Flora of Iran

Being given the big size of the country and the varieties climatic due to various factors the differences in altitude, the level of precipitations and evaporation, the types of grounds etc the territory of the Iran has a great quantity of Biome S and Biotope S, which amounts saying an important variety in the indigenous flora. More than 8.000 species (including 450 endemic) are indexed there; the trachéobiontes are more numerous there than in Central Europe. The composition of the flora of Iran is defined by four factors: climate, phytogeographical diversity, topography and the human intervention.

Climate

Iran is located between the anticyclonic masses of air of the Central Asia and Siberia at north, the Mediterranean mode of the winds in the center (winds of west and depression bringing the rain and snow) and of the influences, tropical and subtropical in the south and the south-east of the country. There thus exist various types of climate in Iran, since the wet subtropical low-grounds on the southern part of the Caspian Sea to the hot and dry deserts (Dasht-e Kavir and Dasht-e Lut).

The mountainous chains of the Alborz (Elbourz), of the Zagros and the North-West of Iran are characterized by surpluses of precipitations; they are thus wet for part of the year, even all the year. The remainder of the country is characterized by deficits: the lack of precipitation, the permanent strong winds or and the high temperatures are the cause of an extreme aridity.

The differences in climate correspond to the ecological differences. 90% of the Iranian territory belong to the climatic zone “Irano-Touranienne” according to Henri Pabot. The characteristics of this zone are:

of the very variable precipitations, generally between 100 and 500 mm, concentrated in winter or in spring.
at least three summer months characterized by a total dryness, period extending to 9 months in the most arid areas.
a relative humidity between 80 and 55% (for the central desert, proportion falling with 40 and even 20% in summer)
of the very variable temperatures according to the area, but of the generally cold winters. The summers are extremely hot in the Khuzestan (36°C on average in July), very heats in the central depression (more than 30°C) and heats elsewhere (enters 24 and 29°C), except in the mountainous regions with the tops of 2.000 or 2.500 Mr.

Topography

The climate and the vegetation depend on topography, and more particularly on the relief. The Elbourz and the Zagros are probably among the examples more striking influence of topography on the natural habitats of the flora and fauna:

sarhadd , for the subtropical high areas with very cold winters and fresh summers
to sardsir , for the fairly high areas with cold winters and hot summers
the subtropical highlands, which have three hot sub-types (cold winters, summers and strong frosts; soft winters, hot summers and short period of frost; soft winters, hot summers and rare frosts)
to garmsir , for the low grounds at the hot winters and summers, without frozen and snows.

The other big factor defining the diversity of the vegetation is the ground. Four areas can be distinguished, gathering nineteen associations of grounds:

the grounds of the plains and the valleys cover approximately: 300000 km ². This area present:

of the saline grounds (Solontchak, Solonetz), typical of the areas of the dasht (Dasht-e Kavir and Dasht-e Lute)
of the fine alluvial grounds
of the endoreic basins

the plates recovers approximately: 470000 km ², with various types of grounds:

of the grounds of gray and red desert
of the Sierozem S (grounds extremely limestones)
of the brown grounds of steppe

the grounds of the piémonts of Caspian covers approximately: 35000 and are the resultant of the climate and of the flora of the area, they contain much humus and are very ventilated.

brown grounds of forest
Podzosol S yellow-red

Moreover, because of the distribution of the mountains and the aridity, almost 50% of the surface of the ground are composed of stony grounds and little épaix on a rock bed, without defined profile, which is called lithosols. This would be due to natural erosion.

Phytogeographical diversity

The vegetation, its density and its composition are function of the Iranian climate, the topographic ground and other factors. The botanists distinguish several biogeographic areas.

Semi-desert and desert zones

The semi-desert flora of the areas is made up of sparse vegetation, in particular in the endoreic deserts of the center of Iran, with great salt concentrations in the basins ( to kavir ) and of the zones where sands dominate. The plants Halophile S dominate, and the hardy perennials generally absent.

Steppes

The flora of the steppes consists of a varied vegetation, determined by the winter temperatures. Plants of various species were very current in the past but their number was reduced by the human activity. Services of the forests was founded at that time. In 1970, this service employed more than 3.000 foresters, and had made it possible to plant 1,3 million young trees on 526.315 hectares of ground.

The forest grounds are estimated at 18 million hectares in 1987, of which only 3,2 million is regarded as productive near the Caspian Sea. The illegal cuts remain however frequent

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