以湖南桃源县一长期种植水稻的酸性土壤为研究对象,在微宇宙培养条件下设置了4个水分梯度处理,分别为田间持水量(water holding capacity,WHC)的30％、60％、90％和淹水2 cm 深。考察了水分条件变化对硝化和反硝化作用影响,并结合定量 PCR 和限制性末端片段长度多态性(T-RFLP)技术研究了硝化-反硝化微生物的响应特征。结果表明,30％ WHC 处理土壤无明显的硝化和反硝化作用发生,硝化作用主要发生于60％ WHC 和90％ WHC 处理土壤,90％ WHC 处理土壤硝化作用明显强于60％ WHC,并检测到明显的N2 O释放,表明该水分条件可能发生了硝化-反硝化耦合作用。淹水处理土壤氧化还原势Eh 显著低于非淹水处理土壤,无明显的硝化作用发生,但能检测到N2 O释放且释放量小于90％ WHC 处理土壤。除培养初期(7 d)外,反硝化功能基因 nirS 和 nirK,以及氨氧化细菌(AOB)amoA 基因的丰度先随着水分增加而增加,并在淹水处理中小幅下降,三者之间呈明显的正相关关系,且 AOB amoA、 nirS 和 nirK 基因丰度均在90％ WHC 处理中最高,与该处理中硝化和反硝化活性最高相一致。 T-RFLP 结果表明,培养2周后,nirS 基因为代表的反硝化微生物群落组成对水分梯度变化产生明显响应,Eh 和含水率 Cw 是影响其群落
To investigate the effect of moisture change on nitrification and denitrification and their corresponding functional microbes, an acidic paddy soil from Taoyuan, Hunan Province was selected as the study object, and soil microcosm experiment containing 4 different water holding capacity (WHC) levels (30% WHC, 60% WHC, 90% WHC, and waterlog) was set up in this study. Results showed that no active nitrification and denitrification occurred in 30% WHC treatment as there were no obvious ammonia consumption and nitrate accumulation, while nitrification was active in 60% WHC and 90% WHC treatments as indicated by the obvious accumulation of nitrate in those two treatments. Meanwhile, significant ammonia consumption and N2 O emission were only observed in 90% WHC treatment, implying that a much stronger nitrification in 90% WHC treatment than in 60% WHC treatment and the co-occurrence of nitrification and denitrification in 90% WHC treatment. In waterlog treatment, relatively lower N
