Detecting forested rock outcrops using focal range statistics: A case study with green salamanders

Abstract Rock outcrop specialists include many at‐risk species whose conservation requires effectively identifying and mapping outcrops. Canopy cover often obscures rock outcrops, making the mapping and detecting of these features difficult. Improvements in the availability of high‐resolution light detection and ranging data (LiDAR) provide opportunities to map outcrops, which has previously been conducted using a slope‐based method; however, this method exhibits varying success across different topographies and struggles to locate especially small outcrops. We measured the accuracy of a new method, focal range statistics, and compared it to the slope‐based method to detect and map outcrops in southern Ohio, USA, using a 0.75‐m digital elevation model (DEM) derived from LiDAR. This method exhibited low error and was notably better at detecting small outcrops compared to the slope‐based method. Focal range statistics also mapped 6 times more total outcrop area (243,027 m 2 ) than the slope‐based method, and field reconnaissance revealed 17 new localities of green salamander ( Aneides aeneus ), an outcrop specialist and state‐listed species. Applying focal range statistics to more widely available 3‐m DEM data detected outcrops with similar accuracy but resulted in mapping 4 times more area of rock outcrops. We recommend additional field testing with 3‐m DEM data to assess the accuracy of the topographic data sources with lower resolutions. Our study indicates that the use of focal range statistics can be a valuable tool for the conservation and management of outcrop specialists and offers notable advantages when used in regions with subtle topographic relief and small outcrops.