Stable Isotopes Reveal Climate Signal Hidden in Tree Rings of Endemic Balkan Pines.

Studies report the good potential of Pinus heldreichii (PIHE) and Pinus peuce (PIPE) for developing long chronologies from living trees and warn that the climate signal is weak in tree-ring widths of PIHE, and particularly PIPE. The goals of the study were to develop long chronologies, and to analyze the climate–growth relationship and potential for long climate reconstructions using tree-ring widths (TRW) and stable carbon isotopes ratios (δ¹³C) in tree rings at the northern edge of species distribution in the eastern part of Montenegro. The PIHE TRW chronology covers the period 1571–2013 (443 years) and the PIPE TRW chronology 1521–2013 (493 years). The temperature signal in PIHE TRW is weak and the precipitation signal is non-existent. PIPE has no climate signal in TRW. Both studied species have very similar δ¹³C chronologies, which allows us to merge isotope chronologies into a single composite δ¹³C Pinus chronology. The composite chronology has a strong signal related to average monthly temperature in June, July, and August and monthly values for cloudiness in July and August, with r > 0.6 and r < −0.6 for individual months, respectively. The climate signal was enhanced when June, July, and August values were merged into seasonal variables. The temporal stability of temperature, precipitation and cloudiness signals is consistent. The spatial extent of the δ¹³C chronology extends over a very large region, including all surrounding countries. [ABSTRACT FROM AUTHOR]