Numerical Simulation Study On The Impacts Of Changes Of Tropspheric O₃ And CO₂ Concentrations On Crops

With the rapid development of industrialization and urbanization, the increase of the tropspheric O3 and CO2 concentration at striking rates caused effects on biosphere, especially on crops. It is generally well accepted that the increase of CO2 concentration will have beneficial effects on plant productivity while ozone is reported as the air pollutant most damaging to agricultural crops and other plant. In this paper, the impacts of double levels of O3 and CO2 alone or in combination on winter wheat are to be assessed with the numerical simulation method. The adaptation of Carbon and Nitrogen Biogeochemistry in Agroecosystems Model (DNDC) to deal with impacts of changes of 03 and CO2 concentration is described in the paper. Model validation includes two parts: comparison with observation cases and sensitivity analysis.The main conclusions of the paper were listed below:1. The growth and yield of winter wheat under the condition of the CO2 concentration of 500 10-6, 700 10-6 and the current ozone concentration are simulated respectively by the model. The results are well fitted with the observed values from the OTCs experiment. The results indicate that the increase of concentration of CO2 may improve the growth of winter wheat and elevate the yield.2. The growth and yield of winter wheat under the condition of the O3 concentration of 50 10-9, 100 10-9, 200 10-9 and the current CO2 concentration are simulated respectively by the model. The simulated curves of the growths of stem, leaf and spike organs as well as leaf area index are well accounted with the observed data. The results reveal that ozone has a detrimental effect on the growth and yield of winter wheat. The impacts accelerated the process of leaf senescence and cause the loss of the yield. Under the very high concentration of ozone, the crops are affected dramatically and even dead.3. At last, by the model the possible effects of changes of air temperature and the combined effects of 03 and CO2 are estimated respectively. The results show that the double concentration of CO2 may alleviate the negative effect of 03 on biomass and yield of winter wheat. The obverse effects of CO2 are less than the adverse effects of O3 when the concentration of ozone is up to 100 10-9.