PARENT SESSION
Contributed Oral Session 121: Freshwater Wetlands
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 520 C, Level 5, Palais des congrès de Montréal

Sedimentation impacts on wetland soils and vegetation: Results from field and greenhouse studies.

Koning, Catherine^*,1, ¹ koningc@fpc.edu, Rindge, NH, USA

ABSTRACT- Three different experiments were used to test the hypothesis that sedimentation in wetlands alters plant diversity and soil properties. Greenhouse experiments using potting soil and Sagittaria latifolia were used with 0.5-2 cm sediment treatments and controls. Thirty 2 m X 2 m plots were established in a freshwater marsh, and were monitored before and after 1, 2, or 4 cm of sediment were added to 15 plots. Large soil cores were removed from the wetland and monitored in the greenhouse before and after the addition of 2 cm of sediment. Results showed that less than 2 cm of sediment had no effects on the growth of S. latifolia, while 2 cm of sediment significantly increased aboveground biomass but had no effect on matrix potential or oxidation-reduction potential. Field plots showed significant differences in bulk density, organic matter, and phosphorus resulting from addition of sediment but few other differences in soils or vegetation. Soil cores showed a significant difference in bulk density and in matrix potential near the soil surface under wetter conditions but no significant differences in temperature, evapotranspiration, oxidation-reduction potential, or aboveground biomass. The lack of effect seen in the field plots may result from a low effective loading rate relative to the greenhouse experiments, and the dense plant and detrital cover in the wetland. Observed changes in bulk density would alter the hydrologic functions of the wetland if these depths of sediment occurred over a larger area. The tolerable level of sediment for a wetland depends on the structure and function of the individual wetland.

Key words: wetlands, sedimentation, vegetation, hydric soils