科研之友
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摘要
Plant diversity in groundwater-fed wetland ecosystems is typically extraordinarily high, yet the biogeochemical controls of this diversity are still incompletely understood. We hypothesized that fine-scale variation in sulfide would influence plant community composition via direct phytotoxicity and indirect mediation of phosphorus release from iron, coupled with gradients in other chemicals such as calcium. We measured porewater chemistry and plant species composition at 400 locations within a calcareous rich fen in central New York State. Groundwater-derived calcium (Ca2+) and sulfate and redox-sensitive sulfide and ferrous iron (Fe2+) showed high heterogeneity. Phosphorus availability was limited and not readily traceable to toxic sulfide, whereas nitrogen (TDN) was more abundant than expected. Using the corrected Akaike information criterion to select between competing models of toxic, nutrient, and mixed-chemistry influences on vegetation, we found that hydrogen sulfide explained decreases in total plant cover, cover of the three most frequently occurring species, dicot species density, plant height, and litter accumulation. Furthermore, sulfide coupled with calcium and phosphorus to explain plant species density and composition. Sulfide was more likely to explain decreased cover of dominant species than rare species. The presence and cover of uncommon species was often unexpectedly explained best by Fe2+ and sulfate, but all models of plant responses with environmental predictor variables were better than the "null" model of mean plant response that lacked environmental variables. An integrated geochemical assessment of coupled groundwater chemistry, redox-sensitive chemistry, and nutrient influences on plants demonstrated the importance of phytotoxic sulfide in explaining plant species density and composition.
- 出版日期2013-9
