SIMWAL: A structural-functional model simulating single walnut tree growthin response to climate and pruning

SIMWAL (SIMulated WALnut) is a structural-functional tree model developed f or single young walnut tree (Juglans sp.). It simulates the 3D structure dy namics of the tree, and biomass partitioning among its different organs, fo r a period ranging from a few months to several years, according to climati c conditions (temperature, radiation and air CO2 concentration) and pruning . The aerial part of the tree is represented by axes split into growth unit s, inter-nodes, buds and leaves. The root system is described very coarsely by three compartments (taproot, coarse root and fine root). Only carbon-re lated physiological processes, i.e., radiation interception, photosynthesis , respiration, photosynthate allocation, and reserve storage and mobilisati on are taken into account. Water and mineral nutrients are assumed to be op timal. We describe the model, and present preliminary tests of its ability to simulate tree architecture dynamics and carbon balance compared with fie ld observations. Data requirements, and limits and improvements of the mode l are discussed.