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    Evaluating the Soil Properties of Different Land Use Types in the Deviskel Watershed in the Hilly Region of Northeast Türkiye
    (Mdpi, 2024) Yuksel, Esin Erdogan; Yavuz, Gokhan
    Land use is a remarkable human-induced change that has redesigned the Earth's surface since the beginning of civilization. Due to the combination of rugged terrain and low-income levels in rural areas, people in watershed regions often resort to overexploiting forests, agricultural land, and grasslands beyond their capacity. As a result of these spatio-temporal changes in land use, various soil properties undergo changes. This study aims to determine the changes in some physical (texture, bulk weight, particle density, total porosity), hydro-physical (water holding capacity, permeability, field capacity, wilting point), physico-chemical (organic matter, pH, electrical conductivity), and erodibility (dispersion ratio, colloid-moisture equivalent ratio, erosion ratio, clay ratio, aggregate stability and K-factor of Universal Soil Loss Equation-USLE) properties of soil depending on land use in the Deviskel Watershed in the city of Artvin in T & uuml;rkiye. For this purpose, disturbed (composite) and undisturbed (cylinder) soil samples were taken from a 0 to 20 cm depth at 108 different points in the determined areas (36 from forests, 36 from agricultural areas, and 36 from grassland areas). It was determined that 15 of the 19 soil properties examined showed statistical differences depending on the change in land use. All the examined soil properties, except for clay content, particle density, dispersion ratio, and aggregate stability, were found to be statistically significantly affected by the change in land use, and the reasons behind these changes were discussed. The particle density had the lowest coefficient of variation value (15.26%) while electrical conductivity had the highest coefficient of variation value (91.25%). According to erosion tendencies, all watershed soils were found to be susceptible to erosion. The average aggregate stability was 88.52% in forest soils, 84.84% in agricultural soils, and 85.48% in grassland soils. The average USLE-K factor was determined to be 0.22 for forests, while it was determined to be 0.17 and 0.18 for agriculture and grassland areas, respectively. According to the USLE-K factor, 68.37% of the watershed was dominated by moderately erodible soils, while 31.63% consisted of highly erodible soils. Based on the colloid-moisture equivalent ratio, erosion ratio, and clay ratio, which are statistically different erodibility features, the grassland soils of the research area were found to be more susceptible to erosion than forest and agricultural soils. In terms of aggregate stability, which indicates resistance to water erosion, forest areas had higher values, while agricultural lands were more prone to erosion.
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    Spatio-Temporal Analysis of Erosion Risk Assessment Using GIS-Based AHP Method: A Case Study of Doğancı Dam Watershed in Bursa (Türkiye)
    (Mdpi, 2024) Yuksel, Esin Erdogan; Karan, Omer Faruk; Akay, Abdullah Emin
    Soil erosion, one of the most serious phenomena in watershed management, can be estimated based on various criteria. Land use change is one of the most important factors affecting the susceptibility of soil erosion. In this study, the effect of land use change on soil erosion risk in two plan periods (2005 and 2017) was investigated using Analytical Hierarchy Process (AHP) and Geographic Information Systems (GIS) for the forest planning units in the Do & gbreve;anc & imath; Dam Watershed, located in Bursa, T & uuml;rkiye. Eight criteria were evaluated including erosion-related slope, bedrock type, land use/land cover, precipitation, relative relief, aspect, drainage frequency, and density. According to the results, the most effective factor in soil erosion was slope (0.29), while bedrock type and land use/land cover ranked second with 0.19. It was found that full closure forests were characterized by high erosion resistance (0.3), while bare land was characterized as the most sensitive area to erosion (0.39). In terms of spatio-temporal changes in a 12-year period, the areas in the medium and high erosion risk decreased, while low and very low-risk areas increased. The ROC method showed a satisfactory accuracy of 72.8% and 80.2% for the 2005 and 2017 erosion risk maps, respectively.
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    The impacts of human-induced disturbances on spatial and temporal stream water quality variations in mountainous terrain: A case study of Borcka Dam Watershed
    (Cell Press, 2023) Ozalp, Mehmet; Yildirimer, Saim; Yuksel, Esin Erdogan
    Unaltered watersheds with natural vegetation cover (forest, grasslands, etc.) provide several ecological benefits in addition to providing freshwater, controlling water levels, and supporting flourishing streamside ecosystems. However, as in many watersheds in the World, the research area in this study, the Borcka Dam Watershed (BDW), has been affected by many human-induced disturbances affecting a wide area of forest and grassland areas as well as soil and water resources. Therefore, the objective of this study was to assess and evaluate the possible effects of anthropogenic disturbances, particularly on annual changes in water discharge, some water quality parameters, and total suspended sediment (TSS) amounts in the main streams of four sub watersheds (Fabrika, Godrahav, Hatila, and Murgul) and the reservoir of the dam. In addition, we intend to confirm that land use change and/or transformation play a significant role in influencing stream water quality. The YSI/Professional-Plus, a portable water quality measurement device, was used to determine the amounts of pH, dissolved oxygen (DO), total dissolved substance (TDS), ammonium (NH4-N), nitrate (NO3-N), salinity, electrical conductivity (EC), and temperature besides measuring discharge and total suspended sediments (TSS) from a total of 27 sampling points in the field. Although the results revealed that the annual mean values of all water quality parameters for all four streams were mostly in good condition, for some time and points of the measurements, several parameters were found to be above the official water quality standards due to the intensive aforementioned anthropogenic activities, particularly in the stream waters of Murgul (e.g. pH and TSS being 10,84 and 236 mg/L, respectively) and Fabrika (e.g. EC of 412 & mu;s/cm; DO of 4.44 mg/L; 14 ml of NO3-N) sub-watersheds. These outcomes indicate that these two sub-watersheds have been impacted more severely by the human-induced disturbances compared to Hatila and Godrahav sub-watersheds.