Studies of wetlands developing on phosphate mined lands and under controlled greenhouse conditions were conducted to evaluate the role of early successional species in ecosystem development. Persistence under reduced light, nutrient cycling, and nutrient sequestration were studied, as well as their role in developing and altering the physical environment (microtopography). Finally, measurable wetland attributes showing directional change with time were identified, and models of successional trajectories were established from attribute data.
These studies suggested that early successional species may facilitate ecosystem development and are not persistent within the developed wetland ecosystem. After three years under low light levels mimicking canopy closure (30% of available sunlight), primrose willow and cattails decreased in abundance and vigor. Cattail (Typha spp.) and primrose willow (Ludwigia peruviana) contributed greater nutrient sequestration than other common herbaceous species. Constructed wetlands dominated by primrose willow and by Carolina willow (Salix caroliniana) had higher microtopographic relief than systems where these species were not present. Native vines showed similar successional trends and may contribute rather than detract from ecosystem development.
Several wetland attributes exhibited sufficient directional change with time so that their trajectories show promise as a means of evaluating success. These include trajectories for tree height, dbh, canopy cover, soil organic matter content, and bulk density.
Mark T. Brown et al., University of Florida Center for Wetlands. August 2002.