Emergent plant decomposition and sedimentation: response to sediments varying in texture, phosphorus content and frequency of deposition

Abstract

The impact of sedimentation on the decay of Typha latifolia, Typha angustifolia and Sparganium eurycarpum litter was evaluated in two Michigan wetlands. In one wetland, T. latifolia decay was studied among replicates of three treatments (unsedimented treatment, one-time sediment application (sandy loam) and multiple sediment applications). In the second wetland, decomposition of T. angustifolia and S. eurycarpum, exposed 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 phosphorus-enriched clay suppressed S. eurycarpum decay by about 6–8% over 117 days; however, T. 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, however, were higher under unsedimented regimes than sedimented regimes. Among measures of water quality (dissolved oxygen, NH 4-N, NO 3-N, total P and suspended solids concentrations), only NH 4-N demonstrated a significant difference among treatments at the T. latifolia field site (0.13 mg NH 4-N l −1 higher in the unsedimented treatment than the sedimented treatments).