Dominant Regulatory Factors of Greenhouse Gas Emission from Tropical Peatlands in Sarawak

Many dominant regulatory factors affecting the emission of GHG between peat soils and the atmosphere in tropical peatlands in Sarawak have been identified. Thus, the main objective of the paper is to review and examine these dominant regulatory factors i.e. forest types and peat characteristics, types of crops, drainage, compaction, nitrogen fertilization and environmental variables. The mixed peat swamp forest has the lowest rate of CO2 emission of 134.03 mg C m hr amongst the various types of forest but the highest emissions of methane (0.1935 mg C m hr) and nitrous oxide (0.0549 mg N m hr). The soil CO2 flux was highest in the forest ecosystem (2.1 kg C m yr) followed by oil palm (1.5 kg C m yr) and sago (1.1 kg C m yr) (Melling et al., 2005a). Only oil palm ecosystem was a CH4 sink with an uptake rate of -15.14 mg C m yr. The highest annual N2O emissions were observed in the sago ecosystem. Drainage increased soil aeration, which improves soil respiration rates by the greater availability of oxygen for soil microorganisms. However, drainage decreases CH4 flux because the lower ground water table would result in a thicker aerobic top layer in the soil. Soil compaction reduces gas permeability in the soils resulting in higher methane consumption and thus, lower methane emission in oil palm ecosystem. Melling et al. (2006) found that urea applications increased CH4 emissions in the month of application and the emissions remain slightly higher a month later before the effect disappeared in the third month after application. There was no dominant environmental factors or regulatory factors that can be related to each GHG flux in all ecosystems or forest types on deep tropical peatlands in Sarawak.