Environmental effects on community productivity of aquatic macrophytes are mediated by species and functional composition

Abstract

AbstractEnvironmental variations are rapidly altering plant species and functional composition, which may have consequent influences on ecosystem functioning. We measured species and functional diversity of macrophyte community as well as environmental variables in 1,008 plots in 24 freshwater lakes across Yunnan–Guizhou plateau and Yangtze River in south China. We used generalized multilevel path models to test how the environmental effects on macrophytes productivity directly and indirectly through changes in species and functional diversity. We found distinct species and functional responses to the four groups of environmental variables:water quality, heterogeneity, climate, and topography. Macrophyte communities tended to be high richness and dominated by species with high‐stem dry mass content and long flowering duration at eutrophic, heterogeneous, high altitude, or deepwater habitats. Submersed and annual species with high‐specific leaf area dominated in heterogeneous and high altitude conditions, whereas species with high shoot and leaf dry mass content as well as thin stem and lamina dominated in heterogeneous and low‐altitude conditions. Functional dispersion (FDis) decreased in heterogeneous and high‐altitude habitats and increased at deepwater. These changes in functional composition have subsequently significant influences on community productivity, involving the opposite pathways of positive effects of community‐weighted mean (CWM) traits and negative effects of FDis, ultimately contributing to the observed invariable macrophytes productivity along the tested environmental gradients. Our results provide strong evidences that both species and functional composition mediate the cascading effects of environments on macrophytes productivity.