| Vegetation is an important component of the terrestrial ecosystem, which play an important role in the energy and material exchange of earth’s climate. At the same time, it is a key link for the global carbon cycle. The climate change has effect on carbon cycle in ecosystem. NPP, which is momentous research content for the global carbon cycle by its changes, is a vital parameter for the physiological and ecological process of vegetation. Remote sensing technology, which has a higher application value for researching on ecological environment of vegetation, has the characteristics of wide band, high spatial resolution and carrying abundant information. Xinjiang is an area, where the glacier area is retreated, grassland is degenerated and desertification is inhancde, that is sensitive to the climate and Ecological changes. Thus, Studying on the dynamic change of the NPP has important significance for the climate change and carbon cycle of northwest arid area. But previously, some schlors utilized the climate data to simulate the climate potential productivity, which could not reflect the actual changes in the NPP and lack of analysis that affect factors variation of NPP. Therefore, the paper selected temperature and precipitation values of 51 standard meteorological stations, vegetation types, DEM and types of land use data. We analyzed spatial-temporal characteristics of NPP in Xinjiang province from 2000 to 2010 based on remote sensing model and used to MOD17 values of MODIS Terra. By means of natural breaks, we put the regression slope of NPP into five categories and discussed the spatial-temporal variation characteristics of NPP in Xinjiang, then, we analyzed the difference of NPP in different areas from two aspects of different ecological zones and administrative divisions. Further by using the climate tendency rate, spatial analyst, overlay analysis and correlation analysis method. We extracted the different altitude and different vegetation types of NPP, and got among of NPP, temperature, precipitation correlation coefficient and land use types in this study area. Then, we discussed of the changes of NPP from 2000 to 2010 in Xinjiang. This paper main conclusions are as follows:(1) The research showed that a decreasing trend of NPP in Xinjiang from 2000 to 2010. Among them, the maximum NPP is 155.8 g C/m2·a in 2003 and the minimum NPP is 32.2 g C/m2·a in 2008, and the average NPP is 145.6 g C/m2·a in 11 years. NPP showed a trend of increase area is less than the decreasing trend of the area and the tendency rate is-36.7?27.4 g C/(m2·10a). Among them, the maximum decrease of NPP is located in Altai and Tianshan Mountains, Weigan River and the Akesu River Basin, which reduce area accounting for 29.15% of the total vegetation area. The NPP increase mainly located in the north of slope Tianshan, Yarkant river oasis and Hotan oasis, which increase area accounting for 25.79% of the total vegetation area.(2) The spatial distribution characteristics that Northern Xinjiang is greater than the Southern Xinjiang and west is greater than the east in Xinjiang from 2000 to 2010. Among them, the maximum NPP is 193.9 g C/m2·a in Shihezi and the minimum NPP is 87.7 g C/m2·a in Artux of Northern Xinjiang. Yining is the highest average annual NPP is 267.4 g C/m2·a in the west of Xinjiang and Turpan is the lowest average annual NPP is 85.6 g C/m2·a in the east of Xinjiang.(3) By means of altitude, vegetation type, temperature and precipitation and LUCC, we analyzed the impact of the Xinjiang NPP:(1) The highest NPP value is 190.8 g C/m2·a when the altitude of 1150?2650 meters where vegetation types are the mixed forest, coniferous forest and other woodlands. The maximum NPP is 222.3 g C/m2·a when the elevation is 1700 meters. Higher NPP value is 162.1 g C/m2·a when the altitude of 50?100 meters in Turpan Basin. Then, NPP decreased with increasing elevation when the elevation is 2650?5850 meters. Consistent with the change of Xinjiang mountain vegetation vertical zone spectrum from meadow, alpine meadow bare rocks to ice and snow.(2) The NPP of different vegetation types had significant difference that is mixed forest > evergreen coniferous, crop > deciduous coniferous forest > deciduous broad-leaved forest>grassland>scrub.(3) Correlation analysis temperature and precipitation with NPP indicated that is a weak negative correlation between NPP and temperature. A significant positive correlation with precipitation that reflected precipitation is the main climate factor affecting NPP and promoted the activity of NPP increased. The correlation coefficient is 0.74(p<0.001).(4) LUCC research suggested that a major cause of NPP in Xinjiang reduced why crop land and grassland area decreased, construction land and unused land increased significantly. In addition, the change index of the city, oasis population creasing rapidly, the city process speed up of social and economic activities are important driving force in Xinjiang also reduced NPP. |
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