中文摘要：

利用臭氧FACE（free-air O3concentration enrichment,开放式空气臭氧浓度增高）试验平台,研究近地层臭氧浓度（臭氧摩尔分数平均为70 nmol·mol^-1）升高对小麦不同生育期植株氮吸收量,土壤w（全氮）、w（矿质氮）、脲酶活性、氨氧化细菌数量、反硝化细菌数量以及小麦成熟期土壤硝化与反硝化作用强度的影响。结果表明,与对照（臭氧摩尔分数平均为45 nmol·mol^-1）相比,臭氧浓度升高条件下小麦不同生育期氮吸收量总体趋于升高,土壤w（全氮）、w（铵态氮）和w（硝态氮）总体趋于下降,在小麦成熟期土壤w（全氮）和w（铵态氮）分别比对照下降9%和71%（P〈0.05）,而w（硝态氮）比对照下降36%;臭氧浓度升高使小麦不同生育期土壤脲酶活性总体趋于增强,在拔节期、抽穗期和灌浆期均显著高于对照（P〈0.05）;随着小麦的生长,臭氧熏蒸土壤氨氧化细菌和反硝化细菌数量也趋于升高,在小麦成熟期均显著高于对照（P〈0.05）。在小麦成熟期,尽管臭氧熏蒸土壤单个氨氧化细菌的硝化活性比对照下降57%,但土壤整体硝化强度却比对照提高123%;臭氧熏蒸土壤反硝化作用强度与对照相比无明显差异,但单个反硝化细菌的反硝化活性却比对照降低96%,达显著水平（P〈0.05）。认为臭氧浓度升高促进了小麦对土壤氮素的吸收,导致土壤氮素库存量降低,进而加快了土壤中氮素的转化,表现为脲酶活性升高,氨氧化细菌和反硝化细菌数量增加,但它们的代谢活性反而下降。

英文摘要：

An O3-FACE（free-air O3 concentration enrichment） system was set up in a wheat field to investigate effects of elevated surface O3 concentration,which was 70 nmol·mol^-1 on average,on wheat N-uptake,soil total N and mineral N,urease activity,and populations of ammonia-oxidizing bacteria（AOB） and denitrifying bacteria（DNB） at various wheat growth stages,as well as soil nitrification and denitrification potentials at the wheat harvesting stage.Compared with the ambient O3concentration,which was 45 nmol·mol^-1,elevated O3 concentration increased individual wheat N-uptake,while decreased soil total N,NH＋4-N and NO-3-N contents.At the wheat harvesting stage,soil total N and NH4^＋-N contents decreased significantly（P〈0.05） by 9% and 71%,respectively,and so did soil NO3^--N content by 36%.During the growth periods of wheat,elevated O3 concentration tended to enhance soil urease activity,which was significantly（P〈0.05） higher than that in the ambient soil at the jointing,heading and filling stages of wheat,and to increase the population of soil AOB and DNB,as well,which were significantly（P〈0.05） higher than those in the ambient soil at the wheat harvesting stage.At that time,although in O3-fumigated soils the specific nitrification potential of AOB tended to decrease,and the soil total nitrification potential to increase,while the specific denitrification potential of DNB decreased significantly（P〈0.05） by 96% and the soil total denitrification potential remained unchanged,which suggests that elevated surface O3 concentration promoted wheat N-uptake,inhibited soil N storage,and then accelerated soil N transformation,which was represented by enhanced urease activity,and bigger population sizes of soil AOB and DNB with low metabolic activity.