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Variation of ozone concentration of winter wheat field and mechanistic analysis of its possible effect on wheat yield in Northwest-Shandong Plain of China

Keywords: cropland ecosystem,Northwest-Shandong Plain,ozone concentration,ozone pollution indexes,winter wheat yield

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Aims High near-surface ozone (O3) has adverse effects on crop growth and yield.Our objective was to analyze the potential impact of O3 concentration on winter wheat yield,the magnitude and change characteristic of O3 concentration over a winter wheat field and the relationship between CO2 flux and O3 concentration.Methods The research site was a winter wheat field at the Yucheng Experimental Station (Shandong Province) of the Chinese Academy of Sciences.We observed O3 concentration with a portable ozone analyzer.We simulta-neously measured micrometeorological and radiation factors such as air temperature,humidity,wind speed and global and net radiation.All data were recorded with a high frequency data-logger and averaged every 30 min.Important findings There was a diurnal change pattern in O3 concentration,with low and high mean O3 concen-trations at about 7:00 and 16:00,respectively.Mean O3 concentration was (30.4 ± 20.1) nL·L-1 (mean ± SE),and the maximum of the 30 min-averaged O3 concentration was 93.1 nL·L-1.During wheat spring growing season (1 March to 31 May,2011),mean O3 concentration increased 0.17 nL·L-1·d-1.Daytime 7-hour and 12-hour mean O3 concentration (M7 and M12) were 45.7 and 43.1 nL·L-1,respectively.Accumulated O3 concentration above the threshold of 40 nL·L-1 (AOT40) was 9.8 μL·L-1·h.Accumulated O3 concentration above 60 nL·L-1 (SUM06) was 12.6 μL·L-1·h.Weight-corrected O3 concentration accumulation (W126) was 10.1 μL·L-1·h.When O3 concentra-tion is high (i.e.,>60 nL·L-1),there is an inverse relationship between CO2 flux and O3 concentration.It implied that the threshold of O3 concentration should be about 60 nL·L-1,which is higher than the 40 nL·L-1 threshold widely applied by European scientists.By using yield-response models to O3 concentration obtained in open-top chambers (OTC) by European and USA scientists,winter wheat yield is potentially decreased about 5.2%-8.8% at the current O3 level in Northwest-Shandong Plain.


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