放牧对短花针茅荒漠草原主要植物种群及群落地上现存量稳定性的影响

Study on Aboveground Biomass and Vegetation Stability of Main Plant Populations and Community in Stipa breviflora Desert Steppe

对荒漠草原主要植物种群和群落地上现存量及其比例关系进行研究以探讨放牧对荒漠草原的影响,结果表明:放牧对主要植物种群和群落地上现存量的影响大于对其比例关系的影响,放牧区3个主要植物种群地上现存量占群落地上现存量的比例最高可达94.40%;受放牧影响,主要植物种群对群落稳定性的主导作用变为决定作用;放牧对建群种短花针茅的影响强烈,导致其对水分的需求表现更为强烈,同时对高温的耐受性下降。自由放牧导致荒漠草原退化的原因可归结为:自由放牧使主要植物种群及群落对降水的需求程度和对高温的耐受程度均发生变化,从而导致其对外界干扰的抵抗能力和干扰后的可恢复能力下降,最终表现为群落植被稳定性降低,草地发生逆行演替。

In order to investigate the effects of grazing on the standing crop stability of the main plant population and the community in Stipa breviflora desert steppe,the relationship between the aboveground standing crop and the proportion of the main plant populations and communities in desert grassland was studied.The results were as follows：The influence of grazing on the aboveground standing crop of major plant populations and communities was greater than their effects on their proportion.The proportion of aboveground vegetation in the three main plant populations to the aboveground extant in the community in the grazing area was up to 94.40%.Under the influence of grazing,the dominant effect of the main plant population on the stability of community became decisive.The influence of grazing on Stipa breviflora was strong,it leaded to more strong demand for water,meanwhile,the tolerance to high temperature was also decreased.The reason why free grazing leads to the degradation of desert grassland can be attributed to that free grazing led to changes in the demand for precipitation and the tolerance to high temperature for the major plant populations and communities,thus it leads to its descend of the resistivity to external inter-ference and the ability to recover after interference,finally,the stability of community vegetation was re-duced,retrograde succession occurred in grassland.