Trait-based and phylogenetic filtering of arbuscular mycorrhizal fungal communities under long-term agricultural practices

We explored how long-term agricultural practices affect arbuscular mycorrhizal (AM) fungal traits and community structure. We sampled soil and roots from a 26-year-old field experiment comprising 16 replicated treatments, in which we manipulated tillage intensity (moldboard vs. chisel plow), fertilization (organic vs. mineral) and crop rotation (continuous barley vs barley-forage rotations) in a factorial design (N = 64). We measured AM fungal community-aggregated traits, namely the abundance of vesicles, arbuscules, extraradical mycelium (ERM) and spores. We characterized root-borne and soil-borne AM communities using Illumina sequencing. Crop rotation was the main factor controlling AM fungal traits, with more arbuscules and ERM found in forage rotation plots, and more vesicles and spores found in continuous barley plots. Members of the Glomeraceae family were preferentially associated with continuous barley whereas the Gigasporaceae and Diversisporaceae families were overrepresented in the first stage of crop rotation. Trait-based and phylogenic filtering of AM fungal communities allowed us to speculate on different life history strategies among taxonomic families. AM community structure in soil responded to fertilizer type, whereas root-borne communities responded to crop rotation. We found the first evidence of temporal niche partitioning as a potential driver of coexistence among AM fungal taxa, resulting in higher species richness (i.e. storage effects). Crop rotation scheme strongly influences functional traits and coexistence of AM fungi, more so than soil disturbance intensity or fertilization regime. Future work is required to understand the implications of these shifts in AM fungal community structure for crop productivity.