A New Method of Assessing Forest Change at the County Level in the Southeastern US

Frank Perchalski (Presenter), Department of Biology, University of the South

Jonathan P. Evans, Department of Biology, University of the South

Aerial data resources, residing in many county USDA offices, have been used since the mid-1980's, for a number of interesting applications beyond their intended program uses.  These have included land cover mapping, nonpoint source inventories, and environmental assessments. In the summer of 1999, the same aerial data was used to document landscape changes on the Cumberland Plateau in Grundy County, Tennessee.  A prototype, annual, one hundred percent, forest landscape change database was produced by manual examination of eighteen years of Farm Service Agency (FSA) compliance program small format aerial photographs.  Landscape changes greater than fifty acres were recorded.

This past summer, the process evolved from its initial manual method to a digital approach.  This involved combining the strengths of three types of aerial imagery: digital orthophoto quarter quadrangles (DOQQs), National Aerial Photography Program (NAPP) airphotos, and small format aerial photographs (SFAPs).  The georeference tie for all other aerial data were Natural Resources Conservation Service (NRCS) DOQQs, now available over most agricultural counties.  The baseline land cover tie was created by stereoscopic analysis of the same NAPP coverage used to create the DOQQs. Annotations resulting from the NAPP analyses were captured through heads-up digitizing of scanned contact prints, with their attached annotated overlays, which were warped to fit the corresponding DOQQs.  The final step was to scan the SFAP slides, warp them to the DOQQs, and digitize landscape changes of greater than twenty-five acres.

The result of this process was an historical record of landscape changes from the mid-1980s to the present, with a framework to keep the database as current as the latest annual FSA compliance aerial data.   The methodology is effective and transferable.  It is now ready for use in documenting changes on the remainder of the Cumberland Plateau and other forested areas with good FSA and NRCS airphoto coverages.

Workshop II: Monitoring Forest Changes

Sustaining
Southern
Forests

a conference sponsored by the Southern Forest Resource Assessment