Recovery of Mangrove Ecosystem Carbon Stocks Through Reforestation at Abandoned Shrimp Pond in Southeast Thailand

Abstract

Mangrove forests play an important role in the carbon cycle by sequestering atmospheric CO2 and storing it as carbon in plant materials and sediments. We evaluated the ecosystem carbon stocks and carbon accumulation rates of an 18-year mangrove reforestation site located in abandoned shrimp ponds of Southeast Thailand. Consequently, carbon stocks in biomass and soil increased drastically through reforestation compared to those in nonplanted area (NPA). Soil carbon stocks at 1.0-and 2.0-m depth after 18 years were approximately 2.1 times and 1.8 times higher than those in NPA. Soil carbon stocks at 1.0-m soil depth increased gradually across the mangrove chronosequence over 18 years. Ecosystem carbon stocks at the 18-year site were 179.6 ± 40.5 Mg C·ha−1 to 1-m soil depth and 325.0 ± 77.6 Mg C·ha−1 to 2-m soil depth, which was higher compared to those in NPA [69.3 ± 8.0 Mg C·ha−1 (1 m) and 157.8 ± 10.9 Mg C·ha−1 (2 m)]. The ecosystem carbon stocks were lower than the global mean value, but the carbon accumulation rate had a comparatively high value. The total carbon accumulation rate after 18 years was 9.9 Mg C·ha−1·year−1 to soil 1-m depth and 18.1 Mg C·ha−1·year−1 to 2-m depth. Moreover, correlation relationships between soil carbon stock and physicochemical properties such as pH, electrical conductivity, redox potential, bulk density, elapsed year, and temperature in NPA and reforestation sites were confirmed. Therefore, the recovery of carbon stocks through mangrove reforestation in abandoned shrimp pond can contribute to blue carbon ecosystem restoration as nature-based solutions.