作 者 ：陈展,王效科,段晓男,冯兆忠,吴庆标
期 刊 ：生态学报 2007年 27卷 5期 页码：1803~1808
关键词：臭氧；根系；土壤微生物；微生物碳；多样性指数；丰富度指数；BIOLOG；
Keywords:ozone, root, soil microorganism, microbial biomass, microbial diversity, BIOLOG,
摘 要 ：拟研究了臭氧浓度升高（日变化熏蒸方式）对小麦根系和土壤微生物活性的影响。实验分3个处理，即空气对照（CF，臭氧浓度约4~10nl•L-1），臭氧浓度Ⅰ（OⅠ，8h平均75 nl•L-1），臭氧浓度Ⅱ（OⅡ，8h平均110 nl•L-1）。结果表明，臭氧浓度升高后小麦茎叶、根系生物量以及根冠比都会降低，根系活力更是显著低于空气对照，可见臭氧对植物地下部分的影响是显著的。与对照相比，低浓度O3（75 nl•L-1）对根际土和非根际土的微生物生物量碳没有什么影响；而较高的O3浓度（110 nl•L-1）会造成根际土微生物生物量碳降低9.3%，非根际土微生物生物量碳降低5.3%，说明高浓度臭氧抑制土壤微生物的量。臭氧浓度升高后小麦根际土壤微生物利用单一碳源的能力（AWCD）都明显低于对照；低浓度的臭氧对土壤微生物的多样性指数和丰富度指数都没有显著影响，而浓度较高的臭氧则显著降低了根际土微生物的多样性指数，而对丰富度指数没有显著影响，且也没有发现O3浓度升高对非根际土微生物的影响。可见，臭氧主要影响根际土壤微生物而对非根际土壤微生物影响不大，且只有在高浓度的臭氧处理下才会显著降低根际土壤微生物的多样性指数。
Abstract:Ozone (03) is considered to be a major air pollutant that affects the yields of several sensitive crop species while reducing carbon acquisition by plants and the subsequent allocation of carbon to roots. Ozone concentrations have dramatically increased in some parts of China. Despite the emphasis on research in this area, however, little has been done to study below-ground component responses when shoots are exposed to ozone, even though evidence suggests that ozone can affect roots more than shoots. Since ozone can not penetrate soil, effects on the below-ground system are the indirect results of altered plant processes. Most current research focuses on constant ozone concentrations that are not in accordance with ambient ozone daily changes. This study is therefore initiated to explore the dynamic Ozone exposure effects on potted wheat roots and soil microorganisms, which can better demonstrate the below-ground response to natural dynamic ambient ozone. Three treatments were performed in this study: (1) control regime: very low ozone with a daily average of 4-10 nl•L-1 (CF); (2) ozone exposure regime: I (OI), low ozone with an 8h average of 75 nl•L-1; and (3) ozone exposure regime: II (OII), high ozone with an 8h mean 110nl•L-1. Wheat seedlings were grown either in a water-hydroponic system for root analysis or in soil for soil microbial analysis and exposed to ozone for 75days in a series of replicated experiments. In both of the two environments with ozone exposure, the root biomass and root/shoot ratio are reduced by 18% and 7.7%, respectively, compared to the control treatment. Effects on root activity were also examined as this parameter is an important indicator of wheat’s ability to absorb nutrients. The results show that root activity is significantly reduced by 58% for the low ozone regime and by 90.8% for the high ozone regime. We also studied the effects of ozone on rhizosphere and nonrhizosphere soil microorganisms. It is demonstrated that low ozone (OI) concentrations can appreciably increase microbial carbon, while high ozone (OII) concentrations cause rhizosphere and nonrhizosphere soil microbial biomass carbon to decrease by 9.3% and 5.3%, respectively, compared to the control treatment. Microbial diversity was studied using sole-carbon-source-utilization (BIOLOG). In the BIOLOG assays, the average well color development (AWCD) and the richness and diversity indices indicate differences in microbial activity and diversity. The AWCD and both of the indices for rhizosphere soil microorganisms are higher than those in nonrhizosphere soil both in the control and ozone treatments. Ozone largely reduces the AWCD of rhizosphere soil microorganisms, while it has little influence on the nonrhizosphere soil microbial AWCD. The richness and diversity indices of both the rhizosphere and nonrhizosphere soil microorganisms in ozone exposure regime I have no difference compared to the control regime. While ozone exposure regime II remarkably decreases the diversity index in rhizosphere soil microorganisms, it does not have such an effect in nonrhizosphere soil. Although rhizosphere soil microorganisms can be considered more susceptible to ozone than nonrhizosphere soil microorganisms, this may actually be due to the indirect effects of ozone via the reduction of carbon allocation to roots. As a result, root exudation is decreased, forming the carbon and energy sources of rhizosphere soil microorganisms.