Short-term thinning effects on saprotrophic and ectomycorrhizal soil fungal communities in a Pinus halepensis common garden

Abstract Background and aim Soil fungal communities can vary in their abundance and diversity between host tree species, but also between genotypes within the same host tree species. However, there are conflicting results on the role of host tree genetics in shaping soil fungal communities and how silvicultural treatments can influence their dynamics. Methods We investigated whether genetic variation among 20 populations representing five ecotypes of Pinus halepensis, the most widespread tree species in the Mediterranean basin, affects their soil fungal community, before and after a thinning treatment. Seedlings from these 20 populations were planted in 1996 in a common garden experiment (eastern Spain) under uniform climatic and soil conditions. In October 2019, a 50% thinning treatment was carried out and soil samples were collected immediately before and one year after thinning. Results Before thinning, no significant differences in soil fungal composition were observed between ecotypes. However, saprotrophic richness increased significantly in three ecotypes and saprotrophic diversity in one ecotype one year after thinning. Conversely, the ectomycorrhizal fungal community diversity and composition of the five ecotypes showed non-significant changes following thinning. Conclusion Our results suggest that genetic differentiation in the host tree plays a minor role in shaping the ectomycorrhizal and saprotrophic communities of Mediterranean Aleppo pine forests. Furthermore, the contrasting response of the ectomycorrhizal and saprotrophic communities to thinning treatment highlights the resilience of ectomycorrhizal communities to short-term disturbances such as thinning, while emphasizing the ability of the saprotrophic communities to exploit newly available resources.