Tropospheric ozone alters solar-induced chlorophyll fluorescence (SIF) and its relationship with gross primary production (GPP) in a subtropical evergreen forest

Solar-induced chlorophyll fluorescence (SIF) offers a novel approach to study how plants respond to stress, yet the extent and mechanism by which SIF reflects vegetation changes under varying ambient O3 remain unclear. Using continuous and simultaneous observations of O3, SIF, and carbon fluxes in a subtropical evergreen forest, we investigated the response of canopy SIF to ambient O3 exposure and explored the underlying mechanisms of vegetation's response to O3. Our findings reveal that high ambient O3 alters both the canopy SIF and its relationship with GPP in the subtropical evergreen forest, but the mechanisms of the effects are different in the dry and wet seasons. These findings highlight the ability of SIF for plant O3 stress detection and the different responses of structure and physiology under varying water conditions, which could effectively advance our understanding of plant O3 stress mechanisms across different climates.