Fungal Diversity in Fire-Affected Pine Forest Soils at the Upper Tree Line

Forest fires represent a significant ecological disturbance in ecosystems that increasingly affects Pinus heldreichii H. Christ forests at the upper tree line in Montenegro, due to climate change and anthropogenic factors. Soil samples were collected from five high-altitude sites in the Kuči Mountains, including three post-fire sites (2-, 4-, and 6-years post-fire) and two unburned control sites. High-throughput sequencing and soil chemical analyses were conducted to assess fungal diversity, community composition, and soil nutrient properties. The results showed that fungal diversity was significantly higher in unburned soils compared to post-fire soils, with the most prominent changes in ectomycorrhizal fungi, which are crucial for pine regeneration. The fungal community composition differed markedly between the post-fire and unburned sites, with specific taxa such as Hygrocybe conica (Schaeff.) P. Kumm. and Solicoccozyma aeria (Saito) Yurkov dominating the post-fire environments. Despite this, the fungal richness did not significantly change over time (2-, 4-, or 6-years post-fire), suggesting the slow recovery of fungal communities in high-altitude environments. In addition to shifts in fungal biodiversity, the post-fire soils exhibited higher levels of available phosphorus, likely due to the conversion of organic phosphorus into soluble forms during combustion. However, the organic matter content remained unchanged. This study provided important insights into the long-term ecological impacts of forest fires on high-altitude P. heldreichii forests and underlined the importance of preserving unburned forest areas to maintain fungal biodiversity and support natural regeneration, as well as the potential need for active restoration strategies in fire-affected regions.