Soil fauna mediate stage‑dependent home‑field advantage: roles of decomposer ability and litter quality

Home-field advantage (HFA) describes faster litter decomposition in native habitat than in foreign habitats, reflecting the adaptability of decomposer communities. As key contributors to decomposition, soil fauna have often been overlooked in HFA studies. We conducted a litter transplant experiment in a subtropical common garden using three representative tree species: Castanopsis ( Castanopsis carlesii ), Chinese fir ( Cunninghamia lanceolata ), and sweetgum ( Liquidambar formosana ). Three litterbag mesh sizes were used to regulate soil‑faunal access and to explore how soil fauna mediate the temporal dynamics of HFA and its underlying mechanisms. HFA occurred primarily in the 2 and 3 mm mesh treatments and was generally absent in the 0.025 mm treatments, with the direction and magnitude of HFA varying among litter species and decomposition stages. Sweetgum litter showed positive HFA at 0–60 % mass loss, Castanopsis litter exhibited declining negative HFA at 60–100 % mass loss, and fir litter displayed negative HFA at 0–60 % mass loss. Structural equation modeling revealed that DART‑derived decomposer ability primarily regulated HFA at the 0–60 % mass loss stage, modulated by litter-specific leaf area (SLA), magnesium (Mg), iron (Fe), soil nitrogen (N), and soil moisture. At 60–100 % mass loss, litter quality dominated HFA dynamics: initial litter lignin content, dynamic carbon (C): N and C: phosphorus (P) ratios promoted HFA, while litter potassium (K) content reduced HFA. Our results highlight stage-dependent interactions among soil fauna, decomposer ability, and litter traits in regulating HFA. By linking decomposer ability with shifts in substrate properties during decomposition, this study provides further insight into litter-decomposer relationships and their potential implications for C cycling in subtropical forests.