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Sentinel-2 satellite-based analysis of bark beetle damage in Sopron Mountains, Hungary
33-40Views:190Sopron mountains were affected by bark beetle (Ips typographus) damage between 2017 and 2020, which was surveyed on high-resolution ESA Sentinel-2 satellite images for the period 2017 and 2020 using Mosaic Hub, Anaconda, and Jupyter Notebook web-based computing environments. Biotic forest damage was detected based on vegetation (NDVI) and moisture (MSI, NDWI) indices derived from satellite images. The spatial and temporal change of damage was observed in the image series, resulting in information about the level of degradation and regeneration. In pursuance of GIS processing, 84 forest compartments were compared, which showed in most of the cases (97%) negative interannual change in the index mean values (MSI = - 0.14, NDWI = - 0.2, NDVI= - 0.19) when years compared to each other. The remote sensing-based survey was marked out and validated based on the forest database of the Hungarian Division of Forest of National Land Centre and forest protection damage reports of the Hungarian National Forest Damage Registration System.
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Above ground forest biomass distribution in the landscape of Jorhat, Assam, India
16-31Views:52This study aims to analyze the spatial and temporal variations in above-ground biomass (AGB) within the Jorhat region from 2001 to 2023. It also highlights the impacts of urbanization, physiographic characteristics, and soil types on AGB variation. In order to accurately assess landscape-level variation of biomass, a combination of field surveys, remote sensing techniques, and modelling approaches are employed in this study. Biomass estimation is difficult over large area using traditional method. The synoptic nature of satellite-based data improves the monitoring of inaccessible areas. Results show approximately 16.6% decrease in AGB, with urban and peripheral areas experiencing the most notable declines due to reduced forest cover. Physiographic analysis reveals low AGB values in marshes (13 t/ha), swamps (14 t/ha), and char lands (25 t/ha). The growth of trees is suppressed seasonal flooding in this physiography. Additionally, AGB follows an increasing trend from North to South, in alignment with the region’s elevation profile. Soils also exhibit variations in AGB, with alluvial soils supporting higher biomass compared to other soil types. Key ecological linkages and spatial patterns are highlighted in this study, laying the groundwork for more proactive and comprehensive environmental management. Finally, in a time of fast environmental change, these insights can assist stakeholders and policymakers
in creating more evidence-based, flexible solutions to protect ecosystems. -
Specific features of NDVI, NDWI and MNDWI as reflected in land cover categories
194-202Views:2303The remote sensing techniques provide a great possibility to analyze the environmental processes in local or global scale. Landsat images with their 30 m resolution are suitable among others for landcover mapping and change monitoring. In this study three spectral indices (NDVI, NDWI, MNDWI) were investigated from the aspect of land cover types: water body (W); plough land (PL); forest (F); vineyard (V); grassland (GL) and built-up areas (BU) using Landsat-7 ETM+ data. The range, the dissimilarities and the correlation of spectral indices were examined. In BU – GL – F categories similar NDVI values were calculated, but the other land cover types differed significantly. The water related indices (NDWI, MNDWI) were more effective (especially the MNDWI) to enhance water features, but the values of other categories ranged from narrower interval. Weak correlation were found among the indices due to the differences caused by the water land cover class. Statistically, most land cover types differed from each other, but in several cases similarities can be found when delineating vegetation with various water content. MNDWI was found as the most effective in highlighting water bodies.