Establishment, persistence, and management implications of experimental wetland plant communities

Abstract

We inoculated 120 wetland microcosms representing 24 different environmental treatments with seeds from a carefully chosen pool of 20 wetland plant species. The treatments were chosen to represent a variety of riverine and lacustrine wetlands, including those with slow-growing, rare species. In the first season, an annual (Bidens cernua) was most abundant in all the microcosms. Both flooding and high fertility negatively effected the other species establishment. Short-term information about establishment was not predictive of longer-term trends. After 5 years, most of the microcosms became dominated byLythrum salicaria and, when this occurred, other dicot species were extirpated. After 5 years, flooding and fertility remained the main factors affecting species composition in the microcosms.Lythrum establishment (and dominance) was minimal when fertility was low and when the microcosms were seasonally flooded. Establishment and growth ofTypha angustifolia was poor, and this was attributed to coarse substrate. These results suggest possible measures to minimize the growth of unwanted plant species in created or restored wetlands. Our results also suggest, that high diversity, low biomass wetlands will be difficult to create; therefore, protection of such wetlands may deserve a higher priority.