An empirical resampling method for determining optimal high-pass filters used in correlation-based tree-ring crossdating

Visual crossdating of tree-ring series focusses on high-frequency variations. Automated correlation-based crossdating tools mimic this by transforming raw ring widths into indices that emphasise the high frequency signal, prior to calculating the goodness-of-fit between series. Here we present a resampling methodology to determine the relative merits of alternative simple high-pass filters and demonstrate it using two tree-ring data sets (British Isles oak, New Zealand kauri). Results indicate that: (a) high-pass filtering is a critical step; (b) the efficacy of alternative filters is variable, and; (c) efficacy appears to be species specific. These results have implications for crossdating in the two contexts investigated, and also for future software developments, especially the desirability of flexible implementations of high-pass filtering.     

A multi-century eastern white pine tree-ring chronology developed from salvaged river logs and its utility for dating heritage structures in Canada's National Capital Region

The early settlement history of Canada's National Capital Region, including Ottawa (Ontario) and Gatineau (Québec), was shaped in large part by the towering eastern white pine (Pinus strobus) forests that once covered the Ottawa Valley and fuelled a lucrative lumber export industry spanning the 19th and much of the 20th century. Some of the first dwellings and farmsteads of this era are still standing and serve as reminders of this history. A crucial piece of information in the assessment of a structure's heritage value is its date of construction. Unfortunately, this information is not always known and is approximated based on construction styles and other sources of information. In this study, dendroarchaeology methods are applied to constrain the construction dates of six historic structures in the National Capital Region of 19th century vintage. A multi-century (AD 1670–2009) eastern white pine ring-width chronology was developed for dating the study structures using cross sections from sunken logs recovered from the Ottawa River and cores from live trees from the Petawawa Research Forest. The tree-ring inferred construction dates for the six structures ranged from 1830 to 1878. For most structures, historical records about the property or first inhabitants were available to corroborate the results. The ring-width chronologies of the individual structures were well correlated with the regional chronology (r_avg = 0.63, p ≤ 0.01), and this regional coherence clearly demonstrates the value of tree-rings for heritage structure assessments and reconstructing the settlement history of this region.     

Precision dating of Cook’s Mill,a Civil War era structure in West Virginia

Dendroarchaeology can provide critical understanding of a structure built during key historic periods, such as the American Civil War (1861–1865), when historical documentation is likely to be sparse or incomplete. Cook’s Mill is located in Greenville, West Virginia and extensive information derived from deeds, court records, wills, and oral history places the present mill’s original construction in 1857. The American Civil War began shortly after its construction and military conflict in the area led to the burning of several key structures, one of which was an unknown mill in Greenville (formerly Centerville). Written history suggests the mill is original and survived the American Civil War, however we used dendroarchaeology to confirm its precise date of construction. We collected 46 samples from the mill and 6 cross sections from a nearby exhumed bridge for dendrochronological dating. The mill was constructed with white oak (Quercus alba) and tulip poplar (Liriodendron tulipifera) logs and the bridge samples were white oak. We visually and statistically crossdated 32 white oak samples from the mill and bridge by comparing them to a local chronology developed for this study and two regional oak chronologies from the International Tree-Ring Data Bank. Based on terminal ring attributes and cutting date years we were able to provide a suggested construction date of the spring or early summer of 1868. This date suggests Cook’s Mill was the mill burned during military conflict in the area and that the current structure was subsequently rebuilt following the conclusion of the war.     

Multi-proxy crossdating extends the longest high-elevation tree-ring chronology from the Mediterranean

Annually precise dating is the cornerstone of dendrochronology. The accurate crossdating of relict wood is, however, frequently challenged during early chronology periods when sample replication is typically low. Here we present a multi-proxy approach in which stable carbon (δ¹³C) and radiocarbon (¹⁴C) isotope data are used to evaluate and correct dating errors in the early period of the longest high-elevation tree-ring chronology from the Mediterranean Basin. The record was initially developed using 878 tree-ring width (TRW) and 192 maximum latewood density (MXD) series from living and relict Bosnian pines (Pinus heldreichii) from Mt. Smolikas in Greece to reconstruct hydroclimate and temperature variability back to the 8th century. New annually resolved and non-pooled δ¹³C series now suggest a re-dating of first millennium relict pine samples during a period when sample replication was too low for proper TRW and/or MXD crossdating. The associated correction shifts the start of the Mt. Smolikas chronology from 575 back to 468 CE, a change independently confirmed by wiggle-matching annual ¹⁴C data along the 774/775 CE cosmic event. Our study demonstrates the importance of independent age validation for robust chronology development and shows how multi-proxy crossdating can improve dating success during periods of low sample replication.     

Adverse implications of misdating in dendrochronology: Addressing the re-dating of the “Messiah” violin

A recent report by Mondino and Avalle (2009) was widely distributed that demonstrated a re-dating of the famous “Messiah” violin, a violin attributed to Antonio Stradivari with a label date of 1716. An outermost ring date of 1844 is instead suggested rather than dates in the 1680s reported in previous studies. Mondino and Avalle suggest that this outermost ring date supports the attribution of the violin to Jean-Baptiste Vuillaume, a prolific French instrument maker who was well known for his copies of famous instruments. The statistical techniques and exercises used by Mondino and Avalle, however, are problematic and do not support this revised outermost date for the “Messiah” violin. Raw measurement data with original trends are used in their statistical crossdating, properties previously shown to hinder precise crossdating. They then substantiate their re-dating with polynomial trend curves, which has ever been accepted practice in dendrochronology. Furthermore, the authors use re-scaled correlation coefficients and t-values which artificially inflate the strength of the relationship between tree-ring series that are being statistically crossdated. Using the exact same tree-ring data, but using accepted techniques in statistical crossdating (e.g., the removal of all low-frequency trends and autocorrelation), we could not verify the revised dating of the “Messiah” violin. We urge caution for those who intend to use the SynchroSearch software, book, and lesson plans developed and distributed by Mondino and Avalle. This study illustrates the adverse effects possible in dendrochronology when investigators do not adhere to accepted and time-tested techniques, and are not versed in the extensive literature that highlights issues commonly encountered in statistical crossdating.     

The potential of intra-annual density information for crossdating of short tree-ring series

The crossdating of tree-ring series is typically based on tree-ring width sequences, which is a crude abstraction of the growth signal stored in tree rings. In contrast, intra-annual wood density data allows a much more detailed comparison of wood growth processes and new measurement techniques scale well to measure large amounts of samples. Thus, chronologies of intra-annual densitometric curves can be built. Here, we investigate to what extent intra-annual wood density information can improve crossdating. We evaluate different approaches on a data set of Norway spruce trees (Picea abies) and compare the results to standard methods that are based on ring width or maximum density. Our results show that intra-annual densitometric data indeed increases crossdating success rate notably for short tree ring series that cover less than 25 years.     

History of the Department of Pediatrics Yale University School of Medicine.

The history of pediatrics at the Yale University School of Medicine can be divided into eight historical eras. The "Paleohistorical Era" included colonial figures such as Governor John Winthrop and Hezekiah Beardsley who wrote about children''s disease in colonial times. Eli Ives, Professor of the Diseases of Children at Yale Medical School gave the first systematic pediatric course in America in the first half of the nineteenth century. During the second era, from 1830-1920, the New Haven Hospital was opened. An affiliation between Yale University and the New Haven Hospital led to the formal establishment of clinical departments including pediatrics in the early 20th century. Six eras coinciding with successive pediatric chairman have led the department to its present respected position in American pediatrics. The department''s 75th anniversary in 1996 is an occasion to recognize many of the department''s accomplishments and leaders over the years. It is also a time to reaffirm the mission of the department: to the health needs of the children of Connecticut and beyond, to the advancement of scientific knowledge of infants and children and their diseases, and to the training and educational of the pediatric clinicians, educators and investigators of the future.     

Precise tree-ring dating of building activities despite the absence of bark: A case-study on medieval church roofs in Damme,Belgium

A detailed dendrochronological survey was performed on the medieval roofs of the Church of Our Lady (CoOL) in Damme, Belgium. Seen its complex architectural history, special attention was paid to the identification of consecutive building phases, based on combined architectural historical research and tree-ring dating. In total 64 increment cores were taken throughout the roof structures of the CoOL. All roof timbers are made of European oak (Quercus robur/petraea), of which only few have surviving sapwood or bark. Tree-ring dating confirms the late 13th/early 14th century construction date of the roofs. For all chronologies that were composed, the highest correlation values are found with reference chronologies covering the catchment area of the river Meuse. From the dating results of the timbers of the CoOL it becomes clear that the same timber source was used for nearly a century. On several of the examined roof timbers, rafting joints were observed, demonstrating that the timbers were indeed tied together as a raft and floated down the river.By implementing sapwood estimates in a Bayesian chronological model (OxCal), tree-ring series with surviving sapwood from coeval roof structures were combined in order to narrow down the time range for the felling date. Based on the refined interpretation of the felling dates, several consecutive building phases can now be identified and dated, leading to a new interpretation of the architectural history of the CoOL. Intriguingly, a marked interruption in building activities is observed around 1300. Probably this is related to the instable political situation at that time, caused by the armed conflict that emerged between the Count of Flanders and the king of France. Since Damme served as the outport of the riotous city of Bruges, it was alternately seized by the French and Flemish, both consuming considerable amounts of timber and other building materials for military fortifications. Potentially this led to a shortage in building materials and provoked a stop in building activities.This paper demonstrates the power of Bayesian models to refine the interpretation of dendrochronological dates in architectural analyses of medieval historical buildings.     

Visualizing the internal structure of polyethylene glycol-impregnated wood by digital breast tomosynthesis

This study proposes digital breast tomosynthesis (DBT) as a low-tube-voltage method for imaging wood artifacts treated with polyethylene glycol (PEG). In case of general clinical X-ray Computed Tomography (X-CT), PEG-impregnated wood images typically suffer from low contrast between the PEG and the tree-ring. Because X-CT uses high-tube-voltage X-rays that have high energy, they are transmitted regardless of the X-ray absorption difference of the substance, and therefore, it is not suitable for imaging PEG-impregnated wood. Mammography uses low-tube-voltage X-rays, and therefore, it is suitable for delineating substances with small X-ray absorption differences. However, although mammography can produce high-contrast images of wood, it cannot distinguish three-dimensional (3D) structures such as tree rings, because those are projection images. DBT is a type of mammography used to enhance contrast using low-tube voltage, and it enables imaging 3D structures by exposure X-rays to objects several times changing the exposure angle, and it can obtain quasi-computed tomography. Therefore, we believe that by applying DBT to dendroarchaeology, it would be possible to obtain high-contrast, high-resolution images in the visualization of the internal structure of wood.In this study, we used clinical X-CT, mammography, and DBT to obtain images of wood after PEG impregnation, and we evaluated the internal structure of the wood and the visibility of annual rings. We obtained DBT images as a tomogram with a thickness of 1 mm, which eliminated the distortion of tree rings in the sagittal direction and duplication of the PEG and the tree-ring. Further, tree-rings were easily visualized without a noticeable blur, and the DBT contrast was improved compared to clinical X-CT contrast because DBT was performed at low voltage. Important wooden artifacts excavated from ruins were preserved by PEG. Therefore, this method can be expected to become a very useful tool for dendroarchaeology when used as a complementary tool for microfocus X-CT.     

A 781-year oak tree-ring chronology for the Middle Ages archaeological dating in Maramureș (Eastern Europe)

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 socio-economic 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.     

Preliminary dendrochronological studies on Populus euphratica in the lower reaches of the Heihe River basin in northwest China

To date, preliminary dendrochronological studies of Euphrates poplar trees have not been reported, even though some dendrohydrological studies have been performed. Based on 11 sites in the Ejin Oasis, located in the lower reaches of the Heihe River basin in northwest China, our studies of Euphrates poplar trees concentrates on the characteristics of the tree-ring structure and the stem radial growth, which is the foundation of accurate crossdating and detrending. The results indicate that the Euphrates poplar trees studied have identifiable ring boundaries; the narrow rings and the same ring width variation pattern make the crossdating achievable. The local habitat, the stem radial growth trend of the poplar trees and the completeness of cores should be valued when selecting a detrending method. The complex ring width variation pattern of the poplar trees in the area suggest that comprehensive sampling and preliminary dendrochronological studies are required to gain insights into the spatiotemporal growth patterns of the poplar trees and their relationship with the changing water environment.     

"Kissing a Baby Is Not at All Good for Him": Infant Mortality, Medicine, and Colonial Modernity in the U.S.-Occupied Philippines

Feminist scholars have begun to consider the ways indigenous practices of child rearing were and are challenged in (post)colonial discourse and practice, and how these practices have become a terrain on which definitions of nation, state, and economy are contested. In this article, I adopt a historical anthropological approach to consider how Filipino child-rearing strategies were described and stigmatized in educational, public health, and public welfare discourses in the U.S.-occupied Philippines in the early 20th century. I demonstrate how public health practices and discourses that were generated as part of a "benevolent" campaign against high rates of infant mortality were strategically used as a weapon against Filipino arguments for independence. I also consider how discourses constructing Filipino caregivers as overly indulgent were linked to metropolitan concerns about production of the "new industrial man" and were used to develop a racialized critique of the cultural practices of Filipinos.     

Drought as an Inciting Mortality Factor in Scots Pine Stands of the Valais, Switzerland

During the 20th century, high mortality rates of Scots pine (Pinus silvestris L.) have been observed over large areas in the Rhône valley (Valais, Switzerland) and in other dry valleys of the European Alps. In this study, we evaluated drought as a possible inciting factor of Scots pine decline in the Valais. Averaged tree-ring widths, standardized tree-ring series, and estimated annual mortality risks were related to a drought index. Correlations between drought indices and standardized tree-ring series from 11 sites showed a moderate association. Several drought years and drought periods could be detected since 1864 that coincided with decreased growth. Although single, extreme drought years had generally a short-term, reversible effect on tree growth, multi-year drought initiated prolonged growth decreases that increased a tree’s long-term risk of death. Tree death occurred generally several years or even decades after the drought. In conclusion, drought has a limiting effect on tree growth and acts as a bottleneck event in triggering Scots pine decline in the Valais.     

Non-destructive tree-ring measurements using a clinical 3T-MRI for archaeology

For dendrochronology, both high spatial resolution and a wide imaging area are required. However, there has been no study to satisfy these two requirement for a tree-ring measurement method using magnetic resonance imaging (MRI). In this study, we developed a ring-width measurement method (ultra-high-resolution T2 weighted imaging: uHR-T2WI) using clinical MRI that can scan images at high resolution and over a wide sample area for waterlogged wood, by repeating small fields of view (FOV).Incidentally, until now, the method using X-ray computed tomography (X-CT) has been developed for non-destructive ring-width measurement for analysis of wooden cultural heritage and excavated wooden artifacts, and is mainly successful for dried samples with a low moisture content. However, the contrast of X-CT images tends to reduce as the water content increases, and it has been reported that the attempts to visualize waterlogged and PEG-impregnated archaeological oak wood were unsuccessful owing to a low degree of contrast between the water/PEG and the preserved wood (Bill et al., 2012).Actually, the archaeologically excavated wood generally has very high moisture content (400%–800%), thereby reducing the suitability of X-CT for tree-ring analysis.On the other hand, MRI equipment images the density and state of hydrogen nuclei, and so the expected quality of MRI improves as the moisture content of the wood increases.With these factors, to use both modality complementary will be very useful for dendroarchaeology. However, direct comparison of the suitable range of each modality has not been reported. Therefore, we examined the difference between X-CT and MRI related to moisture content of wood, and examined the range of adaptation for each modality as a function of moisture content.By using the proposed method, we then obtained a tree-ring width series and evaluated the usefulness of the proposed method. The uHR-T2WI method was able to obtain tree-ring width series comparable to those of an optical scanner from images acquired at a spatial resolution of 0.05 mm in high moisture content wood. The results show that wood with a high moisture content (e.g., waterlogged wood measured immediately after excavation, or high-water-content lacquered wooden cultural property) can now be successfully analyzed as non-destructive methods with MRI.In conclusion, the complementarity of both MRI and X-CT will be very useful as non-destructive inspection methods for dendroarchaeology. Although further research should consider more wood species, our study suggests that the proposed method will significantly advance the field of dendrochronology, particularly when related to dendroarchaeology.     

Evaluation of X-ray densitometry to identify tree-ring boundaries of two deciduous species from semi-arid forests in Brazil

The presence of visible annual rings in semi-arid tropical trees may allow the application of dendrochronological methods. However, variation in water availability may cause the formation of narrow, irregular ill- or non-defined annual rings hindering the correct dating of tree-ring series. We aimed to evaluate X-ray densitometry as a method to identify tree rings of two deciduous tree species from the Caatinga forest, a semi-arid region in the northeast of Brazil, and compare with two other methods commonly used in dendrochronology, the sliding-stage micrometer and image analysis. Xylem was observed macro- and microscopically and wood anatomical features were assessed in Aspidosperma pyrifolium and Poincianella pyramidalis trees. In both species, tree-ring boundaries were identified considering intra-annual density patterns and wood anatomical features. No significant differences in tree-ring widths were found among methods. X-ray densitometry measurements showed a positive correlation with the measurements obtained with image analysis and sliding-stage micrometer in A. pyrifolium and P. pyramidalis, revealing the high reliability of the methods used. However, inter-correlation of tree-ring width series showed differences in the accuracy of crossdating across measuring methods. The maximum, mean and minimum density values were species-dependent, with mean wood density of A. pyrifolium lower than P. pyramidalis. Our results highlight X-ray densitometry as an important and complementary tool to identify tree-rings boundaries in semi-arid tree species, especially in A. pyrifolium. Along with other measuring methods, it may provide higher accuracy in dendrochronological studies in semi-arid or subtropical environments.     

Tree rings and ‘El Año del Hambre’ in Mexico

Mexico has a wealth of historical information regarding extreme climate, famine and disease in the colonial period and even in prehispanic times. The recent development of long tree-ring chronologies throughout Mexico now allows comparison between records of past climate and socioeconomic conditions. North American tree-ring data indicate that, for the 3 consecutive years from 1785 to 1787, a major drought occurred across Mexico and the central United States with the most intense conditions extending north from Zacatecas into Texas. This period included the infamous ‘El Año del Hambre,’ one of greatest famines in Mexican history. The tree-ring data are also correlated with maize yield in central Mexico and with the value of Church tithes normally paid with agricultural goods. Drought and crop failure caused the dramatic inflation of crop value and Church tithes in 1786–1787 when tree-ring data indicate that the 1780s drought was most extreme.     

Tree-ring patterns and climate response of Mediterranean fir populations in Central Greece

Central Greece is the distribution common area of the endemic fir species Abies cephalonica and Abies borisii-regis. Forests fires and fir decline are some of the problems both species encountered during the past decades, with these problems being exacerbated lately by climate change. The present research investigates tree-ring patterns and climate responses of three fir populations along a latitudinal gradient in Central Greece. All three populations were homogeneous in their dendrometric, silvicultural and site characteristics but were phenotypically different. The analysis of tree-ring widths site chronologies revealed that 59% of their variability interprets common tree-ring patterns whereas another 25% interprets their differences as they appear from a south to north direction. This variability in tree-ring widths is proportional to the variability observed for precipitation, temperature and drought from a south to north direction in this region. The tree-ring to climate relationships revealed that the main climatic factor affecting fir tree-ring width is late spring and summer precipitation to which is positively correlated. Also, tree-ring widths were positively affected by the temperatures of the October and April before the growing season. However, June drought adversely affected tree-ring widths of the northern site while it positively affected them at the beginning of the spring season, especially for the southern site and in September for the northern sites. All dendrochronological statistics, tree-ring patterns and climate-growth relationships show a south to north trend following the climatic and phenotypic (species) variation observed to the same direction for fir populations in Central Greece.     

Statistical and visual crossdating in R using the dplR library

I demonstrate new functionality for the Dendrochronology Program Library in R (dplR) that allows for flexible statistical crossdating of tree-ring data. Using a well-dated ring-width file, I give examples of how dplR can be used to examine correlations between each series and a master chronology according to overlapping time periods (segments) specified by the user; examine moving correlations of suspect series; and compute cross-correlation functions to identify specific dating issues. I also show how automatically generated skeleton plots can be used to visually crossdate. Much of the terminology and approach used for crossdating in dplR will be familiar to users of COFECHA.     

Crossdating Juniperus procera from North Gondar, Ethiopia

The application of dendrochronology in (sub)tropical regions has been limited by the difficulty in finding trees with distinct annual rings that can be crossdated. Here, we report successful crossdating of Juniperus procera trees from North Gondar, Ethiopia. The trees form annual rings in response to a unimodal rainfall regime. The selection of mesic locations ensured that the trees did not respond to intra-seasonal weather anomalies. Crossdating was achieved by comparison of the wood anatomy directly on the surface of the core samples and purpose-adapted skeleton plotting. Wood-anatomical anomalies, such as false and indistinct rings, were regarded as potentially replicated features and used in crossdating. COFECHA yielded site-specific mean series inter-correlations between 0.52 and 0.59. AMS radiocarbon dating during the bomb era indicated that dating uncertainty is ±1 year.     

Ancient juniper trees growing on cliffs: toward a long Mediterranean tree-ring chronology

Juniperus phoenicea is a tree that can grow on vertical cliff faces in dry and warm Mediterranean climate conditions. These trees are adapted to extreme growing conditions where the main constraints are verticality, compact hard limestone, and low water supply. They respond to these constraints via various specific features and high longevity. The objective of this study is to confirm whether or not their tree-rings are annual in order to specify growth strategies and accurately date these trees. Trunk morphology, anatomical wood anomalies and radial growth were analyzed on 53 trees in the Ardèche canyon. Crossdating of the ring widths using traditional dendrochronological techniques was unsuccessful, so radiocarbon dating of tree pith was used to assess tree age, and wiggle-match dating was used to test for differences between number of rings counted and radiocarbon dates. Radiocarbon dates span the period 2520–685 BP. Minimal difference between radiocarbon dates and ring counts was apparently small—missing rings occur, but not in large numbers. Tree-ring formation is annual and radial growth is low, which creates stunted old trees. Such old living trees are uncommon in the Mediterranean basin, especially at low elevation. They can provide long tree-ring chronologies back to 792–524 cal BC. Results from the radiocarbon dating indicate that accurate annual dating of these rings may be possible by crossdating. J. phoenicea growing on cliffs offer a valuable model to better understand cliff population ecology and the functional responses of trees that can live in harsh environmental conditions.