بررسي تغيير كاربري اراضي در بيابان زايي محدوده شهر اردكان با استفاده از سنجش از دور

بيابان زايي يكي از عوامل تهديد كننده حيات بشري است كه موجب تخريب منابع طبيعي مي شود. بنابراين شناخت پديده بيابان زايي و عوامل موثر بر تشديد آن براي كشور ما داراي اهميت حياتي مي‌باشد. در اين تحقيق از اطلاعات تصاوير ماهواره اي و عكس هاي هوايي براي بررسي نقش تغييركاربري اراضي بر پديده بيابان زايي محدوده شهر اردكان استفاده شد. به اين منظور، براي سالهاي 1334 و 1376 از عكسهاي هوايي موجود و براي سال 1381 از تصاوير IRS استفاده گرديد. پس از موزاييك كردن عكسهاي هوايي، عمليات پردازش با نرم افزارILWIS انجام گرفت. براي تهيه نقشه كاربري اراضي، از تصاوير به روش پردازش رقومي اقدام و در نهايت پنج نوع كاربري در منطقه شناسايي شد. در هر نوع كاربري 10 نمونه تعليمي به طور موزون در منطقه انتخاب شد. در نهايت، مساحت هر كاربري و ميزان تغييرات آنها در دوره زماني مورد مطالعه محاسبه گرديد. نتايج حاصل بيانگر كاهش وسعت مناطق بياباني از سال 1334 تا سال 1376 به ميزان 2000 هكتار و از سال 1376 تا سال 1381 به ميزان 160 هكتار و افزايش مساحت كاربريهاي ديگر مي‌باشد. در طي دوره مورد مطالعه، تخريب اراضي به صورت تبديل كاربريهاي باغ و اراضي كشاورزي به اراضي مسكوني و صنعتي ديده مي‌شود.

More than one-third of land in the world is located in the areas with arid and semiarid climate and desertification has increased in these areas during recent decades. Around 80% of Iran is located in arid and semiarid areas. Sand dunes as an indicator of desert land cover an area about 32 million hectare. Among which 12-mil hectare has not been stabilized yet. Advancing moving sand dunes has resulted in much damage to agricultural products and urban areas. In this survey satellite images and aerial photos are used to evaluate the role of land use changes on desertification in 1955, 1997 and 2002. To do so, IRS image of 2002 and available aerials photos of 1955 and 1997 are used. Following making the aerial photos mosaic processing was done using ILWIS software and needed data completed by field surveying and the land use map was produced for two years. To produce the land use map using digital processing methods 10 sample set (training points) were selected uniformly in the area. After preprocessing including geometric corrections, image enhancement and band composition, image classification was done by maximum likelihood method and the land use map was produced. In this phase, obtained land use map was corresponded to the ground truth map which was achieved by field surveying and recording coordinate of points with GPS pixel to pixel and accuracy obtained from numerical classification estimated to be 45.3%. Then due to obtained low accuracy, the visual method used to produce the land use map so the accuracy of 78.5% achieved. Finally, the area of each land use and the rate of changes were calculated. The results indicate a decrease of 2000 ha in the area of the desert land from 1955 to 1997 and of 160 ha from 1997 to 2002 and an increase in the area of the other land uses. Results show no desertification in the study area, even though land degradation can obviously be identified in the area, which is resulted from the changes of gardens, and agricultural land uses to industrial and urban areas.