Local soil characteristics determine the microbial communities under forest understorey plants along a latitudinal gradient.

• Soil microbial communities differed significantly under different plant species. • Within each plant species, soil chemistry was the main determinant for soil microbial community composition. • The most influential determinant in soil chemistry was soil acidity. • Large-scale environmental conditions only determined soil microbial community composition under grasses. • Land-use history was insignificant in determining soil microbial community composition. The soil microbial community is essential for maintaining ecosystem functioning and is intimately linked with the plant community. Yet, little is known on how soil microbial communities in the root zone vary at continental scales within plant species. Here we assess the effects of soil chemistry, large-scale environmental conditions (i.e. temperature, precipitation and nitrogen deposition) and forest land-use history on the soil microbial communities (measured by phospholipid fatty acids) in the root zone of four plant species (Geum urbanum , Milium effusum , Poa nemoralis and Stachys sylvatica) in forests along a 1700 km latitudinal gradient in Europe. Soil microbial communities differed significantly among plant species, and soil chemistry was the main determinant of the microbial community composition within each plant species. Influential soil chemical variables for microbial communities were plant species-specific; soil acidity, however, was often an important factor. Large-scale environmental conditions, together with soil chemistry, only explained the microbial community composition in M. effusum and P. nemoralis. Forest land-use history did not affect the soil microbial community composition. Our results underpin the dominant role of soil chemistry in shaping microbial community composition variation within plant species at the continental scale, and provide insights into the composition and functionality of soil microbial communities in forest ecosystems. [ABSTRACT FROM AUTHOR]