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    Animal-Mediated Ecosystem Process Rates in Forests and Grasslands are Affected by Climatic Conditions and Land-Use Intensity
    (Springer, 2021) Ambarli, Didem; Simons, Nadja K.; Wehner, Katja; Kaemper, Wiebke; Gossner, Martin M.; Nauss, Thomas; Bluethgen, Nico
    Decomposition, vegetation regeneration, and biological control are essential ecosystem functions, and animals are involved in the underlying processes, such as dung removal, seed removal, herbivory, and predation. Despite evidence for declines of animal diversity and abundance due to climate change and land-use intensification, we poorly understand how animal-mediated processes respond to these global change drivers. We experimentally measured rates of four ecosystem processes in 134 grassland and 149 forest plots in Germany and tested their response to climatic conditions and land-use intensity, that is, grazing, mowing, and fertilization in grasslands and the proportion of harvested wood, non-natural trees, and deadwood origin in forests. For both climate and land use, we distinguished between short-term effects during the survey period and medium-term effects during the preceding years. Forests had significantly higher process rates than grasslands. In grasslands, the climatic effects on the process rates were similar or stronger than land-use effects, except for predation; land-use intensity negatively affected several process rates. In forests, the land-use effects were more pronounced than the climatic effects on all processes except for predation. The proportion of non-natural trees had the greatest impact on the process rates in forests. The proportion of harvested wood had negative effects, whereas the proportion of anthropogenic deadwood had positive effects on some processes. The effects of climatic conditions and land-use intensity on process rates mirror climatic and habitat effects on animal abundance, activity, and resource quality. Our study demonstrates that land-use changes and interventions affecting climatic conditions will have substantial impacts on animal-mediated ecosystem processes.
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    Arthropod decline in grasslands and forests is associated with landscape-level drivers
    (Nature Publishing Group, 2019) Seibold, Sebastian; Gossner, Martin M.; Simons, Nadja K.; Blüthgen, Nico; Müller, Jörg; Ambarlı, Didem; Wöllauer, Stephan
    Recent reports of local extinctions of arthropod species(1), and of massive declines in arthropod biomass(2), point to land-use intensification as a major driver of decreasing biodiversity. However, to our knowledge, there are no multisite time series of arthropod occurrences across gradients of land-use intensity with which to confirm causal relationships. Moreover, it remains unclear which land-use types and arthropod groups are affected, and whether the observed declines in biomass and diversity are linked to one another. Here we analyse data from more than 1 million individual arthropods (about 2,700 species), from standardized inventories taken between 2008 and 2017 at 150 grassland and 140 forest sites in 3 regions of Germany. Overall gamma diversity in grasslands and forests decreased over time, indicating loss of species across sites and regions. In annually sampled grasslands, biomass, abundance and number of species declined by 67%, 78% and 34%, respectively. The decline was consistent across trophic levels and mainly affected rare species; its magnitude was independent of local land-use intensity. However, sites embedded in landscapes with a higher cover of agricultural land showed a stronger temporal decline. In 30 forest sites with annual inventories, biomass and species number-but not abundance-decreased by 41% and 36%, respectively. This was supported by analyses of all forest sites sampled in three-year intervals. The decline affected rare and abundant species, and trends differed across trophic levels. Our results show that there are widespread declines in arthropod biomass, abundance and the number of species across trophic levels. Arthropod declines in forests demonstrate that loss is not restricted to open habitats. Our results suggest that major drivers of arthropod decline act at larger spatial scales, and are (at least for grasslands) associated with agriculture at the landscape level. This implies that policies need to address the landscape scale to mitigate the negative effects of land-use practices.
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    Drivers of community assembly change during succession in wood-decomposing beetle communities
    (Wiley, 2022) Seibold, Sebastian; Weisser, Wolfgang W.; Ambarlı, Didem; Gossner, Martin M.; Mori, Akira S.; Cadotte, Marc W.; Hagge, Jonas
    The patterns of successional change of decomposer communities is unique in that resource availability predictably decreases as decomposition proceeds. Saproxylic (i.e. deadwood-dependent) beetles are a highly diverse and functionally important decomposer group, and their community composition is affected by both deadwood characteristics and other environmental factors. Understanding how communities change with faunal succession through the decomposition process is important as this process influences terrestrial carbon dynamics. Here, we evaluate how beta-diversity of saproxylic beetle communities change with succession, as well as the effects of different major drivers of beta-diversity, such as deadwood tree species, spatial distance between locations, climate and forest structure. We studied spatial beta-diversity (i.e. dissimilarity of species composition between deadwood logs in the same year) of saproxylic beetle communities over 8 years of wood decomposition. Our study included 379 experimental deadwood logs comprising 13 different tree species in 30 forest stands in Germany. We hypothesized that the effects of tree species dissimilarity, measured by phylogenetic distance, and climate on beta-diversity decrease over time, while the effects of spatial distance between logs and forest structure increase. Observed beta-diversity of saproxylic beetle communities increased over time, whereas standardized effects sizes (SES; based on null models) of beta-diversity decreased indicating higher beta-diversity than expected during early years. Beta-diversity increased with increasing phylogenetic distance between tree species and spatial distance among regions, and to a lesser extent with spatial distance within regions and differences in climate and forest structure. Whereas effects of space, climate and forest structure were constant over time, the effect of phylogenetic distance decreased. Our results show that the strength of the different drivers of saproxylic beetle community beta-diversity changes along deadwood succession. Beta-diversity of early decay communities was strongly associated with differences among tree species. Although this effect decreased over time, beta-diversity remained high throughout succession. Possible explanations for this pattern include differences in decomposition rates and fungal communities between logs or the priority effect of early successional communities. Our results suggest that saproxylic beetle diversity can be enhanced by promoting forests with diverse tree communities and structures.
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    Insights from regional and short-term biodiversity monitoring datasets are valuable: a reply to Daskalova et al. 2021
    (Wiley, 2021) Seibold, Sebastian; Hothorn, Torsten; Gossner, Martin M.; Simons, Nadja K.; Bluthgen, Nico; Muller, Jorg; Penone, Caterina
    Reports of major losses in insect biodiversity have stimulated an increasing interest in temporal population changes. Existing datasets are often limited to a small number of study sites, few points in time, a narrow range of land-use intensities and only some taxonomic groups, or they lack standardised sampling. While new monitoring programs have been initiated, they still cover rather short time periods. Daskalova et al. 2021 (Insect Conservation and Diversity, 14, 1-18) argue that temporal trends of insect populations derived from short time series are biased towards extreme trends, while their own analysis of an assembly of shorter- and longer-term time series does not support an overall insect decline. With respect to the results of Seibold et al. 2019 (Nature, 574, 671-674) based on a 10-year multi-site time series, they claim that the analysis suffers from not accounting for temporal pseudoreplication. Here, we explain why the criticism of missing statistical rigour in the analysis of Seibold et al. (2019) is not warranted. Models that include 'year' as random effect, as suggested by Daskalova et al. (2021), fail to detect non-linear trends and assume that consecutive years are independent samples which is questionable for insect time-series data. We agree with Daskalova et al. (2021) that the assembly and analysis of larger datasets is urgently needed, but it will take time until such datasets are available. Thus, short-term datasets are highly valuable, should be extended and analysed continually to provide a more detailed understanding of insect population changes under the influence of global change, and to trigger immediate conservation actions.
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    Present and historical landscape structure shapes current species richness in Central European grasslands
    (Springer, 2022) Scherreiks, Pascal; Gossner, Martin M.; Ayasse, Manfred; Bluethgen, Nico; Fischer, Markus; Klaus, Valentin H.; Kleinebecker, Till
    Context Current diversity and species composition of ecological communities can often not exclusively be explained by present land use and landscape structure. Historical land use may have considerably influenced ecosystems and their properties for decades and centuries. Objectives We analysed the effects of present and historical landscape structure on plant and arthropod species richness in temperate grasslands, using data from comprehensive plant and arthropod assessments across three regions in Germany and maps of current and historical land cover from three time periods between 1820 and 2016. Methods We calculated local, grassland class and landscape scale metrics for 150 grassland plots. Class and landscape scale metrics were calculated in buffer zones of 100 to 2000 m around the plots. We considered effects on total species richness as well as on the richness of species subsets determined by taxonomy and functional traits related to habitat use, dispersal and feeding. Results Overall, models containing a combination of present and historical landscape metrics showed the best fit for several functional groups. Comparing three historical time periods, data from the 1820/50s was among the most frequent significant time periods in our models (29.7% of all significant variables). Conclusions Our results suggest that the historical landscape structure is an important predictor of current species richness across different taxa and functional groups. This needs to be considered to better identify priority sites for conservation and to design biodiversity-friendly land use practices that will affect landscape structure in the future.