• Energy Research

Summary Agri‐environment schemes promote organic farming in an attempt to reduce the negative effects of agricultural intensification on farmland biodiversity and ecosystem services such as pollination. Farming system, landscape context and regional differences may all influence biodiversity, but their relative impact and possible interactions have been little explored. The study was performed in three regions (150 km apart, 400–500 km2 per region) differing in land use intensity. Within each region, seven pairs of conventionally and organically cultivated wheat fields (mean size 4 ha, 42 study fields) were selected to encompass a gradient from heterogeneous to homogeneous landscapes within a 1‐km radius around each field. Farming system had the greatest influence on biodiversity. Higher bee diversity, flower cover and diversity of flowering plants were recorded in organic compared with conventional fields. Bee diversity was related both to flower cover and diversity of flowering plants, suggesting plant‐mediated effects of the farming system. Differences in bee diversity between organic and conventional fields increased with the proportion of arable crops in the surrounding landscape, indicating that processes at the landscape level modified the effectiveness of organic farming in promoting biodiversity. Similar patterns for flower cover and diversity of flowering plants suggested that landscape effects on bee diversity were mainly resource‐mediated. After statistically removing the variance explained by flower parameters, residual bee diversity increased with increasing landscape heterogeneity. Bee diversity differed between the three regions, but the effects of farming systems and landscape context were independent of regional differences. Synthesis and applications. Bee diversity in wheat fields was mainly influenced by farming system, but an understanding of local bee diversity needs to incorporate both landscape and regional perspectives. The consistency of the results in three regions provides a reliable basis for management decisions. Agri‐environment schemes that promote organic farming in homogeneous landscapes where there are few remaining flower‐rich habitats could have the highest relative impact. However, while organic farming could help to sustain pollination services by generalist bees in agricultural landscapes, other measures are required to conserve more specialized bee species in semi‐natural habitats.

Climatic extreme events can cause the shift or disruption of plant-insect interactions due to altered plant quality, e.g. leaf carbon to nitrogen ratios, and phenology. However, the response of plant-herbivore interactions to extreme events and climatic gradients has been rarely studied, although climatic extremes will increase in frequency and intensity in the future and insect herbivores represent a highly diverse and functionally important group. We set up a replicated climate change experiment along elevational gradients in the German Alps to study the responses of three plant guilds and their herbivory by insects to extreme events (extreme drought, advanced and delayed snowmelt) versus control plots under different climatic conditions on 15 grassland sites. Our results indicate that elevational shifts in CN (carbon to nitrogen) ratios and herbivory depend on plant guild and season. CN ratios increased with altitude for grasses, but decreased for legumes and other forbs. In contrast to our hypotheses, extreme climatic events did not significantly affect CN ratios and herbivory. Thus, our study indicates that nutritional quality of plants and antagonistic interactions with insect herbivores are robust against seasonal climatic extremes. Across the three functional plant guilds, herbivory increased with nitrogen concentrations. Further, increased CN ratios indicate a reduction in nutritional plant quality with advancing season. Although our results revealed no direct effects of extreme climatic events, the opposing responses of plant guilds along elevation imply that competitive interactions within plant communities might change under future climates, with unknown consequences for plant-herbivore interactions and plant community composition.

Cold waves crossing the Amazon rainforest are an extraordinary phenomenon likely to be affected by climate change. We here describe an extensive cold wave that occurred in June 2023 in Amazonian–Andean forests and compare environmental temperatures to experimentally measured thermal tolerances and their impact on lowland animal communities (insects and wild mammals). While we found strong reductions in activity abundance of all animal groups under the cold wave, tropical lowland animals showed thermal tolerance limits below the lowest environmental temperatures measured during the cold wave. While mammal activity and the biomass of most insects recovered over the next season, dung beetle biomass remained low. A quarter of all insects showed very small thermal safety margins (0.62 °C) with respect to the recorded minimum temperature of 10.5 °C, suggesting that an increased intensity of cold waves in the future could imperil cold-sensitive taxa of Amazonian animal communities.

Climate and land use are major determinants of biodiversity, and declines in species richness in cold and human exploited landscapes can be caused by lower rates of biotic interactions. Deadwood fungi and bacteria interact strongly with their hosts due to long‐lasting evolutionary trajectories. However, how rates of biotic interactions (specialization) change with temperature and land‐use intensity are unknown for both microbial groups. We hypothesize a decrease in species richness and specialization of communities with decreasing temperature and increasing land use intensity while controlling for precipitation. We used a full‐factorial nested design to disentangle land use at habitat and landscape scale and temperature spanning an area of 300 × 300 km in Germany. We exposed four deadwood objects representing the main tree species in Central Europe (beech, oak, spruce, pine) in 175 study plots. Overall, we found that fungal and bacterial richness, community composition and specialization were weakly related to temperature and land use. Fungal richness was slightly higher in near‐natural than in urban landscapes. Bacterial richness was positively associated with mean annual temperature, negatively associated with local temperature and highest in grassland habitats. Bacterial richness was positively related to the covariate mean annual precipitation. We found strong effects of host‐tree identity on species richness and community composition. A generally high level of fungal host‐tree specialization might explain the weak response to temperature and land use. Effects of host‐tree identity and specialization were more pronounced in fungi. We suggest that host tree changes caused by land use and climate change will be more important for fungal communities, while changes in climate will affect bacterial communities more directly. Contrasting responses of the two taxonomic groups suggest a reorganization of deadwood microbial communities, which might have further consequences on diversity and decomposition in the Anthropocene.

AbstractAimSpecies differ in their degree of specialization when interacting with other species, with significant consequences for the function and robustness of ecosystems. In order to better estimate such consequences, we need to improve our understanding of the spatial patterns and drivers of specialization in interaction networks.MethodsHere, we used the extensive environmental gradient of Mt. Kilimanjaro (Tanzania, East Africa) to study patterns and drivers of specialization, and robustness of plant–pollinator interactions against simulated species extinction with standardized sampling methods. We studied specialization, network robustness and other network indices of 67 quantitative plant–pollinator networks consisting of 268 observational hours and 4,380 plant–pollinator interactions along a 3.4 km elevational gradient. Using path analysis, we tested whether resource availability, pollinator richness, visitation rates, temperature, and/or area explain average specialization in pollinator communities. We further linked pollinator specialization to different pollinator taxa, and species traits, that is, proboscis length, body size, and species elevational ranges.ResultsWe found that specialization decreased with increasing elevation at different levels of biological organization. Among all variables, mean annual temperature was the best predictor of average specialization in pollinator communities. Specialization differed between pollinator taxa, but was not related to pollinator traits. Network robustness against simulated species extinctions of both plants and pollinators was lowest in the most specialized interaction networks, that is, in the lowlands.ConclusionsOur study uncovers patterns in plant–pollinator specialization along elevational gradients. Mean annual temperature was closely linked to pollinator specialization. Energetic constraints, caused by short activity timeframes in cold highlands, may force ectothermic species to broaden their dietary spectrum. Alternatively or in addition, accelerated evolutionary rates might facilitate the establishment of specialization under warm climates. Despite the mechanisms behind the patterns have yet to be fully resolved, our data suggest that temperature shifts in the course of climate change may destabilize pollination networks by affecting network architecture.

This data set contains plot data on climate, land area, land use, primary productivity, conservation and domestic mammals for explaining the diversity of wild mammals on Mount Kilimanjaro, Tanzania. This data set includes data on mammal diversity from 66 study plots along elevation and land use gradients on Mount Kilimanjaro. Supplement to: Gebert, Friederike; Njovu, Henry K; Treydte, Anna; Steffan-Dewenter, Ingolf; Peters, Marcell Karl (2019): Primary productivity and habitat protection predict elevational species richness and community biomass of large mammals on Mt. Kilimanjaro. Journal of Animal Ecology This data set contains plot data on climate, land area, land use, primary productivity, conservation and domestic mammals for explaining the diversity of wild mammals on Mount Kilimanjaro.

Biodiversity conservation measures and biological processes often do not match in scale. The EU funded project SCALES (Securing the Conservation of biodiversity across Administrative Levels and spatial, temporal, and Ecological Scales) is intended to solve this challenge. SCALES analyses how selected pressures (climate change, habitat loss, fragmentation, disturbance), their drivers, and their impacts on biodiversity change with spatial and temporal scale. The project develops methods for a better understanding of scaling properties of biological processes from the genetic level to populations, communities, and ecosystem functions. SCALES also seeks ways to integrate the issue of scale into policy, decision-making, and biodiversity management, focusing on networks of protected areas, regional connectivity, and biodiversity monitoring.