放牧强度对若尔盖高寒草甸土壤有机质和微生物的影响

若尔盖高寒草甸处于生态脆弱带,人类活动会对若尔盖草甸的结构和功能产生影响。本研究以若尔盖高寒草甸为对象,以植被盖度作为放牧干扰强度的划分依据,将其分为:D₁,盖度0%~20%;D₂,20%~40%;D₃,40%~60%;D₄,60%~80%;D₅,80%~100%,分析探讨了不同放牧强度对土壤有机质、微生物群落结构及数量的影响。实验结果表明:随着放牧强度的增加,土壤有机质含量逐渐降低。同时,随着放牧强度增加,细菌、真菌、放线菌含量、革兰氏阳性菌(G⁺)及革兰氏阴性菌(G^-)整体呈现先降低后增加的趋势,土壤G⁺/G^-在D₃处最大,D₄处最小。以磷脂脂肪酸生物标记作为数量测度,引入生态学多样性指数的计算方法得到的微生物多样性指数表现为:D₅>D₄>D₁>D₂>D₃,且不同放牧强度之间差异不显著(P>0.05)。土壤微生物含量与土壤有机质含量存在显著的正相关关系。放牧强度不仅与高寒草甸植被生产力密切相关,还与土壤有机质及微生物群落紧密相关;因此,控制放牧强度是高寒草地恢复、维持其生产力和改善土壤质量的重要途径。

Effects of grazing intensity on soil organic matter and microorganisms in the Zoige alpine meadow

Human activities have significantly affected the structure and function of the Zoige alpine meadow ecosystem.In this study,we analyzed the effects of grazing intensity on soil organic matter (SOM) and the soil microbial community in the Zoige alpine meadow.Five grazing intensity treatments,which were based on vegetation coverage,were established:D1,coverage of 0％-20％;D2,coverage of 20％-40％;D3,coverage of 40％-60％;D4,coverage of 60％-80％;D5,coverage of 80％-100％.The SOM and total nitrogen content at 0-10 cm soil depth significantly differed among the five grazing intensity treatments (P＜0.05).With increasing grazing intensity,the amounts of bacteria,fungi,actinomycetes,and Gram-positive (G+) and Gramnegative bacteria (G-) decreased.The highest ratio of G+/G-was in D3,while the lowest was in D4.The microbial diversity index decreased in the following order:D5＞D4＞D1＞D2＞D3.The diversity index was calculated from the soil phospholipid fatty acid profiles,and did not differ significantly among the five grazing intensity treatments (P＞0.05).The soil microbe content was significantly positively correlated with SOM content.The grazing intensity was closely related not only to the productivity of the alpine meadow,but also to SOM and microbial communities.Therefore,it is important to restore and maintain soil productivity by controlling the grazing intensity in this region.