Dynamic modeling of the growth of Phragmites australis: model description

A dynamic model was developed to simulate the growth dynamics of a monospec ific stand of Phragmites australis in freshwater ecosystems. Five state var iables (biomass of shoots, inflorescence, roots, old rhizomes and new rhizo mes) were selected to illustrate the growth of P. australis. Growth was des cribed using mathematical relationships. The net growth of the plant stand was the integral effect of photosynthesis, respiration, mortality and assim ilate translocation between shoots and below-ground plant organs. Below-gro und biomass (i.e. rhizome and root biomass) before the growth commencement, daily total global radiation and daily mean air temperature were input dat a. The model is capable of simulating the seasonal variation of above-groun d biomass (shoots, stems, leaves and panicles), leaf area index, rhizome, n ew rhizome, root biomass and shoot height with correlation coefficients clo se to 1.0 for most of the parameters. The model estimated the conversion ef ficiency of photosynthetically active radiation varying from 3.76 to 7.19% from northern temperate regions to warmer southern temperate regions. The c arbon budget was constructed using the modelled predictions. Analysis of an nual net production and fluxes showed that irrespective of the varying clim atic conditions, the percentage of annual fluxes of an event, as a proporti on of the total photosynthetic production remained almost same. The respira tion of shoots, as well as rhizomes and roots, was shown to consume a consi derable amount of photosynthetic production: 25% by shoot respiration and 4 0% by rhizome and root respiration. (C) 2000 Elsevier Science B.V. All righ ts reserved.