In this study, 19 sites representing different habitats in Hail region were regularly
visited for two years, in each site 2-5 stands were selected for investigating floristic
composition and vegetation types in the area. A total of 124 species representing
34 families were recorded. The family Asteraceae is represented by the highest number
of species (21 species) followed by the Poaceae (17 species) and the Brassicaceae
(10 species) whereas, 15 families including Acanthaceae, Convolvulaceae, Moraceae,
Nyctaginaceae and Primulaceae, are represented by a single species each. Chronological
analysis of the vegetation in the area revealed the domination of Saharo-Sindian elements
in the wild vegetations and of weedy species in the cultivated plots. Therophytes
and chamaephytes are the dominating life forms of the vegetation spectra; therophytes
represent 49.20% and chamaephytes represent 29.00% of the total species in the study
area. Application of TWINISPAN and DECORANA classification and ordination techniques
to the data produced seven vegetation groups. Ruderal habitats comprised two small
groups A and F dominated by Phragmites australis and Imperata cylindrical (A), Euphorbia
peplus and Sisymbrium irio (F), respectively. Two vegetation groups (B and G) have
been recognized in the mountains and slopes dominated by Launaea mucronata, Trigonella
stellata (B) and Ficus palmate and Fagonia bruguieri (G). Other two groups (C and
E) inhabit the desert and mountainous wadies; these are represented by Gymnocarpos
decandrus and Ochradenus baccatus (C) and Senecio glaucus subsp. coronopifolius and
Rumex equisetiforme (E). On the other hand, one group (D) inhabits the cultivated
plots and is represented by Plantago albicans and Rumex vesicarius, the last group
also includes species restricted to the sand dune habitat of the Al-Nafud desert north
of Hail city and represented by Calligonum polygonoides and Halyxolon salicornicum.
The vegetation analysis indicated the invasion of Hail Flora by some foreign weeds
such as Solanum nigrum, Lactuca serriola and Amaranthus lividus. The presence of these
weeds points out the need to monitor the vegetation change in Hail region, and also
other regions of Saudi Arabia, in order to elucidate the human impact on the wild
plants diversity as human activities change with the fast development in the kingdom.