Leaf-cutter ant nests are biogeochemical hot spots where ants live and import vegetation to grow fungus. Metabolic activity and (in wet tropical forests) soil gas flux to the nest may result in high nest CO2 concentrations if not adequately ventilated. Wind-driven ventilation mitigates high CO2 concentrations in grasslands, but little is known about exchange for forest species faced with prolonged windless conditions. We studied Atta cephalotes nests located under dense canopy (leaf area index > 5) in a wet tropical rainforest in Costa Rica, where wind events are infrequent. We instrumented nests with thermocouples and flow-through CO2 sensing chambers. The results showed that CO2 concentrations exiting leaf-cutter ant nests follow a diel pattern with higher values at night. We developed an efflux model based on pressure differences that evaluated the observed CO2 diel pattern in terms of ventilation by (1) free convection (warm, less dense air rises out the nest more prominently at night) and (2) episodic wind-forced convection events providing occasional supplemental ventilation during daytime. Average greenhouse gas emissions were estimated through nest vents at about 78 kg CO2eq nest-1 year-1. At the ecosystem level, leaf-cutter ant nest vents accounted for 0.2% to 1% of total rainforest soil emissions. In wet, clayey tropical soils, leaf-cutter ant nests act as free convection-driven conduits for exporting CO2 and other greenhouse gases produced within the nest (fungus and ant respiration, refuse decay), and by roots and soil microbes surrounding the nest. This allows A. cephalotes nests to be ventilated without reliable wind conditions.

中文翻译：

---

自由对流驱动的Diel模式控制了新热带雨林中的切叶蚁巢通风和温室气体排放。

切叶蚁巢是生物地球化学的热点，蚂蚁在那里生活并输入植物来生长真菌。如果通风不充分，代谢活动和（在热带潮湿森林中）土壤气体通向巢穴可能会导致巢内较高的二氧化碳浓度。风驱动的通风减轻了草原上高的CO2浓度，但对于长期无风条件下的森林物种交换却知之甚少。我们研究了哥斯达黎加湿润的热带雨林中茂密的树冠下（叶面积指数> 5）的Atta头足类鸟巢，那里很少发生风灾事件。我们使用热电偶和流通式CO2传感腔室对巢进行了检测。结果表明，离开切叶蚁巢的CO2浓度呈迪尔模式，夜间浓度较高。我们基于压力差开发了外排模型，该模型通过以下方面评估了通风方面的观测到的CO2 diel模式：（1）自由对流（温暖，密度较小的空气在晚上更明显地从巢穴中冒出）和（2）阵风强迫对流白天偶尔提供补充通风的活动。通过鸟巢通风口估计的平均温室气体排放量为第1年第1年巢巢约78千克二氧化碳当量。在生态系统层面，切叶蚁巢穴排放口占雨林土壤总排放量的0.2％至1％。在潮湿，黏稠的热带土壤中，切叶蚁巢充当对流驱动的自由管道，用于输出巢内产生的CO2和其他温室气体（真菌和蚂蚁呼吸，垃圾腐烂）以及巢穴周围的根和土壤微生物。这允许A。