- FunBrowse

FunBrowse

Project description

Roe deer browsing differentially affects the performance of broadleaved tree species in temperate forests, leading in most cases to a decrease in tree species diversity already in the regeneration stage. However, why certain tree species are preferred by deer and others avoided is poorly understood. I want to examine whether browsing intensity of single tree species depends on tree species composition, i.e. species identity and species diversity, in the sapling stage. Also, deer browsing has rarely been related to plant functional traits yet, so I want to find out whether avoided species are simply better defended, either mechanically or chemically, or whether there even is induced defense in saplings in response to deer browsing. With my study I want to contribute to a better understanding of changes in tree species diversity in view of high deer populations.

Research questions

  1. a) Does deer selectivity and thus browsing intensity of certain tree species depend on the species' identity or on the diversity of neighboring tree species?
    b) Is browsing intensity further influenced by abiotic environmental variables, such as gradients in soil type, light availability, or by human disturbance?
  2. Can saplings' defense strategies (mechanical/chemical, constitutive/induced) be predicted from their functional traits?

Methods

Tree species identity and diversity effects on browsing intensity are analyzed using forest inventory data on regeneration and browsing signs from the Hainich forest (Biodiversity Exploratories, Hainich National Park). Other environmental variables (soil type, light availability, and disturbance) are included as additional explanatory variables. Using the above datasets I develop a statistical model in order to predict species abundances and sapling heights in the regeneration layer.

Defense strategies of tree saplings will be related to their functional traits via a field experiment using 24 tree species covering a broad gradient of morphological and chemical traits. The 24 chosen tree species are a subset of broadleaved species that are also growing next to the experiment in the Arboretum in Großpösna near Leipzig. This species overlap enables joint projects, e.g. for measuring a variety of traits. Browsing will be simulated by clipping the saplings apical buds and uppermost leaves, respectively, and applying deer saliva to the cut surface. After two weeks, subjacent buds or leaves, respectively, will be harvested and their chemical composition, especially plant secondary metabolites, will be analyzed (in cooperation with the MPI-CE) and compared to control saplings. Finally I want to relate the browsing induced response to the general morphological and chemical traits of the tree species to be able to predict the trees' ability to perceive, and respond to, deer herbivory.

Experiment in April 2014

This project is the PhD thesis of Bettina Ohse and is funded by a DBU scholarship.

last modified: 17.03.2015