Dominance of Arbuscular Mycorrhiza and Ectomycorrhiza Drive Shifts in Soil Nematode Communities along the Deep Soil Profile in a Young Post-Agricultural Forest

Mycorrhizal type of the dominating vegetation is one of the main drivers of soil functioning, especially across forest ecosystems. While the topsoils (above 30 cm) are mostly influenced by the soil organic matter that comes from the leaf litter decomposition, and therefore is mostly determined by the plant species, the subsoil is highly affected by the rhizosphere processes and directly—by the activity of the soil microbiome, including bacteria and fungi. The current research was aimed at testing how the mycorrhizal type of tree stand affects the vertical distribution of soil nematode communities, driven by the abundance of organic resources and soil parameters. To address this, we assessed the density of individual taxa and feeding types of nematodes along a one-meter soil profile in ectomycorrhiza (ECM) and arbuscular mycorrhiza (AM) dominated soils of a temperate experimental forest (MyDiv experiment). We show that nematode community composition differed between ECM and AM-dominated topsoils, while the subsoil communities were similar. At the same time, the dominating mycorrhizal type drove the density distribution across the one-meter soil profile for individual taxa, including some bacterivores, fungivores, and omnivores, indicating the specific feeding preferences of individual nematode taxa. In general, our data represents the slow change in nematode communities that occurs with the soil development after reforestation, simultaneously reflecting the strong legacy effect of post-agricultural soil.