Snag distributions in relation to human access in ponderosa pine forests

Ponderosa pine (Pinus ponderosa) forests in western North America provide habitat for numerous cavity-using wildlife species that often select large-diameter snags for nesting and roosting. Yet large snags are often removed for their commercial and firewood values. Consequently we evaluated effects of human access on snag densities and diameter-class distributions at nine locations in ponderosa pine forests throughout the interior western United States. We found no relationship between small-diameter (23–50 cm diam breast ht [dbh]) snags and human access measures (i.e., road density, distance to nearest town, and topography). However, large-snag (≥50 cm dbh) density was best predicted by road density, which suggested a decline, on average, of 0.7 large snags/ha for every km of road/km2. Most locations had relatively high densities of small-diameter snags (