The Assessment Reaserch Of The Effect Of O3to Winter Wheat Main Production Areas On The Condition Of Reduced Solar Irradiation

Recently, decreasing solar radiation caused by aerosol and increasing the surface ozone concentration have deserved attention from all governments and populations. With the decreasing of solar radiation reached the surface, the photosynthetically active radiation of plant displays a declining pattern which is to inhibit corp growth. In addition, crop yield is seriously influenced by the constantly increase of O3concentration, which will threaten the food security in China. Therefore, based on the open-top chamber (OTC) field experiment, we conducted three experimental treatments in this this paper: which are the group of100±9nL·L-1fumigation of O3combined with60%±5%solar radiation weakened (T1), the group of100±9nL-L"1fumigation of O3combined with20%±5%solar radiation weakened (T2) and the group of100Q9nL·L-1fumigation of O3combined with0%±5%solar radiation weakened (CK), respectively. Thus, the stomatal conductance of winter wheat on the condition of the decreasing of solar radiation was analyzed by a revised Jarvis model and O3flux model with a mesoscale numerical model, WRF V3.2, and an air quality model, Model-3/CMAQ. Finally, it is established that the evaluation system of stress effects of O3over the main winter wheat producing areas with solar radiation weakened that will provide a theoretical reference for examining the risk of O3pollution under the background of climate change in the future. The results are showed as follows.(1). Field environment factors are all influenced by solar radiation reduced60%and20%and, the average values of vapour pressure, temperature and humidity from8:00am and16:00pm are reduced5.6℃,4.1℃,0.84kPa,0.74kPa and8.5%,7.2%respectily compared with natural solar radiation. Thus, two scenes, daily average and8hours (8-16) average, are established.(2).The daily stomata conductance presents a single-peak type with O3 influenced under solar radiation reduced. And so-called nap phenomenon is denoted clearly as twin peaks type. It obviously demonstrated that there is a cooperative phenomenon between solar radiation and O3. And we also find that the stomatal conductance under radiation60%weaken was decreased24%-64%significantly compared to CK treatment (p<0.05) in four growth period and16%～26%lower than radiation weaken20%with non-significant. In addition, Under radiation weaken20%, stomatal conductance of winter wheat is clearly decreased21%～53%(p<0.05) at jointing stage and heading stage and decreased8%～12%at flowering stage and filling stage with non-significant.(3).Based on the boundary line technology, the parameters of winter wheat stomatal conductance model were improved with VPD critical value less than other experimental results. And it is interesting to find that the most appropriate T and lowest T were all larger than other experimental results. The parameters of PAR and PHEN, however, were similar to the other experimental results.(4).To response to observed values, stomatal conductance simulated is detected at four growth stages. And their relationship were established as the function that is Y=0.94X+0.0094(R2=0.88). It showed that the model was well simulated.(5).In the whole O3exploded period, the O3cumulated absorb flux under60%,20%and0%solar radiation reduced were14.92,15.52,16.23mmol O3/m2, respectively. And the relationships between accumulated O3absorb flux and winter wheat dry matter accumulation under60%and20%solar radiation weakened are y=1.0-0.038x and y=1.0-0.022x,separately. Therefore, the dry matter is to loss38.0%and22.0%under60%and20%solar radiation reduced when O3absorb flux is increased10mmol O3/m2.(6).Nearly50%and20%dry matter and53%and32%yield of winter wheat losed under solar radiation reduced60%and20%combined O3stress compared to natural condition.