Inconsistency between process-based model and dose-response function in estimating biomass losses in Northern Hemisphere due to elevated O3

Tropospheric ozone (O3) concentrations in the Northern Hemisphere have significantly increased since the pre-industrial era, with ongoing growth driven by emissions from industrial, agricultural, and transportation activities, further exacerbated by the warming temperatures and altered atmospheric circulation patterns associated with climate change. This study compared different methodologies for estimating biomass potential losses (BPL) in forests due to elevated O3 using both concentration-based (AOT40) and flux-based (POD1) metrics. Moreover, to further assess the impact of O3 on forest health and carbon uptake across the dominant forest types in the Northern Hemisphere, we also compared BPL estimates from dose-response functions with those derived from the process-based model ORCHIDEE. Our analysis showed that deciduous forests, particularly boreal and continental types, are more sensitive to O3-induced biomass loss compared to evergreen forests. Importantly, the study also revealed significant regional differences, with Europe and North America experiencing higher BPL than Asia and North Africa. Regression analysis between BPL and Gross Primary Production anomalies indicated that the relationship between O3 exposure and forest productivity varied across forest types, with continental deciduous forests showing stronger correlations. The findings highlighted the importance of using flux-based metrics like POD1 in assessing O3 impacts and that current dose-response functions may require further validation across diverse ecological settings to propose effective forest management and conservation strategies.