Analysis of desertification changes with emphasis on precipitation in Qom province

Desertification after climate changes and deficiency of fresh water is the third important global challenge duringthe 21st century. This phenomenon is the consequence of a series of processes in which climate changeand human activities are more important factors than others. Therefore, recognition and assessment of the desertificationtrend are very important issues for better region management. Hence, the aim of this study is theassessment of desertification changes in Qom province using Landsat satellite images, TM5 and LCDM8 sensorsin(1984-2013) with emphasis on the precipitation. Indicators used in this study are Normalized Difference VegetationIndex (NDVI) and Soil Salinity Index (s1, s2, s3). According to Fuzzy ARTMAP method, the land use duringthe period of (1984-2013) recognized and the land use changes were evaluated based on the Multilayer PerceptronNeural Network (MLP) Model in software TERRSET. To study the effect of precipitation on desertification, themonthly data of GPCC have been used and the spatial-temporal trend of annual precipitation was evaluated usingthe Mann-Kendall nonparametric test at 0.95 level of significance. The results showed that the salinity and thedesert lands have been increased relative to the first year of study period from 3% to 18% and about 15% growth.The vegetation has arrived from 7% to 2% that about was reduced 5%. The greatest increase of saline land is seenin the western part of Qom, which replaces the vegetation. The increasing amount in saline and desert lands isabout 1751 km2. Study of land use changes illustrated that saline lands and city are growing whereas vegetation,Sultan-Houz Lake, Salt Lake, and arid lands are reducing. The analysis of precipitation spatial-temporal trendrevealed a decreasing trend on annual time series at the 0.95 level of significance. Obtained results provide a basisfor better recognition and proper combating desertification in the studied region.