Modelling inclusion, testing and benchmarking of the impacts of ozone pollution on crop yields at regional levelModule development and testing and benchmarking with the WOFOST generic crop model

摘要

The WOFOST crop model -as implemented in the BioMA modelling framework- was extended with algorithms to account for the effects of ground-level ozone on crop growth and yield. The additional algorithms implemented concern:•Effect of water stress on stomatal conductance•Reduction of carboxylation rate of Rubisco•Ability of plants to partly recover from ozone damage•Acceleration of leaf senesce due to O3 exposureMeteorological datasets, with a consistent hourly-daily temporal resolution, were selected for two locations in Germany (Bremen) and Spain (Jerez), encompassing different climatic conditions. The sensitivity of two types of crops was assessed: wheat, which is relatively sensitive to O3 damage, and barley, which is less sensitive. These two crops were exposed to a range of hypothetical O3 mixing ratios of 20, 40, and 60 ppb during the entire crop growth cycle, as well as during specific months. Two agro-managements options were analysed: a potential yield case (i.e. no water stress by mimicking a full crop irrigation case), and a rain-fed case. Irrespective of ozone, rainfed wheat and barley yields are lower by only 12 % in Bremen compared to fully irrigated crops, while strongly reduced by 55 % in Jerez. Additionally, wheat yield losses, up to 30 % are calculated for ozone concentrations of 60 ppb, and only half of these for barley. Yield losses are substantially smaller in Jerez for rain-fed crops, when stomatal closure is limiting gas exchange, and thus impeding photosynthesis, crop growth and yields, but also reducing ozone uptake. General findings are: •Crop damages due to O3 exposure increase with O3 concentration •Effects of high O3 concentrations are very heterogeneous depending on month, site, crop and the simulated variable considered•The highest impact is obtained when the month with high O3 concentration coincides with the anthesis/grain filling stage (June for Bremen, April for Jerez) •Rain-fed crop damage is more marked in Bremen than Jerez and irrigation practice exacerbates O3 damages, especially in Jerez •Barley is less affected by O3 impact according to the lower sensitivity of the crop.The algorithms developed can easily be implemented in other (generic or crop-specific) models of similar complexity. Compare model results against field data under diverse conditions will be the next phase of this work, and further model developments are needed to simulate so-called “stomatal sluggishness” (i.e. damage to the stomata due to ozone).