Influence of Elevated O_3 and Different Wheat Cultivars on Soil Enzymes Involving in Nitrogen Transformation

CHEN Wei;HUANGFU Qian-hua;SUN Cong-jian;ZHANG Li-li;WU Zhi-jie;Institute of Applied Ecology, Chinese Academy of Sciences;School of Geographical Science, Shanxi Normal University;

Free-air ozone enrichment(FAOE);;Enzymes activities;;Different wheat cultivars;;Split plot analysis

Taking rhizosphere soil from two different wheat(Triticum aestivum L.) cultivars Yannong 19(ozone sensitive) and Yangmai 16(ozone relatively sensitive) as tested materials, this paper studied the enzymes activities involving in nitrogen transformation through free-air ozone enrichment(FAOE) system. The results showed that under elevated ozone(eO_3) concentration, protease activity had no significant change, while urease activity increased by4.01% at O_3 sensitive wheat rhizosphere soil, ammonium oxidase activity increased significantly at O_3 sensitive and relatively sensitive cultivars by 19.38% and 203.66%, respectively. In accord with urease and ammonium oxidase, soil NH_4~+ and NO_3~-increased significantly but microbial biomass nitrogen(MBN) decreased. The activities of nitrate reductase and nitrite reductase decreased and increased, respectively. Redundancy analysis(RDA) showed that total nitrogen, O_3 and pH were the most important factors to influence the activities of five enzymes. Our results indicated that under elevated O_3, nitrogen cycling at wheat rihzosphere soil could be altered because of changed enzymes activities. These changes may increase the risk of nitrogen loss through ammonia volatilization and nitrate leaching, and this phenomenon was more obvious at O_3 sensitive wheat cultivar.