92-02 Research exposition (monographs, survey articles)
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Increased bat hunting at polluted streams suggests chemical exposure rather than prey shortage
(2023)
Streams and their riparian areas are important habitats and foraging sites for bats feeding on emergent aquatic insects. Chemical pollutants entering freshwater streams from agricultural and wastewater sources have been shown to alter aquatic insect emergence, yet little is known about how this impacts insectivorous bats in riparian areas. In this study, we investigate the relationships between the presence of wastewater effluent, in-stream pesticide toxicity, the number of emergent and flying aquatic insects, and the activity and hunting behaviour of bats at 14 streams in southwestern Germany. Stream sites were located in riparian forests, sheltered from direct exposure to pollutants from agricultural and urban areas. We focused on three bat species associated with riparian areas: Myotis daubentonii, M. cf. brandtii, and Pipistrellus pipistrellus. We found that streams with higher pesticide toxicity and more frequent detection of wastewater also tended to be warmer and have higher nutrient and lower oxygen concentrations. We did not observe a reduction of insect emergence, bat activity or hunting rates in association with pesticide toxicity and wastewater detections. Instead, the activity and hunting rates of Myotis spp. were higher at more polluted sites. The observed increase in bat hunting at more polluted streams suggests that instead of reduced prey availability, chemical pollution at the levels measured in the present study could expose bats to pollutants transported from the stream by emergent aquatic insects.
Die steigende Verfügbarkeit von Smartphones und Tablet-PCs in der Schule bieten neue methodische und mediale Wege der Unterrichtsgestaltung, die zur Beurteilung der Lernwirksamkeit eine wissenschaftliche Betrachtung erfordern. Während zahlreiche Publikationen zu Augmented Reality (AR) im Bildungskontext existieren, fehlt es an einer differenzierten Betrachtung der Lernwirksamkeit AR-typischer Merkmale sowie breit angelegter Untersuchungsdesigns. Ziel dieser Arbeit ist es, die Lernwirksamkeit von AR in authentischen biologischen Unterrichtsszenarien multiperspektivisch zu betrachten. Zur Beurteilung der Lernwirksamkeit wurden Daten zu Lernzuwachs (LZ), Cognitive Load (CL), Nutzungserlebnis (UX), empfundener Lernunterstützung (ELU) sowie zur Immersion gemessen. Die Forschungsfragen beziehen sich auf den Einfluss der Art des Mediums, der Steuerung, des Triggers und der medialen Repräsentation auf die Lernwirksamkeit.
Die Untersuchungen wurden mithilfe eigens entwickelnder AR-Apps mit 769 Teilnehmenden aus rheinland-pfälzischen Gymnasien und zwei Universitäten durchgeführt. Neben dem Nachweis theoretischer Zusammenhänge der untersuchten Parameter mittels Strukturgleichungsmodellierung konnten mehrheitlich signifikante Unterschiede im LZ zugunsten von AR festgestellt werden. Darüber hinaus zeigten die Studien dieser Arbeit einen positiven Einfluss von AR auf den CL, sodass sich der Einsatz von AR nicht nachteilig auf die kognitive Belastung auswirkt. Neben des überdurchschnittlich bis exzellenten Abschneidens der AR-Apps im Benchmark-Vergleich (Vergleichsgruppe n = 20190 (Schrepp, 2019)), konnten positive Effekte der UX-Dimension Stimulation auf die Reduktion des lernhinderlichen Extraneous Cognitive Loads und die Steigerung des lernförderlichen Germane Cognitive Loads nachgewiesen werden. Hinsichtlich der ELU zeigten sich verschiedene mediale Präferenzen der Teilnehmenden, sodass durch die Verwendung von AR im Sinne eines wechselnden Medieneinsatzes die Bedürfnisse aller Lernenden abgedeckt werden kann. Weiterhin erreichten die Teilnehmenden die höchste der drei Ebenen der Immersion, sodass die Art des Triggers die 21 Immersionsfaktoren von Georgiou und Kyza (2017a) ergänzt.
Die Arbeit leistet auf Grundlage der Identifikation von AR-typischen Merkmalen einen Beitrag zum besseren Verständnis der lernwirksamen Potenziale von AR-basierten Lernumgebungen und zeigt darüber hinaus theoriebildende Implikationen zur Messung des CL auf. Ob sich mithilfe von AR der CL senken lässt, bedarf es Untersuchungen in Lernsettings, die einen hohen CL aufweisen. Weiterhin bietet der ARI-Fragebogen einen geeigneten Ausgangspunkt zur Erforschung AR-typischer Immersionsfaktoren. Trotzdem bedarf es weiterer Studien zur Validierung des ARI-Fragebogens und zur systematischen Untersuchung der Lernwirksamkeit von AR-typischen Merkmalen.
Human forest modification is among the largest global drivers of terrestrial degradation
of biodiversity, species interactions, and ecosystem functioning. One of the most
pertinent components, forest fragmentation, has a long history in ecological research
across the globe, particularly in lower latitudes. However, we still know little how
fragmentation shapes temperate ecosystems, irrespective of the ancient status quo of
European deforestation. Furthermore, its interaction with another pivotal component
of European forests, silvicultural management, are practically unexplored. Hence,
answering the question how anthropogenic modification of temperate forests affects
fundamental components of forest ecosystems is essential basic research that has
been neglected thus far. Most basal ecosystem elements are plants and their insect
herbivores, as they form the energetic basis of the tropic pyramid. Furthermore, their
respective biodiversity, functional traits, and the networks of interactions they
establish are key for a multitude of ecosystem functions, not least ecosystem stability.
Hence, the thesis at hand aimed to disentangle this complex system of
interdependencies of human impacts, biodiversity, species traits and inter-species
interactions.
The first step lay in understanding how woody plant assemblages are shaped by
human forest modification. For this purpose, field investigations in 57 plots in the
hyperfragmented cultural landscape of the Northern Palatinate highlands (SW
Germany) were conducted, censusing > 4,000 tree/shrub individuals from 34 species.
Use of novel, integrative indices for different types of land-use allowed an accurate
quantification of biotic responses. Intriguingly, woody tree/shrub communities reacted
strikingly positive to forest fragmentation, with increases in alpha and beta diversity,
as well as proliferation of heat/drought/light adapted pioneer species. Contrarily,
managed interior forests were homogenized/constrained in biodiversity, with
dominance of shade/cold adapted commercial tree species. Comparisons with recently
unmanaged stands (> 40 a) revealed first indications for nascent conversion to oldgrowth
conditions, with larger variability in light conditions and subsequent
community composition. Reactions to microclimatic conditions, the relationship
between associated species traits and the corresponding species pool, as well as
facilitative/constraining effects by foresters were discussed as underlying mechanisms.
Reactions of herbivore assemblages to forest fragmentation and the subsequent
changes in host plant communities were assessed by comprehensive sampling of >
1,000 live herbivores from 134 species in the forest understory. Diversity was –
similarly to plant communities - higher in fragmentation affected habitats, particularly
in edges of continuous control forests. Furthermore, average trophic specialization
showed an identical pattern. Mechanistically, benefits from microclimatic conditions,
host availability, as well as pronounced niche differentiation are deemed responsible.
While communities were heterogeneous, with no segregation across habitats, (smallforest fragments, edges, and interior of control forests), vegetation diversity, herbivore
diversity, as well as trophic specialization were identified to shape community
composition. This probably reflected a gradient from generalistic/species poor vs.
specialist/species rich herbivore assemblages.
Insect studies conducted in forest systems are doomed to incompleteness
without considering ‘the last biological frontier’, the tree canopies. To access their
biodiversity, relationship to edge effects, and their conservational value, the
arboricolous arthropod fauna of 24 beech (Fagus sylvatica) canopies was sampled via
insecticidal knockdown (‘fogging’). This resulted in an exhaustive collection of > 46,000
specimens from 24 major taxonomic/functional groups. Abundance distributions were
markedly negative exponential, indicating high abundance variability in tree crowns.
Individuals of six pertinent orders were identified to species level, returning > 3,100
individuals from 175 species and 52 families. This high diversity did marginally differ
across habitats, with slightly higher species richness in edge canopies. However,
communities in edge crowns were noticeably more heterogeneous than those in the
forest interior, possibly due to higher variability in environmental edge conditions. In
total, 49 species with protective value were identified, of which only one showed
habitat preferences (for near-natural interior forests). Among them, six species (all
beetles, Coleoptera) were classified as ‘priority species’ for conservation efforts. Hence,
beech canopies of the Northern Palatinate highlands can be considered strongholds of
insect biodiversity, incorporating many species of particular protective value.
The intricacy of plant-herbivore interaction networks and their relationship to
forest fragmentation is largely unexplored, particularly in Central Europe. Illumination
of this matter is all the more important, as ecological networks are highly relevant for
ecosystem stability, particularly in the face of additional anthropogenic disturbances,
such as climate change. Hence, plant-herbivore interaction networks (PHNs) were
constructed from woody plants and their associated herbivores, sampled alive in the
understory. Herbivory verification was achieved using no-choice-feeding assays, as well
as literature references. In total, networks across small forest fragments, edges, and
the forest interior consisted of 696 interactions. Network complexity and trophic niche
redundancy were compared across habitats using a rarefaction-like resampling
procedure. PHNs in fragmentation affected forest habitats were significantly more
complex, as well as more redundant in their realized niches, despite being composed of
relatively more specialist species. Furthermore, network robustness to climate change
was quantified utilizing four different scenarios for climate change susceptibility of
involved plants. In this procedure, remaining herbivores in the network were measured
upon successive loss of their host plant species. Consistently, PHNs in edges (and to a
smaller degree in small fragments) withstood primary extinction of plant species
longer, making them more robust. This was attributed to the high prevalence of
heat/drought-adapted species, as well as to beneficial effects of network topography
(complexity and redundancy). Consequently, strong correlative relationships were
found between realized niche redundancy and climate change robustness of PHNs.
This was both the first time that biologically realistic extinctions (instead of e.g.random extinctions) were used to measure network robustness, and that topographical
network parameters were identified as potential indicators for network robustness
against climate change.
In synthesis, in the light of global biotic degradation due to human forest
modification, the necessity to differentiate must be claimed. Ecosystems react
differently to anthropogenic disturbances, and it seems the particular features present
in Central European forests (ancient deforestation, extensive management, and, most
importantly, high richness in open-forest plant species) cause partly opposed patterns
to other biomes. Lenient microclimates and diverse plant communities facilitate
equally diverse herbivore assemblages, and hence complex and robust networks,
opposed to the forest interior. Therefore, in the reality of extensively used cultural
landscapes, fragmentation affected forest ecosystems, particularly forest edges, can be
perceived as reservoir for biodiversity, and ecosystem functionality. Nevertheless, as
practically all forest habitats considered in this thesis are under human cultivation,
recommendations for ecological enhancement of all forest habitats are discussed.