William R. Horwath, Soils & Biogeochemistry Program, Plant and Environmental Sciences Building, One Shields Avenue Davis, CA
The soil microbial biomass plays an important role in ecosystem function primarily through the regulation of nutrient cycles. In their search for energy to grow, the soil microbial biomass relies on nutrients in the plant litter and soil. Because of its competitive ability, the soil microbial biomass is often considered the source and sink of essential plant nutrients. The wide diversity and function of the soil microbial biomass exemplifies its role in a wide variety of processes, including parasitism, pathogenesis, and symbiosis. This wide functionality has made the study of soil microbial biomass problematic and often leads to misinterpretation of its importance in ecosystem function.