ABSTRACT
Exploring the effects of ant nests on soil CH4 emissions in the secondary tropical forests is of great scientific significance to understand the contribution of soil faunal activities to greenhouse gas emissions. With static chamber-gas chromatography method, we measured the dry-wet seasonal dynamics of CH4 emissions from ant nests and control soils in the secondary forest of Syzygium oblatum communities in Xishuangbanna. We also examined the linkages of ant-mediated changes in functional microbial diversity and soil physicochemical properties with CH4 emissions. The results showed that: 1) Ant nests significantly accelerated soil CH4 emissions, with average CH4 emissions in the ant nests being 2.6-fold of that in the control soils. 2) The CH4 emissions had significant dry-wet seasonal variations, which was a carbon sink in the dry seasons (from -0.29±0.03 to -0.53±0.02 µg·m-2·h-1) and a carbon source in the wet seasons (from 0.098±0.02 to 0.041±0.009 µg·m-2·h-1). The CH4 emissions were significantly higher in ant nests than in control soils. The CH4 emissions from the ant nests had smaller dry-wet seasonal variation (from -0.38±0.01 to 0.12±0.02 µg·m-2·h-1) than those in the control soils (from -0.65±0.04 to 0.058±0.006 µg·m-2·h-1). 3) Ant nests significantly increased the values (6.2%-37.8%) of soil methanogen diversity (i.e., Ace and Shannon indices), temperature and humidity, carbon pools (i.e., total, easily oxidizable, and microbial carbon), and nitrogen pools (i.e., total, hydrolyzed, ammonium, and microbial biomass nitrogen), but decreased the diversity (i.e., Ace and Chao1 indices) of methane-oxidizing bacteria by 21.9%-23.8%. 4) Results of the structural equation modeling showed that CH4 emissions were promoted by soil methanogen diversity, temperature and humidity, and C and N pools, but inhibited by soil methane-oxidizing bacterial diversity. The explained extents of soil temperature, humidity, carbon pool, nitrogen pool, methanogen diversity, and methane-oxidizing bacterial diversity for the CH4 emission changes were 6.9%, 21.6%, 18.4%, 15.2%, 14.0%, and 10.8%, respectively. Therefore, ant nests regulated soil CH4 emission dynamics through altering soil functional bacterial diversities, micro-habitat, and carbon and nitrogen pools in the secondary tropical forests.
