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

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.