藏东南森林土壤微生物群落结构与土壤酶活性随海拔梯度的变化

Microbial community and soil enzyme activities along an altitudinal gradient in Sejila mountains

摘要:

【目的】针对青藏高原藏东南地区色季拉山不同海拔森林土壤，探讨微生物群落与土壤酶活性之间的联系以及受控因子。【方法】利用微生物细胞膜磷脂(PLFA)方法研究土壤微生物群落结构随海拔变化情况，分析土壤葡萄糖苷酶、酚氧化酶、蛋白酶、L-天冬酰胺酶、脲酶和酸性磷酸酶活性以及土壤理化性质随海拔的变化趋势。【结果】土壤理化性质和生化指标随海拔增高没有显著变化，如水分含量、有机碳、全氮、碳氮比、pH、无机氮和硝态氮，土壤葡萄糖苷酶、酚氧化酶、蛋白酶、L-天冬酰胺酶和酸性磷酸酶活性等；然而，微生物丰度呈现中峰优势分布规律，细菌、真菌、革兰氏阳性菌、革兰氏阴性菌和放线菌含量在海拔3 900 m和4 000 m处生物量显著高于低海拔和更高海拔。皮尔森相关性分析表明土壤pH是影响微生物群落结构的主要因子，但海拔梯度上的温度变化与微生物群落结构和酶活性不存在显著相关性；同时，有机碳、全氮、水溶性有机碳和水溶性有机氮和pH等理化指标与土壤酶活性显著相关。【结论】在藏东南色季拉山森林生态系统，海拔梯度对土壤微生物群落结构影响较大，土壤理化指标与生物特征对海拔梯度的响应较弱。

Abstract:

[Objective] This study tried to find the key factor which affected the soil microbial communities and enzyme activities along an altitudinal gradient in forest ecosystem in Sejila mountains. [Methods] This study tested six soil enzyme activities (β-glucosidase, phenol oxidase, protease, L-asparaginase, urease and acid phosphatase) and soil microbial communities structures (bacteria, fungi, gram-positive bacteria, gram-negative bacteria and actinomycete). [Results] Soil physicochemical properties such as moisture, TOC, TN, C/N and pH had no significant changes along the altitudinal gradient. Moreover, soil enzyme activities such as β-glucosidase, phenol oxidase, protease, L-asparaginase and acid phosphatase had no significant change along the altitudinal gradient. However, bacteria, fungi, gram-positive bacteria, gram-negative bacteria and actinomycete biomass all showed a mid-domain effect along the altitudinal gradient, which reached higher values at 3 900 and 4 000 ms.a.l. Person correlation analysis showed that pH was the key factor structuring microbial communities, yet mean annual temperature had no significant correlation with microbial communities and enzyme activities. Instead, soil physicochemical properties such as TOC, TN, WSOC and WSON were key factors in enzyme activities. [Conclusion] These results suggested that elevational gradients had an important influence on soil microbial communities, but not on soil physicochemical factors and soil enzyme activities.