摘要:沙漠化是玛曲高寒草甸最为严重的生态问题之一，明晰区域内不同沙化阶段植物群落与表土环境因子的关系，有助于为玛曲高寒草甸沙漠化的监测与防治提供科学参考。鉴于此，研究应用方差分析与典范对应分析，厘清了潜在、轻度、中度、重度和极重度沙化阶段植物的组成格局与变化规律，并对其与表土环境因子的关系进行了分析。结果表明：（1）伴随沙漠化的发展，表土水分与电导率呈逐步降低的趋势，下降幅度显著（P<0.05）；温度呈先降低后增加的变化规律，其中轻度沙化阶段最低，为24.32℃，极重度阶段最高，达30.79℃；（2）伴随沙漠化的发展，植物的盖度、多度依次降低，下降幅度显著（P<0.05）；物种丰富度、Shannon-Wiener指数、Simpson指数与Pielou指数的变化趋势相近，呈潜在至轻度阶段上升，之后逐步下降的规律；（3）典范对应分析（CCA）表明，表土水分和电导率对群落组成的影响程度达到极显著水平（P<0.01）。潜在与轻度沙化阶段，CCA前两轴的方差解释率分别是71.91%和55.25%，表土环境因子能够较好的描述植物群落特征与多样性水平的变化规律；中度、重度和极重度沙化阶段，CCA前两轴的方差解释率不足40%，表土环境因子难以有效表征植物群落特征，预示放牧等人类活动在这些演替阶段的影响更为突出。



Abstract:Desertification is one of the most serious ecological problems in the Maqu alpine meadow. It is helpful to provide scientific reference for monitoring and prevention of desertification by understanding the dynamic changes of plant communities and soil surface environmental factors in different desertification stages in this area. Our study clarified the distribution pattern and vegetation changes in potential, slight, moderate, severe and extremely severe desertification stages by sample survey method and the application of variance analysis and canonical correspondence analysis. Furthermore, their relationships with the soil surface environmental factors were explored. The results showed that: (1) with the development of desertification, the soil moisture and conductivity of the soil surface decreased significantly (P<0.05). The soil temperature decreased firstly and then increased, the lowest was in the slight desertification stage (24.32 ℃) while the highest was in the severity stage (30.79 ℃). (2) The coverage and abundance of vegetation decreased significantly with the development of desertification (P<0.05). All the species richness, Shannon-Wiener index, Simpson index and Pielou index showed dynamic increases from potential to slight phase of desertification and then gradually decreased along moderate, severe, and extremely severe desertification stages. (3) The Canonical Correspondence Analysis (CCA) showed that soil surface moisture, temperature and conductivity could explain 31.10% of species composition in communities, and the influence of soil surface water and conductivity on community composition reached extremely significant level (P<0.01). In the potential and slight desertification stages, the variance interpretation rates of the first two axes of the CCA were 71.91% and 55.25%, respectively. The soil surface environmental factors could better describe the changes of plant community characteristics and diversity levels. In the moderate, severe and extremely severe desertification stages, the variance interpretation rate of the first two axes of CCA was less than 40%. The soil surface environmental factors were difficult to effectively reflect the plant community characteristics, indicated that the impact of grazing and other human activities in the middle and late stage of the sanding succession was more prominent.





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