橡胶林恢复过程中土壤固氮微生物的多样性格局与构建机制

Diversity patterns and assembly mechanisms of soil diazotrophic community following the restoration of rubber monocultures

摘要

【目的】热带地区单一橡胶种植园的快速扩张导致严重土壤退化与生态系统氮限制。生物固氮作用是缓解退化系统养分限制的关键，但其功能微生物群落在橡胶林生态恢复过程中的动态与构建机制尚不明确。本研究旨在揭示橡胶林恢复过程中土壤固氮微生物群落的多样性格局及其构建机制，并比较不同恢复策略（自然恢复与人工促进恢复）的差异。【方法】采用“空间替代时间”的方法，以云南西双版纳地区单一橡胶林（RM）、自然恢复林（NF）、人工恢复林（AF）以及成熟热带雨林（MF）为研究对象，其中 RM 代表退化森林，NF 和 AF 分别代表不同恢复策略下的恢复林，MF 代表参照森林。基于 nifH 基因高通量测序数据，依据丰度阈值划分不同生态类群，并结合 β 多样性分解与群落构建模型，系统解析橡胶林恢复过程中土壤固氮微生物群落多样性格局与构建机制的变化特征。【结果】（1）恢复林（NF 和 AF）的固氮微生物群落结构与 RM 和 MF 均存在显著差异，且 NF 与 AF 之间呈现明显分异；（2）β 多样性分解揭示，物种周转是驱动固氮微生物群落差异的主导过程，且条件稀有类群（CRT，丰度 < 1% 且部分样品 < 0.01%）和绝对稀有类群（ART，所有样品丰度 < 0.01%）与总类群呈现高度一致的周转格局，表明这些类群可能是总类群高周转格局的重要贡献者；（3）固氮微生物群落构建整体以随机性过程（生态漂变和扩散限制）为主导，并在不同恢复策略与生态类群间存在差异：总类群、CRT 与 ART 在 AF 中随机性过程占比增加，在 NF 中则有所降低；而优势类群在 AF 和 NF 中均有所降低。pH 值、土壤总碳和土壤总氮是驱动不同生态类群分化的关键环境因子，且 CRT 较其他类群具有更强的环境敏感性，展现出潜在的环境指示作用。【结论】橡胶林恢复过程中，固氮微生物群落结构发生显著重组且构建机制呈现差异化响应。研究启示，在恢复实践中应关注不同恢复策略对群落构建过程的长期影响，并建议实施“初期人工促进-后期自然主导”的协同恢复策略，以提升生态系统的长期稳定性与韧性。本研究系统揭示了橡胶林恢复过程中固氮微生物群落构建的差异化响应特征，为退化生态系统的功能导向性恢复提供了科学依据。

Abstract

[Objective] The rapid expansion of monoculture rubber plantations in tropical regions has led to severe soil degradation and ecosystem nitrogen limitation. Biological nitrogen fixation plays a crucial role in alleviating nutrient constraints in degraded systems; however, the dynamics and assembly mechanisms of its key functional microbial communities during rubber plantation restoration remain poorly understood. This study aimed to reveal the diversity patterns and assembly mechanisms of soil diazotrophic communities during restoration and to compare the differences between natural restoration and human-assisted restoration strategies. [Method] Using a space-for-time substitution approach, four forest types were investigated in Xishuangbanna, China: rubber monoculture (RM), naturally restored forest (NF), artificially restored forest (AF), and mature tropical rainforest (MF). Here, RM represents a degraded forest, while NF and AF represent regenerated forests under different restoration strategies, and MF serves as a reference. Based on high-throughput sequencing of the nifH gene, we classified different ecological groups according to abundance thresholds, and combined β diversity decomposition with community assembly models to systematically analyze the shifts in diversity patterns and assembly mechanisms of soil diazotrophic communities during rubber plantation restoration. [Result] (1) The community structures of diazotrophs in restored forests (NF and AF) were significantly different from both RM and MF, with a clear divergence observed between NF and AF; (2) β diversity decomposition revealed that species turnover was the dominant process driving compositional variation among diazotrophic communities, and conditionally rare taxa (CRT, abundance < 1% with partial samples < 0.01%) and absolutely rare taxa (ART, abundance < 0.01% in all samples) were highly consistent with the turnover pattern of the overall community, suggesting that these taxa might be important contributors to the high turnover of the overall community; (3) The assembly of diazotrophic communities is predominantly governed by stochastic processes (ecological drift and dispersal limitation), with variations observed across different restoration strategies and ecological groups. Specifically, the contribution of stochastic processes increased in AF but decreased in NF for overall taxa, CRT, and ART, while it decreased for dominant taxa in both AF and NF. pH, total soil carbon (TC), and total soil nitrogen (TN) were identified as key environmental factors driving the differentiation of different ecological groups, with CRT exhibiting stronger environmental sensitivity than other groups, indicating their potential as environmental indicators. [Conclusion] Restoration of rubber monocultures drives the restructuring of soil diazotrophic communities, with assembly mechanisms exhibiting differentiated responses. Our findings suggest that restoration practices should pay attention to the long-term impacts of different restoration strategies on community assembly processes, and we recommend adopting an integrated restoration strategy of “initial artificial facilitation followed by natural succession” to balance recovery efficiency with long-term ecosystem stability and resilience. This study reveals the differential response characteristics of diazotrophic community assembly during rubber plantation restoration, providing a scientific basis for function-oriented restoration of degraded ecosystems.

关键词

橡胶林恢复 / 生物固氮 / β 多样性分解 / 群落构建 / 随机过程 / 生态类群分化

Key words

rubber monoculture restoration / biological nitrogen fixation / β diversity decomposition / community assembly / stochastic processes / ecological group differentiation

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基金资助

云南省重点研发计划(202403AC100028)

中国科学院西双版纳热带植物园“十四五”科技创新规划项目(E3ZKFF7B)

国家自然科学基金项目(32171529)

云南省“兴滇英才支持计划”青年人才项目(YNWR-QNBJ-2020-066)

“智慧云南”计划(202403AM140016)

云南省“彩云博士后计划”创新支持项目()