Is it what's inside that matters? A conserved microbiome in woody tissues of Pinus radiata

Understanding the interaction of endophytic microbiomes and their tree hosts may provide insights into wood formation and quality. Given the role of wood in carbon and nutrient cycling, this will provide valuable insights for forest growth and carbon cycling globally. Furthermore, the management of these interactions may add new value to wood-and fibre-based forest products. We assessed the microbiome of outer and inner bark, cambium tissue, year 2-8 wood increments, and the pith of 11 Pinus radiata trees, a widely planted, model conifer species. Diverse prokaryotic and fungal microbiomes were present in all trees, with communities structured by tissue type (p<0.001). Inner and outer bark tissues had high richness and the most distinct communities. Microbiome richness was lowest in year 2 through to year 8 wood, and the communities in these samples had similar composition. Prokaryote communities were dominated by Alpha-Beta-, and Gamma-proteobacteria, Actinobacteria, Firmicutes (Clostridia and Bacilli). Within fungal communities, Sordariomycetes comprised over 90% of the taxa present. Microbiomes of cambial and pith tissues were distinct to those niches. Overall, we provide further support that the wood of conifers is host to distinct microbiome communities. Microbiomes in these niches are profoundly placed to impact tree physiology, health, and fitness, through to ecosystem function and global carbon cycles.