Multi-scale response of avian communities to prescribed fire: implications for fuels management and restoration treatments in southwestern ponderosa pine forests

Abstract

Ponderosa pine (Pinus ponderosa) forests of the American Southwest were historically characterized by frequent, low severity surface fires that mediated the occurrence of extreme wildland fire events. Over the last century, increases in fuels have transformed these forests in ways that help facilitate stand-replacing crown fires. To reduce the risk of such fires, land managers are implementing fuels treatments in progressively larger stands of ponderosa pine. For the period 1 April to 30 September, 1986-2000,1 examined contributing landscape factors related to the occurrence of large (≥ 20 ha) fires in the forested region of northern Arizona. I used a Bayesian weights-of-evidence approach to model and map the probability of occurrence based on all fire types and lightning-caused fires alone. In total, large fires burned 101,571 ha on my study area and fires due to lightning were more frequent and extensive than human-caused fires. For all fires, probability of occurrence was greatest in areas of high topographic roughness and lower road density. My results indicated that seasonal large fire events were a consequence of non-random patterns of occurrence that can have extensive influence on the regional fire regime. I used a before-after/control-impact experimental design to examine the multiscale response of avian communities to large (~ 260-400 ha) prescribed fire treatments on four ponderosa pine forests in Arizona and New Mexico. I used distance sampling and an information-theoretic approach to quantify changes in density for 14 species and three trait-based clusters of species among 82 total species detected on four sites before (May- June, 2002-2003) and after (May-June, 2004-2005) prescribed fire treatments. I used spatial models to evaluate the post-fire response of species and clusters using initial forest conditions and levels of fire severity. At the point level, five species exhibited a treatment response and two of these species were positively associated with increasing levels of fire severity. Among the four study sites, I identified few non-random patterns of cluster- and community-level response to treatment. In the short term, breeding bird communities in southwestern ponderosa pine forests appear tolerant of low-to-moderate intensity prescribed fire treatments at multiple spatial scales and across multiple geographic locations.