Modeling growth dynamics of Typha domingensis (Pers.) Poir. ex Steud. in Lake Burullus, Egypt

Abstract

Southern Cattail (Typha domingensis) occurs everywhere in ditches and marshy places in Egypt and is one of the major components of vegetation stands along the shores of Lake Burullus close to the Deltaic Mediterranean coast. In our study, we applied a published Typha model to describe the growth production among the various organs of Southern Cattail in Lake Burullus, one of the Mediterranean eutrophic lakes, in order to answer the following questions: (1) Is the Typha model, originally designed for T. angustifolia and T. latifolia, suited to simulate the growth of Southern Cattail in the south Mediterranean region? and (2) How is biomass production of Southern Cattail distributed among the various plant organs? Above- and below-ground biomass of Southern Cattail was sampled monthly from February 2010 to October 2010 at three sites of Lake Burullus using three randomly distributed quadrats (each of 0.5m×0.5m) at each sampling site. Shoots started to grow in February, reached the maximum biomass of 6327±441gDWm−2 in July, and then rapidly decreased in the fall when they went to senescence stage, thereafter their growth ceased before fully dying off in the winter. The total below-ground biomass reduced to 941±152gDWm−2 in March due to the upward translocation for the initial growth of shoots, gradually increased to a maximum biomass of 2184±366gDWm−2 in July by downward translocation from shoots, then decreased afterwards in the winter to reach 1193±64gDWm−2 in October. Southern Cattail allocated approximately 52% of its total biomass to non-flowering shoots, 19% to flowering shoots, 22.5% to rhizomes and 6.5% to roots. The total above-ground biomass was 2.6 times that of the total below-ground biomass. General trends for above-ground 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 below-ground biomass, such as the reduction of rhizome biomass during the early growing season, and the increase in the rhizome biomass during the later period of the season, because of the translocation of materials from current photosynthesis and shoot dry matter, were also reproduced. In general, there was good agreement between the calculated results and field data although simulated results were slightly different from observations for below-ground biomass. Respiration of the above- and below-ground organs consumes a considerable amount of net photosynthetic materials 39% and 7%, respectively. The upward translocation of rhizome resources to form new shoots in February showed 8% to the gross production and the downward translocation afterwards showed a 22% to the gross production. In conclusion, Typha model is well-suited to simulate the growth of Southern Cattail stands in the south Mediterranean region and could be used in wetland management activities to predict the potential growth of Southern Cattail in Egyptian wetlands.