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Modelling the spatial distribution of tree mortality with UAV to assess the drivers of forest degradation : A case study for Calabrian pine forest ins West Crete

Swarge, Nilay (2022) Modelling the spatial distribution of tree mortality with UAV to assess the drivers of forest degradation : A case study for Calabrian pine forest ins West Crete.

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Abstract:	Forests are a critical part of the global ecosystem. From subalpine to tropical regions, forests cover nearly one-third of the earth’s land surface. Forests are generally known as the “lungs of the planet” as they absorb carbon dioxide and release oxygen in the air. Forests worldwide are suffering negative impacts from climate change-related droughts. Calabrian pines (Pinus brutia) form forest in the driest parts of the Mediterranean region exposed to long dry seasons. In addition to drought, multiple other factors are potential causes of stress to pine trees leading to their mortality. However, spatial patterns of tree mortality are not uniform. When multiple factors are in place, the patterns of tree mortality on the landscape level could reveal its drivers. To identify the mortality drivers in Pinus brutia assessment of topographical variables is important as they influence the tree mortality on a local level. However, the ranking of topographic drivers in order of their influence on tree mortality is unknown. Thus, finding out the most influencing topographical driver on tree mortality was the main objective of this study. Additionally, during the field work, it was observed that the mortality in large-sized trees was more than in small-sized trees. Thus, analysing the effect of tree size on tree mortality was also one of the objectives of this study. Until now, the research on identifying influential drivers of tree mortality has mostly been done using statistical modelling and data was collected using traditional field methods and satellite or aerial images. To further improve the knowledge about tree mortality, this study uses the data collected from UAV and field observation in the Mediterranean forest, Crete Island, Greece. The analysis was done using GLM and RF models to identify the topographical mortality drivers from the study area. Analysis was performed on two levels, individual tree mortality; focusing on the relationship between tree size and tree mortality and plot-level mortality; focusing on tree mortality percentage in the study area. This study shows a positive relationship between tree size and tree mortality. Additionally, tree density is also influencing tree mortality percentage in the region. Out of all the topographic variables considered, the slope showed a positive influence on tree mortality. Furthermore, elevation reduces the probability of tree mortality percentage for trees situated at a higher elevation.
Item Type:	Essay (Master)
Faculty:	ITC: Faculty of Geo-information Science and Earth Observation
Programme:	Geoinformation Science and Earth Observation MSc (75014)
Link to this item:	https://purl.utwente.nl/essays/107671
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