Ecological conditions within forest stands are also important indicators of ecosystem integrity. Priority wildlife species are frequently shown to exhibit preference for a specific range of conditions of canopy cover and basal area, tree diameter, midstory cover, and other forest characteristics within a stand. The ISA recommends a range of overstory canopy cover between 20-80% for upland hardwood woodlands and >80% for upland hardwood forests in the Ozark Highlands subgeography. We used the 2011 National Land Cover Database (NLCD) U.S. Forest Service Tree Canopy (analytical) product (USDA Forest Service Remote Sensing Applications Center 2014) combined with the woodland and forest masks derived above for assessment of overstory canopy cover within upland hardwoods in the Ozark Highlands and other GCPO subgeographies. The USFS forest canopy layer contains values representing the unmasked proportion of each 30x30m pixel covered by tree canopy (0 to 100%) produced using random forest regression algorithms (Breiman 2001, Cutler et al. 2007). To align with resolution of the other hardwood forest condition data we sought to generate an average proportion of tree canopy cover across 30 m pixels within each 250 m upland hardwood pixel in the GCPO geography. To calculate average canopy cover we first aggregated 30 m canopy cover cells to 240 m using a mean function and a cell factor of 8 (the aggregate function in ArcGIS only allows for cell factor aggregation, not aggregation to a desired pixel size, whereas the resample function in ArcGIS does not allow for calculation of averages over the resampled cell size). We then resampled the 240 m cell aggregate to 250 m resolution using a nearest neighbor algorithm. This produced an approximation of the average tree canopy cover within each 250 m forested wetland pixel. We next extracted the average tree canopy layer through the upland hardwood woodland and forest masks, then reclassified to extract woodlands with 20-80% canopy cover and forests with >80% canopy cover.
