PS 13-126 - Woodland soil fungal communities vary more with soil characteristics than nearby tree identity at a local scale

Background/Question/Methods

Forest soil fungal communities can vary spatially due to many factors including climate, plant diversity, and gradients of soil characteristics. However, open questions remain on the relative influence of these factors on fungal community composition and associated function, especially at different scales. For instance, small-scale variations in soil fungal communities may drive local variation in nutrient cycling and decomposition. Clarifying the roles of these multiple factors can improve our predictions of soil fungal community and biogeochemical cycling responses to future environmental changes. To explore these themes, we examined the influence of tree species identity, tree compositions, and spatial heterogeneity of soil characteristics on the soil fungal communities of tree saplings in a small suburban woodland in Armonk, NY, USA. A field assay was developed using 2-year-old saplings of two common eastern US trees (Pinus resinosa and Quercus rubra) planted alone and planted together around two mature tree species (Q. rubra and Fagus grandifolia) distributed throughout this woodland. We also compared variations in community composition with fungal potential enzymatic activity. At the end of the experimental period, soil fungal community composition and associated function were analyzed with amplicon sequencing of the ITS1 region and fluorometric extracellular enzymatic assay.

Results/Conclusions

From our samples, we identified ~1,600 ASVs dominated by the phylum Basidiomycota, followed by Ascomycota and Mortierellomycota. Our experimental assay had variations in potential influential factors including tree diversity and tree compositions, but we found that these factors explained only a small proportion of the total variation in community composition. While tree species identity was not a major influential factor, different areas of the woodland did have distinct fungal communities possibly due to variations in soil characteristics including soil moisture, total C, total N, and concentrations of Al. In addition to the lack of broad community compositional differences, we could also detect no significant difference in extracellular enzymatic activity. Despite the established relationship between fungal community composition and tree identity, the results suggest that in this woodland, these communities have assembled largely independent of the aboveground tree distribution. This may also suggest that untested soil characteristics and stochastic factors, such as dispersal and ecological drift, may also be important in structuring these communities. Overall, this study provides further evidence of the relationship between soil fungal communities and aboveground plant diversity.