Is resistant soil organic matter more sensitive to temperature than the labile organic matter?

Abstract. A recent paper by Knorr et al. (2005a) suggested that the decomposition of resistant soil organic matter is more temperature sensitive than labile organic matter. In Knorr et al.'s (2005a) model, the reference decay rate was presumed to be same for all pools of soil carbon. We refit Knorr et al.'s (2005a) model but allow both the activation energy and the reference decay rate to vary among soil C pools. Under these conditions, a similar fit to measured data can be obtained without invoking the assumption that the resistant C pool is more temperature sensitive than the labile pool. Other published evidence does not unequivocally support Knorr et al.'s (2005a) hypothesis of increased temperature sensitivity of resistant pools of soil carbon. Because of the lack of experimental data, Knorr et al.'s (2005a) conclusion that the decomposition of the resistant SOM is more temperature sensitive than the labile pool is premature.