Novel techniques are required to address concerns regarding the long-term sustainability of harvesting practices in order to support increasing demand with decreasing harvests. The sustainability of harvesting northeastern United States forests for wood products and biofuels is essential for ecological and economic capacity across the region. Here, we are proposing to address the knowledge gap of nutrient cycling and primary mineral weathering required to assess immediate and long-term timber harvesting impacts using traditional forest field measurements with novel stable isotope and weathering assessments across a network of existing forest research sites.Goal 1,quantify aboveground biomass and flux rates in forest stands across harvesting severities to measure differences in total ecosystem inorganic nutrients, which allowsfor measuring decreases in productivity with different timber harvests due to losses of inorganic nutrients over iterative harvests.Goal 2,use stable isotopes and microscale geochemical investigations to identify the sources of Ca, Mg, and K within forests and determine the balance between decomposing plant nutrients and mineral dissolution sourced nutrients. In addition, utilize novel in-situ field measurements of vascular fluids and mineral weathering. This information will be used in the process-based model estimate nutrient budgets for several harvests over the next two hundred years.Goal 3, conduct field scale experiment for nutrient additions of wood ash and waste incineration ash. This will allow for determination of potential management strategies to ameliorate the impacts of base cation depletion on forest productivity.Goal 4, Use empirical data from Goals 1 - 3 to parameterize ForNBM, a process-based model, to estimates nutrient inputs, losses, cycling rates, and exports with different timber harvesting intensities and their impacts on biomass and merchantable wood.