Soil microbial residue storage linked to soil legacy under biofuel cropping systems in southern Wisconsin, USA

Microbial residues can be a significant component of soil organic matter, and their component amino sugars are integrative indicators of biologically relevant ecosystem properties. We evaluate the impact of soil attributes, microbial functional group biomass, and cropping system type on soil amino sugar profiles in three model biofuel cropping systems in southern Wisconsin, USA. Total soil carbon and clay content explained differences in soil amino sugar profiles, with glucosamine and galactosamine more strongly related to soil carbon and muramic acid associated with clay content. Amino sugars were not correlated to cropping system or to microbial functional group lipid abundance, suggesting amino sugar differences among locations were due to differences in soil legacy properties such as total carbon, clay content and culture age rather than to current biotic drivers. The disconnect between the current biotic composition and legacies of past microbial activity suggests that microbial residues should be considered as trajectories over time rather than static system properties.