Project description A3

Scientific advisors
Prof. Dr. T. Tscharntke, Dr. C. Scherber

Project

Plant-insect interactions in a tree diversity gradient

In this project, we want to study how tree and herb layer diversity in deciduous forests influence arthropod communities and multitrophic interactions. We especially focus on insect communities on understory herbs. Differences in tree stand diversity might affect the vegetation structure of the herb layer, which in turn influences insect diversity. The rate of herbivory, seed predation, and the diversity of predators, herbivores and pollinators will be studied as well. We will test the hypotheses that tree and herb diversity increase herbivore diversity, but not herbivory and seed predation rates, and that the predator-prey ratio will be higher. Furthermore, we expect a greater diversity of flower visitors. Diversity is expected to show greater spatial and temporal turnover (beta diversity) with increasing habitat heterogeneity. In the course of this study, we will consider the relative importance of smaller (cluster consisting of 3 trees) and larger scales (the surrounding tree community).

Methods

• Pan traps to collect flower-visitors
• Insect suction sampling
• Screening of insects associated with individual plants
• Exposure of potted phytometer plants
• Pollination experiments (pollinator exclusion, hand pollination)
• Seed predation experiments (seed exposure in cages of varying mesh size)
• Vegetation relevés
• Fish-Eye-photographs