Juniper is one of the three main tree species in Central Anatolia, where it grows under extreme environmental conditions. Although dendrochronological studies of juniper are challenging because of cross-dating problems, these types of studies on long-lived tree species have the potential to provide long time series, which reflect changes in climatic conditions. Juniper has been neglected as a scientific research subject in Turkey due to degraded populations and low economic expectations. This study analysed the distribution and present state of Juniperus spp. (Juniperus excelsa M. Bieb., Juniperus oxycedrus L., and Juniperus foetidissima Willd.) stands and used dendrochronological data to examine relationships between growth and environmental parameters. We hypothesised that there may be differences in the radial growth of juniper in areas of different exposure in drought regions. During a field survey, we sampled 31 plots of 25 m × 20 m and data, including information on wood cores, were collected. For dendrochronological investigation, 95 wood cores were manually measured and cross-dated. Residual chronologies of tree-ring width series of juniper from four wind directions and regional chronology of Kirikkale and Ankara Province were provided and similarities between the chronologies were tested using Gleichläufigkeits test. The relationships between climate parameters and growth were examined using a simple correlation analysis and multiple linear regression model analysis in SAS 9.0 program and response function analysis in the DENROCLIM2002 program. The results of this study indicated that Juniperus spp. in Central Anatolia are sensitive to environmental parameters and mainly respond to changes in precipitation. Juniper show differences in radial growth in areas of different exposure in drought regions. We conclude that juniper may offer an excellent opportunity for large-scale dendrochronological and dendroecological studies in drought regions.
Central Anatolia has semiarid ecological conditions that limit tree growth. In addition, long-term human activity has resulted in degradation of existing forests lands. Current forest cover mainly includes oak, juniper, and pine species. In this study, the distribution and present state of Pinus nigra L. and Quercus spp. (Quercus cerris L. and Quercus pubescens L.) mixed stands, and the relationship between different environmental factors and abundance of oaks and pines were analyzed. The results indicate that interactions of environmental variables and human disturbance may have influenced the frequency and abundance of species in the region.
Central Anatolia is one of the semi-arid regions of Turkey that does not offer very suitable conditions for the growth of trees. Tree growth is a process controlled by genetic, environmental and climatic factors. Trees record these signals, which provide valuable scientific data for dendrochronological research. We used raw annual tree-ring width (taken from trees under the age of 100 years) as one of the dendrochronological parameters to compare Juniperus foetidissima and J. excelsa in terms of affecting factors. We compared the annual tree-ring width of both species considering species, locations and research sites of the altitude range of 677–1 400 m a.s.l.. Environmental signals (longitude and latitude, altitude, slope, exposure, human impact and nearest settlement distance), as well as climatic factors (precipitation, temperature, moisture) affecting growth were examined. Results indicate that there is an obvious difference in raw annual tree-ring widths depending on species. J. foetidissima differs from J. excelsa in wider annual tree-ring widths and preferences to a low slope and altitude. While the annual tree-ring width of J. excelsa did not respond to the environmental signals, the annual tree-ring width of J. foetidissima was notably correlated with longitude, latitude, altitude and slope. The most remarkable variables affecting the growth of both species were summer temperatures and moisture.
Background and Purpose: Turkish hazel (Corylus colurna L.) has been overused because of its valuable wood. Recently, Turkish hazel has been found only in small isolated populations, and very small populations within its natural distribution area, so it has been protected under IUCN with the status "Least Concern (LC)". Therefore, the remaining Turkish hazel populations have a critical importance. Genetic conservation of this tree species plays a key role in sustainable forest development. There have been only a few studies of single populations, but an overview including all countries is still missing. The aim of this publication is to give an overview of ecological and economic importance of Turkish hazel, which is considered as a tolerant tree species to climate change, for dry and warm conditions in Central Europe. Materials and Methods: This review paper has been prepared based on the existing literature such as reports, theses, project documents and publications related to Turkish hazel. This paper applies a literature review of the concepts of: i) Distribution and threats of Turkish hazel, ii) Ecological and economic importance, iii) Regeneration, soil demand and shading tolerance, iv) Seed, seedling, plant production and planting, v) Competitiveness in forest communities, vi) Invasiveness and hybridization, and vii) Future stand mixtures. Results and Conclusions: This review paper should interest forest practitioners and scientists in all countries who work with this important and valuable tree species under climate change. At first, an inventory of all populations in each country is needed. For this purpose, research should focus on the cultivation of convenient provenances of Turkish hazel under climate change. Next, genetic differences should be determined in the laboratory using genetic markers. After the assessment of the phenotype and genotype of different provenances, it would be possible to recommend provenance for each ecological condition and assisted migration (AM). Main recommendations for each country are used for selecting and establishing gene conservation units (in-situ and ex-situ) and seed orchards that will ensure the survival of Turkish hazel, and for building the base for cultivation in the future. In addition, the results might be a basis for future provenance tests, plantations and possibilities of assisted migration attempts.
The dendrochronological potential of Juniperus foetidissima, growing in central Anatolia, was assessed. Raw, standard, and residual tree-ring chronologies were prepared for J. foetidissima trees in the Eskişehir region using classical dendrochronological methods for the period between 1875 and 2014. All the chronologies were statistically relevant, and the running correlation, expressed population signal, and mean sensitivity values in the residual tree-ring chronology were within the given limits. Therefore, the residual tree-ring chronologies were used to assess the climate-growth relationship. The relationships between tree-ring width growth and climate variables (mean temperature, monthly sum of precipitation) were investigated using response function analysis (moving windows correlations) in the R platform. Positive or negative relations were found between the residual tree-ring widths and the monthly precipitation and mean temperature, but with low coefficient values. The tree-ring width growth showed a significantly negative response to precipitation in August of the current year for the period in 1977-2001 and 1978-2002 and significantly positive to temperature in June of the current year for the period in 1971-1995, 1972-1996, and 1993-1996. In conclusion, despite some problems with cross-dating, J. foetidissima can generally be used for dendrochronological research and is suitable for developing long-term chronologies.
Trees' height (H) and diameter (D) growth depend on many factors and vary between species. This study examined H and D growth of Juniperus excelsa, J. foetidissima, Pinus nigra, Quercus cerris and Q. pubescens, growing naturally in the Central Anatolian forest steppe and the site conditions (human impact, woody plant coverage, tree density, altitude, exposure) that influence H and D growth. The present study hypothesises that the decline of height growth might indicate limited rainfall in the region. Two datasets were distinguished for the statistical analysis: the first comprised maximum height (MH) and diameter (MD), human impact, woody plant coverage, and tree density of the sampling plots, and the second comprised all measured Hs and Ds of the sampling plots, exposition, and altitude. Variance and correlation analysis were applied to both datasets to determine the relationships between parameters. Non-linear regression analysis was applied to both datasets to provide H-prediction equations. According to the results of statistical analyses applied to two datasets, each tree species reacted differently to the site conditions. However, the most relevant relationship was found between height and diameter growth for all species. The MH-MD and D-H of P. nigra (except the altitude) and Quercus cerris + Q. pubescens (except the human impact) did not respond to any of the site conditions remarkably, while those of J. foetidissima responded to all of the site conditions examined. The H and D of each species were affected by the exposure. While the highest number of trees was found on N-exposed slopes, the heights trees of each species were found on N- and NW-exposed slopes. The results of non-linear regression analysis applied on both datasets of H-prediction equations of each species involved different parameters, even though the diameter was the only relevant variable for height prediction. Although it is not possible to reach a definite conclusion for other species within the scope of this study, P. nigra had a shorter height in Central Anatolia than in areas with better environmental conditions. Height growth might indicate water limitations of Central Anatolian region, but genetic code might be an important factor of how a species will cope with drought.
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