Variations in the Beech Tree Rhizosphere Microbiome Across Pedoclimatic Regions and Tree Age
The rhizosphere microbiome plays a pivotal role in forest ecosystem functioning by mediating nutrient cycling, supporting plant growth, and enhancing stress resilience. In particular, microbial diversity and activity associated with older trees may provide a key ecological role in maintaining the resilience of forest ecosystems. In this study, we investigated the taxonomic composition and functional potential of rhizospheric microbiomes associated with Fagus sylvatica across varying pedoclimatic conditions and tree age classes in the beech forest of Mount Amiata (Italy). Rhizospheric soils were sampled from young, medium-aged, and monumental trees along three altitudinal bands and compared with bulk soil controls. Microbial community composition was characterized using 16S rRNA amplicon sequencing, and functional potential was explored through shotgun metagenomics and the reconstruction of species-level genome bins. Our results revealed that altitude was the primary driver of rhizosphere microbiome variation, with a progressive shift from copiotrophic taxa at lower elevations to oligotrophic and stress-adapted lineages at higher elevations. Tree age also influenced rhizosphere microbiome structure in an altitude-dependent manner, with its effects becoming increasingly pronounced at the highest elevation. At high altitudes, monumental trees harbored more diverse and distinct microbial communities, enriched in taxa associated with nutrient cycling, stress tolerance, and plant growth-promoting traits. Overall, these findings emphasize the importance of the rhizosphere microbiome as a dynamic, adaptive life-support system linking tree longevity, environmental stress, and forest ecosystem resilience.
The rhizosphere microbiome plays a pivotal role in forest ecosystem functioning by mediating nutrient cycling, supporting plant growth, and enhancing stress resilience. In particular, microbial diversity and activity associated with older trees may provide a key ecological role in maintaining the resilience of forest ecosystems. In this study, we investigated the taxonomic composition and functional potential of rhizospheric microbiomes associated with Fagus sylvatica across varying pedoclimatic conditions and tree age classes in the beech forest of Mount Amiata (Italy). Rhizospheric soils were sampled from young, medium-aged, and monumental trees along three altitudinal bands and compared with bulk soil controls. Microbial community composition was characterized using 16S rRNA amplicon sequencing, and functional potential was explored through shotgun metagenomics and the reconstruction of species-level genome bins. Our results revealed that altitude was the primary driver of rhizosphere microbiome variation, with a progressive shift from copiotrophic taxa at lower elevations to oligotrophic and stress-adapted lineages at higher elevations. Tree age also influenced rhizosphere microbiome structure in an altitude-dependent manner, with its effects becoming increasingly pronounced at the highest elevation. At high altitudes, monumental trees harbored more diverse and distinct microbial communities, enriched in taxa associated with nutrient cycling, stress tolerance, and plant growth-promoting traits. Overall, these findings emphasize the importance of the rhizosphere microbiome as a dynamic, adaptive life-support system linking tree longevity, environmental stress, and forest ecosystem resilience.
UNIVERSITY OF BOLOGNA