Soil cover of mountainous regions of Uzbekistan changes from 1980-ies to 2020-ies detected by Landsat images

Soil cover changes oftenly result in significant transformation of soil functions, and in some cases in their complete loss and soil degradation, which affects greatly the quality of the environmental conditions and soil services. Thus, studying the processes of soil and soil cover changes in dynamics is of greatest importance. The aim of the research was to identify the trend in longterm dynamics of soil cover in mountainous regions of Uzbekistan for the period from the 1980-ies to the 2020-ies through the analysis of multitemporal satellite data. The analysis was carried out for regions of Uzbekistan with an absolute altitude of more than 900 meters above sea level. Soil cover changes were identified by means of the analysis of Landsat TM5 satellite data (29 scenes) for 1985–1987 period and Landsat 8 OLI (32 scenes) for 2021– 2023 one. Based on the NDVI threshold values, individually determined for each scene, all images were divided into 3 land cover classes: vegetation cover, open soil surface and water surface. After that, channel-by-channel subtraction of the brightness values in each channel was carried out for both survey periods. The results were expertly interpreted in terms of soil changes. The developed map of soil cover changes was superposed over the updated geoinformation map of the soil cover of the mountainous regions of Uzbekistan. The main types of the found changes are associated with erosion processes, scree, rockfalls, secondary waterlogging and salinization of soils. These changes affect about 7% of the mountainous territory of the country for the period under study. A trend towards soil progradation is observed for 4% of the mountainous territory of Uzbekistan. Changes in the soil cover due to the dynamics of the water surface (flooding of soils, exposure of the soil surface after the water level in reservoirs has dropped or instead of intermittent water bodies) in the study area are observed on 0.1–0.3% of the mountain area. The conducted studies have shown the wide possibilities of using longterm archives of satellite data to assess the dynamics of soils and soil cover in hard-to-reach mountainous regions of Uzbekistan.

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