Soil microbiome diversity on Sable Island, Nova Scotia

Abstract

The soil microbiome is essential for ecosystem functioning and influences both above- and below-ground communities. Sable Island is a sand bar with a large feral horse population, which has been shown to affect marram grasslands more than heathlands. Feral horses can have negative effects on soil microbiomes by reducing microbial diversity and abundance, but there has been no previous research on soil microbes on Sable Island. Determining the microbial composition and the driving factors of diversity is crucial for effective ecosystem management. Our goal was to determine differences in microbial α-diversity and β-diversity across vegetation types, soil pH, organic matter, and phosphorous. This study also serves as an overall survey of bacterial and fungal diversity. We expected microbial α-diversity to be lower in marram grasslands than in heathlands, and the microbial β-diversity to differ between vegetation types. Using eDNA from soil samples, we identified bacteria with 16S and fungi with ITS2 DNA barcodes and performed soil analyses from 80 samples from 16 sites on the island. We identified a total of 812 bacterial and 336 fungal ASVs. Our results indicate that bacterial α-diversity was significantly (p < 0.05) affected by the vegetation type, soil pH, and organic matter content, but not phosphorous concentration. In contrast, fungi were robust to variation in the environmental factors and fungal α-diversity was not significantly affected by any variables. Microbial α-diversity was not lower in marram grasslands than in heathlands, potentially due to horse activities damaging the vegetation types similarly and an increase in nutrient deposition in the marram. Microbial β-diversity of presence/absence was not significantly affected by any variable. Identifying drivers of soil microbiome diversity is important for effective ecosystem management in vulnerable ecosystems such as Sable Island.