Objective This study aimed to compare the storage of total organic carbon and the distribution of active organic carbon in ant nests and reference soils and to provide the key data support for expounding the impact of ant colonization on processes and mechanisms of carbon sequestration in forests of neighbouring mountains in the Napahai Wetlands, Yunnan Provinve of southwestern China.

Method We compared total organic carbon storage, active organic carbon components (i.e., total, microbial, easily oxidized, particulate, and dissolved organic carbon (total organic carbon, microbial biomass carbon, easily oxidized carbon, particulate organic carbon, and dissolved organic carbon), and their distributions (MBC/TOC, EOC/TOC, POC/TOC, DOC/TOC) in ant nests and the reference soils in the spruce-fir community of neighbouring mountains in the Napahai Wetlands. We also explored the ant-induced changes in soil physicochemical properties on organic carbon storage and active organic component distribution.

Result Ant colonization significantly affected SOC accumulation and carbon distribution (P < 0.05). Soil organic carbon storage was 5.7 times higher in ant nests than in reference soil; the concentrations of TOC, MBC, EOC, and POC in ant nests increased by 3.8, 2.7, 4.0, and 3.5 times, respectively. The average ratios of MBC/TOC, POC/TOC, and DOC/TOC in reference soils were 0.43%, 3.30% and 3.21% higher than that in the reference soils. In contrast, the ratio of EOC/TOC in ant nests was 1.50% higher than that in reference soil. The soil layer and treatment had interactive effects on concentrations of TOC, MBC, POC, and DOC (P < 0.05), while there was no significant interaction on EOC. The regression analysis showed that MBC, POC, DOC and EOC can explain 96.45%, 96.35%, 95.13% and 94.27% of the changes in total organic carbon. Principal component analysis showed that soil density, total nitrogen and available phosphorus were the main controlling factors of SOC storage, while available nitrogen and phosphorus, soil density were the main driving factors of active carbon accumulation, and total kalium was the main influencing factor for the distribution of particulate organic carbon and dissolved organic carbon.

Conclusion Ant nesting mainly regulates the total organic carbon storage and distribution of active organic carbon components in the forest soil of neighbouring mountains in the Napahai Wetlands by changing environmental factors such as soil compaction and nitrogen and phosphorus nutrient conditions. These results would contribute to the understanding of fauna regulatory mechanisms for soil carbon sequestration in the forests of neighbouring mountains in the Napahai Wetlands.