Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China.
Sci Total Environ. 2022 Oct 20;844:157116. doi: 10.1016/j.scitotenv.2022.157116. Epub 2022 Jul 1.
Understanding community assembly is a key issue in recognizing community succession and guiding the restoration of degraded ecosystems. Based on the stress-dominance hypothesis (SDH), along a gradient of increasing environmental stress, the relative importance of environmental filtering is supposed to be dominant but species interaction could be a minor process in assembling communities. However, this hypothesized model of the assembly-rule shift was equivocally supported by various studies. In this study, by examining riparian plant communities with the zonation distribution of species composition along a markedly contrast flooding-stress gradient, a general aim was to clarify whether assembly rules of the communities would be also sorted into the zonation pattern as expected by the SDH. Another aim was to identify how edaphic factors associate with the assembly processes. Firstly, we found that even under the distinct stress gradient, community assembly was not stratified into different rules as the SDH expected, but environmental filtering appeared as a dominant assembly process across the stress gradient. Secondly, although filtering holds as a dominant assembly rule, environmental filters were found different along the gradient. By disentangling the filters of edaphic attributes, we found that the filters significantly shifted from soil physical properties to chemical nutrients governing the filtering process along the gradient. This result revealed that, across the contrast gradient, the environmental deterministic process on assembly is so strong that the other assembly processes became weaker. By synthesizing our results, the SDH may not be applied even under the context of a contrast stress gradient, which suggests that environmental context may be a key in testing and applying the SDH. Finally, in guiding riparian restoration under strong stress, we suggest that soil physical structure rather than chemical nutrients shall be given a priority for consideration in rebuilding the degraded riparian communities.
理解群落组装是认识群落演替和指导退化生态系统恢复的关键问题。基于胁迫主导假说（SDH），在环境胁迫逐渐增加的梯度上，环境过滤的相对重要性应该是主导的，但种间相互作用可能是群落组装的一个次要过程。然而，这种关于组装规则转变的假设模型在各种研究中得到的支持并不一致。在这项研究中，通过检查沿明显对比的水淹胁迫梯度具有物种组成分带分布的河岸植物群落，我们的主要目标是阐明群落的组装规则是否也会按照 SDH 的预期模式进行分带。另一个目标是确定土壤因子如何与组装过程相关联。首先，我们发现，即使在明显的胁迫梯度下，群落组装也没有按照 SDH 的预期分层为不同的规则，而是环境过滤在整个胁迫梯度上表现为主要的组装过程。其次，尽管过滤是一种主要的组装规则，但在梯度上发现环境过滤器是不同的。通过分离土壤属性的过滤器，我们发现过滤器从土壤物理性质显著转变为化学养分，沿着梯度控制过滤过程。这一结果表明，在对比梯度上，环境决定论对组装的影响如此之大，以至于其他组装过程变得较弱。综合我们的结果，SDH 甚至在对比胁迫梯度的情况下可能都不适用，这表明环境背景可能是检验和应用 SDH 的关键。最后，在强胁迫下指导河岸恢复时，我们建议在重建退化的河岸群落时，应优先考虑土壤物理结构而不是化学养分。
