Standing dead trees, or snags, are an important habitat element in any forested system, and provide diurnal or seasonal shelter for many LCC priority species. The ISA landscape endpoint for snag density in upland hardwood woodland and forest systems targets one large (≥16” dbh) snag for every five acres of forest (or approximately ~0.2 large snags/acre), reflected by cavity-roosting habitat needs of the silver-haired bat (Lasionycteris noctivagans) and ample other avian, and mammalian species that require cavities in snags to carry out their life history. We used USFS imputed density of large (>16” dbh) snags data (USDA Forest Service Remote Sensing Applications Center, personal communication) extracted through the upland hardwood woodland and forest masks for assessment of snag density within the Ozark Highlands and other GCPO geographies. The USFS imputed snag 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 Forest Inventory and Analysis National Program (FIA). Density of large snags was imputed from plot-level FIA data coalescing standing dead trees >5” with dbh >16”. Note estimates of snag density were calculated on a per-acre-of-land basis, though forested lands were the primary sampling frame. The USFS-imputed percent large snag density layer was created in the target resolution for this assessment (250 m). We used an extract by mask function in ArcGIS to delineate large snag density in upland hardwood woodland and forest, using the USFS imputed large snag density layer as input data and the woodland and forest data as masks. We then reclassified the product to pull out pixels with large snag density with at least 0.2 large snags/acre. Note the ISA endpoint targets exactly 0.2 snags >16”/ac, but due to data limitations we have assessed this endpoint to include all large snags with 0.2/ac density or greater. 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 forested wetland (>0.2/ac snags >16”)/acres HUC 12) within each HUC 12 watershed using zonal statistics in ArcGIS.
