Diverse communities are more productive than less diverse ones because of two overyielding mechanisms: a selection effect and a complementarity effect, which operate in different ways. Moreover, ecosystem multifunctionality is expected to increase and become more stable with increasing species diversity. However, it is unclear how the aforementioned processes operate in aquatic ecosystems, where the overyielding mechanisms, ecosystem multifunctionality, and stability have been poorly explored. Here, we conducted an experimental study manipulating three levels of macrophyte richness to test two hypotheses: (i) the positive macrophyte richness effect on community biomass production is the result of the species complementarity effect; (ii) ecosystem multifunctionality and its stability increase with macrophyte richness. We found that macrophyte species increased their biomass production in high richness treatment, evidencing overyielding, which occurred through a significant complementarity effect. Macrophyte richness also enhanced ecosystem multifunctionality, and made it more stable over time, but only in high richness treatment. Our study shows that preserving high macrophyte richness is essential to preserving the ability of aquatic communities and ecosystems to sustain their functioning.

由于两种过度产出机制：选择效应和互补效应，它们以不同的方式运作，因此多样化的社区比不那么多样化的社区更具生产力。此外，随着物种多样性的增加，生态系统的多功能性有望增加并变得更加稳定。然而，目前尚不清楚上述过程如何在水生生态系统中运作，其中对超产机制、生态系统多功能性和稳定性的探索很少。在这里，我们进行了一项操纵三个水平的大型植物丰富度的实验研究，以检验两个假设：(i) 大型植物丰富度对群落生物量产生的积极影响是物种互补效应的结果；(ii) 生态系统多功能性及其稳定性随着大型植物丰富度的增加而增加。我们发现大型植物物种在高丰度处理中增加了它们的生物量产量，证明了通过显着的互补效应发生的超产。大型植物丰富度也增强了生态系统的多功能性，并使其随着时间的推移更加稳定，但仅限于高丰富度处理。我们的研究表明，保持丰富的大型植物对于保持水生群落和生态系统维持其功能的能力至关重要。