Significant changes in global maize yield sensitivity to vapor pressure deficit during 1983–2010

Vapor pressure deficit (VPD) is a critical factor in crop growth, and low yields are often associated with high VPD. The adverse effects of VPD on crop yield have been well-documented; however, whether and where yield sensitivity to VPD (SVPD) changes over time across global cropping areas remain elusive. Based on the observed maize yield and VPD at the grid scale, the SVPD calculated using least-squares linear regression for 27.5 % and 25.9 % of the global maize-growing areas, respectively, showed a significant (p < 0.05) decreasing and increasing trend from 1983 to 2010. Spatially, a statistically negative trend in SVPD was found in southeastern Brazil, the central United States, most of Europe, and northeastern China, whereas a positive trend was observed in the eastern United States and northern China. In particular, negative SVPD was alleviated in 23.2 % of global maize areas, primarily in the northeastern United States and northern China, but was aggravated in 18.4 % of maize areas in the middle latitudes of the Northern Hemisphere. In addition, the sign of SVPD was reversed in 34.4 % of the global maize areas, notably in the central United States, northern China, and southern Brazil. The results of the random forest model show that shortwave radiation was identified as the primary co-varying factor that modulated the pattern of changing SVPD in about 26 % of the global maize area, followed by maximum temperature (24.3 %) and minimum relative humidity (21.5 %). By assessing the 14 process-based crop models, we found that their ensemble mean could reproduce the annual patterns of SVPD well but failed to capture its decadal change trends.