CO2 Fertilization Effect Offset the Vegetation GPP Losses of Woodland Ecosystems Due to Surface O3 Damage in China

Air pollution and climate change are a growing threat to terrestrial woodland ecosystems. Extensive research in China has focused on single environmental factors, such as ozone, carbon dioxide, and climate change, but the multifactor interactions are poorly known. Here, we coupled the interactions of climate change, elevated CO2 concentration, and increasing O3 into the BEPS_O3 model. The GPP simulated by the BEPS_O3 is verified at site scale by using the eddy covariance (EC) derived GPP data in China. We then investigated the impact of ozone and CO2 fertilization on woodland ecosystem gross primary production（GPP） in the context of climate change during 2001-2020 over China. The results of multi-scenario simulations indicate that the GPP of woodland ecosystems will increase by 1-5% due to elevated CO2. However, increased ozone pollution will result in a GPP loss of approximately 8-9%. In the historical climate, under the combined effects of CO2 and O3, the effect of ozone on GPP will be mitigated by CO2 to 4-7%. In most areas, the effect of ozone on woodland ecosystems is higher than that of CO2 on vegetation photosynthesis, but CO2 gradually counteracts the effect of ozone on the ecosystem. Our simulation study provides a new way of thinking about assessing the interactive responses to climate change, and advances our understanding of the interactions of global change agents over time. In addition, the comparison of individual and combined models will provide an important basis for national emission reduction strategies as well as O3 regulation and climate adaptation in different regions.