Fungal response to wildfire in a southeastern wildland-urban interface

Fungi are key to belowground ecosystem function, yet post-fire recovery of fungal communities has not been examined in many ecosystems. A massive wildfire in 2016 in the Great Smoky Mountains National Park (GSMNP) and surrounding urban landscape (Gatlinburg, TN) presented a novel opportunity to study post-fire fungal response within an urban-forest ecosystem. We surveyed soils and plants in GSMNP and Gatlinburg, TN 1.5-2 years post-fire to assess colonization of arbuscular mycorrhizal fungi (AMF, aseptate hyphae) and decomposers/pathogens (septate hyphae) from 13 plant species across 18 sites, (9 park, 9 urban).

Overall, colonization by aseptate (intraradical R²= 0.46, P= 0.03) and septate (intraradical R²= 0.19, P= 0.01; extraradical R²= 0.07, P= 0.03) hyphae decreased with increasing fire intensity. This pattern was primarily driven by GSMNP sites (intraradical, R²= 0.28, P< 0.01; extraradical R²= 0.26, P< 0.01), with colonization decreasing in roots but not soils—suggesting soil recovery precedes root recovery for symbiotic AMF. Meanwhile, the decrease in intra- and extraradical septate colonization suggests this community recovers more slowly after wildfire than AMF. The sensitivity of our fungal communities to wildfire alongside predicted changes in wildfire regimes suggests declines in fungal abundance throughout southeastern Appalachia.