Foliar fungi on urban trees are important for tree health, biodiversity and ecosystem functioning. Yet, we lack insights into how urbanization influences foliar fungal communities. We created detailed maps of Stockholm region’s climate and air quality and characterized foliar fungi from mature oaks (Quercus robur) across climatic, air quality and local habitat gradients. Fungal richness was higher in locations with high growing season relative humidity, and fungal community composition was structured by growing season maximum temperature, NO₂ concentration and leaf litter cover. The relative abundance of mycoparasites and endophytes increased with temperature. The relative abundance of pathogens was lowest with high concentrations of NO₂ and particulate matter (PM_2.5), while saprotrophs increased with leaf litter cover. Our findings show that urbanization influences foliar fungi, providing insights for developing management guidelines to promote tree health, prevent disease outbreaks and maintain biodiversity within urban landscapes.

城市树木上的叶面真菌对于树木健康、生物多样性和生态系统功能非常重要。然而，我们缺乏对城市化如何影响叶面真菌群落的深入了解。我们创建了斯德哥尔摩地区气候和空气质量的详细地图，并根据气候、空气质量和当地栖息地梯度对成熟橡树（栎树）的叶面真菌进行了表征。生长季相对湿度高的地区真菌丰富度较高，真菌群落组成由生长季最高温度、NO ₂ 浓度和凋落物覆盖度决定。真菌寄生虫和内生菌的相对丰度随着温度的升高而增加。当 NO ₂ 和颗粒物 (PM _2.5 ) 浓度较高时，病原体的相对丰度最低，而腐生菌则随着落叶覆盖而增加。我们的研究结果表明，城市化影响叶面真菌，为制定管理指南提供见解，以促进树木健康、预防疾病爆发和维持城市景观中的生物多样性。