Effect Of Elevated O₃in Tropospheric On The Microelements In Paddy Field Ecosystem

In recent decades, due to the activity of human, the O3concentration in tropospheric has been increasing at a rate of about0.3%-2%per year, and doubled the past century。The increasing of O3concentration has impacted the structure of farmland’s ecosystem. A lot of studies show that elevated O3could reduce rice yield, photosynthetic, biomass, etc. It could also affect soil respiration, mineralization and so on. However the studies about the effects of atmospheric elevated O3on the microelements in paddy field ecosystem are reported rarely. By using the O3-FACE (Ozone-Free Air Concentration Enrichment) system in2009rice season, the effect of elevated O3(target at50%above ambient) on the microelements in paddy field ecosystem were studied, after a rotation of rice and wheat. Results showed as follows:1. Elevated O3significantly affected the concentrations of DTPA-extractable microelements in paddy soil, which were different with growth stage and soil depth. Elevated O3has increased the concentrations of DTPA-extractable Fe, Mn and Cu, but reduced DTPA-extractable Zn.2. Elevated O3increased the concentrations of Fe, Mn and Zn of the soil solution in5cm depth, while reduced the concentrations of Fe, Mn and Zn in15cm depth. But all of the effects are not significant.3. Elevated O3had the trend of decreasing the concentrations of microelements in rice straw and the rice panicle. And the level of Mn and Cu concentrations’reducing in rice straw was significant at jointing stage.4. Elevated O3has decreased the dry matter accumulation of rice straw and rice production。 During the crop growth, the microelements accumulation of rice straw tended to increase. Elevated O3has decreased the accumulation of microelements in rice straw and rice panicle. Results from this study indicated that, elevated O3in tropospheric could affect the rice production and the ecological environment by changing paddy fields ecosystem. Therefore, studying the respond of the microelements in paddy field ecosystem to O3enrichment in tropospheric is positive to the protection of agricultural environment and improving grain production efficiency in future atmospheric background.