<p><b>W</b>ildfires are increasingly affecting boreal conifer forests, altering their chemical defences and carbohydrate reserves in ways that may affect their susceptibility to subsequent herbivore threats. We quantified monoterpenes and non-structural carbohydrates in the phloem of lodgepole pine across three treatments (unburned, burn-year, one-year post-fire) to identify fire-induced chemical changes and their temporal dynamics. Monoterpene concentrations rose sharply immediately following the fire but declined after one year. Non-structural carbohydrates showed compound-specific responses: starch and sucrose concentrations reduced post-fire, with partial recovery of sucrose, while glucose increased, and fructose exhibited a delayed response. Multivariate analysis revealed sucrose, starch, and specific monoterpenes as key compounds distinguishing the treatments. Elevated monoterpene concentrations immediately post-fire likely decreased susceptibility to insects; however, the subsequent decline in defences and accumulation of sugars suggest the emergence of a distinct post-fire window of increased vulnerability. These findings improve our understanding of fire-induced chemical shifts and can help predict forest vulnerability to interacting biotic stressors under a changing climate.</p>