放牧强度对西藏高寒草甸植被群落和土壤理化性质的影响

Effects of grazing intensity on vegetation community and soil physicochemical properties of alpine meadow in Tibet

【目的】研究放牧强度对高寒草甸植被群落和土壤理化性质的影响，为西藏高寒草甸科学放牧和退化草地生态系统的恢复提供科学依据。【方法】于2010-06-2012-08在西藏邦杰塘高寒草甸开展牦牛放牧控制试验，设置对照（零放牧）、适度放牧和重度放牧3个处理，研究不同放牧强度对植被群落丰富度、均匀度、生物量、盖度、密度、高度和土壤理化性质的影响。【结果】随放牧强度的增加，植被群落的丰富度和总盖度降低，均匀度指数和地上、地下生物量均先增大后减小；高山嵩草和紫花针茅的盖度和高度随放牧强度的增加而降低，密度增大。高寒草甸生态系统中土壤的体积质量和硬度随放牧强度的增加而增大；0～10 cm土层土壤总孔隙度随放牧强度的增加而增大，10～20和20～30 cm土层总孔隙度变化规律不明显；土壤含水量在0～10 cm土层以适度放牧区最高，但各处理间无显著差异（P＞0.05）；随放牧强度的增加，土壤有机质、全氮、速效氮含量以及pH均显著减小（P＜0.05），速效钾含量在0～10和10～20 cm土壤中先增加后减少，速效磷变化无明显的规律性。【结论】重度放牧是高寒草甸植被退化、土壤理化性质改变的主要因素。围栏封育可作为高寒草地植被短期恢复的最佳方式。适度放牧有利于植被群落的增多和改善土壤理化性质。

【Objective】To provide scientific basis for grazing and restoration of alpine degraded grassland in Tibet,this study investigated the effects of grazing intensity on vegetation community and soil physical and chemical properties.【Method】The experiment of yak grazing was carried out from June 2010 to August 2012 in beginning alpine meadow in Tibet.Three treatment,heavy grazing,moderate grazing and no grazing as control,were set to researched the effects of different grazing intensities on richness,homogeneous degree,biomass,coverage,density,and height of vegetation community and soil physicochemical properties.【Result】With the increase of grazing intensity,evenness and biomass of vegetation community increased while richness and total coverage decreased.The homogeneous degree index and the biomass of the ground or the underground is increased firstly then decreased.The coverage and height of alpine wormwood and purple flowers.grandis decreased while the density increased.The density and the hardness of soil in alpine meadow ecosystem in-creased along with the grazing intensity.Toal porosity of soil increased in layer of 0-10 cm,while it did not change significantly inlayers of 10-20 cm and 20-30 cm.The highest water content in soil was found in soil layer of 0-10 cm in moderate （P＞0.05）.With the increase of grazing intensity,Soil organic matter,total nitrogen,available nitrogen,available phosphorus and pH significantly decreased （P＜0.05）,the available K content in 0-10 cm and 10-20 cm soil decrease after the first increase,and the available phosphorus no significant changes in regularity.【Conclusion】Heavy grazing was the main reason for degradation of alpine meadow and change of soil physical and chemical properties.Fencing was the best way to recover vegetation of alpine meadow in short-term.Moderate grazing was beneficial to the increase of vegetation and improvement of soil physical and chemical properties.