Judul: The Carbon Dynamics in Rewetted Tropical Peat Swamp Forest
Abstrak: Extensive areas of tropical peat swamp forests (PSFs) have been deforested, degraded, and converted to other land uses. In degraded and drained conditions, the carbon emission is greater than the carbon sequestered, making this ecosystem a significant contributor to greenhouse gas (GHG) emissions from forestry and land-use sectors. Rewetting interventions as part of restoration management have been strongly recommended to mitigate the GHG emissions from degraded and drained tropical PSFs. GHG emission reductions or carbon benefits from the rewetting intervention is calculated by subtracting the GHG emissions from rewetted PSFs with GHG emissions from drained PSFs. Due to the lack of site-specific emission factors (EFs) from rewetted tropical PSFs, default EFs derived from Tier 1 methodology proposed by the Intergovernmental Panel on Climate Change (IPCC) have been widely used to quantify carbon benefit from the rewetting intervention in tropical PSFs. However, GHG emissions are not only affected by the climatic zone and soil nutrient status but also by the site-specific characteristics such as vegetation cover, previous land use, and restoration management being implemented. Therefore, the application of default EFs to a specific land cover could under- or over-estimate the carbon benefit, mainly if applied to a specific tropical PSF cover at the national and project levels. To assess this situation, we conducted a study with the intent of contributing to the restoration of tropical PSFs, particularly by providing site-specific GHG EFs for undrained and rewetted sites in tropical PSFs in Central Kalimantan Province, Indonesia. Both sites had been selectively logged prior being restored. The restoration was started in 2016. The study was divided into three phases: the first was a systematic review and meta-analysis of peer-reviewed literature and data, the second was an assessment of the study sites’ biophysical characteristics and carbon stocks, the third evaluated the variability of GHG EFs in the study sites. In the first phase (Chapter two), a review and meta-analysis were conducted to evaluate the effect of rewetting on carbon emissions by comparing the carbon emissions (CO2, CH4, and Dissolved Organic Carbon [DOC]) from rewetted peatlands (treatment sites) with drained peatlands (control sites) in various climatic zones and at different restoration times. Twenty-seven articles passed the inclusion criteria and were used for meta-analysis. Three of these articles were from tropical climates while the remainder were from boreal and, predominantly, temperate climates. The overall effect size indicates that peatland rewetting can reduce the CO2 emission rate by -1.343 ± 0.358 Mg CO2-C ha-1 yr-1, while significantly increasing the CH4 emission rate by 0.033 ± 0.003 Mg CH4-C ha-1 yr-1. However, there was no discernible effect of rewetting on DOC. The findings highlight the lack of primary data from rewetted tropical peatlands which indicates an opportunity to conduct more research on carbon emissions. In the second phase (Chapter three), biophysical characteristics, carbon stock, and fluxes of the study sites were assessed. The biophysical characteristics of both sites were not significantly different, except for the C/N ratio. The number of species per ha and basal areal in the undrained site were 78, and 23.2  3.1m2/ha While in the rewetted
Keyword: Carbon benefit, greenhouse gas, emission factors, meta-analysis, peatland restoration, heterotrophic respiration