Environmental and climatic signals from stable isotopes in Anatolian tree rings, Turkey

Dendrochronological and oxygen-carbon isotopic analysis was conducted on tree rings collected at two different elevations from three different regions in western Anatolia, Turkey. Tree rings were sampled from Anatolian black pines (Pinus nigra Arn. subsp. pallasiana (Lamb.) Holmboe) of at least 200 years old through an N-S transect covering Bolu-Mengen (north), Kütahya-Simav, and Antalya-Alanya (south) forests. Cellulose was extracted from 5-year blocks of tree rings from lower to upper altitudes in each region. Dendrochronological site chronologies were built for each of the 6 sites, and response to climate was evaluated. The long-term δ ¹³C chronologies comprising the period 1800-2008 strongly decline by an average of 2. 5‰ from the mid-twentieth century, which corresponds with the commencement of industrialization in Turkey. Oxygen isotope (δ ¹⁸O) time series show dominantly low undulations, although some high-frequency variations of up to 6‰ are also observed. As a result of latitude and continent effects, oxygen isotope values of tree rings show an average of 3‰ increase from south (Antalya) to the north (Bolu). Correlations between carbon isotope ratios yield high positive values indicating that industrial pollution exerts a major control on the δ ¹³C systematics of the studied trees. Corrected δ ¹³C ratios are mostly represented by strong positive responses to variations in temperature and precipitation, whereas δ ¹⁸O and summer temperature/precipitation are negatively correlated. Tree-ring widths and δ ¹⁸O display similar responses to the temperature and sensitivity to the climatic impact of historic volcanic eruptions, and changes in the solar irradiance record are also detected in other high-resolution paleoclimate archives for the region.