Mycobiome and microbiome resilience of alpine Norway spruce forests in response to disturbances: Can soil and endophytic microorganisms help drive an efficient forest management?

: Assessing biodiversity and ecosystem services of forests is pivotal to implement effective climate adaptation strategies, especially in unmanaged forests, which, according to the Nature Restoration Law (Reg. EU 2024/1991), are considered as reference systems to restore biodiversity-rich ecosystems. Forest biodiversity includes also the microbiota which can enhance tree ability to adapt to a broad spectrum of environmental stimuli, including anthropogenic disturbances like silviculture. The aim of this work was to compare the mycobiome and microbiome biodiversity, in both soil and plant compartments, between managed and unmanaged alpine Norway spruce forest stands, assessing the variations driven by forestry. Branches, wood, roots, and bulk soil samples were collected from mature spruce trees for bacterial and fungal metabarcoding in parallel with stand structure and soil proprieties. The effect of stand structure was evident in soil and root microbiota, especially for fungi, even if wood and crown compartments also showed peculiar features. Results showed a more favorable soil nutrient cycling in soil-root compartment of managed stand compared to the unmanaged one but also a higher presence of pathotrophic fungal guilds. On the contrary, in the unmanaged stand there was a higher coordination of microorganisms but the presence of potential pathogens in plant compartments. In conclusion, some specific taxa featured the study areas and thus the forest management suggesting the possibility to individuate biomarkers of anthropogenic disturbances that could help in the implementation of sustainable management strategies and the long-term monitoring of forest systems within the framework of climate adaptation and biodiversity restoration policies.