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Resilience of Earthworm and Soil Microbial Communities to Agricultural Intensification and Climatic Extremes - A Case Study in the North German Lowlands

dc.contributor.advisorLeuschner, Christoph Prof. Dr.
dc.contributor.authorKlingenberg, Esther Odilie Felicia
dc.format.extentXXX Seitende
dc.titleResilience of Earthworm and Soil Microbial Communities to Agricultural Intensification and Climatic Extremes - A Case Study in the North German Lowlandsde
dc.contributor.refereeIsselstein, Johannes Prof. Dr.
dc.description.abstractengHigh demands for agricultural goods such as food, fiber and fodder and at the same time a decreasing farmland area result in an ongoing intensification of agricultural production. This is accompanied by high environmental costs such as pollution of soils and water bodies, biodiversity loss and greenhouse gas emissions. Since especially arable soils are a major nexus that links the fluxes of energy, carbon, water, and food, their conservation is a key challenge of the twenty-first century. A sustainable management of soils aims at maintaining its resilience, that is the soil’s capacity to absorb disturbances and continue to function in the established way. Soil organisms mediate core ecosystem processes, therefore focusing on them allows us to study the soil’s resilience. Since soil organism groups are known to not all respond in the same way to their environment, this dissertation focuses on two very different organism groups: on soil microbes and on earthworm communities. The long-term effect of intensive cropland management on soil organisms is studied in the North German Plains. They experienced a transition to intensive agricultural management half a century ago and currently rank among the most productive areas globally. In order to capture a picture across this area, four study sites with different natural landscape and cultivation history in the North German Plains were selected. To ensure consistent management in study site, three to four cropped fields of the same farm were sampled. The first objective of this dissertation was to assess to what extent intensive agricultural management as a permanent stress factor impacts earthworm and soil microbial communities, by comparing cropped fields with permanent field margins with same natural background as the cropped field. Our data indicate that intensive agricultural management simplifies soil organism communities in two ways – crop management and soil cultivation reduce the size and activity of soil microbial and earthworm populations. Furthermore, this treatment reduces the diversity of earthworm communities and levels out geographical variation. In contrast, permanent field margins in intensively managed farmlands preserve a greater biomass and diversity of earthworm populations. In addition to the long-term pressure of land-use intensification, cropland soils must buffer extra stressors such as droughts, as one example of climatic extremes whose frequency will increase due to global warming. Resilient arable soils exhibit a high resistance to stresses and/or a quick recovery to a pre-disturbed state after perturbation. Therefore, in the second part of this dissertation, earthworms and microbes were sampled in the year before, during and after the two years of the exceptional 2018/19 Central European drought. To disentangle the effect of drought and intensive management, soil organisms of arable fields were compared to soils of adjacent permanent, grassy field margins. We show that in the short-term, the drought reduced earthworm biomass and abundances in both field and margins. In margins, earthworms recovered quickly after the drought, however, in fields they did not recover during the study period. The drought reduced microbial biomass and activity in margins, but not in the fields. In fields, microbial biomass and activity were overall lower, but stayed at a constant level during and after the drought. This dissertation contributes to a better understanding of biotic resilience in intensively managed soils. It provides evidence that intensive farming in the North German Plains simplifies and the homogenizes soil microbial and earthworm communities in cropped fields. Margins, however, continue to host a greater diversity and abundance of earthworms and are therefore valuable for earthworm conservation efforts in farmlands. Intensive farming reduces the resilience of earthworms to cope with drought as an additional stress. Soil microbial populations in fields were smaller and less active than those in field margins, however, these communities were resistant to drought, presumably because intensive agricultural practices selected for stress tolerators. Thus, this dissertation underlines the importance of semi-natural habitats such as permanent field margins in intensive farmlands for the conservation of diverse and resilient soil communities. With the prospect of increasing frequency of drought events due to climate change, margins may serve as refuges for recolonization of cropped fields by soil organisms. So, with increasing attention on sustainable agriculture, the protection of existing, and creation of new, semi-natural habitats such as permanent field margins should become a priority. Future research should inform this further by assessing how quickly soil communities recover once taken out of management. Furthermore, more detailed analysis of microbial functional groups would allow to also determine the impact of intensive agriculture and drought on the community structure. In this way, we can contribute to a more nuanced understanding of soil decomposer communities that considers the different responses of organism groups to global change
dc.contributor.coRefereeMaraun, Mark Prof. Dr.
dc.contributor.thirdRefereeBergmeier, Erwin Prof. Dr.
dc.contributor.thirdRefereeSchuldt, Andreas Prof. Dr.
dc.contributor.thirdRefereeKamp, Johannes Prof. Dr.
dc.subject.engearthworms, soil microbes, biodiversity conservation, intensive agriculture, long-term soil fauna surveys, landscape simplification, soil ecology, ecological resilience, climate change, natural experimentde
dc.affiliation.instituteBiologische Fakultät für Biologie und Psychologiede
dc.subject.gokfullBiologie (PPN619462639)de
dc.notes.confirmationsentConfirmation sent 2023-05-16T19:45:01de

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