Microbial life-history strategies and nutrient limitation modulate soil organic carbon stability under nitrogen addition in subtropical plantations

Although different forms of N addition had consistent directions and pathways of effect on MNC and CCE, organic N exerted a stronger effect on microbial phosphorus limitation and a greater promotion of CCE. Furthermore, N addition significantly decreased the ratios of MNC:SOC and MNC:CCE. The shift of microbial communities toward K-strategists combined with intensified nutrient limitations represented the key regulatory pathway underlying the decline in MNC and increase in CCE, thereby weakening SOC stability.

Taken together, short-term N addition markedly reshaped SOC fractions and weakened soil carbon stability, with microbial life-history strategies and nutrient limitations acting as central mediators. These findings highlight the necessity of integrating N forms and SOC fractions to more accurately assess the regulatory effects of atmospheric N deposition on critical carbon cycling processes in subtropical forests.