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

Jernej Jevšenak,Polona Hafner,Tom Levanič

doi:10.3390/atmos11020135

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.

Highlights

In the Mediterranean region of limited water resources, reliable climate predictions on seasonal to decadal timescales are essential in developing effective strategies for mitigating the environmental and socioeconomic impacts of climate change
In addition to the tree-ring widths (TRW) chronology, we developed a δ13 C chronology to test it as a potential proxy for the reconstruction of climate in the Balkan Peninsula
Both studied pines are long-lived species and, even with a limited number of cored trees, it was possible to construct more than 440-year chronologies

Summary

Introduction

In the Mediterranean region of limited water resources, reliable climate predictions on seasonal to decadal timescales are essential in developing effective strategies for mitigating the environmental and socioeconomic impacts of climate change. The increase in temperature and decrease in precipitation, as forecast by climate change scenarios for the Eastern Mediterranean region, pose one of the main challenges for the sustainable management of natural resources in countries of the Adriatic and Aegean regions [1,2]. The Balkan Peninsula is known for its relict tree species, due to late glacial refugia and some more or less untouched forest sites [3,4,5]. Two Balkan tree species, Pinus heldreichii H. (Macedonian pine), are interesting in terms of dendroclimatology because they can get very old and grow on extreme sites. Pinus heldreichii and Pinus peuce are long-lived, relict Balkan species growing close to the alpine timberline, where climatic conditions are harsh and limiting for tree growth. Corona et al [7] studied the climate–growth relationship in Larix decidua and Pinus cembra

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