A comparison of the functional traits of Phragmites australis in Lake Burullus (a Ramsar site in Egypt): Young vs. old populations over the nutrient availability gradient

Abstract

This research was performed in order to compare the functional traits (morphology, density and biomass) of Phragmites australis (common reed): young vs. old populations which were analyzed along nutrient availability gradient in Lake Burullus (Egypt) every month for a year. The samples were gathered from six sites distributed equally along the northern and southern parts of this lake. The present study indicated that, water N, P, Ca and Mg concentrations of the southern sites were higher than those of the northern sites. Shoot height, stem diameter, number of leaves, flowering ratio, leaf area, and leaf area index (LAI) were significantly lower in young populations compared with old populations. However, shoot density was significantly higher in young populations compared with old populations. The above-ground biomass increased from February until it reached its maximum during August and then decreased again, while a decrease in below-ground biomass in spring to support the rapid shoot growth, followed by an increase in summer due to the shoot translocations in the reverse direction was indicated. The CR (common reed) exhibited a slower relative growth rate (RGR) during cooler months, September–December, while highest RGR was achieved during spring months, March–May. In Lake Burullus the results from this field work indicated that shoot height, stem diameter, number of leaves, flowering ratio, leaf area, LAI, and biomass of CR increased with increasing nutrients along north-south direction in Lake Burullus, where lake eutrophication influenced CR growth positively. Thus, the theory that the biomass and morphology of this macrophyte is determined by the water trophic content is reinforced. The collection of this data is valuable to further comprehend the growth cycle of CR and to contribute to the future management and utilization of CR in the Egyptian wetlands.