Throughout Ohio there are a number of wetlands created/restored to fulfill requirements under Section 404 of the Clean Water Act. The purpose of these created/restored wetlands is to replace habitat area and ecosystem processes of natural wetlands. The created/restored wetlands are usually monitored for vegetation structure, but rarely ecosystem function. The purpose of this study was to examine vegetation development in created/restored wetlands from a structural and functional standpoint.
Structural and functional characteristics of the dominant vegetation of mitigation bank wetlands (<20 years of age) were examined from 2008-2010 for five wetland mitigation bank sites and compared to a natural and created reference wetland sites. Wetlands were sampled for vegetation structure (species richness, Ohio floristic quality assessment index, Shannon-Wiener diversity index, and community diversity index) and function (aboveground net primary productivity and functional group composition). The mitigation wetlands were significantly different from the reference wetlands in terms of both structure and function (p<0.001), but the younger wetland mitigation sites were more similar structurally (species richness and floristic quality) to the reference sites than the older mitigation sites.
Development of vegetative structure and function was examined 15 to 17 years after wetland creation in a planted wetland and an unplanted wetland at the Olentangy River Wetland Research Park (ORWRP) on a monthly basis throughout the growing season from 2008 through 2010. Structural and functional characteristics (aboveground net primary productivity, belowground net primary productivity, macrophyte nutrient concentration) were examined. The planted wetland had higher species richness (p=0.019), floristic quality assessment scores (p=0.002), and less area occupied by invasives (p<0.001) than the unplanted wetlands, while the unplanted wetland had higher aboveground net primary productivity than the planted wetland (p=0.006). Planting may be beneficial even in a flow-through wetland that receives propagules from an adjacent river by reducing potential niches for invasive species, increasing species richness and increasing floristic quality.
Open system flow-through chambers were used to measure gaseous carbon fluxes of gross primary productivity (GPP), respiration (R), and methane emissions associated with dominant macrophyte communities at the ORWRP over the growing season. Gas samples from the inflow and outflow pipes of the chambers were collected over 48-hr periods every month from April through September on odd hours between sunrise and sunset and twice nightly to estimate GPP and R. Methane emissions were also examined from both the day and night samples. GPP averaged 13.94 ± 0.79 g CO2-C m-2 day-1, while respiration averaged 12.55 ± 0.54 g CO2-C m-2 day-1. GPP differed by both month sampled and plant community sampled (p<0.001 and p=0.002, respectively). Median methane emissions from the sample plots was 12.81 mg CH4-C m-2 day-1 and differed by month (p<0.001) and soil temperature (p=0.049). Combining all three carbon fluxes, there is an overall uptake of carbon within the sample plots, suggesting that the wetlands are acting as overall carbon sinks. There was a net retention of carbon in the two experimental wetlands ranging from 160-195 g C m-2 year-1 in 2010 and 164-171 g C m-2 year-1 in 2011.