Dendrochronological analyzes in the field between Kürtün and Gavraz Creeks

Many forests on Earth are living monuments that witness to the history of our planet, therefore, are important and sensitive ecosystem. The study area, located in the Eastern Black Sea Region between Kürtün and Gavraz Creeks and an important ecosystem that is under protection due to its importance in terms of flora and fauna for Turkey, as well as the diversity of the environment it hosts. Dendrochronology, the study of dating the tree rings and also used in physical geography studies, is an important branch of science that aims to understand the dynamics of annual rings and growth characteristics of trees. For this reason, I aimed to contribute to the elimination of the existing data gap for the Eastern Black Sea Region using primary forest trees and to obtain climate sensitive chronologies. Using these chronologies, it is aimed to 1) understand the linear and nonlinear climate-growth relationships, 2) determine the stability of these relationships over time, and 3) develop climate and streamflow reconstruction. Oriental spruce or Caucasian spruce (Picea orientalis), is the dominant tree species of the study area, and Scots pine (Pinus sylvestris), is also one of the important conifer species, were sampled for this study. The core samples were collected in total of 70 trees from five sites. The samples were sanded and measured in the LINTAB-TSAP Measurement System and the missing and/or false rings were eliminated. The time series for each annual ring was then standardised with Biweight Robust Mean method and lastly the residual chronologies of each site was calculated. The calculated chronologies were analysed using annual ring growth characteristics to understand the effect of changes in climate on vegetation and other physical environment characteristics from past to present. In the study area, some analyses were also carried out to determine the annual ring growth relations, not only on the climatic features, but also on the currents that represents the movement of water that is channelled after landing on the earth. The bootstrap correlation coefficients were calculated to determine the relationships between the regional chronologies and the physical geographic factors, and the moving correlation function were used to examine the time-dependent changes of the relationships, and GAMM was used to reveal the nonlinear relationships of the climate on the trees.v According to the results of all these various analyses; (1) The longest site-level chronology (304 year-long) in the study area was obtained for the Oriental spruce species in the Örümcek Forest (ORU) site. The shortest site-level chronology (206 year-long) was obtained for the Scots pine species from the Bakacak Tepe (BAK) site. (2) The correlation coefficient values between the site-level chronologies with different species and the climate data showed that the species in the similar habitat in the study area have common responses to the climate. According to these values, the late winter and early spring temperatures and May precipitation have significant and positive effects on the radial growth in the study area. (3) In the moving correlation analyses, which the temporal relationships and stationarity of the climatic factors that affect the radial growth, the relationships vary in the time interval (1930 – 2020). There are also differences in the growth relationships under similar climatic conditions in the study area. Accordingly, it was determined that precipitation showed more stable relations than temperature on Scotch pine trees, whereas temperature showed more stable relations with precipitation in Eastern spruce trees. (4) In the GAMM analysis, nonlinear growth relationships are examined between climatic factors and radial growth, it was determined that 2 °C – 4 °C mean temperature in the January – April period positively affected the radial growth of Scots pine and spruce trees. On the other hand, the total May – June precipitation (130 – 175 mm for Scots pine; 140 – 185 mm for Oriental spruce) positively affects the radial growth. (5) The changing climatic conditions in the study area were effective both on the species and the streamflow. Especially, the seasonal trends in climate and the complex effects of climatic factors on the study area led to significant inconsistencies in tree ring - climate growth relationships. For this reason, climatic variability found to be a major obstacle in determining backward relationships in climate and streamflow reconstruction experiments in this study area. In addition, the negative effect of natural processes on the streamflow for the Eastern Black Sea region as well as the increasing human impact can be observed both on the streamflow and the tree rings. Such studies will contribute to the understanding of the effects of climate change in areas where complex relationships are observed in environmental conditions depending on the topographic structure in the Eastern Black Sea region.