Research On The Changes Of Net Primary Product Based On The MODIS In The Upreach Area Of Shiyang River Basin

Net primary productivity (the NPP) is the result of the interaction,between theplant own biological characteristics and environmental factors.It is the net to create ofphotosynthesis to organic matter. It determines the composition of the earth and alllife functions of the natural ecology.It is an important partner who changes materialon the earth by the atmospheric composition, especially the changes in CO2concentration.So it is a important thing for the research of NPP to climate. Researchon the changes of net primary productivit in the upreach area of Shiyang RiverBasin,we can recognize the degradation of vegetation,which provides a theoreticalbasis and science and technology to support for the local economy and the wholeecological environment and related fields.This paper used CASA model, combining multi spectral remote sensing data andclimate data, estimated net primary productivity in the upreach area of Shiyang RiverBasin from 2000 to 2009,by NPP data products and Gansu Grassland inventory datafor its validation, and make the corresponding analysis. First of all, we analyzed theover all spatial distribution of NPP in the study area nearly ten years. In addittion, wealso analyzed the seasonal variation of NPP. Finally, we analyzed the changes of NPPwith the different elevation changes. At the same time, combining the distribution ofvegetation in different regions and landscape features,we analyzed the distribution ofNPP,described the NPP of different vegetation types, analyzed the overall trend inrecent years NPP and discussed the driving factor of NPP to the study area. Theconclusions as follows:(1) Revised FPAR of the CASA model parameters ,by NPP simulation and NPPproduct on MODIS in upreach area of Shiyang River Basin in 2005 and SunanCounty Grassland resource inventory data,we made validation analysis.It isrecongized that improved CASA model is suited to estimate and research NPP of thegrowing season of vegetation in the upreach area of Shiyang River Basin.(2) The fundamental spatial pattern of annual NPP in the upreach area of ShiyangRiver Basin was characterized by high NPP levels distributed in the West and by lowNPP levels distributed in North,then the NPP levels rapidly reduced from Northwestinto southeast. This distribution was bound up with different hydrothermal conditionsand variation of zonal of vegetation.From east to west along 37°14′52.064″N,and withthe increase of elevation, the value of NPP was on the increase,which illustrated that there were a better consistency between the phase change of NPP and altitude in thislatitude.Judging from different vegetation types,the general sequence of Study area ofNPP was Mountain evergreen broad leaf deciduous broad leaf thickets bushes andmountains,the alpine coniferous,alpine meadow,cultivated land,meadow,desertgrassland.There was a close relationship between the distribution characteristics ofNPP and rivers,which follows the distance attenuation rule.It was that as the increaseof from rivers distance the value of NPP is attenuating.(3) By analyzed seasonal variation of net primary productivity of vegetation ingrowing season,it was conclued that monthly mean NPP from May to September firstincreased and then decreased from 2000 to 2009.Among them, the mid July toAugust,the net primary productivity of the period reached a maximum value.(4) Latitudinal profiles from the point of view, the overall distribution of NPPcurve decreased slightly in the study area from 2000 to 2009,which indicated thatthere was a further degradation trend of vegetation in the area. The overall trend of thestudy area for the NPP:the reduction area of vegetation NPP is mainly distributed inthe West River, East River, xiying River, Gulang River and the dajing River .Theincreased NPP of vegetation areas are mainly scattered in Huanghe River and EastRiver northeast.Most of the other regions did not change significantly.(5) By analyzed the correlation between vegetation NPP and FPAR, temperature,precipitation, it was conclued that FPAR and NPP is closely relationship, and therelevance of precipitation and temperature was decreasing orderly.