Dissertation Research: Carbon Sequestration in a Subalpine Forest and Its Control by Winter and Summer Precipitation Dynamics

本研究的重点是了解两个重要的地球化学循环之间的耦合：碳循环和水循环。 在亚高山森林生态系统中，它被假设为美国西部的一个主要碳汇，树木的生长和土壤微生物的活动在很大程度上取决于水分的供应情况。 该项目旨在了解不同的降水类型（冬季降雪与夏季降雨）如何影响该生态系统的碳吸收。 通过分析最近固定的糖的碳同位素比率，树木水分利用效率（WUE）的测量将计算全年。 然后，将开发一个模型，从WUE和蒸腾量的测量计算碳同化。 利用氢、氧同位素示踪树木利用水源，并将主要水源与森林碳吸收量联系起来，研究降水类型对森林碳吸收的影响。

The focus of this research is to understand the coupling between two important biogeochemical cycles: the carbon and water cycle. In the subalpine forest ecosystem, which has been hypothesized as a major carbon sink in the Western U.S., tree growth and soil microorganism activity are highly controlled by the availability of moisture. This project aims to understand how different precipitation types (winter snow versus summer rains) affect carbon uptake in this ecosystem. By analyzing the carbon isotope ratio of recently fixed sugars, measurements of tree water use efficiency (WUE) will be calculated throughout the year. A model will then be developed to calculate carbon assimilation from measurements of WUE and transpiration. Oxygen and hydrogen isotopes will be used to trace water sources used by trees, and the dominant water source will be related to forest carbon gain in order to investigate the influences of precipitation type on forest carbon uptake.