Collaborative Research: Water and Carbon Dynamics in Tropical Peat Lands -- Comparison of a Forested Peat Dome with a Deforested Peat Dome in Borneo

东南亚的热带泥炭森林含有大量的有机碳，其中许多地区在被砍伐和转化为农业的过程中，正在迅速排放这种碳。泥炭积聚在地下水位接近地表的地方，因为饱和的条件维持缺氧，限制了泥炭的腐烂。厚厚的泥炭沉积物可能已经积累了数千年，因为一个正反馈——积累的泥炭限制了排水，提高了地下水位，因此更多的泥炭可以积累。除了这一基本认识之外，人们对热带泥炭森林的动态知之甚少。热带泥炭地耦合H2O/CO2动态对气候变化的敏感性是什么？泥炭的积累或损失如何取决于降雨的季节性？泥炭的积累如何取决于营养条件，如磷酸盐浓度？如果有的话，甲烷的生产和消耗在泥炭的形成或损失中起什么作用？过去土地利用的滞后、遗留和恢复动态如何影响当前的生态系统动态？可以做些什么来恢复退化的泥炭地？为了回答这些问题，该项目正在建立一个研究地点，包括两个相邻的泥炭圆顶，一个是原始的森林圆顶，一个是被砍伐的森林圆顶，都在文莱的婆罗洲岛。所有的迹象都表明，在森林砍伐之前，这些邻近圆顶的生态是难以区分的。在这个地点，他们将把对嵌套时间尺度（每日到季节性到年际）的碳通量的精确测量与控制泥炭氧化和腐烂的生物地球化学机制的分析结合起来。据推测，这些穹顶的净碳通量的大部分波动可以通过水文动力学来预测，并且最大碳吸收（或毁林地点的最小碳损失）发生在旱季的第一阶段，此时，较高的光合有效辐射（PAR）投入增加了初级生产力，而异养呼吸速率由于高水位而保持在较低水平。他们还将结合近连续的CH4涡流通量测量与室内和溶解CH4测量，以创建一个独特而全面的甲烷排放和动力学评估。大多数热带泥炭分布在东南亚，土地利用的变化正在改变那里的水文系统，打破了导致泥炭积累的反馈。近年来，泥炭地退化和氧化估计造成每年0.30 Pg C的排放量（1997-2006年平均），约占全球毁林和森林退化造成的二氧化碳排放量的四分之一。这项研究将数据收集和模型开发相结合，将为理解热带泥炭储量的历史变化提供必要的工具，促进我们对热带泥炭森林在地质历史上碳循环中所起作用的理解。这些工具对管理现有的热带泥炭地也很有价值。对未受干扰的地点和被砍伐的地点进行比较，将使我们能够建立适当的模型，以考虑森林砍伐和热带泥炭地的发展以及退化泥炭地的恢复的影响。数据收集部分得益于文莱林业部的现场支持，以及新加坡科学基金会资助的新加坡环境传感与建模中心（CENSAM）的环境传感器开发活动。SMART（麻省理工学院与新加坡合作的项目）与文莱林业部之间的项目协议包括与碳通量测量和碳清单有关的培训讲习班，以便通过该项目产生的方法和知识能够传播给当地学术界、政府和更广泛的文莱社区。博士研究生将通过麻省理工学院smart项目获得支持。

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.