EMERGENT PLANT DECOMPOSITION AND SEDIMENTATION - RESPONSE TO SEDIMENTS VARYING IN TEXTURE, PHOSPHORUS-CONTENT AND FREQUENCY OF DEPOSITION

The impact of sedimentation on the decay of Typha latifolia, Typha ang ustifolia and Sparganium eurycarpum litter was evaluated in two Michig an wetlands. In one wetland, T. latifolia decay was studied among repl icates of three treatments (unsedimented treatment, one-time sediment application (sandy loam) and multiple sediment applications). In the s econd wetland, decomposition of T. angustifolia and S. eurycarpum, exp osed to phosphorus-enriched clay and unenriched clay applications, was assessed in contrast to an unsedimented control treatment. A one-time application of coarse sediment was sufficient to inhibit decay of T. latifolia by about 10% over 470 days. Application of unenriched and ph osphorus-enriched clay suppressed S. eurycarpum decay by about 6-8% ov er 117 days; however, ir. angustifolia decomposition was diminished by only 2% during the same time period. Neither the net flux of nitrogen nor phosphorus mass from decaying tissues was influenced by sediment application. Averages of %N concentration in T. latifolia tissues? how ever, were higher under unsedimented regimes than sedimented regimes. Among measures of water quality (dissolved oxygen, NH4-N, NO3-N, total P and suspended solids concentrations), only NH4-N demonstrated a sig nificant difference among treatments at the T. latifolia field site (0 .13 mg NH4-N l(-1) higher in the unsedimented treatment than the sedim ented treatments). (C) 1998 Elsvier Science B.V. All rights reserved.