中文摘要：

利用1982～1997年的气温、降水和1983～1997年生长季的NOAA/AVHRR的归一化植被指数（Normalized differential vegetationindex,NDVI）遥感数据,分析了中国北方温带草原植被生长对气象因子的时滞响应。根据4个时间尺度（1～4个月）和4个时滞期（前0～3个月）将降水数据进行16种组合方式,计算了植被的NDVI与同期及前期（前1～6个月）降水之间的相关系数。同时,计算了植被的NDVI与同期和前一个月气温之间的相关系数。结果表明：1）中国北方温带草原植被的NDVI与同期降水和气温的显著相关。2）植被的NDVI对前一个月降水的时滞响应最强烈,植被的NDVI与当月降水和前两个月降水的累积量相关性最强。3）在生长季的起始阶段,去冬、今春的降水总量对草甸草原植被的生长有重要的作用。在生长季的中期和后期,当月和前一、二个月的降水对典型草原和荒漠草原的植被有显著影响。4）在草甸草原、典型草原区,生长季早期的气温均对植被生长的影响较为显著。在荒漠草原区,气温不仅在生长季初期与植被的NDVI呈现正相关,而且在生长季的中后期,气温与植被的NDVI呈现负相关性。

英文摘要：

Aims Vegetation has strong temporal response to climate variables in some regions.The normalized differential vegetation index（NDVI）is generally recognized as a good indicator of terrestrial vegetation,so it can be used to analyze temporal responses of vegetation to climate variables.This study addresses two key questions：a）How quickly and over what time period does NDVI respond to different patterns of climate variables？ b）How does NDVI respond to weather variation for different temperate steppe types of northern China？Methods We calculated 1）linear correlations between monthly climate variables and NDVI for 1983-1997,2）NDVI-precipitation correlation coefficients,with precipitation in four different time periods（1-4 months）and four different time lags（0-3 month lags）to evaluate the time period over which precipitation most strongly influences on NDVI and 3）NDVI-temperature correlation coefficients for the current and previous month.Important findings The correlation coefficients between NDVI and concurrent climate variables were all significant in three temperate steppe types.There is a strong relationship between precipitation and NDVI in temperate steppe of northern China.Correlation coefficients between NDVI and precipitation are high for specific combinations of time duration and lag.In terms of time lag,NDVI was most strongly related to the previous month,although differences existed among different steppe types.In terms of time duration,NDVI was most strongly related to the sum of precipitation over three months than one,two or four month periods.Precipitation from February back to November of the previous year was positively correlated with NDVI early in the growing season in meadow steppe,and there was a strong correlation between NDVI and precipitation for the preceding 1-2 months in the mid and late growing season in desert steppe and typical steppe.Temperature was moderately correlated with NDVI during the growing season,but differences existed among steppe types.For typica