Submitted to: Society of Wetland Scientists
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2006
Publication Date: 7/1/2006
Citation: Kroger, R., Holland, M.M., Moore, M.T., Cooper, C.M. 2006. Plant senescence: a mechanism for nutrient release in temperate agricultural wetlands. Society of Wetland Scientists 27th International Conference, Cairns, Australia. p. 136. Interpretive Summary: Abstract only. Interpretative summary not required.
Technical Abstract: Agriculture drainage ditches are primary intercept wetlands in amelioration of nutrient pollution from agricultural fields. Drainage ditches, as integral components of the agricultural landscape, remove surface run-off and act as major conduits of nutrients from agricultural lands to receiving waters. These ditches support numerous species of wetland plants, providing additional surface area for microbial interactions as well as acting in a small, yet important assimilatory capacity. However, a wetland plant’s nutrient uptake function is negated in winter with significant seasonal vegetative die-back and the release of assimilated nutrients back into the aquatic environment. We tested the hypotheses of luxury uptake whereby plants given the opportunity will firstly assimilate higher loads of nutrients, such as nitrogen and phosphorus, and whether with subsequent decomposition these loads are released back into the water column. When exposed to elevated (>2 mg/L N & P) runoff, Leersia oryzoides assimilated significantly higher concentrations of nitrogen (p < 0.001) and phosphorus (p < 0.001) in above-ground biomass as compared to non-enriched plants (<0.05 mg/L N & P). Subsequently, senescence of enriched above-ground biomass yielded significantly higher concentrations of phosphorus (2.19 mg P/L+ 0.84). Using L.oryzoides as a model it appears that the assimilatory role of wetland plants is negated in environments where seasonal dieback re-releases nutrients back into the system.