荒漠河岸生态系统退化机理的定量分析

通过野外监测资料，采用聚类分析与主成分分析法，分析了荒漠河岸生态系统退化的内外因素与驱动力、植被退化的环境主导因子与生态退化程度，结果表明：（1）地质、地貌与气候条件等因素的影响，塔里木河下游生态系统存在脆弱和不稳定性是其退化的内因，外界干扰则是其退化的外在因素。人为干扰则是其退化发生的驱动力，起因于人口的增加、需求的增长。（2）在此过程中导致植被受损的环境主导因子是水，植被退化是人类干扰作用于植被赖以生存的环境主导因子所致。（3）其不同河段的生态退化可以归为三类：潜在沙漠化类（轻度退化），轻度沙漠化类（中度退化），中度或重度沙漠化类（重度退化），其中第三类型，土壤条件与其它两类差异较大，表现出土壤退化的滞后现象。

Quantitative analysis of the degradation of desert riparian ecosystem

The Tarim River, the longest inland river of China, runs in a specific region--the extreme dry area of the Taklimakan De- sert. Natural vegetation in the Tarim River basin plays a very important role both in conservation of biodiversity and reduction of desertification. During the past 50 years, human activities related to water resource development have significantly changed natural ecological processes of the Tarim River watershed, especially the lower reaches from Daxihaizi Reservoir to Tatema Nor. In order to reveal the driving force of degradation and the degree of plant communities degradation, 11 representative sections were chosen, and 42 plant plots were built. Based on analysis of 11 groundwater-monitoring sections with 58 monitoring wells and the statistical data of plant plots in the lower reaches of Tarim River during 2000-2006a, the driving force of vegetational degradation, ？ _ and the degree of degradation in the lower reaches of the Tarim River were analyzed. The result showed： （1） The vulnerability and instability of ecosystem in the lower reaches of the Tarim River, as a result of the interaction of its geological, geomorphological and climatic conditions and other factors, were the internal factors of ecological degradation, then, the disturbance were external factors of its degradation. The driving forces of its degradation were the intense human activities due to population growth, demand growth. （2） In this process, water factor was the dominant ecological factor to lead vegetation degradation. In other words, the dominant eco- logical factors of vegetation survival were changed by the intense human activities, Finally, riparian vegetation degraded. （3） The degraded ecosystem at the study area could be divided into three types by the Cluster Analysis namely the slight degradation, the serious degradation and the intergrade degradation. The soil texture of serious degradation were different from those of other types, Displayed the hysteresis of soil degradation as a result of desertification.