Unraveling edaphic, environmental, and management drivers of soil microbial communities via ester-linked fatty acid methyl esters using a multilocation agroecosystem study

Microbial communities are essential to soil functions within agroecosystems. Understanding interactions between agricultural management and soil biological properties is important for sustainability, however, broadscale inferences on these interactions are challenged by differences in site-specific characteristics. To identify the effects of conservation management on soil microbial communities, we conducted a multi-location study of 15 sites across the United States, which varied in crop management strategies and climate and edaphic characteristics. Microbial community composition was assessed by ester-linked fatty acid methyl esters (EL-FAME) with biomarkers for gram-negative bacteria, gram-positive bacteria, actinobacteria, saprotrophic fungi, and arbuscular mycorrhizal fungi. Among the edaphic characteristics considered in this study, soil organic C (SOC) was more correlated with EL-FAME than pH and clay content. Reduced tillage, cover cropping, and manure increased total EL-FAME and SOC, whereas crop diversity had no significant effect. Abundance of bacterial fatty acid biomarkers had stronger relationships to SOC (r2 = 0.64–0.65) than fungal biomarkers (r2 < 0.23), but fungi exhibited more sensitivity to management than bacteria. Though some fatty acids were sensitive to management across locations, manure had the overall largest effect on EL-FAMEs. This study revealed a strong response of the microbial community to conservation management practices regardless of location, but the magnitude differed across locations. Additionally, SOC and moisture deficit were key drivers of site-specific responses. Our multilocation study supports the utility of EL-FAMEs as an important soil health indicator that should be considered in national soil health assessments.