| The “Three-River Headwaters” Region is the source of the Yangtze River, Lancang River and the Yellow River, it holds the pivotal status in ecological environment protection and construction in China.Net primary productivity(NPP) is the key content when researching material circulation and energy flow. Based on remote sensing data and meteorological data as model input data, using the GLOPEM-CEVSA model, estimation of the “Three-River Headwaters” Region vegetation net primary productivity in 2000-2012, NPP temporal and spatial patterns and trends in temperature and precipitation were analyzed from the regional scale. The results showed that:1. In 1990-2012, the annual average temperature presented upward trend with a tendency rate of 0.326 per 10 years in “Three℃-River Headwaters” Region, and had accelerated rise in recent years, especially in the central and southern regions; The annual precipitation of “Three-River Headwaters” Region was in the trend of 62.13 mm per ten years increasing. The precipitation in the eastern and central parts of “Three-River Headwaters” Region was mainly to increase, while the precipitation in the southern and western regions was not obvious. The west and south of the regional climate showed warm and dry trend, in the northern and eastern regions becoming warm but wet trend.2. The mean vegetation NPP in “Three-River Headwaters” Region was 149.40(unit: g Cm-2a-1, the same below) in 2000-2012. The NPP showed a significant zone characteristics decreased from the southeast to the northwest. There was a high value of NPP in the east and southeast area, the central and northern regions of low NPP. The lowest NPP was in the Tanggula Mountain Area. The value of NPP showed a rising trend at the rate of 13.7 g Cm-2 per ten years. According to the mean NPP value among different ecosystems from high to low were ranked : farmland(327.28 g Cm-2a-1), forest ecosystem(299.20 g Cm-2a-1), grassland(169.90 g Cm-2a-1),wetland(161.15 g Cm-2a-1), and desert ecosystem(75.63 g Cm-2a-1);In main grassland types, the NPP were Warm mountain meadow(321.55 g Cm-2a-1) and Alpine meadow grassland class(289.629 g Cm-2a-1). A comparison is made between simulated NPP results and field measured values to verify that there was a significant linear correlation(R2 = 0.45,p=0.00,n=32).3. From the standardized regression coefficient to analysis, vegetation NPP had a significant correlation with temperature and precipitation in a whole “Three-River Headwaters” Region, and the influence of temperature on vegetation was higher than that of precipitation. The ratio of the regression coefficient of precipitation and air temperature was 1:2.34, It showed that the air temperature in this area was the main climate control factor of vegetation NPP change.Taken together, the value of NPP hold a upward trend in overall, the year and terrain differences were big, there were clear differences in NPP between different ecosystem types and vegetation types. How to get a further study on mechanism of water and heat factors impacted on plant growth, integration based on the model simulation of remote sensing data and experimental data of vegetation physiological process, is the direction of effort for the future. In this paper, the NPP, temperature and precipitation trends in the “Three-River Headwaters” Region were studied and analyzed, which provides a data base for the vegetation growth responded to climate change in the future, and it is of great significance. |
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