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.
Ali Mohammadian; Esmaeil Asadi Borujeni; Ataollah Ebrahimi; Pejman Tahmasebi; Ali Asghar Naghipour borj
Abstract
Nowadays, using satellite imagery is one of the fastest and lowest-cost methods in rangeland assessment. Also, remote sensing-based vegetation indices are among the most widely used tools to assess and monitor vegetation changes, especially in the post-fire period, and to map the burned regions in rangelands. ...
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Nowadays, using satellite imagery is one of the fastest and lowest-cost methods in rangeland assessment. Also, remote sensing-based vegetation indices are among the most widely used tools to assess and monitor vegetation changes, especially in the post-fire period, and to map the burned regions in rangelands. The present study was conducted considering the importance and extent of rangelands and the recently increased prevalence of fires in the semi-steppe rangelands of Iran, especially in Chaharmahal and Bakhtiari Province. The main objective of this study was to distinguish and identify the burned areas during 1-3 year and 3-5 year periods to adopt an appropriate post-fire management program in these areas using spectral indices. After calculating the spectral indices, the M statistical parameter was determined to designate the separation capability of the burned areas from the adjacent ones. According to the findings, using NBRT, NBR, and CSI indices is recommended to identify and distinguish the burned areas 1-3 years after the fire from the adjacent areas in semi-steppe rangeland regions of Iran. Overall, these indices are of high efficiency in separating these ranges. Moreover, T.C. Brightness and NBRT indices can efficiently identify and separate the burned areas 3-5 years after the fire. Among the studied indices for both periods of fire in the studied semi-steppe rangelands, the NBRT index showed a high potential for identifying the burned area from the adjacent areas.
