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2 2015

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Long-term summer temperature variations in the Pyrenees from detrended stable carbon isotopes

Esper J., Konter O., Krusic P. J., Saurer M., Holzkämper S., Büntgen U.

Geochronometria

2015

Vol. 42, no.1

53--59

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 treerings, 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 amplitude 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 derived from traditional tree-ring parameters.

Exploring Growth Variability and Crown Vitality of Sessile Oak (Quercus petraea) in the Czech Republic

Rybníček M., Čermák P., Žid T., Kolář T., Trnka M., Büntgen U.

Geochronometria

2015

Vol. 42, no.1

17--27

Unraveling climatic effects on growth of oak — Europe’s most ecologically and economically important forest species — has been the subject of many recent studies; however, more insight based on field data is necessary to better understand the relationship between climate and tree growth and to adapt forest management strategies to future climate change. In this report, we explore the influence of temperature, precipitation and drought variability on the productivity and vitality of oak stands in the Czech Highlands. We collected 180 cores from mature oaks (Quercus petraea) at four forest stands in the Czech Drahany Highlands. Standard dendro-methods were used for sample preparation, ring width measurements, cross-dating, chronology development, and the assessment of growth-climate response patterns. Crown vitality was also evaluated, using the modified ICP Forests methodology. Late spring precipitation totals between May and June as well as the mean July temperature for the year of ring formation were found to be the most important factors for oak growth, whereas crown condition was significantly affected by spring and summer drought. This study is representative for similar bio-ecological habitats across Central Europe and can serve as a dendroclimatological blueprint for earlier periods for which detailed meteorological information is missing.