ESTABLISHMENT, PERSISTENCE, AND MANAGEMENT IMPLICATIONS OF EXPERIMENTAL WETLAND PLANT-COMMUNITIES

We inoculated 120 wetland microcosms representing 24 different environ mental treatments with seeds from a carefully chosen pool of 20 wetlan d plant species. The treatments were chosen to represent a variety of riverine and lacustrine wetlands, including those with slow-growing, r are species. In the first season, an annual (Bidens cernua) was most a bundant in all the microcosms. Both flooding and high fertility negati vely 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 by Lythrum salicaria an d, when this occurred, other dicot species were extirpated. After 5 ye ars, flooding and fertility remained the main factors affecting specie s composition in the microcosms. Lythrum establishment (and dominance) was minimal when fertility was low and when the microcosms were seaso nally hooded. Establishment and growth of Typha angustifolia was poor, and this was attributed to coarse substrate. These results suggest po ssible measures to minimize the growth of unwanted plant species in cr eated or restored wetlands. Our results also suggest that high diversi ty, low biomass wetlands will be difficult to create; therefore, prote ction of such wetlands may deserve a higher priority.