Fire regimes of the pinon-juniper woodlands of Big Bend National Park and the Davis Mountains, west Texas, USA

摘要

While pinon woodlands cover much of arid North America, surprisingly little is known about the role of fire in maintaining pinon forest structure and species composition. The lack of region-specific fire regime data for pinon-juniper woodlands presents a roadblock to managers striving to implement process-based management. This study characterized pinon-juniper fire regimes and forest stand dynamics in Big Bend National Park (BIBE) and the Davis Mountains Preserve of the Nature Conservancy (DMTNC) in west Texas. Mean fire return intervals were 36.5 and 11.2 years for BIBE and DMTNC, respectively. Point fire return intervals were 150 years at BIBE and 75 years at DMTNC. Tree regeneration in west Texas pinon-juniper woodlands occurred historically during favorable climatic conditions following fire years. The presence of multiple fire scars on our fire-scar samples and the multicohort stands of pinon suggested that low intensity fires were common. This study represents one of the few fire-scar-based fire regime studies for pinon-juniper woodlands. Our results differ from other studies in less topographically dissected landscapes that have identified stand-replacing fire as the dominant fire regime for pinon-juniper woodlands. This suggests that mixed-severity fire regimes are typical across southwestern pinon forests, and that topography is an important influence on fire frequency and intensity.