With increasing concerns about sustainable exploitation of tropical timber, there is a need for developing independent tools to check their origin. We evaluated the potential of tree-ring stable isotopes for identifying four Cedrela species (C. balansae, C. fissilis, C. odorata, and C. saltensis) and for identifying geographic origin of C. fissilis and C. odorata, two of the most intensively exploited species. We studied differences in δ¹³C and δ¹⁸O of wood among 11 forest sites (163 trees). We quantified isotope composition of 10-year bulk samples, and for a subset we also evaluated isotopic annual fluctuations for the last 10 years. Although annual isotopic variability was not correlated to precipitation or elevation, we found a significant relationship between the 10-year bulk stable-isotope composition and average precipitation and elevation. However these relationships were not consistent across all sites. We also explored isotopic site and species differentiation using Kernel Discriminant Analyses. Site discrimination was low: 30% accuracy for C. odorata, and 40% for C. fissilis sites. However, species discrimination was 57.5% for C. odorata and 95.3% for C. fissilis. These results suggest that although δ¹³C and δ¹⁸O isotopic analyses hold potential to verify species identification, discrimination of geographical origin within a country may still be challenging.

There is a tendency of warming and wetting in northwestern China in recent decades. However, less is known about whether or not tree growth shows an increasing trend. In this study, we developed three tree-ring width chronologies of Picea schrenkiana in the northern Tianshan Mountains to assess changes in the radial growth of P. schrenkiana and to discuss the stability of the relationships between tree growth and climate. Three chronologies all showed that the tree-ring index has declined significantly since the 1960s. At two western sites, the growth of P. schrenkiana was negatively affected by the summer temperature of the previous year. At the eastern site, early summer temperature-induced drought of the current year was the key factor affecting tree growth. The result of moving-window correlations was consistent with correlation analyses. Spatial correlation analyses revealed that variations in tree-ring width could respond to a wide range of temperature changes in northwestern China, especially in the past half century. We expect that climate warming hinders the radial growth of P. schrenkiana in the northern Tianshan Mountains. Our study also helps to clarify the characteristics of tree growth in northwestern China under the influence of westerlies.

Wiggle-matched ¹⁴C dates anchored an 82-year floating cedar tree-ring chronology from the basal layer of a Mississippian Period mound to AD 1170 ± 9 (1σ) (outermost ring). Although numerical cross-matching showed preference for a temporal placement consistent with the ¹⁴C dates and visual matching, statistical scores were below critical thresholds for annual crossdating. Sapwood-corrected terminus post quem dates for the material, and their stratigraphic relationship with overlying dates, show that the earliest truncate mound construction at Mound 4 occurred after AD 1177. This date is informative for the timing of the transition of Kincaid to a major regional center and does not support an earlier hypothesis that Mound 4 was constructed in Early Kincaid times (AD 1050–1150). These results demonstrate the potential for archaeological collections to extend long tree-ring chronologies in the Midwestern U.S.

Long-term paleoclimate reconstructions of temperature provide context for the magnitude of recent anthropogenic warming, help quantify the climate response to radiative forcing, and better characterize the range of natural variability. In North America, temperature-sensitive tree-ring proxy data remain sparse, which limits the spatial and temporal extent of these reconstructions. Here we present an analysis of yellow-cedar (Callitropsis nootkatensis) growth in Washington State (USA) and its relationship to climate. Combining empirical statistical analysis with a process model of xylogenesis, we show that tree-ring chronologies from three high-elevation sites in the North Cascades are primarily controlled by temperature. We then use these chronologies to reconstruct summer temperatures over the period 1333 to 2015 CE, adding a new proxy to the North American network of temperature-sensitive trees. Comparison with an existing large-scale spatial gridded reconstruction suggests this species offers important local and regional information on past temperatures.

This report describes an international summer course, “Tree Rings, Climate, Natural Resources, and Human Interaction”, held in Cheriomushki, Russia, in the summer of 2018. The course was attended by 12 participants from six countries (Belgium, India, Lebanon, Poland, Russia, and South Africa) and instructors from the USA and included basic training in dendrochronology skills and dendroclimatology and dendroecology projects. This report focuses on a nested May–July Palmer Drought Severity Index (PDSI) reconstruction from annual rings of Pinus sylvestris trees growing in the region and also explores false-ring (FR) occurrence in samples collected during the course. Four chronologies, one developed during the course from Maina District, Khakassia, Russia, are used in the reconstruction, which was based on principal component (PC) regression. The nested reconstruction demonstrated a strong statistical relationship between PDSI and tree-ring growth and allowed for an assessment of climate variability on both interannual and interdecadal time scales. FR occurrence in tree cores collected along an elevational transect from a site along the Yenisei River north of Cheriomushki was found to differ depending on the position of trees on the slope. The frequency of FRs and the location of the FR within the annual ring also appear to be related to seasonal precipitation anomalies.

Dendrochronologists regularly host conferences and workshops to share tree-ring research and new methodologies. Unfortunately, national and international scientific gatherings have also historically been events where some female researchers have experienced sexual harassment, discrimination, and assault. The objective of this project was to host a focus group with experienced conference and workshop organizers to gather best practices and policies to reduce the risk of sexual misconduct at these events. A concerted effort by organizers is needed, and this begins with the development of a diverse and inclusive organizing committee. Organizers will need to craft a sexual misconduct policy that includes a clear definition, a violation reporting system with multiple reporting pathways, a review process, an enforcement system with penalties for the violator, and supportive resources for victims. Currently, the Tree-Ring Society offers organizers of workshops and conferences a definition of sexual misconduct and possible penalties for violations; however, the dendrochronology discipline currently lacks a reporting system, formalized review system, and resources for victims. We hope sharing the results of this focus group will allow future conference and workshop organizers to implement these findings and provide a safe environment for all dendrochronologists.

Increment cores with intact tree rings are crucial in dendrochronological investigations to age trees. However, it is not always possible to obtain complete cores from trees because of rot, so alternative methods need to be explored. We tested the collection of one oblique core and one straight core reaching the pith at breast height from 12 sound Scots pine (Pinus sylvestris) trees. We simulated a missing inner part (caused by hypothetical rot) from each straight core, and estimated the trees' ages from both the oblique and straight cores, using several methods. We then compared the estimates to ages obtained from the complete cores, and found that the mean absolute error was lower for estimates from partial straight cores (17.75%) than from oblique cores (47.58%). We then obtained oblique cores from 14 hollow pines affected by rot, to test the applicability of this practice to real rotten trees. We concluded that oblique coring is not suitable for pine trees because of high failure rates of coring attempts and large distances between the cores and chronological centers of the trees' stems. We recommend the collection of two cores aiming straight toward the center of trunk to increase the chances of obtaining an accurate age estimation.

Les carottes de sondage collectées sur les arbres sont d'une grande importance dans diverses études en dendrochronologie pour determiner l'âge des arbres. Cependant, les arbres creux ne permettent pas d'obtenir des échantillons comportant toutes les cernes de croissance, rendant nécessaire l'exploration de méthodes alternatives. Nous avons ainsi testé la collecte de deux carottes (une visant le centre géométrique de l'arbre, l'autre oblique évitant le coeur du tronc) sur 12 pins sylvestres sains (Pinus sylvestris). Sur chaque échantillon visant le centre, un coeur pourri a été simulé. L'âge de l'arbre a été estimé à partir de cet échantillon rendu incomplet, puis à partir de l'échantillon oblique en utilisant les méthodes appropriées. Ces estimations ont été comparées à l'âge de référence. L'erreur absolue moyenne était plus faible pour les échantillons droits tronqués (17.75%) que pour les échantillons obliques (47.58%). L'applicabilité de cette méthode a ensuite été testée sur 14 pins creux. La collecte de carottes de sondage obliques n'est pas adaptée aux pins en raison d'un fort taux d'échec d'échantillonnage, et de la distance trop importante entre les carottes et le centre chronologique de l'arbre. Il est conseillé de collecter deux échantillons droits, pour augmenter les chances d'avoir une estimation vraisemblable de l'âge.