Tropical peat forests in Southeast Asia contain vast stores of organic carbon and many of these areas are now rapidly emitting this carbon as they are logged and converted to agriculture. Peat accumulates where the water table is near the surface because saturated conditions maintain anoxia, limiting decay of the peat. Thick peat deposits have likely accumulated over thousands of years because of a positive feedback -- accumulating peat restricts drainage, lifting the water table so more peat can accumulate. Beyond this basic understanding, very little is known about the dynamics of tropical peat forests. What is the sensitivity of tropical peatland coupled H2O/CO2 dynamics to changes in climate? How does peat accumulation or loss depend on seasonality of rainfall? How does peat accumulation depend on nutrient conditions, such as phosphate concentrations? What role, if any, does methane production and consumption play in peat formation or loss? How do lags, legacies, and recovery dynamics of past land use impacts current ecosystem dynamics? What can be done to restore degraded peat lands? To answer these questions, the project is establishing a research site that encompasses two adjacent peat domes, a pristine forested dome and a deforested dome, both on the island of Borneo, in Brunei. All indications are that, prior to deforestation, the ecology of these neighboring domes was indistinguishable. At this site, they will bring together accurate measurements of carbon fluxes over nested time-scales (daily to seasonal to interannual) with analysis of the biogeochemical mechanisms that control peat oxidation and decay. It is hypothesized that most of the fluctuation in net carbon flux from these domes can be predicted from hydrological dynamics, and that the period of maximum carbon uptake (or minimum carbon loss in the deforested site) occurs in the first-stage of dry season when primary productivity increases from higher inputs of photosynthetically active radiation (PAR) and heterotrophic respiration rates remain low because of high water tables. They will also combine near-continuous eddy-flux measurements of CH4 with chamber and dissolved CH4 measurements to create a unique and comprehensive assessment of methane emissions and dynamics.
Most tropical peat is found in Southeast Asia and land-use changes are altering hydrologic systems there, breaking the feedback that has caused peat to accumulate. In recent years, peatland degradation and oxidation has been estimated to account for emissions of 0.30 Pg C yr-1 (averaged over 1997-2006), about a quarter of the global CO2 emissions from deforestation and forest degradation. This research, combining data collection and model development, will provide the tools necessary for understanding historical shifts in tropical peat stores, advancing our understanding of the role that tropical peat forests have played in the carbon cycle over geologic history. These tools will also be valuable for managing existing tropical peat lands. The comparison between an undisturbed site and a deforested site will enable us to construct models appropriate to consider the effects of deforestation and development of tropical peat lands, as well as restoration of degraded peatlands. Data collection is enabled in part by on-site support from the Brunei Forestry Department and environmental sensor development activities at the Center for Environmental Sensing and Modeling (CENSAM) based in Singapore and funded by the Science Foundation of Singapore. The project agreement between SMART (an MIT/Singapore collaboration) and the Brunei Forestry Department includes training workshops related to carbon flux measurement and carbon inventories so the methods and knowledge generated through this project can reach local academics, the government, and the broader Bruneian community. A PhD student is to be supported through the MIT-SMART program.
