Dissertation Research: Effects of Oxic-Anoxic Dynamics on Methanogenesis and Methane Oxidation in Humid Tropical Forests-Evidence from Stable Isotope Distributions

在潮湿的热带森林土壤中甲烷的动力学和稳定同位素地球化学知之甚少，损害了我们预测甲烷通量和13 C与大气交换速率的能力。如果我们希望评估热带地区在全球甲烷收支中的作用，那么量化甲烷通量的源/汇强度和 * 13 C特征至关重要。在氧化还原波动的系统中，例如潮湿的热带森林土壤，氧气的变化通过改变甲烷生成和甲烷氧化之间的平衡来影响甲烷排放。本研究探讨了氧气变化对甲烷生成、甲烷氧化和13 C与大气交换的影响。甲烷通量和13 C交换的模式将在野外的自然氧气梯度中记录下来。将通过气体浓度和稳定同位素分析，在土壤和整个景观中确定甲烷的源和汇。将进行一系列的机理实验，以探讨氧气变化对总甲烷生成，甲烷氧化和稳定同位素分馏的影响。这项研究将推进我们对调节甲烷和13 C从潮湿热带森林到大气的通量的因素的认识。

The dynamics and the stable isotope geochemistry of methane in wet, tropical forest soils are poorly understood, compromising our ability to predict rates of methane flux and 13 C exchange with the atmosphere. Quantifying the source/sink strength and * 13 C signature of methane flux is crucial if we hope to evaluate the role of the tropics in the global methane budget. In systems where redox fluctuates, such as wet tropical forest soils, variations in oxygen influence methane emissions by altering the balance between methanogenesis and methane oxidation. This study explores the effects of oxygen variations on methanogenesis, methane oxidation and 13 C exchange with the atmosphere. Patterns of methane flux and 13 C exchange will be documented across natural gradients of oxygen in the field. Sources and sinks of methane will be identified, both in soil and across the landscape, through gas concentrations and stable isotope analysis. A series of mechanistic laboratory experiments will be performed to explore the effects of oxygen variation on gross methanogenesis, methane oxidation and stable isotope fractionation. This study will advance our knowledge of the factors that regulate methane and 13 C flux from wet tropical forests to the atmosphere.