Estimation Of Heihe Basin Net Primary Productivity Using The CASA And Multi-spectral Radiometric Data

Terrestrial ecosystem is the supporting system for biosphere as well as human being's survive and development. The carbon cycling is interrelated to global climate change, and the research of carbon cycling will help the development of global climate and ecosystem. For the county's profit, China has to evaluate the output and absorbed greenhouse gas volume to gain active status during diplomatic negotiation. The estimation of global carbon balance research indicate that there may be a big missing carbon sink exists in middle and high latitude of Northern Hemisphere, and the ecosystem problem in Heihe Basin has become severe, which attracts many researchers attention. Therefore the research of calculating net primary production in Heihe Basin can help to find driver factor of vegetation fixing CO2.The thesis is about retrieving NPP in Heihe Basin using CASA (Carnegie Ames Stanford Approach) and multi-spectral radiometric data, in VC++ program environment, obtaining temporal and spatial distribution of NPP in Heihe Basin during 1998-2002, analyzing vegetation's feedback on climatic conditions. Then simulating under the situation of the climate change to warm and moist, and the Basin's NPP temporal and spatial dynamic transformation. The conclusions are below:1. Validate the CASA's applicability in inland watershed scale. CASA initially was established to estimate global NPP, the thesis proves its high accuracy in watershed scale according to applying it to Heihe Basin.2. Estimate the amount of NPP in Heihe Basin during these 5 years, the total amount NPP in Upper reaches of Heihe Watershed is the biggest, the middle reaches is the second, and the lower reaches is the third. From 1998 to 2002, the NPP does not change much, maintains stably under normal fluctuation range. The result indicates during these years the temperature, rainfall, radiation and vegetation do not alter enormously.3. Analyze the relationship between NPP and temperature, rainfall, radiation and NDVI and I find that NPP is the complex result of heat and moist, the basin has the biggest correlative coefficient with radiation, especially in upper and middle reaches of Heihe Basin, the whole watershed has low correlative coefficient with rainfall.4. The lower reaches of Heihe Basin has little relation with temperature, rainfall, radiation and NDVI. The upper and middle reaches of basin intercept the most part of water resource, the rainfall in lower reaches is much less than evapotranspiration, in these areas the vegetation grow in severe arid condition.5. Simulate the Basin's NPP temporal and spatial dynamic transformation under thesituation of the climate change to warm and moist. Upper reaches mountanious region and middle reaches oasis decrease a little, lower reaches hungriness vegetation increase a little.6. CASA output many parameter data, including net primary production, Absorbed Phtosynthetically Active Radiation by vegetation, Light Use Efficiency, Estimated Evapotranspiration, et al. All of these data are useful for quantitative research of Heihe Basin vegetation photosynthesis and ability of assimilating carbon.