Redefine droughts in the U.S. Corn Belt

Our story

About the


To disentangle contributions of high atmospheric water demand (i.e., high vapor pressure deficit (VPD)) and low soil water supply (i.e., soil water content – SWC) on stomatal conductance (Gs) implying impacts on crop productivity during drought conditions throughout Illinois and the U.S. Corn Belt.


The dominant contribution to variability in crop stomatal regulation (decrease in Gs) during droughts in the US Midwest agroecosystems is mostly due to dry air (high VPD) rather than dry soil (low SWC).


This study improves our understanding of the mechanisms of crop response to drought for the US Midwest agroecosystems. The outcomes of this study can improve the modeling capability of crop stress under drought conditions. The study also provides information to crop breeders on what specific traits should be enhanced to obtain drought-tolerant genotypes.


Meteorology data and exchange rate of CO2 and H2O at the atmosphere and plant canopy landscape interface from Eddy-covariance network sites (http://ameriflux.lbl.gov/).


Relationships among VPD, SWC, and Gs are evaluated hourly, daily, and weekly time intervals and fitted a multiple linear regression model and a non-linear model. To attribute the variability in Gs to VPD and SWC, numerically calculated partial derivatives and ANOVA-derived partial contributions are obtained. PATH analysis is conducted to understand the underlying processes.

Preliminary Results

 VPD and SWC are highly correlated at longer timescale, so to decouple their contributions, the data are analyzed at a daily timescale. Based on the current results, we find that dry air (high VPD) is found to have a higher impact on stomatal conductance (Gs) variability compared to dry soil (low SWC), which supports our hypothesis. Further study is ongoing to understand the specific underlying processes.