How accurately do maize crop models simulate the interactions of atmospheric CO2 concentration levels with limited water supply on water use and yield?

Abstract

This study assesses the ability of 21 crop models to capture the impact of elevated CO2 concentration ([CO2]) on maize yield and water use as measured in a 2-year Free Air Carbon dioxide Enrichment experiment conducted at the Thünen Institute in Braunschweig, Germany (Manderscheid et al., 2014). Data for ambient [CO2] and irrigated treatments were provided to the 21 models for calibrating plant traits, including weather, soil and management data as well as yield, grain number, above ground biomass, leaf area index, nitrogen concentration in biomass and grain, water use and soil water content. Models differed in their representation of carbon assimilation and evapotranspiration processes. The models reproduced the absence of yield response to elevated [CO2] under well-watered conditions, as well as the impact of water deficit at ambient [CO2], with 50% of models within a range of +/−1 Mg ha−1 around the mean. The bias of the median of the 21 models was less than 1 Mg ha−1. However under water deficit in one of the two years, the models captured only 30% of the exceptionally high [CO2] enhancement on yield observed. Furthermore the ensemble of models was unable to simulate the very low soil water content at anthesis and the increase of soil water and grain number brought about by the elevated [CO2] under dry conditions. Overall, we found models with explicit stomatal control on transpiration tended to perform better. Our results highlight the need for model improvement with respect to simulating transpirational water use and its impact on water status during the kernel-set phase

Response of maize biomass and soil water fluxes on elevated CO2 and drought—From field experiments to process‐based simulations

“…An accurate simulation of the transpiration is important, since an underestimated reduction in transpiration hampers the maize model to simulate a strong biomass increase under eCO 2 (Durand et al, 2017). The reduction of transpiration could be approved; however, a simulated increase in soil moisture was not found above the measurement accuracy.…”

“…However, current model approaches show evident limitations in reflecting the combined effect of water stress and elevated CO 2 on maize production, indicating that those models underestimate the CO 2 -fertilizing effect on maize under drought (Durand et al, 2017). However, current model approaches show evident limitations in reflecting the combined effect of water stress and elevated CO 2 on maize production, indicating that those models underestimate the CO 2 -fertilizing effect on maize under drought (Durand et al, 2017).…”

“…Tubiello et al (2007) find that most simulations of established crop models are in agreement with observations of up-to-date FACE experiments. However, a recent study by Durand et al (2017) revealed limitations in accurate simulations of biomass of the C4 crop maize under eCO 2 and restricted water supply. However, a recent study by Durand et al (2017) revealed limitations in accurate simulations of biomass of the C4 crop maize under eCO 2 and restricted water supply.…”

“…Jin, Ainsworth, Leakey, and Lobell (2018) simulated successfully the combined effect of eCO 2 and drought for the C3 crop soybean. The performance of 21 maize crop models was tested against data of the aforementioned 2-year FACE experiment with maize in Braunschweig, Germany (Durand et al, 2017). The performance of 21 maize crop models was tested against data of the aforementioned 2-year FACE experiment with maize in Braunschweig, Germany (Durand et al, 2017).…”

“…The effect of water stress is commonly simulated based on either the ratio of actual and potential transpiration, the ratio of water supply and water demand or the soil moisture content (Jin et al, 2016). To improve the maize models, Durand et al (2017) emphasized the need for a better representation of the strong reduction of transpiration under eCO 2 , to allow a stronger benefit of eCO 2 in periods of water stress. They emphasized in particular, these models must explicitly represent the stomatal response to eCO 2 .…”