Dryland forest management alters fungal community composition and decouples assembly of root- and soil-associated fungal communities

Land management practices considerably influence ecosystem processes and functioning, particularly in dryland ecosystems where nutrient and water limitations have direct (via effects on productivity) and indirect (via effects on soil biota) effects on ecosystem properties. Fungi in soils and associated with roots play critical roles in soil nutrient cycling and plant nutrient acquisition, but their responses to land management practices in dryland ecosystems remain equivocal. Here we evaluate the responses of fungal communities in roots and soils associated with a Eucalyptus saligna plantation after six years of forest management practices (irrigation and fertilisation) and in two different microenvironments within treated plots, in the presence and absence of understorey grasses. We observed that the richness and evenness of fungal communities were higher in soil than in root samples, but these two parameters did not vary among any of the management treatments. Effects of fertilisation and irrigation on fungal community composition were observed and appeared to be related to variation in soil pH, moisture, and nitrogen availability. Both fertilisation and irrigation decreased the ratios of ectomycorrhizal fungi to total fungi and increased the frequencies of saprotrophic and/or plant pathogenic fungi. We observed that some OTUs were shared between soil and root-associated fungal communities but that fertilisation was associated with lower frequencies of shared OTUs, suggesting a decoupling of these communities. In the absence of grasses, where only tree roots were present, we observed fewer tight relationships between fungal occurrence in root and soil samples. Our findings highlight the importance of forest management practices for fungal community assembly processes in dryland ecosystems, which may have consequences for the predictability of fungal community dynamics and nutrient cycling.