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The high diversity of insects has limited the volume of long-term community data with a high taxonomic resolution and considerable geographic replications, especially in forests. Therefore, trends and causes of changes are poorly understood. Here we analyse trends in species richness, abundance and biomass of nocturnal macro moths in three quantitative data sets collected over four decades in forests in southern Germany. Two local data sets, one from coppiced oak forests and one from high oak forests included 125K and 48K specimens from 559 and 532 species, respectively. A third regional data set, representing all forest types in the temperate zone of central Europe comprised 735K specimens from 848 species. Generalized additive mixed models revealed temporal declines in species richness (−38%), abundance (−53%) and biomass (−57%) at the regional scale. These were more pronounced in plant host specialists and in dark coloured species. In contrast, the local coppiced oak forests showed an increase, in species richness (+62%), while the high oak forests showed no clear trends. Left and right censoring as well as cross validation confirmed the robustness of the analyses, which led to four conclusions. First, the decline in insects appears in hyper diverse insect groups in forests and affects species richness, abundance and biomass. Second, the pronounced decline in host specialists suggests habitat loss as an important driver of the observed decline. Third, the more severe decline in dark species might be an indication of global warming as a potential driver. Fourth, the trends in coppiced oak forests indicate that maintaining complex and diverse forest ecosystems through active management may be a promising conservation strategy in order to counteract negative trends in biodiversity, alongside rewilding approaches.

Poster über denLOEWE-SchwerpunktNatur 4.0, präsentiert auf dem HeFDI Plenary 2020.

Die wissenschaftliche Ökologie untersucht Organismen in Wechselwirkung mit ihrer Umwelt. Um Vorhersa-gen ableiten zu können, wie ökologische Gemeinschaften in der Zukunft auf fortschreitende Umweltverände-rungen reagieren werden, ist es notwendig zu verstehen wie (I) Artengemeinschaften allgemein auf sich natür-lich ändernde Umweltbedingungen reagieren, (II) welche Merkmale für den Erfolg von Arten verantwortlich sind und (III) wie Merkmale den Erfolg einer Art in Abhängigkeit von gegebenen Umweltbedingungen beein-flussen. Nach einer generellen Einleitung in Kapitel 1, untersuche ich diese Fragestellungen in dieser Arbeit anhand von sieben Fachartikeln unterteilt in drei Kapiteln. Kapitel 2 untersucht die Reaktion von Artengemeinschaften auf sich ändernde Umweltbedingungen entlang natürlicher Gradienten in terrestrischen Waldökosystemen Hierbei zeige ich den starken Effekt lokaler Höhen-gradienten und der damit assoziierten Änderung der Umweltbedingungen auf die Alpha- und Beta-Diversität von Artengemeinschaften verschiedener Organismengruppen. Weiterhin analysiere ich wie Organismen ver-schiedener Taxa und trophischer Ebenen auf sich ändernde Waldstrukturparameter verschiedener Sukzessions-stadien reagieren. Schließlich untersuche ich wie klimatische, geographische und waldstrukturelle Bedingungen die Diversität von Arthropodengemeinschaften auf kontinentaler Skala beeinflussen. Die Ergebnisse zeigen starke Unterschiede in der Reaktion auf sich ändernde Umweltbedingungen zwischen taxonomischen und trophischen Gruppen auf, unterstreichen die Bedeutung des Artenumsatzes zwischen Sukzessionsstadien für den regionalen Artenpool und offenbaren das für bestimmte Artengemeinschaften, wie die in Pilzfruchtkör-pern lebenden Arthropoden, Klimabedingungen und der geographische Raum nur eine untergeordnete Rolle spielen. Im Kapitel 3 untersuche ich wie der Erfolg von Arten durch deren Merkmale beeinflusst werden. Dabei teste ich verschiedene Hypothesen die zur Erklärung der allgegenwärtigen Beziehung zwischen lokaler Verbreitung und mittlerer Abundanz aufgestellt wurden. Anhand phytophager Insekten demonstriere ich das die Habitat-verfügbarkeit in der Landschaft der wichtigste Faktor für die lokale Verbreitung und im Folgeschluss auch für die mittlere Abundanz der Tiere ist. Diese Beziehung wird weiterhin durch energetische Strategien der Arten moduliert. Kapitel 4 untersucht wie sich positive Effekte von Arteigenschaften auf den Erfolg der Arten verändern, wenn sich die Umweltbedingungen ändern. Zwei Studien untersuchen hier den Effekt von thermoregulatorisch rele-vanten Merkmalen auf die Verbreitung von Nachtfaltern entlang von Temperaturgradienten. Starke inter- und intrataxonische Unterschiede in den Merkmals-Umwelts-Beziehungen deuten hierbei darauf hin, dass derlei Beziehungen stark von der Skala und dem Kontext der Untersuchung abhängen. Die Identifikation relevanter Umweltgradienten, welche die Dynamik von Artengemeinschaften beeinflussen (I), die Bestimmung relevanter Arteigenschaften welche den Erfolg oder Misserfolg von Organismen bestim-men (II) sowie die Analyse der interaktiven Auswirkungen dieser Umweltbedingungen und Arteigenschaften auf das Vorkommen von Arten (III) wie sie in dieser Arbeit präsentiert wurde können uns helfen relevanten Treiber für bestimmte Arten und Artengemeinschaften in bestimmten raum-zeitlichen Kontexten zu identifi-zieren Darüber hinaus erweitern diese Erkenntnisse unser Wissen über die Prozesse, die die terrestrische Bio-diversität erzeugen und erhalten. Die Ergebnisse zeigen jedoch auch, dass es fraglich ist, ob es in naher Zu-kunft möglich ist, verlässliche und vor allem verallgemeinerbare Vorhersagen darüber zu generieren, wie zu-künftige Umweltveränderungen die terrestrischen Gemeinschaften insgesamt beeinflussen werden., Ecology as a science investigates organisms in interaction with their environment. This thesis aims at investi-gating how the environment and species’ traits as well as their interaction affect population and community structure and dynamics on varying spatial and temporal scales. In order to derive predictions of how ecological communities will respond to ongoing environmental change we need to understand (I) community responses to environmental gradients and their variation, (II) drivers of species’ performances and (III) how species’ traits affect species’ success in a particular environment. After a general introduction in chapter 1, I investigate these questions in seven articles subdivided in three chapters. Chapter 2 focusses on the response of ecological communities in terrestrial forest ecosystems to environmental conditions changing along natural gradients. Here, I show the strong effect of a local elevational gradient and the associated changes in environmental conditions on alpha and beta diversity of a multi-taxon community. Additionally, I analyze how organisms of varying taxonomic groups and trophic levels respond to temperate forest succession and the associated changes in forest structural parameters. Finally, I investigate how climatic conditions, geographic space and forest structure affect alpha and beta diversity of fungus-dwelling arthropod communities on a continental scale. The results reveal strong differences in the response to changing environ-mental conditions among taxonomic and trophic groups, underline the importance species turnover across successional stages for the regional species pool and reveal that climatic conditions and geographic space may play only minor roles in particular communities like those inhabiting fungus fruiting bodies. In chapter 3, I investigate how species’ performances are affected by species traits. Here, I test several pro-posed hypotheses aimed at explaining the ubiquitous relationship between local distribution and mean abun-dance in a causal statistical framework. For phytophagous insects I show that habitat availability is the most important driver of local distribution which in turn facilitates species’ mean abundances via population dynam-ic processes. This relationship is further modulated by species’ energy uptake and allocation strategies. Species that successfully compensate for higher energetic costs associated with beneficial morphological traits may reach higher local distributions and mean abundances. Chapter 4 aims at investigating how the effect of a particular trait on species’ success may change with chang-ing environmental conditions. Here, two studies investigate the effect of thermoregulatory relevant functional traits on the occurrence of moth along changing thermal conditions along spatial gradients. The results show that the relationship between species’ traits and species’ performances is highly context and scale dependent, as the presented studies revealed strong intra- and intertaxonic differences in the trait-environment relationships. Identifying important environmental gradients driving community dynamics (I), determining the drivers of species’ performances (II) and analyzing the interactive effect of environment and traits on species’ perfor-mances across scales (III) as pursued in this thesis helps us to identify the relevant drivers of species responses to environmental change on particular spatio-temporal scales for particular communities. Furthermore, these insights broaden our knowledge of the processes generating and maintaining terrestrial biodiversity. However, the results also show that it is debatable whether it is possible in the near future to generate reliable and more importantly generalizable predictions of how future environmental change will affect terrestrial communities as a whole.

Unmanned aerial systems (UAS) are cost-effective, flexible and offer a wide range of applications. If equipped with optical sensors, orthophotos with very high spatial resolution can be retrieved using photogrammetric processing. The use of these images in multi-temporal analysis and the combination with spatial data imposes high demands on their spatial accuracy. This georeferencing accuracy of UAS orthomosaics is generally expressed as the checkpoint error. However, the checkpoint error alone gives no information about the reproducibility of the photogrammetrical compilation of orthomosaics. This study optimizes the geolocation of UAS orthomosaics time series and evaluates their reproducibility. A correlation analysis of repeatedly computed orthomosaics with identical parameters revealed a reproducibility of 99% in a grassland and 75% in a forest area. Between time steps, the corresponding positional errors of digitized objects lie between 0.07 m in the grassland and 0.3 m in the forest canopy. The novel methods were integrated into a processing workflow to enhance the traceability and increase the quality of UAS remote sensing., This research was funded by the Hessian State Ministry for Higher Education, Research and the Arts, Germany, as part of the LOEWE priority project Nature 4.0—Sensing Biodiversity. The grassland study was funded by the Spanish Science Foundation FECYT-MINECO through the BIOGEI (GL2013- 49142-C2-1-R) and IMAGINE (CGL2017-85490-R) projects, and by the University of Lleida; and supported by a FI Fellowship to C.M.R. (2019 FI_B 01167) by the Catalan Government.