DOI: 10.3897/jbgs.e185535

Authors: Saleh Eddine Zahli

Abstract: Soil erosion and sediment transport represent major environmental challenges in semi-arid Mediterranean watersheds, where high erosion rates do not necessarily translate into high sediment delivery to river systems. This study assesses sediment regulation ecosystem services in the Nfifikh watershed (Morocco) to clarify how landscape connectivity controls sediment export, retention, and internal buffering processes. A spatially explicit connectivity-based modelling approach was implemented using the InVEST Sediment Delivery Ratio (SDR) model, integrating a 30 m digital elevation model, land use and land cover data (2019), soil properties, and rainfall erosivity factors within a GIS environment. The results reveal a marked decoupling between potential soil erosion and effective sediment transfer. Despite high erosion potential in upstream areas, sediment export remains spatially limited due to reduced connectivity, whereas midstream sectors with moderate erosion exhibit higher sediment delivery efficiency. High SDR values are confined to a limited number of well-connected zones, while large portions of the basin function as sediment sinks. Valley-floor deposition locally exceeds 1100 kg yr-1, under-scoring their buffering capacity. Ecosystem service indicators further show spatial differentiation between avoided soil erosion and avoided sediment export, reflecting the role of land-cover configuration in regulating sediment fluxes. Overall, the findings demonstrate that sediment regulation is primarily governed by landscape connectivity and land-cover structure rather than erosion intensity alone, providing transferable insights for ecosystem-based watershed management in semi-arid Mediterranean environments.

HTML

PDF

DOI: 10.3897/jbgs.e128013

Authors: Melike Durak

Abstract: Kuruçay Stream basin, located in the Edremit district in northwest Turkey, is a small, narrow and long basin with an area of 17.3 km2, extending in the N–S direction, located on the southern slopes of Mount Ida. The study was carried out to determine the soil erosion susceptibility and distribution of Kuruçay Stream basin, as well as to estimate the annual average amount of soil loss through the Revised Universal Soil Loss Equation (RUSLE) model using Geographical Information Systems (GIS). To apply the equation to the basin, data layers for rainfall erosivity (R), soil erodibility (K), slope length (L) and slope steepness (S), landcover management (C), and support practice (P) factors were generated. The layers were then overlaid, calculations were made and erosion susceptibility classes were generated. Thus, the spatial distribution of erosion susceptibility classes and the annual estimated amount of soil loss were determined. Based on the results, the Kuruçay Stream basin was found to have five distinct erosion susceptibility levels: low, moderate, high, severe, and extremely severe. Accordingly, 76% of the basin has low, 11.3% moderate, 6% high, 2.9% severe and finally 3.7% very severe erosion susceptibility. The Kuruçay Stream basin shows similar characteristics with the neighbouring river basins in terms of erosion sensitivity.

HTML

PDF

DOI: 10.3897/jbgs.e101301

Authors: Petar Stefanov, Hristina Prodanova, Dilyana Stefanova, Vanya Stoycheva, Gergana Petkova

Abstract: Karst is a widely spread natural phenomenon which provides essential benefits to human society, such as drinking water. The water cycle in the karst geosystems is the main factor for their formation and at the same time one of the main drivers for ecosystem services (ES) provision. The monitoring of the water cycle can provide valuable information regarding its functioning and ensure data for ES assessment. This paper aims to present an overview of the monitoring of the water cycle in the karst geosystems and the opportunities to integrate the monitoring data into the water regulation ES assessment. The monitoring of the water cycle is based on the methodological framework ProKARSTerra. It is applied in model karst geosystems, which are representative of the main karst types in Bulgaria. One of them is the Brestnitsa karst geosystem, which is the case study of this work. The monitoring ensures data for analyses of the water cycle which can be used in the assessment of water-related ecosystem services. The results from the analyses of the data requirements and availability show that some services such as water flow regulation and regulation of chemical condition of freshwaters can be easily provided through data for quantification, while for others further studies are needed. The results of the long-term integrated monitoring in Brestnitsa karst geosystem provide the foundation for important conclusions and models for the karst genesis and function under global changes and active anthropogenic pressure. Their integration into the assessment framework and mapping of ecosystem services is an essential step towards the development of models for sustainable use of natural resources in the karst areas.

HTML

XML

PDF

DOI: 10.3897/jbgs.e99206

Authors: Zvezdelina Marcheva, Tsvetan Kotsev, Assen Tchorbadjieff, Velimira Stoyanova

Abstract: This study aims to reveal the arsenic dynamics in groundwater of а river floodplain contaminated with mine tailings under temperate climate conditions and natural river hydrodynamics. Arsenic concentrations were monitored in the primary morphological units of the floodplain in the upper stretch of the Ogosta River in NW Bulgaria. Iron, lead-silver, and gold mining heavily affected the river valley in the second half of the 20th century. We used groundwater monitoring data from 21 piezometers for the period 2016-2020. Based on the geochemical and geomorphological conditions in the valley, the piezometers were grouped into three clusters. Regression models were developed for each cluster and representative piezometers to predict arsenic concentrations. In the active floodplain, seasonal fluctuations in arsenic concentrations followed the river and groundwater regime. In this part of the valley floor, we determined two periods of elevated arsenic concentrations during the spring and autumn/winter seasons that coincide with high river water stages. Arsenic content in the groundwater of the higher floodplain was less dependent on the water level fluctuations but followed changes in redox potential, electrical conductivity, and water temperature. The obtained results showed the elaborated models as valuable tools for studying arsenic dynamics in alluvial aquifers of contaminated river floodplains. The suggested models could be coupled with groundwater monitoring systems to monitor arsenic concentrations and identify periods of the year with levels below and above threshold values.

HTML

XML

PDF

DOI: 10.3897/jbgs.e98660

Authors: Petko Bozhkov, Borislav Grigorov, Alexandar Sarafov

Abstract: The present study deals with the investigation of soil organic carbon in two water catchments in Northern Rila, Western Bulgaria. Field research, combined with analysis, provided sufficient data. Six key sites were selected and sampled in order to estimate and compare the amount of organic and inorganic carbon in the topsoil. The applied criteria for the choice of sites included: vegetation cover, predominant soil group, level of anthropogenization and transport accessibility. A total number of 13 samples from both catchments were collected and analyzed in the Central laboratory of the Institute of Soil Science, Agrotechnologies and Plant Protection (ISSAPP) “N. Pushkarov“. The results concern the amount and composition of soil organic matter in different soils – Cambisols (Albic, Humic, Dystric), Fluvisols and Umbrosols. The total carbon content of all samples varies between 1.23 and 9.69%. The amount of organic carbon ranges between 0.45 and 3.73%. The results of the study prove once again that the preservation of natural vegetation and current condition of the soil is of great importance for carbon sequestration and climate change mitigation.

HTML

XML

PDF

DOI: 10.3897/jbgs.e97168

Authors: Tsvetan Kotsev, Velimira Stoyanova

Abstract: The present study aims to determine the spatial distribution of soils with lead (Pb) content above the quality thresholds in a section of the Ogosta River valley (NW Bulgaria). The study area was contaminated with mine waste from the extraction and flotation of iron, lead-silver, and gold-bearing ores in the second half of the XX century. Predictive modeling was performed with the software Maximum Entropy Species Distribution Modeling (MaxEnt), Version 3.4.4, which uses machine learning algorithms and applies the maximum entropy method. The choice of predictors of contaminated soil distribution is consistent with the main factor for Pb dispersal within the valley floor - flooding from the Ogosta River. The following six parameters explained the environmental settings related to the accumulation of contaminated floodplain sediment: vertical distance to the river channel, lateral distance to the Ogosta River, terrain slope, land cover (CORINE Land Cover, 2019), morphographic units of topography, and elevation. The results represent the average values of 10 replicates of the model. We evaluated the individual models by the value of the area under the relative operating characteristic curve (AUC) and the geographic logic of the obtained results. The AUC score for the test samples was 0.666 for the soil group 1 with Pb ≤120 mg/kg, 0.782 for group 2 with Pb (120-500] mg/kg, and 0.934 for group 3 with Pb>500 mg/kg. The most significant predictors for the models are the vertical and lateral distance to the river and the slope of the terrain. Lead concentrations tend to decrease with the distance from the main river and by increasing the elevation above the river channel due to lower inundation frequency and deposition rate of polluted river sediments. The soils with a Pb concentration below the permissible threshold of 120 mg/kg cover more than 58.42% of the valley floor of the studied section, and lands with Pb content above the intervention value of 500 mg/kg occupy nearly 10.82% of the investigated territory. The selected predictors describe the distribution of highly contaminated soils well and define the range of soils with lower Pb content worse. Combining clean and contaminated soil samples into one group is considered the main reason for the poor performance of MaxEnt for soils with Pb ≤120 mg/kg. However, the results prove the model's ability to predict the spatial distribution of not only biological species but also the dispersal of hazardous substances in soil.

HTML

XML

PDF

DOI: 10.3897/jbgs.e94913

Authors: Petko Bozhkov, Borislav Grigorov, Alexandar Sarafov

Abstract: The following paper represents results from a research focused on the soil associations and their corresponding vegetation communities (soil-plant catenas), located on the northern slopes (N, NW, NE) of the Rila Mountains. Data from eight key sites located between 815 and 2041 m above sea level is discussed. The slope in each site varies from 2° to 25°, and most often the tests and descriptions were carried out on sites with a slope of 10-15°. Vegetation cover is analyzed with plant community plots which provides data on species composition, abundance and coverage. The size of each plot varies from 16 up to 225 m2 depending on the vegetation type. Topsoil horizons were tested in each site in order to diagnose the subspecies diversity of brown forest soils (Cambisols) using ratio of humic acids to fulvic acids. That ratio varies from 0,69 up to 1,61 in all studied sites. Both acids are associated with the dominance of different vegetation types – deciduous, mixed or coniferous forest or herbaceous canopy. The results are interrupted in terms of the diagnosis and classification of Cambisols and Umbrosols in the area of interest. Differences in soil and vegetation cover of Northwest and Eastern Rila Mountain are highlighted and analyzed.

HTML

XML

PDF

DOI: 10.3897/jbgs.2018.39.10

Authors: Alexander Peychev

Abstract: The object of the study is separate territory with natural boundaries - the water catchment of the river Struma. Within these limits is digitized (in the environment of GIS) soil map of Bulgaria (S 1:200000). Рolygons of 18 different soil types are established. From large-scale (S 1:10000 and S 1:25000) soil survey of the country is extracted and processed a large database of both characteristics – soil texture and humus content. With generalized data on these characteristics the identified 18 polygons are filled. Two thematic maps are composed. Area distribution of soil (classified according to two studied characteristics) is established.

HTML

PDF

DOI: 10.3897/jbgs.2018.39.4

Authors: Alexandar Sarafov, Emilia Tcherkezova

Abstract: This paper presents the results of soil investigation in the archaeological site 27 near the settlement Kapitan Andreevo (SE Bulgaria). The following soil types are recognized: Fluvisols, Vertisols, Luvisols and Planosols. Their spatial distribution is closely related to the Pliocene facial surface that consists of erosion, abrasion and accumulative deposits in the region and presents a transitional zone in the investigated archaeological area.These circumstances depend on the terrain and climate conditions over thousands of years and have determined the mosaic nature of the three soil types. The results support the archaeological investigation in the study area and were additionally filled with GIS-based analysis of the Digital Terrain Model (DTM) using open software GRASS GIS.

HTML

PDF