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Comparing the impact of live-tree versus historic-timber data on palaeoenvironmental inferences in tree-ring science, eastern North America
Abstract
Dendroarchaeological data from historic structures and artefacts have the potential to extend tree-ring chronologies spatially and temporally, especially where old-growth forests have been extensively modified or harvested. While these data may contribute to an improved understanding of past climate and ecology, critical differences in the properties of live-tree and historic-timber data might affect results and interpretations of large-scale studies, such as those relying on large datasets from public databases like the International Tree-Ring Data Bank (ITRDB). The objective of this work was to compare summary measures of live-tree versus historic-timber datasets likely to affect outcomes and inferences of typical paleoenvironmental applications. We used 99 live-tree (LT) and 41 historic-timber (HT) datasets collected in the Appalachian region of the eastern United States and compared common analytical measures for understanding past climate and ecology, including temporal coverage, species composition, recruitment patterns, segment length, series coherence/mean interseries correlation (as Rbar), expressed population signal (EPS), subsample signal strength (SSS) and response to drought and extreme climate events. We found that tree-ring data from historic timbers record some ecological events similarly to live trees and are sensitive to some climate conditions, with important caveats related to the influence of site and tree selection on analytical measures. In some cases, these caveats can be overcome through improved collection of metadata and additional analyses. In all cases, potential differences in LT and HT data should be considered by those who perform large-scale analyses using public tree ring databases, especially as more scientists contribute historic-timber datasets.
Over recent decades, the southeastern United States (Southeast) has become increasingly well represented by the terrestrial climate proxy record. However, while the paleo proxy records capture the region's hydroclimatic history over the last several centuries, the understanding of near surface air temperature variability is confined to the comparatively shorter observational period (1895‐present). Here, we detail the application of blue intensity (BI) methods on a network of tree‐ring collections and examine their utility for producing robust paleotemperature estimates. Results indicate that maximum latewood BI (LWBI) chronologies exhibit positive and temporally stable correlations (r = 0.28–0.54, p < 0.01) with summer maximum temperatures. As such, we use a network of LWBI chronologies to reconstruct August‐September average maximum temperatures for the Southeast spanning the period 1760–2010 CE. Our work demonstrates the utility of applying novel dendrochronological techniques to improve the understanding of the multi‐centennial temperature history of the Southeast.
Tree-ring widths (TRW) of historical and archeological wood provide crucial proxies, frequently used for high-resolution multi-millennial paleoclimate reconstructions. Former growing conditions of the utilized trees, however, are largely unknown. Potential influences of historical forest management practices on climatic information, derived from TRW variability need to be considered but have not been assessed so far. Here, we examined the suitability of TRW series from traditionally managed oak forests (Quercus spp.) for climate reconstructions. We compared the climate signal in TRW chronologies of trees originating from high forests and coppice-with-standards (CWS) forests, a silvicultural management practice widely used in Europe for most of the common era. We expected a less distinct climate control in CWS due to management-induced growth patterns, yet an improved climate-growth relationship with TRW data from conventionally managed high forests. CWS tree rings showed considerably weaker correlations with hydroclimatic variables than non-CWS trees. The greatest potential for hydroclimate reconstructions was found for a large dataset containing both CWS and non-CWS trees, randomly collected from lumber yards, resembling the randomness in sources of historical material. Our results imply that growth patterns induced by management interventions can dampen climate signals in TRW chronologies. However, their impact can be minimized in well replicated, randomly sampled regional chronologies.
Dendroarchaeology is under-represented in the Gulf Coastal Plain region of the United States (US), and at present, only three published studies have precision dated a collection of 18th–19th-century structures. In this study, we examined the tree-ring data from pine, poplar, and oak timbers used in the Walker House in Tupelo, Mississippi. The Walker House was constructed ca. the mid-1800s with timbers that appeared to be recycled from previous structures. In total, we examined 30 samples (16 pines, 8 oaks, and 6 poplars) from the attic and crawlspace. We cross-dated latewood ring growth from the attic pine samples to the period 1541–1734 (r = 0.52, t = 8.43, p < 0.0001) using a 514-year longleaf pine (Pinus palustris Mill.) latewood reference chronology from southern Mississippi. The crawlspace oak samples produced a 57-year chronology that we dated against a white oak (Quercus alba L.) reference chronology from northeast Alabama to the period 1765–1822 (r = 0.36, t = 2.83, p < 0.01). We were unable to cross-date the six poplar samples due to a lack of poplar reference chronologies in the region. Our findings have two important implications: (1) the pine material dated to 1734 represents the oldest dendroarchaeology-confirmed dating match for construction materials in the southeastern US, and (2) cross-dating latewood growth for southeastern US pine species produced statistically significant results, whereas total ring width failed to produce significant dating results.
To satisfy the increasing demand for wood in central Europe during medieval times, a new system of forest management was developed, one far superior to simple coppicing. The adoption of a sophisticated, Coppice-with-Standards (CWS) management practice created a two-storey forest structure that could provide fuelwood as well as construction timber. Here we present a dendrochronological study of actively managed CWS forests in northern Bavaria to detect the radial growth response to cyclical understorey harvesting in overstorey oaks (Quercus sp.), so-called standards. All modern standards exhibit rapid growth releases every circa 30 years, most likely caused by regular understorey management. We further analyse tree-ring width patterns in 2120 oak timbers from historical buildings and archaeological excavations in southern Germany and north-eastern France, dating between 300 and 2015 CE, and succeeded in identifying CWS growth patterns throughout the medieval period. Several potential CWS standards even date to the first millennium CE, suggesting CWS management has been in practice long before its first mention in historical documents. Our dendrochronological approach should be expanded routinely to indentify the signature of past forest management practices in archaeological and historical oak wood.
Summer temperatures across eastern North America (hereafter East) will soon reach a level consistently above any observation experienced during the instrumental period. Increasing temperatures will have negative impacts on natural (e.g., water, plant and animal communities) and human (e.g., health, infrastructure, economies) systems upon which the large and growing centres of human population across the region depend. Within the network of Northern Hemisphere tree‐ring temperature proxy records, one of the most obvious geographic holes is the East, where few temperature‐sensitive proxies exist. Here we present the first steps towards building a network of temperature‐sensitive proxy records across the East using blue light intensity (BI) methods applied to the tree rings of multiple temperature sensitive tree species situated from North Carolina to Maine, USA. Our overall objective is to report on the most viable species for BI analysis across different regions of the East (e.g., Southeast US, Midwest US, Northeast US/Canadian Maritimes) by exploring temporal (e.g., since ca. 1900) and spatial relationships between instrumental temperatures and BI metrics. We found BI to be a strong predictor of March–October mean air temperature (R² = 0.61) across the Northeast US/eastern Canada, and Sep‐Oct maximum air temperature (R² = 0.42) across the Southeast US. Of all species tested, Tsuga canadensis and Picea rubens contained the strongest BI temperature signal. Adding more BI sites from these and potentially other species, as well as inclusion of other temperature proxies (e.g., ring widths) will allow for the development of a skilful broad‐scale and long‐term temperature field reconstruction across the East.
The “two-third spline” (2/3S) is a frequently applied method to detrend tree-ring series. It fits a spline with a 50% frequency cutoff at a frequency equal to two-thirds of each sample length in a dataset. It was introduced to ensure a minimum loss of low-frequency variance, which is resolvable during the detrending of ring-width series.
In this paper I show potential problems that arise when rusing this method. The 2/3S runs counter the strengths of using a digital filter to detrend – i.e. one is giving up full control over the frequency-removing characteristics of the growth curve and each individual time series retains a different amount of low frequency. Thus, the 2/3S is less suitable for reconstructing climate or to compare environmental impacts on tree growth between groups – both of which comprise the majority of dendrochronological analyses – as it will likely introduce a temporal frequency bias. Within a long chronology it will result in decreasing power to resolve low frequencies towards present in a living-only trees setting, especially when the youngest segment lengths are 100 years and shorter, and more generally during the period where the chronology is constructed from samples with shorter segment lengths compared to the period with longer segment lengths. The frequency bias will also significantly impact regression slopes and correlation coefficients, possibly distorting analyses investigating multiple groups with different mean segment lengths. Highlighting these potential biases, I recommend the community to not use this method on an individual basis but rather to use a fixed spline stiffness for all samples based on the n% criterion (n = 67) of e.g. the mean segment length of the entire dataset.
Regional differences in tree growth can be used to approximate the geographical provenance of ring-width series (‘dendro-provenancing’). This method relies on cross-dated ring-width series (reference chronologies) that are thought to represent the radial growth signal of trees in a given region. Reference chronologies are often established from ring-width series of living tree populations. Frequently, they are too short to allow for investigating the provenance of historical wood. Thus, references are extended by ring-width series from buildings and art-historical objects that exhibit best matching growth patterns with the living tree references. Yet, series from other provenances may erroneously be included. Thereby the local or regional growth signal of the references is progressively contaminated, but this has received little attention to date. I investigate this contamination risk using a simulation approach that allows for generating pseudo site chronologies that preserve the relevant statistical properties of the real site chronologies. While the exact provenance of historical wood is unknown, for simulated ring-width series the provenance is unambiguous. Hence, pseudo reference chronologies may be established while monitoring the signal mixture. Specifically, 15 site chronologies of Norway spruce (Picea abies (L.) H. Karst.) from northeastern Switzerland were used to generate 15 pseudo site growth signals that span 1000 years. The simulation demonstrates that quasi uncontaminated references can be established in ideal circumstances for the study area. However, the thresholds for the similarity in between-series correlation must be very high. Even then, contaminated pseudo references occurred in rare cases during the simulation. Yet, elevation-specific pseudo references were established with lower thresholds. Simulation currently offers the only approach for assessing the contamination risk of reference chronologies, and it allows for elucidating the conditions under which acceptable levels of contamination can be guaranteed. Therefore, the present approach paves the way towards a practical simulation tool for dendro-provenancing.
The application of tree-ring research to the study of cultural heritage has seen important conceptual and methodological developments in the 21st century. Following the breakthrough discovery in the 1980s of the importation of timber from the south-eastern Baltic to the Low Countries for panel paintings, the historical timber trade acquired paramount relevance in European dendrochronology. The improvement of methods and tools to locate the area of origin of the wood has since become a focal line of research. Reference chronologies of different variables (ring width, earlywood, latewood, earlywood vessel size in oak, latewood density in conifers, stable isotope chronologies of δ13C, δ18O) are now being developed in areas formerly (and currently) exploited for timber production, and isotopic signatures of 87Sr/86Sr are being mapped to provide a geochemical reference. In parallel, novel techniques to identify wood species (automated wood identification, chemical biomarkers, DNA barcoding) and their application on historical and ancient wood are being explored, given that this could sometimes help narrow down the timber source area. Modern technology is playing a key role in the study of wooden objects through non-invasive methods, and collaboration with (art) historians, mathematicians, engineers and conservators has proven essential in current achievements. Tree-ring series can now be retrieved from high resolution X-ray computed tomography images, allowing the research of otherwise inaccessible pieces. This paper reviews recent advances in those fields (tree-ring based dendroprovenancing, wood species identification, chemical fingerprinting, use of genetic markers, isotopic signatures, and non-invasive methods), and discusses their implementation and challenges in dendroarchaeological studies.
From its inception as a scientific discipline, tree-ring research has been used as a trans-disciplinary tool for dating and environmental reconstruction. Tree-ring chronologies in some regions extend back many thousands of years, opening up new potential for the study of climate, people, and ecology at annual and sub-annual resolution. As such, they are a frequently used resource for a diverse range of studies spanning the Holocene. They are also the focus of a constantly evolving array of analytical techniques and multidisciplinary approaches to research questions. This literature review discusses case studies at the cutting-edge of interdisciplinary tree-ring research, notes recent breakthroughs and limitations, and identifies key frontiers for the future of tree-ring research.
Cool and warm season precipitation totals have been reconstructed on a gridded basis for North America using 439 tree-ring chronologies correlated with December-April totals and 547 different chronologies correlated with May-July totals. These discrete seasonal chronologies are not significantly correlated with the alternate season and the December-April reconstructions are skillful over most of the southern and western United States and northcentral Mexico, and the May-July estimates have skill over most of the United States, southwest Canada, and northeast Mexico. The strong continent wide El Niño/Southern Oscillation (ENSO) signal embedded in the cool season reconstructions, and the Arctic Oscillation signal registered by the warm season estimates, both faithfully reproduce the sign, intensity, and spatial patterns of these ocean-atmospheric influences on North American precipitation as recorded with instrumental data. The reconstructions are included in the North American Seasonal Precipitation Atlas (NASPA) and provide insight into decadal droughts and pluvials. They indicate that the 16 th century megadrought, the most severe and sustained North American drought of the past 500-years, was the combined result of three distinct seasonal droughts each bearing unique spatial patterns potentially associated with seasonal forcing from ENSO, the Arctic Oscillation, and the Atlantic Multidecadal Oscillation. Significant 200- to 500-year long trends toward increased precipitation have been detected in the cool and warm season reconstructions for eastern North America. These seasonal precipitation changes appear to be part of the positive moisture trend measured in other paleoclimate proxies for the East that began due to natural forcing before the industrial revolution and may have recently been enhanced by anthropogenic climate change.
Aim
To test the previously published hypothesis that there was widespread reforestation following the depopulation of Indigenous Peoples in the 16th and 17th centuries.
Location
The central Appalachian Mountains of eastern North America.
Taxon
Quercus alba, Liriondendron tulipifera
Methods
To test for reforestation following depopulation, we used tree‐ring evidence of tree recruitment, early radial growth and growth releases from 18 historic log buildings (n = 361 logs) and eight old‐growth forest sites (n = 197 trees). We used inner‐ring dates to determine if a synchronous recruitment event(s) was present at historic sites but absent from old‐growth sites following depopulation. We used cluster analysis to determine if historic logs established in a clearing (fast early growth) or under a canopy (slow early growth). Similarly, we calculated disturbance rates (growth releases per 100 years) to determine if historic logs grew in a clearing (low disturbance) or under a canopy (high disturbance).
Results
Historic log and old‐growth forest sites both document a period of elevated recruitment beginning in the 1670s. This event was observed in previous studies and across site types, suggesting that either climate variability or the absence of low‐intensity land use (e.g. fire) may have also contributed to forest establishment. Most historic sites (61%–83%) had fast early growth, indicating growth of trees in high‐light conditions. The rate of disturbance was lower at historic sites with fast early growth (5.3 events/century, 95% Cl [3.6, 7.0]) than at old‐growth sites with slow early growth (23.5 events/century, 95% Cl [17.5, 29.5]), consistent with the idea that most historic logs were harvested from fast‐growing, second‐growth forests that established after depopulation.
Main Conclusions
Our results support the hypothesis of reforestation in upland forests of the central Appalachian Mountains following depopulation and suggest that upland forests, at the time of European immigration, were at least in part, a legacy of indigenous land use practices. However, the timing of a regional drought event, depopulation and subsequent recruitment of trees, all within the period of ~1650–1690 CE, warrants further research into interactions between indigenous land use and climate during a pivotal period in North American history.
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Our knowledge of climate variability in the densely populated Northeastern United States is limited to instrumental data of the last century. Most regional paleoclimate proxies reflect a mix of climate responses, which makes reconstructing historical climate a challenge. Here we analyze tree-ring chronologies from Atlantic white cedar (Chamaecyparis thyoides) as a potential regional paleotemperature proxy. We evaluate our tree-ring network for spatiotemporal climate signal strength and reconstruction skill across New England. Atlantic white cedar sites in the northern section of the species' range exhibit positive significant annual growth relationships with local and regional temperatures. Chronologies constructed from northern sites yield skillful reconstructions of temperature that reproduce centennial, multidecadal, and interannual variability in the instrumental record, providing a novel paleotemperature record for New England.
Dendroarchaeological samples archived in historical wooden artifacts can be used to reconstruct forest conditions during European settlement of North America. In this study, we dated and examined tree-ring records of white oak (Quercus alba L.) logs sampled from a kitchen and slave quarters from a historical plantation in western Virginia. The kitchen was constructed from logs harvested after the 1845 growing season. The slave quarters was constructed from logs harvested after the 1864 growing season. White oak establishment in the study area parallels a general pattern of forest expansion into clearings following the depopulation of Native Americans from the eastern United States between 1720 and 1789. Synchronized canopy openings in the 1770s and 1780s could be due to increased tree cutting by European settlers to erect wooded palisades for protection against Native Americans.
For the period of the Neolithic lake-shore occupation on Lake Constance (similar to 4000-2400 bc), settlement and woodland developments are investigated in parallel using dendrotypology, a dendroarchaeological approach based on the classification of oak timber according to tree age, growth patterns, and degree of stem conversion. Along with characteristics related to architectural adaptations and settlement relocations, dendro-groups allow an insight into the structure and dynamics of the exploited forest stands. From clearing activities through intermediate coppice practices to forest degradation, dendrotypological models show a strong relationship between demographic developments and woodland use in a region largely covered by forest at that time. It appears that against a background of climate evolution, regional patterns of settlement development can be directly linked at a higher resolution of time to the management of woodland as well as to the intensity of land use. Regarding the varying ecological susceptibility of a mosaic-like landscape around Lake Constance, the consideration of the ecological components enhanced by dendrotypology allows a better balance in the interpretation of the interaction between climate impact and settlement behavior. Consequently, dendrotypology has to be seen as a reliable interface between humanology and natural sciences in wetland archaeology, and from this perspective, further prospects of this approach are presented.
Significance
A 1,112-y tree-ring record of moisture shows that in opposition to conventional wisdom, the climate during the rise of the 13 th -century Mongol Empire was a period of persistent moisture, unprecedented in the last 1,000 y. This 15-y episode of persistent moisture likely led to a period of high grassland productivity, contributing fuel to the Mongol Empire. We also present evidence that anthropogenic warming exacerbated the 21st-century drought in central Mongolia. These results indicate that ecosystems and societies in semiarid regions can be significantly affected by unusual climatic events at the decadal time scale.
In a number of areas of applied climatology, time series are either averaged to enhance a common underlying signal or combined to produce area averages. How well, then, does the average of a finite number (N) of time series represent the population average, and how well will a subset of series represent the N-series average. We have answered these questions by deriving formulas for 1) the correlation coefficient between the average of N time series and the average of n such series (where n is an arbitrary subset of N) and 2) the correlation between the N-series average and the population. We refer to these mean correlations as the subsammple signal strength (SSS) and the expressed population signal (EPS). They may be expressed in terms of the mean interseries correlation coefficient r-barm as SSS = (R-bar/sub n/,N)/sup 2/roughly-equaln(1+(N-1)r-bar)/N(1+(n+1)r-bar), EPS = (R-bar/sub N/)/sup 2/roughly-equalNr-bar/1+(N-1)r-bar. Similar formulas are given relating these mean correlations to the fractional common variance which arises as a parameter in analysis of variance. These results are applied to determine the increased uncertainty in a tree-ring chronology which results when the number of cores used to produce the chronology is reduced. Such uncertainty will accrue to any climate reconstruction equation that is calibrated using the most recent part of the chronology. The method presented can be used to define the useful length of tree-ring chronologies for climate reconstruction work.
Dendrochronology studies in Atlantic Canada are rare partly because old-growth forests are scarce making it difficult to establish multiple-century tree-ring chronologies. One approach to overcome this problem is to use tree-ring records found in the wood of historical structures. For our study, the Sinclair Inn in Annapolis Royal, Nova Scotia, was selected for a dendroarchaeological assessment because of its rich and complex history: it resulted from the merging of two early 18th Century houses (the Soullard and Skene houses). To date the Sinclair Inn, three other historical structures of a younger age were used to establish an annual ring record in lieu of old-growth forest data. Red spruce (Picea rubens), a dominant tree species in the Maritimes, was the most prominent wood found in the structures and allowed for the creation of a regional red spruce reference chronology extending far enough into the past to cover the supposed period of construction of the Sinclair Inn. Crossdating results indicate cutting dates of 1709 and 1710 for the Skene and Soullard houses, respectively, and 1769 for the inn itself. In the process of dating the structure, a ,200-year long regional floating red spruce chronology (1591-1789) was developed that will further help future dendrochronological investigations in the Maritimes.
On the basis of different methods, researchers have reached different and sometimes contradicting conclusions on the question, when regular woodland management started in Europe. While some reconstruct systematic woodland management already in the Neolithic, others found it altogether improbable that woodland management should have been invented in prehistoric times. This study critically reviews the applied methods and their respective data. The aim is not only to learn about their respective strengths and weaknesses and certainly not to decide on the winner. Rather, we try to reflect on basic assumptions and whether these are the reason for seeming contradictions.
Stable oxygen isotope dendrochronology is an effective precision-dating method for fast grown, invariant (complacent) tree-rings and for trees growing in moist, temperate climatic regions where growth may not be strongly controlled by climate. The method works because trees preserve a strong common isotopic signal, from summer precipitation, and therefore do not need to be physiologically stressed to record a dating signal. This study explores the working hypothesis that whilst tree species may differ in their eco-physiology, leaf morphology and wood anatomy they will record an isotopic signal in their growth rings that is sufficiently similar to enable their precise dating against isotopic reference chronologies developed using dated oak tree rings from the same region. Modern and historic samples from six species (sweet chestnut, English elm, ash, alder, European beech and black poplar) were analysed and their oxygen isotopic variability was compared against an oak master chronology previously developed for central southern England. Whilst differences in the relative strength of the agreement between the different species and the master chronology are apparent, the potential for interspecies dating is demonstrated convincingly. The ability to date non-oak species using stable oxygen isotopes opens-up new opportunities for science-based archaeology and will improve understanding of a largely-unexplored, but significant part of the European historic buildings archive.
Loblolly pine (Pinus taeda L.), shortleaf pine (Pinus echinata Mill.), and eastern white pine (Pinus strobus L.) seedlings were multi-cropped with standard and large-diameter white oak (Quercus alba L.) seedlings to test for neutral or positive effects of multi-cropping. The study was established in 2014 in three complete blocks within recent clearcuts in eastern Tennessee, USA. Each block consisted of six multi-cropped treatments and four monocultures randomly assigned to ten 14.63 × 21.95 m plots. Within each block, monocultures of white oak and each pine species were planted in four control plots. Multi-cropped treatments included loblolly pine planted with white oak at a 0.31 m spacing, loblolly pine planted with white oak in alternating rows at a 1.74 m spacing, shortleaf pine planted with white oak at a 0.31 m spacing, shortleaf pine planted with white oak at a 1.74 m spacing, eastern white pine planted with white oak at a 0.31 m spacing, and eastern white pine planted with white oak at a 1.74 m spacing. Each plot with white oak received 20 standard (~0.127 cm in basal diameter) and 20 large-diameter (~0.632 cm in basal diameter) white oak seedlings that were randomly assigned to planting locations. Initial height, basal diameter, and early survival were recorded for each seedling just after planting. Height growth, basal diameter growth, survival, herbivory, and insect damage were recorded in early December 2014, 2015, 2016, 2017, 2018, and 2019. In 2019, percent survival among treatments did not differ significantly for white oak (p = 0.152), loblolly pine (p = 0.396), shortleaf pine (p = 0.246), or eastern white pine (p = 0.065). In addition, mean height growth and mean basal diameter growth did not differ significantly among treatments for white oak (p = 0.698 and 0.437, respectively), loblolly pine (p = 0.630 and 0.762, respectively), shortleaf pine (p = 0.324 and 0.251, respectively), or eastern white pine (p = 0.623 and 0.823, respectively). Survival was greater for large-diameter white oak seedlings than standard seedlings (p < 0.001). Mean height and mean basal diameter growth in large-diameter white oak seedlings were significantly greater than in standard seedlings ((p < 0.001) and (p < 0.001), respectively). Although these plantings are in the early stages of development, the lack of significant differences in seedling performance among treatments suggests species compatibility and no net negative impact of multi-cropping white oak with the three pine species.
The Boyhood Home at Knob Creek is part of the Abraham Lincoln Birthplace National Historical Park in Hodgenville, Kentucky. Here, a replica cabin constructed in the 1930s by Chester and Hattie Howard is meant to represent the home where President Abraham Lincoln formed his earliest memories. According to oral histories, this replica, the Knob Creek Cabin, was constructed using timbers salvaged from a cabin found elsewhere on the Knob Creek Farm, believed to have been the home of Lincoln's childhood friend, Austin Gollaher. Therefore, the cabin is believed to be contemporary with Lincoln's childhood at Knob Creek (early 1800s), and represents what the original Lincoln family cabin may have looked like, despite the disappearance of the original Lincoln cabin during the late 1800s. To determine whether the Knob Creek Cabin truly dates to Lincoln's childhood, we extracted core samples from logs in the cabin and compared the tree-ring patterns to an absolutely-dated reference chronology from Mammoth Cave, Kentucky. We dated the oak chronology from the Knob Creek Cabin to the period 1712–1861 (r = 0.57, n = 150 years, t = 8.44, p < 0.0001). Several of the logs indicate cutting dates occurred during two different periods, 1847–1848 and 1861–1863, neither of which coincide with Lincoln's childhood at Knob Creek Farm. Based on these findings, we conclude that the Knob Creek Cabin could not have been originally constructed by the Gollaher family during Abraham Lincoln's childhood on the Knob Creek Farm. Instead, the Knob Creek Cabin likely was built using timbers that were salvaged from two different structures, one that was constructed during the period 1847–1848 and another that was constructed during the period 1861–1863. The origins of these logs are unknown.
Annual surface air temperatures across the eastern United States (US) have increased by more than 1 °C within the last century, with the recent decades marked by an unprecedented warming trend. Tree-rings have long been used as a proxy for climate reconstruction, but few truly temperature-sensitive trees have been documented for the eastern US, much less the Appalachian Mountains in the Southeast. Here, we measure blue intensity (BI) and ring width (RWI) in red spruce growing at the southernmost latitudinal range margin of the species on the North Carolina-Tennessee border to test the efficacy of using either metric as a temperature proxy in the eastern US. The BI and RWI chronologies spanned 1883–2008 and had an interseries correlations of 0.42 and 0.54, respectively, but time series were trimmed to the period 1950–2008 due to low sample depth. We discovered strong, positive, and stable correlations between both current-year early fall (September–October) T max (r = 0.62; p < 0.001) and T mean (r = 0.51; p < 0.001) and ΔBI during the period 1950–2008, but found no significant relationships between temperature and RWI. We show BI metrics measured in red spruce to be a promising temperature proxy for the southern Appalachian Mountain region. Future research should focus on testing [1] the efficacy of using BI on red spruce collected from across the species range, and [2] the potential for using BI as a temperature proxy in other conifers distributed in the eastern US.
The La Pointe-Krebs House in Pascagoula, Mississippi is an important archaeological site (22JA526) located in the southeast United States (US). Despite being subjected to several independent archaeological and architectural studies, the exact calendar year(s) of construction for the original building and subsequent additions was unknown. We identified and sampled 26 timbers throughout the structure that contained bark or a smooth, curved outer surface that would return near-cutting or cutting dates using techniques of dendroarchaeology. A total of 14 samples came from timbers associated with the original 2-room Center Room, 9 from the East Room addition, and 3 from the West Room addition. All sampled timbers derived from a southern yellow pine tree species, most likely Pinus palustris (Mill.; longleaf pine) which was once widely distributed across the southeast US. The structure chronology spanned the period 1572-1932 CE with an inter-series correlation of r = 0.49 (1595-1788; p < 0.001) and was correlated against a regional P. palustris reference chronology from Eglin Air Force Base, Florida (n = 194 years, r = 0.40; t = 6.03, p < 0.001). Compilation of the cutting-and near-cutting dates revealed three distinct dating groups of timbers. First, three timbers from the Center Room have cut dates of 1757 CE. Second, two timbers in the East Room had cutting dates of 1762 CE. Third, three timbers with bark located over the Center and East Rooms dated to 1772 CE and were most likely repairs made to the roof following Bernard Roman's Hurricane in September 1772. No samples collected from the West Room provided near-cutting or cutting dates. The Gulf Coast region of the US has strong ties to French culture, heritage, and history, and the La Pointe-Krebs House played an important role during the creation of that culture in the region that still exists today.
The Black Death (1349–1350 in Norway) is often cited as the cause of a severe population decline and building hiatus in the middle of the 14th century. This paper analyses this hypothesis by matching the Black Death with human and environmental impacts on tree-ring growth. The number of buildings dated by dendrochronology in Norway shows a dramatic decline several decades before the plague. In Norway, the building hiatus, which has parallels in several other places in Europe, dates from the late-13th century almost to the 16th century. The first dated houses built after the plague date from the 15th century and many of the logs have exceptionally wide tree rings compared to timber from other periods. Assuming the rapid growth was because of an open landscape, the trees are likely to have grown on infields of farms abandoned due to the 14th century population decline. Since many of these fast-growing trees germinated in the early-14th century and the number of dated buildings drops dramatically several decades before the plague, the Black Death can hardly be the only reason for the population decline in Norway and one plausible explanation is that some environmental impact occurred decades earlier. The dendroclimatological evidence of cold and wet summers in the years before the plague is suggestive, but historical sources also pinpoint famine due to crop failure. They also tell of farms being abandoned several decades before the plague and mention periods of heavy rainfall and famine in the early-14th century.
The unique position of dendrochronology at the nexus of archeology, ecology, and climatology allows it to play a pivotal role in the study of past human-environment interactions. Yet, few tree-ring studies in Europe and eastern North America have been used to study pre-industrial land-use changes, forest ecology, and carbon dynamics and thus to constrain the uncertainties surrounding the Early Anthropocene hypothesis (Ruddiman Clim Chang 61:261–293, 2003; Rev Geophys 45(4):RG4001, 2007). Here, we discuss the potential of dendro-archeo-ecology—the use of dendroarcheological material in the study of forest ecology—to document past human land-use and forest alteration, which started in the Neolithic Era (∼12,000–4000 BP) in Europe and after European immigration into eastern North America in the 1620s. In this context, we focus on the dendro-archeo-ecology of (1) Neolithic pile dwellings in the Euro-Mediterranean region and (2) old-growth forest dynamics in eastern North America. We discuss recurring challenges (e.g., low sample depth, short series length) and uncertainties (e.g., species and tree size bias) related to the use of (pre)historic timbers for ecological purposes that need to be carefully addressed. We advocate for a concerted effort to move the use of dendro-archeological material from strictly archeological applications towards exploration of its ecological potential and for a close alliance of dendrochronology with related disciplines that aim to address the same subjects.
During May 2013, the Bear Paw State Natural Area near Boone, North Carolina acquired an 11.5 ha tract of land and two log cabins from David Wray of Blowing Rock, North Carolina. Work was soon underway to determine the historical nature of these two buildings and to evaluate them for consideration for the National Register of Historic Places. A historic structure report, completed as a collaboration between Appalachian State University and the North Carolina Division of Parks and Recreation, was unable to discover much about the history of the two log cabins except that they were both likely moved to their current location in the early 20th Century. To determine when the cabins were built, we extracted core samples from logs in both cabins and compared the tree-ring patterns to region-wide, precisely-dated reference chronologies. We dated the tulip poplar tree-ring chronology from the Big Cabin to the period 1675-1859. Cutting dates on several of the logs revealed tree harvest likely occurred between fall 1859 and spring 1860. Some logs had outermost rings that dated to 1857 and 1858. Still, these logs may have been harvested a few years earlier, or some of the outer rings may have been lost during construction or sampling. We were unable to absolutely date an 81-year long American chestnut chronology from the Small Cabin. Our results confirmed that the Big Cabin was an Antebellum Period structure (pre-American Civil War) and therefore has potential historical significance. Because we still cannot tie this cabin to a historical figure or a historical event, the cabin cannot be nominated yet for inclusion in the National Register of Historic Places, but the identification of an original construction date for the cabin may contribute to further assessment for inclusion on a local or national register. In the meantime, we intend to use this cabin in annual summer workshops for undergraduate students taking courses at Appalachian State University so that more students can be exposed to the hands-on nature of scientific inquiry and can learn the value of dendrochronology for understanding human and environmental history.
Forests of eastern North America have undergone abrupt transformations over the last several centuries due to changing land use and climate. Researchers look to pre-settlement forests as a guide for forest restoration, though much of our understanding of composition and dynamics in pre-settlement forests is based on spatially restricted sediment records, few and fragmented old-growth stands in a narrow range of site types, and potentially biased historical documentation. Logs from historic structures hold information that may be useful to forest ecology in eastern North America, but before these records can be used, we must first establish where the logs originated, why they were selected over other trees, and what they can and cannot tell us about past forest ecology. Using a case study approach, I collected data from fifteen log structures in the central Appalachian region to compare construction site locations, species used, and mean diameter of logs through time to determine the ecological biases associated with human behavior in log structure construction. Construction site locations changed from valleys to mountains through time and the species used in construction shifted from Quercus alba to a mix of Quercus alba, Liriodendron tulipifera, Pinus strobus, and Castanea dentata over time. The diameter of logs used in construction were generally consistent through time, with an average basal diameter of 31.3 cm (±4.7). Mean age of logs increased through time for Quercus species, regardless of log diameter. These results suggest the species used for structural logs were selected by their abundance at the location of construction but that as construction site locations and resource availability changed through time, the species used in construction changed as well. While there are biases and limitations of dendroecological data from historic structures, the results presented here demonstrate that structural log data provide greater replication during the early European immigration period, representation of upland (valley) forest sites, and establishment of chronologies for species that are not well represented in current tree-ring chronologies (e.g. Castanea dentata, Liriodendron tulipifera). These results suggest structural logs can benefit ecological research by filling the temporal, spatial, and species void of tree-ring chronologies not only for the central Appalachian region, but also for other areas in eastern North America.
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.
Dendroarchaeology has been an invaluable resource in aiding management agencies with data that can authenticate or contest traditional dates of construction for historic log structures. Tipton-Haynes is a well-documented state historic site in East Tennessee with two log structures thought to be constructed by its original occupant, Colonel John Tipton, in the late eighteenth century. To examine the landscape history of the site, these structures were dated using dendrochronology to contextualize the built environment over time. Structures include a renovated log cabin that stands as the core of a Greek-Revival farmhouse and a double-pen log corn crib. Results of the analysis show that the Tipton farmhouse was constructed in 1799 to serve as a retirement residence with renovations occurring shortly after 1821 by John Tipton, Jr., while the corn crib was constructed by Landon Haynes in 1851 during an expansion of farm production on the site. Our study contextualized the provenience of these structures over time which allowed us to recognize why these changes took place on the landscape and under whose ownership these changes occurred. Such dendroarchaeological studies provide a deeper understanding of the history of construction of historic sites in Tennessee and the Southeastern U.S. in general, helping historians, historical architects, and historical agencies more accurately interpret and understand the value of our historic resources.
The Rocky Mount site has important historical and cultural significance for the State of Tennessee because it was built by one of its earliest settlers and served as the capital of the territory from 1790 to 1792. Questions arose concerning whether the two main log structures - known as the Cobb House with adjoining dining room - were built by William Cobb between 1770 and 1772. The authors used tree-ring dating to determine the year(s) of construction of these two log structures. Three nearby reference tree-ring chronologies anchored the Rocky Mount tree-ring chronology from 1667 to 1829. Cutting dates obtained from 19 logs revealed that the Cobb House was built beginning in 1827 and finished by 1828, while the dining room was begun in 1829 and finished by 1830. An additional six logs had outermost dates between 1820 and 1825. These 25 logs demonstrate, instead, that Michael Massengill constructed the house and dining room between 1827 and 1830.
In humid, broadleaf-dominated forests where gap dynamics and partial canopy mortality appears to dominate the disturbance regime at local scales, paleoecological evidence shows alteration at regional-scales associated with climatic change. Yet, little evidence of these broad-scale events exists in extant forests. To evaluate the potential for the occurrence of large-scale disturbance, we used 76 tree-ring collections spanning ∼840 000 km2 and 5327 tree recruitment dates spanning ∼1.4 million km2 across the humid eastern United States. Rotated principal component analysis indicated a common growth pattern of a simultaneous reduction in competition in 22 populations across 61000 km2. Growth-release analysis of these populations reveals an intense and coherent canopy disturbance from 1775 to 1780, peaking in 1776. The resulting time series of canopy disturbance is so poorly described by a Gaussian distribution that it can be described as "heavy tailed," with most of the years from 1775 to 1780 comprising the heavy-tail portion of the distribution. Historical documents provide no evidence that hurricanes or ice storms triggered the 1775-1780 event. Instead, we identify a significant relationship between prior drought and years with elevated rates of disturbance with an intense drought occurring from 1772 to 1775. We further find that years with high rates of canopy disturbance have a propensity to create larger canopy gaps indicating repeated opportunities for rapid change in species composition beyond the landscape scale. Evidence of elevated, regional-scale disturbance reveals how rare events can potentially alter system trajectory: a substantial portion of old-growth forests examined here originated or were substantially altered more than two centuries ago following events lasting just a few years. Our recruitment data, comprised of at least 21 species and several shade-intolerant species, document a pulse of tree recruitment at the subcontinental scale during the late-1600s suggesting that this event was severe enough to open large canopy gaps. These disturbances and their climatic drivers support the hypothesis that punctuated, episodic, climatic events impart a legacy in broadleaf-dominated forests centuries after their occurrence. Given projections of future drought, these results also reveal the potential for abrupt, meso- to large-scale forest change in broadleaf-dominated forests over future decades.
The Harding Cabin is a one and one half story, double pen log cabin located on the Belle Meade Plantation in Davidson County, Tennessee, USA. Historical accounts attribute the eastern cabin to Daniel Dunham who originally settled in the area ca. 1780 and the western cabin to John Harding who purchased the land from the Dunham family in February 1807. We used dendrochronological dating techniques to determine the years of harvest for trees cut and used to build both cabins. We found that both cabins were predominantly made from two genera not commonly used to build log cabins in the southeastern U.S., Fraxinus (ash) and Ulmus (elm). We obtained ring width measurements from 30 cores from all walls on both cabins and used graphical and statistical techniques to crossdate the tree-ring series and create floating chronologies for both species. We crossdated these with reference chronologies from the ITRDB. The Fraxinus chronology was dated from 1657 to 1805 while the Ulmus chronology was dated from 1583 to 1805. Cutting dates indicated that most if not all trees used to build both cabins were cut in late winter/early spring of 1807 before the trees had broken dormancy. We propose that both cabins were built the same year but by different families. We propose that the Harding family built the eastern cabin while Harding’s slaves built the western cabin, originally at a different location on the property. Once the mansion was completed by 1820, the slave cabin was relocated beside the Harding cabin.
Four types of error are commonly associated with the basic problem of the time relationship that exists between the date of a tree-ring specimen and the archaeological manifestation being dated. These errors may sometimes be discovered and amended by using the clustering of dates and the clustering of archaeological traits. A secondary problem arises when lost exterior rings produce non-cutting dates in contrast to cutting dates. Tree-ring data may also be employed in deriving information of a non-chronological nature.
Tree rings of eastern red cedar (Juniperus virginiana L.) were examined from cores extracted from two log cabins located at the Wynnewood State Historic Site in Castalian Springs, Sumner County, Tennessee. One cabin was reportedly built by the first explorer in the area, Isaac Bledsoe, sometime between 1772 and his death in 1793. The second cabin was known as Spencer's Cabin after the first settler of the region, Thomas Sharp Spencer, who lived in the immediate vicinity from 1776 to 1779. The goal of this research was to determine the probable construction year(s) for both cabins and determine whether Bledsoe and Spencer did indeed build these structures. Forty-one cores were extracted from Bledsoe's Cabin, and 30 were used for crossdating and building a floating chronology using COFECHA. The Bledsoe's Cabin chronology was then statistically and graphically crossdated using the eastern red cedar reference tree-ring chronology (ITRDB #TN031) from Norris Dam, Tennessee. We found a statistically significant correlation (r = 0.42, t = 4.18, n = 85, p < 0.0001) between the Bledsoe's Cabin chronology and the reference chronology, anchoring the chronology between 1720 and 1804, with nearly all cores indicating tree harvesting between February and April 1805. Twenty-two cores were extracted from Spencer's Cabin, and 17 were used to build a floating chronology for the cabin. Again, we found a statistically significant correlation (r = 0.44, t = 4.85, n = 100, p < 0.00001) with the reference chronology which anchored the Spencer's Cabin chronology between 1726 and 1825. All trees appear to have been harvested between February and August in 1826. Therefore, neither structure was built by its historical namesake. No known historical documents suggest who the potential builders were, although the property was owned between ca. 1797 and 1826 by General James Winchester. He and his family, however, never resided on the Wynnewood property because Winchester had built a large multi-room structure in nearby Gallatin, Tennessee by 1802.
rings are an important proxy for understanding the timing and
environmental consequences of volcanic eruptions as they are precisely
dated at annual resolution and, particularly in tree line regions of the
world, sensitive to cold extremes that can result from climatically
significant volcanic episodes. Volcanic signals have been detected in
ring widths and by the presence of frost-damaged rings, yet are often
most clearly and quantitatively represented within maximum latewood
density series. Ring width and density reconstructions provide
quantitative information for inferring the variability and sensitivity
of the Earth's climate system on local to hemispheric scales. After a
century of dendrochronological science, there is no evidence, as
recently theorized, that volcanic or other adverse events cause such
severely cold conditions near latitudinal tree line that rings might be
missing in all trees at a given site in a volcanic year ("stand-wide"
missing rings), resulting in misdating of the chronology. Rather, there
is a clear indication of precise dating and development of rings in at
least some trees at any given site, even under adverse cold conditions,
based on both actual tree ring observations and modeling analyses. The
muted evidence for volcanic cooling in large-scale temperature
reconstructions based at least partly on ring widths reflects several
factors that are completely unrelated to any misdating. These include
biological persistence of such records, as well as varying spatial
patterns of response of the climate system to volcanic events, such that
regional cooling, particularly for ring widths rather than density, can
be masked in the large-scale reconstruction average.
Dendroprovenancing studies have been shown to have historically been initiated on the use of oak in art-historical contexts, but are now employed on a much wider range of species and artefact types, particularly in relation to ship remains. The commonest methodology is to compare individual site chronologies with a network of other chronologies, and to recognise trends in the geographical distribution of strong matches, suggesting the likely source area of the material. Other studies may look at the matching of individual timbers to draw similar conclusions. It is shown that ecological and genetic factors may strongly influence individual matching results and that ring-widths may therefore be considered a somewhat crude means of provenancing. Additional chemical and genetic markers are discussed, although these are unlikely to become routinely used in the near future.
Superposed epoch analyses, based on solar sector boundary crossings as key times and the Vorticity Area Index as the response variable, are tested for significance using both parametric and randomization techniques. We conclude from a comparison of these techniques that the randomization procedure leads to markedly different results from those obtained from parametric tests. In particular, the results are strongly affected by the modest skewness of the Vorticity Area Index distribution.-Authors
Intensified exploitation of natural populations and habitats has led to increased mortality rates and decreased abundances of many species. There is a growing concern that this might cause critical abundance thresholds of species to be crossed, with extinction cascades and state shifts in ecosystems as a consequence. When increased mortality rate and decreased abundance of a given species lead to extinction of other species, this species can be characterized as functionally extinct even though it still exists. Although such functional extinctions have been observed in some ecosystems, their frequency is largely unknown. Here we use a new modelling approach to explore the frequency and pattern of functional extinctions in ecological networks. Specifically, we analytically derive critical abundance thresholds of species by increasing their mortality rates until an extinction occurs in the network. Applying this approach on natural and theoretical food webs, we show that the species most likely to go extinct first is not the one whose mortality rate is increased but instead another species. Indeed, up to 80% of all first extinctions are of another species, suggesting that a species' ecological functionality is often lost before its own existence is threatened. Furthermore, we find that large-bodied species at the top of the food chains can only be exposed to small increases in mortality rate and small decreases in abundance before going functionally extinct compared to small-bodied species lower in the food chains. These results illustrate the potential importance of functional extinctions in ecological networks and lend strong support to arguments advocating a more community-oriented approach in conservation biology, with target levels for populations based on ecological functionality rather than on mere persistence.
I present and describe a new software package in the R statistical programming environment for dendrochronology. R is considered the world’s pre-eminent open-source statistical computing environment where users can contribute packages, which are freely available on the Internet. The dendrochronology program library in R (dplR) is able to read standard decadal-format files and allows users to perform several standard analyses including interactive detrending, chronology building, and the calculation of standard descriptive statistics. The package can also produce a variety of publication quality plots. The dplR package should make it easier for dendrochronologists to take advantage of R and use it as their primary analytic environment.
The problem of constructing millennia-long tree-ring chronologies from overlapping segments of cross-dated ring-width series is reviewed, with an emphasis on preserving very low-frequency signals potentially due to climate. In so doing, a fundamental statistical problem coined the 'segment length curse' is introduced. This 'curse' is related to the fact that the maximum wavelength of recoverable climatic information is ordinarily related to the lengths of the individual tree-ring series used to construct the millennia-long chronology. Simple experiments with sine waves are used to illustrate this fact. This is followed by more realistic experiments using a long bristlecone pine series that is randomly cut into a number of 1000-, 500- and 200-year segments and standardized using three very conservative methods. When compared against the original, uncut series, the resulting 'chronologies' show the effects of segment length even when the most conservative and noncommittal method of tree-ring standardiza tion is applied (i.e., a horizontal line through the mean). Alternative schemes of chronology development are described that seek to exorcise the segment length curse. While they show some promise, none is universal in its applicability and this problem still remains largely unsolved.
In dendroclimatology, tree-ring indices are traditionally calculated as part of the tree-ring chronology development process. This is accomplished by fitting a growth curve to the ring-width series and using it as a series of expectations for more or less well specified null conditions (uniform climate perhaps) of annual radial growth. The ratio of the actual ring widths to these expectations produces a set of dimensionless indices that can be averaged arithmetically with cross-dated indices from other trees into a mean chronology suitable for studies of climatic and environmental change. We show that tree-ring indices calculated in this manner can be systematically biased. The shape of this bias is defined by the reciprocal of the growth curve used to calculate the indices, and its magnitude depends on the proximity of the growth curve to the time axis and its intercept. The underlying cause, however, is lack of fit. To avoid this bias, residuals from the growth curve, rather than ratios, can be computed. If this is done, in conjunction with appropriate transformations to stabilize the variance, the resulting tree-ring chronology will not be biased in the way that ratios can be. This bias problem is demonstrated in an annual tree-ring chronology of bristlecone pine from Campito Mountain, which has been used previously in global change studies. We show that persistent growth increase since AD 1900 in that series is over-estimated by 23.6% on average when ratios are used instead of residuals, depending on how the ring widths are transformed. Such bias in ratios is not always serious, as it depends on the joint behaviour of the growth curve and data, particularly near the ends of the data interval. Consequently, ratios can still be used safely in many situations. However, to avoid the possibility of ratio bias problems, we recommend that variance-stabilized residuals be used.
Accurate (i.e., annual resolution) determination of total tree ages with increment core samples is difficult because of the improbability of intercepting the pith at the root collar for most trees. For the xeric conifer Austrocedrus chilensis (D. Don) Florin and Boutelje in northern Patagonia (Argentina), we developed and tested a three-stage procedure for improving estimates of total tree ages. i) For increment core samples not reaching the pith, a graphical technique is used to estimate the missing length of the tree radius. ii) Cumulative radial growth curves are used to estimate the numbers of rings in the missing lengths at variable heights above the root collar. And, iii) number of years required to reach coring height are derived from height-growth curves for seedlings growing under different site conditions. Approximately 500 seedlings (< 100 cm tall) were uprooted and sectioned for determination of height-growth curves and radial-growth curves at different stem heights. From these curves, total ages were estimated for trees sampled with increment borers. These procedures may reduce errors resulting from assumptions of circular ring symmetry or constant radial growth rate. However, where age determination requires estimation of the location of the missed pith, complete accuracy is not likely in all cases. For example, for slow-growing Austrocedrus trees, a missing core length of just 1 cm may result in errors of 10 to 20 years. Differences in rates of tree growth among stands of Austrocedrus indicate that the most accurate estimates of total tree ages require determination of seedling growth rates for each homogeneous site sampled for age structure. Best estimates must also take into account the differential growth rates of subpopulations of seedlings within each stand due to micro-site variation and competitive influences.
Deciduous Forests of Eastern North America, written by E. Lucy Braun and published in 1950, included a map depicting “original” (virgin) forest pattern. Her classification of forest regions remains an influential reference, though it was shaped by ecological assumptions that researchers consider outdated today. In this article, I present a new map of forest regions, using a data set from an extensive network of contemporary forest plots. Although there are differences between the two maps, including the homogenization of forests in the central section of the deciduous forest formation, the geography of Braun's forest regions is largely maintained. The similarities between the maps are noteworthy, considering the methodological differences in their creation and the intensive land use changes, fire suppression, introduction of exotic species, and changes in atmospheric chemistry that have occurred since Braun's work.