Identifying biomarkers for shifts in microbial community structure in Irish Grasslands: the influence of context-specific drivers

Abstract Purpose This study investigated the comparative influence of regional/climatic difference in agronomic potential (‘Region'), natural drainage (‘Drainage’) and grassland management intensity (‘Manage’) on soil physicochemical variables, microbial community structure and soil potential extracellular enzymatic activity across 37 Irish grassland sites. Methods Soil samples were collected in a structured manner from representative sites, and soil physicochemical parameters were measured. Soil microbial community structure was determined by phospholipid fatty acid analysis and different potential soil extracellular enzymatic activities were measured through both fluorometric and colorimetric assays. Doubly-nested PERMANOVA and ANOVA models were performed in R to evaluate the impact of the examined factors on multivariate and univariate variables, respectively. Results A doubly-nested PERMANOVA model revealed that each of the three factors exerted a significant influence on soil microbial community structure ( p < 0.05). The factor ‘Drainage’ did have a stronger influence on the abundance of the fatty acid biomarker for the arbuscular mycorrizal fungi (effect size = 20.54%) than ‘Region’ had (effect size = 10.05%), with ‘Manage’ having no significant effect. In contrast to soil microbial community structure, individual soil potential extracellular enzymatic activities mostly either did not significantly respond to any factor, or significantly responded to ‘Region’ only ( p < 0.05, i.e., β-N-acetyl-glucosaminidase, arylsulfatase and acid phosphatase). Conclusion The study highlights the value of considering localized environmental drivers in studies relating to soil parameters at the national level, to support effective, context-specific management strategies for soil biodiversity conservation and national monitoring schemes of soil biology.