近23年来青藏高原东北部香日德地区高寒草甸上界变化及其与气候变化关系研究

Research on the Upper Boundary Change of Alpine Meadow and Its Relationship with Climate Change During the Past 23 Years in Xiangride,in Northeast Tibetan Plateau

利用1990年、1999年、2013年的Landsat卫星遥感影像数据,通过遥感和GIS技术,运用非监督分类和目视解译相结合的方法,提取香日德地区的高寒草甸上界,分析其变化特征及其与该地区气候变化的关系。结果显示：（1）1990—1999年升温趋势显著,降水量基本保持不变;1999—2013年气温基本不变而降水呈显著增加的趋势。（2）香日德地区高寒草甸上界呈现向更高海拔即原高寒荒漠的范围扩张的趋势,其上界的扩张受气温和降水变化的共同作用。其中以气温变化为主导的1990—1999年期间,高寒草甸面积扩张迅速;以降水变化为主导的1999—2013年期间,高寒草甸上界扩张减慢。并且海拔越高的地区高寒草甸面积增加越迅速。（3）高寒草甸上界在不同坡向上均有扩张。其中,以升温为主导的1990—1999年主要集中在北坡与西坡;以降水量增加为主导的1999—2013年期间则主要集中在南向坡。（4）从坡度分布来看,1990—1999年高寒草甸上界的扩张主要发生在15°-25°,而1999—2013年为20°-35°。

We adopted the unsupervised classification and visual interpretation to extract upper boundary of alpine meadow in Xiangride by using remote sensing images of 1990, 1999 and 2013 to summarize the change characteristics and analyze its relationship with climate change. The results showed that： （1） the temperature had a significant increasing trend and the precipitation remained unchanged from 1990 to 1999; the temperature remained unchanged and the precipitation increased significantly from 1999 to 2013. （2） the upper boundary change of alpine meadow was controlled by both temperature and precipitation, the alpine meadow expanded in higher region in the past 23 years, the area increased fast from 1990 to 1999 which was controlled by temperature change, the area increased slowly from 1999 to 2013 which was controlled by precipitation change. （3） the upper boundary of alpine meadow increased in all slope aspects, alpine meadow increased mainly in north and west from 1990 to 1999 which was controlled by temperature, and it increased in southern slope aspect from 1999 to 2013 which was controlled by precipitation. （4） according to the distribution of slope gradient changes, the expansion of the upper boundary of the alpine meadow in 1990 to 1999 mainly occurred in steepness of 15°-25°,and the expansion in 1999--2013 mainly occurred in gradients of 20°-35°.