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

Abstract

The highly dynamic, fine root component of forested wetland ecosystems has received inadequate attention in the literature. Characterizing fine root dynamics is a challenging endeavor in any system, but the difficulties are particularly evident in forested floodplains where frequent hydrologic fluctuations directly influence fine root dynamics. Fine root (≤3 mm) biomass, production, and turnover were estimated for three soils exhibiting different drainage patterns within a mixed‐oak community on the Coosawhatchie River floodplain, Jasper County, South Carolina. Within a 45‐cm‐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., fine root biomass in well‐drained soil > intermediately drained soil > poorly drained soil). Fine root productivity was measured for 1 yr using minirhizotrons 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, 1.8, and 0.9 Mg ha−1 yr−1 in the well‐drained, intermediately drained, and poorly drained soils, respectively. Results from minirhizotrons indicated that fine roots in well‐drained soils grew to greater depths while fine roots in poorly drained soils were restricted to surface soils. Minirhizotrons also revealed that the distribution of fine roots among morphological classes changed between well‐drained and poorly drained soils.