New flux based dose - response relationships for ozone for European forest tree species

To derive O3 doseeresponse relationships (DRR) for five European forest trees species and broadleaf\r\ndeciduous and needleleaf tree plant functional types (PFTs), phytotoxic O3 doses (PODy) were related to\r\nbiomass reductions. PODy was calculated using a stomatal flux model with a range of cut-off thresholds\r\n(y) indicative of varying detoxification capacities. Linear regression analysis showed that DRR for PFT and\r\nindividual tree species differed in their robustness. A simplified parameterisation of the flux model was\r\ntested and showed that for most non-Mediterranean tree species, this simplified model led to similarly\r\nrobust DRR as compared to a species- and climate region-specific parameterisation. Experimentally\r\ninduced soil water stress was not found to substantially reduce PODy, mainly due to the short duration of\r\nsoil water stress periods. This study validates the stomatal O3 flux concept and represents a step forward\r\nin predicting O3 damage to forests in a spatially and temporally varying climate