PARENT SESSION
Oral Session 6: Herbivory I: Dynamics, Communities, and Photosynthesis.
Presiding: C Ivey
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room B 114.
Light regime and consumer control of autotrophic biomass.
Hillebrand, Helmut*,1, 1 Botanical Institute, Cologne, Germany
ABSTRACT- Light, nutrients and consumers can limit plant biomass. In comparison to nutrients, the interplay between light and herbivores on plant biomass has received less systematic attention. Here, I present results of a meta-analysis of factorial experiments reporting the biomass of periphyton in response to the removal of consumers (invertebrates and herbivorous fish) and the supply of light. Both the manipulation of grazers and light significantly altered periphyton biomass. Moreover, these two factors showed significant interactions, which were much larger than previously observed interactions between nutrients and grazers. Light enhancement increased grazing effects, whereas grazer presence reduced light effects to a degree where the overall light effect sizes became non-significant. Increased grazer efficiency at high light is presumably based on changes in community architecture. Consequently, grazer presence and light regime have important implications for important evolutionary traits such as plant height. Finally, I show how grazer and light effects depend on characteristics of the system such as nutrient supply, algal and grazer biomass, and light enhancement ratio.
Key words: grazer - periphyton interactions, top down - bottom up, light limitation, meta-analysis