短期牦牛放牧对青藏高原高寒草地土壤真菌群落的影响

Effects of short-term yak grazing on soil fungal communities in an alpine meadow on the Qinghai-Tibetan Plateau

牦牛放牧是青藏高原重要的人为干扰形式,放牧管理方式以及放牧强度对维持草地健康具有重要作用。为了明晰牦牛短期放牧对高寒草甸土壤真菌群落的影响过程,本研究在川西北典型高寒草甸进行牦牛放牧强度试验,设置了对照(禁牧)、轻度放牧(1头牦牛·hm^(-2))、中度放牧(2头牦牛·hm^(-2))和重度放牧(3头牦牛·hm^(-2))4种放牧强度。结果表明短期(2年)放牧处理通过增加土壤中子囊菌门的相对丰度、降低担子菌门的相对丰度从而改变土壤真菌群落结构;土壤真菌群落多样性与丰富度在各放牧强度间差异不显著,但放牧均有增加土壤真菌群落多样性与丰富度的趋势。通过对真菌群落结构变化进行方差分解,发现放牧强度通过改变土壤养分进而影响真菌群落结构;通过对真菌的共现网络进行模块化分析发现,短期的牦牛放牧对真菌相互作用主要模块的相对丰度影响不显著,而放牧强度通过影响土壤中的养分含量来影响模块相对丰度。

Yak grazing is one of the major human disturbances,and decisions about grazing management and intensity play important roles in maintaining grassland health on the Qinghai-Tibetan Plateau.In order to clarify the effect of short-term yak grazing on soil fungal communities in alpine meadows,an experiment involving a range of grazing intensities was conducted in a typical alpine meadow of northwestern Sichuan.The experiment included a control group(no grazing),light grazing(1 yak·ha^(−1)),moderate grazing(2 yak·ha^(−1)),and heavy grazing(3 yak·ha^(−1)).After two years,it was found that the grazing treatments had changed the community structure of the soil fungi by increasing the relative abundance of Ascomycota and decreasing the relative abundance of Basidiomycota in the topsoil.Grazing treatments tended to enhance the diversity and richness of soil fungal communities,although differences among grazing intensities were not statistically significant.Variance partitioning analysis indicated that grazing intensity affected the community structure of soil fungi via alteration of soil nutrient status.Furthermore,the co-occurrence network showed that short-term yak grazing had no significant effect on the relative abundance of the main fungal groups,while grazing intensity affected the relative abundance of fungal groups through change in soil nutrient status.