Aims <p>Soil carbon cycling in orchard systems is profoundly influenced by tillage regime (TR) and mulching material (MT); however, their synergistic effects on soil carbon cycling and microbial functional traits remain poorly understood.</p> Methods <p>A field experiment was conducted to analyze soil physicochemical properties, active carbon-pool components, and functional gene structure of carbon‑cycling microbial community under two tillage regimes: clean tillage (CT) and natural grass cultivation (NG), and four mulch treatments: no mulch (NM), shredded branches mulch (SDM), composted shredded-branch mulch (SDCM), and shredded branches-derived biochar mulch (SDBM).</p> Results <p>Compared with CT, NG increased soil nutrients, active carbon components, key carbon- and nitrogen- cycling enzymes activities, and the abundance of key carbon-cycling bacterial phyla, including <i>Proteobacteria</i> and <i>Chloroflexi</i>. Under NG, different MT treatments significantly promoted soil carbon cycling and microbial function, particularly SDCM, significantly increasing soil nutrients content and carbon pool management index (CPMI) while boosting active carbon components and related enzyme activities. Functional gene analysis revealed that SDCM synergistically promoted carbon cycling through methanol metabolism (K04480) and pectin degradation (K22994) while inhibiting methanogenesis (M00356).</p> Conclusion <p>NG combined with SDCM most effectively enhanced soil-carbon sequestration by optimizing microbial community structure and metabolic networks, providing a theoretical basis for sustainable orchard management.</p>