PLANT COVER COMMUNITIES IN A HYDROCHEMICALLY DIVERSE AQUIFER SYSTEM, NORTH RIVER WATERSHED, SE MASSACHUSETTS

The plant communities of interest lie within the Old Pond Meadows aquifer, a roughly 2 square mile area, characterized by low lying fresh water wetlands, underlain by a 20ft thick layer of peat deposits and forested uplands, a glacial outwash delta, perched approximately 10 ft above the lowlands. Surface and ground waters in the lowlands are more reducing, higher in iron and manganese (4ppm and 1ppm, respectively; compared to water standards of 0.3ppm and .05ppm), while in the uplands they are more oxidizing with iron and manganese below the contaminant levels. The boundary between these hydrochemical zones coincides with the line separating the two geomorphic and ecologically diverse domains that encompasses the plant communities subject of this study. Nested circular plots with a 30-foot radius were used to characterize the plant cover of both domains. Groundcover, shrubs and saplings and trees were individually surveyed and percent cover and percent dominance was determined for each species. The uplands are characterized by Red Oak (Quercus rubra) 16.2%, Eastern Hemlock (Tsuga canadensis) 11.4%, White Pine (Pinus strobus) 16.6% and an understory of Common Greenbrier (Smilax rotundifolia) 17.25%, Bracken Fern (Pteridium aquilinum) 10.5% and Tree Clubmoss (Lycopodia obscurum) 10%. The wetland is distinguished by Red Maple swamps (Acer rubrum) 15%, including dense stands of Broadleaf Spirea (Spiraea litifolia) 32%, Eastern Joe-Pye weed (Eupatorium dubium) 20% and the reed Carex crinita, 32%. The make-up of the upland community is representative of communities in similar, well-drained environments. The composition of the wetlands also typifies wetland communities under similar conditions. The differences in make-up of the two plant communities appear to clearly reflect the differences in the ecological domains present with no discernable evidence that would bear on the presence of diverse hydrochemical environments. This study is a two phase project; phase two, currently in progress, examines the role of the plant communities in nutrient cycling within the context of the aquifer hydrochemistry.