Like all plants, forest trees accumulate and store surplus mobile carbon (C) compounds as resources to be used to support future growth (Chapin et al. 1990). This can be viewed as a “bet hedging†strategy, providing reserves that the tree can draw on in times of stress, e.g., following disturbance, disease, or extreme climatic events. In the context of climate change, understanding factors influencing the availability of these stored C compounds to support growth and metabolism is essential for predicting the resilience of forests to environmental stress factors. The objective of our work is to use novel field sampling and analytical methods to quantify the size, availability, and turnover time (i.e., mean age) of the mobile C pool in forest trees throughout the growing season. By incorporating these data into a model of tree C dynamics, we will be able to quantify the capacity (in terms of mobile C reserves) of trees to tolerate biotic and abiotic stress factors. We have recently completed lab work for a study that quantifies the mixing of stored reserves across tree ring boundaries (i.e. mixing of “new†reserves into “old†wood). New work being conducted in 2014 will construct whole-tree budgets of stored reserves, and quantify the seasonal cycles in root, stem and canopy pools, for the dominant tree species at Harvard Forest. We are also starting a project to evaluate the impact of hemlock woolly adelgid (HWA) infestation on stored reserves.