Insights into fungal communities in some benchmark agricultural soils of Alberta, Canada

Soil micro-organisms, including fungi, are integral to soil functions such as biogeochemical cycling, pollutant degradation and plant growth promotion. Soil fungi are influenced by environmental perturbations such as agricultural parameters and thus may be a potential soil health indicator. We hypothesized that tillage intensity, crop type and herbicide application would impose changes on soil fungal community composition and diversity and that these shifts would be associated with changes in soil physico-chemical properties. We examined the response of soil fungal communities to various agricultural parameters at a provincial scale from benchmark agricultural sites in Alberta. Surface soil samples from 26 farm locations were collected from benchmark sites across Alberta. Samples were grouped by crop type, tillage intensity and herbicide application. Physico-chemical properties of soil samples were measured. Following DNA extraction of soil samples, we used amplicon sequencing through primers for the ITS2 (internal transcribed spacer) region and analysed fungal community diversity, composition and predicted function. Multivariate analyses showed that ecoregion was the strongest environmental predictor of variation in fungal community composition. Amongst farming practices and soil properties, crop type was the most important identified driver of fungal community composition, followed by tillage intensity and soil pH. The genera Mortierella, Pseudogymnoascus and Fusicolla, as well as functional traits, including soil saprotrophs and mycoparasites, were responsive to variation in crop type, tillage levels and herbicide application. We observed minor changes in overall fungal diversity, but significant differences in species composition, in all farming treatments. The heterogeneity of samples also varied significantly by tillage intensity and crop type. No indicator species was strongly associated with crop type, tillage intensity or herbicide system. Bray-Curtis dissimilarity in the fungal community was positively correlated with soil pH and base saturation and negatively correlated with soil cation exchange capacity, organic matter and clay content. We conclude that management practices affect different attributes of soil fungal communities, and fungal community heterogeneity is a responsive attribute that could be used for soil health assessment in Alberta. The potential linkage we found between agricultural parameters, fungal community heterogeneity and soil parameters could be further investigated as a metric in soil health assessment.