Wildfire, salvage logging and warming: Their interactive effects on boreal conifer reforestation

Abstract In Boreal forests, wildfires are common disturbance agents, important for sustaining forest regeneration and ecosystem processes. However, climate warming has intensified fire activity and severity in recent years, and warmer conditions following fire can alter environmental factors affecting tree seedling survival and growth. Management interventions can potentially counterbalance the effects of fire severity and warming. Using a field experiment, we investigated the main and interactive effects of fire severity, experimental warming, understory shrub presence and salvage logging on the growth of different conifer ( Picea abies and Pinus sylvestris ) provenances, to provide insight about how tree seedlings of various species respond to multiple environmental drivers following fire. Our study shows that low fire severity without salvage logging resulted in poorer seedling above‐ground growth, whereas experimental warming and ericaceous shrubs removal increased seedling biomass regardless of fire severity or logging treatment. Our results suggest that enhanced light availability and reduced resource competition from the understory supports the growth of conifer seedlings following fire. Post‐fire warming further stimulated the growth of conifer seedlings (particularly in high‐severity burn areas) potentially due to increased early colonization by fast‐growing deciduous trees. Moreover, in warmer conditions, northern provenances of P. sylvestris planted in southern locations also showed greater height growth compared to local populations, highlighting the potential for assisted migration under climate change. Synthesis and applications. This study demonstrates that artificial regeneration through planting can support forest recovery following wildfire, especially under high fire severity in sites where natural regeneration is poor. Salvage logging can enhance the growth of P. sylvestris seedlings and indirectly benefit P. abies on low‐severity sites by facilitation by deciduous species that create favourable microhabitats. However, the broader ecological impacts of salvage logging (such as on biodiversity loss and soil and habitat structure) must be considered in management planning. Post‐fire vegetation management, including control of competitive ericaceous shrubs, may further improve seedling establishment. Selecting climate‐adapted seedling provenances can boost reforestation success under future warming. These findings support an adaptive management framework that integrates fire severity, logging intensity, understory control and assisted migration to foster resilient forest landscapes in a changing climate.