LEE- Jeodinamik Lisansüstü Programı

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http://hdl.handle.net/11527/19319

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Yazar "Biltekin, Demet" ile LEE- Jeodinamik Lisansüstü Programı'a göz atma
  • Öge
    Investigation of late holocene period vegetation and climatic changes of Gölbaşi basin based on palynological analysis
    (Graduate School, 2024-06-12) Gökgöz, Dila Doğa ; Biltekin, Demet ; Eriş, Kürşad Kadir ; 602211001 ; Geodynamics
    The Gölbaşı Basin is located in Adıyaman Province, SE Türkiye and there are three lakes within the basin, namely Gölbaşı, Azaplı, and İnekli. This thesis focuses on the palaeoenvironmental and palaeoecological changes in the Gölbaşı Basin which is one of the most important wetlands in southern Anatolia. For the first time, and palaeoenvironmental reconstruction was performed through high-resolution palynological data covering the late Holocene (> 3019 cal years) in the basin. Fossil pollen and non–pollen palynomorphs (NPPs) provide a complementary assessment for environmental monitoring, such as vegetation and climate changes, agricultural preferences, deforestation phases, animal husbandry, land-use change, trophic states of wetlands, and prey–predator relationships in the ecosystem. Scope of this thesis, palynological analyses were performed on two sediment cores obtained from Lakes Gölbaşı (GLB-01) and Azaplı (AZP-03) during the fieldwork of the TÜBİTAK-121Y287 project carried by İTÜ EMCOL Applied Research Centre. Analyses and observations were performed in the microscope laboratory at the Eurasia Institute of Earth Sciences and sedimentology and geochemistry laboratories in the East Mediterranean Centre for Oceanography and Limnology (EMCOL) Applied Research Center. The chronology of the cores was established based on AMS radiocarbon dating. Additionally, 53 species and 13 families were identified within the pollen assemblages, and 83 distinct non–pollen types were classified based on their taxonomic characteristics. According to palynological data, the dominance of cultivated plants, anthropogenic plants, cereal types, mega herbivore indicators, and open vegetation indicator fungal taxa indicates that intense human activity occurred around Lake Gölbaşı and Lake Azaplı during the late Holocene. In the GLB-01 core taken from Lake Gölbaşı, the abundance of Poaceae increased from the upper part of the Glb-1 pollen zone toward the top of the core with slight fluctuations. The presence of cultivated species such as Juglans (walnuts), Olea (olive), and Pistacia (pistachio) indicates agricultural practices in the vicinity of Lake Gölbaşı at 1915 cal years BP. The drastic decrease in the abundance of Cedrus (cedar), which is a relict plant in Anatolia, is probably related to human activity in the Glb-1 pollen zone. At the transition of the Glb-1 and Glb-2a pollen zones, increasing arboreal species and lake levels are probably associated with humid conditions. Additionally, this phase is supported by algae and micro herbivore taxa. At 85 cm, the decrease in abundance of herbaceous communities and lake level suggest arid climatic conditions. Additionally, agricultural practices were probably affected by dry conditions during this time interval. In the middle of the Glb-2b pollen zone, increasing drought-tolerant Mediterranean xerophytes such as Quercus ilex- coccifera, and Pistacia indicate another dry period. The uppermost pollen zone of the GLB-01 core shows abrupt changes in the non–pollen assemblages, indicating important environmental alterations associated with deforestation. The dominance of Glomus (a mycorrhizal fungus) in the core suggests that erosion processes were active in the basin and were associated with some dry climatic conditions, anthropogenic influences, and probably seismic activity. At the bottom of the AZP-03 core taken from Lake Azaplı, with increasing deciduous Quercus, the humidity increases (>3019 cal years BP). This humid phase is also supported by algae taxa and the lake level change curve. In the upper part of the Azp-1 pollen zone, the decrease in the abundance of arboreal pollens such as deciduous Quercus, Pinus, and Cedrus and the presence of some NPP assemblages inhabiting dead wood and leaf litter indicate that the deforestation phase during the early Iron Age was accompanied by arid conditions. However, in the following pollen zones until the uppermost zone, an increase in Pinus represents the presence of secondary forests as a result of decreasing human pressure on the forests after the early Iron Age. Concurrently, the existence of cultivated and anthropogenic species and mega herbivore indicators prove that human activity has occurred in the area. The presence of Juglans (walnuts), which is a cultivated species in Anatolia, has spanned more than the last 3019 cal years in the vicinity of Lake Azaplı. The earlier emergence of Juglans compared to its eastern counterparts such as Lake Van and Lake Hazar, is possibly related to its geographic position which is situated at the intersection of the Eastern Mediterranean and Iran-Turan phytogeographic regions and earlier human activity in the area. The upper parts of the Azp-2b and Azp-1 pollen zones are represented by abrupt changes with decreasing numbers of arboreal plants and an increasing number of herbs, similar to Lake Gölbaşı. An increasing number of algae taxa, such as Pediastrum simplex, Pediastrum duplex, Pediastrum boryanum, Pediastrum biwae, Cosmarium sp., Spirogyra sp., Scenesmus, and Staurastrum sp., are related to nutrient enrichment as a result of freshwater input to the catchment area and human-induced pollution in the basin during the late Holocene. Moreover, the NPP of Rotifera eggs, Acari (oribatida), tintinids, and Cladocera species including Bosmina longirostris, among the microherbivores increased with the nutrient and algae enrichment in the GLB-01 and AZP-03 sediment cores. However, in the uppermost part of the cores, the occurrence of algal blooms is likely related to water level rise, changes in lake chemistry due to urbanization, and increased waste. Additionally, the classification of algae taxa based on trophic state showed that Lake Azaplı has more eutrophic conditions than Lake Gölbaşı in the uppermost pollen zones. Based on these findings, a palynological assessment revealed important environmental changes during the late Holocene in the Gölbaşı Basin. Further investigations are needed to better understand the ecological role of non–pollen palynomorphs and to establish their transfer functions. In addition, since the study area is a tectonically active basin, the ecological history of the region should be compared with palaeoseismological studies, together with the new chronology to be created with extra 14C dates.