Simulated treatment effects on bird communities inform landscape‐scale dry conifer forest management

Abstract

Human land use and climate change have increased forest density and wildfire risk in dry conifer forests of western North America, threatening various ecosystem services, including habitat for wildlife. Government policy supports active management to restore historical structure and ecological function. Information on potential contributions of restoration to wildlife habitat can allow assessment of tradeoffs with other ecological benefits when prioritizing treatments. We predicted avian responses to simulated treatments representing alternative scenarios to inform landscape‐scale forest management planning along the Colorado Front Range. We used data from the Integrated Monitoring in Bird Conservation Regions program to inform a hierarchical multispecies occupancy model relating species occupancy and richness with canopy cover at two spatial scales. We then simulated changes in canopy cover (remotely sensed in 2018) under three alternative scenarios, (1) a “fuels reduction” scenario representing landscape‐wide 30% reduction in canopy cover, (2) a “restoration” scenario representing more nuanced, spatially variable treatments targeting historical conditions, and (3) a reference, no‐change scenario. Model predictions showed areas of potential gains and losses for species richness, richness of ponderosa pine forest habitat specialists, and the ratio of specialists to generalists at two (1 km2 and 250 m2) spatial scales. Under both fuels reduction and restoration scenarios, we projected greater gains than losses for species richness. Surprisingly, despite restoration more explicitly targeting ecologically relevant historical conditions, fuels reduction benefited bird species richness over a greater spatial extent than restoration, particularly in the lower montane life zone. These benefits reflected generally positive species associations with moderate canopy cover promoted more consistently under the fuels reduction scenario. In practice, contemporary forest management is likely to lie somewhere between the fuels reduction and restoration scenarios represented here. Therefore, our results inform where and how active forest management can best support avian diversity. Although our study raises questions regarding the value of including landscape‐scale heterogeneity as a management objective, we do not question the value of targeting finer scale heterogeneity (i.e., stand and treatment level). Rather, our results combined with those from previous work clarify the scale at which targeting structural heterogeneity and historical reference conditions can promote particular ecosystem services.

Birds of the Burn: Avian Community and Functional Guild Variation Five Years Post-Fire in Warm–Dry Mixed Conifer, Southwest Colorado

“…High-burn severity areas typically have a high snag density, which favors cavity-nesting species such as woodpeckers and insectivorous species that eat insects associated with recently deceased trees [28]. Aerial insectivores, such as flycatchers, are known to respond favorably to moderately open canopies that favor their hunting strategies [29]. The successional growth of shrubs and aspen following low-and moderateseverity fire favors shrub-nesting species [29].…”

“…Aerial insectivores, such as flycatchers, are known to respond favorably to moderately open canopies that favor their hunting strategies [29]. The successional growth of shrubs and aspen following low-and moderateseverity fire favors shrub-nesting species [29]. In low-and moderate-severity fires, large trees may produce more cones when released from pressure from surrounding small trees.…”

“…In low-and moderate-severity fires, large trees may produce more cones when released from pressure from surrounding small trees. This increase in cone production may favor granivorous species such as Clark's Nutcracker and Red Crossbill [29]. The evaluation of functional guilds can illuminate the type and Avian communities in post-burn mixed conifer forests have been studied extensively in some regions of the country, but there is little recent information about these systems in Southwest Colorado [3,9,13,28,30].…”

“…This study addresses the variation in burn severities by stratifying burn areas by change in percent canopy cover, according to RAVG data (Rapid Assessment of Vegetation Condition after Wildfire). The time since fire has also been revealed to be a crucial component to post-burn avian communities, as many groups follow successional trajectories initiated by fire and continue to be influenced by fire up to a decade post-burn [24,29,33]. Many studies in mixed conifer areas post-fire have been conducted three years or less following a burn, with studies five years post-fire lacking in the Southwest [9,25].…”