Abstract

Carbon cycling in the terrestrial biosphere, particularly forest ecosystems, has an important role in regulating atmospheric concentrations of carbon dioxide. US West coast forest management policies are being developed to implement forest biofuels energy production while reducing risk of catastrophic wildfire. The impact of partial disturbance (i.e. thinning) on net ecosystem carbon balance (NBP) has not been quantified. Modeling and understanding the response of terrestrial ecosystems to changing environmental conditions associated with energy production and use are primary goals of global change science. Coupled carbon-nitrogen ecosystem process models identify and predict important factors that govern long term changes in terrestrial carbon stores or net ecosystem production (NEP). Through the combined use of forest inventory data and the NCAR CESM /CLM4-CN coupled carbon-climate model, the objectives of this project were to 1) determine the short-term net carbon emissions to the atmosphere of US west coast forests following the implementation of bioenergy management strategies using observed plot data, 2) validate model output using a spatially representative dataset for the region, and 3) predict the net carbon emissions for Oregon forests under future environmental change and multiple rotations of bioenergy harvest. Increased harvest activity for bioenergy was found to result in increased emissions to the atmosphere depending on the baseline conditions of the forest. Future changes in baseline conditions may result in reduced emissions in some forest types. However, better understanding of the causes of reduced forest carbon uptake, the implications on nutrient cycling, and a range of climate scenarios are required to determine the specific consequences of forest management decisions under future environmental change.