Oliver Konter

Tree-Ring Amplification of the Early Nineteenth-Century Summer Cooling in Central Europe

Annually resolved and absolutely dated tree-ring chronologies are the most important proxy archives to reconstruct climate variability over centuries to millennia. However, the suitability of tree- ...

LONG-TERM SUMMER TEMPERATURE VARIATIONS IN THE PYRENEES FROM DETRENDED STABLE CARBON ISOTOPES

Abstract Substantial effort has recently been put into the development of climate reconstructions from tree-ring stable carbon isotopes, though the interpretation of long-term trends retained in such timeseries remains challenging. Here we use detrended δ13C measurements in Pinus uncinata tree-rings, from the Spanish Pyrenees, to reconstruct decadal variations in summer temperature back to the 13th century. The June-August temperature signal of this reconstruction is attributed using decadally as well as annually resolved, 20th century δ13C data. Results indicate that late 20th century warming has not been unique within the context of the past 750 years. Our reconstruction contains greater am-plitude than previous reconstructions derived from traditional tree-ring density data, and describes particularly cool conditions during the late 19th century. Some of these differences, including early warm periods in the 14th and 17th centuries, have been retained via δ13C timeseries detrending - a novel approach in tree-ring stable isotope chronology development. The overall reduced variance in earlier studies points to an underestimation of pre-instrumental summer temperature variability de-rived from traditional tree-ring parameters.

New Tree-Ring Evidence from the Pyrenees Reveals Western Mediterranean Climate Variability since Medieval Times

AbstractPaleoclimatic evidence is necessary to place the current warming and drying of the western Mediterranean basin in a long-term perspective of natural climate variability. Annually resolved and absolutely dated temperature proxies south of the European Alps that extend back into medieval times are, however, mainly limited to measurements of maximum latewood density (MXD) from high-elevation conifers. Here, the authors present the world’s best replicated MXD site chronology of 414 living and relict Pinus uncinata trees found >2200 m above mean sea level (MSL) in the Spanish central Pyrenees. This composite record correlates significantly (p ≤ 0.01) with May–June and August–September mean temperatures over most of the Iberian Peninsula and northern Africa (r = 0.72; 1950–2014). Spanning the period 1186–2014 of the Common Era (CE), the new reconstruction reveals overall warmer conditions around 1200 and 1400, and again after around 1850. The coldest reconstructed summer in 1258 (−4.4°C compared to 1961...

Effects of host abundance on larch budmoth outbreaks in the European Alps

Outbreaks of the larch budmoth (LBM) in the European Alps are among the most documented population cycles and their historical occurrence has been reconstructed over 1200 years. Causes and consequences of cyclic LBM outbreaks are poorly understood and little is known about populations near the margin of the hosts distribution range. In the present study, we quantify historical LBM outbreaks and associated growth reductions in host trees (European larch). Tree‐ring data collected from 18 sites between approximately 500 and 1700 m a.s.l. in the Northern pre‐Alps are compared with data from the Western Alps and Tatra Mountains, as well as with nonhost Norway spruce. Highly synchronized host and nonhost growth in the Northern pre‐Alps shows that periodic LBM outbreaks are largely absent near the distributional limit of larch. By contrast, growth patterns in the Western Alps LBM core region are indicative of LBM events. Although climatic conditions in the Northern pre‐Alps and Tatra Mountains would allow LBM outbreaks, low host plant abundance is likely the key driver for the absence of cyclic outbreaks in these regions. The results obtained in the present study suggest that, in addition to the climatic conditions, host‐species abundance is critically important for the occurrence of periodic LBM outbreaks and the determination of the respective outbreak range.

Comparison of δ13C and δ18O from cellulose, whole wood, and resin-free whole wood from an old high elevation Pinus uncinata in the Spanish central Pyrenees

ABSTRACT δ13C and δ18O values from sapwood of a single Pinus uncinata tree, from a high elevation site in the Spanish Pyrenees, were determined to evaluate the differences between whole wood and resin-free whole wood. This issue is addressed for the first time with P. uncinata over a 38-year long period. Results are also compared with published isotope values of α-cellulose samples from the same tree. The differences in δ13C and δ18O between whole wood and resin-free whole wood vary within the analytical uncertainty of 0.3 and 0.5 ‰, respectively, indicating that resin extraction is not necessary for sapwood of P. uncinata. Mean differences between cellulose and whole wood are 0.9 ‰ (δ13C) and 5.0 ‰ (δ18O), respectively. However, further analyses of different species and other sites are needed to evaluate whether the findings reported here are coherent more generally.