CO2-response function of radiation use efficiency in rice for climate change scenarios

Abstract

The objective of this work was to evaluate a generalized response function to the atmospheric CO₂ concentration [f(CO₂)] by the radiation use efficiency (RUE) in rice. Experimental data on RUE at different CO₂ concentrations were collected from rice trials performed in several locations around the world. RUE data were then normalized, so that all RUE at current CO₂ concentration were equal to 1. The response function was obtained by fitting normalized RUE versus CO₂ concentration to a Morgan-Mercer-Flodin (MMF) function, and by using Marquardt's method to estimate the model coefficients. Goodness of fit was measured by the standard deviation of the estimated coefficients, the coefficient of determination (R²), and the root mean square error (RMSE). The f(CO₂) describes a nonlinear sigmoidal response of RUE in rice, in function of the atmospheric CO₂ concentration, which has an ecophysiological background, and, therefore, renders a robust function that can be easily coupled to rice simulation models, besides covering the range of CO₂ emissions for the next generation of climate scenarios for the 21^st century.