放牧强度对三江源典型高寒草甸生物量和土壤理化特征的影响

Effects of grazing intensity on biomass and soil physical and chemical characteristics in alpine meadow in the source of three rivers

为了揭示高寒草甸生态系统在放牧扰动下的植被和土壤特征变化,通过野外样地调查和室内分析法研究和探讨围栏封育(EN)、轻度放牧(LG)、中度放牧(MG)、重度放牧(HG)、对照区(CK)几种不同放牧强度对草地生物量和土壤碳特征的影响,为高寒草甸的退化研究提供依据。结果表明,封育区地上生物量和地下生物量最高,随着放牧强度的增加,草地地上生物量和地下生物量均呈减少趋势;放牧干扰对高寒草甸土壤湿度也产生影响,其中封育区和轻牧区土壤湿度显著高于其他处理(P<0.05);在土壤剖面上,随着土层深度的增加土壤湿度呈明显降低趋势;放牧的践踏作用不仅影响土壤湿度,而且随着放牧强度的增加土壤容重增加;土壤全氮和土壤有机碳也对放牧有一定的响应,土壤全氮表现为LG>EN>MG>CK>HG,土壤有机碳从高到底为LG>EN>MG>HG>CK。草地受到放牧干扰时,适度的践踏干扰将提高草地生产力和碳固存,但是高强度的放牧对草地植被和土壤结构的干扰作用不利于草地生态系统的可持续发展。

Human activity has adversely affected global carbon(C) and nitrogen(N),and contributed to an alteration of climate that will generate discernible feedbacks to all organisms and ecosystems on earth.The purpose of this study was to provide the basis of degrading mechanisms in alpine meadow research and understanding global C reserves and quantifying the pools and changing of soil carbon under grazing intensity.The combined methods of field survey and experiment analysis were applied to detect the influence of biomass and soil carbon characteristics under different grazing intensity:enclosure(EN),light grazing(LG),moderate grazing(MG),heavy grazing(HG)and control(CK) on an alpine meadow.The experiment plots were located in the Yushu Longbao alpine meadow.The results showed that aboveground biomass and underground biomass of grassland were maximum in EN treatment.With the grazing intensity increasing,the aboveground biomass and underground biomass decreased.The soil moisture in EN and LG treatments were significantly higher(P < 0.05) than the other treatments which influenced by grazing disturbance.In the soil profile,the soil moisture decreased with soil depth increase in all treatments.Trampling of grazed not only influenced soil moisture but also impacted soil bulk density,the soil bulk density increased with the grazing intensity increasing.The soil organic carbon(SOC) and total nitrogen were also influenced by grazing,the total nitrogen decreased in the following order:LG > EN > MG > CK > HG whereas the SOC decreased in the following order LG > EN > MG > HG > CK.Optium trampling of grazing increased soil bulk density,however,but the effects on meadow vegetation and soil structure of high grazing intensity were not benefical for sustainable development of grassland ecosystem.