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蕴藏着大量的有机碳，其中许多地区在砍伐森林并将其转化为农业后，正在迅速排放这种碳。泥炭在地下水位接近地表的地方堆积，因为饱和条件保持缺氧，限制了泥炭的腐烂。厚厚的泥炭沉积可能已经积累了数千年，因为有一个正反馈--积累的泥炭限制了排水，抬高了地下水位，因此可以积累更多的泥炭。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H2O/CO2耦合动力学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？甲烷的生产和消费在泥炭的形成或损失中起到了什么作用？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？怎样才能恢复退化的泥炭地呢？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，一个原始的森林圆顶和一个被砍伐的圆顶，两者都在文莱的婆罗洲岛上。所有迹象都表明，在砍伐森林之前，这些邻近圆顶的生态是难以区分的。在这个地点，他们将结合对嵌套时间尺度(从每日到季节性再到年际)碳通量的准确测量，并分析控制泥炭氧化和腐烂的生物地球化学机制。假设这些穹顶的净碳通量的大部分波动可以从水文动力学中预测出来，最大的碳吸收时期(或砍伐地点的最小碳损失)发生在旱季的第一阶段，此时初级生产力因光合作用有效辐射(PAR)的较高输入而增加，而异养呼吸速率由于高地下水位而保持较低的水平。他们还将结合对甲烷的近乎连续的涡流通量测量，以及室内和溶解甲烷的测量，创建对甲烷排放和动态的独特和全面的评估。大多数热带泥炭发现在东南亚，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，泥炭地退化和氧化的排放量估计为0.30PgCyr-1(1997-2006年平均)，约占全球毁林和森林退化二氧化碳排放量的四分之一。这项研究结合了数据收集和模型开发，将为理解热带泥炭储存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的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。比较未受干扰的地点和砍伐森林的地点将使我们能够构建适当的模型，以考虑森林砍伐和热带泥炭地的开发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，以及设在新加坡、由新加坡科学基金会资助的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/新加坡合作)和文莱林业部之间的项目协议包括与碳通量测量和碳清单相关的培训讲习班，以便通过该项目产生的方法和知识可以接触到当地学者、政府和更广泛的文莱社区。一名博士生将通过MIT-SMART计划得到支持。

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.