Climate, fire (frequency and intensity), and forest structure and development are strongly linked, but our knowledge of the interactions of these factors is poor. We lack the ability to make robust predictions about how changes in climate will alter these interactions and change the carbon balance of a landscape. Our objective is to estimate how changes in fire frequency, pattern, and intensity will alter the distribution of forest age and structure across a landscape and how these changes, in turn, will change the landscape carbon balance. We will determine the current carbon balance for the Yellowstone National Park (YNP) landscape and how much carbon was lost in the 1988 fires by (a) mapping the current distribution of forest age and tree density for the YNP landscape, (b) measuring how annual net carbon storage (NEP) varies with forest age and tree density using replicated chronosequences, (c) estimating how much carbon was removed from the landscape by the 1988 fires through direct combustion, and (d) extrapolating stocks and fluxes to the landscape using the detailed maps and measurements. We will then determine how NEP will change for the YNP landscape with changes in climate and fire regimes (a) by calibrating the Century biogeochemical model to assess how changes in climate will alter NEP across stand development, (b) using models developed in past research to simulate fire frequency, fire spread, and the resulting landscape structure (the distribution of stand age and tree density) for alternative climatic conditions, and (c) by combining (a) and (b) to estimate landscape NEP for different climates and the different fire regimes they cause. The lodgepole pine ecosystems of YNP are ideal for this research because the landscape mosaic is complex (high variability in tree density and stand age), the structure within a patch is simple (generally one species with even-aged cohorts of trees), and, because soils and climate are similar across the plateau, information from replicated plot studies can be extrapolated to the landscape. We hypothesize that variation in tree establishment after a fire and the legacy of the prior stand will control the trajectory of NEP through time, and that climate and fire frequency will change the distribution of forest age and structure, and these changes will alter net carbon storage for the landscape. This research will significantly improve our knowledge of how NEP changes with stand development after a fire, and how climate-induced changes in the disturbance regime will affect landscape age and stand structure and NEP for the landscape. Because we will examine the entire C budget we will also tightly link fuels (litter, CWD, foliage, etc.) with overstory characteristics on a landscape scale.