Effects of Disturbance, Climate, and Management on U.S. Forest Carbon
Forest Service scientists combined an advanced ecosystem process model with data from Forest Inventory and Analysis and remote sensing to separate the effects of disturbance factors (harvesting, fire, and insects) from nondisturbance factors (climate variability, carbon dioxide fertilization, and nitrogen deposition). Results showed that disturbance factors had the strongest effects overall, but with significant regional and temporal differences. This is the first instance where separation of causes has been possible at the continental scale, and this new information can be used to support development of policies and approaches to improve sustainable forest management and provide for cleaner air and water.
Recent climate variability (increasing temperature and droughts) and atmospheric composition changes (nitrogen deposition, rising carbon dioxide concentration) along with harvesting, wildfires, and insect infestations, have had significant effects on U.S. forest carbon uptake. The carbon changes in forests of the conterminous United States can be attributed to disturbance and nondisturbance factors. Factors were grouped into disturbances (harvesting, fire, insect infestation) and nondisturbances (carbon dioxide concentration, nitrogen deposition, and climate variability) and their subsequent effects on forest regrowth patterns were estimated.
Results showed that, on average, the carbon sink in the conterminous U.S. forests from 1950 to 2010 was 87 percent of the sink in living biomass. Compared with the simulation of all factors combined, disturbance factors alone (including forest regrowth after disturbances) may contribute 46 percent of the sink, while nondisturbance factors alone contribute about 24 percent of the sink.
The study also showed diverse regional patterns of carbon sinks are related to the importance of driving factors. From 1980 through 2010, disturbance effects that dominated the carbon changes in the South and Rocky Mountain regions were nearly equal to nondisturbance effects in the North, and had minor effects compared with nondisturbance effects in the west coast region.
Forest Service Partners