Downed and dead woody material (DWM) is created when trees fall or shed branches, and DWM is a substantial pool of carbon. The removal of DWM during harvests has raised questions about how long it would normally reside in forests. If DWM is determined to be a long-term store of carbon, then its conservation during harvests might be considered "carbon friendly." Forest Service scientists developed a technique for matching measured DWM pieces over short periods of time. Instead of waiting for DWM to decay (possibly a 100-year wait), a model was created to predict the probability of DWM moving from one stage of decay to the next. The decay model was applied to a DWM inventory across the eastern United States to estimate the residence time of DWM. For hardwood species, especially small DWM in warm andhumid climates, over half of the DWM biomass is lost to the atmosphere or other carbon pools within 10 years. For coniferous DWM in cold anddry climates, it may take over 100 years for carbon to be emitted or transferred to other pools. So, if a tree falls in a forest, how long does it lie there In eastern U.S. forests, the answer is between 30-100 years.