基于分子生态学网络探究西藏草地放牧对土壤微生物群落的影响

Molecular ecological network analyses revealing the effects of livestock grazing on soil microbial community in the Tibetan grassland

摘要:

【目的】揭示西藏地区放牧对在功能基因层面上的微生物相互作用的影响。【方法】利用最近发明的网络工具(基于随机矩阵理论的分子生态学网络)分别在对照和放牧条件下分析基因芯片中碳循环和氮循环基因。【结果】碳和氮循环基因网络在对照和放牧条件下都具有无标度、小世界、模块性和层次性的拓扑学特征。放牧条件下的网络关键基因(模块枢纽和连通者)与对照显著不同。放牧导致网络变得小而紧密，暗示环境压力的存在。地上植物生物量与微生物基因网络显著相关(P=0.001)，证实了研究样地地上植物与地下微生物紧密相连。【结论】放牧显著改变了西藏草地在功能基因层面上的微生物相互作用关系。

关键词:分子生态学网络，土壤微生物相互作用，功能基因，西藏放牧，碳氮循环，基因芯片

Abstract:

[Objective] To unveil effects of livestock grazing in Tibet on microbial interaction at the functional gene level. [Methods] We applied a recently developed network inference tool (Random Matrix Theory-based molecular ecological network) on GeoChip data related to carbon (C) and nitrogen (N) cycling with or without livestock grazing. [Results] C and N cycling gene networks in both control and grazing conditions had topological features of scale-free, small-world, modularity and hierarchy. Key genes in the grazing networks (hubs and connectors) differed substantially from those in the control. The grazing effects on soil microbial interactions were revealed by smaller, denser networks in the grazing samples, suggestive of environmental stress. In support of close linkages between aboveground plants and microbial community at this site, aboveground plant biomass was significantly (P=0.001) linked to grazing network topology. [Conclusion] Livestock grazing significantly altered microbial interaction at the functional gene level.

Key words:Molecular ecological network, Soil microbial interactions, Functional genes, Grazing in Tibet, C and N cycling, GeoChip