The Study On The Temporal And Spatial Variation Of NPP And Its Driving Factors In Sanjiangyuan Nature Reserve

this study use the Sanjiangyuan Nature Reserve’s meteorological data, solar radiation data ,land use data and MOD13Q1NDVI data from 2003 to 2013, with the modified CASA model and the method of mathematical statistics to research the NPP driving factors of the Sanjiangyuan Nature Reserve for the month and interannual change analysis,interannual time spatial distribution and spatial change trend analysis, calculated the NPP of Sanjiangyuan Nature Reserve from April to August 2003, 2008 and 2O13.finally, verified the years of NPP after a monthly summary. Driving factors of this study include solar radiation, temperature, rainfall, NDVI and vegetation types. This five-month inter-driving factors and interannual variability analysis results of NPP are as follows:(1) The annual total amount of solar radiation from 2003 to 2013 blessing Sanjiangyuan Nature Reserve showed overall decreasing trend, with an average annual reduction of about-1.96MJ ·m-2.a-1, the space distribution features of solar total radiation is gradually reduced from northwest to southeast. Golmud, and the most parts of Zaduo in western and eastern, the average annual total solar radiation tended to decrease, Yushu and parts of the Chenduo weighing up to reduce.(2) Sanjiangyuan Nature Reserve in the growing season from 2003 to 2013 tends a warm and humid climate, the annual average temperature of 7.6 ℃ , annual rainfall of 336.9mm, the warming trend in the annual average temperature was 0.07 ℃ /a, the increasing trend of precipitation for 1.57 mm/a. Spatial characteristics of annual average temperature in Sanjiangyuan Nature as central and western parts of the region, temperature is low,and high temperature in marginal areas, the rainfall of spatial characteristics for the north to south gradually increase; in addition to thesomel areas of Yushu with a reduced temperature year by year, the other regions rising year by year. In some areas of southern and eastern boundaries of the study area，annual rainfall is less than 0mm/a, in most other regions, rainfall radiate upward trend.(3)The year NDVI of growing season from 2003 to 2013 showed an increasing trend, NDVI gradually increasing from the north to south,and west to east in the spatial distribution.NDVI is lower at north and west, south and eastis is higher. The past 10 years, the annual NDVI of Sanjiangyuan Nature Sanctuary showing an overall upward trend. Variation in trends of annual NDVI range of-0.11/a -0.11/a, mean 0.002/a, showing an overall increase.Variation range mainly in the-0.39-0.40.(4) Growing trend of vegetation from April to Augustis presents a gradual expansion from east to west, the eastern part of the vegetation grows first, and western region grow slower, the highest month of the NPP in different regions appears different. For most of the region ,vegetation NPP from april-July constants increases ,and reached maximum in july, August began to decrease. But maximum NPP in some areas appeared in June and August. Distribution characteristics of NPP for the northern and northwestern is lower, higher in central, southern and eastern.(5)The NPP of Sanjiang Source Nature Reserve is mainly influenced by vegetation type (maximum energy utilization) and NDVI,The influence of solar radiation, low rainfall and temperature on the NPP is low. NDVI and maximum energy utilization is the main driving force of the NPP. Global The solar radiation have a positive effect on the yield of NPP, different effects in different months of monthly rainfall and monthly average temperature for the NPP mild month, July and August is negatively related to the vegetation growth, positively correlated with vegetation growth is in April and May.