| Aims to reveal the response of the regional vegetation changes to regional climate change, this paper studied the Spatial-temporal characteristics of vegetation cover variations in Upstream of the Shiyang River Basin from 1998 to 2008 based on a time series of SPOT-VEGETATION Normalized Difference Vegetation Index (NDVI) data with 1km×1 km spatial resolution, Precipitation data and temperature data. The linear regression, trend analysis, correlation analysis were used to characterize the trends in vegetation cover change and the relation with the climate change. Main conclusions and progress are as follows:(1) Spatial distribution characteristics of the NDVI:Along with the change in altitude, the distribution of the NDVI in the research areas showed the regular changes. From the northeast to the southwest, the NDVI first increased and then decreased with the rise of altitude. The vegetation presents a zonal distribution form northeast to southwest.(2) The character of temporal change of the NDVI:The NDVI in the research areas trends to increase indistinctly as a whole during 1998 to 2008. Both the annual NDVI and the average NDVI in spring, summer and autumn of the different vegetation types were on the rise, which indicates the growth period of the vegetation was prolonged. From the different NDVI clustering types, the NDVI of low-cover category whose average NDVI is less than 0.15 is on a declining trend, and the others are in a rising trend. The vegetation starts turning green from April and the best vegetation months appears in July and August.(3) Spatial change characteristics of the NDVI:In the recent 11 years, the activity of the vegetation strengthens in most research areas, however, the vegetation degradation and deterioration appeared locally. The area where the vegetation cover increased occupies 73.36% and vegetation degradation is 17.47%.(4) Relationship between the NDVI change and climate change:Firstly, the annual average NDVI have significantly positive correlation with annual precipitation, and it have little positive related with annual mean temperature in the study area. These suggest that the impact of precipitation on vegetation is more sensitive than the temperature's impact in the study area. The annual precipitation is the major factor influencing annual average vegetation.Secondly, there exists lag between average season NDVI and precipitation. The precipitation acted as a stimulus to the growth of the vegetation. The precipitation had more effects on NDVI than temperature in summer and autumn in summer and fall, but it is reverse in spring. The influence of temperature on vegetation mainly embodies promoting function in spring and inhibitory effect in summer. The rise of the temperature in spring was likely to be the main reason leading to the increase of the average spring NDVI in the research area, which was the important signal that the vegetation changes response to global warming.Thirdly, climate in different regions has different effects on vegetation while the sensitivity of vegetation to climate is also different. The correlation coefficient between NDVI and precipitation and temperature changes along with altitude elevation. There is an obvious boundary between positive correlation areas and negative correlation areas.Finally, different types of the vegetation showed the different sensitivity to precipitation and temperature. With regard to the facilitation of precipitation to the three kinds of vegetation, farmland is greatest, and meadow greater than forestland. To the facilitation of the temperature in spring, forestland is the greatest, and farmland is greater than meadow. And to the inhibition of temperature in summer, farmland is the greatest, and forestland is greater than meadow.
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