Abstract:
Tropospheric ozone (O
3), as one of the primary atmospheric pollutants, poses a global threat to plants, causing ecological stress that severely hinders the achievement of carbon neutrality goals and significantly endangers food security. Photosynthesis is a critical physiological process and a pathway for carbon to enter terrestrial ecosystems. Previously, studies focused only on one or two vegetation types, a single environmental interaction factor, or over a short period. This study compiled 1263 observations from O
3 fumigation experiments published over the past 52 years (from January 1970 to December 2022) and conducted strict data quality control. Through meta-analysis, a comprehensive analysis was conducted on the response of the plant photosynthesis rate to O
3, revealing the impact of the vegetation type, ozone concentration (O
3), combined effects of O
3 with other environmental factors, and tree age on this response. Our meta-analysis results show that elevated O
3 significantly reduces the plant photosynthesis rate by up to 22.29%. The response of photosynthesis rates to the O
3 variation across vegetation types is as follows. Crops, shrubs, and broadleaf trees are the most sensitive, with photosynthetic rate reductions of 25.82%, 23.28%, and 22.14%, while grass and needle-leaf trees have smaller responses, decreasing by 14.51% and 6.70%, respectively. The tree photosynthesis rates increase and then decrease with rising O
3, while for crops, the rate falls first and then rises. As for the combined effects of O
3 with different environmental factors, drought, frost, elevated CO
2 concentration (CO
2), fertilization, and the simultaneous increase of CO
2 and fertilization can alleviate O
3 stress, while shading and high soil salinity will exacerbate O
3 stress when O
3 ≥ 70 ppb. Furthermore, the photosynthetic rate of tree leaves in response to O
3 intensifies with the increasing age of trees, particularly in the case of needle-leaf trees. Our findings provide an important reference for understanding the influence of O
3 pollution on the plant physiological process and carbon cycle of terrestrial ecosystems in the context of global change.