Modelling of reserve carbohydrate dynamics, regrowth and nodulation in a N2-fixing tree managed by periodic prunings

We used a modified transport resistance approach to model legume tree growth, nodulation and dynamics of reserve carbohydrates after pruning. The model distributes growth between roots and shoots applying the transport resistance approach. Within shoots, growth is divided into leaves, branches and stems applying the pipe model theory. The model also accounts for the metabolic differences of principal N sources, nitrate, ammonium and atmospheric dinitrogen, in a mechanistic way. We compared the simulation results with measured biomass dynamics of Gliricidia sepium (Jacq,) Walp. (Papilionaceae: Robinieae) under humid and subhumid tropical conditions. Comparison showed that the biomass production predicted by the model is close to measured values. Total N-2 fixation is also similar to measured values. Qualitatively the model increases the proportion of N-2 fixation if roots acquire less mineral N, In the present study the general form of the model is discussed and compared,vith similar models. The results encourage the use of this approach for studying biomass dynamics of legume trees under the scheme of periodic prunings, Also, it shows that process-based models have potential in the simulation of trees disturbed by prunings, herbivory or similar factors.