Biodiversity-ecosystem functioning relationship under water level regulation: Wetland plant biomass is more strongly related to functional redundancy than functional diversity

Understanding biodiversity-ecosystem functioning (BEF) relationships in natural ecosystems is essential for biodiversity conservation and ecological rehabilitation. However, it is unclear whether positive BEF relationships persist under environmental disturbances in freshwater habitats. We examined the biodiversity-biomass production relationship of wetland plant assemblages using observational data: ( n ​= ​316 plots) from Yangtze River floodplain lakes with contrasting water level fluctuations. Generalized linear mixed models were constructed to statistically separate the effects of biodiversity and environments on biomass production. Using a unifying Hill diversity framework, we tested the roles of different biodiversity facets (i.e., species diversity, functional diversity, and functional redundancy) and species relative abundance (i.e., rare, common, and dominant species) in driving the biodiversity-biomass relationship. We found that positive biodiversity-biomass relationships persisted for wetland plants in floodplain lakes after removing the effects of environment. Biomass was more strongly related to functional redundancy and species diversity than functional diversity. Common and dominant species were more important than rare species. Both the diversity and biomass of plant assemblages were affected by water level regulation with the former by inundation and the latter by type of water level fluctuations. Our results suggested that positive BEF relationships could persist in periodically disturbed habitats, where both ecosystem resilience and functioning would be promoted by functional redundancy. Rehabilitation of biodiversity and ecosystem functioning in river-floodplains will benefit from water level regulation when requirements of aquatic biota are considered. • Positive biodiversity-biomass relationship of wetland plants was revealed. • Plant biomass was driven by functional redundancy rather than functional diversity. • Water level regulation affected both biodiversity and biomass of wetland plants.