Remote sensing for forestry: assessing tree stress and climate-induced changes in the Vrsac Mountains
DOI:
https://doi.org/10.59463/33m76a81Keywords:
vegetation indices, satellite images, drought, mixed stand forest, forest environmentsAbstract
The forests of the Vrsac Mountains, located in the southeastern part of the Pannonian Plain, represent a unique ecological system within an otherwise predominantly agricultural landscape. The dominant tree species are sessile oak (Quercus petraea [Matt.] Liebl). Increasing climatic variability, particularly rising temperatures and prolonged drought periods, has begun to alter forest dynamics, raising concerns about their long-term resilience.
This study assesses drought-induced stress in the mixed forest ecosystems of the Vrsac Mountains using remote sensing data from the years 2023 and 2024. To evaluate the condition of forest vegetation and detect drought-induced stress, four vegetation indices were used in this study: Enhanced Vegetation Index (EVI), Triangular Vegetation Index (TVI), Moisture Stress Index (MSI), and Normalized Difference Moisture Index (NDMI). Each of these indices provides specific insights into different aspects of vegetation vitality, canopy structure, and moisture availability, making them highly suitable for use in forest environments, especially in complex and heterogeneous mixed stands.
Results indicate a dramatic increase in the percentage of forest area affected by drought in 2024 compared to 2023. In 2024, 39.16% of the forested surface showed signs of stress according to EVI, 46.9% according to TVI, 41.57% based on MSI, and 44.2% based on NDMI. In contrast, the same indices showed minimal stress in 2023: 0.37% (EVI), 0.69% (TVI), 0.61% (MSI), and 0.6% (NDMI). The sharp contrast between the two years is attributed to significantly reduced precipitation and above-average temperatures during the summer of 2024, especially in June and July. These climatic conditions intensified water stress and contributed to canopy thinning, leaf discoloration, and chlorophyll degradation. Among the indices, TVI and NDMI proved to be the most sensitive in capturing early vegetation response to drought.
These findings underscore the growing susceptibility of forest ecosystems in the Vrsac Mountains to climate extremes. The use of vegetation indices in drought monitoring enables spatially explicit assessments of vegetation stress and can support early warning systems, forest management planning, and long-term climate adaptation strategies.
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