塔里木河下游荒漠生态系统退化机制分析

近几十年来，塔里木河下游河道断流，地下水水位剧烈下降，天然植被衰退，土地的沙质荒漠化问题十分严峻。通过对下游退化荒漠生态系统的脆弱性和不稳定性以及干扰体驱动力的分析，阐述了该系统退化的机制，并在此基础上，提出了退化荒漠生态系统的恢复对策。系统的内在脆弱性特征决定了其抗干扰的能力差，退化后恢复的弹性小；强烈的人为干扰体是系统退化的重要驱动力。下游荒漠生态系统的退化是系统内在特性和外在干扰体综合作用的结果。在干旱区严酷的生态环境下，荒漠生态系统的人为干扰结果值得重视。2000年5月以来的塔里木河下游生态输水，使系统的退化形式得到了一定程度的遏制，但系统的恢复是有限的。植被的恢复，必须遵循干旱区植物的生态学性质，密切结合植物发生所需的环境条件，特别是干旱区植被分布格局与地下水的关系。

Degradation Mechanism of Desert Ecosystem in Lower Reaches of Tarim River

Over the past decades,zero-flow caused the reduction of groundwater level and the degradation of vegetation,meanwhile,sandy desertification spread seriously in the lower reaches of the Tarim River.Based on the overall review of intrinsic characteristics,natural environment,and their interaction in the special desert ecosystem,this paper firstly discussed some important issues contributed to the desert ecosystem degradation-such as bio-community instability,natural environmental fragility,ecosystem functional limitedness;then analyzed the anthropogenic disturbance regimes happened in the ecosystem in past decades.Its inborn characteristic displayed that the desert eco-system was sensitive to disturbance and has only low resistance to the disturbance and limited resilience of restoration after degradation.The degradation of desert ecosystem was resulted from integration of high natural fragility,intensive human-induced disturbance regime,and their interaction.Since 1950's,the man-induced disturbance regimes have played as an important driving force was responsible for the degradation of the desert ecosystem degradation.The result of human-induced disturbance would be emphasized under rigorous environment in arid area.The restoration of degradation of desert eco-system in the lower reaches of the Tarim River was put forward finally.Since May 2000,the project of ecological transporting water,the result showed that the respond of ground-water was significant.In the vicinities along the river channel,vegetation restoration was evident,but the seedlings were scarce.Vegetation restoration must be follow the ecological feature of vegetation and conform to the theory of vegetal occurrence of inland river in arid zone.