Belowground Carbon Density of Lowland Colombian Peatlands

Peatlands hold approximately 30% of carbon stored in soil, on only 3% of total land area. Tropical peatlands are vulnerable to effects of climate change and anthropogenic activities. South American peatlands are poorly understood, due to accessibility challenges and limited local resources. In this work, we investigate the carbon content of tropical peatlands in Colombia, and produce the first estimates of belowground carbon density in the peatlands of the eastern Colombian lowlands. We sampled peatlands representing three major vegetation communities: 1) pole forests, dominated by thin, nutrient deprived trees; 2) palm swamps mostly dominated by Mauritia flexuosa, 3) and open peatlands dominated by grass and/or sedge. We estimated peat organic matter (OM) content via loss-on-ignition (LOI) analysis at 10 cm depth intervals from nineteen peat cores for a total of four hundred forty two individual measurements. We paired the OM estimates with sparser measurements of peat carbon content via elemental analysis (flash combustion) from a subset of eight cores and calculated a conversion factor for %OM to %C using linear regression. In order to assess belowground carbon density, we calculated carbon storage per area, using data on peat depth, bulk density and carbon concentration. The loss on ignition ranged from approximately 45% to 90%. Peatland carbon density varied greatly between sites because of highly variable peat depths. Pole forest peatlands had the shallowest peats (mean depth 165 cm) and therefore the lowest mean carbon density (660 Mg / ha; n =11). The deeper palm swamp peats and open peatlands (mean depth = 215 and 350 cm respectively) had similar mean carbon densities (1429 Mg / ha; n = 24 and 2052 Mg / ha; n = 7, respectively). Improved understanding of carbon content in tropical peatlands can inform peatland mapping and conservation planning in this region.