Based on the current available information on the flora and vegetation of the Asir mountain of SW Saudi Arabia, spectra on life form and some other ecological attributes were analyzed and reviewed in different sub-ecosystem of the investigated area. The floristic list of Asir Mountain of the Kingdom of Saudi Arabia consists of 189 species belonging to 74 families, 65 dicotyledons (dicots), 4 monocotyledons (monocots), while gymnosperms and pteridophytes were represented by one family each. Asteraceae was the dominating family in the study area. According to the Raunkiaerian life form therophytes (36.5%) followed by hemicryptophytes (15%) and geophytes (12.5%) were dominant in the area. Chaemophytes 6.5%, mesophanerophytes 3%, megaphanerophytes 2%, nanophaneorophytes 13% and climbers 1.5% contribution in the establishment of vegetation structure in the study area. In leaf size spectra, the analysis revealed that microphylls (38.5%) followed by nanophylls (24%), leptophylls (13.5%), mesophylls (12%), macrophylls (3%) and megaphylls (1%) construct the vegetation belt of the area. The biological spectrum of the high altitude was characterized by phanerophytes mainly representing nanophanerophytic followed by hemicryptophytic and geophytic species. These were increasing with the rise in elevation while the megaphanerophytic species were decreasing. The vegetation cover in general and the tree layer in particular were observed very rare and sparse. The grassland vegetation is characterized by the largest percentage of hemicryptophytes. In this region, the vegetation expression was predominantly evergreen, although the tree flora has considerable elements of deciduous species. The dominance of phanerophytes appears to be due to high rainfall, temperature and low biotic pressure. However, the population of therophytic species was increasing in highly grazed and eroded areas.Keywords: Biological spectrum, Asir mountain, leaf size, life form, biotic and abiotic factorsAfrican Journal of Biotechnology Vol. 9(34), pp. 5550-5559, 23 August, 201
