Average tree diameter (dbh) is also an important forest condition for some species requiring large trees and subsequent tree cavities for denning/nesting/roosting sites. The GCPO LCC ISA targets diameter of upland hardwood forest and woodland trees to be ≥14” dbh. The standardized Forest Inventory and Analysis (FIA) national program, which collects data using standardized field protocols across counties in every state annually, may be the only landscape-scale data source feasible to investigate average tree diameter in the absence of other large-scale data sources in the GCPO geography. We used FIA-imputed data on average tree diameter (DBH, inches) (USDA Forest Service Remote Sensing Applications Center [USFS], personal communication) extracted through the upland hardwoods mask as a proxy for assessment of DBH within the Ozark Highlands and other GCPO geographies. The USFS imputed average DBH product provides raster maps for the conterminous U.S. generated using 250 m resolution MODIS satellite imagery, ancillary environmental data, and 2000-2009 plot-level field data from the FIA program. We used an extract by mask function in ArcGIS to delineate average DBH in upland hardwoods, using the USFS imputed DBH layer as input data and the upland hardwoods woodland and forest layers described above as mask overlays. We then reclassified to extract woodlands and forest ≥14” DBH. There was very limited presence of average DBH ≥14” in upland hardwood systems in the GCPO geography. We therefore binned the data into quantiles and used the upper quantile of DBH values for woodlands (≥6.10” DBH) and forests (≥6.26” DBH) as a proxy to examine areas in the GCPO upland hardwoods that exhibited the “largest” trees on average. We summarized the data spatially as a binary reclassification of the top quantile (0,1), by summing acres within each GCPO subgeography, and by calculating the proportional area of a HUC12 watershed falling into the top DBH quantile for woodlands and forest.
