Adaptation of a functional model of grassland to simulate the behaviour of irrigated grasslands under a Mediterranean climate: The Crau case

In order to take into account firstly the specificities of Mediterranean weather conditions on grass growth and secondly the effect of irrigation management on hay, we adapted an already published model of grassland growth. From literature new equations were added to account for water balance, botanical composition and the effect of wind. The modified model was parameterised based on new experimental data. An automatic and rigorous parameter estimation Procedure was developed based on a criterion that combines the goodness-of fit for dry matter (DM), leaf area index (LAI) and fraction of total transpirable soil water (FTSW). Mean squared error of prediction (MSEP) was estimated using cross-validation. Adding the three equations for water balance, botanical composition and wind effect improved the goodness-of-fit of the model. A sensitivity analysis showed that the model results were mainly sensitive to the parameter that controls the increase of leaf area index and to the radiation use efficiency coefficient. Both absolute values and dynamics of DM LAI and FTSW were well simulated and satisfactory for future use of the model in a decision Support tool. Estimated MSEP values for DM, LAI and FFSW were 0.145Tha(-1), 0.092 m(2) m(-2) and 0.0155% respectively. (C) 2008 Elsevier B.V. All rights reserved.