Rising Atmospheric CO2 Alleviates Drought Impact on Autumn Leaf Senescence Over Northern Mid‐High Latitudes

ABSTRACT Aim Drought reduces plant growth and hastens the process of leaf senescence in autumn. Concurrently, increasing atmospheric CO 2 concentrations likely amplifies photosynthetic activity while increasing plant water‐use efficiency. However, how drought affects the date of leaf senescence (DLS) and whether elevated CO 2 can alleviate this remain unknown. Here, we explore the effect of drought on DLS under recent climate change and explore the underlying mechanisms. Location Northern mid‐high latitudes. Time Period 2000–2019. Major Taxa Studied Plants. Methods We conducted comprehensive analyses based on satellite remote sensing, eddy covariance flux observations, in situ phenology observations and land‐surface models. Linear regression analysis and a ten‐year moving window were adapted to investigate the spatiotemporal patterns in DLS sensitivity to drought ( S dd ). The partial least squares regression method was used to attribute the main factors for the variation in S dd , and land‐surface models in different scenarios were used to verify the robustness of the results. Results Our study presented divergent spatial patterns of S dd , where the highest S dd was concentrated in dry and warm regions. Temporally, multiple datasets consistently illustrate a significant decrease in the S dd during recent decades ( p < 0.05). We also observed a nonlinear relationship between the trend of S dd and aridity gradient, which presented a slightly positive S dd trend in dry regions but a negative trend in wet regions. We found these observed changes were primarily attributed to elevated CO 2 , alleviating the drought stress on DLS in nearly 40% of the study area. Main Conclusions Our findings demonstrate the complex role that atmospheric CO 2 plays in regulating plant leaf senescence during drought stress, highlighting the need to incorporate the effects of elevated CO 2 on vegetation autumn phenology into land‐surface models for projecting vegetation growth and carbon uptake under continued global change.