Changes in snag populations on national forest system lands in Arizona, 1990s to 2000s

Abstract

Snags receive special management attention as important components of forest systems. We used data from the US Department of Agriculture (USDA) Forest Service Forest Inventory and Analysis Program, collected during two recent time periods (1995 to 1999 and 2001 to 2010), to evaluate trends in snag populations in two forest types in Arizona. Densities of snags ≥4 in. dbh increased by 21 and 72% between these time periods in mixed conifer and ponderosa pine (Pinus ponderosa) forest, respectively. Proportions of plots meeting USDA Forest Service guidelines for density of large snags (defined as snags≥18 in. dbh and≥30 ft tall) increased between time periods in both forest types (from 19 to 45% in mixed conifer and from 5 to 17% in ponderosa pine forest), but large snags remained relatively sparse, especially in less productive ponderosa pine forests. More than 50 and 75% of sampled plots lacked large snags entirely in mixed conifer and ponderosa pine forest, respectively.