近40 年来青藏高原典型高寒湿地系统的动态变化

选择青藏高原长江源区、黄河源区以及若尔盖地区等典型高寒湿地分布区域,利用1969、1986、2000和2004年多期航片和卫星遥感数据,从湿地主要组分分布、空间格局以及水生态功能等方面,分析了近40年来典型高寒湿地系统动态变化特征及其区域差异性、结果表明:青藏高原典型高寒湿地退化具有普遍性,湿地面积萎缩在10%以上.以长江源区的沼泽湿地退化最为严重,退缩幅度达到29%,同时大约有17.5%的长江源区内流小湖泊干涸消失,黄河源区和若尔盖地区湿地系统空间分布格局的破碎化和岛屿化程度显著加剧.高寒湿地系统退化使其水文功能发生变化,表现在湿地退化较为强烈的长江源区与若尔盖地区枯水期流量减少、稀遇较大流量径流发生频率增加而常遇流量发生频率减少、水涵养能力下降.湿地系统变化与区域气温显著升高有关,在20世纪80年代以来区域增温幅度升高到过去40年平均增温幅度的2.3倍,湿地系统退化程度也同步在20世纪80年代中期以后明显加剧.在降水量呈现增加以及冰川趋于消融的背景下,高寒湿地退化是导致其流域径流持续递减的主要因素之一.

Typical Alpine Wetland System Changes on the Qinghai-Tibet Plateau in Recent 40 Years

The wetlands in the source regions of the Yangtze and Yellow rivers and the Zoige wetland were selected as the typical wetland systems on the Qinghai-Tibet Plateau. This study evaluated changes in wetland components,spatial pattern and hydro-ecological function of the typical wetlands on the Qinghai-Tibet Plateau on the basis of three sets of remote sensing data (1969,1986 and 2000) and field investigations. In recent 40 years,the degradation of wetlands on the Qinghai-Tibet Plateau was prevailing with the declining area exceeding 10%. Among the three typical wetland systems,the most serious wetland degradation took place in the source region of the Yangtze River,and wetland area decreased by 29% and dried-up area of the lakes by 17.5%. The fragmentation and island of wetlands in the source region of the Yellow River and the Zoige region were accelerated. The degradation of the alpine wetlands resulted in the changes of their hydrological functions. In the source region of the Yangtze River and the Zoige region,where the wetlands declined more severely,the low water runoff decreased,the frequency of rare larger runoff increased and the frequency of regular runoff decreased. The water regulation capacity of all the wetlands was declined. The wetlands degradation was related with the air temperature rise. Under the air temperature rise by 2.3 folds of the average increasing magnitude during recent 40 years,the degradation of wetland systems was accelerated after the mid-1980s. Since the precipitation increased and glacier thawed,the wetland degradation was the main cause for river runoff decrease.