Data from: Shifts and linkages of functional diversity between above- and below-ground compartments along a flooding gradient

Trait-based approaches have the potential to reveal general and predictive relationships between organisms and ecosystem functioning. However, the mechanisms underlying the functional structure of communities are still unclear. Within terrestrial ecosystems, several studies have shown that many ecological processes are controlled by the interacting above- and below-ground compartments. However, few studies have used traits to reveal the functional relationships between plants and soil fauna. Mostly, research combining plants and soil fauna solely used the traits of one assemblage in predictive studies.
Above-ground (plants) and below-ground (Collembola) compartments were sampled over a flooding gradient in northern France along the Seine River. First, we measured the effect of flooding on functional and taxonomic assembly within both communities. We then considered the linkages between plant and Collembolan species richness, community traits and assessed whether traits of both compartments converged at high flooding intensity (abiotic filtering) and diverged when this constraint is released (biotic filtering).
Species richness of both taxa followed the same bell-shaped pattern along the gradient, while a similar significant pattern of functional richness was only observed for plants. Further analyses revealed a progressive shift from trait convergence to divergence for plants, but not for Collembola, as constraints intensity decreased. Instead, our results highlighted that Collembola traits were mainly linked to the variations in plant traits. This leads, within Collembola assemblages, to convergence of a subset of perception and habitat-related traits for which the relationship with plant traits was assessed.
Synthesis. Using a trait-based approach, our study highlighted that functional relationships occur between above- and below-ground compartments. We underlined that functional composition of plant communities plays a key role in structuring Collembola assemblages in addition to the role of abiotic variables. Our study clearly shows that functional diversity provides a new approach to link the above- and below-ground compartments and might, therefore, be further considered when studying ecological processes at the interface between both compartments.

基于性状的研究方法（Trait-based approaches）有望揭示生物与生态系统功能之间具有普适性且可预测的关联。然而，群落功能结构背后的调控机制仍未明确。在陆地生态系统中，多项研究已证实，多数生态过程受地上与地下两个交互作用的组分共同调控。但目前鲜有研究借助性状来阐明植物与土壤动物之间的功能关联。绝大多数结合植物与土壤动物的预测性研究，仅采用了其中一个类群的性状数据。

本研究沿着法国北部塞纳河沿岸的水淹梯度，对地上（植物）与地下（弹尾目（Collembola））两个组分开展了采样。首先，我们量化了水淹对两个群落的功能组装与分类组装的影响；随后，我们探究了植物与弹尾目物种丰富度、群落性状之间的关联，并评估了两个组分的性状是否在高水淹强度下发生趋同（即非生物过滤（abiotic filtering）），而在该限制因子解除后发生趋异（即生物过滤（biotic filtering））。

两个类群的物种丰富度沿水淹梯度均呈现出一致的钟形分布模式，但仅在植物群落中观测到了具有统计学显著性的功能丰富度相似变化模式。进一步分析显示，随着环境限制强度降低，植物的性状呈现出从趋同到趋异的渐进式转变，而弹尾目则未出现该趋势。相反，本研究结果表明，弹尾目的性状主要与植物性状的变异相关联。这使得弹尾目类群中，与感知及生境相关的部分性状发生趋同，本研究亦针对此类性状与植物性状的关联展开了评估。

研究总结：本研究借助基于性状的研究方法，证实了地上与地下组分之间存在功能关联。我们明确指出，除非生物变量的作用外，植物群落的功能组成在弹尾目类群的结构构建中发挥着关键作用。本研究清晰表明，功能多样性为联结地上与地下组分提供了全新的研究路径，因此在探究两类组分界面处的生态过程时，可进一步借鉴该思路。