Modelling C, N, water and heat dynamics in winter wheat under climate change in southern Sweden

The possible consequences of climate change on carbon and nitrogen budgets of winter wheat were examined by means of model predictions. Biomass, nitro gen, water and heat dynamics were simulated for long-term climatic conditio ns in central and southern Sweden for a clay soil and a sandy soil. The eff ects 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 seve ral variables at the sites under present conditions, and the long-term pred ictions at present climate were shown to correspond reasonably well with me asured soil C and N trends in long-term experiments. The climate and CO2 co nditions for the year 2050 were represented by climatic scenarios from a gl obal climate model, and the elevated atmospheric CO2 concentration was assu med 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 conce ntration decreased although N mineralisation increased by 18%. Drainage was predicted to increase which resulted in increased N leaching by 17%, and t he decrease in soil C became larger. The predictions were found to be most sensitive to assumptions concerning changes of radiation use efficiency, st omatal conductance, air temperature and precipitation. Hence, the load of N and C to surrounding ecosystems and the atmosphere, on a ground surface ba sis, was predicted to increase under climate change. However, because the h arvest will increase, these negative effects of climate change on a yield b asis will be almost zero, except that N leaching from the sandy soil will s till increase. (C) 2001 Elsevier Science B.V. All rights reserved.