An ecological assessment of the relationships between landscape structure and depressional-wetland ecosystem status along environmental gradients in Central Ohio

Three different analysis techniques are used to understand better the relationships between depressional wetlands and their surrounding landscape: (1) the range of current conditions among depressional wetlands and their local environments are explored by comparing means and extreme values for physio-chemical and plant community characteristics; (2) the range of current conditions among depressional wetlands and their local environments are explored by comparing the full range (or gradient) of physio-chemical and plant community characteristics; and (3) the range of conditions over the past 60 years are explored at a single depressional wetland and compared to current plant community characteristics. The physio-chemical differences observed among these 31 wetlands suggest that the sole use of the hydrogeomorphic classification methodology may not account for ecologically distinctive differences among central Ohio's depressional wetlands and may ignore the influences of landscape factors on wetland physio-chemistry. Depressional wetlands also have distinctly different plant community characteristics; within the plant communities of depressional wetlands, taxa richness is negatively associated with mean-distance to the nearest wetland for all plant guilds except submersed wetland plants. Highly significant positive associations were also observed between the areal proportion of areas of open water in the vicinity of wetland sites and the proportion of submersed aquatic plant taxa, native submersed plant species, submersed perennial:annual ratio, and bird-dispersed submersed species at the site. Within the bird-dispersed plant guild, genus and family richness is negatively associated with the mean distance of neighboring wetlands, suggesting that bird-dispersed plant taxa may be more abundant at less isolated wetland sites. Temporal studies of a single urbanized depressional wetland suggest that severed landscape connections and habitat destruction in the recent past may be responsible for changes in the herbaceous plant community. However, there may be a time lag in the response of the woody plant community to these disturbances. The combined results of these studies have important implications for natural resource professionals who rely solely on hydrogeomorphic classifications, total plant community measurements, and current environmental conditions to assess wetland ecosystems.