Use of a crop model ensemble to quantify CO2 stimulation of water-stressed and well-watered crops

Challinor, A.J. and Wheeler, T.R. (2008) Use of a crop model ensemble to quantify CO2 stimulation of water-stressed and well-watered crops. Agricultural and Forest Meteorology, 148 (6-7). pp. 1062-1077.

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Increased atmospheric concentrations of carbon dioxide (CO2) will benefit the yield of most crops. Two free air CO2 enrichment (FACE) meta-analyses have shown increases in yield of between 0 and 73% for C3 crops. Despite this large range, few crop modelling studies quantify the uncertainty inherent in the parameterisation of crop growth and development. We present a novel perturbed-parameter method of crop model simulation, which uses some constraints from observations, that does this. The model used is the groundnut (i.e. peanut; Arachis hypogaea L.) version of the general large-area model for annual crops (GLAM). The conclusions are of relevance to C3 crops in general. The increases in yield simulated by GLAM for doubled CO2 were between 16 and 62%. The difference in mean percentage increase between well-watered and water-stressed simulations was 6.8. These results were compared to FACE and controlled environment studies, and to sensitivity tests on two other cropmodels of differing levels of complexity: CROPGRO, and the groundnut model of Hammer et al. [Hammer, G.L., Sinclair, T.R., Boote, K.J., Wright, G.C., Meinke, H., Bell, M.J., 1995. A peanut simulation model. I. Model development and testing. Agron. J. 87,1085–1093].TherelationshipbetweenCO2andwater stress in theexperimentsand in the models was examined. From a physiological perspective, water-stressed crops are expected to showgreaterCO2 stimulation thanwell-watered crops.This expectation has been cited in literature.However, this result is not seen consistently in either the FACE studies or in the cropmodels. Incontrast, leaf-levelmodelsof assimilationdoconsistently showthis result. An analysis of the evidence fromthese models and fromthe data suggests that scale (canopy versus leaf),model calibration, andmodel complexity are factors in determining the sign and magnitude of the interaction between CO2 and water stress. We conclude from our study that the statement that ‘water-stressed crops show greater CO2 stimulation than well-watered crops’ cannot be held to be universally true. We also conclude, preliminarily, that the relationship between water stress and assimilation varies with scale. Accordingly, we provide some suggestions on how studies of a similar nature, using crop models of a range of complexity, could contribute further to understanding the roles of model calibration, model complexity and scale.

Item Type: Article
Author Affiliation: Institute for Climate and Atmospheric Science, School of Earth and Environment, The University of Leeds, Leeds LS2 9JT, UK
Subjects: Atmosperic Science > Meterology
Divisions: General
Depositing User: Sandhya Gir
Date Deposited: 19 Jan 2011 18:13
Last Modified: 19 Jan 2011 18:13
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