Journal of Plant Ecology ›› 2021, Vol. 14 ›› Issue (3): 491-503.DOI: 10.1093/jpe/rtab009

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  • 收稿日期:2020-10-20 修回日期:2020-12-02 接受日期:2021-01-11 出版日期:2021-06-01 发布日期:2021-03-29

Species abundance is jointly determined by functional traits and negative density dependence in a subtropical forest in southern China

Weitao Wang1, Yun Jiang1, Buhang Li1, Nianxun Xi1, Yongfa Chen1, Dong He2, Jiayi Feng1 and Chengjin Chu1,*   

  1. 1 Department of Ecology, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China, 2 School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200241, China

    *Corresponding author. E-mail: chuchjin@mail.sysu.edu.cn
  • Received:2020-10-20 Revised:2020-12-02 Accepted:2021-01-11 Online:2021-06-01 Published:2021-03-29

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摘要： 植物物种多度受功能性状和负密度依赖共同影响——以中国南亚热带黑石顶森林样地为例
影响植物群落中植物物种多度的因素较多，确定关键影响因素及阐明其具体机制一直是群落生态学的研究重点之一。目前确定性的影响因素主要有两大类：植物功能性状和负密度依赖。功能性状通过影响植物的竞争能力、资源的获取效率、对环境的适应能力等方面进而影响植物的多度；负密度依赖表现在同种或异种植物个体在空间上聚集，特异性的寄主(病原菌、昆虫等)传播容易导致植物个体(主要为幼苗和小树)死亡，种群发生自疏，进而影响植物的多度。到目前为止，单一探究植物功能性状或负密度依赖对植物多度影响机制的研究已有大量报道，而将两者结合来探讨对植物多度的影响的工作相对较少。为了更深入地探索影响植物多度的机制，本研究中我们综合分析了功能性状与负密度依赖对植物多度的影响。研究地点为广东省黑石顶亚热带森林50 ha大样地；功能性状方面选取了叶面积(LA)、比叶面 积(SLA)、叶片干物质含量(LDMC)、叶片氮含量(LNC)和最大电子传输速率(ETRmax)；植物物种所受负密度依赖强度通过构建小树在样地两次普查期间的存活状况受邻体密度影响的层次贝叶斯模型计算；通过结构方程模型构建功能性状-负密度依赖-物种多度的内在联系框架。结构方程模型结果显示，物种多度受功能性状和负密度依赖共同作用，其中功能性状对物种多度的影响包括直接作用和通过负密度依赖的间接作用。具体来说，SLA对多度的影响包括直接和间接两种；LDMC和LNC仅间接影响物种多度；LA和ETRmax对多度只有直接影响；负密度依赖与物种多度之间存在直接的负相关关系，说明多度较高的物种受到的负密度依赖效应更强。结构方程模型对物种多度差异的解释度达到20%。以上结果表明，黑石顶植物多度分布是功能性状与负密度依赖共同作用的结果；比叶面积在所研究的因素中贡献最大。该项工作有助于提高我们对亚热带森林植物常见种和稀有种分布格局的理解。

关键词: 植物多度, 负密度依赖, 功能性状, 常见种, 稀有种

Abstract:

Aims

The factors affecting species abundance are a subject of ongoing debates in community ecology. Empirical studies have demonstrated that tree abundance is affected by plant functional traits and negative density dependence (NDD). However, few studies have focused on the combined effects of NDD and plant functional traits on species abundance.

Methods

In this study, we used tree functional traits and two census data from a 50-ha forest dynamic plot in the Heishiding (HSD) Nature Reserve to explore the combined effects of functional traits and NDD on species abundance. Using hierarchical Bayesian models, we analyzed how neighbor densities affected the survival of saplings from 130 species and extracted posterior means of the coefficients to represent NDD. The structural equation modeling (SEM) analysis was then applied to investigate the causal relationships among species functional traits, NDD and species abundance.

Important Findings

SEM showed that tree functional traits, including specific leaf area (SLA), leaf area (LA), leaf dry matter content (LDMC), leaf N content (LNC), maximum electron transport rate (ETRmax) and conspecific adult negative density dependence (CNDDadult), together explained 20% of the total variation in tree abundance. Specifically, SLA affected tree abundance both directly and indirectly via CNDDadult, with a totally negative influence on abundance. LDMC and LNC had only indirect effects mediated by CNDDadult on tree abundance. ETRmax and LA had directly negative effects on abundance, but their direct connections with CNDDadult were not observed. In addition, CNDDadult was negatively correlated with species abundance, indicating that abundant species are under stronger NDD. Among these investigated traits, SLA contributed the most to the variation in CNDDadult and abundance. We argued that our findings of trait–CNDDadult–abundance relationships can improve our understanding of the determinants of species commonness and rarity in forests.

Key words: tree abundance, negative density dependence, functional traits, common species, rare species

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