干旱区生态环境知识资源中心

The Rothamsted soil-carbon turnover model was used to determine rates of change of organic carbon in soils of a degraded semi-arid land system of New Zealand. Estimates of annual inputs, net primary production (NPP), and recovery time to raise carbon from a degraded state to a sustainable level of production were obtained. The annual inputs and hence the NPP were estimated by running the Rothamsted soil-carbon turnover model in reverse. Inputs included the organic C content of the soil, clay content, monthly temperature and rainfall and the rate of decay of annual inputs. An estimate of the biologically inert organic matter fraction was obtained from the radiocarbon content of soil organic matter. The soil recovery time was estimated by determining NPP for a relatively undegraded soil and and applying carbon at this rate to a degraded soil. The predicted total annual plant residue inputs were 1.81 tha(-1) y(-1) and the predicted inert organic matter content from radiocarbon data is 5.12 tha(-1). The estimated time needed to raise carbon from a degraded state to the level of an undegraded site is 48 years. This is most likely an underestimate, because in initial years the vegetation will not be capable of adding the same annual carbon input as the undegraded site. The refinement of this estimate of recovery time will require data on the rate of increase in net primary productivity with revegetation.