When balancing potentially competing objectives like single-species management with broader ecosystem values, landscape context is a key consideration. Restoration to increase resilience to drought and fire in historically open-canopy forests in fire-prone environments is constrained by concern for species that favor dense forest conditions. In this study, we assessed changes between historical and current 1) forest structure and composition and 2) extent of northern spotted owl (NSO) nesting and roosting (NR) or foraging (F) forest cover on 39,000 ha at the eastern edge of the current designation of the range of the NSO. Historical records depict a predominantly open-canopy landscape dominated by large ponderosa pine. Current conditions include more than a 600% increase in trees 15–53 cm dbh, substantial decline in trees ≥81 cm dbh, loss of the widespread distribution of trees ≥53 cm dbh, and loss of the dominance of ponderosa pine on mixed conifer sites. NSO habitat assessment involves a suite of attributes including: landscape context; species composition; canopy cover; basal area; average tree diameter; diameter diversity; and abundance of large trees, snags, canopy layers, coarse woody debris, and mistletoe. We tested for the presence of forest that met USFWS threshold values for two of these variables, canopy cover and basal area.
Results/Conclusions
Historically none of the area met the 60% canopy cover threshold for NR or F forest cover and almost none meets it currently. However, several NSO nesting pairs and individual birds have been observed in the study area over the last 20 years, and studies in other frequent-fire forests show that canopy cover as low as 50% may be functional for NSO. To assess the implications of lower threshold values, we tested for NR or F forest cover presence at half the recommended thresholds, considerably below published estimates. Only five percent of the area exceeded 30% canopy cover historically; much of the current forest exceeds it today. Forests in the project area are an isolated peninsula separated from higher-quality spotted owl habitat by several miles across water, ponderosa pine forest, and private land. Current dense conditions result from management actions and are vulnerable to fire and drought. The increase in canopy cover comes at the expense of loss of historical functions and processes and increasing vulnerability to fire and drought. Landscape context can determine where forest restoration takes precedence over maintaining dense forest cover in altered landscapes where existing, novel conditions favor at-risk species.