Vegetation Coverage Change And The Driving Force Quantitative Research In Sichuan Province

Vegetation is the tie that links soil, water and eco-environment,therefore, it plays a role of indicator in globalchange. Vegetation cover change is a direct result of ecological environment variation. Considerably it represents the ecological environment's overall status. Sichuan Province is located in the first and the second stage of our country's topography with a steep and complex landscape. It is a typical ecologically fragile region and also an important ecological barrier of the upper reaches of Yangtze River. Since vegetation and weather conditions also have significant regional differentiation characteristics.therefore, quantitatively study the driving force of temporal and spatial variation of vegetation cover change in Sichuan province has important practical implications for agriculture, forestry, and environmental protection and so on.Based on the NOAA / AVHRR-NDVI time series data set from 1982 to 2006 and meteorological data over the same period, trend line analyzed method is applied to study vegetation and meteorological factors change in temporal and spatial sequence in Sichuan province.correlation analysis is used to analyze the correlation between vegetation change and meteorological factors in the study area.we use residual analysis method to strip out human activities and natural factors, and established a trend model of vegetation response to climate chang.then we get the residuals between measured and simulated vegetation to act as the human activities affection, based on all these works we have done,climate and human activities contribution rate to vegetation coverage change can be assessed.The main conclusions are as follows:1.In terms of spatial and temporal varies trend,Sichuan annual NDVI maximum is 0.6574 and appeared in 1990,the minimum is 0.6034 and appeared in 2005,NDVI shows a volatility decline in all the four study period. In 1982- 2006 NDVI decreased most significantly, the down slope is the maximum among them.2.In terms of different study period,the vegetation cover change varies.The spatial distribution of vegetation cover is significantly different in Sichuan province. The vegetation cover is high in the northen of West Sichuan Plateau,Qionglai mountains and northeastern area of Sichuan. The coverage in dense urban area in che central Sichuan province and Panxi Region is lower.In the northewest and south West Sichuan plateau, along with Chengdu urban, the vegetation coverage is the minmum.3.The impact of climate factors on vegetation coverage change varies over time,vegetation coverage decrease with temperature and precipitation increasing,and the negative correlation between vegetation and annual temperature is significantly greater than that and precipitation. In the period of 1982 – 2006, vegetation cover is improved significantly in northern West Sichuan Plateau and central Sichuan Basin region. The improved area concentrated in central Sichuan basin region in the period of 1982-1989.Panxi region and Qionglai mountain area vegetation coverage improved significantly in the period of 1990-1997.Northern Panxi region and West Sichuan Plateau is the vegetation coverage improved significantly area in the period of 1998-2006.The effect of temperature and precipitation on vegetation coverage change in the study area changes over time.The two both show negative impact on vegetation growth, and compares to annual precipitation, annual temperature influence vegetation coverage change more.Meanwhile,annual temperature showed significantly negative influence on vegetation coverage change in the period of 1982-2006 and 1982-1989.that is to say,vegetation coverage change is sensitive to annual temperature change,it decreases obviously as temperature increases.As for different study regions,vegetation cover and change is mainly affected by the negative impact of precipitation in west Sichuan plateau,temperature affect panxi region and the Sichuan basin more.4. Using residual method,we find that the temporal and spatial vegetation coverage change is influenced by human activities in large extent.compared with short time sequence, the impact of human factors is greater in long time series.