青海湖高寒草原植被群落结构和水源涵养功能对禁牧封育的响应

Response of plant community structure and soil water conservation function to forbidden grazing and enclosure in alpine steppe of the Qinghai Lake

【目的】探讨禁牧封育对青海湖植被群落结构和水源涵养功能的影响,对准确评估禁牧封育在青海湖退化草地恢复过程中的作用具有重要意义。【方法】对青海湖北岸高寒草原设置自由放牧及不同封育年限样地,分析封育措施对植物物种数、生物量、功能群、土壤容重、持水量及孔隙度等指标的影响。【结果】(1)随封育年限延长,青海湖北岸高寒草原物种数呈降低趋势,植被盖度、地上地下生物量均呈先增加后降低趋势,禾本科植物在群落中的重要值占比逐渐增加。(2)禁牧封育对青海湖北岸高寒草原土壤水分特征的影响主要集中在0—20 cm。随禁牧封育年限延长,0—20 cm土壤容重逐步降低,0—10 cm土壤饱和持水量、毛管持水量、田间持水量及总孔隙度均呈先增加后稳定趋势。(3)土壤容重是影响青海湖北岸高寒草原植被群落结构的最主要土壤水分特征因子。【结论】从植被群落结构的角度考虑,青海湖高寒草原禁牧封育年限不应超过7年,超过7年应进行适度干扰。

[Objective]This study aims to explore the impact of grazing enclosure on plant community structure and soil water conservation function in alpine steppe in the Qinghai Lake region,and to evaluate the effects of grazing enclosure on the restoration of the degraded grassland in Qinghai Lake.[Methods]By setting up free grazing and different years of enclosure in the alpine grassland on the north bank of the Qinghai Lake,we analyzed the effects of enclosure measures on plant species,biomass,functional groups,soil bulk density,water holding capacity,porosity,and other indicators.[Results](1)With the increas-ing of enclosure time,the number of species in the alpine steppe was decreased,the vegetation cover,above-ground biomass,and below-ground biomass were first increased and then decreased.The percentage of grasses in the community was gradually increased.(2)The effects of grazing exclusion on soil moisture characteristics of alpine steppe were mainly concentrated in the 0-20 cm depth.With the increase of graz-ing exclusion time,soil bulk density at 0-20 cm was decreased gradually,soil saturated water holding ca-pacity,capillary water holding capacity,field water holding capacity,and total porosity at 0-10 cm was first increased and then stabilized.(3)Soil bulk density was the most important soil water characteristic factor affecting the vegetation community structure in the alpine steppe.[Conclusion]From the view of vegetation community structure,the grazing exclusion time in the alpine steppe in Qinghai Lake may not exceed 7 years,and moderate disturbance might be allowed after 7 years of grazing exclusion.