Evaluation of Different Grasses to Restore Wetlands and Control Weed Species after Pipeline Construction

Joseph M. McMullen, Mark E. Burger, and Scott D. Shupe

In the northeastern United States, two invasive weed species of vegetation, common reedgrass (Phragmites australis) and purple loosestrife (Lythrum salicaria), invade and degrade wetlands. Soil disturbance during pipeline construction can promote the invasion of these aggressive weed species into wetland areas. To assess this concern, a three-year research project was implemented to assess the ability of three different restoration grasses — Japanese millet (Echinochloa crusgalli), annual ryegrass (Lolium spp.), and redtop (Agrostis gigantea) — and natural regeneration in their ability to stabilize disturbed wetland areas and restrict the invasion of weed species. Organic soil wetlands along a pipeline constructed in upstate New York in 1994 were studied. Grasses were planted in randomly selected plots in the summer of 1994. Vegetation data were collected along permanent transects in each plot in 1994, 1995 and 1996. Initial differences among grass treatments were noted, especially in the millet plots where total vegetation cover was high, but plant species richness was low. By the third year of study, dominant plant species composition was identical in all treatment plots, including untreated control. Loosestrife invaded the wetland areas and by the third year had somewhat similar values among all treatments. Common reedgrass never invaded the disturbed wetland areas. Results of the study question the need for and benefit of planting restoration grasses in wetlands where topsoil and grades are restored.

Keywords: Weed species, common reedgrass, purple loosestrife, pipeline construction, wetland restoration, Japanese millet, annual ryegrass, redtop, wetland vegetation, wetlands disturbance, organic soil, rights-of-way