Modeling the growth dynamics of Pistia stratiotes L. populations along the water courses of south Nile Delta, Egypt

Abstract

We developed a dynamic numerical model to describe the growth production and the interaction between shoots and roots of Pistia stratiotes under natural conditions in south Nile Delta, Egypt. Two state variables, shoots and roots, were considered to simulate the growth of P. stratiotes. The biomass of each organ was formulated to incorporate the net growth of the plant as a function of photosynthesis, respiration, mortality, and translocation from shoots to roots. Shoots and roots biomasses of P. stratiotes was sampled monthly from May 2013 to February 2014 along three water courses of Giza Province using three randomly distributed quadrats (each of 0.5 × 0.5 m) at each water course. General trends for shoots biomass, such as the slow initial growth rate followed by a high growth rate, the timing of peak biomass, and the decline of biomass due to senescence, were successfully reproduced by the model. Many characteristics typical for the roots biomass, such as the increase in the roots biomass during the early growing season because of the translocation of materials from shoots, and the reduction of roots biomass during the later period of the season, were also reproduced. In general, there was a good agreement between the calculated results and field data although simulated results were slightly different from observations for roots biomass. In conclusion, Pistia model could be used to predict the potential growth of P. stratiotes and this model might be useful for practical applications such as the management of water courses.