Revegetation and production in a constructed freshwater tidal marsh

The development of a constructed freshwater tidal wetland was studied for the first two growing seasons. Vegetation was sampled in the constructed marsh and in a neighboring natural Carex-Peltandra marsh using a random sampling design to determine species occurrence, vegetation-elevation relations, and planted species survival. Planted with Scirpus pungens and Leersia oryzoides in the high marsh and Peltandra virginica in the low marsh, the constructed marsh was rapidly colonized by an additional 54 plant species. The patterns of vegetation and the direction of development in the constructed marsh were determined by the level of mortality of planted species, the rate of colonization by individual planted and invading species, and by elevation. Eight productivity methods (harvest and phenometric) were used to estimate the accumulation of aboveground biomass by the planted species and two dominant invading species Typha angustifolia and T. latifolia. The aboveground estimates for S. pungens, ranging from a low of 348.48 g{dollar}cdot{dollar}m{dollar}sp{lcub}-2{rcub}cdot{dollar}yr{dollar}sp{lcub}-1{rcub}{dollar} (Peak Live) to a high of 1403.78 g{dollar}cdot{dollar}m{dollar}sp{lcub}-2{rcub}cdot{dollar}yr{dollar}sp{lcub}-1{rcub}{dollar} (Hopkinson et al. method) demonstrate the extreme results for different computational methods. Total production for the constructed marsh was determined by taking the most accurate estimate for each species and adjusting for measures of density and coverage. By the end of the second growing season, S. pungens achieved aboveground production values within the reported range of natural Scirpus marshes. P. virginica grew, but not as rapidly. The low marsh areas gradually developed into Typha-Cyperus community. Total estimated belowground biomass of the low marsh was relatively low, but the aboveground production value was within the range for natural Typha marshes. Overall, aboveground production of the constructed high and low marshes were 100% and 27% respectively, compared to the adjacent natural marsh.