Influence of microtopography and nutrient limitation on belowground productivity in an old-growth floodplain forest at Congaree National Park, SC, USA

Abstract

This study was designed to improve our understanding of nutrient cycling, C storage and belowground net primary productivity (BNPP) in an old-growth floodplain forest. Four microsites were established parallel to the Congaree River on a floodplain in Congaree National Park, SC, decreasing in elevation from the river (natural levee > flat > transitional > backswamp). Response variables for each microsite included: BNPP (June 2011-March 2013) and results from two fertilized root in-growth core studies (summer 2012, fall 2012). BNPP decreased significantly in the following order: natural levee, flat, transitional, and backswamp. Combined N+P fertilization treatments significantly increased fine root productivity relative to the control, suggesting that N and P co-limit fine root productivity in this floodplain forest. Results indicate that significant differences in root growth patterns and nutrient dynamics occur along an elevational gradient, and water availability has a greater effect on fine root productivity than does a single nutrient.