Microbial decomposition of soil organic matter is a key process in determining the carbon sequestration potential of tropical ecosystems and carbon fluxes to the atmosphere. Since microbial decomposition is highly sensitive to changes in temperature, predicting the temperature sensitivity of microbial decomposition is critical to predicting future atmospheric carbon dioxide concentrations and feedbacks to anthropogenic warming. Fundamental principles derived from enzyme kinetics predict that the temperature sensitivity of microbial decomposition should increase with increasing biochemical recalcitrance of a substrate. Yet, the generality of this principle has yet to be tested and we know little about how microbial acclimation to long-term increases in temperature would affect its role in determining temperature sensitivity of organic matter decomposition to increased to temperature. To these purposes, we measured the temperature sensitivity of microbial respiration of soil organic matter with serial short-term and long-term temperature manipulations over 365 days for 28 North American soils. These data were then joined from similar studies that represent a wide variety of environmental contrasts.
Results/Conclusions
We show that the temperature sensitivity of organic matter decomposition scales with biochemical recalcitrance. With physico-chemical protection likely an important covariate for relating plant and soil organic matter decomposition scalars, biochemically recalcitrant organic matter is highly susceptible to short-term increases in temperature, a key link in predicting the effects of warming on carbon cycling. That said, there are important patterns to acclimation of temperature sensitivity which suggest that the pattern of future warming might control the fate of tropical soil organic matter in a warmer world.