Analyzing On The Change And Driving Force Of Vegetation Cover In Heihe River Watershed Based On The MODIS Data

Vegetation plays an important role in global change, and it is an important, component of the terrestrial ecosystem. It also affects the energy balance of the earth atmosphere system and act as a sensitive indicator of the impact of climate and human factors on the environment. To carry out dynamic monitoring of vegetation can reflects the development of climate change at a certain extent, a hot topic and important content of dynamic monitoring of vegetation and vegetation cover change is also in global change research.Heihe river basin is a typical inland river basin in arid region of northwest China, and it contains diverse landscape types and a variety of abundant natural resources. At the same time,due to the deep location of the hinterland of the Eurasian continent, less precipitation, high temperature, dry climate, and excessive consumption by human activities in the basin within the limited water resources in recent decades, its natural vegetation ecological environment becomes weak and the ecological system turns unstable, It is a sensitive area of climate change.This paper based on the 2000~2013 MODIS NDVI data, climate data and statistical data as the data source, based on the RS and GIS technology and applied maximum value synthesis method, average method, pixel decomposition method, correlation analysis method and principal component analysis to dynamically monitoring the change of vegetation coverage in the Heihe river basin and to explore the effect of vegetation coverage change the main driving factor, draw the following conclusions:(1) Vegetation coverage of Heihe river basin is generally low in recent 14 years and mainly in the low vegetation coverage. Because of regional differences, it presents obvious vertical zonality in spatial distribution caused by regional differences. Upstream vegetation coverage is good and mainly consists of the high and middle-high coverage vegetation;vegetation coverage of the middle reaches is middle coverage vegetation, downstream is mainly covered by low coverage vegetation.(2) From the variation of vegetation coverage, cover change to the good direction of the vegetation in the whole basin, the area of middle-high coverage vegetation and middle coverage vegetation present increase trend, the low coverage vegetation and high coverage vegetation areas are decreasing, the change range of low coverage vegetation to middle coverage vegetation is obvious.(3)On the whole, watershed vegetation cover change is the main driving force of human factor, the contribution rate of about 80%, and the rate showed an increasing first and then decreased trend, the influence degree of the corresponding natural driving force is showing a trend of first decreased and then increased.(4) On regional scale, influence degree which caused by artificial factors induced upstream vegetation coverage change showed a decreasing trend, and the degree of natural factors showed decreased first and then increased trend; the main driving force which influence middle vegetation coverage change is the human factors and the influence degree tends to be stable; Under the influence of tour plant cover changes mainly is the driving force of natural factors, the person factor of vegetation cover change is also very big.