[目的]为探究草原不同放牧强度下植被群落的改变,解析群落特征变化对土壤团聚体的影响.[方法]以希拉穆仁荒漠草原控制放牧试验区为研究对象,采用野外调查、室内分析相结合的方法,分析轻度放牧(LG)、中度放牧(MG)、重度放牧(HG)和禁牧(CK)下植被群落特征和土壤团聚体特征及二者的关系,揭示植物群落变化对土壤团聚体的影响.[结果](1)植物群落物种数随放牧强度的增加而增加,LG的群落Shannon-Wiener多样性指数(H')和Simpson优势度指数(D)显著低于其他放牧强度(p＜0.05).地上生物量随放牧强度的增加而降低,HG的地上生物量显著低于其他放牧强度(p＜0.05).不同放牧强度下地下生物量差异显著,且不同土层的地下生物量均以LG最高.(2)平均重量直径(MWD)和几何平均直径(GMD)的变化趋势与大团聚体含量一致,在0-5,5-10 cm 土层表现为随放牧强度的增加先增加后降低再增加(LG最高、MG最低).(3)群落Shannon-Wiener多样性指数(H')、Pielous均匀度指数(J')、地上生物量、容重是影响大团聚体含量、MWD和GMD的显著性因子(p＜0.05).[结论]放牧强度对土壤团聚体稳定性具有负反馈调节作用,主要通过影响植被群落多样性指数(H'和J')、地上生物量、土壤容重的变化而引起土壤团聚体稳定性的变化.该结果为希拉穆仁草原放牧强度选择及生态恢复工作提供理论支撑和科学依据.
Effects of Different Grazing Intensities on Vegetation Community Characteristics and Soil Aggregates in Xilamuren Grassland
[Objective]In order to explore the changes of vegetation communities under different grazing intensities in grassland,the effects of community characteristics on soil aggregates were analyzed.[Methods]Taking the controlled grazing experimental area of Xilamuren desert steppe as the research object,the characteristics of vegetation community and soil aggregates under light grazing(LG),moderate grazing(MG),heavy grazing(HG),and no grazing(CK)and their relationship were analyzed by field investigation and indoor analysis,and the effects of plant community changes on soil aggregates were revealed.[Results](1)The Shannon-Wiener diversity index(H')and Simpson dominance index(D)of LG were significantly lower than those of other grazing intensities(p＜0.05).The aboveground biomass decreased with the increase of grazing intensity,and the aboveground biomass of HG was significantly lower than that of other grazing intensities(p＜0.05).The underground biomass under different grazing intensities was significantly different,and the underground biomass of different soil layers was the highest in LG.(2)The change trend of mean weight diameter(MWD)and geometric mean diameter(GMD)was consistent with the content of macroaggregates.In 0-5 cm and 5-10 cm soil layers,it increased first,then decreased and then increased with the increase of grazing intensity(LG was the highest and MG was the lowest).(3)Shannon-Wiener diversity index(H'),Pielous evenness index(J'),aboveground biomass,and bulk density were significant factors affecting macroaggregate content,MWD,and GMD(p＜0.05).[Conclusion]Grazing intensity had a negative feedback regulation effect on soil aggregate stability,which mainly caused the change of soil aggregate stability by affecting the changes of vegetation community diversity index(H'and J'),aboveground biomass,and soil bulk density.The results provide theoretical support and a scientific basis for the selection of grazing intensity and ecological restoration in Xilamuren grassland.
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