Soil legacy effects on a temperate tree species depend on the mycorrhizal types and phylogenetic distance of the conditioning trees

Abstract Associations of trees with arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) fungi often shape distinct microbial communities in soils. Whether this distinction can create different soil legacies and to what extent such legacies are correlated to phylogenetic relatedness between the trees remains largely unresolved. In this study, we examine the soil legacy effects of five AM and three EcM conditioning tree species on a dual‐mycorrhizal poplar species Populus tomentosa and estimate dependence of the legacy on the phylogenetic distance between these species and poplar. EcM tree species overall had a weaker soil legacy effect on biomass and foliar C/N ratio of the poplar than AM trees, and this correlated with lower relative abundances of the bacterial genus Rubrobacter and the fungal genus Mortierella in soils of EcM trees compared to AM soils. Soil legacy effects on biomass of test poplar correlated negatively with its phylogenetic distance from the conditioning trees. A negative correlation also occurred for concentration of total phenolics in the foliage of poplar with phylogenetic distance, but only when the conditioning trees were EcM species. The negative dependence of soil legacies on phylogenetic distance was mediated by a decreased abundance of the bacterial genera Agromyces , Blastococcus and the fungal genera Pseudogymnoascus and Metarhizium , as well as an increased abundance of the fungal genera Aspergillus and Clonostachys in the soil. Our results indicate that the effects of soil microbial legacies on a given dual‐mycorrhizal species may depend not only on the mycorrhizal type of the conditioning trees but also on its phylogenetic distance from these trees. Read the free Plain Language Summary for this article on the Journal blog.