Abstract
Forested wetlands provide a valuable potential sink for atmospheric carbon, with rates varying between tree communities. Previous studies found that topographic position within the Congaree Swamp (South Carolina, USA) influences flooding regimes, sedimentation processes, and forest community types. We measured aboveground net primary productivity (ANPP) for four distinct tree community types situated within an elevational gradient of this floodplain forest. Twenty data collection sites, blocked by a priori elevational differences, were established along five roughly parallel transects with four 20 × 25-m plots along each transect. Total ANPP was estimated using the sum of annual litterfall (five 0.25 m 2 litter traps/plot) and annual incremental increase in tree biomass. Tree (stems ≥ 10 cm diameter) wood ANPP ranged from 409 to 606 g/m 2 while total litterfall ranged from 678 to 705 g/m 2 . Total ANPP, tree wood biomass, and biomass of reproductive materials (mast) varied annually but sapling biomass, leaf litter, and total litterfall did not. Total and fractional ANPP differed between some forest community types with lowest and highest rates measured in communities occupying high floodplain elevation sites. The community occupying low elevation sites had the lowest rates of total ANPP but highest litter production. The community occupying intermediate floodplain elevation sites had the second highest rates for total, and most measured fractions, of ANPP. Sapling (stems < 10 cm diameter) wood averaged 5.8% of total ANPP for one community, suggesting that, in areas with a moderate to dense sapling layer, sapling wood is an important component of ANPP.