Biogenic volatile organic compound (BVOC) emissions from boreal forest floors during the first years after wildfire: effects of stand age and management

Abstract. Boreal forests emit a wide range of biogenic volatile organic compounds (BVOCs) that influence atmospheric chemistry and climate through oxidation reactions and the formation of secondary organic aerosols. These emissions originate from plant metabolism, microbial activity, and storage pools such as litter, and vary in response to environmental conditions and disturbances. Wildfires, the dominant natural disturbance in boreal ecosystems, substantially alter ecosystem structure and carbon cycling, yet their effects on BVOC emissions during the early post-fire years remain poorly understood.

Here, we quantified BVOC emissions during the first years after wildfire across gradients of stand age, fire severity, and post-fire management. BVOC emissions were strongly controlled by tree mortality and management practices. High-severity fire in young stands resulted in persistently low emission rates and a shift away from monoterpene dominance, likely reflecting limited biomass and substrate availability. In contrast, sites with surviving mature trees exhibited elevated emissions dominated by monoterpenes, driven by litter-derived storage pools. Salvage logging caused a transient increase in emissions in the first year after fire due to accumulated needle debris, followed by a rapid decline as litter inputs were depleted. Conversely, reforestation led to increasing emissions over time.

These results demonstrate that early post-fire BVOC dynamics are regulated by the interaction between disturbance severity, stand age and management strategies, leading to distinct emission trajectories in the early recovery phase. Such shifts in BVOC emission magnitude and composition may have important implications for post-disturbance atmospheric chemistry and climate feedbacks. Our findings highlight the need to account for disturbance legacy effects and management practices when representing BVOC emissions in large-scale models.