高寒草原退化对植物群落及土壤理化性质的影响

Effects of alpine steppe degradation on plantcommunities and soil physical andchemical properties

摘要:

以空间分布代替时间演替的方法,调查黄河源区玛多县高寒草原退化过程中植物群落特征和土壤理化特性的变化,探讨植物群落与土壤理化特性对退化的响应。结果表明:(1)不同退化梯度下植物优势种变化明显,从轻度退化到重度退化,草地优势种由紫花针茅和矮嵩草逐渐向杂类草转变,极度退化下变为沙生植物为主;(2) 随着草地退化加剧,植物物种重要值、丰富度、多样性、均匀度以及地上生物量均呈先增加后降低的趋势,但轻度退化草地地上生物量比未退化草地高21.5%,其与不同物种在退化演替过程中的消长变化密切相关;(3) 土壤有机质、全氮、全磷以及pH表现出随退化程度加剧呈显著降低(P＜0.05)的趋势。土壤容重随退化程度加剧而显著增加,土壤通气孔隙度随退化程度加剧而显著降低。通过分析,草地退化首先影响土壤物理属性,进而影响草地群落物种组成,导致草地生产力明显降低。

Abstract:

The alpine steppe is an important part of the grassland ecosystem in the Qinghai-Tibet Plateau.It is important to understand the effects of alpine grassland degradation on plant community and soil physical and chemical properties.In this study,spatial distribution was used instead of time succession to investigate the changes of plant community characteristics and soil physical and chemical properties during the degradation of alpine steppe in Maduo County,Yellow River source area,and to explore the response of plant community and soil physical and chemical properties to degradation.The results showed: (1) The dominant species of plants under different degradation gradients changed significantly,from mild to severely degraded.The dominant species of grassland changed from the genus Stipabreviflora and Kobresia to the heterotic grass,and the dominant species became sandy plants under extreme degradation.(2) With the increase of grassland degradation,the importance value,richness,diversity,evenness and aboveground biomass of plant species increased first and then decreased,but the aboveground biomass of slightly degraded grassland was 21.5% higher than that of non-degraded grassland.The reason may be closely related to the change of growth and decline of different species in the process of degraded succession.(3) Soil organic matter,total nitrogen,total phosphorus and pH showed a significant decrease (P＜0.05) with the degree of degradation;soil bulk density increased significantly with the degree of degradation;soil aeration porosity decreased significantly with the degree of degradation.Through redundant analysis,grassland degradation first affects the physical properties of the soil and then affects the species composition of the grassland community,resulting in a significant decrease in grassland productivity.