Luo Tianxiang, Li Wenhua, Leng Yunfa, Yue Yanzhen
Based on more than 800 measured plots and the inventory data of natural resource survey,the total biomass of natural vegetation was estimated for various counties of Qinghai and Tibet provinces,which was 2.586×108t for Qinghai and 1.282×109t for Tibet.The QZNPP model established here shows that,as temperature rises by degrees,net primary productivity (NPP) increases in the way of "S" curve;the rate of increasing is quickened by more precipitation.The rapidest rate appears when the annual mean air temperature is 0℃~10℃ and the annual precipitation is 400 mm-1 000 mm.When the temperature is over 11℃ and the precipitation is more than 1 100 mm,NPP approaches a maximum of 20 t/ha·a;and in the condition of less than 0℃,with the increasing of precipitation,NPP declines slowly,indicating that temperature is a major limiting factor.A biomass map for the 115 counties in Qinghai and Tibet provinces shows that,the maximum biomass occurs in Motuo County of Tibet,up to 196 539 t/ha;the second is in Chayu,Bomi,Linzhi and Milin counties of Tibet,whichis 115 t/ha~140 t/ha;the value is only 1 t/ha~5 t/ha in the extensive regions in north west Tibetan Plateau.A map of potential NPP for the natural vegetation of the Tibetan Plateau indicates that NPP varies from 0 to 20 t/ha·a;the area weighted average of NPP is 6.03 t/ha·a,less than the value of the global terrestrial vegetation (7 82 t/ha·a).