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A vulnerability assessment is one tool that land managers can use to inform rangeland management decisions. As part of a distributed vulnerability assessment of the impact of climate change on sagebrush steppe ecosystems we evaluated the impact of climate change on carbon cycling in mature sagebrush ecosystems. We used ecosystem carbon values from the SageSTEP (http://www.sagestep.org/) project to parameterize the DayCent (http://www.nrel.colostate.edu/projects/daycent/) model simulations of carbon fluxes. We used projected values of daily weather from a full suite of climate change models (http://gdo-dcp.ucllnl.org/downscaled_cmip_projections/) to simulate a range of climate change scenarios. We also evaluated the effect of fire on ecosystem carbon through a state change from a mature sagebrush ecosystem to an annual grass dominated ecosystem. We found that sagebrush ecosystems continued to provide carbon storage in most of the years modeled, indicated by a positive net annual ecosystem carbon balance, and there was little difference in storage potential associated with different climate change scenarios. We found that the amount of carbon stored varied by site and by initial input values. There are two major implications for land management. First, that carbon storage potential is site specific. Second, that disturbance, such as fire and agricultural or urban development, are likely to have greater impact on the carbon-storage potential of sagebrush ecosystems than climate change alone.