Drivers of plant community composition in Delta wetlands

Author(s): Shoemaker, C.; Ervin, G.

Intensive agricultural practices in watersheds have the potential to lead to high inputs of non-point source pollutants as a byproduct of nitrogen and phosphorus fertilizer applications. Excess amounts of these nutrients can lead to the eutrophication of receiving water bodies and cause water quality degradation at local, regional, and national scales. To combat this problem, wetland restoration is seen as a potential remediation strategy for reducing nutrient loads entering into larger water bodies. However, wetlands differ in their ability to remove nutrients, in part a result of the plant diversity within wetlands. This study examined natural and restored herbaceous wetlands across the northern Delta in Mississippi to determine drivers of plant community composition and their subsequent effect on water quality. Six naturally occurring wetlands along with 24 restored wetlands enrolled in the Wetland Reserve Program (WRP) were sampled across 12 watersheds stratified by expected nitrogen loads (based on USDA agricultural statistics data). Wetlands were visited in May and August of 2014, with species presence and abundance recorded at 50 sampling plots within each wetland. On the restored sites, redvine (Brunnichia ovata) and trumpet creeper (Campsis radicans) frequently were recorded at 50% or more of our sample points per wetland, while knotweed (Polygonum spp.) was common throughout. Additionally, woody species, such as buttonbush (Cephalanthus occidentalis), swamp chestnut oak (Quercus michauxii), slippery elm (Ulmus rubra) and other bottomland hardwood species were found in greater abundance on the six natural sites compared to restored sites. Ongoing analyses are aimed at investigating components of water quality that may be driving or driven by plant species composition in these wetlands.

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