Ecological Regions in Iran
The differences in northern and southern latitudes, topographic features including internal plains and climatic conditions of the country have created varied characteristics with a rich plant species and vegetation regions in this territory as follows:
1. Hyrcanian Region
Hyrcanian region is located in the northern part of Elborz and the southern part of the Caspian Sea. These forests form a rather narrow green belt bordering the northern part of the Alborz Mountains and extend from Astara in the west of Gilan Province to Giledaghi in the east of Golestan province with an area of 2086371 h.
Fertile soil, proportionate precipitation and high humidity have created a varied collection of plants in this region, including about 80 species of trees- mainly deciduous species- as well as four species of conifers and 50 species of shrubs of which the most important are: Fogus orientalis, Acer insigne, Acer Cappadocicum,Ulmus glabra, Fraxinus excelsior, Tilia begonifolia,Cerasus avium, Quercus castaneifolia, Zelkova carpinifolia,Alnus subcordata and Carpinus betulus.
Hyrcanian forests belong to the end of the third geological era, are known as the oldest forests in the world, that due to environmental and economic values are considered as world natural heritage.
2. The Iran-o-Touranian Region
The region is recognized as the vast vegetation region of the country that covers an area about 4666941 ha. It is located in the central plateau of Iran. The region is divided into two sub-regions including mountainous region with cold climate and low land section with dry climate based on topography and altitude from the sea level. Although climatic condition in the region has made vegetation pattern unevenly distributed, however, the vegetation diversity is significant which is home to 69% of Iran's flora. Having very little precipitation and a long arid season, on the whole differentiates the region from other parts of the country.
This region is quiet unique in terms of distribution and number of species in the country, especially goat's thorn geneses: Astragalus with more than 600 species. There are also many species of Silen Cousinia, Allium , Nepeta, Euphorbia, Centaurea acantholimon, Salvia and Onobrychis in this region.
3. The Arasbarani Region
The region covers an area about 174838 ha and is located in the north east of East Azerbaijan province in the watershed basin of the Aras River. The area’s sub-humid
Arasbaran is characterized by unique and rear plant species and thus have been registered in UNESCO's biosphere reserves. This region has been protected for the last 30 years and it is the main habitat of some of the world’s rarest fauna. Most of the forest species of the Hyrcanian region can be found in here. However, lack of the main tree species of this region such as beech and alder, has differentiated it from the Hyrcanian region. The region of Arasbaran has been registered as the world’s foremost genetic reserve for its high biological variety, and so far more than 775 plant species have been identified in protected areas alone, of which 55 species have been reported for the first time from Iran. There are about 100 tree species, the most important of which are as follows: Acer, compestire, Amygdalus sp., Carpinus orintalis, Celtis australis, Cornus mas, Corylus avellana, Ficus carica, Fraxinus rotandifolia, Juglans rejia, Juniperus communis, morus sp., Pistacia mutica and Quercus komarovii.
The Arasbarani forests
4. The Zagros Region
The Zagros Mountains extend from the North West border (south of Ararat Mountains) up to the Straits of Hormoz alongside Hassan Longi River in the west of Minab. This mountain range covers the west side of the country parallel to the western border and therefore are under the direct impact of the sub-humid climate from Black Sea and the Mediterranean Sea in the form of precipitation and thus creates a suitable condition for forestation. The forests in this region are located in Western Azerbaijan, Kurdestan, Kermanshah, Ilam, and Lorestan, Chaharmahal-e-Bakhtiari & Boyerahmad as well as some parts of Fars province. These forests were denser and much vaster in the past. The remaining forest is a protected area bordered by the Piranshahr to Sardasht road in Western Azerbaijan province (known as Qabre Hossein) up to Firouzabad in Fars province, about 5,440,494 ha..
The principal species of tree found in the Zagros forests is oak which has been able to survive despite heavy felling as well as overgrazing in the area. It should be mentioned that if there was not coppice ability, the western forests in Iran would be destroyed.
The most important plant species in this region includes Quercus infecturia, Q.libani and Q. brantii which can be found in the Zagros forests in addition to other tree and shrubs species like Acer Persicum , Amygdalus spp.Berberis vulgaris, Celtis caucasica, Crataequs sp,Cotoneaster sp, Cupressus horizantalis , P. Fraxinus sp., Pistacia mutica, Pistacia Khinguk, Prunus sp and Pyrus sp.
It is an undeniable fact that the Zagros forests contribute to soil conservation as well as approximately 45% of the water supply in Iran, and also may contribute to the development of the economy in that region. The government, however, due to lack of regeneration has protected the Zagros forests and has a detailed conservation program for this region.
5. The Persian Gulf and Oman Sea Region
This region extends as a narrow strip to the southern part of Iran passing through Khouzestan, Boushehr, Hormozgan and Sistan & Balouchistan provinces that cover an area about 2039963 ha. The mean annual precipitation ranges between 100-250 mm, generally increasing from east to west, whereas annual humidity increases from west to east. Ecological differences and variations have divided the region into Persian Gulf and Omanian regions.
The Persian Gulf territory is bound by Qasr-e-Shirin up to the border of Boushehr and Hormozgan provinces. The main trees and shrubs of this region are Zizyohus spina christi, Prosopis farcta and Zizyphus nomularia . The Omanian region contains territories of Hormozgan and Sistan & Balouchistan provinces and the main trees and shrubs to be found here are Prosopis spicigera, Acacia tortilis , acacia nilotica. A.nubica can also be found scattered in this region and its wood is used for the ship-building industry. Other main tree species of this region are: Albizia lebbek, Capparis decidua, Calatropis procera ,Ficus bengalensis, Haloxylon spp.,melia indica, Nerium indicium,Prosopis,juliflora,procopis specigera, Taramix spp., Tecomella undulata, zygophyllum sp. and Salvadora persica.
Mangrove forests consist of two species of Avecina marina and Rhizophora mucronat which can be found along the coastal line of the Persian Gulf and Oman Sea, particularly in the north of Qeshm Island. These forests are the habitat of a number of valuable species of marine animals and sea birds, and have special bio-ecological value.