Plant functional diversity and the restoration of riparian wetland ecosystem function

Ecosystem restoration is a promising method to mitigate the loss and degradation of ecosystem functions.  This research examines the effects of plant functional trait diversity (FD) on the restoration of two key riparian ecosystem functions: denitrification and plant biomass nitrogen (N).  At the Duke Stream Wetland Assessment and Management Park (SWAMP) in Durham, N.C., we planted plots with 1, 4 or 8 species in May 2005.  We collected soil samples during 2005-2006 and analyzed them for Denitrification Enzyme Assay (DEA) analysis, extractable N, % organic matter, % moisture, and microbial biomass.  We collected aboveground plant biomass in early fall each year.  Results indicate that, along with other environmental variables, plant FD may be a good predictor of some ecosystem functions such as biomass N.  However, for other functions such as denitrification, average plant trait values, including belowground biomass and specific root length, are better predictors.  These results suggest that plant trait diversity can be an important factor in restoring certain, but not all, ecosystem functions.  As a result, when the goal of restoration is to restore a suite of ecosystem functions, plant functional diversity should be considered in the restoration design.