Doctoral Dissertation Research: Biomass Burning, Land-Cover Change, and Atmospheric Emissions. A Comparative Study of the Guinean and Sudanian Savannas of Cote d'Ivoire

在西非的农牧系统中，火是一种重要的管理工具。环境科学家和政策制定者认为生物质燃烧是温室气体和一氧化二氮、甲烷和二氧化碳等气溶胶的重要来源。非洲在全球火灾事件的地理分布上占主导地位，约占所有火灾的40%，据信非洲大陆占全球生物质燃烧排放总量的30%。然而，最近土地利用和土地覆盖的变化与棉花、树木作物的扩大和牲畜饲养有关，导致了燃烧制度的变化。燃烧规律是指火灾发生的时间、强度和频率。最显著的变化是燃烧的时间，因为牧民在旱季会更早地生火。由于植物和土壤的高湿度，这些早期的火灾不那么强烈。早期的火灾对植被的破坏性不那么大，这会导致更多的树木出现在景观中。不那么强烈的火灾也产生更少的气体和气溶胶排放到大气中。本博士论文研究项目将在科特迪瓦当地和区域尺度的社会、经济、政治和生物物理过程中研究生物质燃烧对全球气候变化的影响。该博士候选人将研究热带稀树草原燃烧机制的趋势，分析1975年至2008年期间土地覆盖变化的性质和方向，并评估科特迪瓦热带稀树草原生态系统对全球温室气体产生的贡献。将使用实地研究技术和遥感方法来解决本研究中提出的问题。将对农民和牧民进行调查和访谈，以征求他们对焚烧做法变化的看法，并了解他们在特定时间和地点纵火的观点和原因。植被样带和对四年（1975年、1985年、1995年和2007年）卫星图像的分析将揭示植被覆盖的趋势和燃烧的时空分布。生物质燃烧实验将在整个燃烧季节进行，以估计一氧化碳、二氧化碳、甲烷、氮氧化物和臭氧的数量。这项研究将对全球气候变化的科学文献作出贡献，为地方和区域尺度上主要温室气体的产生提供更准确的评估。研究人员将在评估科特迪瓦与生物质燃烧有关的温室气体排放时考虑燃烧制度和不同的稀树草原景观。这些数据将对燃烧的生物质和排放的气体的种类和数量作出新的估计。这些知识将有助于计算全球气候变化模式中常用的新系数。通过从局部尺度扩大到区域尺度，本研究将有助于填补当前全球气候变化研究的一个重要空白。这项研究将有助于在稀树草原生态系统动力学尚未得到很好理解的情况下进行火灾政策辩论，特别是火灾对植被和温室气体排放的影响。这项研究的结果将产生科特迪瓦迫切需要的温室气体和气溶胶排放数据，这些数据可用于为科特迪瓦的环境政策提供信息。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。该奖项由美国国家科学基金会国际科学与工程办公室联合资助。

Fire is an important management tool in the farming and pastoral systems of western Africa. Environmental scientists and policymakers consider biomass burning to be an important source of greenhouse gases and aerosols like nitrous oxide, methane, and carbon dioxide. Africa dominates the geographical distribution of fire events globally, accounting for about 40 percent of all fires, and the continent is believed to account for 30 percent of all biomass burning emissions worldwide. Recent changes in land use and land cover related to the expansion of cotton, tree crops, and livestock rising have led to changes in burning regimes, however. A burning regime refers to the timing, intensity, and frequency of fires. The most notable change is in the timing of burning, as fires are set earlier in the dry season by herders. These early fires are less intense due to high moisture levels in plants and soils. Early fires are not as destructive to vegetation, which results in more trees in the landscape. Less intense fires also produce fewer gas and aerosol emissions into the atmosphere. This doctoral dissertation research project will investigate the impacts of biomass burning on global climate change in the light of social, economic, political, and biophysical processes at the local and regional scales in Cote d'Ivoire. The doctoral candidate will examine trends in savanna burning regimes, analyze the nature and direction of land cover change over the period 1975 to 2008, and assess the Ivorian savanna ecosystems contribution to the global greenhouse gas production. Field research techniques and remote sensing methods will be used to address the questions raised in this study. Surveys and interviews with farmers and herders will be conducted to solicit their perceptions of any changes in burning practices and to gain their perspectives and reasons for setting fires at certain times and places. Vegetation transects and the analysis of satellite images for four years (1975, 1985, 1995, and 2007) will reveal trends in vegetation cover and the spatial and temporal distribution of burning. Biomass burning experiments will be conducted throughout the burning season to estimate the amount of carbon monoxide, carbon dioxide, methane, nitrogen oxides and ozone.This study will contribute to the scientific literature on global climate change by providing a more accurate assessment of the production of key greenhouse gases at the local and regional scales. The investigators will consider burning regimes and differentiated savanna landscapes in the evaluation of greenhouse gas emissions associated with biomass burning in Cote d'Ivoire. The data will furnish new estimates of the type and amount of biomass burned and gases emitted. This knowledge will result in the calculation of new coefficients that are commonly used in global climate change models. By scaling up from the local to the regional scale, this research should help fill an important gap in current global climate change research. This research will contribute to the fire policy debates in which savanna ecosystems dynamics are not well understood, especially the impacts of fire on vegetation and greenhouse gas emissions. The study's results will yield badly needed data on greenhouse gas and aerosol emissions in Cote d'Ivoire that can be used to inform Ivorian environmental policies. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career. This award is jointly funded by NSF's Office of International Science and Engineering.