NUMERICAL SIMULATION STUDY ON THE IMPACTS OF TROPSHERE O3 AND CO2 CONCENTRATIONS CHANGES ON WINTER WHEAT: ⅠMODEL DESCRIPTION

Ozone is well documented as the air pollutant most damaging to agricultural crops and other plants. It is reported that troposphere O3 concentration has been increased rapidly in recent 20 years. Evaluating and predicting impacts of ozo ne concentration changing on crops are drawing great attention in the scientific community. In China, main study method on this field is controlled experiments, for example open top chambers, but numerical simulation study about impacts of ozone on crops using crop model is rare, what’s more, the simulation study abou t combined impacts of ozone and carbon dioxide has not been reported. The improv ed agroecosystem model is presented to evaluate simultaneous impacts of troposph ere O3 and CO 2 concentration changes on crops in the paper by integrating im pacts of ozone on crop growth and development algorithms with an existing agroec osystem biogeochemical model, DNDC. The main crop physiological process of crop grow th (phenology, leaf area index, photosynthesis, respiration, assimilate allocati on and so on) in former DNDC are kept. The algorithms about impacts of ozone on photosynthesis and winter wheat leaf are added in improved model to reveal impac ts of ozone and carbon dioxide on growth development and yield formation of wint er wheat coupling the simulation about impacts of carbon dioxide on photosynthes is of winter wheat which exists in former DNDC.In the paper, firstly assimilate allocation algorithms and some specie parameters (such as daily thermal time of different development stage) were modified in order that DNDC can be applied to North of China. Secondly two different kinds of impacts of ozone on crops algor ithms were tried to coupling with the former model the one was impacts of ozon e on light use efficiency, another was direct effects of ozone on leaves photosy nthesis. The later were closer to experiment measurements through comparing resu lts of two group simulated. At last, the method of direct impacts of ozone on le aves growth was adopted and the coefficients about impacts of ozone on leaf grow th and senescence were ascertained. Effects of climate changes, increasing ozone and carbon dioxide concentration on agroecosystem are attempted to be simulated numerically in the study which is considered to be advanced and credible.