Sensitivity analysis and calibration of a soil carbon model (SoilGen2) in two contrasting loess forest soils

摘要

To accurately estimate past terrestrial carbon pools is the key tounderstanding the global carbon cycle and its relationship with the climatesystem. SoilGen2 is a useful tool to obtain aspects of soil properties(including carbon content) by simulating soil formation processes; thus itoffers an opportunity for both past soil carbon pool reconstruction andfuture carbon pool prediction. In order to apply it to various environmentalconditions, parameters related to carbon cycle process in SoilGen2 arecalibrated based on six soil pedons from two typical loess deposition regions(Belgium and China). Sensitivity analysis using the Morris method shows thatdecomposition rate of humus (k_HUM), fraction of incoming plant materialas leaf litter (fr_ecto) and decomposition rate of resistant plantmaterial (k_RPM) are the three most sensitive parameters that would cause thegreatest uncertainty in simulated change of soil organic carbon in bothregions. According to the principle of minimizing the difference betweensimulated and measured organic carbon by comparing quality indices, thesuited values of k_HUM, (fr_ecto and k_RPM in the model are deducedstep by step and validated for independent soil pedons. The difference ofcalibrated parameters between Belgium and China may be attributed to theirdifferent vegetation types and climate conditions. This calibrated modelallows more accurate simulation of carbon change in the whole pedon and haspotential for future modeling of carbon cycle over long timescales.