Dominance of coniferous and broadleaved trees drives bacterial associations with boreal feather mosses

The composition of ecologically important moss-associated bacterial communities seems to be mainly driven by host species but may also be shaped by environmental conditions related with tree dominance. The moss phyllosphere has been studied in coniferous forests while broadleaf forests remain understudied. To determine if host species or environmental conditions defined by tree dominance drives the bacterial diversity in the moss phyllosphere, we used 16S rRNA gene amplicon sequencing to quantify changes in bacterial communities as a function of host species (Pleurozium schreberi and Ptilium crista-castrensis) and forest type (coniferous black spruce versus deciduous broadleaf trembling aspen) in eastern Canada. The overall composition of moss phyllosphere was defined by the interaction of both factors, though most of the bacterial phyla were determined by a strong effect of forest type. Bacterial alpha-diversity was highest in spruce forests, while there was greater turnover (beta-diversity) and higher gamma-diversity in aspen forests. Unexpectedly, Cyanobacteria were much more relatively abundant in aspen than in spruce forests, with the cyanobacteria family Nostocaceae differing the most between forest types. Our results advance the understanding of moss-associated microbial communities among coniferous and broadleaf deciduous forests, which are important with the increasing changes in tree dominance in the boreal system.

Automated summary

The composition of moss-associated bacterial communities is mainly influenced by host species and environmental conditions related to tree dominance. The overall composition of moss phyllosphere is determined by the interaction of both factors, with forest type having a strong influence on the bacterial phyla. Bacterial diversity is higher in spruce forests, while turnover and gamma-diversity are higher in aspen forests. Cyanobacteria, particularly the family Nostocaceae, are more abundant in aspen forests compared to spruce forests.