Large regional differences of soil water limitation effect on ozone induced yield loss for wheat and potato in Switzerland

摘要

The accumulated stomatal ozone (O_3) uptake over a threshold (Phytotoxic Ozone Dose POD_6), calculated by an ozone deposition model, has been shown to be the most appropriate metric to quantify negative effects of O_3 on food crops. In this study we used data of 13 sites in different regions of Switzerland with multiple years of O_3 measurements to quantify the stomatal O_3 uptake and the related yield loss of wheat and potato. Flux patterns for different years were calculated with the DO_3SE model to disentangle the influence of contrasting seasonal environmental conditions. Regional and inter-annual differences in meteorological conditions led to considerable variations in soil water conditions and the POD_6 values for wheat. Potato stomatal uptake was much less influenced by soil water and showed a more even distribution of P0D_6 values across sites and years. The estimated nationally and temporally average yield loss was 3.2 ± 1.2% for wheat and 2.4 ± 0.8% for potato, calculated based on an area weighting. It was found that soil water deficit, observed frequently in the western part of Switzerland, had a large attenuation effect on stomatal O_3 uptake by wheat and on corresponding yield losses. This highlights the importance of including soil moisture limitation in O_3 uptake modelling even in moist climatic regions. The comparison of modelled evapotranspiration with water flux measurements over a wheat field showed a reasonable agreement concerning the temporal pattern and the magnitude. But it is also concluded that the DO_3SE soil moisture module will need further testing and adaptation to improve accuracy of the model in dryer conditions.