Belowground Allies, Aboveground Threats: The Vulnerability of the Persian Oak (Quercus brantii Lindl.)- Arbuscular Mycorrhizal Fungi Symbiosis in a Changing Climate

Climate change poses a major threat to ecosystems worldwide, including Iran's ecologically important Zagros oak forests. These forests are experiencing accelerating decline due to climate-related stress and intensified human pressures, despite their key role in sustaining regional biodiversity. Soil health and the crucial symbiotic partnership between oak trees and arbuscular mycorrhizal fungi (AMF) are crucial for resilience in drought-prone Mediterranean environments. Due to a lack of comprehensive studies, this research aimed to analyze the root-associated microbiome of Persian oak (Quercus brantii) across western and southwestern Iran, specifically focusing on AMF diversity and their ecological role. Our study employed Illumina high-throughput sequencing of ITS and 18S rRNA V4 markers of root-associated fungal communities to assess taxonomic composition and diversity of 160 trees across eight different sites. Analyses revealed dominant fungal groups, including key AMF taxa like Glomeraceae and Claroideoglomeraceae, with significant spatial variation in diversity and community structure, likely influenced by regional and abiotic factors. While both ITS and V4 markers provided insights, the V4 region proved particularly effective for AMF profiling. In addition, the findings underscore the critical ecological function of the Persian oak canopy in creating a favorable microclimate and the essential symbiotic partnership with AMF for drought tolerance and nutrient uptake. However, our study ultimately concludes that despite this crucial symbiosis, the Zagros oak forests remain highly vulnerable to increasing pressures from agricultural expansion and the escalating impacts of climate change, seasonal wildfires, and declining groundwater levels, which pose significant threats to their long-term survival.