Post-fire forest management often relies on external indicators of tree damage to classify burn severity and predict survival. However, visually intact trees may undergo internal changes that influence its long-term recovery. Wood-inhabiting fungal communities may provide early biological signals of tree physiological changes that are not detectable through visual assessment alone.
This study examined sapwood fungal community in three boreal tree species in Alberta: lodgepole pine (Pinus contorta), white spruce (Picea glauca), and trembling aspen (Populus tremuloides), for their responses to fire across three burn severity classes (low, medium, and high). Changes in community composition is monitored across two years (2023 and 2024). Wood samples were ground, DNA extracted and sequenced for community analysis.
Sapwood fungal community responses differed among tree species, burn severities, and across time. Pine and spruce showed similar responses, with both showing immediate dominance by saprotrophs after high-severity fire. However, under low and medium severity fire, there were with no immediate change in community structure. After one year, pine and spruce showed signs of delayed mortality through the emergence of saprotrophic and pathogenic fungi. Aspen showed immediate but irregular changes to fungal community structure and sustained those changes even after one-year post-fire.
These findings suggest that pine and spruce under low and medium severity fire require prolonged monitoring for best management decisions. Pine especially requires additional monitoring of bark beetle-vectored blue-stain fungi for the tree’s importance in forest timber. Highly burnt pine and spruce, however, should be salvaged immediately after fire. Aspen trees do not contribute directly to the forest sector, but are key fire breaks, hence will need to focus on conservation management and delayed intervention.