Distribution patterns of fungal taxa and inferred functional traits reflect the non-uniform vertical stratification of soil microhabitats in a coastal pine forest

In boreal systems, soil profiles typically consist of distinct stratified
horizons, with organic layers at the surface overlying deeper mineral
horizons providing microhabitat variation along a depth gradient, and
vertical stratification of fungal communities along such soil profiles is
commonly observed. We studied fungal community structure in a coastal pine
forest along a gradient of decreasing influence from the coast. In this
system, the vertical stratification pattern of soil microhabitats (defined
here as organic, mineral with roots, and mineral without roots; O, MR, and
MN, respectively) is non-uniform; organic horizons are sometimes buried
under drifting sand dunes. Our results show that soil microhabitats are
distinct with respect to physiochemical characteristics, community
composition, and OTU richness. While community composition was partly
related to depth and distance from the coastal forest edge, microhabitat
appeared to have the strongest influence. A closer inspection of the OTUs
with the highest relative sequence abundance within each microhabitat
revealed that microhabitats support functionally distinct fungal
communities with respect to trophic mode and growth morphology. These
results suggest that in coastal pine forests, variation in soil
microhabitats contributes to the high fungal diversity found below-ground
and may play an important role in optimizing nutrient cycling.