多功能性状维度上的环境筛选过程和竞争对植物群落构建的影响

Understanding changes in community structure and composition along environmental gradients is a central goal in plant ecology. Recently, trait-based approaches have been the most widely used tool in studying community structure and assembly at local and landscape scales. These studies often focus on two assembly mechanisms influencing diversity patterns along environmental gradients: environmental filtering and competition. However, two key challenges, revealed by contradictory conclusions among studies, may limit the utility of these approaches: i) intraspecific trait variation has been largely ignored despite the evidence that intraspecific variation is substantial both within and across communities; ii) most previous studies have focused on one trait axis alone, but environmental filtering and competition likely occur in multiple decoupled trait axes. We investigate how the importance of environmental filtering and competition in shaping community assembly vary along soil nutrient gradients, using herbaceous components of semiarid Savanna in Yuanjiang, Yunnan. The study is in a nested design with landscape, community, population and individual as factors. In the middle and end of herb growing season, six functional traits are measured for each individual, including traits related to plant soil resource use and traits related to light strategy. For each functional trait partitioning of trait variance across scales is conducted. Ratios of intraspecific to community-level trait variation and community-level to landscape-level trait variation are calculated to quantify the relative importance of competition and environmental filtering for community assembly in multiple trait axes. The study may improve our accurate understanding for mechanisms underlying community assembly and provide theoretical knowledge for practiced ecology such as vegetation restoration, land use management and biodiversity conservation.

土壤养分梯度上植物群落结构的变化规律是生态学的核心问题之一。环境筛选过程与竞争过程都影响群落结构，但近年来普遍采用的功能性状方法发现在环境梯度上两者相对重要性差异明显。可能的原因是绝大多数研究关注物种性状平均值，忽略种内性状变异。或者所分析的功能性状紧密相关，相互不独立。本研究以元江干热河谷的萨王纳生态系统的草本植物群落为研究对象，拟探讨两个独立的性状维度上环境筛选过程和竞争沿土壤养分梯度对群落构建的影响的变化。本研究采用尺度嵌套设计（景观，群落，种群，个体），测量了所有植株在生长季中期和末期的两类功能性状：土壤营养相关的性状和光利用相关的性状。对每一种性状，计算它在所有尺度上的变异。用种内变异与群落内变异之比、群落内变异与景观尺度内总变异之比分别量化环境筛选过程和竞争的相对作用。该研究有助于阐明多功能性状维度下的群落构建的机制，进而为植被恢复、土地利用管理和生物多样保护提供理论依据。

环境因子对植物性状和种间关系的影响是群落生态学的核心问题之一。然而，人们常常忽略土壤微生物在这些生态过程中发挥的关键作用。已有的研究表明土壤微生物能够影响植物的生存、生长等，其方向取决于微生物的类别（病原体或者有益微生物）。本项目探讨了环境因子对植物性状和竞争的影响，以及土壤微生物在植物与环境二者关系中的作用。根据可用的实验平台并基于最新研究进展，本项目具体包含三项研究内容：（1）土壤微生物与水分对植物性状的影响；（2）土壤微生物与光照强度对植物性状的影响；（3）光照、土壤微生物与植物竞争。主要发现为：（1）土壤微生物改变了植物性状对环境因子（即土壤水分和光照）的响应；（2）土壤微生物提升了植物应对环境波动的能力；（3）植物与光照交互作用并影响了植物间的竞争关系。该项目在个体和种间关系的水平上阐述了土壤微生物在介导植物与非生物环境关系中的作用，对理解更高水平（如群落，生态系统）上的生态过程提供了数据支持与有价值的参考。