Inhabitants of Landscape Scars: Succession of Woody Plants After Large, Severe Forest Fires in Arizona and New Mexico

Abstract

Understanding consequences of changes in climate and fire regimes for succession in plant communities is critical for conservation planning at broad spatial and temporal scales. We selected two sites that burned in high-severity fire decades ago and studied succession in the woody plant community and its variations across two environmental gradients; elevation and distance from a lower- severity/unburned edge. By overlaying an ordination of data for woody species on the modeled environmental gradient most closely related to variation in communities, we analyzed the interaction of life-history traits of species and landscape heterogeneity at each study site. Species that resprout from surviving roots were widespread across the distance gradient 28 years after the La Mesa fire in New Mexico. Species that reproduce from off-site seed, including Pinus ponderosa, were more prevalent where resprouters (e.g., Quercus) were less important in defining communities. At Saddle Mountain, Arizona, 45 years post-fire, we observed neighborhood interactions across the elevation gradient, for example, where shade-tolerant conifers (e.g., Abies concolor) occurred in understories of Populus tremuloides .A t both sites, greater cover of woody plants that reproduce from off-site seed at shorter distances from a lower-severity/unburned edge suggested migration of these species following the model of wave-form succession. In contrast to studies that emphasize undesirable effects when forest transitions to openings and alternative habitats, our research elucidates the need for further consideration of both young forest communities and the persistent species and communities described as landscape scars in conservation plans for forest systems of the southwestern United States.