若尔盖盆地沙漠化驱动机制

作为世界上最大的高寒泥炭沼泽湿地,若尔盖盆地是黄河水源的重要补给区,素有黄河"蓄水池"之称.作为生态敏感区,在自然环境和不合理的人为活动的影响下,若尔盖盆地出现了湿地萎缩、草场退化、沙地增加等一系列严重的生态环境问题.本文通过分析若尔盖盆地沙漠化现状及其驱动因素,进而阐述和分析沙漠化驱动机制.结果表明:若尔盖盆地广泛分布的古风沙沉积物是现代沙漠化的沙物质来源,地表致密草皮层的机械破坏,使下伏松散的古风沙沉积物暴露,是形成沙漠化的关键一步;随后在风蚀、雨水冲刷及生物因素的共同作用下,松散的古风沙沉积物被侵蚀,引起草皮层坍塌,导致古沙丘活化,风沙活动加剧,形成风沙沉积;若尔盖沙漠化是人为因素与自然因素共同作用的结果,其中人为因素是其主导驱动因素,鼠类活动和热融沉陷、滑塌是沙漠化的诱发因素.

The Driving Mechanism of Sandy Desertification in the Zoige Basin of China

As the world's largest alpine mire wetland, Zoige Basin is an important water recharge area of the Yellow River, known as the Yellow River "reservoir ". As ecologically sensitive areas, under the influence of the natural environment and irrational human activities, the Zoige Basin shows a series of serious environmental problems, such as wetlands shrinking, grassland degradation, sandy land increase, and so on. This paper analyzes the current situation and its driving factors of desertification in the Zoige Basin, and then describes and analyzes the driving mechanism of desertification. The results show that widely distributed fossil dune is the sand supply of the modern desertification. Destruction of turf which contained a dense growth of grass and its matted roots resulting of exposure of underlying loose fossil dune sand sediments is the key step in formation of desertification. As a kind of large-bodied underlying-dwelling rodents, the burrows digging behavior of marmots (Marmota himalayana) play a vital role in destroying surface turf. Marmot burrow sites are usually located in open, herb-covered talus slope. The large opening of burrows is easily collapse by rainfall erosion and other biological factors, causing destroying of turf and exposing loose sand. Another important role that can destroy turf is the thaw subsidence and slump effect, which results from permafrost degradation. The subsidence and slump of surface can form pull crack on the turf around the subsidence pit or slump scarp, leading exposedness of loose sand. The exposed loose sand blown out by wind, resulting of wind erosion pit. With the expansion wind erosion pit, aeolian activities intensified, leading the reactivation of fossil dunes. The reactivation of fossil dunes combined with continuous heavy grazing, leads aeolian deposition in leeward and formation desertification. Principal component analysis showed that desertification is the result of human factors and natural factors work together, where the human factors are the main driving factors.