Soil carbon stabilization associated with iron-aluminum complexes and microbial communities in paddy

Rice paddies play a pivotal role in global carbon cycling, offering significant potential for climate change mitigation and sustainable agriculture. This study investigates the synergistic effects of long-term fertilization, iron-aluminum-soil organic carbon (Fe(Al)-SOC) complexes, and microbial communities on soil organic carbon (SOC) stabilization across major rice-growing regions. Black soils exhibited the highest SOC content (43.9 g kg −1 ), surpassing other soils by 41.6–82.6 %, suggesting distinct stabilization mechanisms. Key findings include: (1) Fe(Al)-SOC complexes and aromatic carbon (20.4 % in black soils) jointly enhanced long-term SOC preservation; (2) CO 2 emissions were controlled by nitrogen (N) and phosphorus (P) stoichiometry and physical protection within 0.25–0.5 mm aggregates; (3) Bacterial abundance negatively correlated with SOC and light fraction organic carbon (LFOC) levels, concomitant with reduced CO 2 emissions; and (4) N/P fertilization boosted carbonyl-C (recalcitrant pool) while maintaining Alkyl-C (31.7 % in brick-red soils), indicating balanced C stabilization. Critically, we demonstrate that Fe/Al-microbial interactions—where Fe/Al complexes modulate microbial composition and activity—are central to SOC storage. These results provide a mechanistic framework for optimizing rice cultivation practices to maximize soil carbon storage through the synergistic management of mineral-organic complexes, microbial ecology, and fertilization strategies. • SOC and molecular C-groups (alkyl/O-alkyl/aromatic) co-determined by soil types. • Black soils store more carbon via enriched aromatic-C and carbonyl-C components. • Higher bacterial abundance correlates with lower SOC stocks. • Fungal dominance drives CO 2 emissions in paddy soils.