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.
探明蚂蚁巢穴对热带次生林土壤甲烷排放的影响过程及机理,对于理解土壤动物活动对温室气体排放的贡献具有重要科学意义。以西双版纳高檐蒲桃热带次生林群落为研究样地,采用静态箱-气相色谱法测定蚁巢与非蚁巢土壤甲烷排放干湿季动态,探讨蚂蚁巢穴引起土壤功能微生物多样性及理化性质的变化对甲烷排放的影响机制。结果表明: 1)蚂蚁巢穴显著促进土壤甲烷的排放,蚁巢排放量是非蚁巢土壤的2.6倍。2)蚁巢与非蚁巢土壤甲烷排放通量具有显著的干湿季变化,干季为碳汇,其通量变幅为(-0.29±0.03)～(-0.53±0.02) μg·m-2·h-1;湿季为碳源(0.098±0.02)～(0.041±0.009) μg·m-2·h-1;蚁巢甲烷通量均大于非巢地,蚁巢干湿季变幅(-0.38± 0.01)～(0.12±0.02) μg·m-2·h-1小于非巢地(-0.65±0.04)～(0.058±0.006) μg·m-2·h-1。3)蚂蚁巢穴显著促进土壤产甲烷菌多样性(Ace和Shannon指数)、温湿度、碳库(有机碳、易氧化碳和微生物生物量碳)和氮库(全氮、水解氮、铵态氮和微生物生物量氮)组分的增加(增幅为6.2%～37.8%),蚂蚁巢穴却引起土壤甲烷氧化菌多样性(Ace和Chao1指数)的减少(减幅为21.9%～23.8%)。4)结构方程表明:土壤温度、湿度、碳库、氮库、产甲烷菌多样性显著促进土壤甲烷排放,分别解释了6.9%、21.6.%、18.4%、15.2%和14.0%的通量变化;甲烷氧化菌多样性的变化对甲烷排放具有抑制作用,解释10.8%的通量变化。因此,蚂蚁巢穴的存在引起了土壤功能细菌多样性、微气候和碳氮库的改变,进而影响热带次生林甲烷排放。.
Keywords: CH 4 emission; Xishuangbanna; ant nest; methane-oxidizing bacteria; methanogen; tropical forest.