The possible consequences of climate change on carbon and nitrogen budgets of winter wheat were examined by means of model predictions. Biomass, nitrogen, water and heat dynamics were simulated for long-term climatic conditions in central and southern Sweden for a clay soil and a sandy soil. The effects of elevated atmospheric CO2 and changed climate as predicted for 2050 were simulated daily with two linked process orientated models for soil and plant (SOIL/SOILN). The models had previously been calibrated against several variables at the sites under present conditions, and the long-term predictions at present climate were shown to correspond reasonably well with measured soil C and N trends in long-term experiments. The climate and CO2 conditions for the year 2050 were represented by climatic scenarios from a global climate model, and the elevated atmospheric CO2 concentration was assumed to change plant parameter values in accordance with literature data. For the year 2050, winter wheat production was predicted to increase by 10-20% (depending on soil type) compared with the present value. Plant N concentration decreased although N mineralisation increased by 18%. Drainage was predicted to increase which resulted in increased N leaching by 17%, and the decrease in soil C became larger. The predictions were found to be most sensitive to assumptions concerning changes of radiation use efficiency, stomatal conductance, air temperature and precipitation. Hence, the load of N and C to surrounding ecosystems and the atmosphere, on a ground surface basis, was predicted to increase under climate change. However, because the harvest will increase, these negative effects of climate change on a yield basis will be almost zero, except that N leaching from the sandy soil will still increase. (C) 2001 Elsevier Science B.V. All rights reserved.
