Limited midstory density was also identified in the Integrated Science Agenda as an important component of upland hardwood systems in the GCPO geography, with midstory coverage ≤20% indicating a healthy additional vertical strata in the system. Midstory is an important habitat component for several ISA priority species, particularly those avian species who require midstory structure for nesting such as the wood thrush (Hylocichla mustelina). We again used plot-level Forest Inventory and Assessment data imputed at 250 m resolution across the GCPO LCC to assess tree density. The USFS imputed tree density data 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. Note estimates of midstory tree density were calculated on a per-acre-of-land basis, though forested lands were the primary sampling frame. Midstory density is calculated by using FIA Phase II crown class code (CCLCD) of 5, which indicates the amount of sunlight and the crown position in the canopy. A CCLCD = 5 indicated “overtopped” with trees and crowns entirely below the general canopy and receiving no direct light either from above or the sides. For this assessment a CCLCD of 5 was combined with a diameter (DBH) value between 4.3 and 9.8” to assess midstory crown position in the canopy. However, the ISA endpoint of midstory density ≤20% is not an appropriate metric because it could either be defined as ≤20% of total live tree midstory density or could be defined as ≤20% midstory canopy cover. We therefore could not calculate percent midstory cover from FIA data in these systems, but in the absence of a quantifiable relationship between density and percent cover we used the bottom quantile (bottom 20%) of imputed midstory density values in upland hardwood woodlands (i.e., midstory density <99.35 trees/acre) and forests (i.e., midstory density <141.5 trees/acre) as a surrogate for ≤20% midstory cover. We used an extract by mask function in ArcGIS to delineate midstory density within the target ranges in upland hardwood woodland and forest, using the USFS imputed midstory density layer as input data and the woodland and forest data as masks. We then reclassified the product to pull out pixels with midstory density <99.35 trees/acre for woodlands and <141.5 trees/acre for forests. 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. For display we calculated the proportional area (acres upland hardwood (midstory density target/acres HUC 12) within each HUC 12 watershed using zonal statistics in ArcGIS.