Functional identity enhances aboveground productivity of a coastal saline meadow mediated by Tamarix chinensis in Laizhou Bay, China

Research in recent decades has confirmed that biodiversity influences ecosystem productivity; however, the potential mechanisms regulating this process remain subject to controversy, due to variation across ecosystems. Here, the effects of biodiversity on ecosystem productivity were evaluated using three variables of biodiversity (taxonomic diversity, functional identity, and functional diversity) and surrounding environmental conditions in a coastal saline meadow located on the south coast of Laizhou Bay, China. At this site, the shrub and field layers were primarily dominated by Tamarix chinensis and natural mesic grasses, respectively. Our results showed that functional identity, which is quantified as the community weighted mean of trait values, had greater explanatory ability than taxonomic and functional diversity. Thus, ecosystem productivity was determined disproportionately by the specific traits of dominant species. T. chinensis coverage was a biotic environmental factor that indirectly affected ecosystem productivity by increasing the community weighted mean of plant maximum height, which simultaneously declined with species richness. The present study advances our understanding of the mechanisms driving variation in the productivity of temperate coastal saline meadows, providing evidence supporting the "mass ratio" hypothesis.