Sink or Source? Fire and the Forest Carbon Cycle

As the size and severity of fires in the western U.S. continue to increase, it has become ever more important to understand carbon dynamics in response to fire. Many subalpine forests experience stand-replacing wildfires, and these fires and subsequent recovery can change the amount of carbon released to the atmosphere because subalpine forests store large amounts of carbon. Stand-replacing fires initially convert ecosystems into a net source of carbon as the forest decomposes—a short-term effect (decades) that will likely be important over the next century if fire frequency increases as a result of climate change. Over the long term (centuries), net carbon storage rebounds throughout the fire cycle if forest stands replace themselves. In a case study of the landscape changes resulting from the 1988 fires in Yellowstone National Park, landscape carbon storage was shown to be resistant in the long term to changes in fire frequency because the most rapid changes in carbon storage occur in the first century, these forests regenerate quickly, and the current fire interval is very long. In subalpine ecosystems with different characteristics, however, the conversion of forest to sparse forest or meadow after fire is possible and could have a large impact on landscape carbon storage