Abstract
Drainage is a major means of the conversion of tropical peat forests into agriculture. Accordingly, drained peat becomes a large source of carbon. However, the amount of carbon (C) loss from drained peats is not simply measured. The current C loss estimate is usually based on a single proxy of the groundwater table, spatially and temporarily dynamic. The relation between groundwater table and C emission is commonly not linear because of the complex natures of heterotrophic carbon emission. Peatland drainage or lowering groundwater table provides plenty of oxygen into the upper layer of peat above the water table, where microbial activity becomes active. Consequently, lowering the water table escalates subsidence that causes physical changes of organic matter (OM) and carbon emission due to microbial oxidation. This paper reviews peat bulk density (BD), total organic carbon (TOC) content, and subsidence rate of tropical peat forest and drained peat. Data of BD, TOC, and subsidence were derived from published and unpublished sources. We found that BD is generally higher in the top surface layer in drained peat than in the undrained peat. TOC values in both drained and undrained are lower in the top and higher in the bottom layer. To estimate carbon emission from the top layer (0–50 cm) in drained peats, we use BD value 0.12 to 0.15 g cm−3, TOC value of 50%, and a 60% conservatively oxidative correction factor. The average peat subsidence is 3.9 cm yr−1. The range of subsidence rate per year is between 2 and 6 cm, which results in estimated emission between 30 and 90 t CO2e ha−1 yr−1. This estimate is comparable to those of other studies and Tier 1 emission factor of the 2013 IPCC GHG Inventory on Wetlands. We argue that subsidence is a practical approach to estimate carbon emission from drained tropical peat is more applicable than the use of groundwater table.
Highlights
Carbon loss in drained peat occurs globally, in tropical regions
Low emission values in the agricultural land can be attributed to the natural hydrophobicity of selected aromatic organic compounds such as lignin [21], in that when the tropical peat soil particles are not dissolved in water and the particles become recalcitrant for biological decomposition [15,73]
Despite complex issues and views on peat degradation, ecological degradation of tropical peat forests consists of hydrological change and alteration of peat soil properties
Summary
Carbon loss in drained peat occurs globally, in tropical regions. Research has shown that the groundwater table does not always positively correlate with carbon emission [11,12] Other factors, such as soil moisture, soil pH, and fertilizer application [6,13,14,15], are significant predictors in estimating carbon loss from drained peat soil. Continuous monitoring of groundwater table and carbon emission is not practical in the tropical peatlands in Southeast Asia due to expensive automatic chambers, lack of electrical power in remote peat area, and lack of skilled human. A variety of vegetation formations occurs in a tropical peat swamp in Southeast Asia. The removal of vegetation in the tropical peat swamp forest causes the depletion of OMs, which are necessary for maintaining peat accumulation. Under anthropogenic disturbances, such as deforestation, drainage, and fires, peat accumulation stops [35] and, peats act as a source of carbon to the environment [36,37,38]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
