PARENT SESSION
Poster Session #1: Decomposition and Soil Respiration.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Production, bioavailability, and isotopic composition of dissolved organic carbon: Results from a decomposition experiment.

CLEVELAND, CORY^*,1, NEFF, JASON², TOWNSEND, ALAN¹, ¹ INSTAAR, Boulder, CO² Earth Surface Processes Team, Denver, CO

ABSTRACT- Dissolved organic carbon (DOC) fluxes are important for the formation of soil organic matter, and for the redistribution of carbon both within and between terrestrial and aquatic ecosystems. However, DOC dynamics, and in particular microbial control on the flux and composition of DOC in soil, are only partially understood. Using DOC leached from dry foliage and litter (of both temperate and tropical species) and inoculated with a system-specific soil microbial community, we conducted an experiment to determine: 1) the solubility (production) of DOC from leaf litter from water leaching; 2) the dynamics of DOC biological availability throughout a three month decomposition experiment, and; 3) the isotopic composition ( ¹³C) of DOC before and after decomposition. Our results suggest that DOC production rate from litter leaching is highly plant species dependent, ranging from <0.2% to more than 3% of total litter biomass leached as DOC during a single wet-up. In addition, we found that a very large fraction of DOC produced from litter of many plant species is readily available for rapid microbial decomposition, with >70% of initially extracted DOC leached from an alpine forb (Acomystalis rossii) consumed within the first 10 days of the decomposition experiment. Finally, despite using leachate from a diversity of both species and ecosystem-types, our data provided no evidence of microbial carbon fractionation during decomposition, and we conclude that this process does not contribute significantly to elevated ¹³ C values commonly observed with depth in soil profiles.

KEY WORDS: carbon, decomposition