植物群落稀有种维持机制与土壤反馈的研究进展

自Janzen-Connell (J-C)假说提出后半个世纪以来, 生态学家在热带及亚热带森林对该假说开展的大量实证研究表明, 由专性天敌导致的J-C效应所引起的负密度制约是维持森林多样性和决定群落组成的重要驱动力, 该假说成功地解释了热带及亚热带森林的丰富多样性。土壤病原真菌所引起的植物-土壤负反馈是J-C效应最主要的表现形式。然而, 对于植物-土壤负反馈是否能够维持森林群落中的大量稀有种仍然存在许多争议。基于当代物种共存理论的“稀有种优势”假说认为, 只有在满足“可入侵准则” (即物种在稀有时具有种群增加的趋势)的前提下, 稀有种才能在群落中与其他物种长期共存。然而, 当前基于土壤反馈的实验结果与该理论预测相悖, 因此在稀有种的维持机制方面仍存在较大的分歧。本文通过介绍植物-土壤反馈理论, 整合了可能对稀有种维持有较大影响的因素, 包括共生菌根真菌、土壤养分以及植物细根性状等在影响土壤负反馈方面的相关研究, 并对这些因素如何影响群落中物种多度和稀有种在群落中的维持进行了探讨。最后, 我们也从其他角度探讨了一些对稀有种维持的研究。我们认为在未来对稀有种的研究中, 探讨使其长期存续的“优势”和制约其种群扩大的“限制”同等重要, 将当代物种共存理论与新技术、新方法相结合对于探究稀有种的维持机制具有重要的意义, 可为稀有种保护提供理论依据。

Advances in mechanisms of rare species maintenance and plant-soil feedback in plant communities

Background & Aim: Since the Janzen-Connell (J-C) hypothesis was proposed half a century ago, a mounting number of studies have been conducted to test the hypothesis in tropical and subtropical forests. These studies have since greatly improved our understanding of how high biodiversity is maintained. In particular, the pathogenic fungi-induced J-C effect, a type of negative plant-soil feedback (PSF), has been well-recognized as a mechanism to maintain biodiversity and structure community composition, though the overall contribution of PSF to the persistence of a large number of rare species in nature remains controversial. As predicted by the modern species coexistence theory, the “invasion criterion” should be met for rare species to co-exist with other species such that one species will increase in abundance when rare. However, previous studies show results contrary to the prediction of such theory and have thus sparked debates on the mechanism underlying rare species maintenance.
Progresses: In this work, we review PSF and the potential factors associated with PSF, including mycorrhizal fungi, soil nutrient content, and fine root functional traits. We discuss their contributions in maintaining rare species and determining species abundance via PSF. In addition to PSF, some other perspectives about rare species maintenance are also covered in this review.
Prospects: We propose that the advantages in maintaining the long persistence of rare species and the limitations in restricting population expansion of rare species may be of equal importance for rare species. The combination of modern species coexistence theory and new techniques and methodologies provide promising future directions to fully understand rare species and to better conserve rare species in the future.