Data from: Quantifying the importance of functional traits for primary production in aquatic plant communities

1. Aquatic plant meadows are important coastal habitats that sustain many ecosystem functions such as primary production and carbon sequestration. Currently, there is a knowledge gap in understanding which plant functional traits e.g. leaf size or plant height underlie primary production in aquatic plant communities. 2. To study how plant traits are related to primary production, we conducted a field survey in the Baltic Sea, Finland, which is characterized by high plant species and functional diversity. 30 sites along an exposure gradient were sampled (150 plots) and nine plant morphological and chemical traits measured. The aim was to discern how community-weighted mean traits affect community production and whether this relationship changes along an environmental gradient using structural equation modelling (SEM). 3. Plant height had a direct positive effect on production along the exposure gradient (r = 0.33) and indirect effects through two leaf chemical traits, Leaf δ15N and Leaf δ13C (r = 0.24 and 0.18 respectively) resulting in a total effect of 0.28. In plant communities experiencing varying exposure, traits such as root N concentration and leaf δ15N had positive and negative effects on production, respectively. 4. Synthesis: Our results demonstrate that the relationship between plant functional traits and community production is variable and changes over environmental gradients. Plant height generally has a positive effect on community production along an exposure gradient, while the link between other traits and production changes in plant communities experiencing varying degrees of exposure. Thus, the underlying biological mechanisms influencing production differ in plant communities, emphasizing the need to resolve variability and its drivers in real-world communities. Importantly, functionally diverse plant communities sustain ecosystem functioning differently and highlight the importance of benthic diversity for coastal ecosystem stability.1. 水生植物草甸是重要的沿海生境，维系着初级生产力、碳汇等诸多生态系统功能。目前，学界对于水生植物群落中哪些植物功能性状（plant functional traits，如叶片大小、株高）支撑着初级生产力的认知仍存在空白。 2. 为探究植物性状与初级生产力的关联机制，我们在植物物种与功能多样性均较高的芬兰波罗的海海域开展了野外调查。沿暴露梯度共布设30个采样位点（含150个样方），并测定了9项植物形态与化学性状。本研究旨在通过结构方程模型（structural equation modelling, SEM），厘清群落加权平均性状对群落生产力的影响效应，以及该关联是否会沿环境梯度发生变化。 3. 沿暴露梯度，株高对生产力具有直接正向效应（r=0.33），同时还可通过两项叶片化学性状——叶片δ15N与叶片δ13C——产生间接效应（分别为r=0.24与r=0.18），总效应达0.28。在暴露程度各异的植物群落中，根系氮浓度与叶片δ15N等性状分别对生产力产生正向与负向调控作用。 4. 研究总结：本研究结果表明，植物功能性状与群落生产力之间的关联并非固定不变，而是会随环境梯度发生动态变化。整体而言，沿暴露梯度，株高对群落生产力均具有正向效应，而其他性状与生产力之间的关联则会因植物群落所处的暴露程度不同而发生改变。由此可见，影响生产力的潜在生物学机制在不同植物群落中存在差异，这凸显了阐明现实群落中变异及其驱动因素的必要性。值得注意的是，功能多样的植物群落对生态系统功能的维系方式各不相同，同时也凸显了底栖生物多样性对沿海生态系统稳定性的重要意义。