Greenhouse gas emissions from soil and water surface in different mangrove establishments and management in Ranong Biosphere Reserve, Thailand

Mangrove forest is a blue-carbon-rich ecosystem and source of greenhouse gases (GHG) to the atmosphere. Recent studies of GHG fluxes have been limited for inventory baseline in Thailand. Three GHG emissions were investigated for different mangrove establishment and managements in Ranong province; natural rehabilitation, reforestation, and primary undisturbed forests, due to their differences in carbon and nutrient input as a result of natural and human-induced management. The static closed-chamber technique was used to collected gas sample from soil and water surface interface throughout the year. Total highest GHG emissions were found in the primary undisturbed site (15.40 Mg CO2eq ha−1 yr−1), compared to the reforestation and natural rehabilitation sites (12.60 and 8.53 Mg CO2eq ha−1 yr−1), respectively. The mean average of GHG fluxes at soil–air interface for three mangrove sites were 2.59 ± 0.94 mmol CO2 m−2 h−1, 3.86 ±2.01μmol CH4m−2 h−1, and 2.09 ±1.59μmol N2O m−2 h−1. Whereas at water–air interface, GHG fluxes were 1.66 ± 0.66 mmol CO2 m−2 h−1, 2.47 ±1.47μmol CH4 m−2 h−1, and 2.74 ±1.06μmol N2O m−2 h−1. The undisturbed and reforested sites with good conservation, enriched organic matters and nitrogen nutrients, and large mature trees had significantly higher CO2 emission. CH4 fluxes had significantly higher in the natural rehabilitation site with well growing stage and dominant in low-elevated area with longer inundation periods. Whereas N2O emissions were not statistically different among three mangrove sites. GHG fluxes were recorded higher in soil surface during wet season and rainfall was significantly correlated to CO2, CH4, and N2O emissions. Additionally, the results would be useful in improving mangrove conservation and restoration strategy for GHG emission mitigation and developing an inventory baseline and more accurately estimating of GHG emissions from different mangroves in Thailand.