Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2006
Publication Date: 2/15/2007
Citation: Kroger, R., Holland, M.M., Moore, M.T., Cooper, C.M. 2007. Plant senescence: a mechanism for nutrient release in temperate agricultural wetlands. Environmental Pollution 146:114-119. Interpretive Summary: Eutrophication of water bodies, due to excessive nutrient runoff, is of growing concern in the United States. Laboratory experiments were conducted to examine plant specific uptake of nitrogen and phosphorus during the growing season, followed by natural plant die back in the winter. Samples of water were collected and analyzed for nutrients during the winter to determine how much of the assimilated nutrients were being released when the plants died. When plants exposed to higher concentrations of nutrients during the growing season began to die, they released higher concentrations of nutrients than those plants not exposed to increased nutrient concentrations. Because this research documents plant specific uptake (growing season) and release (senescence) of nutrients, more informed decisions regarding nutrient best management practices can be made by practitioners.
Technical Abstract: Wetland plants nutrient uptake function is negated in winter with significant seasonal vegetative die-back and the release of assimilated nutrients back into the aquatic environment. The current study examined wither Leersia oryzoides, a common wetland plant, accumulates higher than necessary concentrations of nutrients from simulated farm runoff. The study also tested whether with subsequent decomposition, these nutrients are released back into the water column. When exposed to elevated (> 2 mg/L N and P) runoff, L. oryzoides assimilated significantly higher concentrations of nitrogen and phosphorus in above ground biomass as compared to untreated plants. Subsequently, senescence of treated above ground biomass yielded significantly higher concentrations of phosphorus. Using L. oryzoides as our model, this study documents duplicity of certain vegetation in nitrogen and phosphorus assimilation during the growing season and release of phosphorus in the winter.