PARENT SESSION
Oral Session # 74: Riparian Ecology I: Nutrient Cycling; Decomposition.
Presiding: K Bushaw-Newton
Thursday, August 7. 8:00 AM to 11:30 AM, SITCC Meeting Room 205.

Chemical characteristics of river and floodwaters of forested floodplains in the SE United States.

Dress, William^*,1, Whitmire, Stefanie^{1, 2}, Walbridge, Mark¹, ¹ West Virginia University, Morgantown, WV² Kellogg Biological Station, Hickory Corners, MI

ABSTRACT- Forested floodplains are common wetland ecosystems bordering rivers and streams that receive water from the adjacent river during periods of high streamflow (bankfull discharge). Floodplain sites were established adjacent to two types of riverine systems (alluvial, blackwater), with underlying parent materials of two ages (young –Pliocene-Miocene 2-24 mya, old –Cretaceous 66-144 mya) (n = 3 per river type - parent material combination). River water samples were collected to characterize baseflow stream chemistry in anticipation of sampling flooding events. Water samples were also collected from 2 sites that experienced flood events in October 2002: Chicod Creek (young-blackwater system) and Cape Fear River (old-alluvial system). Blackwater rivers had greater dissolved organic carbon (DOC) concentration than alluvial rivers (14.3 vs. 5.2 ppm, respectively); concentrations of inorganic ions (i.e. NH₄⁺, NO₃^-, PO₄^3-) were highly variable among the river systems. In the Chicod Creek floodplain, concentrations of NH₄⁺, NO₃^-, and PO₄^3- were significantly lower within the floodplain than in river water collected both above and below the floodplain, but there were no differences in pH, conductivity or DOC between floodplain and river water samples. In the Cape Fear floodplain, pH (5.65 vs. 6.62, respectively) and conductivity (67.1 vs. 122.3, respectively) were significantly lower within the floodplain, and DOC concentrations (24.6 vs. 12.9 ppm, respectively) were significantly higher. Concentrations of both NH₄⁺ and NO₃^- were reduced by 95-96% within the floodplain, but there were no differences in the concentration of PO₄^3-. Differing results from these flooding events are compared with soil and baseflow water characteristics from the two forested floodplain ecosystems.

Key words: water, forest floodplain, phosphorus