Species Diversity and Phenology of the Wetland Vegetation in Siwa Oasis, Western Desert, Egypt

الملخص EN

This study evaluates species diversity, phenology and the effect of environmental variables on the vegetation composition of the wetland habitats in Siwa Oasis.

Thirty-six stands were sampled in the different habitats (salt marsh, lakes and springs).

These stands were classified into four vegetation groups using TWINSPAN analysis.

The indicator species were Juncos rigid us, Altai Mauro rum (Group A), Arthrocnemum macrostachyum (Group B) Phragmites Australia, Scarps littorals (Group C), Typhus domingensis, Ceratophyllum dimerism (Group D).

Soil salinity, water table and the percentage of gravel in the soil showed significant variations among vegetation groups.

The diversity indices did not vary among the groups.

The distribution pattern of the dominant species along the gradient of nine environmental variables was examined using canonical correspondence analysis (CCA) ordination.

The number of species with vegetative, flowering and fruiting plants was higher in summer, while the number of species with dormant plants was higher in winter in reed swamp habitat.

An opposite trend of change in the phonological status (dormant vegetative and flowering) of plant species in dry and wet salt marsh was detected.

The number of species with fruiting plants had two peaks, one in summer and the other in winter.

The floristic changes of Siwa Oasis wetland within the last thirty years were discussed.

Also, some reasons that may led to the disappearance of some species e.g.

Caladium meniscus which was previously reported as dominant species are given.