Background P. sylvestris var. mongolica is one of the most commonly used tree species for large-scale greening in northern China, and in-depth investigation of the structural and functional characteristics of root-associated fungal communities in P. sylvestris var. mongolica, along with their soil driving factors is crucial for understanding its growth adaptation mechanisms and ensuring forest sustainability management.

Methods This study took the P. sylvestris var. mongolica plantation located in the Saihanba Mechanical Forest Farm, Chengde city, Hebei province. Using high-throughput sequencing technology, the study analyzed the structure and functional characteristics of root-associated fungal communities in young (18 years), middle aged (26 years), near mature (37 years) and mature (50 years) P. sylvestris var. mongolica plantations, and also explored the influences of soil properties on root-associated fungal communities.

Results 1) With the increase of forest age, the diversity of root-associated fungi in P. sylvestris var. mongolica showed a trend of first decreasing, then increasing, and then decreasing again, which had no significant correlation with soil properties. 2) Root-associated fungi in P. sylvestris var. mongolica plantations within the study area were classified into 9 phyla, 32 classes, 76 orders, 148 families, and 243 genera, Ascomycota (72.25%) and Basidiomycota (25.8%) occupy the absolute phylum level. The dominant genus in the young forest was Leptodophora, while the dominant genus in other stages was Phialocephala. 3) Soil properties contributed more than forest age and location to the root-associated fungal community structure of P. sylvestris var. mongolica. Among these soil properties, soil total carbon was the most important soil factor in shaping the structure of the root-associated fungal community. 4) The main trophic mode of root-associated fungal in the young stage was saprotrophyic, while at other stages, symbiotic was the main type, and endophytic fungi occupied dominant position in the ecological functional groups. Soil total carbon and organic carbon were significantly negatively correlated with the relative abundance of symbiotic fungi.

Conclusions In summary, the root-associated fungal community of P. sylvestris var. mongolica in the Saihanba region demonstrates complex and diverse species composition, with significant differences in diversity observed across different forest ages. Soil total carbon is the most important soil factor in shaping the structure of root-associated fungal communities. The dominant trophic mode are saprotrophic and symbiotic fungi.