The interacting effects of temperature and plant community type on nutrient removal in wetland microcosms

摘要

Four wetland plant species (Scirpus validus, Carex lacustris, Phalaris arundinacea, and Typha latifolia) were grown in monocultureand as a four-species mixture to compare effectiveness of nutrient removal in controlled 18.93-l outdoor subsurface treatmentwetland microcosms. A nutrient treatment that mimicked single-resident domestic effluent consisted of two levels of nitrogen (N)and phosphorus (P) [low (56 mg/l N and 31 mg/l P) and high (112 mg/l N and 62 mg/l P)] of nutrient solution applied three timesweekly. The plants were established and maintained for one year before the nutrient treatment and monthly water samplingcommenced; water sampling began July 31, 2001 and ended October 23, 2001. We tested four hypotheses: (1) vegetated microcosmsare more effective at reducing concentrations of total N and total P from soil leachate than unvegetated, (2) there is a differentialspecies effect on the potential to reduce N and P, (3) plant mixtures are more effective than monocultures at reducing N and P, and(4) the microcosms will be least effective at reducing N and P concentrations in October compared to August. We found support forhypotheses 1, 2, and 4, but our results are inconclusive for the third hypothesis. Total N and total P in the soil leachate weresignificantly higher from unvegetated microcosms compared to vegetated. S. validus was most effective and P. arundinacea wasgenerally least effective at reducing N and P in monocultures, with treatment capabilities similar to unvegetated microcosms. Thefour-species mixture was generally highly effective at nutrient removal, however the results were not significantly different from themonocultures. At the end of the growing season (October) treatment efficiency was significantly less than earlier months, especiallyfor the unvegetated treatment.