Most plant diversity-function studies have been conducted in terrestrial ecosystems and have focused on plant productivity and nutrient uptake/retention, with a notable lack of attention paid to belowground processes (e.g., root dynamics, decomposition, trace gas fluxes). Here we present results from a mesocosm experiment in which we assessed how the richness of emergent macrophyte functional groups influences aboveground and belowground plant growth and microbial-mediated functions related to carbon and nitrogen cycling, with an emphasis on methane (CH4) efflux and potential denitrification rates. We found that an increase in the richness of wetland plant functional groups enhanced belowground plant biomass, altered rooting patterns, and decreased methane efflux, while having no effect on aboveground plant production or denitrification potential. We hypothesize that the greater root production and increased rooting depth in the highest diversity treatments enhanced CH4 oxidation to a relatively greater degree than methane production, leading to an overall decrease in CH4 efflux across our plant functional group richness gradient.
