Scientific merits and analytical challenges of tree-ring densitometry

R.W. was supported by NERC grant NE/K003097/1.X-ray microdensitometry on annually-resolved tree-ring samples has gained an exceptional position in last-millennium paleoclimatology through the maximum latewood density parameter (MXD), but also increasingly through other density parameters. For fifty years, X-ray based measurement techniques have been the de facto standard. However, studies report offsets in the mean levels for MXD measurements derived from different laboratories, indicating challenges of accuracy and precision. Moreover, reflected visible light-based techniques are becoming increasingly popular and wood anatomical techniques are emerging as a potentially powerful pathway to extract density information at the highest resolution. Here we review the current understanding and merits of wood density for tree-ring research, associated microdensitometric techniques, and analytical measurement challenges. The review is further complemented with a careful comparison of new measurements derived at 17 laboratories, using several different techniques. The new experiment allowed us to corroborate and refresh ?long-standing wisdom?, but also provide new insights. Key outcomes include; i) a demonstration of the need for mass/volume based re-calibration to accurately estimate average ring density; ii) a substantiation of systematic differences in MXD measurements that cautions for great care when combining density datasets for climate reconstructions; and iii) insights into the relevance of analytical measurement resolution in signals derived from tree-ring density data. Finally, we provide recommendations expected to facilitate future inter-comparability and interpretations for global change research.Publisher PDFPeer reviewe

Comparing Scots pine tree-ring proxies and detrending methods among sites in Jamtland, west-central Scandinavia

Scots pine tree-ring width (TRW) data from Jamtland in the Central Scandinavian Mountains has been used to reconstruct summer temperatures back to 1630 BC. However, it was recently shown that this reconstruction was of limited spatial importance. In this paper, we aim to explain this limitation in the TRW data as a temperature proxy, as well as assess the temperature information from new maximum latewood density (MXD) data. Furthermore, the effect of two standardization methods is evaluated: regional curve standardization (RCS) and a more traditional standardization, termed "non-RCS" standardization. Three TRW and two MXD sites were analyzed. Our results showed that despite the proximity to the Norwegian Sea, the MXD data is a powerful temperature proxy. Difference among sites in TRW data, especially on decadal timescales, together with a lower temperature association, suggests that other factors, such as changes in the local climate regimes, weakens the temperature signal. In general the RCS method overestimates pine growth trends in the latter half of the twentieth century, a feature not seen when using "non-RCS" standardization. This is likely due to an age-bias of older trees in most recent parts of the tree-ring chronologies. This effect will have consequences when reconstructing climate with tree-ring data. To overcome this problem, all age-classes should be represented throughout a chronology. If this is not possible, the use of "non-RCS" standardization is recommended, although this method results in a loss of low-frequency variability. (C) 2010 Istituto ltaliano di Dendrocronologia. Published by Elsevier GmbH. All rights reserved

The Origin of Tree-Ring Reconstructed Summer Cooling in Northern Europe During the 18th Century Eruption of Laki

Basaltic fissure eruptions, which are characteristic of Icelandic volcanism, are extremely hazardous due to the large quantities of gases and aerosols they release into the atmosphere. The 1783–1784 CE Laki eruption was one of the most significant high-latitude eruptions in the last millennium and had substantial environmental and climatic impacts. Contemporary observations recorded the presence of a sulfuric haze over Iceland and Europe, which caused famine from vegetation damage and resulted in a high occurrence of respiratory illnesses and related mortality. Historical records in northern Europe show that the summer of 1783 was anomalously warm, but regional tree-ring maximum latewood density (MXD) data from that year are low and lead to erroneously colder reconstructed summer temperatures. Here, we measure wood anatomical characteristics of Scots pine (Pinus sylvestris) from Jämtland, Sweden in order to identify the cause of this discrepancy. We show that the presence of intraannual density fluctuations in the majority of 1783 growth rings, a sudden reduction in lumen and cell wall area, and the measurement resolution of traditional X-ray densitometry led to the observed reduced annual MXD value. Multiple independent lines of evidence suggest these anatomical anomalies were most likely the result of direct acidic damage to trees in Northern Europe and that the normal relationship between summer temperature and MXD can be disrupted by this damage. Our study also demonstrates that quantitative wood anatomy offers a high-resolution approach to identifying anomalous years and extreme events in the tree-ring record. © 2022. American Geophysical Union. All Rights Reserved.6 month embargo; first published: 24 January 2022This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

ADVANCE-10K: a European contribution towards a hemispheric dendroclimatology for the Holocene

This editorial introduces a special issue of The Holocene containing 12 papers which represent highlights from a European Commission research project: ‘Analysis of Dendrochronological Variability and Associated Natural Climates in Eurasia – the last 10000 years’ (ADVANCE-10K). The focus is on the climatic implications of dendrochronology and especially on developing an integrated, dendrochronological approach to high-resolution climatic reconstruction in the Holocene, with the ultimate aim of extending this to the global scale. Emphasis is given to: (1) long chronologies from northern Fennoscandia (pine), temperate central and western Europe (oak) and Siberia (larch); (2) the precise climatic signals reflected in these chronologies and possible links to atmospheric circulation patterns; (3) complementary methodologies for extracting climatic information from subfossil trees in a variety of different environmental settings; and (4) the use of a large (subhemispheric) network of tree-ring density data to examine detailed, geographical patterns in climatic varia bility at a high temporal resolution. These studies are placed in their wider context and future directions for research in this field are also highlighted

Reconstructing Holocene climate from tree rings: The potential for a long chronology from the Scottish Highlands

Despite promising research in the 1980s showing the potential of Scots pine (Pinus sylvestris L.) for the reconstruction of past summer temperatures in the Scottish Highlands, little dendroclimatic work has been attempted in this region since. This reflects, in part, the limited number of sparsely distributed remnant natural/ semi-natural pine woodlands in the Scottish Highlands and the lack of old growth forest therein. On average, most of the pine trees dated in this region are around 225 years in age. Here, we present the first results of an ongoing interdisciplinary initiative to develop a long Scottish chronology through the acquisition of modern, historical and subfossil pine material from the native pinewoods, historic structures and lakes of the Scottish Highlands. Radiocarbon dating of 25 subfossil pine timbers recovered from lake sediments identified the presence of preserved material covering the last 8000 years with initial clusters focused on the last two millennia and early-mid Holocene. Although developing a well-replicated 8000 year pine chronology will take many years, this preliminary study indicates that a millennial length pine chronology from the northwest Cairngorm region is a feasible and realistic objective in the near future. The importance of such a record in this climatically important sector of northwest Europe cannot be underestimated.</p

Reconstructions of surface ocean conditions from the North East Atlantic and Nordic Seas during the last millennium

We undertake the first comprehensive effort to integrate North Atlantic marine climate records for the last millennium, highlighting some key components common within this system at a range of temporal and spatial scales. In such an approach, careful consideration needs to be given to the complexities inherent to the marine system. Composites therefore need to be hydrographically constrained and sensitive to both surface water mass variability and three-dimensional ocean dynamics. This study focuses on the northeast (NE) North Atlantic Ocean, particularly sites influenced by the North Atlantic Current. A composite plus regression approach is used to create an inter-regional NE North Atlantic reconstruction of sea surface temperature (SST) for the last 1000 years. We highlight the loss of spatial information associated with large-scale composite reconstructions of the marine environment. Regional reconstructions of SSTs off the Norwegian and Icelandic margins are presented, along with a larger-scale reconstruction spanning the NE North Atlantic. The latter indicates that the �Medieval Climate Anomaly� warming was most pronounced before AD 1200, with a long-term cooling trend apparent after AD 1250. This trend persisted until the early 20th century, while in recent decades temperatures have been similar to those inferred for the �Medieval Climate Anomaly�. The reconstructions are consistent with other independent records of sea-surface and surface air temperatures from the region, indicating that they are adequately capturing the climate dynamics of the last millennium. Consequently, this method could potentially be used to develop large-scale reconstructions of SSTs for other hydrographically constrained regions

Scientific Merits and Analytical Challenges of Tree-Ring Densitometry

X‐ray microdensitometry on annually resolved tree‐ring samples has gained an exceptional position in last‐millennium paleoclimatology through the maximum latewood density (MXD) parameter, but also increasingly through other density parameters. For 50 years, X‐ray based measurement techniques have been the de facto standard. However, studies report offsets in the mean levels for MXD measurements derived from different laboratories, indicating challenges of accuracy and precision. Moreover, reflected visible light‐based techniques are becoming increasingly popular, and wood anatomical techniques are emerging as a potentially powerful pathway to extract density information at the highest resolution. Here we review the current understanding and merits of wood density for tree‐ring research, associated microdensitometric techniques, and analytical measurement challenges. The review is further complemented with a careful comparison of new measurements derived at 17 laboratories, using several different techniques. The new experiment allowed us to corroborate and refresh “long‐standing wisdom” but also provide new insights. Key outcomes include (i) a demonstration of the need for mass/volume‐based recalibration to accurately estimate average ring density; (ii) a substantiation of systematic differences in MXD measurements that cautions for great care when combining density data sets for climate reconstructions; and (iii) insights into the relevance of analytical measurement resolution in signals derived from tree‐ring density data. Finally, we provide recommendations expected to facilitate future inter‐comparability and interpretations for global change research