Detection of dry lake beds formation and estimate of environmental regime shift in semi-arid region

抄録

In the Inner Asian Gobi desert, vegetation distribution mainly has annual herbs and perennial shrubs. Annual plants strongly depend on rainfall, and perennial plants can survive even in years of extreme drought. In this study, we used remote sensing method and field experiment method, to extract the area where regime shift had occurred in semi-arid region and to estimate the critical wind speed of dust emission from dry lake beds and desert steppe. Hovmoller diagrams are efficient for displaying large amounts of data in a meaningful manner. Hovmoller (time-longitude) diagrams were generated to summarize and examine the space-time features of seasonal evolution and the anomaly patterns for the entire monthly time series during 1985-2013. Because of analyzing the Hovmoller diagrams generated using vegetation index and precipitation data, NDVI values tended to increase with increasing precipitation during the vegetation growth period (VGP) between May and September. Vegetation showed high response to precipitation during the VGP. Moreover, the results of this study showed that the areas with less precipitation were more sensitive to the dynamics of precipitation than the areas with more precipitation. The most degraded area was the southwest region of Gobi with the least precipitation. The NDVI values responded to precipitation over vast areas including Inner Mongolia, China. In some areas, we estimated that the ecosystem has been destroyed and regime shift of ecosystem had occurred.