2000-2010年黄河源玛曲高寒湿地生态格局变化

玛曲湿地作为黄河上游重要的水源涵养以及补给区之一，对于调节黄河水量与泥沙量、维持生物多样性和区域生态平衡以及实现社会经济的可持续发展具有重要意义。为揭示和分析近10 年来玛曲高寒湿地系统动态变化特征及其区域差异性，应用2000 年、2010 年两期Landsat TM卫星影像提取玛曲景观类型信息，对玛曲湿地分布格局变化进行分析；利用S-G 滤波以及最大值合成法处理后的2000-2010 年MODIS归一化植被指数（NDVI）数据，进行一元线性回归分析，模拟湿地生态系统的空间演变趋势；运用长期气候观测数据，采用最小二乘法对玛曲湿地变化与气候之间的相关关系进行分析与探讨。结果表明：近10 年来玛曲夏季年际NDVI值呈现波动减小的趋势，“黄河第一弯”玛曲腹地的阿万仓处NDVI减少明显，且存在沼泽草甸向亚高山草甸类型转化趋势。另外，玛曲高寒湿地变化与降水量及温度的年际变化均有关系，但与降水量的相关关系更强。

Changes in ecological patterns of Maqu alpine wetland in Yellow River Source Area during 2000-2010

Wetland as a unique ecosystem has important environment regulating functions and irreplaceable role in maintaining regional ecological balance, conserving biodiversity, and providing food, materials and water resources to humans. The Maqu alpine wetland located in the northeast of the Tibetan Plateau is an important water conserving and supplying area to the upper reach of the Yellow River. In the past 30 years, global warming has led to significant vegetation changes on the Tibetan Plateau. The Maqu alpine wetland is undergoing a process of prominent warming and drying, and degradation of its water conservation function is very significant in recent years. Wetland vegetation dynamics , regional differentiation and causes of degradation of the alpine wetland ecosystem were investigated using multi-source remote sensing data in this study. Land use information and ecological patterns of Maqu were extracted via analyzing Landsat-5/TM and Landsat-7/ETM+ satellite images of 2000 and 2010, through visual interpretation and supervised classification using GIS techniques. NDVI (Normalized Difference Vegetation Index) was used as an indicator in monitoring vegetation changes. MODIS NDVI time series data of 2000-2010(after applying the S-G filtering method and MVC) were used to detect temporal and spatial variations and evolution trend of wetland ecosystems. Point data from weather stations was interpolated using Kriging interpolation method. Based on long-term observations from weather stations，the relationship between Maqu wetland changes and climatic factors(temperature and precipitation) was examined using the least squares method. The results show that areas of rivers, inland beaches, ponds, and swamp meadows were decreasing. Summer NDVI of 2000-2010 in the study area also decreased. Areas with significant decline in NDVI are located in Cairima, Manrima and Hequmachang. Changes in vegetation type also occurred, as signified by swamp meadows shifting to subalpine meadows. The warming and dry climate appears to be a critical factor contributing to the degradation of the Maqu alpine wetland. The changes of the Maqu alpine wetland are related to the inter-annual variability of precipitation and temperature, with 61% and 51% of the total area showing a positive correlation between NDVI and annual precipitation as well as between NDVI and mean temperature respectively. A stronger correlation exists between NDVI and annual precipitation, indicating that the vegetation growth is more sensitive to the inter-annual variability of precipitation.