly species and pigment specific, thus to clarify the effects of climate change a deeper understanding of the effects of light variability and species interactions within communities is important.