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B8) Effect of large herbivores

The effects of large herbivores on multiple levels of biodiversity in European mixed montane forests

Ilse Storch
Doctoral researcher: Sebastian Schwegmann (since 2019)

University of Freiburg, Faculty of Environment and Natural Resources, Chair of Wildlife Ecology and Management


Background

Deer are the dominant herbivore taxa in the northern hemisphere and considered keystone species. Deer affect vegetation, soil and cooccurring faunal taxa through browsing, zoochory, trampling and defecation as well as fostering associated parasites, coprophages and necrophages.

From a forestry perspective deer are often seen as pest species inhibiting natural tree succession through browsing. Thus, past research often focused on assessing the effects of deer on young trees, which were often used inadequately as a proxy for biodiversity in general. Frequently exclosure experiments compared high deer densities with the absence of deer, to show that deer reduce biodiversity, an approach that does not fully meet the complexity of the interaction of deer and their ecosystem. 

 

Research questions

  • What factors influence relative local abundance of roe deer in the ConFoBi study area?
  • How is local deer abundance related to diversity and community composition of vegetation?
  • What are the co-occurrence patterns of roe deer and other faunal taxa studied in ConFoBi (birds, bats, insects) in the southern Black forest?
  • How are relative deer abundance and browsing intensity on forest succession related and what other factors shape this relationship?

 

Approach, methods and linkages

This study aims to investigate the interactions of roe deer (Capreolus capreolus) with their ecosystem more holistically than prior studies, using gradual measures of relative abundance without fencing along with data on multiple ecosystem elements and other influencing factors (vegetation, soil, insects, birds, bats, landscape pattern, forest structure, hunting pressure). As a first step driving factors of spatial variation in local deer abundance will be assessed. Secondly, relations between roe deer and ground vegetation will be investigated, followed by exploratory research on cooccurrence patterns of roe deer with other faunal taxa that might indicate direct or indirect interactions. The last part will focus on factors next to deer population density influencing browsing pressure.

Camera traps and pellet-group sampling will be applied on all 135 research plots, to acquire two relative abundance measures of roe deer on different spatial scales. This will be combined with an equally extensive browsing survey and a germination experiment from roe deer faecal pellets. Usage of data on vegetation and forest structure (A1, A2 & B2) is of key importance for this project. Datasets on faunistic groups will be used (B3-B6). The germination experiment is a collaboration with B2.