Temperate steppe is sensitive to fluctuation of ecohydrological conditions and human disturbances such as increasing pressure of grazing by domestic herbivores. Temperatures are increasing, and higher associated rates of evaporation will likely bring drier conditions in large portion of monsoon Asia areas where ecosystems and social-economy are under pressure of water deficit. Regional climate model projects that severer water shortage, intensifier land degradation, and more frequent dust storms will likely occur over monsoon Asia in coming decades, as consequences of climatic change and increasing human pressure. The objective of this study was to examine the decadal trends and spatial patterns of variability of aboveground net primary production along gradients of bioclimate regimes and grazing intensity in temperate steppes in Inner Mongolia. Here we examined vegetation greenness time series derived and fused from two satellite sensors to investigate interannual changes of primary production over the region. We applied a meta analysis of field ANPP data collected from various locations to scale up the patterns with fractional analysis of fine resolution satellite data.
Results/Conclusions
Increased biological production was evident in large portion of the study region, but declining vegetation growth was also observed in some areas over this steppe biome. There were strong interannual variability throughout the region, with the greatest fluctuations occurred along the ecotone between semi desert and desert steppe in the west. Mean annual net aboveground primary production since early 1980s ranged from about 120 g/ m2 in semi desert vegetation in the west to about 3300 g/ m2 in the northeast Inner Mongolia. Major linear greening trends were observed in semi desert, desert steppe, and typical steppe located in western and central Inner Mongolia, while meadow steppe (Stpia baicalensis) dominated northeast showed slight declining in primary production. The negative trends in primary production in northeast were coincide with increasing water deficit, i.e., Palmer Drought Index, while enhanced vegetation growth in rest of the region is likely contributed by the combination of relatively favorable water availability and recent grazing ban policy that closed 20% of rangeland and put another 30% in rotation. There is a clear evidence of grassland recovery in enclosed rangeland, however, the lifted grazing pressure were relocated to adjacent rangeland and cause further overgrazing, especially in northeast where stocking rate is already high.
