Population Dynamics and Multivariate Analysis of Vegetation in Lake Manzala, Egypt

A distribution map of 17 prominent species in different habitats of lake Manzala is constructed after surveying 17 major stations distributed over the lake. The spatial population dynamics was tested through a comparison with a previous mapping, before 20 years ago. During that period six species showed reduced zonation, however, other species invaded the lake, sometimes with expanded zonation. Studying the temporal dynamics on the species-level in the lake over 8-years period, on 16 species showed that five species (31%) became extinct from the lake, while six species (27% of the present potential) are the new records. Our new records include Azolla filiculoides (fern), Jussiaea repens, Lemna gibba and Ruppia maritima, as hydrophytes and Echinocloa stagnina and Panicum repens, as lithophytes or amphibians. The cumulative temporal dynamics over 60-years period (1937-1996) was investigated on the cumulative number of species (36) and revealed that the ratio of the extinct species to the sustaining species is 17:19 species, respectively (i.e. 47% : 53%). The multivariate classification analysis of 30 stands resulted in six community types, namely Eichhornia crassipes, Phragmites australis-Typha domingensis, Inula crithmoides, Halocnemum strobilaceum, Arthrocnemum macrostachyum and Sarcocornia fruticosa. Seventeen species are organized in four clusters, representing habitats with different salinity levels, namely fresh-water, transitional water quality (ecotones), low saline soil and high saline soil. The multivariate ordination analysis on 17 species resulted in five distinct clusters between the first two axes. The first axis showed a positive correlation with moisture availability, while the second axis showed a negative correlation with salinity levels, suggesting that moisture and salinity are likely to be the major limiting factors for distribution of plant species in lake Manzala`s environment.