Coarse woody debris assay in northern Arizona mixed-conifer and ponderosa pine forests

Abstract

Coarse woody debris (CWD) provides important ecosystem services in forests and affects fire behavior, yet information on amounts and types of CWD typically is limited. To provide such information, we sampled logs and stumps in mixed-conifer and ponderosa pine (Pinus ponderosa) forests in north-central Arizona. Spatial variability was prominent for all CWD parameters. Correlations between amounts of CWD and current forest structure (tree density and basal area) were relatively weak. Most plots in mixed-conifer forest exceeded current USFS guidelines for retention of large logs. In contrast, 50% of ponderosa pine plots contained no large logs, and only 37% met current guidelines for log retention. Biomass of CWD in mixed-conifer forest typically fell within or above recommended levels for this forest type, whereas biomass of CWD in ponderosa pine forest typically fell within or below recommended levels. These results provide empirical data on amounts and types of CWD in this area and establish a baseline for monitoring CWD. The pronounced spatial variability in CWD parameters argues for managing CWD at broad spatial scales, rather than attempting to maintain average characteristics on every piece of ground.