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Background Forest and nonforest ecosystems of the western United States are experiencing major transformations in response to land-use change, climate warming, and their interactive effects with wildland fire. Some ecosystems are transitioning to persistent alternative types, hereafter called “vegetation type conversion” (VTC). VTC is one of the most pressing management issues in the southwestern US, yet current strategies to intervene and address change often use trial-and-error approaches devised after the fact. To better understand how to manage VTC, we gathered managers, scientists, and practitioners from across the southwestern US to collect their experiences with VTC challenges, management responses, and outcomes. Results Participants in two workshops provided 11 descriptive case studies and 61 examples of VTC from their own field observations. These experiences demonstrate the extent and complexity of ecological reorganization across the region. High-severity fire was the predominant driver of VTC in semi-arid coniferous forests. By a large margin, these forests converted to shrubland, with fewer conversions to native or non-native herbaceous communities. Chaparral and sagebrush areas nearly always converted to non-native grasses through interactions among land use, climate, and fire. Management interventions in VTC areas most often attempted to reverse changes, although we found that these efforts cover only a small portion of high-severity burn areas undergoing VTC. Some areas incurred long (>10 years) observational periods prior to initiating interventions. Efforts to facilitate VTC were rare, but could cover large spatial areas. Conclusions Our findings underscore that type conversion is a common outcome of high-severity wildland fire in the southwestern US. Ecosystem managers are frontline observers of these far-reaching and potentially persistent changes, making their experiences valuable in further developing intervention strategies and research agendas. As its drivers increase with climate change, VTC appears increasingly likely in many ecological contexts and may require management paradigms to transition as well. Approaches to VTC potentially include developing new models of desired conditions, the use of experimentation by managers, and broader implementation of adaptive management strategies. Continuing to support and develop science-manager partnerships and peer learning groups will help to shape our response to ongoing rapid ecological transformations.

High-severity fires in dry conifer forests of the United States Southwest have created large (>1000 ha) treeless areas that are unprecedented in the regional historical record. These fires have reset extensive portions of Southwestern ponderosa pine (Pinus ponderosa Lawson & C. Lawson var. scopulorum Engelm.) forest landscapes. At least two recovery options following high-severity fire are emerging. One option is for post-fire successional pathways to move toward a return to the pre-fire forest type. Alternatively, an area may transition to persistent non-forested ecosystems. We studied regeneration patterns of ponderosa pine following eight fires in Arizona and New Mexico, USA, that burned in dry conifer forests dominated by ponderosa pine during a recent 18-year regional drought period, 1996 to 2013. Our a priori hypotheses were: 1) the most xeric areas within these severely burned dry conifer forests are least likely to regenerate to the pre-fire forest type due to persistent post-fire moisture stress; and 2) areas farther away from conifer seed sources have a lower likelihood of regeneration, even if these areas are climatically favorable for post-fire ponderosa pine establishment. We evaluated our hypotheses using empirical data and generalized linear mixed-effects models. We found that low-elevation, xeric sites are more limiting to conifer regeneration than higher-elevation mesic sites. Areas >150 m from a seed source are much less likely to have ponderosa pine regeneration. Spatial interpolations of modeled post-fire regeneration of ponderosa pine across the study landscapes indicate expansive areas with low likelihood of pine regeneration following high-severity fire. We discuss multiple post-fire successional pathways following high-severity fire, including potentially stable transitions to non-forest vegetation types that may represent long-term type conversions. These findings regarding landscape changes in Southwest forests in response to fires and post-fire regeneration patterns during early-stage climate warming contribute to the development of better-informed ecosystem management strategies for forest adaptation or mitigation under projected hotter droughts in this region.