气候变化背景下近15 a乌梁素海流域植被动态变化

Dynamics of Vegetation in the Wuliangsuhai Basin Under Climate Change During the Years From 1999 to 2013

以内蒙古乌梁素海流域为研究对象,利用SPOT-VGT NDVI、数字高程模型(DEM)和气象数据,分析了1999—2013年流域植被覆盖变化及其海拔效应,并结合年平均气温和年降水量变化,探讨了流域植被变化对气候变化的响应。结果表明,乌梁素海流域植被覆盖度总体较低,NDVI多年平均值仅为0.213;1999—2013年乌梁素海流域94.8%的区域植被覆盖呈明显增加趋势,2013年NDVI年平均值比1999年增加22.4%;乌梁素海流域的植被覆盖表现为随高程增加而减少的趋势,1999—2013年NDVI年变化率随高程的变化趋势显著,仅在海拔梯度1 000 m处出现显著减小趋势(Mann-Kendall检验的统计值Z<-1.64),在其余海拔高度均呈显著增加趋势(Z>1.64);1999—2013年乌梁素海流域NDVI年平均值变化与年降水量呈显著正相关(P<0.05),与年平均气温呈负相关(P>0.05)。

Based on the SPOT-VGT normalized difference vegetation index （NDVI） dataset,SRTM digital elevation model （DEM）,and metrological data accumulated during the years from 1999 to 2013 in four observatory stations in the Wuliangsuhai Basin, Inner Mongolia, analyses were performed for interannual changes in vegetation coverage in the region and their elevation effect,and at the mean time exploration was done of responses of the vegetation to climate changes through comparing changes in annual mean temperature and annual precipitation. Results show that （1） on the whole, the basin was quite low in vegetation coverage,with a multi-year mean of NDVI being 0. 2 1 3; however,vegetation cover-age in 94. 8% areas of the basin exhibited an apparent rising trend,and the trend in 51. 8 % areas of the region passed the 99% confidence level （a statistical variable calculated by the non-parametric Mann-Kendall test of Z〉2. 32） ; and the annual mean NDVI was 22. 4% areas in 2013 than in 1999; （2） vegetation coverage in the region declined with rising elevation and annual NDVI change rate also varied significantly with elevation, exhibiting a declining trend around 1 000 m in elevation and rising trends in all the others; and （ 3） variation of annual mean NDVI in the region was significantly and positively related to annual mean precipitation （ P 〈0.05）,but negatively to annual mean temperature （ P〉0.05）.