Monitoring Grassland Growth And Net Primary Production In Xilingol Steppe, China

Declining local agricultural production as a part of ongoing grassland degradation and desertification is considered a severe problem with global climate change and anthropogenic disturbances in the temperate region of China. Learning grassland growth and estimating its net primary production can provide important information for livestock grazing and environment protecting.In this study, Xilingol steppe was chosen as a sample region. Firstly, MODIS NDVI was used to learn the grassland growth. Secondly, images from MODIS and TOMS, monthly weather data and information from field survey were input to CASA model to estimate NPP in Xilingol steppe from May to September in 2002 and 2003. Furthermore, The NPP in each type of grassland and in each county was analyzed. Lastly, the relationship of grassland growth, net primary production and local climate character was discussed. The main conclusions and innovations were as follows:(1) The ground resolution of net primary production was 250m using MODIS data and CASA model.(2) Spatially high accuracy and timely estimation of net primary production was possible using CASA model, if Photosynthetically Active Radiation could be got using TOMS UV reflectivity.(3) The NPP values were 28.86TgC and 32.73TgC in Xilingol steppe from May to Sep in 2002 and 2003. Compared with other categories of grassland, the temperate steppe was the widest and its NPP was the most from May to Sep, which accounts for over 55% of that in Xilingol steppe during the same period.(4) NPP in Duolun County, Taipusi Qi and Xiwuzhumuqin Qi were much more than other county in Xilingol steppe.(5) In July or Aug within a year, the grassland grew best. Spatially, the grassland turned low gradually from the east to the west in Xilingol steppe.(6) Grassland growth and production in May was much more controlled by mean temperature from last November to this April, whereas growth and production during July and September were much more controlled by precipitation, especially in July and August in Xilingol steppe.