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

Aim

Drought reduces plant growth and hastens the process of leaf senescence in autumn. Concurrently, increasing atmospheric CO₂ concentrations likely amplifies photosynthetic activity while increasing plant water-use efficiency. However, how drought affects the date of leaf senescence (DLS) and whether elevated CO₂ 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 CO₂, alleviating the drought stress on DLS in nearly 40% of the study area.

Main Conclusions

Our findings demonstrate the complex role that atmospheric CO₂ plays in regulating plant leaf senescence during drought stress, highlighting the need to incorporate the effects of elevated CO₂ on vegetation autumn phenology into land-surface models for projecting vegetation growth and carbon uptake under continued global change.