亚热带森林树种多样性与生产力关系的内在机制研究

Although biodiversity usually have a significant effect on ecosystem functioning, no unanimous conclusion can be drawn about the potential mechanism. Biodiversity effect is partitioned by selection effect and complementarity effect, but the source of complementarity effect (caused by resource partitioning and species competition)is difficult to partition in practice. A new individual level trait-based study provide a species competition model about the effect of resource partitioning and species competition on plant growth, which is a nice opportunity to partition the source of complementarity effect. .In this project, based on individual level functional traits (root, branch and leaf), plant growth volume (basal diameter and height), identity and diversity of neighbors as well as environmental factors (topography factor, temperature, humidity, light factor, nutrients of rhizosphere soil) of 820 individuals across different species richness levels (1,2,4, 8, 16) were measured in subtropical forest biodiversity-ecosystem functioning controlled experiment in China (BEF-China), which is constantly monitored from 2009. .The effects of biodiversity effect and environmental factors on community level functional traits and productivity were explored. Community level species competition index was gained by modifying the species competition model. The relationships between environmental factors, community level species competition index and biodiversity effects were analyzed by structural equation model (SEM). The effects of abiotic and biotic factors on biodiversity effects were examined and the contributions of resource partitioning and species competition on complementarity effect were explained, when the effect of environmental factors was removed. Therefore, the internal mechanism on the relationship between tree diversity and productivity was revealed, which is helpful to expand the theory of biodiversity and ecosystem functioning (BEF) and provide a scientific basis for biodiversity conservation and productivity improvement of subtropical forest.

生物多样性能够显著地影响生态系统功能，但其潜在机制众说纷纭。生物多样性效应可划分为选择效应和补偿效应，但补偿效应的来源依然难以区分。最新基于个体水平的功能性状研究提出了物种竞争与资源互补作用于植物生长的竞争模型，为区分补偿效应的来源提供了有利的契机。本项目以连续监测的BEF-China控制实验为对象，基于个体水平监测在1、2、4、8、16个物种等多样性水平下820株植物的根、枝、叶功能性状，基径、树高生长量及环境因子，探讨物种多样性和环境因素如何影响植物功能性状及生产力；通过改进竞争模型获得群落竞争指数，应用结构方程模型分析环境因子-群落竞争指数-生物多样性效应的关系，阐明生物因素和非生物因素对生物多样性效应的影响机制，诠释刨除环境因素后，物种竞争和资源互补在补偿效应中的相对贡献，以期揭示树种多样性与生产力关系的内在机制，丰富BEF理论，为亚热带森林生物多样性保育及生产力提升提供科学依据。

生物多样性能够显著地影响生态系统功能，但其潜在机制众说纷纭。基于个体水平的功能性状研究为区分补偿效应的来源提供了有利的契机。以中国亚热带森林生物多样性与生态系统功能实验样地（BEF-China）为研究对象，从个体水平和物种水平功能性状的角度，通过对不同多样性水平下根叶功能性状（包括形态学性状及养分含量）、地上和地下生产力(包括树高生长速率、地径生长速率、枯枝产量、细根产量及其周转等)及环境因子（包括土壤和光照等）测定，探讨物种多样性及环境因素如何影响群落水平的功能性状进而影响森林生产力，结果表明：1）树种类型（包括叶习性、耐荫性、根系分布、菌根类型等）和树种多样性对根叶功能性状都有显著影响，树种类型与树种多样性的交互作用也对根叶功能性状有显著影响，并且所有类型的树种都随着树种多样性的增加，其根叶功能性状协同性也随之增加。根系功能性状对土壤的适应性强于叶片功能性状，并且根叶功能性状协同性随着土层的加深而逐渐增强。2）深根-深根组合细根产量和周转的净效应通常为正效应，主要表现为垂直生态位上的资源竞争，而深根-浅根组合的细根产量和周转的净效应通常为负效应；意味着深根-浅根组合在垂直生态位上的资源互补效应有利于植物投资更少的资源用于根系构建，并且有利于延长细根的寿命；落叶-落叶树种组合枯枝生物量的净效应为正效应，也体现了生态位重叠而产生的竞争造成了更多的枝条枯死，而落叶-常绿树种组合则为负效应，意味着落叶-常绿树种在光资源上季节性地资源互补有利于减少枯枝的产生，延长枝条的寿命。3) 树种多样性对地上生产力的影响受到根叶功能性状的共同调控，而树种多样性对地下生产力及其周转的影响次序为根系功能性状>叶片功能性状>土壤。总之，混种后各个树种的根叶功能性状协同性增加，而基于功能性状的研究方法可以解析混种后各个树种之间的竞争和资源互补效应，为揭示树种多样性与生产力关系的内在机制提供了新的视角。

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