O_3浓度升高对麦田土壤氨氧化细菌、氨氧化古菌和硝化细菌数量的影响

Effects of Elevated Ozone on Quantity of Ammonium-oxidizing Bacteria,Ammonia-oxidizing Achaea and Nitrobacteria in Wheat Field Soil

硝化作用在氮循环过程中至关重要,包括氨氧化作用和亚硝酸盐氧化作用,通过氨氧化反应和亚硝酸盐氧化反应将N素转化为植物可利用的NO3-形态。利用开顶式臭氧气室(OTCs,open-top chambers)试验平台,通过大田模拟熏气试验,结合Real-timePCR探讨大气O3浓度升高对麦田土壤氨氧化细菌(AOB)、氨氧化古菌(AOA)及硝化细菌(NOB)数量的影响。结果表明,AOB、AOA和NOB对O3胁迫的反应不一样,AOB基因拷贝数基本上随着O3浓度的升高呈现出降低的趋势,而AOA和NOB基因拷贝数随O3浓度的升高变化不明显。冬小麦拔节期,当O3浓度为40、80、120nmol·mol-1时,20～40cm土层的AOB基因拷贝数分别比对照处理降低39.8%、51.2%和59.4%。AOB和NOB基因拷贝数灌浆期多于收获期,0～10cm土层多于10～20cm。AOA基因拷贝数随季节的变化不大。O3胁迫可通过影响AOB、AOA和NOB的数量和活性来影响土壤的硝化反应,从而影响土壤的氮素循环过程。

Nitrification is of vital importance in nitrogen cycle, including ammoxidation and nitration processes. The nitrogen is transformed into NO; form which is available for the plants through the ammoxidation and nitration. The study aimed at the impact of near the surface O_3 concentration on the quantities of ammonium-oxidizing bacteria（AOB ）, ammoniumoxidizing achaea（AOA ） and nitrobacteria（NOB ） by the realtime polymerase chain reaction（PCR）, openthe top chambers（OTCs） and simulatedsmoke experiment in the field. The results showed that the responses of AOB, AOA and NOB under the stress of O3 were different. The quantity of AOB gene copies had a trend of a decrease with the increase of O3 concentration, but the quantities of AOA and NOB gene copies were not changed significantly with the increase of O3 concentration. In the jointing stage of winter wheat, whenO3 concentration were 40, 80 and 120 nmol ＂mo1-1, the quantities of AOB gene copies in 20-40 cm soil were respectively lower than the control group by 39.8%, 51.2% and 59.4%. The quantities of AOB and NOB gene copies in filling stage were more than those in the harvest time, and the quantities of AOB and NOB gene copies in 0-10 cm soil layer were more than those in 10-20 cm soil layer. The quantity of AOA gene copies had not changed significantly with the change of season. In summary, changes in the quantities and activities of AOB, AOA, NOB in response to different 03 concentrations provide a good indicator for investigating the nitrification, which can be used as indicator for the nitrogen cycling in soil.