Spatio-temporal variations and impacting factors of vegetation NPP in the Bosten Lake Drainage Basin from 2000 to 2014

Net Primary Productivity (NPP) is an important indicator reflecting the response of terrestrial ecosystems to climate change, and is closely connected with climate change, and the carbon balance and cycle. NPP is a fundamental ecosystem function that is influenced by vegetation type, climate, and human activities at local and global scales. Research on NPP of ecosystems is important, as solutions are needed for issues, such as environmental change, sustainable management, and biodiversity conservation. Hence, an in-depth understanding of spatio-temporal variation and driving factors of NPP are fundamental for carbon balance and cycle in changing environments. Bosten Lake Drainage Basin, northwestern China, covers a vast area of complicated terrain, including the most of the middle Tianshan Mountains in the northwest, the entire Yanqi basin, and northeast Tarim basin in the south, and is characterized by distinctive distribution patterns of temperature and precipitation. In this paper, based on MOD11A2, GHCN_CAMS air temperature, DEM(digital elevation model), and metrological observed data, we established monthly Geographical Weighted Regression (GWR) models and retrieved near surface air temperature. Then, the spatio-temporal evolution characteristics and driving factors of NPP in Bosten Lake Drainage Basin was studied employing methods of slope, partial correlation, and multiple correlations as effective methodologies. The results demonstrate that: 1) the determinant coefficient (R2) of the monthly temperature GWR regression model was > 0.85 and R2 between estimated and observed air temperature was R2 > 0.9, indicating the accuracy of this research; 2) the annual mean NPP varied between 205.12~235.7 g·(m2·a)-1, whereas the inter-annual mean value was 221.52 g·(m2·a)-1. Generally, vegetation NPP in the research area showed a decreasing trend; 3) the linear slope analysis demonstrated that the NPP varied between -18~26 g·(m2·a)-1. The decreasing trend was mainly distributed in the mountains, which accounted for 5.23% of the total study area, whereas the increasing trend was mainly distributed to the oasis plain area, which accounted for 16.99%; 4) the regions with NPP changes resulted from climate factors of 39.81% of the total coverage of the research area.These regions were distributed in the mountainous and plain areas.By contrast, those subjected to non-climate factors occupied 16.57%, were mainly located at plain areas.Regarding the significance of this research, the results provide information for ecological environmental construction and sustainable development for the Bosten Lake drainage basin.