Released control of vapor pressure deficit on rainfed rice evapotranspiration responses to extreme droughts in the subtropical zone

Rice production consumes more freshwater than any other crop. Rice evapotranspiration (ET) response to extreme droughts due to ongoing climate change is becoming critical in agricultural water management and national food security. Here, we aim to evaluate the impact of droughts in the subtropical zone during 2009–2011 on rainfed rice ET and to explore the underlying influencing mechanisms of dryness stress on it.

We detected the impact of drought events on rainfed rice ET using a modified Surface Energy Balance Algorithm for Land model. Additionally, we applied both multiple linear regression model and extreme gradient boosting models—Shapley additive explanations framework to fully investigate the sensitivity of rainfed rice ET to vapor pressure deficit (VPD) and soil moisture (SM).

Compared to normal conditions, the rainfed rice ET exhibited a 24.7% reduction after the “2009/2010 drought”, whereas it increased by 4.3% and 15% before and during the “2011 drought”. Both linear and non-linear regression model results revealed that rainfed rice ET is more sensitive to variations in VPD rather than SM, but the dominant control of VPD appears to be released and the limiting effect of SM strengthened with the intensification of droughts.

The rainfed rice ET is highly susceptible to water stress and can rapidly respond to changing hydroclimatic conditions even during non-drought periods. Our results highlight the susceptibility of rainfed rice ET to dryness stress and the important role of VPD and SM in analyses of drought-related impacts.