This study aims to strengthen dendroclimatic research in tropical dry forests by analyzing tree rings from Handroanthus chrysanthus and Bursera graveolens in southern Ecuador. We developed new dendrochronological records to determine the dendroclimatic potential of the species for evaluating the relationship between precipitation and tree growth. Chronologies were correlated with regional climate parameters, as well as with spatial patterns of Sea Surface Temperature (SST) anomalies. Besides dendroclimatic analyses, we propose enhancing Organic Code of the Environment (COA) regulations to promote the use of forest species with dendroclimatic potential, including Faculty number thirteen. Two tree-ring width chronologies were developed based on 39 H. chrysanthus and 53 B. graveolens trees. Tree growth shows strong correlations with precipitation during the rainy season, indicating that these species preserve reliable climatic information. This evidence supports the use of tree-ring data to inform climate adaptation and forest management strategies. Based on these findings, we propose incorporating a regulation within COA (Faculty no. 13) to "implement measures for the protection, sustainable management, and restoration of long-lived forest species with dendroclimatic potential in southern Ecuador." This enhancement can contribute to evidence-based environmental policy and strengthen climate adaptation strategies in the region.
Dendrochronology offers valuable insights into global environmental change, yet the field remains geographically biased toward northern latitudes, leaving tropical Africa relatively underrepresented. The African Dendrochronological Fieldschool (ADF) addresses this gap through training and research to expand knowledge of ring formation and environmental variation, and to build research capacity. We present case studies from the first three ADFs (2021-2023), spanning wood anatomy, dendroecology, dendroclimatology, and dendrochemistry studies from Miombo woodlands near Kitwe, Zambia. Wood anatomical characterization for 13 species, many of which have not been assessed before, indicated two are semi-ring-porous, but most (11 of 13) are diffuse-porous, and five show indicators of annual ring formation. Dendroecological studies characterized stand diversity and establishment history and produced a mixed-species chronology (series intercorrelation = 0.42). Dendroclimatological research yielded chronologies of Brachystegia longifolia and B. boehmii (series intercorrelations of 0.38 and 0.44, respectively) and found significant relationships (p , 0.05) between wet-season precipitation and growth for B. boehmii B. longifolia revealed bioaccumulation of pollutants linked to local soil contamination, including As, Pb, and Sc. These findings demonstrate the applicability of several African tree species for dendrochronological research and underscore the importance of continued capacity building.
In this article, we introduce new methods for taking core samples from wooden beams for dendrochronological analysis and crossdating from uncharred archaeological wood in arid environments. Although many advancements in the analysis of tree-ring samples have occurred over the century since A.E. Douglass first developed dendrochronology, few advancements in the methods of core sample collection have occurred since those he established. With the methods outlined in this article, we hope to provide researchers new, more effective, and efficient ways to sample archaeological wood on-site, methods that are also aimed at reducing the impact of core sampling on archaeological materials and cultural resources, while also reducing the visual impacts to irreplaceable cultural resources. We developed these methods over years of trial and error, and we encourage others to use this how-to-guide and expand on its applications. Although the techniques and tools we describe were developed in the US Southwest, they are readily applicable to arid and semi-arid regions elsewhere in the world.
The field of dendrochronology is currently undergoing a transition, with an increasing reliance on digital analysis. Recent advances in hardware and software have enabled the rapid acquisition of information from wood in ways that were previously unattainable. However, the variety of digitization tools and the high resolutions achievable present a challenge in maintaining replicability and comparability of results. In addition, the high speed at which data are collected can lead to overlooking important aspects of dendrochronological techniques. For example, awareness of resolution of images for tree-ring measurements or even crossdating may play a minor role when setting tree-ring boundaries or may be biased towards the first samples measured. This commentary addresses potential sources of error in the novel advances of digital techniques and highlights the suitability of combining digital advances with traditional data-control procedures that maintain the robustness and replicability of dendrochronological methods.
The widely used open-access COFECHA program requires manual keyboard input to cross-match an undated tree-ring series with a dated master series. The COFECHA program, like its commercial alternatives, has no option to execute a sequence of runs with the exclusive input from a file. The user trying to crossmatch a set of undated tree-ring series with a large regional set of dated series faces a cumbersome task: the user must manually repeat the input for each new run with an individual undated series even though the regional set of dated master series is identical to that of the previous run. Unlike its commercial counterparts, the COFECHA program lends itself to running from an external script file. The most convenient script is a Windows AutoHotkey script. Two example scripts are available on https://github.com/mathgeol/cros25. Using a text editor, the regional set of dated series file names is input only once, and it is used in all the following automated runs with a new undated series.
The Australia-New Zealand Tree-Ring Conference was held January 21-23, 2025, at Waipapa Taumata Rau/University of Auckland, in Aotearoa/New Zealand. It was intended to provide an opportunity for the Australian and New Zealand dendrochronological researchers to meet, present current research, and discuss the challenges and opportunities in working with Southern Hemisphere tree species, but it was open to others outside of Australasia, including some keynote speakers. The meeting brought together many researchers from within and outside academia for the first time since the pandemic, and in addition to providing a look at current interesting and ongoing dendrochronology projects, it promoted camaraderie for this regional tree-ring community.
Seaside juniper (Juniperus maritima) is a recently identified cryptic, rare tree species endemic to the Salish Sea region. This study reports on the first dendrochronological investigation of the species. We sought to determine if seaside junipers are capable of crossdating and to identify correlations between instrumental climate records and radial growth. We collected tree core samples from seaside juniper in five sites throughout the San Juan Islands and nearby mainland in Washington State. We encountered pervasive issues with broken and partially rotten cores. The lobate growth form characteristic of junipers and frequency of missing rings created additional challenges for crossdating samples. Furthermore, most stands were relatively young, with few or no trees that established prior to the early 20th Century. However, samples collected from one of five sites successfully crossdated. Pearson's correlation analysis revealed that the dominant growth-limiting factor of the seaside junipers we sampled was growing-season minimum temperatures in both the prior year and current year. Understanding this climate-growth relationship will aid in the development of a conservation strategy for this rare and endemic species.
The world's longest tree-ring chronology comprises thousands of oak and pine series from Germany and continuously covers the Holocene back to 12,325 cal BP. A lack of relict wood from the Younger Dryas cold reversal ca. 12,900-11,700 cal BP, however, challenges the extension of this absolutely dated ring width record further back in time. Here, we combine 646 high-resolution stable oxygen isotope and 795 radiocarbon measurements from subfossil pines that grew during the Younger Dryas at three different sites near Zurich, Switzerland, to extend the record. Coherency of the oxygen isotope variations secures internal crossdating, and radiocarbon wiggle-matching places the final 425-year-long ring-width chronology between 12,716 and 12,292 cal BP with an uncertainty of 68 years. Our study describes an important step towards annual dating precision further into the Late Glacial period.
Large tropical tree samples are driving new research in dendrochronology. The development of imaging tools for these substantial samples represents a significant challenge. Specifically, tree-ring measurements are strongly associated with images acquired through scanning, with an A3 large-format scanner being the preferred choice for these sizable samples. However, the literature lacks information about image distortions resulting from this approach. To address this gap, we developed a system comprising a table, a mobile scanner lift, and a fixed sample-support unit. This system ensures the production of aligned composite images of wooden disc samples and safeguards the scanning equipment from damage. To test its efficiency, we evaluated distortions in the measurements of treering widths across various digitized images at nine different heights, ranging from 2 to 10 mm. Remarkably, we observed no distortions in the growth ring measurements at any assessed height. Furthermore, the images of samples positioned 2 mm and 3 mm away from the scanner glass were clear, allowing precise measurements of small growth rings between 0.1 and 0.5 mm in size. Our equipment offers flexibility of use with other models and sizes, including A4 scanners. It can digitize wooden discs with diameters ranging from 60 to 200 cm.
Forest ecologists and dendrochronologists are beginning to recognize the conservation and research value of forest fragments. In this study, a forest fragment was studied to quantify the current vegetation composition and structure, reconstruct the disturbance history, and identify evidence of future changes in forest composition. The most important overstory trees were white oak (Quercus alba), eastern white pine (Pinus strobus), scarlet oak (Quercus coccinea), and chestnut oak (Quercus montana). This overstory composition appears to have developed during a 100-year period from 1850 to 1950, when the forest experienced continuous low-levels of disturbance. There was a timber harvest in the early 1950s, which appears to have initiated a reduction in the successful establishment of oaks and an increase in the successful establishment of red maple (Acer rubrum) and eastern white pine. Thus, although this forest fragment is not spatially connected to the larger eastern deciduous forest, it shares the regional pattern of mesophication observed across this region and is likely to experience a shift in composition towards more mesic tree species and a reduction in the dominance of oak.
The 1st Ecuadorian Dendrochronology Conference (ECUADENDRO 2025) took place in Daule, Ecuador, on January 23-24, 2025, with the generous sponsorship of the Tree-Ring Society. The event attracted 230 participants from 45 countries, bringing together leading experts in various subfields of tree-ring science, including dendroclimatology, dendroecology, dendrogeomorphology, dendroarchaeology, and cellular dendrochronology. Fifteen international speakers presented a diverse range of case studies from countries such as Ecuador, Norway, Sweden, India, Bangladesh, the United States, Brazil, Argentina, Pakistan, and Germany. Their contributions highlighted significant advancements in tree-ring research and the global progress in the field. The conference discussions emphasized emerging trends and future directions for tree-ring science, shedding light on new areas for continued research and collaboration.
Annually resolved multi-millennial records of temperature are rare in the Southern Hemisphere (SH), and even rarer are SH records of cool-season temperature. Here we present a new tree-ring chronology extending back to 42 BCE based on Athrotaxis selaginoides from southern Tasmania. The development of this chronology was complicated by multiple tree-age cohorts and growth classes. Additionally, there was a collapse in sample depth between the mid-14th and mid-16th Centuries. Therefore, we used a multiple Regional Curve Standardization (mRCS) approach to standardization but have subsequently employed piecewise adaptive detrending (PAD). PAD utilizes the Friedman Supersmoother to remove the remaining multimillennial trend likely to be the result of changing site conditions rather than climate. The chronology is significantly associated with temperature from winter through to the end of the warm season, but its association with Austral July-October temperatures is both unusual and stable. The collapse in sample depth, and four clear cohorts of trees are most likely associated with landscape scale fire events.
This study analyzes wood anatomical properties and growth-ring boundaries in 16 tree species across a tropical humid forest along an altitudinal gradient in southern Ecuador. We extracted 64 wood cores, subjecting them to meticulous microscopic examination and thin section preparation with safranin and astrablue staining for growth-ring identification following IAWA standards. Correspondence analysis linking wood anatomical features and environmental variables revealed a nuanced connection between ecological factors, elevation and microscopic growth-ring distinctiveness. Species at lower altitudes (1000 m a.s.l.) exhibit indistinct growth rings, whereas those at higher altitudes (2000 m a.s.l.) often display distinct growth-ring boundaries with thick-walled latewood fibers. Apart from the deciduous Schefflera morototoni, evergreen tropical rainforest trees dominate at both elevations. This study provides new insights into growth-ring occurrence and anatomy in Ecuadorian tropical mountain rainforest trees, setting the stage for future dendrochronological research. The analysis of microscopic growth-ring features across species, elevations, and locations in the southeastern Andes offers new perspectives on wood structure. In the context of climate change, acquiring high-quality wood anatomical and dendrochronological data is crucial to advance our understanding of how forest trees respond to climate change and to develop adapted conservation and management strategies.
A study was conducted to assess the impact of fertilization regimes on the growth and wood density of 13-year-old stands of Pinus caribaea var. hondurensis and Pinus taeda, located in an experimental area in Southeast Brazil. Growth parameters, such as total height, diameter at breast height (DBH), wood volume, and mean annual increment (MAI), were estimated using forest inventory data collected over an 8-year period. Forty-eight trees were selected, with 12 trees assigned to each of the four treatments: control and fertilized for each species. Four cores were obtained from each tree to measure wood density using X-ray densitometry, and tree-ring width series were crossdated and synchronized. The fertilization regime significantly affected the growth of P. caribaea var. hondurensis, which exhibited increased productivity, while P. taeda showed no significant growth responses. Fertilization resulted in a slight increase in wood density for P. taeda, while no changes were observed in P. caribaea var. hondurensis. Precipitation was identified as a key factor influencing wood density, with a negative correlation in P. taeda and a positive correlation with tree-ring width for both species. These findings underscore the importance of targeted fertilization strategies in forest management, particularly under varying environmental conditions.
An international summer course in dendrochronology, ''Tree Rings, Climate, Natural Resources, and Human Interaction'', was held in Amman, Jordan, in summer 2023. Drs. Ramzi Touchan and David M. Meko from the University of Arizona Laboratory of Tree-Ring Research were course instructors. The course, with 10 students from Jordan, Algeria, Tunisia, Pakistan, Greece, and the USA, included training in core-sample collection, sample preparation, crossdating, detrending, and climate signal identification. Students applied their training in group precipitation reconstruction projects. Fifty-two Pinus halepensis core samples were collected at Dibeen Forest Reserve, Jordan, which were used to develop a tree-ring chronology (1925-2022) and then used for the reconstruction models. Two reconstructions extended precipitation for Dibeen using: (1) measured October-April precipitation data (R(2)adj. = 0.63), and (2) gridded November-April precipitation data (R(2)adj. = 0.61). A third reconstruction used the Dibeen chronology and three low-elevation tree-ring chronologies in Cyprus to extend gridded December-April precipitation data for the eastern Mediterranean region (R(2)adj. = 0.55). Results from the class projects demonstrated the success of reconstruction techniques in regions with sparse measured climate data and tree-ring chronologies. Future training classes in these regions will also promote the importance of understanding historic climate variability, which is essential for water resource managers and planners.
