Soil Respiration and Carbon Dynamics as Controlled by Microbial Extracellular Enzyme Activities: Meta-analysis Results and Implications for Earth System Modeling

Tuesday, December 11, 2018 - 13:55
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Microbial extracellular enzymes catalyze rate-limiting steps in soil organic matter decomposition and stabilization. Their activities (EEAs) play a key role in determining soil respiration and soil carbon dynamics. We have conducted a few meta-analysis studies to reveal patterns of and mechanisms underlying microbial controls of soil respiration and soil carbon dynamics under different global change scenarios. First, we synthesized data from 56 studies of soil respiration in responses to climate warming. We found that warming significantly enhanced ligninase activity by 21.4% but had no effect on cellulase activity. Increases in ligninase activity were positively correlated with changes in soil respiration, while no such relationship was found for cellulase. Furthermore, warming effects on ligninase activity increased with experiment duration. Our results suggest that soil microorganisms sustain long term increases in soil respiration with warming by gradually increasing the degradation of the recalcitrant carbon pool. In the second study, we synthesized 62 publications on responses of soil EEAs and soil respiration to elevated nitrogen addition. Increases in glycosidase activity under nitrogenaddition were positively correlated with nitrogen-induced changes in soil respiration over a range of ecosystems. The third meta-analysisstudy reveals that nitrogen addition reduced the activity of lignin-modifying enzymes, and that this nitrogen-induced enzyme suppression was associated with increases in soil carbon. In contrast, nitrogen-induced changes in the activity of cellulase were unrelated to changes in soil carbon. Moreover, nitrogen effects on the lignin-modifying enzyme activity accounted for more variation in responses of soil carbon than a wide range of environmental and experimental factors. Our results suggest that, through responses of a single enzyme system to added nitrogen, soil microorganisms drive long-term changes in soil carbon accumulation. Those studies laid empirical foundation to incorporate this microbial influence on ecosystem biogeochemistry into Earth System Models and thus to improve their prediction of ecosystem carbon dynamics.

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