I will describe some of the observational approaches we have deployed to measure the net rate of carbon dioxide exchange between a forest ecosystem and the atmosphere. The observed net exchange of CO₂ represents the sum of several components of gross CO₂ exchange, which in turn represent fundamental tree and soil metabolic processes. One challenge we have had is: how do we extract insight about how these component processes might be responding to environmental change at various scales from an observed time series? I will discuss some of our experiences with statistical- and process-based models as we apply them to our several-year record of forest CO₂ exchange, and use these applications to extract insight about ecosystem processes. I will briefly describe how one such approach – model-data assimilation and posterior parameter estimation – might be applied to a time series extracted from the tree ring record, and used to inform us about the integration of both phenotypic and environmental influences on tree ring structure and isotopic composition.