Research On A Remote Sensed-based NPP Model And Environmental Response For Semiarid Grassland Ecosystem

Located in the interior region of the Eurasian continent at middle latitudes, and in a transitional zone between the arid Northwest region and the moisture Northeast region or the dry-land agricultural region in North of China, Inner Mongolia has been dominated by grassland vegetation under a semiarid climate. The regional development has shown great importance to our country in ecologic security and sustainable development. Grassland vegetation, which is the primary producer in grassland ecosystem, has very serious effect on regional climate and even global climate and environment change. Supported jointly by Chinese National Key Project for Basic Research (Grant No. G2000077907) 'Study on application of quantitative remote sensing in environmental construction of west China', this paper engages in monitoring, analyzing and evaluating the grassland eco-environment mainly using MODIS products. It concludes:(1) Research on remote sensed-based net primary productivity in semiarid grassland. The model uses the concept of Light Use Efficiency (LUE), while change of air temperature, plant-water deficits and respiration reduce the efficiency of light usage, and the model is modified to couple with ecology model to better represent regional environmental characteristics of the semi-arid grasslands. In this study, the two different v/ays to simulate NPP in the process of vegetation growth were introduced to calibrate model parameters. The accuracy of model products was assessed through comparing them with MODIS data, field measurement and other correlative models. The promising results suggest this model could provide spatial and temporal distribution of net primary productivity for semi-arid grassland management.(2) The methods of assessment of regional grassland degradation. Two methods to obtain the intensity of grassland degradation were conducted. On the one hand, it is based on the ecological analysis method, the judge of grassland degraded and intensity of degradation by comparison of the recent grassland and the formal non-degraded grassland, which MODISFPAR was validated as the all-around denotation variable to...