Plant community establishment in a restored wetland: Effects of soil removal

Question: This study investigated the establishment of wetland plant assemblages following soil removal and restored hydrology in a former agricultural field. The following questions were posed. Does plant community composition differ as a result of soil removal? Does soil removal reduce the frequency of non-wetland plants? Does soil removal reduce the frequency of non-native invasive plants? Location: The Panzner Wetland Wildlife Reserve (PWWR) in Summit County, northeastern Ohio, USA. Methods: During 2000-2001, restoration was conducted on two adjoining fields (3.9 ha total) by excavating the upper 40-50 cm of soil layer and establishing 12 10 m × 10 m undisturbed control plots. Preliminary data included seed bank composition and soil organic matter, estimated from three different soil depths on the control plots. In spring 2004, a 10 m × 10 m soil-removed plot was established adjacent to each control plot. Plant percent cover of all species was estimated within the center 5 m × 5 m of every plot. Above-ground biomass of all species from three 0.25-m2 quadrats was collected. Environmental water measurements included water depth, temperature, dissolved oxygen, pH, and conductivity. Results: The top 10 cm of soil contained the most seeds, the highest species diversity, the greatest proportion of annual to perennial plants, and the lowest organic content. Obligate and facultative wetland plants were found in soil-removed plots while facultative upland and upland plants were found in control plots. The only plots with arable weeds were the control plots. However, plant communities on soil-removed plots in the North field, which had a higher elevation (ca. 15-20 cm), had a different species composition than soil-removed plots in the South field. Conclusions: The results of a controlled, replicated large-scale study on the effects of soil removal showed that soil removal altered both the biotic and abiotic environment, but that the proximity to the water table was the primary controlling factor in the assembly of plant communities.