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

Abstract

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.

Stable Isotopes in Tree Rings of Pinus heldreichii Can Indicate Climate Variability over the Eastern Mediterranean Region

“…These results are in general agreement with an earlier study by Hafner et al [50] that confirm a robust positive relationship between δ 13 C and δ 18 O values and summer temperature, and a negative relationship with precipitation in the southeastern European Alps. Compared to the results of Levanič et al [24], we observe a somewhat stronger relationship between δ 13 C and summer precipitation. They found correlations between δ 13 C and JJA temperature up to 0.6, although it was only −0.51 for JJA precipitation over the Balkan Peninsula.…”

“…In this study, we present a 487-year-long TRW chronology, thus extending the chronology for this region by 50 years [24,30]. This is also the first study to use stable carbon and oxygen isotopes for climate reconstruction in this geographical region.…”

“…In this study, we present a 487-year-long TRW chronology, thus extending the chronology for this region by 50 years [24,30]. Because the climate signal in TRW chronologies of P. heldreichii is relatively limited for robust climate reconstruction (also shown by [24]), we tested the hypothesis that TRSIs (δ 13 C and δ 18 O values) are better proxies for highresolution reconstructions of hydroclimatic variability. Indeed, our results show higher correlations between TRSIs and climate parameters compared to TRW.…”

“…Dendrochronological research in the Dinarides, a mountain range in southern and southeastern Europe that separates the Balkan Peninsula from the Adriatic Sea, has been limited to date. There is therefore huge potential in this region for the development of long, climate-sensitive tree-ring chronologies suitable for the reconstruction of sunshine duration [22], summer temperature [23,24], and drought [25].…”

“…The main aim of this research was therefore to determine whether alternative proxies such as isotope data offer stronger climate reconstruction potential in comparison to conventional TRW chronologies [22,24,30]. Our hypothesis is that isotope data (δ 13 C and δ 18 O values) are better proxies for high-resolution reconstructions of past hydroclimatic variability and can significantly improve the climate signal in Bosnian pine tree-ring data.…”