Northwest flora:
The Northwestern Flora covers more than 85% of the country. It is very well characterized by the frequency and richness in species of numerous genera, in particular the genus Astragalus (at least 600 species); the genera: Cousinia (more than 200 species), Silene (more than 100), Allium (approximately 90), Euphorbia, Nepeta, Acantholimon (roughly 80 species), Onobrychis, Salvia, Centaurea (approximately 70 species), etc. Among other genera less rich in species, but present in the greatest part of the Northwestern zone, are: Acanthophyllum, Artemisia, Stipa, Phlomis, Stachys, Achillea, Bromus, Poa, Agropyron, Hordeum, Scrophularia, Eremurus, Echinops, Ephedra, Trigonella, Convolvolus, Alyssum, etc.
The arborescent vegetation includes a good number of Amygdalus, Prunus, Crataegus, Rhamnus, Pyrus, Celtis. The most important native trees are Quercus persica, Pistacia atlantica, Juniperus excelsa, various Tamarix and Salix, Populus euphratica and in the warmest regions Ziziphus spina-christi. In almost all the Northwestern zone the depletion of rangelands has favoured the extension of Poa bulbosa (and related species) and more recently Carex stenophylla (and related species). In occasionally-cultivated lands certain perennial weeds have extended considerably, such as: Hulthemia persica, Alhagi camelorum, Prosopis stephaniana, Glycyrrhizia glandulifera, G. glabra, Goebelia alopecuroides, Eremurus spp., Phlomis persica, Euphorbia spp., Peganum harmala, Cynodon dactylon, numerous Compositae, etc
a) Subdesertic flora. In the central "deserts" of Iran, a scattered vegetation is generally possible but very large areas are completely bare due to human influence, the excessive concentration of salt in the moister lowlands, or the extension of moving sand dunes. From the phytogeographic point of view there is still little reliable documentation on these areas. In this subdesert zone it is mainly edaphic and topographic factors which determine the vegetation belts. Many of the plants are halophilous Chenopodiaceae: Halocnemum strobilaceum, Salicornia herbacea, Seidlitzia rosmarinus, various Salsola, etc. Others Chenopodiaceae (Haloxylon, Cornulaca, Suaeda, etc.) can be abundant outside the saline areas, in particular on sandy soils and on very stony and rocky slopes. Perennial grasses are generally absent, except Aristida plumosa in some sandy or gravelly areas and Aeluropus repens on moderately saline soils, with perhaps a few Stipa barbata still existing on the mountains. The remainder of the vegetation includes Astragalus, Echinops, Heliotropium, Fagonia, Zollikoferia, Stellera, Reaumuria, etc., as well as a good number of spring annuals. Peganum harmala is frequent around villages and camp sites. This subdesertic flora can be distinguished from the steppic flora by the absence (or extreme rarity) of Artemisia herba-alba, Poa bulbosa, Carex stenophylla, Noaea mucronata, Stipa spp., etc.. In the warmer south-eastern region the flora is notably richer than in the north.
b) Steppic flora. In the very large area where precipitation varies between 100 and 230 mm, the vegetation types are very diverse, the determining factor being primarily winter temperatures, which depend on the altitude and even longitude (at equal latitudes and altitudes the eastern areas are noticeably warmer). The flora is generally richer in the southern and eastern regions due to a greater abundance of annuals.
Artemisia herba-alba still characterizes this flora well, but it has disappeared over wide areas as a result of uprooting, particularly in much cultivated regions such as Khuzestan. (To be contd.)
© Tehran Times 2005
