Mehran Fatemi; Atefeh Jebali; Asghar Zare Chahouki
Abstract
Salt playas in arid regions are unique and sensitive ecosystems, playing a crucial role in environmental balance and ecological sustainability. This study aimed to evaluate the geomorphological change trends in the Abarkouh salt playa by employing advanced remote sensing techniques within the Google ...
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Salt playas in arid regions are unique and sensitive ecosystems, playing a crucial role in environmental balance and ecological sustainability. This study aimed to evaluate the geomorphological change trends in the Abarkouh salt playa by employing advanced remote sensing techniques within the Google Earth Engine (GEE) platform. The research monitored geomorphological facies and environmental changes in the playa from 2002 to 2024 using Landsat 5 and 8 satellite imagery. Spectral indices for vegetation (NDVI, SAVI, EVI, and TSAVI), water (MNDWI), soil moisture (NDMI), and soil salinity (SI) were analyzed to assess these changes. The results reveal substantial geomorphological alterations in the playa over the study period. Specifically, water bodies and vegetation cover decreased by approximately 65% and 51%, respectively, from the initial year, while saline, clay, and sandy lands expanded by about 23%, 66%, and 103%. Spectral index analyses further indicated a significant decline in water levels and a significant rise in soil salinity, both at the 1% and 5% significance levels, respectively. Notably, a key finding of this study is the contradiction between the spectral indices and the classification maps. Despite a significant upward trend in all vegetation indices, the classification maps consistently showed a decrease in vegetation cover. This discrepancy highlights that in this arid environment, the vegetation indices are influenced by the spectral reflectance of salt and gypsum rather than actual vegetation, leading to a false positive signal. The study concludes that the boundaries of geomorphological facies within the Abarkouh salt playa have undergone significant changes, largely driven by drought and human activities.
Mohammad Ali Saremi Naeini
Abstract
Rapid population growth and the need to provide the necessities of life has caused human beings to change land use widely. In many cases these changes have been accompanied by disruption of balance in nature and providing the possibility of soil erosion. This study was carried out to investigate the ...
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Rapid population growth and the need to provide the necessities of life has caused human beings to change land use widely. In many cases these changes have been accompanied by disruption of balance in nature and providing the possibility of soil erosion. This study was carried out to investigate the effect of land use changes on increasing the intensity of wind erosion. Landsat satellite imagery and implementation of supervised classification by using SVMs were used to prepare land use map. Ground surface temperature was calculated, as one of the effective factors in wind formation, with single channel and split window algorithms in different land uses. In order to make connections between land use changes and wind erosion, effective climatic parameters such as temperature, relative humidity and maximum wind speed were investigated. The highest surface temperature was observed in poor and non-vegetation areas, and the lowest temperature was estimated in highlands and rangelands. Results showed an increase in average temperature as well as maximum and minimum absolute temperature and decrease in relative humidity. Over the past decade, the maximum wind speed in the study area showed a significant increase, and it has increased from eight m/s in 1990 to more than 20 m/s in the last decade. This shows that land use change by removing vegetation cover, as well as the uncontrolled increase of human constructions and creating thermal islands in the last 30 years, has a significant impact on the emergence of climate change and increasing wind speed.
