Carbon Balance in Soils under Conifers and Broadleaved Species within La Sierra, Dominican Republic

Our research assesses the effects of four forest species, namely Swietenia macrophylla King, Swietenia mahogany (L.) Jack., Pinus occidentalis Swartz, and Pinus caribaea Morelet var. Caribaea, on organic carbon (OC) dynamics and carbon dioxide equivalent balance (BCO2 Eq.) in the soils beneath these species. Reforestation projects in the study region cover 1,200, 543, 770, and 1,152 hectares, with these four species, respectively, being the most relevant species in reforestation projects within the country. To determine the BCO2 Eq. per unit area, we compared the greenhouse gas (GHG) fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) with the OC reserves found in the mineral soil to a depth of 30 cm and in the forest litter. For 18 months, we conducted field measurements in sixteen stands, four for each species. Our results indicate that S. macrophylla absorbed the highest amount of CO2, while S. mahogany released the highest amount into the atmosphere. BCO2 Eq. from S. macrophylla soils was -23.19 metric tons of CO2 Eq. ha-1 year-1, while for P. occidentalis, S. mahogany, and P. caribaea, the corresponding quantities were -3.838, -2.299, and +0.982, respectively. During the measurement period, soils under S. macrophylla, P. occidentalis, and P. caribaea were net sinks of CO2 Eq., while soils under S. mahogany behaved as a source. The absorption rate of CO2 Eq. from the atmosphere was approximately 6, 10, and 24 times higher in S. macrophylla when compared to the respective rates of P. occidentalis, P. caribaea, and S. mahagony.