How do different ant species mediate CH4 fluxes in slash-burn tropical forest soils?

Abstract

As important structuring force in ecosystems, ants play crucial roles in driving source-sink processes of soil methane (CH₄) through a series of biotic and abiotic pathways. However, there is still uncertainty about how different ant species regulate CH₄ fluxes in slash-burn tropical soils. This study aimed to identify the pathways by which the different ant species (i.e., Pheidole capellini-honeydew harvester, Odontoponera transversa-predator, and Pheidologeton affinis-scavenger) control soil CH₄ fluxes in Xishuangbanna tropical forests, southwestern China. We observed a net CH₄ emission in the nests of three ant species (1.29 ± 0.047 μg m⁻² h⁻¹) and a net uptake in the reference soils (-1.60 ± 0.043 μg m⁻² h⁻¹). The contribution of three ant species to the reduction of annual total forest surface CH₄ uptake ranged from 0.06 % to 4.82 %. The P. capellini nests increased CH₄ emissions by 144.18 % compared with the reference soils, whereas O. transversa and P. affinis nests increased by 124.65 % and 111.71 %, respectively. In contrast with the reference soils, the greatest increase (33.7–511.1 %) in abundance of dominant methanogen taxa (Candidatus Thermoplasmatota and Euryarchaeota), methanogen Sobs index, soil water content, total organic carbon, and microbial biomass carbon was found in P. capellini nests. In contrast, the highest increase (92.0 %) in nitrate nitrogen was recorded in P. affinis nests. In particular, CH₄ fluxes were directly or indirectly driven by increased Candidatus Thermoplasmatota abundance (26.04 %), soil water content (15.41 %), and microbial biomass carbon (11.70 %), while the abundance of Methylomirabilota bacteria explained 7.76 % of variation in CH₄ fluxes. Our data indicate that CH₄ fluxes vary with ant species probably due to their differentiated modification on methanogenic bacterial abundance, micro-habitat, and microbial carbon in Xishuangbann tropical soils. This results would provide further insight into the contribution of soil fauna to greenhouse gas emissions from tropical forests.