Responses of NPP of salinized meadows to global change in hyperarid regions

Growth of plants and formation of net primary productivity (NPP) of salinized meadows in hyperarid regions in the north of the Tarim Basin, Xinjiang, China, mainly depends on the undergroundwater which provides the transpiration requirement of plants and supports the evaporation of water from the soil. Based on the understanding that the more the undergroundwater evaporates, the greater the soil water regime keeps, and the more the NPP of salinized meadows form, we developed a model for estimating the NPP of salinized meadows in hyperarid regions in the north of the Tarim Basin. Responses of NPP of salinized meadows to global change were predicted with the model. The results showed that the NPP of salinized meadows is a function of the undergroundwater table (UWT) and the air temperature. The NPP of salinized meadows varied with the difference in UWT, and declined logarithmically with decrease of UWT. The NPP of salinized meadows with shallower UWT is greater than that with deeper UWT in similar climate and soil conditions in hyperarid regions in the north of the Tarim Basin. Responses of the NPP with deeper UWT to variation of UWT and air temperature resulting from global change are more sensitive than that with shallower UWT. Impacts of global change on NPP of salinized meadows in hyperarid regions, therefore, depend largely on the salinized meadows with various UWT. (C) 2002 Elsevier Science Ltd.