本研究通过对我国陆地生态系统8个典型样地的植被指数取样实验和图像计算结果发现，这8个样地植被指数随着水、热因子的季节变化，在时间和空间上具有一定的“绿波推移”和“景观更替”规律。在中国东部湿润的季风区（样地1－3），随着纬度的增高，其月平均植被指数与月平均气温有较大的相关。发现降水相对丰沛的地带，热量和光照条件的变化成为植被生长和变化的自然限制因子；而在中国北方森林－森林草原－典型昌原－荒漠草原－荒漠地带上，随着从东部（湿润地区）到西部（干旱地区）干湿条件的更替，月平均植被指数与降水多寡有较大的正相关关系。在8个样地上都呈现出共同的规律，即定向风的分布与植被指数的分布在时间和空间上具有逆相分布的“套合关系”。尤其在时间上有相逆套合关系，这正是中国北方沙尘暴和沙漠化加剧的自然原因。本研究定量地给出了我国陆地不同经纬度带生态系统脆弱季节和累积时间的分布。

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.