锡林郭勒盟植被物候枯黄期对干湿变化的时间多尺度响应

基于全球监测与建模组(GIMMS)1982～2015年第三代归一化植被指数(NDVI)GIMMS NDVI 3g数据集和气象观测数据,采用累计NDVI的Logistic曲线曲率极值法提取锡林郭勒草原植被枯黄期,并结合不同时间尺度标准化降水蒸散指数(SPEI)分析植被枯黄期对干湿变化的响应特征.结果表明:1982～201...

Response of phenological vegetation wilting period to multi-scale drying-wetting changes in Xilingol

Based on the third generation《Global Inventory Monitoring and Modelling Studies》(GIMMS) and the《Normalized Difference Vegetation Index》(NDVI) (1982~2015), this study extracted vegetation EOS (End of Growing Season) data in Xilingol grassland from 1982 to 2015, and analyzed its responses to multi-scale drying-wetting changes derived from the Standardized Precipitation Evapotranspiration Index (SPEI). The results showed that during 1982~2015, the EOS of Xilingol vegetation was 265~280 d, and delayed from northeast to southwest, with a decreasing trend of -0.14 d/a. Generally, the interannual variation in spatially averaged SPEI tended to decrease at -0.10d/10a. In addition, an increasing trend was mainly observed in the northeastern meadows, and a decreasing trend was observed in the southwestern desert grasslands. Over the past 34 years, the frequency of drought in Xilingol has increased, with the large areas experiencing the light to mid-droughts. The sudden change to frequent droughts occurred in the 1990s. There were significant spatial differences in the impacts of multiple SPEI time scales on EOS. In detail, the positive effect of monthly SPEI-1(Index for one month data) on vegetation EOS in the Xilingol was the greatest, suggesting that grassland vegetation EOS could be delayed in a favorable dry-wet environment over a short time scale. The SPEI-3, SPEI-6, SPEI-9, and SPEI-12(Index for many months data), however, had relatively large negative correlations with EOS, indicating that the long-term changes in the drying conditions could advance grassland EOS in Xilingol. The time-lag effect of SPEI-1 in the Xilingol mainly occurs two months before EOS. The long-term SPEI-3, SPEI-6, and SPEI-9 (especially SPEI-3), which are accumulated to June, have particularly considerable lag effects.