毛乌素沙地东南缘沙漠化过程中植被的退化和稳定性

目的]揭示毛乌素沙地东南缘沙漠化过程中植被退化及其稳定性变化机制,为沙漠化修复和治理提供科学依据。方法]综合应用野外调查、取样、室内试验和统计分析相结合的多种方法,对研究区沙漠化过程中植被特征变化进行分析。结果]结构和功能特征中,植被盖度、密度、物种丰富度、多样性指数均呈下降趋势,地上生物量呈现先升高后降低趋势;营养特征中,有机质含量变化规律并不明显,全氮含量在沙漠化进程中逐渐降低,C/N不断升高;且轻度沙漠化阶段植被特征发生突变,是沙漠化逆转的关键阶段。对植被稳定性定量测度结果认为,沙漠化过程中,植被稳定性指数不断降低,稳定性等级非沙漠化阶段和潜在沙漠化阶段为稳定和基本稳定,轻度沙漠化阶段开始均处在不稳定状态。结论]沙漠化过程伴随着植被的退化和植被稳定性程度的降低,维持土壤—植被系统的良性循环是植被恢复的关键,也是沙漠化治理的关键。

Vegetation Degradation and Its Stability in Desertification at Southeastern Edge of Mu Us Sandy Land

Objective] To analyze the mechanisms of vegetation degradation and stability maintenance during the process of desertification at the southeastern edge of Mu Us sandy land, and to provide scientific basis for the repairing and controlling of desertification.Methods] The methods of field investigation, field sampling, indoor assay and statistical analysis were integrated to analyze the change of vegetation characteristics during desertification in the study area.Results] The results of functional and structural characteristics showed that the vegetation coverage, density, richness and Simpson diversity index reduced; The aboveground biomass increased first and then decreased. The changing regularity of organic matter was not obvious, while the total nitrogen content decreased and C/N increased. Vegetation characteristics changed suddenly in the mild desertification stage which was the key stage for desertification repairing. Furthermore, the quantitative measurement of vegetation stability showed that the stability index decreased in the process of desertification, stable and basically stable in non-desertification stage and potential desertification stage, unstable in other stages.Conclusion] The vegetation degrades and the stability indexes decrease with desertification deepens. Therefore, maintain the virtuous circle of plant-soil system is the key of vegetation restoration and desertification control.