Objectives

Functional-structural plant models (FSPMs) were designed to simulate 3-dimensional plant structure, as well as plant biophysical and physiological functioning with their mutual dependencies. However, when they include several processes and represent the plant at the level of organs (leaves, fruits, internodes), calculation times for FSPMs can become prohibitive, particularly for large plants like trees. A further problem with many FSPMs is caused by complexity: The necessary steps of parameter estimation, sensitivity analysis and validation against independent data are nontrivial, due to the large number of parameters and the intricate, often non-linear dependencies between the modelled processes.

The FSPM-Apple project which gathers four teams (3 French, 1 German) with expertise in botany, agronomical and horticultural crop modelling, mathematics and computer science addresses this problem. This project is devoted to two research foci: F1 – "Model development, calibration, analysis, and corresponding software tools", and F2 – "Case study: Modelling apple tree growth at organ, branch and whole-tree scale in response to environmental stresses, crop load variation and for contrasted genotypes".

FSPMApple is organized in four main packages.

• The first one deals with the development of upscaling and downscaling algorithms adapted to FSPMs and of corresponding user-friendly queries for the simulation platform GroIMP
• The second workpackage aims at the conceptualization and subsequent implementation of a functional-structural plant model of the bearing branch of apple, with a strong emphasis on combined carbon and water flows between sources (leaves) and sinks (developing fruits) within the same branch.
• The third workpackage mainly focus on modelling tree architecture in response to environmental conditions (water stress) and genotypic variability. The modelling activities are based on MAppleT and include the evolution of vegetative organ dimensions, metamer emergence dynamics and shoot mechanical proprieties throughout the annual growth cycles.
• The last work package is dedicated to the analysis, parameterization and statistical evaluation of multiscale functional-structural plant models, by developing new methods and applying them to the apple tree model to be extended / developed in WP 3 and 2.