Open Access

The biotic release of nitric oxide (NO), a greenhouse gas, into the atmosphere contributes to climate change. In plants, NO plays a significant role in metabolic and signaling processes. However, little attention has been paid to the plant-borne portion of global NO emissions. Owing to the growing significance of global flooding events caused by climate change, the extent of plant NO emissions has been assessed under low-oxygen conditions for the roots of intact plants. Each examined plant species (tomato, tobacco, and barley) exhibited NO emissions in a highly oxygen-dependent manner. The transfer of data obtained under laboratory conditions to the global area of farmland was used to estimate possible plant NO contribution to greenhouse gas budgets. Plant-derived and stress-induced NO emissions were estimated to account for the equivalent of 1 to 9% of global annual NO emissions from agricultural land. Because several stressors induce NO formation in plants, the actual impact may be even higher.

Wood is a sustainable natural resource and an important global commodity. According to the ‘moon wood theory’, the properties of wood, including its growth and water content, are believed to oscillate with the lunar cycle. Despite contradicting our current understanding of plant functioning, this theory is commonly exploited for marketing wooden products. To examine the moon wood theory, we applied a wavelet power transformation to series of 2,000,000 hourly stem radius records from dendrometers. We separated the influence of 74 consecutive lunar cycles and meteorological conditions on the stem variation of 62 trees and six species. We show that the dynamics of stem radius consist of overlapping oscillations with periods of 1 day, 6 months, and 1 year. These oscillations in stem dimensions were tightly coupled to oscillations in the series of air temperature and vapour pressure deficit. By contrast, we revealed no imprint of the lunar cycle on the stem radius variation of any species. We call for scepticism towards the moon wood theory, at least as far as the stem water content and radial growth are concerned. We foresee that similar studies employing robust scientific approaches will be increasingly needed in the future to cope with misleading concepts.

Climate warming advances the onset of tree growth in spring, but above- and belowground phenology are not always synchronized. These differences in growth responses may result from differences in root and bud dormancy dynamics, but root dormancy is largely unexplored. We measured dormancy in roots and leaf buds of Fagus sylvatica and Populus nigra by quantifying the warming sum required to initiate above- and belowground growth in October, January and February. We furthermore carried out seven experiments, manipulating only the soil and not air temperature before or during tree leaf-out to evaluate the potential of warmer roots to influence budburst timing using seedlings and adult trees of F. sylvatica and seedlings of Betula pendula. Root dormancy was virtually absent in comparison with the much deeper winter bud dormancy. Roots were able to start growing immediately as soils were warmed during the winter. Interestingly, higher soil temperature advanced budburst across all experiments, with soil temperature possibly accounting for c. 44% of the effect of air temperature in advancing aboveground spring phenology per growing degree hour. Therefore, differences in root and bud dormancy dynamics, together with their interaction, likely explain the nonsynchronized above- and belowground plant growth responses to climate warming.

Sacred areas are the oldest form of habitat protection and contribute to biodiversity conservation. Freshwater swamps are tree-covered wetlands, marshy areas with a high-water table and slow runoff occurring on flat terrain around streams in climax evergreen forests. While sacred groves have received considerable scholarly attention, little is known about sacred freshwater swamps. Sacred swamps are dedicated to worship deities through long-term commitment and traditional laws and practices. With studies conducted in one of the global biodiversity hotspots, the Central Western Ghats, India, this thesis aims to advance our knowledge of the socio-ecological phenomenon of sacred swamps. It is based on a multi-layered approach that analyses the distinct physical, ecological as well as socio-cultural aspects of sacred freshwater swamps and then uses the results to explore in a participatory manner the role of these swamps for nature and livelihood protection. The thesis tests the conjecture that sacred swamps have physical features that distinguish them from non-sacred swamps. The thesis further compares plant species composition, floristic structure, diversity, and the occurrence of amphibians, odonata and birds between sacred and non-sacred swamps. It presents the rituals and rules that define the socio-cultural features of sacred swamps, and addresses the ecological, socio-cultural and economic valuation of the swamps with special attention to the overlaps and differences of valuation among different stakeholder groups living with and around the swamps. In a final step of the study, the results of these physical, ecological and socio-cultural explorations were presented at four workshops, where the stakeholder groups were invited to participate in a visioning exercise that identified the role of sacred swamps for nature conservation and livelihood protection. 110 swamps in the district of Uttara Kannada, Central Western Ghats, were exploratively mapped after which ten sacred and ten non sacred swamps with similar sizes were selected for more intensive study. The systematic comparison showed that sacred swamps differ distinctly from non-sacred swamps: a) physically: sacred swamps are significantly smaller, shorter in length and more compact than non-sacred swamps, b) ecologically: the biodiversity and canopy cover of sacred swamps is significantly higher than of non-sacred swamps, and c) socially: their distance from tar roads, mud roads, commercial orchards and human settlements is significantly smaller than that of non-sacred swamps. The sacred swamps also have a higher surrounding population density than non-sacred swamps. This shows that preferentially swamps close to human infrastructure have been declared as sacred, probably to regulate provisioning of ecosystem services. Our research revealed that more species occur in sacred than in non-sacred swamps (122 tree species from 99 genera and 58 families in the sacred against 83 species from 72 genera and 47 families in the non-sacred swamps). Stem density and average basal area are higher in the sacred swamps and sacred swamps have slightly more endemic plant species (28%) when compared to non-sacred swamps (23%). Significant differences exist in the Shannon index of diversity (species diversity) of amphibians (H=2.749) and birds (H=3.097) between sacred and non-sacred swamps, with t (194) = 3.929, p=0.001 and t (37) = 2.140, p= 0.039, respectively. Also, the number of individuals of critically endangered amphibian species from the IUCN Red list (Nyctibatrachus dattatreyaensis, Pseudophilautus amboli and Micrixalus kottigeharensis) is higher in the sacred swamps. While we find a variety of deities associated with the sacred swamps, the practices associated with sacred swamp status and management are essentially the same across belief groups and limit harvest and resource extraction in the sacred swamp areas. Extra-ordinary rituals around annual festivals (re)-establish the shared status of the sacred place and provide meaning and effect to everyday rules of sacred swamp management via a self-regulating, invisible fence. We identified six major value categories (hydrological, religious, biodiversity, recreational, utilitarian and social), and labelled them in such a way that participants could understand and score them. Results of the scoring exercise showed substantial differences between the scores assigned to the values associated with sacred swamps by the various stakeholders. Across all stakeholder groups, the hydrological value of sacred swamps was highly appreciated. The visioning workshops allowed linking results on physical, ecological and socio-cultural aspects of swamps to the development of location-specific, desirable suggestions drawn on traditional knowledge of species and landscapes. The approach promoted development of action plans in response to the challenges that tropical forests and freshwater swamps are facing. The workshops also showed limits of the approach, since not all stakeholder groups belong to the same community of faith. This suggests that faith-based governance of sacred swamps can benefit from the emphasis on faith-independent, ecological, socio-cultural and economic values to foster a dialogue around sacred swamps and their importance for livelihoods and nature conservation.

Aim Climate change challenges temperate forest trees by increasingly irregular precipitation and rising temperatures. Due to long generation cycles, trees cannot quickly adapt genetically. Hence, the persistence of tree populations in the face of ongoing climate change depends largely on phenotypic variation, that is the capability of a genotype to express variable phenotypes under different environmental conditions, known as plasticity. We aimed to quantify phenotypic variation of central Europe's naturally dominant forest tree across various intraspecific scales (individuals, mother trees (families), populations) to evaluate its potential to respond to changing climatic conditions. Location Europe. Time Period 2016–2019. Major Taxa Studied European beech (Fagus sylvatica L.). Methods We conducted a fully reciprocal transplantation experiment with more than 9000 beech seeds from seven populations across a Europe-wide gradient. We compared morphological (Specific Leaf Area), phenological (leaf unfolding) and fitness-related (growth, survival) traits across various biological scales: within single mother trees, within populations and across different populations under the contrasting climates of the translocation sites. Results The experiment revealed significant phenotypic variation within the offspring of each mother tree, regardless of geographic origin. Initially, seedling height growth varied among mother trees and populations, likely due to maternal effects. However, the growth performance successively aligned after the first year. In summary, we observed a consistent growth response in different beech populations to diverse environments after initial maternal effects. Main Conclusions The study strikingly demonstrates the importance of considering intraspecific variation. Given the surprisingly broad spectrum of phenotypes each mother tree holds within its juvenile offspring, we conclude that Fagus sylvatica might have the potential for medium-term population persistence in face of climate change, provided that this pattern persists into later life stages. Hence, we also suggest further investigating the inclusion of passive adaptation and natural dynamics in the adaptive management of forests.