الفهرس 
Introduction
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Abstract
The present thesis is aiming at studying the impacts of the different types of waste waters usually drain into Damietta Branch of the River Nile and the successive changes of the vegetation along its course. Also, to determine the factors controlling the distribution and abundance of the plant communities in the study area. Sixty sampling quadrats were selected to represent the Damietta Branch of the River Nile in the five provinces of the study area. The total number of hydrophytes and terrestrial bank plants recorded in the present study is 70 species belonging to 54 genera grouped under 30 families. Out of these families, Chenopodiaceae and Gramineae, Asteraceae and Cyperaceae are the main families being represented collectively about half (48.57%) of the total number of recorded species. According to the life-span, the recorded taxa can be classified to annuals:24 species and perennials:46 species. According to the life-form spectra of the recorded species, the majority of plants are mainly cryptophytes (48.57 %) which include geophytes, helophytes and hydrophytes, and partly therophytes (34.29%). Chamaephytes (11.43%), hemicryptophytes (10.0%) and phanerophytes (5.72 %). The floristic analysis of the study area revealed that, about 31.43% of the total number of the recorded species are Mediterranean taxa, Cosmopolitan (18.57%), Palaeotropical and Pantropical (14.29% each) or Neotropical (8.57 %). The application of TWINSPAN classification on the importance values of plant species recorded in 60 sampled stands led to the recognition of four vegetation groups. The application of Canonical Correspondence Analysis (CCA) led to the determination of the most effective hydrosoil variables which correlate with the distribution and abundance of the vegetation groups were: the concentrations of sodium, SAR, water-holding capacity, total phosphorus, bicarbonates, and sulphates. The percentages of chlorides, total phosphorus, sodium, SAR, potassium, PAR, magnesium, sulphates, electrical conductivity and calcium are the most important water variables. On the other hand, Co, Zn, Ni, Pb and Cd in hydrosoil and Co, Ni and Fe in water samples were the most important heavy metals, they affected on the vegetation. The concentrations of iron ion in the tissues of the four selected hydrophyte in the study area were, relatively, the highest among those of the other heavy metals and least amounts are those of cobalt ion.