基于CASA模型的吉林西部植被净初级生产力时空特征及其碳汇量估测

he net primary productivity (NPP) and net ecosystem productivity (NEP) in western Jilin province have been estimated by using MODIS, meteorological data and vegetation type map, along with combination of CASA model and soil microbial respiration model. Analyzing the temporal and spatial variation and the reason causing the change in NEP of alkali soil, it is found that NPP in this area showed an increasing tendency from west to east. Within this study area, the NPP is higher in the east and the southeast while lower in the middle and the west. The annual NPP is not much related to the temperature and precipitation，but the NPP of September only is highly related to the precipitation. NEP<0 in the southwest, northwest and central parts owes to the alkali soil. By comparison, the NEP is higher in the east and the northwest. The overall NEP has shown an increasing trend over the last 10 years, with some fluctuations due to climate change. Between the years of 2001 and 2009, the alkali areas with NEP<0 have been decreasing while that with NEP>0 increasing. It is found that fence-feeding and other methods have played a positive role in improving ecological environment of Jilin western land.