LEE- Yer Sistem Bilimi Lisansüstü Programı

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http://hdl.handle.net/11527/19499

Gözat

Yazar "Dalfes, Nüzhet H." ile LEE- Yer Sistem Bilimi Lisansüstü Programı'a göz atma
  • Öge
    Pollen-based quantitative reconstruction of vegetation cover in Turkey
    (Graduate School, 2024-06-27) Erdoğmuş Ergin, Esra ; Dalfes, Nüzhet H. ; 601172001 ; Earth System Science
    Vegetation is a critical component of the climate system that influences and is influenced by climate through physical and chemical processes. Vegetation affects regional and local climate dynamics by contributing to energy and water vapor exchanges and is also affected by these dynamics. Incorporating vegetation into climate models improves the accuracy of global climate change predictions. Paleoecological and paleoclimate data provide insights into historical vegetation, land use, and climate patterns, helping us understand long-term changes. Fossil pollen data preserved in lakes, peatlands, and marshes are essential for reconstructing and understanding vegetation dynamics. However, interpreting pollen data is limited due to the non-linear relationships between pollen percentages and plant abundances. Taxonomic differences in pollen production, dispersal and deposition, changes in the spatial structure of vegetation, and differences in the size and type of the sediment basin are not considered in traditional pollen analysis methods. Additionally, before interpreting a pollen record, it is necessary to have an idea about the pollen source area of the studied site. Therefore, model-based methods play an essential role in correcting for factors that influence pollen representation of vegetation and in linearizing the pollen-vegetation relationship. The Landscape Reconstruction Algorithm (LRA) quantitatively reconstructs vegetation abundance at regional and local scales using fossil pollen counts. The REVEALS model, a part of the LRA, reconstructs past vegetation cover based on pollen data and relies on Relative Pollen Productivity estimates (RPP) and pollen fall speed values (FSP). Although the REVEALS model has been applied in various regions, its use in the Mediterranean is limited due to the lack of region-specific RPP values. The primary objective of this thesis is to understand the vegetation dynamics of southwestern Turkey during the late glacial period and the Holocene. To achieve this goal, the study aims first to acquire RPP values for Turkey and then to conduct quantitative vegetation reconstructions in southwestern Turkey using the REVEALS model. Studies on Holocene vegetation changes in southwestern Anatolia indicate increased human activities such as agriculture, grazing, and fires. Lake Gölhisar is located in southwestern Turkey with its rich palynological and archaeological evidence of human-induced vegetation changes. This study focuses on a 50 km radius around Lake Gölhisar in the Oro-Mediterranean vegetation zone. This area includes forests of Pinus brutia, Pinus nigra, and Juniperus, high mountain steppes, and Quercus coccifera shrublands. Sampling sites were randomly selected within a 50 km radius using QGIS software, ensuring a minimum distance of 1500 m between each location to prevent autocorrelation. Moss samples were collected from 21 accessible sites, and vegetation surveys were conducted within a 100 m radius of each site. These data were used to create land cover maps for distances up to 5000 m, and pollen extraction from moss samples was performed according to standard procedures. The ERV model was applied to estimate RPPs for different plant taxa by focusing on species well represented in both vegetation and pollen samples. Specific pollen types were selected for analysis, with Quercus coccifera used as the reference taxon. The RSAP was determined to be 102 m. Five taxa, including Q. coccifera, Juniperus, Fabaceae, Pinus, and Poaceae, were used for the final analysis, and RPP values were produced for these taxa. In the second part of the study, the REVEALS model was used with the produced RPP values. The study focused on the Oro-Mediterranean vegetation zone and utilized fossil pollen data from the Neotoma Paleoecology Database. Fossil pollen data were converted into REVEALS input files, and the model was run using the RPP values. Results indicated that some taxa not well represented in pollen proportions were better captured by the REVEALS model. This highlights the model's ability to provide a more comprehensive and accurate reconstruction of vegetation by compensating for biases and limitations in raw pollen data. By integrating all available records and using the Mediterranean taxa set, the REVEALS model offers a robust framework for understanding past vegetation dynamics, even in the presence of time gaps and varying pollen counts. Throughout the Holocene, human activities and climate changes in southwestern Anatolia have led to significant changes in vegetation structure. Agriculture, grazing, and fires have greatly influenced vegetation dynamics in the region. Records obtained from Lakes Gölhisar and Söğüt provide detailed insights into the impact of human activities on vegetation. Pollen analyses show an increase in agricultural activities and deforestation processes, especially during the late Holocene. The REVEALS model quantitatively evaluates these impacts, providing a more accurate reconstruction of past vegetation. Integrating REVEALS-based reconstructions with traditional pollen data offers new insights into the extent and nature of human impact on vegetation over thousands of years. Human activities such as agriculture, grazing, and fires have caused significant changes in vegetation dynamics. These changes can be tracked and analyzed through pollen records. Particularly during the late Holocene, increased agricultural activities and deforestation processes have greatly affected the vegetation structure in the region. This study enhances the understanding of historical vegetation dynamics in southwestern Turkey and underscores the importance of region-specific RPP research for accurate vegetation reconstructions. This comprehensive approach provides a clearer picture of human-induced changes and their long-term effects on biodiversity. Future research, covering a wider geographical area and including more sampling points, could further improve RPP values and contribute to a more detailed understanding of vegetation dynamics. In conclusion, this thesis takes a crucial step in understanding the vegetation dynamics of southwestern Turkey and sheds light on the paleoecological and climatic history of the region. By providing a comprehensive analysis of historical vegetation changes, it helps us understand the long-term effects of human impact. Moreover, these findings contribute to the accuracy and reliability of future climate and vegetation models.