LEE- Yer Sistem Bilimi-Doktora

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Fire history and climate change: Black pine forests in Western Anatolia

(Graduate School, 2022-06-15) Şahan, Evrim Ayşe ; Dalfes, Hasan Nüzhet ; Köse, Nesibe ; 601172003 ; Earth System Science

Wildfire is a part of the ecological processes that is highly important for the sustainability of forest ecosystems in the Mediterranean Basin. Species adapted to crown fires, such as Turkish pine, are capable of regeneration after a fire and establishing new forests. On the contrary, tree species such as black pine adapted to surface fires have regeneration problems after severe crown fires, and mass extinctions in some regions can be observed. Many studies have revealed that the fire frequency of forests in the Mediterranean Basin is expected to increase due to climate change and the fire regime of black pine forests will shift from surface fires to crown fires. In order to understand the fire regime changes in the black pine forests in the Mediterranean Basin, including Turkey, centuries-long fire records are needed. Thus, dendrochronology is one of the most reliable and effective methods commonly used in fire history studies. In this doctoral thesis, the aims are to develop a high-resolution fire reconstruction of black pine forests in Turkey, determine the seasonality of historical fires, understand the association between climate variability and fire occurrence, understand the variability of spatiotemporal patterns of fires throughout the main distribution areas of black pine forests in Turkey using tree-ring analysis, and monitor the cambium activity in black pine forest. Several spatial and temporal studies are conducted in order to understand the effects of fire management strategies, climate types or geographical gradients on regional fire regimes in the world. A large number of dendrochronology-based studies were conducted, especially in North America, to understand the spatiotemporal patterns in different geographical gradients and different climate types and also corroboration of empirical data. However, in the Mediterranean basin, a few fire history studies based on dendrochronological methods was conducted in Greece, France and Spain to understand the regional fire regime and the relationship between fire and climate. To my knowledge, there is no any conducted fire history study for any species based on tree-ring analysis in Turkey. A total of 211 samples were collected from ten sites throughout western Anatolia. The collected samples were dated by standard dendrochronological methods and the seasonality of each sample was determined. The site-level composite and regional fire chronologies were created for Kütahya, Isparta, Bolu, and western Anatolia. The major fire years were calculated with the criteria that greater than or equal to 25% of recording samples have fire scars on that year in at least two of the samples, while the regular fire years were determined by recording samples have fire scars on that year in at least two of the samples. The relationship between the major fire years and climate was analysed using Superposed Epoch Analsis. Understanding the seasonality of historical forest fires facilitates the development of concepts related to fire as an ecological and evolutionary process. In order to understand the fire regime of a region, determination of the seasonality is a must. In dendrochronology-based fire history studies, the seasonality of fire scars is mostly classified according to the intra-ring position of the fire scars as a classical method. However, studies of cambial phenology are needed to accurately correlate the position of a fire scar with the months in a year. Because the timing of the earlywood and latewood production (cambial cell production) varies according to the species, location and climate. In this context, the aim of this part of this thesis is to determine in which months the cambium activity of black pine forests starts and in which month the early/latewood cells form. In order to monitor cambium activity, a total of 144 microcores were sampled from three sites near the fire history reconstruction sites during a vegetation period (April-November 2021). Monitoring the cambial activity helped to obtain information about which month(s) are risky for forest fires. The first tree-ring based 553-year long fire history reconstruction and cambial activity of black pine forests were presented to improve our understanding of the regional fire regime components with the effect of climate in Turkey. The fire return interval of black pine forests in Anatolia was calculated from a minimum of one year and a maximum of 105-year intervals over the study period. The seasonality of most of the fire scars in western Anatolia occurred in the latewood period. As conducted in a cambial activity study of black pine forests in western Anatolia, latewood tracheid cells are formed from (August in Isparta) from September to November. Since most of the fires in western Anatolia occur in latewood, the risky months for fires in the study area are from (July in Isparta) August to November (the late summer and autumn) based on xylogenesis studies. The relationship between climate and fire years calculated with regional fire chronologies showed that the major fires in Kütahya and Bolu are associated with dry years, while the wet conditions two years prior to major fire events in Isparta. The decrease in fire frequency was observed in the late 19th and early 20th centuries due to human-induced fire suppression activities. That can cause the accumulation of combustible material and pose a risk for more intense fires. Based on future climate projections, as a result of increased drought frequency, we will face extended fire seasons that may shift the fire regime from the surface to crown fires and even cause mega fires. A large number of simultaneous fires were recorded in the period between the mid-1800s and the early 1900s. The decrease in fire frequency after the early 1900s coincides with the first forest protection law in 1937. As a result of the comparison of fire years in western Anatolia, Spain, and Greece, more common fire years were found in studies of Greece than in Spain. The differences in climate conditions of the eastern and western Mediterranean due to frontogenesis or depressional activity might explain these different common fire years. The year 1879 was the most extensive fire year in Greece in the 19th century and it was recorded as one of the most common fire years in western Anatolia. The year 1945 was the only common fire year in the Mediterranean region sites. Results in this study showed that the fires in 1945, observed simultaneously in Anatolia, Greece, and Spain, occurred in the most severe and widespread drought among the spatially visualized common fire years. In this study, long-term fire history data were developed by using dendrochronological methods to understand the fire regime of black pine forests for the first time in Turkey. These fires were analyzed with a new approach with the determination of the seasonality by taking samples with microcores. Unlike studies only current fires are analyzed or fire history reconstructions, the results were obtained by integrating both ecological and statistical methods.
Distribution of radionuclides in Arıklı region (Çanakkale/Ayvacık) and possible causes

(Graduate School, 2022-06-28) Top, Gülcan ; Tutay Örgün, Yüksel ; Karahan, Gürsel ; 601112002 ; Earth System Science

The aim of this thesis is to determine the indoor and outdoor gamma dose rates in Arıklı (Çanakkale/Ayvacık/Turkey) uranium mineralization region, to determine the activity concentrations of 226Ra, 232Th, 40K in selected samples (building materials, rocks, surface soils, beach sands and soil samples collected from excavation ditches), to map the outdoor gamma dose rates and the activity concentrations of the radionuclides specified in the surface soils using geographic information systems, to identify the geological sources that cause high doses and to evaluate the possible health risks for the region based on all these measurement results. The measurement of mass concentrations for U, Th on some selected samples is also included into the study. This study is the first comprehensive study for the region. For this thesis, the Arıklı region was considered as a research area due to the presence of a uranium mineralization zone and the prevalence of felsic volcanic rocks containing above-average uranium, thorium and potassium concentrations. In order to determine the level of radioactivity in the Arıklı uranium mineralization region, preliminary field studies were started in 2015 measuring the outdoor gamma dose taking into account the geological formations. It has been determined that anomalies are especially concentrated in and around the drilling points determined by the General Directorate of Mineral Researches (MTA) to search for uranium.
Temporal and spatial investigation of maritime accidents in the strait of Istanbul in the perspective of navigational safety

(Graduate School, 2022-10-24) Kodak, Gizem ; Ünal, Alper ; Acarer, Tayfun ; 601142001 ; Earth System Sciences

The Strait of Istanbul is located on the primary routes of international maritime transport. The strait, which is the second busiest waterway in the world with average of 50.000 ships per year, has four times more maritime traffic than the Panama Canal and three times more than the Suez Canal. When compared to its peer waterways the biggest threat in the Strait, the risk of accidents created by difficult navigational conditions. Some of the accidents that took place in the strait in the recent past have caused worldwide concern due to the environmental disaster they have caused. Considering that today, ships carrying dangerous goods serve at much larger capacities compared to the past, the maritime traffic in the region poses a risk both for the ships passing and for the city and people of Istanbul, which is densely populated on its shores. In this context, the development of solutions to reduce maritime accidents in the region plays a key role in strengthening navigational safety. In this study, the accidents that took place in the strait were discussed in terms of temporal/spatial and were examined simultaneously with the environmental factors affecting the navigational safety. For this purpose, hourly wind speed and wind direction data of Sarıyer and Atatürk meteorology stations located on the traffic route in the strait were obtained from the Turkish State Meteorological Service and wind dynamics affecting maritime traffic were examined. On the other hand, accidents also were evaluated in terms of the number of ships passing and the effect of maritime traffic on accidents were examined with the regression analysis. In this direction the monthly movement of international ship traffic in the strait was examined on a micro scale with the data of the Directorate General of Coastal Safety and accident rate per passing ship was calculated. In addition to dynamic factors such as wind speed, wind direction and traffic flow, another factor affecting the occurrence of accidents in the strait is the navigational regulations carried out in relation to the traffic order. In this context, the regulations for maritime traffic in the strait were examined chronologically and compared with the accident data. Thus, not only the effects of the regulations regarding navigational safety on the accidents were observed, but also the strengths and weaknesses of the developed solution proposals were revealed. The results of the study have shown that patrol tugs can be an effective solution to prevent accidents when the wind and current dynamics in the region and the spatial distribution of the accidents are evaluated together. In this direction, the response time of the proposed patrol tugboats to a possible accident was calculated and the response options were evaluated under two different scenarios as parallel to the current and antiparallel.
Systematics and biostratigraphic implications of micromammals (Rodentia) from selected pliocene-quaternary basins along the North Anatolian Fault Zone

(Graduate School, 2023-07-20) Erdal, Ozan ; Dalfes, H. Nüzhet ; Şen, Şevket ; 601122006 ; Earth System Sciences

Anatolia plays an important role as a bridge between Africa, Europe and Asia for the evolutionary course of vertebrates. It is potentially rich in fossil bearing deposits which would greatly serve to contribute the understanding of vertebrate evolution. However, paleontological research conducted in Turkey is mainly focused on Paleogene and Miocene deposits. Although it is obvious that any studies of mammalian paleontology dealing with any interval of Cenozoic in Anatolia is worthful because of its potential, one must point out that Quaternary mammalian fauna is still not well known when compared to European equivalent. In this manner, it is not difficult to estimate how micromammalian paleontology is less dealt. The introduction of the present thesis deals with some general definitions and fields of application of micromammals besides a brief summary of all conducted or ongoing studies on the Quaternary micromammalian fauna in Anatolia. One of the main motivations of this study is to underline the potential contribution of micromammal paleontology to Quaternary research in Turkey. On the following sections, a detailed study is provided on rodent remains which were collected from diverse localities in three adjacent basins on the North Anatolian Fault Zone (NAFZ), the depositional ages of which are estimated spanning from the Pliocene to the late Pleistocene. I investigated small mammal faunas of these basins by means of systematic paleontology, biochronology with proper stratigraphic positions, and studied their inference on paleoclimate and paleoenvironment of the localities. The North Anatolian Fault Zone (NAFZ) forms the boundary between the Anatolian and Eurasian plates and hosts many tectonic basins. The chronology of the NAFZ basin deposits is established mostly by pollen and partly by mammalian fauna studies. Nonetheless, the formation history of these basins starting in the Late Miocene to the Pleistocene and actively continuing today is still incompletely known because biochronological data are still scarce. The previous studies on the Tosya Basin by many authors and on its several aspects revealed detailed information on the structure of the basin (Barka and Hancock, 1984; Şengör et al, 1985; Andrieux et al, 1995; Dhont et al, 1998). The earliest deposition within the basin, the Devrez Formation, is claimed to date of Early-Middle Miocene but no fossil findings are discovered so far. According to Ünay and de Bruijn (1998), the only paleontological work on the area despite the lack of stratigraphic position nor systematic description, an Early Pliocene age (late Ruscinian-MN15) is suggested based on micromammal fauna from one locality at Ortalıca Village. In the same study, they proposed Early Pleistocene (MN17) age for a locality at Karasapaca Village to the West of Ortalıca, based on micromammal remains. Unfortunately, stratigraphic positions of these localities are uncertain. In the present study, the occurrence of Mimomys cf. polonicus at the Sapaca locality points out the early late Villanyian (MN16b) age for the locality which is older than previously studied locality Karasapaca by Ünay and de Bruijn (1998), situated at the north-eastern to the Sapaca village. At the Ortalıca locality, the co-occurence of Pliomys destinatus, Apodemus atavus and Mesocricetus primitivus within their stratigraphic position, supports rather the transition from MN15 (late Ruscinian) to early Villanyian (MN16a), slightly younger than age proposed by Ünay and de Bruijn (1998). On the other hand, the newly discovered Kumkapı locality, at the SW of Ortalıca and Sapaca-Karasapaca, surprisingly indicates a much younger age, late Toringian with remains of Microtus (M.) arvalis and Mus cf. macedonicus which provide a profile well younger than the Umurlu locality findings from the Niksar Basin. Finally, the finding in this basin reveals a more or less continuous deposition, where the faunal succession from the Early Pliocene (MN15) toward the Late Pleistocene follows the opening of the basin in a NE–SW direction, in almost 4 Ma. Indeed, the surprising young age of Kumkapı deposits is subjected to further geological studies in the near future. The abundance of Pliomys and Apodemus species in Ortalıca, in overall, points out rather forested, wooded and humid environment rather than grassland. (Sen, 1977; Suata-Alpaslan, 2010; Hoek Ostende et al. 2015b; Popov, 2018). However, the presence of Mesocricetus remains together with Pliomys and Apodemus would indicate that for a while between MN15b–MN16a (Pliocene), there have been cooler climatic conditions occurred, which resulted in steppe environment (Sen, 1977; Hoek Ostende et al. 2015a; Popov, 2018) may be with sparse forested area for the food sources. Sapaca locality which is younger than Ortalıca but much older than the Kumkapı localities yielded only Mimomys species, which are generally reported from relatively warm and arid, open steppe environment (e.g. Rabeder, 1981; Montuire et al, 1994; Popov, 2017). Finally, the Kumkapı locality with the presence of recent species of Microtus and Mus, is not much different from the present climate and environmental condition of the studied area such as mixture of open environment with meadows and grasslands with warm climate, as pointed out in previous studies (e.g. Montuire et al, 1994; Çolak et al, 2016; Erdal et al, 2018, 2019). The Suluova Basin is a prominent member of a wide transtensional Amasya Shear zone, located at the central part of the North Anatolian Shear Zone. Analysis of detailed stratigraphic sections, faulting data and mammal paleontology reveals that the Suluova Basin has started to evolve as a closed half-graben along the NE-SW trending, SW dipping basin bounding fault zone with normal slip at early Quaternary. Within this tectonic environment, the sedimentary assemblages were various facies of a river dominated alluvial fan network. As faults propagated westwards, the basin deepened and a fresh water lake started to develop at the basin depocenter. The initiation of E-W trending southern tectonic boundary of the basin caused further extension. Each basin boundary fault zones witnessed clockwise rotation in time. Marking an increasing water income, the Suluova Basin has evolved into a vast fresh water lake during the Middle Pleistocene (~1.7–0.8 Ma) acting as a refugia for a potential rich faunal assemblage of large and small land mammals. Thus far, micro- and macromammal remains studied from several localities in the basin comprise Kalymnomys sp. and Sivatherium sp. from late Villanyian of Kurnaz; Microtus (Allophaiomys) aff. nutiensis, Mimomys aff. pliocaenicus and Apodemus cf. dominans from late Villanyian–early Biharian of Kerimoğlu; Mesocricetus aff. arameus from early Biharian of Kızıleğrek, and Mesocricetus cf. brandti and Arvicola cf. mosbachensis from early Toringian of Yolpınar, in addition to some fragments of Equus sp. The faunal association from five localities would allow to make some assumptions concerning the past environment. For instance, the paleoenvironment of Sivatherium is reported as grasslands and well-watered landscape with much warmer temperature for the early part of Early Pleistocene (MN17–MNQ18); Kalymnomys on the other hand, is not well known but based on actual relatives (e.g., Lagurus lagurus) it is thought that should be rather dry steppe environments (Alçiçek et al, 2017, p.242). The floodplain deposits at the Kurnaz locality would support the former hypothesis in addition to environmental changes with the presence of a paleolake at the younger Kerimoğlu locality which would point out rather warmer climate. The Kerimoğlu locality, as it is important for the formation of a paleolake which is also supported by the remains of unidentified fossil fish teeth, represents an environment surrounded with deciduous woodland and bushy vegetation covers with streams and marsh-like areas by the presence of a large vole Mimomys aff. pliocaenicus and Apodemus cf. dominans. (Siori and Sala 2007; Hoek Ostende et al, 2015a; Erdal et al, 2018; Sen et al, 2018). The macromammal remains at Kamışlı has been previously reported by Sickenberg and Tobien (1971, p.60–61) where faunal elements including Equus sp. point out steppe environment crossed by forest along the water courses and lakes. The presence of Mesocricetus spp. at Kızıleğrek and Yolpınar localities would indicate somewhat dry, semi-arid steppes covered by sparse vegetation (Krystufek and Vohralik 2009). Note that Anatolia is playing an important role for the evolution of the hamster Mesocricetus during the Middle Pleistocene, which is favoured by alternating dry periods and spreading lakes causing steppe-corridors for hamsters' dispersals and adaptations (Neumann et al, 2017). On the other hand, the water vole Arvicola findings together with Mesocricetus as at the Niksar Basin, demonstrate rather a mixture of steppe-like environments with water streams for that youngest locality to the east of the Suluova Basin. A new micromammalian faunal assemblage from four horizons at the Umurlu locality (Niksar Basin, Tokat-Turkey) has been investigated; it improves our knowledge about the chronology of this basin infill. According to the stratigraphic range of the recorded species (Mesocricetus cf. brandti, Cricetulus migratorius, Arvicola cf. mosbachensis, Microtus arvalis, M. (Terricola) subterraneus, Clethrionomys cf. glareolus, Apodemus flavicollis, Nannospalax cf. xanthodon) the age of the deposit is constrained between early Middle Pleistocene and Late Pleistocene (i.e., 480–130 ka). The fossil assemblage indicates a mixture of open environments with meadows and grasslands associated with forested and bushy vegetation covers. This fauna and the implied environment are typical for an interglacial period, most probably within the interval of MIS 12–5. The studied rodent assemblage with elements of several paleobiogeographic affinities shows once more the key position of Anatolia as a bridge between the Old World continents. It improves our knowledge on Quaternary micromammals of Anatolia, which is still poorly documented, and provides a well-constrained age of the investigated localities.
Vegetation phenology and its interactions with climate change – a study on Turkey and its region

(Graduate School, 2023-07-25) Şenel, Tuğçe ; Dalfes, Hasan Nüzhet ; 601152003 ; Earth System Science

In the face of climate change, one of the most crucial questions in ecology is 'How will the ecosystems respond to the impacts of climate change?'. The literature on the topic of how climate change is and will be affecting natural ecosystems is quite rich, however, it is not quite the same way around for the literature on how the natural ecosystems will react to these threats or if they will react at all. To be able to answer the initial question and prepare accordingly, first we need to understand how these natural ecosystems or vegetation cover responded to these changes before and then make healthy predictions on what will be their mechanisms to deal with the impacts of climate change in the future. Results from many studies globally already reported on the observed responses from different taxa and ecosystems to climate change. These responses can be expressed as the shifts in phenological phase timings, range and/or distribution shifts, changes in population dynamics, altered composition of communities or changes in genetic traits. Among these phenological phase timings are the most commonly reported ones. Phenology, a term coined by Belgian botanist Charles François Antoine Morren, studies the timing of periodic events in organisms' life cycles both plants (such as first leaf budding, or first leaf fall and animals (such as egg laying), investigates which factors drive these timings and in which ways they affect them and in which ways these periodic events or 'phenophases' are related to each other, how they affect each other for the same species and between different species. Plant phenology is strongly affected by climate but also capable of affecting it through, e.g., carbon sequestration, surface roughness, albedo, water, and other important biophysical cycles. Moreover, changes in phenology, even for individual species can have massive chain effects on the ecosystems, affecting many connected biotic and abiotic elements and consequently lead to changes in ecosystem functioning and processes. Phenology modeling has an important role in predicting the effects of climate change and ecosystem responses to these impacts and investigating the factors behind phenological shifts as well as in conservation and management planning. Plant phenology also became a prominent part of regional or global ecosystems simulation models and coupled biosphere/atmosphere general circulation models. As the important roles and connections of phenology to climate have been better understood, more attention and effort have started to be put into phenology studies. Phenology is traditionally tracked by field observations on individual or small groups of plants. Today it is mostly carried out by phenology networks such as USA-NPN and Observatoire des Saisons. Phenophases to be observed (such as first leaf or budburst, first leaf fall or autumnal coloring) and their descriptions are defined through the chosen protocols by individual networks. These observations produce very valuable, accurate and long-term datasets which are capable of catching critical phenophases. However, to understand the impacts of climate change on vegetation phenology and to be able to see the generalized response patterns from different vegetation covers, long-term, continuous data from broad scale areas, from ecosystem scale to hemispheric or global domains, is needed as the individual responses of plants may not represent the response of the entire ecosystem it occurs in. Moreover, observational phenology data has serious drawbacks such as not being evenly distributed around the world (e.g., some countries do not have this sort of observation records of their natural vegetation types and most available phenological records are on certain types of vegetation such as deciduous forests but rarely on ecosystems such as deserts), observations made by following different protocols, potential mistakes in records due to the observer-related errors, etc. After satellite remote sensing (SRS) entered ecological research, phenology studies gained an indisputable speed and volume as it overcomes many of the disadvantages mentioned above. SRS data provides data from local to near-global scales, datasets are continuous, long-term, and objective by the nature of the sensor measurements. With these advantages, researchers now can observe large-scale vegetation response patterns to climate change and study the long-term trends in phenological parameters such as the start of season (SOS). Phenology, measured by the SRS tools, is now named 'Land surface phenology' to emphasize the difference between them and the phenological records obtained by traditional phenology. LSP constitutes a very valuable tool to monitor phenology in the absence of observational data. Due to its location between Asia and Europe, diverse topography, the effect of the three bounding seas, three phytogeographical regions intersecting within its borders, Turkey has an enormous biodiversity richness. Turkey resides in the easternmost Mediterranean Basin which was defined as one of the most vulnerable areas to climate change impacts. Results from many studies and projections show that Turkey will be experiencing increasing temperatures and alterations in precipitation. To make accurate management, mitigation, and conservation planning for the aforementioned biodiversity richness, to have a deep understanding of if and how the natural vegetation covers of Turkey responded to climate change impacts is a must. However, Turkey is one of the mentioned countries which does not have phenological observations data for its natural vegetation covers. Phenological observations, as well as LSP studies, are made almost exclusively on plants under human care such as agricultural plants. To my knowledge there is no LSP studies, which focuses on Turkey's natural vegetation covers, investigating the long-term trend shifts in season metrics such as the start of season (SOS) at the country-scale with a clear metric extraction. To address this gap and to provide a baseline for methodology for future studies in Turkey and its region, in this thesis, I investigated the long-term (2002-2020) phenological parameter trends of two deciduous (Fagus orientalis and Quercus; Quercus robur, Quercus cerris, Quercus frainetto, Quercus pubescens) and three evergreen needleleaf species (Pinus brutia, Pinus nigra and Pinus sylvestris) by means of SRS methods and assessed their relationship with the temperature-derived parameters. I characterized the spring phenology for Fagus and Quercus in Turkey and evaluated the effect of altitude and latitude on their phenologies. As phenological parameters are very time sensitive, unlike the majority of LSP studies worldwide which utilize composite datasets, I used a daily MODIS product, 'MODIS/Terra Surface Reflectance Daily L2G Global 1 km and 500 m SIN Grid v006" (MOD09GA)' and calculated the Normalized Difference Vegetation Index (NDVI) with red and NIR band measurements for all pixels within the borders of Turkey. To keep the pixel heterogeneity minimum, I used a forest management plan to filter only the pure stands for the species I worked with and applied a vigorous temporal and spatial coverage filtering to work with pixels of the best quality for this work. This study is designed around and focuses on the parameter SOS, as the end of season (EOS) is very problematic and hard to correctly detect, and I did not have grounding observational data to be sure of my interpretations on EOS. However, to provide a full understanding on the season dynamics EOS and the length of season (LOS) parameters were also extracted and calculated and their trends over the 19-year study period was also analyzed. The evergreen species did not show phenological phase changes measurable by NDVI so they were not included in further steps of the study. I extracted the SOS parameter first, for the two deciduous species, analyzed their SOS trends over the study period and then extracted the EOS metric only for the pixels which showed a significant SOS trend (547 MODIS pixels for Fagus and 840 MODIS pixels for Quercus). LOS was calculated as the difference between SOS and EOS. Then trends in these parameters over the study period were also investigated. As temperature is considered the main driver of phenology for the temperate zone deciduous forests, I used temperature-derived variables to assess the relationship between the climate change and SOS trends of studied vegetation types. To achieve that, I calculated chilling hours (CHs), growing degree days (GDDs), mean, maximum and minimum temperature variables for different time intervals (such as FebruaryMarch or April) and with different thresholds (for CHs) and different base temperatures (for GDDs). These variable-interval-threshold/base temperature combinations were then evaluated for statistically significant changes over the study period. Variables/combinations which did not show a significant change in 19 years were not included in further analysis. According to the estimations, both Fagus and Quercus showed an earlier SOS and prolonging LOS pattern in concert with the reports from the literature. SOS was exhibiting an advancing trend over the study period by 0.8 days per year and LOS was getting longer by 1.07 days for Fagus. Similarly, for Quercus an advancing SOS pattern by 0.74 days per year and a prolonging LOS by 0.84 days per year. For Fagus, the multi-annual (2002-2020) mean SOS and EOS were found as day of year (DOY) 121.1 and 300.30 respectively and the mean LOS was 179.09 days long. For Quercus, the multi-annual (2002-2020) mean SOS and EOS were found as DOY 122.3 and 289.5 respectively and the mean LOS was 167.2 days long. The highest correlations between the SOS and temperature-derived variables were found to be February-March CH with 7.2°C threshold value for Fagus and March-April maximum temperature for Quercus.
Invasive species distribution modeling under climate change

(Graduate School, 2023-08-08) Kanmaz, Oğuzhan ; Dalfes, Hasan Nüzhet ; 601152001 ; Earth System Science

Biological invasions are one of the most significant components of global environmental change. The biological consequences of invasions such as biodiversity loss, biotic homogenization, alterations in the structure and function of ecosystems are difficult to reverse and even impossible in many cases. The damages and loss caused by biological invasions are estimated to reach billion dollars each year. Post introduction control of an invasive species is often futile alongside being expensive and labor intensive. In this sense, prevention is considered to be the most effective strategy against invasions. Determination of the areas under risk of invasion and evaluation of the potential invasion scenarios are extremely important. To that end computational models constitute crucial tools. In recent decades increased availability of powerful hardwares, alongside with the accessibility of environmental and biogeographic data, due to the developments in information technologies, lead to the utilization of computational models in various fields of ecology. Species Distribution Models (SDMs), which are an example of such applications, especially the data-driven correlative methods, were utilized widely to investigate the impacts of global environmental change on the current and future distribution of species. Application of SDMs on invasive species to determine the areas under invasion via the projected suitability/presence probabilities, despite the criticism on the violation of the equilibrium assumption, has become a widely used method with various successful and promising examples. However, another problematic aspect of such applications is that the projected suitability cannot always be interpreted as an actual invasion since the dispersal is a crucial process of biological invasions. Agent-Based Modeling (ABM) is a population modeling method with wide applications in ecology to simulate various complex processes via the functional units called agents which can interact with each other and the environment. In this respect agent-based models constitute a remarkable alternative to simulate biological invasions with various examples in the literature. While agents-based models are especially useful to investigate the theoretical problems and considered as in silico laboratories for paradigmatic models, their application on spatially explicit, real world cases to construct pragmatic models is mostly difficult due to the lack of a priori knowledge on the majority of the species to calibrate such models. Hybrid modeling is a promising approach which can utilize more than one modeling method in tandem, by taking advantageous aspects of these methods which can complement each other to obtain more reliable results. Within the scope of this thesis, a hybrid modeling framework, which consists of a correlative and an agent- based component was constructed. Accordingly, while the framework proceeds in yearly time steps, correlative component produces bioclimatic suitability projections to be used by the agent-based component and the agent-based component generates simulated occurrence records to be utilized by the correlative component for making projections. Beyond the basic structure of the framework, the modular structure enables the inclusion of species specific processes which are constructed based on the a priori knowledge to obtain more realistic projections. For the implementation of the modeling framework, Impatiens glandulifera, a highly aggressive invasive plant native to Himalayas, was selected. Since its introduction to Europe and North America in the late 19th century as an ornamental plant, it has primarily invaded riparian habitats. The current invasive range of I. glandulifera spreads across the northern hemisphere. In the last two decades, it was observed to invade forests and mountainous areas. The spatial context of the model was determined as North America where the invasive range is far from reaching its bioclimatic potential and the simulations were conducted for 2020-2050 period under RCP 4.5 climate change scenario. In accordance with the a priori knowledge on I. glandulifera, the agent-based component of the framework which consists of three procedures (Climatic Window Procedure, Landscape Suitability Procedure and Propagule Procedure) to process three types of agents (productive, post-production and pre-productive agents) was constructed. The Climatic Window Procedure which consists of Chilling Period, Bioclimatic Suitability, and Productive Agent Sampling sub-procedures, performs the transformation of pre-productive agents to productive agents based on the chilling requirement and bioclimatic suitability projections that are generated by the correlative component alongside the sampling of the generated agents. The Propagule Procedure performs the generation and dispersal of post-generation agents. The Landscape Suitability procedure evaluates the transformation of post- generation agents to pre-productive agents based on the pH, elevation, slope, and land use properties. As the result of the conducted simulations, it was observed that the initial invasive range in North America, which is on the west and the east shores initially, has expanded through the 2020-2050 period. While in the eastern part of the invasion range, Great Lakes region and New England shores were observed to be saturated, progression on the western part was primarily determined by the mountain ranges. The severity of the projected invasion range on the Alberta-Saskatchewan region is especially remarkable, considering the limited presence of I. glandulifera in this area in the initial conditions. Another important result is the potential formation of a continuous range crossing the continent in the long term, due to the aggressive expansion to the interior regions. The projected latitudinal progression of the invasion is compatible with the large- scale pattern of the northward progression of the species due to climate change. While the northern boundary of the projected invasion range was roughly following the boreal biome, the southern boundary was formed on latitudes similar to the southern boundary of the invasion range in Europe. Another striking similarity was the southern progression on the west shores being limited by the Mediterranean climate observed in the region, which is also the determinant of the limited southward progression in Europe. The potential impacts of the I. glandulifera on the boreal forests, which are expected to be more fragile in the future due to climate change, must be carefully evaluated since I. glandulifera is known to spread in such disturbed forests. The long distance dispersal is mostly a result of anthropogenic activity, and unlike many of the natural processes, can lead to unpredictable results. This constitutes a limitation for the projections. Also, the impact of the incomplete occurrences data on the projections, especially records for the regions, is unavoidable. In the scope of this PhD thesis, it was aimed to construct a modeling framework by the utilization of correlative species distribution and agent-based modeling methods in tandem to simulate biological invasions under climate change. The framework was implemented to make projections for I. glandulifera invasion in North America for 2020-2050 period under RCP 4.5 scenario. In accordance with the conducted spatiotemporal analysis on the projections, invasion patterns were determined and the potential impacts on the invasive range were evaluated. The results were observed to be in concert with the historical invasion patterns of I. glandulifera in Europe and the climatic and environmental projections for North America. In this regard the framework can be considered a promising tool to be utilized for making projections which can be used for determination of the areas under invasion risk.
Effects of climate change on potential range shifts and composition of Türkiye's terrestrial ecosystems

(Graduate School, 2024-03-18) Ekberzade, Bikem ; Şen, Ömer Lütfi ; Yetemen, Ömer ; 601192001 ; Earth System Science

At the current critical juncture with climate change, centennial projections of potential species distributions in biodiversity hotspots, using dynamic vegetation models with integrated ecological notions such as competition, may provide vital insight into conservation efforts. The central aim of this thesis research is to estimate the current and future potential distribution of Türkiye's forests and their composition in the absence of anthropogenic landcover change, to calibrate the bioclimatic thresholds of certain key taxa to reflect their regional distribution in simulations using a process-based dynamic regional-to-global vegetation model (DGVM) to introduce new taxa to the simulations where necessary and in this manner to contribute to past studies on the distribution of European forest taxa by filling an important spatial gap. For this purpose, potential distribution of 25 forest taxa, and a C3-grass type are simulated by means of LPJ-GUESS v. 4.1 for the Anatolian Peninsula, keeping a spatial window large enough to track temporal changes in the vegetation range and composition in its surrounding areas. The model was forced with ERA5-Land reanalysis data for the historical period (1961-2014), and five different global climate model (GCM) contributions to the 6th phase of the Coupled Model Intercomparison Project (CMIP6) for the scenario period (2015-2100). The GCM datasets were interpolated to ERA5-Land's resolution and bias corrected with the climatology of the reference period 1995-2014 from the ERA5-Land dataset. The reference period for bias correction was selected in accordance with the 6th assessment report of Intergovernmental Panel on Climate Change (IPCC 2021), and in part, to reflect the current state of global warming. Shared Socioeconomic Pathways (SSP) 5-8.5, the high emissions scenario, was selected for all simulations. The bioclimatic tolerance levels of all plant functional types were calibrated using the temperature components of 1 km CHELSA dataset, and 9 km ERA5-Land datasets, calculating climatologies where necessary using Climate data operators (CDO) and R computing language; species distribution maps from European forest genetic resources programme (EUFORGEN); and the forest inventory data from General Directorate of Forestry (GDF) of Türkiye. In situ site visits were also undertaken to critical regions within the study area to further finetune the bioclimatic tolerance levels of certain key taxa, and further analysis of both observation data and the simulation results were made using R and ArcGIS. The simulation results from multiple model runs highlighted a consistent increase in woody species biomass for the entire study region, by the end of the century. The increase in biomass, mainly in the grasslands ecosystems was an important outcome of these series of simulations, which highlighted a consistent encroachment of woody taxa into terrain that is otherwise dominated by grasslands in simulations, in part reigniting the discussion over the past anthropogenic influence on the current vegetation composition of the Peninsula. The mountain systems also came out as important potential refugia for many cold-favoring woody taxa. Throughout the centennial simulations, the tree species prioritized an altitudinal move rather than a latitudinal one, consolidating their ranges around high elevation massifs, occasionally giving up their density dominance but gaining biomass. The composition of forest and woodland ecosystems shifted in large part in favor of the temperate taxa, as these species expanded their distribution ranges throughout the study area, without any particular prioritization for altitude or latitude. Temperate taxa with higher tolerance for drought increased their overall biomass and density, while the drought sensitive species gave up their dominance but continued to exist in smaller groups in areas where resource limitation became a determinant for the outcome of competition. All simulated taxa survived the 140-year simulation period at some capacity (there were no potential regional extinctions), finding some form of a footing along this ancient land bridge – some giving up their largely monotypic/homogeneous forest ranges for mixed forest compositions; others either leaving their dominant presence and becoming a "member of the team"; or exerting their dominance over a larger area. Overall, the results from these series of simulations, sans human presence, suggest a high potential for future forest cover throughout the study region by the end of the century under a high emissions scenario, and important changes in vegetation composition including encroachment of grasslands ecosystems by woody taxa. Our findings also corroborate recent paleo studies that highlight the early forest capacity of Asia Minor, and with the right environmental policies in place to ensure a fair human-nature co-existence, the region may continue to play its role as a cradle.
The impact of paleoclimatic changes on the archaeological settlement patterns in the Gediz Graben (Western Türkiye) during the late pleistocene and holocene

(Graduate School, 2024-05-28) Kolbüken, Mesut ; Arıkan, Bülent ; 601192009 ; Earth System Science

The Gediz Graben has been an attractive area for human occupation due to its suitable geographical features such as the large arable land coupled with water sources that supported animals and plants attracted human groups and societies at different archaeological periods. The graben is one of the highly sensitive areas in the Anatolian Peninsula to climatic changes as the climatic patterns in the region have been controlled by both polar and tropical circulation systems. Therefore, the area provides a great opportunity to assess human-climate interaction. This research aims to reconstruct paleoclimate dynamics of the Gediz Graben since the late Last Glacial covering the last 21 ka and to contextualize human-environment interactions in archaeological settlement patterns in the region by using a multiple approach through different paleoclimate models (the Macrophysical Climate Model and CHELSA-TraCE21k) for paleoprecipitation and paleotemperature patterns and a new palynological record from core MAR03-02C in the Aegean Sea for the reconstruction of paleovegetation patterns with paleoclimate interpretations in the surrounding landmass. Based on the results of the paleoclimate models, in the late Last Glacial Period and the early Holocene, the climatic conditions of the graben were wetter (except paleoprecipitation of the CHELSA-TraCE21k) and colder than today. During the middle and late Holocene, the climate was generally stable, and near-modern patterns prevailed around 7 ka in the graben while the climatic shifts occurred at smaller amplitudes for shorter time periods in comparison to the previous periods. This pattern was recorded in variations in Mediterranean/temperate forests and herb/steppe plants. In the cold and dry late Last Glacial Period, low amounts of arboreal pollen and high percentages of cold/drought-tolerant Pinus and Cedrus trees with high amounts of herbaceous and steppe pollen, including Artemisia, Cyperaceae, and Asteraceae Cichorioideae were recorded. Warm-temperate and Mediterranean trees, consisting of mainly deciduous Quercus and Quercus ilex-type trees, reached their maximum from the onset of the Holocene at ~11.7 to 6 ka, corresponding to the Holocene Climate Optimum. Subsequently, general aridity trends and nearly modern climate patterns prevailed. Variations in the paleovegetation, the paleoprecipitation and paleotemperature patterns indicate major climatic shifts associated with the Greenland Stadial 2, the Bølling-Allerød, the Younger Dryas, and the Holocene Climatic Optimum and some rapid climate changes, such as the 11.1, 9.4 8.2, 5.9, and the Little Ice Age cold events; a short warm interval of the Medieval warm period during the Holocene. In Gediz Graben, the patterns from the paleoclimate models and the palynological record show similarity with local and regional proxy data in the eastern Mediterranean. The archaeological settlements in the plain, which increased from the Neolithic to the Bronze Age except the Iron Age, gathered around water resources. The results suggest that the paleoenvironmental processes (the paleolakes, paleoclimatic conditions, paleovegetation patterns) contributed to the decisions concerning the locales of archaeological settlements on the Gediz Plain. Anthropogenic indicators plants with the onset of the Neolithic come into slight in the region. Especially, during the last 3.5 ka when cultivated plants became prominent in the pollen records (e.g., Olea europea and Pistacia), with a significant decline in warm-temperate trees until 1.2 ka, suggesting that the Beyşehir Occupation Phase is also recorded in the palynological records of core MAR03-02C in the Aegean Sea. As a result of this study, significant findings regarding paleoenvironmental changes in the region and human-environment interactions have been obtained. The results underscore the importance of making future plans regarding human-environment relationships in the Eastern Mediterranean Basin, where Türkiye is prominently located, which notably demonstrates the impacts of the current climate change crisis. This highlights the necessity of taking measures to mitigate the effects of the climate crisis, strengthening societal resilience, and conserving natural resources.
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.
Buzlu okyanus dünyalarının jeokimyasal modeller yoluyla astrobiyolojik açıdan incelenmesi

(Lisansüstü Eğitim Enstitüsü, 2025-06-13) Işık, Seda ; Kıyak Olğun, Nazlı ; 601142011 ; Yer Sistem Bilimi

Bu çalışmada, Güneş Sistemi'ndeki okyanus dünyalarının (Europa, Enceladus, Titan, Ganymede) astrobiyolojik potansiyeli termodinamik modelleme yaklaşımıyla incelenmiştir. DEWPython ve SUPCRT modelleri kullanılarak, temel metabolik reaksiyonların (metanojenez, asetojenez, hidrojenez, sülfat indirgeme), sitrik asit döngüsünün ve prebiyotik reaksiyon ağının bu dünyaların iç koşullarındaki termodinamik davranışları analiz edilmiştir. Yeni geliştirilen "kimyasal tür kararlılığı" parametresi ile denge dışı sistemlerdeki moleküler kararlılık değerlendirilmiştir. Bulgular, okyanus dünyalarında sitrat ve süksinatın birikme eğiliminde olduğunu, fumarat ve oksaloasetatın ise kararsız olduğunu göstermiştir. TCA döngüsünün tek yönlü işleyişinin termodinamik kısıtlamalarla karşılaştığı, ancak piruvat-asetat yoluyla alternatif metabolik yolakların bu darboğazları aşabileceği tespit edilmiştir. Sülfat indirgeme tüm ortamlarda en elverişli metabolizma olarak öne çıkarken, her okyanus dünyasının benzersiz termodinamik imzalar sergilediği belirlenmiştir. Bu sonuçlar, gelecek uzay misyonlarında biyoimza arayışı için önemli teorik temeller sağlamaktadır.

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