DETERMINATION AND CLASSIFICATION OF THE GEOGRAPHICAL DOMAIN OF IRANIAN DESERTS (CASE STUDY: KHORASAN PROVINCE DESERTS)

Real deserts as one of the most important biomes of biosphere, occupy nearly 7.5 percent of world arid lands (UNDP, 1997). In order to determining geographical domain of real deserts for correct managing and sustainable development, we need to information about environmental factors that interactions between them resulted to desert condition. So, in this research which was carried out in 2000-2003, some of major earth sciences such as Geology, Geomorphology, Climatology, Hydrology, Pedology and Vegetation cover which are directly or indirectly affected on existing desert bioms, were studied. Then, considering fitness index for any of above subjects using standard tables, map of Khorasan deserts were drawn in six layers. Scale of base maps were 1/250000 that digitized in Geographical Information System (GIS) and were analyzed by Ilwis software. Individual analyzing of environmental factors indicated that climatic deserts contain the maximum area of Khorasn province (22100112 hectare), while geomorphologic deserts have the lowest area (3551050 hectare). Crossing and matching of different layers showed that total area of desert regions including common and noncommon areas is about 24520687.5 hectare which is covered over than 82.79Khorasan province. In addition to overlying of desert layers resulted in boundary of real or potential deserts in area equal with 1418450 hectare which is covered over of 4.79 Khorasan province. Vital resources are limited seriously by harsh conditions such as low precipitation, evaporate formations, logging of water table, and so on in real deserts. Recent region contain different landscapes and facies of playa for example: salt marsh (Kavirs), Dags, Badlands, Flooded beds and Sand dunes. So, it is recommended non development program at this area because of lack population and vital sources. Difference between common and non-common areas of overlaid layers is about 23102237.5 hectare which is named Semi-desert areas and covered over of 87 Khorasan province. Because of concentrating of human communities and consequent development of exploiting activities, desertification phenomenon is obviously accelerated recent area. Desertification process such as degradation of vegetation due to overgrazing, secondary salinization, wind erosion, water erosion, decreasing infiltration rate and water logging were occurred at this area. Thus, mismanagement and exceed exploiting from destructive sources of semi-desert areas caused land degradation and desertification. Hence, development programs in semi-desert areas were failed so far and were caused many problems from view of social, economy and migration. So, primary it is necessary to performance combat desertification programs at this area. Secondary, it is recommended determining fitness land use by monitoring of environmental factors permanently.