Fine Root Productivity and Dynamics on a Forested Floodplain in South Carolina

The highly dynamic, fine root component of forested wetland ecoi&g fine root dynamics is a challenging endeavor in any system, but the dilficulties are particularly evident in forested floodplains where frequent hydrologic fluctuations directly influence fine root dynamics. Fine root (53 mm) biomass, production, and turnover were estimated for three soils exhibiting different drainage patterns within a mixedoak community on the Coosawhatchie River floodplain, Jasper County, South Carolina. Within a 45cm-deep vertical profile, 74% of total fine root biomass was restricted to the upper 15 cm of the soil surface. Fine root biomass decreased as the soil became less well drained (e.g., tine root biomass in well-drained soil > intermediately drained soil > poorly drained soil). Fine root productivity was measured for 1 yr using minirhiitrons and in situ screens. Both methods suggested higher fine root production in better drained soils but showed frequent fluctuations in fine root growth and mortality, suggesting the need for frequent sampling at short intervals (e.g., monthly) to accurately assess fine root growth and turnover. Fine root production, estimated with in situ screens, was 1.5, l-g, and 0.9 Mg ha-’ yr-’ in the well-drained, intermediately drained, and poorly drained soils, respectively. Results from minirhizotrons indicated (hat fine roots in well-drained soils grew to greater depths while fine roots in poorly drained soils were restricted to surface soils. Minimizotrons also revealed that the distribution of fine roots among morphological dasses changed between well-drained and poorly drained soils. P WETLAND ECOSYSTEMS has been the focus of numerous studies. Most commonly, productivity is estimated using aboveground parameters such as litterfall and stemwood production (B&son et al., 1980; Conner and Day, 1992; Conner et al., 1993; Conner, 1994; Megonigal et al., 1997). Many investigators have acknowledged, however, that failure to include belowground data will seriously underestimate forest ecosystem productivity (Vogt et al., 1986a; Day and Megonigal, 1993). It has been suggested that fine root production accounts for up to 75% of total net primary production (NPP) in some forests (Nadelhoffer and Raich, 1992). Similar to aboveground foliage, large amounts of fine roots die annually and can contribute a quantity of litter similar in magnitude to foliar litter (McClaugherty et al., 1984). Fine root dynamics, therefore, represent a significant source of energy and nutrient flow through forested systems, particularly for those TerreU T. Baker III, College of Agriculture and Home Economics, New Mexico State Univ., Box 30003, MSC 3AE, Las Cruces, NM 88003-8003; William H. Conner, Baruch Forest Science Institute, P.O. Box 596, Georgetown, SC 29442; B. Graeme Lockaby, School of Forestry, Auburn Univ., 108 M.W. Smith Hall, Auburn, AL 36849. 5418; John A. Stanturf, USDA-Forest Service, Center for Bottomland Hardwoods Research, P.O. Box 227, Stoneville, MS 38776; Marianne K. Burke, USDA-Forest Service, Southern Research Station Center for Forested Wetlands Research, 2730 Savannah Hwy., Charleston, SC 29414. Received 11 Mar. 1999. *Corresponding author (ttbaker@