  Recent studies have revealed effects of various tree species on soil physical
and chemical properties. However, effects of various tree species on
composition and activity of soil microbiota and the relevant controls remain
poorly understood. We evaluated the influence of tree species associated with
two different mycorrhizal types, ectomycorrhiza (EcM) and arbuscular mycorrhiza
(AM), on growth, biomass and metabolic activity of soil fungal and bacterial
communities using common garden tree species experiments throughout Denmark.
The soil microbial communities differed between six European tree species as
well as between EcM (beech, lime, oak and spruce) and AM (ash and maple) tree
species. The EcM tree species had higher fungal biomass, fungal growth and
bacterial biomass, while AM species showed higher bacterial growth. The results
indicated that microbial community composition and functioning differed between
groups of tree species with distinct litter qualities that generate soil C/N
ratio and soil pH differences. The mycorrhizal association only partly
explained litter quality and soil microbial species differences since lime was
more similar to AM tree species. In addition, our results indicated that tree
species-mediated soil pH and C/N ratio were the most important variables
shaping microbial communities with a positive effect on bacterial and a
negative effect on fungal growth rates. The results suggest that tree
species-mediated microbial community composition and activity may be important
drivers of the different vertical soil C distribution previously observed in AM
and EcM tree species.
