Soil carbon dioxide efflux is a natural process by which soil carbon is released into the atmosphere through plant and microbial respiration. While this flux represents the largest natural respiratory flux from forested ecosystems, the effects of soil temperature, soil water content, soil nutrient status, and vegetation cover on soil carbon dioxide efflux remain poorly understood. This dissertation research seeks to identify the relationship between these biophysical controls and the resultant carbon dioxide efflux across the soil-atmosphere interface in a subalpine catchment of the northern Rocky Mountains. This study incorporates knowledge gained through field observations (two growing seasons) into a process-based modeling approach to estimate point-to-catchment scale soil carbon dioxide efflux. Field knowledge will be used to aid in modeling parameterization and calibration. This model will be useful for corroboration and integration of soil and canopy level carbon fluxes. The synergistic nature of this exercise will provide bidirectional feedback, as the model will benefit from field knowledge, and empirical data can be further explored according to modeling results. This study addresses two outstanding eco-hydrological, carbon cycle research questions: the role of hydrology as a spatial and temporal control of soil carbon dioxide efflux, and the effects of yearly hydrological variability in regulating ecosystem carbon balance. The broader impacts of this research include involvement of undergraduate assistants and scholars, incorporation of data from this research into field trip materials and homework problems of undergraduate watershed science classes, and exposure of minority students (Hispanic) to research.
