Soil- and plant-associated fungi and bacteria are an important part of many ecosystems as they can affect plant health, growth and stress tolerance. However, it remains poorly understood whether the microbiomes differ between conifer species growing in the same site conditions and between tree ecosystem compartments. The main aim of the study was to describe and compare the microbiomes of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.), growing in a boreal forest common garden experiment on adjacent forest plots, to analyse the tree species effect on the composition of the needle and surface soil organic-mineral horizon microbiomes. The needle and surface soil organic-mineral horizon bacterial and fungal microbiomes were simultaneously analysed by full-length 16S and ITS sequencing on a long-read sequencing platform; however, the bacterial analysis was restricted to soil samples. The highly abundant bacterial phyla in both pine and spruce soil were Actinomycetota, Pseudomonadota, Planctomycetota and Acidobacteriota. The dominant fungal phyla in pine and spruce surface organic-mineral soil was Basidiomycota, while the needles were dominated by Ascomycota. The results showed an effect of tree species on the soil bacterial and fungal microbiomes and needle fungal microbiomes based on alpha diversity, which was higher for Norway spruce compared to Scots pine. The results indicated that Norway spruce might be able to support higher microbial diversity, which could potentially be due to differences in needle longevity, root exudates, litter input and its degradation, between pine and spruce. Furthermore, the results indicated distinct microbiomes between the soil and needle compartments.
Bizjak-Johansson et al. (Thu,) studied this question.