Estimation Of Grassland NPP And Factors Influencing In Gansu Province

As supporter of climatic change, grasslandgrassland not only is sensitive to entironmentchange, but also can feedback to climatic change. The productivity of grasslandgrassland hasbeen decreased gradually by reason of climatic change and rapid development of communityand economy.In order to supply basic data support for using and protection of grasslandgrasslandresource in Gansu province, we selected CASA model and its driven data of NDVI andmeteorological data contaning monthly precipitation, mean monthly temperature and monthlysolar radiation to estimate grasslandgrassland NPP in Gansu province on Arc GIS platform.The main conclusions were as following:1) It was found that the interpolation of Σθ and r with M-AMMRR method has moreprecision, realistic performance which took micro topographic factors such as slope andaspect into regression formula based on AMMRR method.2) According to the comparision between simulative grasslandgrassland NPP andobservated grasslandgrassland NPP or previous study results, we discovered that theimproved CASA model with perfectly sumilative performance, whose εmaxand water forcingcoefficient were modified can accurately estimate grasslandgrassland NPP in Gansu province.3) From2001to2010, the mean annual NPP of grasslandgrassland fluctuated in yearswith mean value of133.87gC·m-2·a-1, varing from minimum value of122.67gC·m-2·a-1tomaximum value of142.49gC·m-2·a-1, and its corresponding mean annual total NPP was3.62×1013gC·a-1, ranging from3.62×1013gC·a-1to3.85×1013gC·a-1. Seasonly variation ofgrasslandgrassland NPP was significant with total NPP (60.93%) in summer and total NPP(3.15%) in winter, respectively.4) High-cold meadow and Temperate montane meadow had the highest NPP with1.09×1013gC·a-1and9.79×1012gC·a-1, occupying29.98%and26.96%of mean annualgrasslandgrassland NPP in Gansu province, respectively. But, the preponderantgrasslandgrassland classes of Lowland meadow and Temperate desert had the lowest NPP,which accounted for31.96%and23.07%of mean annual grasslandgrassland NPP in Gansuprovince, respectively.5) The spatial distribution pattern of grasslandgrassland NPP represent declining trendfrom southwest to northwest, which was highly agreement with water and heat condition instudy area. There had significant difference of its spatial distribution with high NPP inGannan plateau and low NPP in north mountains. The spatial variation showed74.42%areaof mean annual grasslandgrassland NPP with non-significant changes,15.86%withsignificant decrease and9.74%with significant increase, respectively.6) There had extre-significantly positive, non-significantly negative and weakly positivecorrelations between mean annual grasslandgrassland NPP and annual precipitation, mean annual temperature and annual solar radiation. It showed a extre-significantly positivecorrelation between mean annual grasslandgrassland NPP and altitude, but with weakcorrelations to slope and aspect. Other human activities had non-significantly negativecorrelations with annual grasslandgrassland NPP exception for rural population.