TOWARDS A BETTTER UNDERSTANDING OF FOREST CHANGE PROCESSES IN THE CONTIGUOUS U.S.
Goward, Samuel N.
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Estimates of forest canopy areal extent, configuration and change have been developed from satellite based imagery and ground based inventories to improve understanding of forest dynamics and how they interact with other earth systems across many scales. The number of these types of studies has grown in recent years. Yet, few have assessed the multiple change processes underlying observed forest canopy dynamics across large spatio-temporal extents. To support these types of assessments, a more detailed and integrated understanding of the geographic patterns of the multiple forest change processes across the contiguous US (CONUS) is needed. This study examined a novel data set from the North American Forest dynamics (NAFD) project that provides a dense temporal record (1984-2005) of forest canopy history across the U.S., United States Forest Service (USFS) ground inventory data, and ancillary geospatial data sets on forest change processes (wind, insect, fire, harvest and conversion to suburban/urban land uses) across the CONUS to develop a more robust understanding of the implications of the shifting dynamics of forest change processes and our ability to measure their effect on forest canopy dynamics. A geodatabase of forest change processes was created to support synoptic and specific quantitative analysis of change processes support through space and time. Using the geodatabase, patterns of forest canopy losses from NAFD and USFS data and the underlying causal process were analyzed across multiple scales. This research has shown that the overlap of multiple disturbance processes leads to complex patterns across the nation's forested landscape that can only be fully understood in relation to forest canopy losses at fine scales. Regional statistics confounded the direction and magnitude of forest canopy loss from multiple change processes operating on the landscape. Data gaps and uncertainty associated with process data prevent a full quantitative analysis of the proportion of forest area affected by each forest change process considered here. Fine scale data were critical for interpreting the highly variable NAFD canopy change observations and their ability to capture the continuously changing spatial and temporal characteristics of forest change processes across the CONUS.