Estimation and uncertainty of recent carbon accumulation and vertical accretion in drained and undrained forested peatlands of the southeastern USA

Abstract

The purpose of this study was to determine how drainage impacts carbon densities and recent rates (past 50 years) of vertical accretion and carbon accumulation in southeastern forested peatlands. We compared these parameters in drained maple-gum (MAPL), Atlantic white cedar (CDR), and pocosin (POC) communities in the Great Dismal Swamp National Wildlife Refuge (GDS) of Virginia/North Carolina and in an intact (undrained) CDR swamp in the Alligator River National Wildlife Refuge (AR) of North Carolina. Peat cores were analyzed for bulk density, percent organic carbon, and 137 Cs and 210 Pb. An uncertainty analysis of both 137 Cs and 210 Pb approaches was used to constrain error at least partially related to mobility of both radioisotopes. GDS peats had lower porosities (89.6% (SD = 1.71) versus 95.3% (0.18)) and higher carbon densities (0.082 (0.021) versus 0.037 (0.009) g C cm −3 ) than AR. Vertical accretion rates (0.10–0.56 cm yr −1 ) were used to estimate a time period of ~84–362 years for reestablishment of peat lost during the 2011 Lateral West fire at the GDS. Carbon accumulation rates ranged from 51 to 389 g C m −2 yr −1 for all sites. In the drained (GDS) versus intact (AR) CDR sites, carbon accumulation rates were similar with 137 Cs (87 GDS versus 92 AR g C m −2 yr −1 ) and somewhat less at the GDS than AR as determined with 210 Pb (111 GDS versus 159 AR g C m −2 yr −1 ). Heightened productivity and high polyphenol content of peat may be responsible for similar rates of carbon accumulation in both drained and intact CDR peatlands.