Dissertation Research: The Effect of Plant Community Composition and Land-use Change on Soil Microbial Community Composition and Function

Stanford University, Stanford CA

Investigators

Abstract

PROJECT SUMMARY Land-use change and alterations of plant diversity and composition have been shown to influence ecosystem processes. Until recently, however, there has been little evaluation of the role of microbial community changes in mediating process change. Shifts in land-use and plant diversity may alter the composition, and thus collective physiology, of soil microbial communities, leading to differences in process rates. To understand more fully the factors that influence microbial communities and their functioning, our research addresses the following questions: 1) Does plant diversity and/or land-use influence soil microbial community composition? 2) Do these changes in microbial composition influence nutrient cycling rates? We are addressing these questions using an experiment in Costa Rica that manipulates plant community composition and diversity as well as a set of land-use sites, including forest and pasture. To address the first question, we are examining microbial community composition using phospholipid fatty acid analysis (PLFA) and terminal restriction fragment length polymorphisms (T-RFLP). PLFA data suggest that microbial communities differ significantly across plant diversity and land- use gradients. We request funds to proceed to the crucial second question and test, using controlled laboratory experiments, whether soils with distinct microbial communities differ in two critical ecosystem functions: nitrification and litter decomposition.