In this study

three test sites with the same longitude have been selected from south to north in wetland area（the monsoon region） of Eastern China. Five test sites with the same latitude have been selected in arid or semi-arid area of North Western China（the Non-monsoon region）. Production of 24J month time series of one month maximum NDVI composites have been accomplished based on NOAA AVHRR and Landsat-TM data. Average temperature

precipitation and wind-speed data in each average of the month to be synchronous have also been input into computer for analyzing the dynamically correlated model of driving forces of land cover Changes Conclusions have been drawn that land- cover change in China has distinct seasonal fragileness in each test site and their relationship has been found. In the study

we draw the following conclusions: （1）Vegetation is the connection of soil

atmosphere and precipitation.When using vegetation as an indicator of land cover change

not only seasonal but also spatial change has been found in the land cover change. In addition

some unstable phase has also been identified. We conclude that the unstable phase in land cover was related to the seasonal and longitudinal change. （2）The zone and coastal plain of east of China belong to East Asian Monsoon.The climate is rather wet. The correlation between NDVI and temperature is obvious. But the correlation between NDVI and precipitation is not so good. Therefore

we conclude that in a region of high precipitation

temperature is the key affecting factor for growth of vegetation. （3）In northwestern China

the Big Xingan Mountain forest area

the typical grassland area and arid desert area almost lie on the same latitude. From east to west

the land cover types are forest

forest grassland

typical grassland

desertgrassland and arid desert. In the line

as the distance from coastal line increase

the monthly average NDVI value depends largely on precipitation. Thus

compared with temperature

precipitation is the key affecting factor for vegetation growth in arid area. （4）From south to north

under the limitation of temperature

the deviation of averages NDVI is not obvious. However

the seasonal deviation is high. From east to west

under the limitation of precipitation

the regional deviation of NDVI coincide with the productivity of vegetation. It implies that temperature affect the budding

flowering

fruiting of vegetation. On the other hand

precipitation affects the productivity of vegetation. （5）Wind is one of the driving forces causing desertification in dry and semi dry region. The period of lasting of strong wind seems to be coincident with the degradation of vegetation for each test sites. In contrast

when the cover of vegetation was at maximum

wind speed was found to be minimum

because of the inverse relationship between wind speed and NDVI

desertification and land degradation happen in the grassland and cultivated land in northern China. Some researches show that desertification and land degradation happened on winter and spring

which coincide with the unstable stage

found in our study.