Document: SCO-3-75-7

Channelization effects on floodplain nutrient levels.

FRANKLIN, S.B.* ¹, S.R.PEZESHKI ¹, N.C.G.VAN GESTEL ¹, M.ELCAN ¹ and J.A.KUPFER ²

University of Memphis, Memphis, TN 38152, U.S.A. ¹
University of Arizona, AZ 85721, U.S.A. ²

Abstract:
The effects of channel alterations on adjacent floodplain functions are not well understood. We were interested in the effects of channels and levees on floodplain nutrient pools in an effort to examine two biogeochemical functions that floodplains perform; nutrient retention and transformation. We specifically examined nutrient pools in soils and leaf fall, and further examined redox potential in soil. Six low-gradient river floodplains in western Tennessee were chosen based on their historical alterations: Two were channelized, two were channelized and leveed, and two were unchannelized (considered a reference standard). Four plots were located on each river: Two depressional and two nondepressional sites. Differences in nondepressional sites varied between rivers, as channelized and leveed floodplains often had little topographic variation. Analyses suggest that channelized rivers with levees had significantly greater soil redox potential than rivers channelized only. This difference was especially pronounced in June, prior to a severe drought occurring in July and August. On three of the six rivers, soil redox potential was significantly lower in depressional areas. On the other three rivers, no significant difference was found. There was a general decreasing trend in soil nutrients between channelized sites, channelized and leveed sites, and unchannelized sites. That is, unchannelized rivers generally had lower soil nutrient pools (exchangeable) than modified rivers, and the soil nutrient pools of these unchannelized sites were remarkably similar. The differences between the river manipulations did not hold for the leaf fall nutrient pool data. Some nutrients showed the opposite trend. For instance, the one unchannelized river had the highest zinc, and the other had the highest manganese and aluminum in their leaf fall. No consistent patterns were found relating to river alterations or depressional microsites.

Keywords: Floodplains, river alterations, forest nutrient pools

This abstract is being presented at: 10:30 AM in session:
RIPARIAN ECOLOGY