2026/07/21 by Martin P. Girardin, Yan Boulanger, Raquel Alfaro-Sánchez +1 · 2 voices
Environmental Science · Earth and Planetary Sciences · #Fire effects on ecosystems #Plant Water Relations and Carbon Dynamics #Tree-ring climate responses
paper · doi:10.1071/wf25274
Background Atmospheric dryness, measured as vapor pressure deficit (VPD), is rising with climate warming, yet its joint impacts on tree growth, fire activity and biomass dynamics remain understudied at broad spatial scales. Aims We examine how interannual variability in VPD relates jointly to tree growth, annual area burned (AAB) and aboveground biomass dynamics across western North American boreal forests. Methods We compiled time series of spring and summer VPD (1951–2022), tree-ring based basal area increments (BAI; 1950–2009), AAB (1950–2020) and Landsat-derived aboveground biomass increments (AGBI, 1985–2014). Pairwise relationships were quantified with correlations accounting for persistence; a structural equation model summarizes significant linkages. Key results Rising VPD promoted BAI reductions and increased AAB, whereas AGBI increased with higher BAI and declined with increasing AAB. SEM revealed indirect pathways linking VPD to biomass increments through its effects on BAI and AAB. Conclusions VPD acts as a coordinating driver of boreal dynamics, synchronizing fire activity and growth suppression while indirectly influencing biomass accumulation. Implications These findings illustrate the need to move beyond isolated treatment of fire and growth in ecosystem interpretations. Incorporating these dual pathways into fire behavior and carbon budget models is essential for anticipating boreal forest trajectories under continuing warming.