Management strategy influences landscape patterns of high-severity burn patches in the southwestern United States

Abstract

Context: Spatial patterns of high-severity wildfire in forests affect vegetation recovery pathways, watershed dynamics, and wildlife habitat across landscapes. Yet, less is known about contemporary trends in landscape patterns of high-severity fire or how differing federal fire management strategies have influenced such patterns. Objectives: We assessed fires managed for ecological/resource benefit and fires that are fully suppressed and investigated: (1) whether spatial patterns of high-severity fire differed by management strategy, (2) whether spatial patterns were related to fire size and proportion of high-severity fire, and (3) temporal trends in spatial patterns. Methods: We examined high-severity spatial patterns within large fires using satellite-derived burn severity data from 709 fires that burned from 1984-2017 in Arizona and New Mexico, USA. We calculated a suite of spatial pattern metrics for each individual fire and developed a method to identify those which best explained variation among fires. Results: Compared to managed fires, spatial pattern metrics in suppression fires showed greater patch homogeneity. All spatial pattern metrics showed significant relationships with fire size and proportion of high-severity fire for both management strategies. Mean annual spatiotemporal trends in suppression fires have moved toward smaller, more complex, fragmented patches since the early 2000s. Conclusions: Increases in fire size and proportion high-severity fire are driving more homogenous patches regardless of management type, with proportion high-severity more strongly driving average temporal trends. Anticipated shifts in fire size and severity will likely result in larger, more contiguous, and simple-shaped patches of high-severity fire within southwestern conifer forests.