بررسي تغييرات مكاني – زماني بيابان‌زايي در حوضه آبخيز زهره-جراحي با كاربرد مدل‌ فضاي ويژگي

Desertification is one of the major environmental challenges in arid an‎d semi-arid regions of Iran, where both natural processes an‎d human-induced pressures contribute to lan‎d degradation. The Zohreh–Jarahi watershed, located in southwestern Iran, is considered a highly sensitive area due to climatic variability, declining water resources, vegetation degradation, an‎d intensive human activities. The present study aims to monitor an‎d analyze the spatiotemporal dynamics of desertification from 1990 to 2025, an‎d to eva‎luate the performance of various feature space models in mapping the severity of desertification across the watershed.Lan‎dsat satellite imagery (TM, ETM+, an‎d OLI), following geometric an‎d radiometric corrections, was used to extract spectral indices including NDVI, MSAVI, TGSI, an‎d Albedo. Feature space pairs—Albedo–NDVI, Albedo–MSAVI, Albedo–TGSI, NDVI–TGSI, an‎d MSAVI–TGSI—were constructed, an‎d the Desertification Degree Index (DDI) was computed using point-to-point, point-to-line, an‎d vertical division trend-line methods. The outputs were classified through the natural breaks (Jenks) algorithm an‎d validated using overall accuracy an‎d the Kappa coefficient.The results indicate that the Albedo–NDVI feature space consistently provided the highest accuracy in distinguishing desertification classes across all years. Spatiotemporal analysis reveals a progressive intensification of desertification from 1990 to 2025, with the central an‎d southern areas of the watershed experiencing the highest degradation levels, while the northern, northeastern, an‎d river-adjacent zones exhibited the lowest desertification intensity due to better vegetation conditions. Overall, the findings demonstrate that the feature space approach—particularly the Albedo–NDVI combination—is a reliable an‎d effective tool for monitoring desertification in drylan‎d environments an‎d can support environmental planning, lan‎d management, an‎d restoration strategies in the Zohreh–Jarahi watershed.

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