Dating the Wood from the Trees

1995

Absolutely dated tree-ring series from the Early Middle Ages and later, derived from Dutch archaeological and historical contexts, are clustered into three master chronologies. In geographical terms, the distribution of the sites represented by the chronologies differs markedly. Chronology NLHist_1 (AD 427 -1752; 259 series) mainly represents sites in the south of the Netherlands; NLHist_2 (AD 1023 -1666; 195 series) consists of timbers applied in the central and northern parts, and NLHist_3 (AD 1041 -1346; 30 series) is composed of timbers from sites along the coast and in the IJssel and Vecht Valley. The new chronologies are well suited as a reference to date oak from Medieval archaeological sites and historical buildings in the Netherlands.

Radiocarbon

Measurements of the stable isotope ratio13C/12C, relative to PDB, were made for fractionation correction purposes on all oak samples used in the Irish oak14C calibration curve. Stable isotope data have not been published previously. We have collated the stable isotope data from the calibration work, carried out some further measurements to investigate anomalies in the original results, and generated tables of data that include site and tree information pertaining to both stable isotopes and source material for14C calibration measurements. The data suggest that land-grown trees tend to be isotopically lighter than bog-grown wood, and that the Irish trees used in the calibration exercise tend to be isotopically heavier than those from Scotland and England. Preliminary analysis of the data is given.

Radiocarbon, 2004

Often it is not possible to date a sample of wood from the final growth ring of the tree from which it came. In these cases, an “old-wood offset” is apparent. A number of quantitative approaches for the assessment of this offset are available, dependent on the actual tree rings that have been dated. A range of examples are given, demonstrating how such radiocarbon measurements can be interpreted using additional information from archaeology and dendrochronology.

wsl.ch

Vernacular Architecture, 1982

2005

Isotope dendroclimatology is a relatively new field investigating environmental factors that control the radial growth of trees. Tree-ring series of sub-fossil bog oaks can be dated from sites across northwest Europe indicating that the environmental change(s) were regional rather than local. Bog oaks show characteristic periods of suppressed growth thought to have resulted from changes in the hydrological status of bogs towards either wetter or drier conditions. This study investigates relative changes in stable carbon (δ 13 C) and oxygen (δ 18 O) isotope content in phases of suppressed and normal growth in three bog oaks dated as c. 200 BC to 150 AD from Zwolle, eastern Netherlands. Bog oaks show no clear relationship between tree-ring width and isotopic composition although one tree exhibited relatively depleted values of 13 C and 18 O with suppressed growth. Suppressed ring growth is characterised by the formation of earlywood only, possibly as a result of hydrologic alterations that limited the formation of latewood, which would otherwise have locked up a detectable signal in stable isotopic shift.

MethodsX, 2018

In the process of dating the oldest trees, which are often hollow, we developed a new method that combines treering cross dating and wiggle matching radiocarbon techniques on wood samples extracted from the stem and from exposed roots. The method can be illustrated by the following steps: crossdated tree-ring series from trunk cores reveal a multi-century tree age, and the hollow section is large enough to contain several more years (decades to centuries) exposed roots can be cored for acquiring wood samples older than the stem cores and for construction of a floating root average tree-ring series if synchronization between stem and exposed roots is unclear, proceed to date the root wood samples by radiocarbon wiggle matching; match root and stem tree-ring series within the radiocarbon-dated period to more accurately date the tree. This new multistep dating method allowed for refining the age estimation of the oldest Pinus heldreichii tree in Pollino National Park by 166 years, to 789 CE. This tree, which we named Italus, was 1229 years old in 2017, making it the oldest, scientifically dated, living tree in Europe. Any study that relies on tree age determination for paleo-reconstructions, for biological and genetic research on what controls longevity, or for understanding structural dynamics and succession in old-growth forests, would potentially benefit from the multistep dating method we tested.

2005

Jansma, E. & E. Hanraets, 2004. Dating Flanders : towards a Flemish tree-ring chronology of oak. In: Jansma et al. (eds.), 2004., 2004

Since a few years, we have been systematically investigating oak from archaeological excavations in western Flanders. These series are well-suited for the production of a regional master chronology that can be used asa standard for dating. By presenting this chronology here, we hope to lay the foundation for further dendrochronological work in this region.

Drvna industrija, 2014

Palaeogeography, Palaeoclimatology, Palaeoecology, 2015

Subfossil bog oak material is an important palaeo-climate and hydrology proxy for the Holocene. A correct interpretation of the subfossil material in terms of growth and population dynamics requires understanding of the underlying processes. The catastrophic rewetting after dyke-failure of a drained peatland forest in NE-Germany provides a unique natural laboratory to calibrate bog oak growth pattern with a known event. Growth differences among groups of currently vital, damaged and dead oaks in the years before the flooding were used to estimate the adaptation potential in dependence on age, tree-size, competition class and groundwater table. Dendrochronological analysis of growth patterns and wood-anatomical parameters revealed changes in the wood in reaction to sharp hydrological shifts (drainage and rewetting). Group specific chronologies were contrasted against instrumental data to evaluate the influence of climate and hydrology on radial growth of oak. Groundwater table proved to be the overriding factor influencing oak growth at our site, already during times of intensive drainage. Results show an influence of micro-site conditions (elevation above soil-water level) along with a higher chance for slower growing and possibly former suppressed trees to survive the catastrophic rewetting. These trees display a typical ring-pattern with four to five years of depressed growth and a subsequent recovery, characterised by a significant increase in ring-width, especially in the earlywood. Trees that died or were damaged following the rewetting typically show strongly reduced latewood-width before they gradually die-off. Our findings are discussed with regard to the interpretation of subfossil bog oak material and a modified version of release detection analysis is proposed as a tool to sharpen the identification of hydrological shifts in bog oak material. The results of the study can contribute to a better understanding of ecophysiological mechanisms underlying growth reactions (and adaptation potential) of oaks to prevailing high water levels.

Archaeology International, 2000

By studying the annual growth rings of long-lived trees, and those preserved in ancient timbers that have survived in waterlogged or very dry conditions, it is possible to date past events in calen dar years and to investigate climatic and other environmental changes. Dendrochronology has many applications, including the dating of buildings and ships and the calibration of the radio carbon timescale that is so widely used in archaeology. Here the technique is outlined and some recent applications of it in Eng land are described.

Dendrochronologia, 2018

From 1997 to the present, a sustained project in the Maramureș region in Romania was completed with the construction of a 781-year oak tree-ring chronology. A total of 395 samples from living trees and 429 from archaeological wood were analysed with dendrochronological methods. The study aimed to provide the scientific community with a new oak chronology that could be applied in dendroarchaeology, dendroclimatology and dendroecology studies and also for interpreting past socioeconomic events. Furthermore, we studied the number of sapwood rings and the growth pattern for different time periods. The chronology covered the continuous period of A.D. 1236-2016. From the 824 samples collected, we separated 271 tree-ring series into a new chronology (A.D. 1406-2016), which fulfilled all the criteria necessary to reconstruct past climate and environmental changes. The resulting new tree-ring chronology indicated robust signal series intercorrelation (r = 0.55) and an average mean sensitivity of 0.21. Based on an analysis of the sapwood, we recommend estimating a number between 8 and 32 rings to the date of final ring for 95% confidence range of mean on the for felling in the Maramureș region. Additionally, we observed that the number of sapwood rings was not correlated with altitude or oak tree species.