若尔盖沼泽湿地的萎缩机制

1960年以来，若尔盖沼泽湿地的快速萎缩严重影响黄河上游水量补给和当地湿地生态系统，但其机制尚不清晰。基于2010—2013年野外调查、气象水文资料和遥感影像，分析若尔盖沼泽退化的主要原因与机制。尽管气温的缓慢升高，但降水量并未减少，考虑到沼泽的季节性特征，气候变暖对沼泽萎缩影响相当有限，但不是主要原因。经遥感判读和统计，共识别现有920 km的人工渠道，其疏干的沼泽面积约648.3 km2，占总萎缩面积的27%。人工开渠作为强烈的人类活动干扰，是若尔盖沼泽快速萎缩的重要原因。自然水系的溯源侵蚀长期疏干沼泽、降低地下水水位和放射状地向沼泽内部切穿是沼泽萎缩的重要机制。人工开渠连通自然水系强化沼泽内河床下切和排水作用。

A study on the mechanism of wetland degradation in Ruoergai swamp

The Ruoergai swamp had been experiencing a rapid degradation since 1960s. However, the mechanism causing the degradation in Ruoergai swamp remains unclear, as a few studies concerning the issue can be found. The rapid degradation of swamp affects the wetland ecosystem and causes a reduction of flow rate draining into the upper Yellow River. In this study, we investigate the mechanism using the combined approach of field studies conducted in 2010-2013, and analyzing meteorological and hydrological data and remote sensing images. Results show that climate change may not be the main cause of the wetland degradation as the overall amount of annual precipitation remains steady in spite of a slow rise in temperature in the past 50 years. The analysis of remote sensing images reveals that there exists an artificial drainage system with a total length of 920 km developed for animal husbandry purposes. Water is thus drained from wetlands by the system, which causes a reduction of 648.3 km² in Ruoergai swamp, accounting for up to 27% of the wetland degradation. Therefore, excavated artificial ditches as an intense disturbance of human activity are an important reason on rapid shrinkage of swamp. Headcut erosion of countless tributaries inside the swamp continuously draining water, lowering groundwater water level and cutting into the inside of swamp, is another important natural degradation mechanism. Connection of artificial channels and natural river networks strengthens the effect of riverbed incision and drainage.