CO2 produced through microbial respiration during litter decomposition is one of the major constituents of atmospheric CO2 preventing a reduction in atmospheric carbon by plant uptake in natural ecosystems. Respiration fluxes can range from 10 to 50% of the ecosystem-scale gross primary production, and turn ecosystems from carbon sinks to carbon sources when plant carbon uptake is hindered. Along with the immediate release of CO2 into the atmosphere, another major product of litter decomposition is dissolved organic carbon (DOC) which remains in the soil. DOC that permeates into deeper soil layers becomes more stable and is an important contributor to soil carbon stocks. In previous experiments our team identified a variety of microbial decomposer communities that differ in the amounts of CO2 and DOC produced during early phases of plant litter decomposition in controlled microcosm systems. In this experiment, our goal was to test the impact of microbial community composition on carbon flow in a complex and realistic system. To achieve this, we inoculated natural, arid-soil cores containing 13C-labelled blue gramma grass (Bouteloua gracilis) litter with microbial communities previously shown to produce either high or low DOC extremes and then measured their CO2 and DOC production.
Results/Conclusions
Our results show increased CO2 flux from soil cores inoculated with high DOC communities compared to those inoculated with low DOC communities or controls. From a carbon balance perspective this suggests that CO2 and DOC production during litter decomposition are not always inversely correlated, but can also be additive. We will explore whether this additive effect was due to faster decomposition, and/or presence of specific microbial communities, and if DOC production was affected by the natural soil environment.