Abstract
For agricultural purposes, the drainage and deforestation of Southeast Asian peatland resulted in high greenhouse gases’ (GHGs, e.g., CO2, N2O and CH4) emission. A peatland regenerating initiative, by rewetting and vegetation restoration, reflects evidence of subsequent forest recovery. In this study, we compared GHG emissions from three Malaysian tropical peatland systems under the following different land-use conditions: (i) drained oil palm plantation (OP), (ii) rewetting-restored forest (RF) and (iii) undrained natural forest (NF). Biweekly temporal measurements of CO2, CH4 and N2O fluxes were conducted using a closed-chamber method from July 2017 to December 2018, along with the continuous measurement of environmental variables and a one-time measurement of the soil physicochemical properties. The biweekly emission data were integrated to provide cumulative fluxes using the trapezoidal rule. Our results indicated that the changes in environmental conditions resulting from draining (OP) or rewetting historically drained peatland (RF) affected CH4 and N2O emissions more than CO2 emissions. The cumulative CH4 emission was significantly higher in the forested sites (RF and NF), which was linked to their significantly higher water table (WT) level (p < 0.05). Similarly, the high cumulative CO2 emission trends at the RF and OP sites indicated that the RF rewetting-restored peatland system continued to have high decomposition rates despite having a significantly higher WT than the OP (p < 0.05). The highest cumulative N2O emission at the drained-fertilized OP and rewetting-restored RF sites was linked to the available substrates for high decomposition (low C/N ratio) together with soil organic matter mineralization that provided inorganic nitrogen (N), enabling ideal conditions for microbial mediated N2O emissions. Overall, the measured peat properties did not vary significantly among the different land uses. However, the lower C/N ratio at the OP and the RF sites indicated higher decomposition rates in the drained and historically drained peat than the undrained natural peat (NF), which was associated with high cumulative CO2 and N2O emissions in our study.
Highlights
Greenhouse gas (GHG) emissions cause global warming, as well as contributing to the loss of carbon (C) and nitrogen (N) from soils
There was no significant different in the Water-filled pore space (WFPS) between sites, the natural peat swamp forest (NF) was slightly higher than the oil palm plantation (OP) and restored forest (RF) sites
Our results indicate that the significant differences in the environmental conditions of the drained, rewetting-restored and natural peatland systems affected CH4 and nitrous oxide (N2 O) the most, with little effect on CO2 emissions
Summary
Greenhouse gas (GHG) emissions cause global warming, as well as contributing to the loss of carbon (C) and nitrogen (N) from soils. Three of the most important GHGs are carbon dioxide (CO2 ), methane (CH4 ) and nitrous oxide (N2 O), but they have different atmospheric lifetimes and radiative efficiencies. Carbon dioxide and N2 O are long-lived atmospheric gases, the radiative efficiency of N2 O molecules is much greater than that of CO2 [1]. Methane has only a short lifetime (12 years), but its radiative efficiency is 137-fold greater than CO2 when including indirect effects [1]. Previous studies have reported that GHG emissions from tropical peatlands are related to peat composition, as well as subsidence and degradation due to human activities and land-use change that affect aspects such as water table (WT) levels, vegetation cover and fire activities [7,8,9]
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