Date

2021-9-10

Author

Bilgin, Gelincik Deniz

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Alpine treeline ecotone (ATE) is the transition zones between forests and alpine grasslands. Because of its ecological importance due to its unique biodiversity, understanding the characteristics of the transition zone is essential. Recent climate change research has shown that the ATE tends to shift upwards. Understanding this upward shift enables the development of climate change indicators for mountain ecosystems and provides insight into efforts towards improving adaptation and mitigation measures. This thesis aims to develop and apply a methodology for objectively defining and delineating a tree line that is also ecologically meaningful. Another aim is to reveal the shift in ATE for a study area in which this altitudinal shift is expected to have been substantial in the last decades. Within this context, the factors that determine the spatial configuration of the ATE have been investigated through the use of remotely sensed resources. The study area is in the Western Taurus Mountains, located in the Mediterranean region of Turkey. An algorithm with four steps has been developed to delineate treeline for any given time during the study period, using Landsat images of the relevant years. For each step, the methodology was chosen with the aim of minimising the need for human interpretation as much as possible and for developing a reproducible method. These steps include obtaining cloud-free seasonal composites from Landsat images, determining tree percentages over the area through spectro-temporal unmixing, and characterising the transition of ATE through fitting a sigmoid response to tree percentages along uphill transects, and modelling of the ATE transition using Random Forest Regression. Applying this algorithm has revealed that topographical variables combined with information on the percentage of canopy cover can be used effectively while modelling treeline ecotones. Outcomes of the model indicate a downward shift of the treeline on west face of the Dedegöl Mountain for some slopes since 1984, against theoretical expectations or contrary to observations of increases elsewhere in the world. However, on eastern slopes, the shift is indicated to be upwards. This study can provide input for estimating future shifts in ATE and for further development of models for various climates and latitudes. Also, the algorithm can easily be adapted to other satellite data, thus enabling higher resolution outcomes.

Subject Keywords

Alpine Treeline Ecotone, Treeline, Landsat, Treeline Dynamics, Spatio-temporal Analysis

URI

https://hdl.handle.net/11511/94328

Collections

Graduate School of Natural and Applied Sciences, Thesis