Aims <p>Neutral lipid fatty acids (NLFA) are key carbon reserves for microorganisms, influencing microbial growth and soil organic carbon (SOC) formation. Combining NLFA with phospholipid fatty acids (PLFA) provides insights into microbial community dynamics and carbon storage, yet their relationship with residuals accumulation remains unclear.</p> Methods <p>This study examined microbial community shifts and the link between microbial biomass and residues accumulation using PLFA, NLFA, and amino sugars in <i>Robinia pseudoacacia</i> plantations of varying ages (10, 15, 20, and 50 years) and cropland on the Loess Plateau, China.</p> Results <p>In plantation soils, total PLFA, NLFA, and amino sugars ranged from 3103~ 6916 pmol g⁻¹, 3893 ~ 4733 pmol g⁻¹, and 0.830 ~ 1.380 mg g⁻¹, respectively. As forest aging, microbial communities were bacterial-dominant, with gram positive bacteria (G⁺) showing a faster turnover than gram negative bacteria (G⁻). Compared to PLFA, NLFA and amino sugars showed stronger correlations, with G⁺ NLFA exhibiting the strongest positive relationship with all four amino sugars (R² = 0.17 ~ 0.39, p &lt; 0.05); to quantify this, we defined the amino sugars accumulation coefficient (ASAC), the ratio of amino sugars to G⁺ NLFA. ASAC increased by 2.1% ~ 108.0% during forest restoration, highlighting enhanced linkage between NLFA biomass and residue accumulation. ASAC was influenced by soil nitrogen and showed potential for SOC prediction.</p> Conclusions <p>The contribution of NLFA to microbial residues accumulation was greater than PLFA and should not be overlooked. This study highlighted NLFA’s role in microbial biomass–residue links and suggested integrating ASAC in SOC models.</p>