Increasing tree phylogenetic diversity stimulates microbial functional potential in a subtropical forest

Soil microbial functions are closely related to ecosystem productivity, carbon sequestration, and their responses to global change. Tree diversity has been found to impact microbial community composition, diversity, and functions, but how it modulates the linkage between microbial community facets and functions remains unclear. Here, 45 plots covering a natural gradient of tree phylogenetic diversity (TPD) were selected in a subtropical forest of southwest China to explore how increasing TPD impacts soil microbial community facets and microbial functional potential, with the latter being assessed by the abundances of carbon, nitrogen, and phosphorus cycling-related functional genes. Our results indicate that soil fungal alpha diversity increased significantly, but bacterial alpha diversity did not change as TPD increased. Both soil microbial network complexity and stability improved significantly with increasing TPD. Ultimately, increasing TPD promoted soil microbial functional potential by stimulating soil carbon and nitrogen availability, microbial keystone diversity, and network stability collectively. These findings emphasize the critical roles of keystone taxa and network stability as microbial factors in stimulating soil microbial function in response to increasing TPD, and provide useful information for predicting ecosystem functions in Earth system models.

土壤微生物功能与生态系统生产力、碳固存过程及其对全球变化的响应密切相关。已有研究证实，树木多样性会影响微生物群落的组成、多样性与功能，但树木多样性如何调控微生物群落特征与功能之间的关联，目前仍不明确。本研究在中国西南亚热带森林中选取了45个样地，这些样地涵盖了树木系统发育多样性（Tree Phylogenetic Diversity, TPD）的自然梯度，旨在探究树木系统发育多样性提升如何影响土壤微生物群落特征与微生物功能潜力，其中功能潜力通过碳、氮、磷循环相关功能基因的丰度进行评估。研究结果显示，随着TPD提升，土壤真菌的α多样性显著升高，而细菌α多样性未发生显著变化；土壤微生物网络的复杂度与稳定性均随TPD提升而显著增强。最终，树木系统发育多样性提升可通过协同提升土壤碳、氮有效性、微生物关键类群多样性以及网络稳定性，从而促进土壤微生物功能潜力。本研究结果强调了关键类群与网络稳定性作为微生物调控因子，在响应树木系统发育多样性提升过程中对土壤微生物功能的关键驱动作用，同时可为地球系统模型中的生态系统功能预测提供有价值的参考依据。