PARENT SESSION
Oral Session 3: Biogeochemistry I: Litter and Decomposition.
Presiding: J Dilustro
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room A 107.

Dissolved organic carbon decomposition and the soil microbial community: Are molecular techniques the key to the black box?

Cleveland, Cory ^*,1, Nemergut, Diana², Townsend, Alan ¹, Schmidt, Steve², ¹ INSTAAR, Boulder, CO, USA² Department of Ecology & Evolutionary Biology, Boulder, CO

ABSTRACT- Traditionally, soil biogeochemical research has emphasized understanding specific process rates and controls that together help define ecosystem function. Until recently, methodological limitations have hindered progress toward understanding the importance of microbial community composition in regulating soil biogeochemical processes, including carbon and nutrient cycling. For example, virtually nothing is known about the role of specific microorganisms in regulating the decomposition of dissolved organic carbon (DOC) entering the soil (as litter leachate) following precipitation events in forested ecosystems. We constructed small-subunit ribosomal DNA (SSU rDNA) clone libraries from soil bacterial DNA extracted from a tropical rain forest oxisol soil before and after incubating with DOC leached from native plant litter. Rapid respiratory losses of CO₂ following DOC additions to soil corresponded with significant changes in the relative abundance of SSU rDNA sequences extracted from treatment soil (+ DOC) compared to control soil (- DOC). Our results revealed that rapid DOC decomposition was carried out by an opportunistic subset of a diverse soil bacterial community. Our work suggests the importance of microbial community composition and dynamics in regulating soil biogeochemical processes, including organic matter decomposition.

Key words: soil respiration, biogeochemistry, soil microorganism, decomposition