A bird’s eye view of ecosystem conversion: Examining the resilience of piñon-juniper woodlands and their avian communities in the face of fire regime change

• Published in: Forest ecology and management Vol. 546; p. 121368
• Main Authors: Woolet, Jamie, Stevens-Rumann, Camille S., Coop, Jonathan D., Pejchar, Liba
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.10.2023
• Subjects: administrative management; biodiversity; Bird communities; birds; canopy; climate change; ecological function; Ecological memory; ecosystems; fire regime; forest ecology; forest types; habitat preferences; land use; pinyon-juniper; Piñon-juniper; refuge habitats; Refugia; Resilience; seedlings; shrublands; shrubs; species; Turdus migratorius; Vegetation type conversion; Vireo; Virginia; Western United States; wildfires; wildlife; woodlands; Western United States; Virginia; Vegetation type conversion; Refugia; Bird communities; Ecological memory; Piñon-juniper; Resilience
• ISSN: 0378-1127; 1872-7042
• DOI: 10.1016/j.foreco.2023.121368

•PJ woodlands 25–27 years post-fire lacked tree seedlings and were dominated by shrub and grass cover.•Lack of recovery in burn patches was prevalent in bird communities, where several obligate and semi-obligate species were absent or had a low habitat use.•Findings from the vegetation and bird communities indicate these woodlands either have a long recovery time or are transitioning to non-forest cover types.•Patches of refugia preserved plant and avian attributes, sharing similar vegetation characteristics and PJ-associated bird species to the unburned reference sites. Climate change and land-use legacies have caused a shift in wildfires and post-fire growing conditions. These changes have strong potential to diminish the resilience of many ecosystems, with cascading effects and feedbacks across taxa. Piñon-juniper (PJ) woodlands are a diverse and widespread forest type in the western US and are home to many obligate and semi-obligate bird species. As such, this system is ideal for understanding wildfire resilience, or lack thereof, in terms of both vegetation and wildlife associations. This study evaluated post-fire vegetation structure and associated avian communities following three wildfires; one that burned one year prior to sampling (recent fire), and two that burned approximately 25 years previously (old fires). Vegetation characteristics and the habitat use of PJ-associated bird species were compared across severely burned patches, unburned refugia, and unburned sites outside of the burn perimeter. We expected wildfire to alter vegetation and bird usage for the first few years post-fire, which we observed in our recent burns. However, even 25-years post-fire, little recovery to PJ woodland had occurred and the associated bird communities had not returned, compared to unburned areas. No piñon regeneration was observed in any burned areas and no juniper regeneration in the recent fire. Piñon seedling densities in unburned sites and refugia averaged 80 ha−1 and 151 ha−1, respectively, while juniper seedling densities were 220 ha−1 in both habitat types. Habitat use for thirteen PJ-associated species were modeled, three of which (Woodhouse’s Scrub Jay, Ash-throated Flycatcher, and Virginia’s Warbler) used all habitats. Four species (American Robin, Gray Vireo, Black-throated Gray Warbler, and Gray Flycatcher) were essentially absent from the old burn habitat, reflecting species-specific need for mature piñon or juniper trees and/or greater canopy cover. Conversely, birds that were present in the old burn habitat (including Virginia’s Warbler, Blue-gray Gnatcatcher, Woodhouse’s Scrub-jay, Ash-throated Flycatcher, and Spotted Towhee) are typically associated with habitat edges, high shrub cover, or cavity nests. Altered vegetation structure and bird habitat use in burned areas 25 years post-fire are evidence for enduring conversion to non-forest vegetation types. However, unburned refugia embedded in burned areas maintain forest attributes and support obligate bird communities, supporting ecological function and biological diversity.