Temporal dynamics of each GCPO priority system are recognized as important contributors to the overall system integrity. The Integrated Science Agenda (ISA) alludes to the desired condition that forest structure should be dominated by mature upland hardwood stands across the greater landscape. However, to ensure future forest sustainability a small portion (≤10% of the landscape) should be in a state of regeneration, or early forest succession. The ISA provides this endpoint as a general target, but lacks specificity regarding the desired composition of forest stand ages because there is limited literature available that assesses upland hardwood stand age from an ecosystem integrity perspective. Priority wildlife species will also respond differentially to forest stand age depending on life history needs of the species. Composition of early-successional forest in the landscape also depend on management regimes on protected lands and land use history in surrounding private lands. However, forest practitioners in the southeast typically practice even-aged management, particularly in long-rotation upland hardwood systems. Therefore, forest regeneration will more frequently be found in a patch mosaic of regenerating clearcuts, with some potential for uneven-aged management regimes in some of the larger protected lands in the Ozark Highlands and West Gulf Coastal Plain. We used plot-level 250 m resolution imputed data from the FIA program to assess forest stand age as a proxy for successional stage distribution in the GCPO (USDA Forest Service Remote Sensing Applications Center, personal communication). The USFS stand age data 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, and calculates stand age on a per-acre-of-land basis, though forested lands were the primary sampling frame. We first extracted the forest stand age data layer through the upland hardwood woodland and forest masks to assess stand age within our target system. Because the ISA does not provide criteria for determination of succession, we derived quantiles from the extracted stand age layer, and used the bottom quantile (bottom 20%) of imputed values in upland hardwood woodlands (i.e., stand age ≤22.2 years) and forests (i.e., stand age ≤19.5 years) to represent young and successional forests in the landscape. We assessed acreage by summing the count of pixels within each geographic construct and multiplying by pixel resolution (250 x 250 m = 62,500 m2) and converting to acres using the Tabulate Area tool in ArcGIS. We also could not determine the target size of the landscape within which to evaluate distribution of successional stages. Therefore, to be consistent with summary metrics the other endpoints in the assessment we assumed the landscape of interest to be at the scale of a HUC12 watershed. For display we calculated the proportional area (acres upland hardwood (stand age bottom quantile/acres HUC 12) within each HUC 12 watershed using the tabulate area tool in ArcGIS.
