Recognition of Desert Environment and Classification - their Limitation Intensity by GIS in Yazd Province

摘要

Yazd province with 73000 km~2 and arid climate has located in central plateau of Iran. In spite of dryness it has various natural environment, so that the altitude is 800 m. to 4045 m. above sea level. According to several thousands years of civilization and utilization of desert resources, people has had peaceful coexistence with desert environment in this region. Desertification is main manager's problem in last decade, with classifying of this large environment, usable area and their limitation will be cleared, then sustainable utilization is available. With known definition 6 maps were produced. Each map has 3 classes, desert, semi-desert and non-desert environment. The subjects of these maps were climatology, vegetation, pedology, geology, geomorphology and hydrology. With calculation technique in GIS environment, by using Ilwis 3.2 software maps were combined and 2 final maps were produced, 1 - Desert environment map, 2- Intensity map of limitation or degree of desert. For combining maps Boolean algebra and logical terms were used. All maps were rasterized with pixel size of 100~* 100 meter; therefore the study area has 7309300 pixel. Only five maps of six maps were used in processing, because the hydrology map didn't have enough information for our purpose. The environment that in all five maps had consensus of non-desert, in final map was called non-desert and the environment that at least in one map was desert in final map was called as desert and the rest of area was called semi-desert. In the desert limitation rate map, the pixels with number 1 to 5 shows degree of limitation. By the results of this study, 79.3, 17.1 and 3.6 percent of the Yazd province area are desert, semi-desert and non-desert respectively. Due to 5796270 ha. of desert environment, the area with 1, 2, 3,4 and 5 limitation factor have 27.8, 26.7, 26.2, 13.6 and 5.8 percent of desert environment.