How good is the turbid medium-based app.pdfVIP

PART OF A SPECIAL ISSUE ON FUNCTIONAL–STRUCTURAL PLANT MODELLING How good is the turbid medium-based approach for accounting for light partitioning in contrasted grass–legume intercropping systems? Romain Barillot1, Gae?tan Louarn2, Abraham J. Escobar-Gutie?rrez1,2,*, Pierre Huynh1 and Didier Combes2 1LUNAM Universite?, Groupe Ecole Supe?rieure d’Agriculture, UPSP Laboratoire d’Ecophysiologie Ve?ge?tale Agroe?cologie, 55 rue Rabelais, BP 30748, F-49007 Angers cedex 01, France and 2INRA, UR4 P3F, Equipe Ecophysiologie des plantes fourrage?res, Le Che?ne – RD 150, BP 6, F-86600 Lusignan, France * For correspondence. E-mail abraham.escobar@lusignan.inra.fr Received: 11 April 2011 Revision requested: 23 May 2011 Accepted: 28 June 2011 Published electronically: 23 August 2011 ?Background and Aims Most studies dealing with light partitioning in intercropping systems have used statistical models based on the turbid medium approach, thus assuming homogeneous canopies. However, these models could not be directly validated although spatial heterogeneities could arise in such canopies. The aim of the present study was to assess the ability of the turbid medium approach to accurately estimate light partitioning within grass–legume mixed canopies. ?Methods Three contrasted mixtures of wheat–pea, tall fescue–alfalfa and tall fescue–clover were sown accord- ing to various patterns and densities. Three-dimensional plant mock-ups were derived from magnetic digitizations carried out at different stages of development. The benchmarks for light interception efficiency (LIE) estimates were provided by the combination of a light projective model and plant mock-ups, which also provided the inputs of a turbid medium model (SIRASCA), i.e. leaf area index and inclination. SIRASCA was set to gradually account for vertical heterogeneity of the foliage, i.e. the canopy was described as one, two or ten horizontal layers of leaves. ?Key Results Mixtures exhibited various and heterogeneous profil