The U.S. has been a strong carbon sink over the last several decades, largely due to regrowing forests. However, the carbon sink measured today does not account for carbon lost from previous disturbances. The Terrestrial Ecosystems Model Hydro version (TEM-Hydro) has been developed to include both human and natural disturbances. Human disturbances are based on a land use transition dataset and include agricultural (crops and pasture) conversion and abandonment and timber harvest. Natural disturbances include tropical storms, hurricanes and fires based on stochastic return intervals. Model results show that, to the first order, human changes in land use have determined the magnitude of the carbon sink, modified by natural disturbances, whereas climate is often responsible for year-to-year variability. Fertilized croplands and forests are the largest sinks, seconded by pastures, if not accounting for decomposition of agricultural products and livestock respiration. While the positive Net Ecosystem Productivity (NEP) measured today is the result of past land use disturbance, net carbon sequestration (NCE), including product decomposition, conversion fluxes, and livestock respiration, has not yet returned to predisturbance levels. Differences in response to disturbance have to do with the type, frequency, and intensity of disturbance, which affects the decomposition of coarse woody debris and soil nutrient levels. A full carbon accounting should be considered when determining the effects of forest regrowth on the terrestrial carbon sink

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