Landscape heterogeneity following high‐severity fire in California's forests

Abstract

ABSTRACTMany at‐risk wildlife species depend upon high‐severity fire patches to create “complex early seral forest” (CESF) land cover, characterized by an abundance of snags, downed logs, shrub patches, and regeneration of trees. However, concern has been expressed about whether high‐severity fire might result in persistent type conversion to nonforest, or from pine (Pinus spp.) dominance to forest predominantly consisting of white fir (Abies concolor), Douglas‐fir (Pseudotsuga menziesii), and incense‐cedar (Calocedrus decurrens), as opposed to heterogeneous natural succession and ephemeral occurrence of CESF. If type conversion is common, it could in time harm other at‐risk species that depend on dense, late‐successional forest for some of their habitat needs. I investigated postfire patterns in high‐severity fire patches within yellow pine (Pinus ponderosa and Pinus jeffreyi) and mixed‐conifer forests in California, USA, using field plots evenly spaced along random transects into the interior of patches within fires that occurred from 1999 to 2013. I found natural conifer regeneration in ≥80% of plots, even >300 m into patches. Conifer regeneration was greater closer to low–moderate‐severity areas. Areas with lower conifer regeneration, where CESF would have the greatest longevity—comprised only 4.6% of these fire areas. Pine species dominated regeneration deeper into the interior of large high‐severity patches, and fir–cedar‐dominated at patch edges. Shrubs did not impede conifer regeneration, but greater densities of conifer saplings reduced shrubs, and sapling growth increased with time‐since‐fire. My findings suggest heterogeneous land‐cover patterns are resulting from natural succession in high‐severity fire patches. © 2018 The Wildlife Society.