Modelling nitrogen partitioning in young trees during the first year of growth
1990
Habib, R. | Loisel, P. | Wallach, D.
A dynamic simulation model of total nitrogen partitioning in a whole tree was developed based on previous experimentals results. In this model, four compartments are considered-roots, trunk, shoots and leaves. Nitrate absorption by roots is described by an equation similar to the Michaelis-Menten equation with maximum inflow rate changing with time. The main assumptions of the partitioning model are (i) only certain of the flow pathways between compartments need be considered (ii) for each compartment, the rate of nitrogen outflow depends on the nitrogen content of that compartment (i.e. its source capacity) (iii) the rate of nitrogen outflow from a compartment is proportional to the sum of rates of dry matter increase in the compartments that can act as sinks for that compartment (i.e. sink needs considered as driving forces) (iv) total outflow from a compartment is divided among the compartments that can act as sinks according to their rates of dry matter increase (i.e. sink equality). In the present study, the first year growth of peach trees in sand culture is considered. Data were collected from the beginning of the growing season till after leaf fall. This differs from the previous studies in that growth over a longer time period is considered. Only the data up the start of leaf fall are used to test the model. The results of the nitrogen allocation model were compared to the observe tree N data. It is shown that the fitted data are very close to the measure values.
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