Andrey Stoyanov

Bulgarian Academy of Sciences

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Теmenuzhka Spasova

Space Research and Technology Institute

Daniela Avetisyan

Space Research and Technology Institute

Borislav Naumov

Bulgarian Academy of Sciences

Nikolay Tzankov

Bulgarian Academy of Sciences

Georgi Popgeorgiev

National Museum of Natural History

Yurii V. Kornilev

National Museum of Natural History

Kameliya Radeva

Space Research and Technology Institute

Iliyana Gigova

Space Research and Technology Institute

Emiliya Velizarova

Swiss Federal Institute for Forest, Snow and Landscape Research

Ivo Ivanchev

South-West University "Neofit Rilski"

Cooperative Institutions

Bulgarian Academy of Sciences

Space Research and Technology Institute

National Museum of Natural History

Institute of Biodiversity and Ecosystem Research

University of Vienna

Bulgarian Society for the Protection of Birds

Sofia University "St. Kliment Ohridski"

Swiss Federal Institute for Forest, Snow and Landscape Research

Ministry of Environment and Water

Bulgarian Food Safety Agency

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First survey on the invasive Pond slider (Trachemys scripta) in Bulgaria: historic development and current situation

Nikolay Tzankov Georgi Popgeorgiev Yurii V. Kornilev Nikolay Natchev Andrey Stoyanov

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Citations (1)

Seasonal assessment of the dynamics of sea ice based on aerospace data on Livingston Island, New Shetland Islands in Antarctica and Longyearbyen in the Arctic

Теmenuzhka Spasova Roumen Nedkov Adlin Dancheva Andrey Stoyanov Iva Ivanova

Sea ice plays a major role in our planet’s climate. It’ acts as a reflector of solar energy, mainly in spring and summer. Sea ice covered with fresh snow can reflect 75-90% of solar energy, the open sea reflects just 5-15%. Sea ice acts as an insulator in autumn and winter. This insulating effect limits the amount of both heat and moisture the ocean loses to the atmosphere. The declining sea ice disrupts the climate, societies and fauna of Polar areas, but encourages the econcmic and industrial development. The relevance of this study is related to current trends in the use of remote sensing in solving problems of a different nature in environmental monitoring. The sea ice was analyzed and mapped according to the European Space Agency data (ESA), acquired by sensors of Sentinel-1 SAR (Synthetic Aperture Radar), Sentinel- 2MSI (Multi Spectral Instrument), Sentinel- 3 and GIS. The subject of the study is to demonstrate the dynamics, during the summer season from 2015 to 2019, around the coastline of Livingston Island, New Shetland Islands in Antarctica and Longyearbyen in the Arctic. Changes in environmental objects are indicated by radar images through different processing approaches. The results clearly show that sea ice melting can be best recorded by using SAR data through the C-band. The results obtained are data in the form of thematic maps showing the spatial reflectance of sea ice and its dynamics over time.

Sea ice concentration

10.1117/12.2570829

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Application of remote sensing techniques for monitoring of the climatic parameters in forest fire vulnerable regions in Bulgaria

Emiliya Velizarova Roumen Nedkov Daniela Avetisyan Kameliya Radeva Andrey Stoyanov

Forest fires are among the most dangerous natural threats that cause significant changes in forest ecosystems. For the better management of the wildfire-prone territories, the fire weather components like temperature, precipitation and evapotranspiration predictions and monitoring within the extreme fire seasons are of great importance. Remote sensing has been identified as an effective tool for better understanding how forest ecosystems respond to these components. Respective spectral indices, like Normalized difference greenness indices (NDGI), Normalized Difference Vegetation Index (NDVI), Improved Modified Chlorophyll Adsorption Ratio Index (MCARI2) and Moisture Stress Index (MSI), derived from remote sensing methods (satellite data from different sensors - Landsat and Sentinel) as well as the Geographical Information System (GIS) were applied for the monitoring of the climatic parameters in forest fire vulnerable regions in Bulgaria. The climatic parameters dataset from 2008 consisting of the ten-day period mean temperature and precipitation data were collected. The NDVI trends for the studied periods exhibited significant correlations with the mean precipitation and weak or no correlation with the temperature recorded. These results are largely linked to the relative air humidity. Different vegetation types were found to show distinct spatial responses to climatic changes.

10.1117/12.2533656

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Updated distribution and species composition of the amphibians and reptiles along the Lower Danube, Bulgaria

ARPHA Conference Abstracts (2019)

Georgi Popgeorgiev Borislav Naumov Yurii V. Kornilev Vladislav Vergilov Miroslav Slavchev

In a recently published paper (Popgeorgiev et al. 2019), we compiled for the first time published and unpublished data on localities of the herpetofaunal species observed up to ca. 10 km south of the Bulgarian Danube River. Overall, we identified 687 published records belonging to 62 cells of the 10×10 km MGRS grid. Another 1918 records with real coordinates of our unpublished data from the past ca. 13 years belong to 1269 cells of the 1×1 MGRS grid. As a result, 34 native species – 15 amphibians (4 salamanders and 11 frogs) and 19 reptiles (1 turtle, 2 tortoises, 8 lizards and 8 snakes), and one invasive turtle, have been recorded; further species findings are unlikely. This study further identifies areas that are under-sampled and species such as Pelophylax lessonae that are cryptic. Our data are especially relevant concerning the high economic incentives to change the hydrology of the Danube, which will likely negatively impact the biodiversity along the river and its surrounding.

Species distribution

10.3897/aca.2.e46571

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Post-fire forest disturbance monitoring using remote sensing data and spectral indices

Emiliya Velizarova Kameliya Radeva Andrey Stoyanov Nikolai Georgiev Iliyana Gigova

Wildfires are recurring in many terrestrial ecosystems all over the world. Accurate assessment of the forest ecosystem, affected by fire is of great importance for the fires spread predicting and modelling of the post-fire activities for recovery of the affected territories. High spatial and spectral resolution satellite data were used to evaluate the vegetation variation on a fire-affected territory, located on the northwest slopes of the Rila mountain, considering its spatial heterogeneity. The forest fire was spread on the area of deciduous forests Turkey oak (Quercus cerris L.), and coniferous: Scots pine (Pinus sylvestris L.) and European larch (Larix desidua, Mill.). Different spectral indices like Disturbance index (DI), Normalized difference greenness indices (NDGI) and Normalized Difference Vegetation Index (NDVI) and derived from remote sensing methods (satellite data from different sensors Landsat and Sentinel) as well as the Geographical Information System (GIS) were applied for the forest disturbance assessment in two periods after forest fire occurrence. The results of the applied integrated model provide a quantitative information about the fire effects for distinct forest types. The documented spatial distribution of the territory based on the obtained DI values shows clear differences between the fire-affected forest types, thus demonstrating the usefulness and accuracy of the approach followed.

Scots pine

10.1117/12.2533709

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Assessment of elevation and slope exposure impact on snow cover distribution in the mountainous region in Bulgaria using Sentinel-2 satellite data

Daniela Avetisyan Andrey Stoyanov

Snow cover is among the most important features of the Earth's surface and a crucial element of the cryosphere that affects the global energy balance, water, and carbon cycles. Accurate monitoring of this land surface component is of particular significance as snowmelt provides between 50%–80% of the annual runoff in the temperate (boreal) regions and significantly impacts the hydrological balance during the warm season. Limited reserves of soil moisture during the winter period can lead to all types of droughts, including green-water drought, which is expressed by reduced water storage in soil and vegetation. Green-water drought causes a variable effect across landscape components, on the functions and ecosystem services (ES) they provide. The present study aims to track the snow cover dynamics in the transitional seasons of the year when the snow cover is most unstable and to differentiate its territorial distribution depending on elevation and slope exposure. The study area covers the mountainous territories of Bulgaria and the seasons from 2016 to 2022. To achieve the aim of the study, we used Sentinel-2 images and calculated the Snow Water Index (SWI). SWI uses spectral characteristics of the visible, shortwave infrared (SWIR), and near-infrared (NIR) bands to distinguish snow and ice pixels from other pixels, including water bodies which is crucial for the accurate monitoring of snow cover dynamics. The obtained results were validated using VHR images for pre-selected test areas.

Snowmelt

Land Cover

Water balance

Elevation (ballistics)

10.1117/12.2679770

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Registered high mortality of allochthon Red-eared Sliders (Trachemys scripta elegans) in an artificial pond in Sofia, Bulgaria

Andrey Stoyanov

Allochthon

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Monitoring and spatial-temporal analysis of Stryama river flood event, Karlovo municipality, Bulgaria, occurred on 02.09.2022 by the methods of remote sensing

Andrey Stoyanov

The aim of the study is to present results derived from monitoring the flood event on river Stryama, located in Karlovo municipality, Bulgaria occurred on 02.09.2022 due to extreme intensive rainfalls. During the flood event the rainfall had increased up to 250 l/m², and the water level of the Stryama River in some regions had reached up to 3 meters in 8 hours. Stryama river is situated in central Bulgaria, Plovdiv district, it springs up from Stara planina mountain and its length is 110 km. The applied methodology in the following survey includes use of Sentinel-2 MSI optical data and Tasseled Cap Transformation (TCT) of selected satellite imagery for change detection and estimating the territorial extent of areas affected by the flood waters. Satellite imagery of different temporal points were chosen before and after the flood event in order to track the water dynamics around the riverbed. The calculation of the spatial and temporal characteristics of the river waters were accomplished by segmenting of Sentinel-2 multispectral imagery. The application of the matrix for Tasseled Cap Transformation segments the optical images in 3 components: TCT-brightness, TCT-wetness, TCT-greenness. On the basis of TCT-wetness component and its values the dynamics and territorial distribution of river waters were monitored for the chosen temporal period. On the basis of TCT-greenness component and Normalized Differential Greenness Index (NDGI) an assessment of the impact of flood waters on the vegetated areas was made.

Aerial photos

10.1117/12.2684415

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Prvo istraživanje invazivne crvenouhe kornjače (Trachemys scripta) u Bugarskoj: povijesni razvoj i trenutno stanje

Nikolay Tzankov Georgi Popgeorgiev Yurii V. Kornilev Nikolay Natchev Andrey Stoyanov

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Snow cover mapping based on a multi-index technique in Vitosha, Pirin and Rila mountains

Теmenuzhka Spasova Daniela Avetisyan Andrey Stoyanov

10.1117/12.3031481

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