Spatial-temporal Change Of Climate And Driving Mechanisms Of Vegetation Cover Change In Xilinguole Grasslands

The precipitation, temperature data and livestock statistical data of counties or banners was used., we analyzed the climate data, vegetation index NDVI data, livestock density data from 1981 to 2007.With statistical analysis methods, this paper discussed the detailed exposition on the climate change, vegetation cover and grazing pressure on the spatial distribution of the change trends, the dryness and NDVI as indicators. The paper analyzed the space displacement of eco-geographical zones Xilinguole League under the influence of climate change, and discussed the natural and man-made driving mechanisms of vegetation cover change.The main results as follows:1. From 1981 to 2007, the precipitation declined in most regionst; the annual average temperature of whole region showed increase trend; the degree of drought showed an upward trend overall the Xilinguole. The amount of annual precipitation depended mainly on the summer rainfall. The precipitation during 1990's was the most abundant, and the precipitation decreased significantly in 21st century. The temperatures increased since 1981, the annual average temperature of 4 eco-geographical zones showed an upward trend in volatility throughout the study period. The most dramatic warming appeared in the 1990's. 1980's and 1990's were the relatively humid periods, and the average dryness was around 22.7. The dryness showed an increase trend in most parts of Xilinguole after the 21st century, the average dryness only was 16.7.2. The wavelet analysis results showed that in the inter-annual scale, there was an obvious signal of the 25-32 year cycle of annual precipitation, annual average temperature and annual dryness in 4 eco-geographical zones from 1960 to 2007.3. The average of vegetation cover NDVI of Xilinguole League showed staggered mosaic pattern, zonal distribution, and decreased from east to west in space. The spatial distribution of NDVI inter-annual fluctuations was different, the NDVI inter-annual fluctuations were low in the west, and NDVI inter-annual fluctuations were drastic in the central and north regions. The vegetation cover NDVI showed a trend to lower in the vast majority of Xilinguole League. The eco-geographical boundaries of desert steppe zone and typical steppe zone shifted eastward obviously from 1980's to the 21st century, at the beginning of the 21st century. 4. The average livestock density showed zonal distribution in space, and increased from northwest to southeast. Considering the number of livestock per NDVI value as grazing pressure, the average grazing pressure showed zonal distribution in space, and decreased from southwest to northeast. The livestock density in Xilinguole league increased from 1980's to 1990's, but after the 21st century, the livestock density decreased obviously.5. The correlation between annual NDVI and precipitation was positive correlation in the vast majority of Xilinguole League, but the correlation between annual NDVI and average temperature was negative correlation in the vast majority of Xilinguole League; the correlation between annual NDVI and dryness was positive correlation in the majority of Xilinguole League.6. The analysis showed that the higher livestock density concentrated in the regions which NDVI was 185-200. There was polynomial regression between average NDVI and livestock density. With the change of vegetation cover in ages, the higher livestock density region shifted eastward obviously.