不同温度下尿素对水稻土甲烷产生及相关古菌群落的影响

Effect of Urea Fertilizer on Methane Production and Methanogenic Archaeal Community Structure in Paddy Soil at Different Temperatures

水稻田是大气甲烷的重要排放源。尿素氮肥施用是提升水稻产量和品质的重要措施,但其对稻田土壤中产甲烷古菌的影响规律仍不清楚。通过模拟水稻生长季节可能的田间温度变化,本研究设置水稻土施加尿素(N,400 mg/kg干土)与未施加尿素两个处理,在15℃、25℃、37℃以及50℃下进行为期100天的厌氧培养,定期测定了培养过程中甲烷累积量以及土壤理化因子如p H、NH_4^+-N以及有机碳的变化,并运用基于16S r RNA基因的T-RFLP(末端限制性片段多态性分析)技术分析了产甲烷过程中古菌群落结构随时间的变化情况。结果表明:在中低温范围内(15~37℃),尿素对水稻土产甲烷有抑制作用,但在50℃高温下尿素对水稻土产甲烷量没有显著影响。尿素可能通过改变产甲烷古菌群落结构来影响甲烷的产生,在15~37℃范围内,尿素降低了水稻土产甲烷古菌群落的稳定性,增大了其在不同时间的差异性;而在50℃高温时,尿素对水稻土产甲烷古菌稳定性和差异性的影响不明显。不同温度下,尿素均降低了甲烷八叠球菌(Methanosarcinaceae)的丰度,且随着温度的变化,尿素对水稻土产甲烷机制的改变可能没有影响。

As the second largest greenhouse gas, methane production and emission have great effect on global warming and carbon cycle in the ecosystem. Paddy soil is one of the main sources of atmospheric methane. Urea fertilizer which affects yield and quality of rice plays an important role in regulation methane emission flux. In order to study the effect of urea fertilizer on methane production and methanogenic archaeal community structure at different temperatures, the neutral paddy soils were incubated under anaerobic condition with urea of 0 and N 400 mg/kg at 15℃, 25℃, 37℃ and 50℃ for 100 days. The cumulant of methane-production and soil characteristics such as pH, organic carbon and nitrogen of ammonium were detected during the incubation. The shifts of methanogenic archaeal community structure with incubation time in different treatments were analyzed by terminal restriction fragment length polymorphism （T-RFLP） analysis based on archaeal 16S ribosomal RNA gene. The results showed that urea fertilizer inhibited methane production in paddy soil at low or medium temperature （15 ℃- 37℃）, while had no effect on the accumulated methane production at high temperature （50℃）. Urea may influence methane production by altering the community structure of methane-producing archaea. Urea fertilizer decreased the stability and increased the diversity of methanogenic archaeal community structure with incubation time in the range from 15℃ to 37℃. But there was unconspicuous influence of urea fertilizer on methanogenic archaeal community structure at 50℃. The result of T-RFLP indicated that urea reduced the relative abundance of Methanosarcinaceae under these four experimental temperatures. Urea prossibly had nothing to do with the changes of methane-producing mechanism as temperature changed.