Changes to vegetation structure and tree species composition drive bird species turnover following disturbance in southwestern United States mixed-conifer forest
Jones H , Merriell B, Swan M , Johnson J, Siegel R. 2026. Changes to vegetation structure and tree species composition drive bird species turnover following disturbance in southwestern United States mixed-conifer forest. Forest Ecology and Management. 609
Abstract: Mixed-conifer forests in the southwestern United States are vulnerable to climate-change-mediated disturbance, and provide habitat for many regionally declining birds. Drought stress and increased prevalence of high-severity wildfire can reshape the canopy structure, age distribution, and tree species composition of mixed-conifer forests, though there is little understanding of how these habitat features correlate with avian abundances. We fit Bayesian N-mixture models to eight years of monitoring data from Bandelier and Grand Canyon National Parks, including sites at Bandelier which experienced high-severity wildfire. We related breeding-season densities of 34 mixed-conifer forest bird species to 12 microhabitat variables to identify microhabitat associations. We also examined changes to bird and tree community composition over time. Tree and bird community composition significantly shifted following the high-severity wildfire, but smaller shifts also occurred after prescribed fire at Grand Canyon. There were no community-wide microhabitat associations with breeding-season density. Instead, declining canopy cover, subcanopy foliage cover, and foliage height diversity as well as increasing sapling density (perhaps a proxy for loss of mature trees) all affected distinct subsets of disturbance-sensitive birds. However, 62% of species were resilient to changes in canopy cover. Associations with tree species composition were also important, with declining local tree richness and subalpine tree (subalpine fir, quaking aspen, spruces) basal area, as well as increasing ponderosa pine dominance, each negatively associated with a subset of bird species. One third of the community responded negatively to increasing live tree basal area, however, suggesting the potential importance of disturbance in shaping breeding-season densities.
- Type
- Journal Article
- Authors
- Jones, Harrison; Merriell, Brandon; Swan, Megan; Johnson, James (Matthew); Siegel, Rodney
- Units
- BAND , GRCA
- Keywords
- Bandelier National Monument, Bayseian model, birds, Grand Canyon National Park, habitat, mixed-conifer forest, SCPN, Southern Colorado Plateau Network, southwestern United States, vegetation