Implementation of the North American Forest Dynamics (NAFD) Project: Current Progress and Future Plans

Through the North American Forest Dynamics (NAFD) project we are evaluating forest disturbance and regrowth patterns by combining U.S. Forest Service Forest Inventory and Analysis (FIA) field observations with biennial time series Landsat imagery. Phase I of the NAFD study examined forest dynamics and disturbance history from Landsat time series stacks (LTSS) for 23 sample locations within the United States. These samples were selected with known inclusion probability to allow derivation of unbiased national estimates of disturbance rates with known uncertainty boundaries. FIA field plot data were used to validate the changes mapped in the Landsat data by the vegetation change tracker (VCT) algorithm. Additional accuracy assessment was performed on selected sample LTSS using visual analysis of the time series compared with high resolution imagery. Results of NAFD disturbance mapping to date reveal generally high rates of forest disturbance across the U.S., with these rates varying both spatially and temporally. Ongoing work for the Phase II NAFD study expands on this initial work, in several ways, to meet NACP goals. We are adding additional sample locations in the conterminous U.S. to reduce error in nationwide estimates of disturbance. We are also now partnering with Canada and Mexico to improve our understanding of continent- wide forest dynamics. The NAFD study has also developed collaborative relationships with other NACP- funded scientists who are using our analyses to inform their carbon assessment. In addition, we are currently developing nationwide maps of disturbance rates from model-based estimators combined with the sample site locations to better meet the needs of carbon modelers. The NAFD project is also extending forest dynamics analyses by examining regrowth patterns. We are doing so by converting Landsat data stacks to biomass to better characterize the carbon significance of forest disturbance and regrowth. We are also employing radiative transfer modeling as a means to validate relationships between the FIA and Landsat measurements by employing the FIA field data to parameterize the RT model and compare with the actual Landsat observations.