Collaborative Research: Modeling and Measuring the Spatio-Temporal Variability of Methane Emissions from Tropical Dambo Wetlands

从分子的角度来看，甲烷（CH 4）作为温室气体的有效性在100年的时间尺度上是二氧化碳（CO2）的30倍。天然湿地是全球甲烷排放的最大单一来源，也是直接应对气候变化的唯一来源。尽管甲烷的重要性，很大的不确定性围绕着天然湿地的全球甲烷排放量的估计。由于缺乏地面观测、详细的地图和大多数发展中国家的数据，热带湿地（占湿地排放的大部分）的不确定性特别大。Dambos（季节性饱和，无渠道的谷底）是中非和南部非洲最大的季节性湿地，占中非高原的20%，总面积超过200，000平方公里。本项目的目标是构建一个空间和时间上明确的估计，从2500平方公里的代表性dambos在北方卢韦罗区，乌干达的甲烷排放量。研究人员将使用多光谱（ASTER）遥感与数字地形建模相结合，对景观进行分层，区分丹波湿地和高地地区，以及丹波内的土壤和水文变化。将选择有代表性的地点，详细描述土壤和植被的特性，监测水文和温度，并测量甲烷通量。项目小组将监测一个主要雨季的甲烷通量和一年半或三个雨季的水文情况。利用这些数据，他们将确定对dambo甲烷通量的关键控制，并构建一个经验模型，将这些通量与土壤特性，植被，温度和水文学联系起来。该项目将首次严格量化dambo的甲烷排放量，为整个中部和南部非洲热带dambo湿地的年度和季节甲烷排放量的一阶估计提供基础。这些数据将有助于限制高度不确定的热带来源估计全球大气甲烷模型。采用的建模策略“连接剖面尺度甲烷模型的动态景观湿地模型”支持热带丹波湿地对未来气候变化情景的响应预测，使科学家能够评估积极或消极的气候变化反馈的潜力。该项目支助的两名研究生将接受从遥感和地形建模到湿地甲烷排放的地球化学等领域的培训。他们还将在该领域与美国-他是一位来自乌干达的合作者和一位来自巴基斯坦的研究者，他将亲自学习热带土壤、水文、植被和景观，以及如何在发展中国家开展研究。相反，一名年轻的乌干达科学家将有机会与美国科学家一起研究一个对当地和全球都具有重要意义的项目。为了提高人们对丹波的普遍认识，除了正常的科学出版物外，研究人员还将指导一名本科生研究人员建立一个丹波网站，其中包括遥感图像、实地照片、地图、统计数据、参考书目和灰色文献。

Molecule for molecule, methane (CH4) is about 30 times more effective as a greenhouse gas than carbon dioxide (CO2) on a 100-year time scale. Natural wetlands are the largest single source of global methane emissions and are the only source that responds directly to climate change. Despite the methane's significance, large uncertainties surround estimates of global CH4 emissions from natural wetlands. Uncertainties are particularly large for tropical wetlands (accounting for the majority of wetland emissions) due to the paucity of ground observations, detailed maps, and data for most of the developing world. Dambos (seasonally saturated, channelless valley floors) constitute the largest geographic extent of seasonal wetlands in Central and Southern Africa, occupying up to 20 percent of the central African plateau with more than 200,000 km2 of total extent. The objective of this project is to construct a spatially and temporally explicit estimate of methane emissions from 2500 km2 of representative dambos in the northern Luwero District, Uganda. The investigators will use multispectral (ASTER) remote sensing combined with digital terrain modeling to stratify the landscape, distinguishing dambo wetlands from upland regions as well as soil and hydrologic variability within dambos. Representative sites will be selected for detailed soil and vegetation characterization, hydrologic and temperature monitoring, and the measurement of methane fluxes. The project team will monitor methane fluxes through one major wet season and hydrology over one and a half years or three wet seasons. Using this data, they will identify key controls on dambo methane fluxes, and construct an empirical model relating these fluxes to soil properties, vegetation, temperature, and hydrology.This project will provide the first rigorous quantification of methane emissions from dambos, providing the basis for a first-order estimate of methane emissions over annual and seasonal for tropical dambo wetlands throughout Central and Southern Africa. Theses data will help constrain highly uncertain tropical source estimates for global atmospheric methane models. The modeling strategy employed "linking a profile-scale methane model to a dynamic landscape wetland model" supports predictions of the response of tropical dambo wetlands to future climate change scenarios, allowing scientists to assess the potential for positive or negative climate change feedbacks. The two graduate students supported on this project will be trained in fields ranging from remote sensing and terrain modeling to the biogeochemistry of wetland CH4 emissions. They will also work closely in the field with both a U.S.-based investigator and a Ugandan collaborator, learning first hand about tropical soils, hydrology, vegetation, and landscapes as well as how to conduct research in a developing country. Conversely, a young Ugandan scientist will have the opportunity to work with U.S. scientists on a project of both local and global importance. To raise general awareness of dambos, in addition to normal scientific publication the investigators will direct an undergraduate researcher to construct a dambo website with remotely sensed images, photos from the field, maps, statistics, a bibliography, and grey literature.