Enhancement of Floral Species Richness in Glaciated Prairie Temporary Wetlands

Restored semipermanently flooded Prairie Pothole Region wetlands frequently recover plant species richness resembling undisturbed conditions. However, plant species richness in temporarily flooded wetlands often recovers poorly due to colonization by aggressive undesirable species. This study was conducted during 1995 and 1996 in eastern South Dakota to assess the effectiveness of several treatments designed to improve the species richness and coverage of desirable temporarily flooded wetland vegetation. To assess the effectiveness of these treatments on reed canarygrass (Phalaris arundinacea L.), 2 of the temporary wetlands selected had plant communities dominated by this undesirable colonizing species. Experimental treatments were a combination of (1) application of glyphosate herbicide (spray); (2) cutting and removal of vegetation (mow); (3) disturbance of soil using a field disc (disc); (4) application of seed purchased from a seed vendor (purchased seed); and (5) application of seed collected locally (collected seed). The study consisted of 2 experiments, both randomized complete block designs. Experiment 1 had 4 blocks with the following 3 treatments: (1) spray-mow-disc-collected seed; (2) spray-mow-disc-purchased seed; (3) mow-disc-purchased seed; and 1 control. Experiment 2 had 2 blocks with treatments identical to the first experiment, except that discing was not conducted due to soil saturation. The species composition and abundance of plants found within each wetland\u27 s seed bank were determined by conducting a greenhouse seedling emergence experiment. To assess the effectiveness of each treatment, species were grouped as either desirable or undesirable . Analysis of variance was used to determine treatment and treatment by year interaction effects on the coverage and species richness of desirable, undesirable, and those species which were seeded. The Spray/Purchased seed treatment resulted in the highest coverage and species richness of desirable and seeded species for Experiment 1. However, herbicide application did not significantly improve the establishment of desirable species, since the Purchased seed treatment of Experiment 1 was statistically as effective. The discing procedure significantly reduced the coverage of undesirable species, but also promoted an increase in the species richness of these species. No treatment was effective at reducing the coverage or frequency of reed canarygrass. For Experiment 2, the Spray/Purchased seed treatment was most effective at increasing the species richness of desirable species and the coverage and species richness of seeded species. The Purchased seed treatment for Experiment 2 resulted in the highest coverage of desirable species and the lowest coverage of undesirable species. Herbicide application impeded the regeneration of light-competing vegetation and helped to improve establishment of seeded species