Uncertainties related to the temperature sensitivity of soil carbon decomposition

Abstract

The fate of soil carbon stores in response to global warming is hotly debated as considerable uncertainties remain in forecasts of the temperature sensitivity of soil organic matter decomposition. This is the result of disagreements in the response of heterotrophic respiration and dissolved organic carbon release to temperature. In the case of soil respiration uncertainties are derived from the inclusion of fixed Q(10) values of 2 and a variable number of carbon pools in the models. For the soluble carbon no consensus has emerged in relation to the causal factors leading to the observed carbon exports from organic soils. In most predictions soil biology is poorly represented despite current knowledge indicating that warming can induce important changes in below-ground invertebrate Populations which could have important consequences for organic matter decomposition and nutrient cycling. Furthermore, the evidence that the adaptation of soil invertebrate Populations to changing climates will exacerbate decomposition of long-standing soil carbon reservoirs and diminish the predicted respiration acclimation effects is critical to develop more realistic predictions of the fate of our terrestrial sink.