Microbial metabolic potential to transform plant residual carbon

Abstract

The pathways of exogenous carbon (C) mineralization and retention in soil have been widely investigated via analyses of microbial fingerprints (e.g., phospholipid fatty acids (PLFAs)) and footprints (e.g., amino sugars). However, the potential of soil resident microbiota to metabolize plant-derived substrates remains unclear. This study aimed to clarify how microbial growth cumulatively contributes to residual C transformation under different substrate qualities and soil management practices. Nonlinear fitting of the cumulative contribution of PLFA-based microbial growth to residual C decomposition showed that among microbial groups, fungi metabolized grains to the greatest extent, and gram-negative bacteria contributed the most to root C metabolism, whereas gram-positive bacteria and actinomycetes were generally less competent in the decomposition of all residues. The sequestration of leaf and root C in amino sugars was greater without tillage than with tillage, whereas an opposite tillage trend was observed for grain-derived galactosamine. Our findings highlight that the potential of fungi and bacteria for residual C transformation depends on residue quality. Furthermore, high-quality residue (e.g., grain) transformation is strongly exacerbated by soil disturbance, whereas few tillage-facilitated effects occur with a decline in substrate quality (e.g., leaf and root).