We examined the effects of climate (i.e. temperature, precipitation, moisture index, river discharge) on the radial growth of eastern white pine (Pinus strobus) in two contrasting microhabitats (floodway versus terrace) in relation to an elevational and moisture gradient along the banks of the Red Cedar River, Michigan. We hypothesized that trees growing on the terrace sites would have a greater sensitivity to climatic factors than trees growing in the floodway. Increment cores were sampled and crossdated from dominant and co-dominant trees in the floodway and terrace sites and standardized growth chronologies were developed. Mean sensitivity, standard deviation, percentage of absent rings, and intertree correlation were generally greater for eastern white pine on the terrace compared to the floodway forests. Dendroclimatic relationships were examined with bootstrapped correlation analysis, which indicated that radial growth of eastern white pine in both floodway and terrace sites was negatively associated with summer temperature (i.e. June and July) of the current growing season. Radial growth in both floodway and terrace sites were positively related to current May precipitation, moisture index, and river discharge. Dendroclimatic response of eastern white pine in floodway and terrace sites differed in that the effect of summer moisture stress was more persistent in the terrace sites into later summer (i.e. current July ) whereas floodway sites showed a negative response to prior-year May precipitation and moisture index. Although precipitation and hydrological conditions of the river were generally favorable during the summer months, which appeared to have promoted soil moisture recharge, flooding in early winter (i.e. prior November) had a negative impact on growth in both microhabitats. The effect of winter river discharge was significantly negative in January (t) in the floodway sites compared to the terrace sites.

Silver fir trees grown outside their natural distributional range were intensively studied in terms of their adaptability to increased late winter temperature and extreme weather events. The main questions of the study are: what is the influence of March temperature increase on tree rings and is the further introduction of silver fir outside its natural range economically justified? A total of 268 cores of silver fir were obtained from 12 sites throughout north Poland, which were located outside its natural range. Next, standard dendrochronological and dendroclimatological methods were applied. The March temperature increase was investigated using the bootstrap running correlation option with a 25-year moving window. Response function analysis revealed that the studied trees were more sensitive to winter temperature than to precipitation. Hierarchical cluster analysis identified two distinct geographical regions of fir growth. The positive effect of high March temperature is observed in both regions. Trees from the northwestern Poland region recovered from an extreme cold period in the following year, whereas trees from northeastern Poland were more sensitive, and needed an additional year for recovery. The reason for the relatively fast growth recovery in northwestern Poland is the influence of the mild Atlantic and Baltic climates.

Machaerium scleroxylon (morado) is an important timber species from the lowland tropical dry forests in Bolivia. We followed a dendrochronological approach to (i) evaluate the responses of radial growth to climatic variables and atmospheric circulation patterns, and (ii) quantify the growth rate in order to estimate the Minimum Logging Diameter (MLD), age, and optimal cutting rotation. We measured tree-ring width in wood discs taken from ten randomly selected mature individuals. We used previous histological analyses to distinguish and visually crossdate tree rings. Despite the existence of false rings, lenses and wedging rings, the species showed defined annual ring boundaries, thus enabling a tree-ring chronology analysis. Correlations between residual ring-width indices and monthly climatic variables (temperature and rainfall) and atmospheric circulation patterns (El Niño-Southern Oscillation) index were calculated. Growth showed a significant positive correlation with monthly rainfall and a negative correlation with mean temperature during the late rainy season (i.e. from December up to March). A positive correlation found between the ring width and ENSO indices indicates that the growth of M. scleroxylon was significantly affected by atmospheric circulation patterns. Growth rate is slow in morado, suggesting a MLD of 50 cm and an optimal cutting cycle longer than 40 years depending on each site.

The creation of chronologies from intra-annual features in tree rings is increasingly utilized in dendrochronology to create season-specific climate histories, among other applications. A conifer latewood-width network has recently been developed for the southwestern United States, but considerable uncertainty remains in understanding site and species differences in signal strength and sample depth requirements. As part of the 22nd annual North American Dendroecological Fieldweek, the first Pinus ponderosa earlywood-width (EW) and latewood-width (LW) chronologies were developed for the Jemez Mountains in northern New Mexico. The aim was to extend an existing total ring-width (TW) chronology and to assess the potential for creating long LW chronologies. Analysis of chronology signal strength suggests that large sample size requirements remain a considerable hurdle for creating P. ponderosa LW chronologies longer than 400 years. At the Cat Mesa site, twenty-three sample trees were required to capture a statistically acceptable common signal in adjusted latewood (LW_a), whereas only four samples were required for EW. This is significantly higher than sample depth requirements for LW_a from the few other chronologies in the region where this statistic has been reported. A future priority should be to develop a conceptual guide for site and tree selection in order to maximize the potential for enhancing LW signal and for creating a robust network of multi-century LW chronologies.

The discovery of exceptionally well-preserved Paleogene wood fossils (ca. 55–53 Ma) within Canadian Arctic diamond-bearing kimberlites prompted a paleoclimatic study of the Paleocene-Eocene Transition. The samples are not petrified, but have been “mummified” by their inclusion in pyroclastic debris and still contain primordial wood material. However, preferential cellulose loss has rendered the wood very fragile, precluding the use of standard dendrochronological methods of surface preparation. Similar to archaeological charcoal, breaking the mummified wood allows superior visualization of tree-ring boundaries and wood anatomy, but often produces irregular surfaces making microscopic examination difficult. Therefore, a simple aluminum clamp was constructed to break radial wood transects in a controlled manner for the purpose of collecting dendrochronological and wood-anatomical data for paleoclimatic reconstructions. Because it does not require the use of chemical treatments or stabilizing resins, the wood remains chemically unaltered, allowing chemical and isotopic analyses to be undertaken. Future studies of fragile woods may benefit from this method of controlled breaking if sanding is ineffective.

La découverte de fossiles bois du Paléogène (55–53 Ma), exceptionnellement bien conservés, dans des kimberlites diamantifères dans l'Arctique canadienne a incité à une etude paléoclimatique de la transition Paléocène-Eocène. Les échantillons ne sont pas petrifies. Ils ont été «momifié» de par leur inclusion dans des débris pyroclastiques et contiennent toujours du matériel du bois primordial. Toutefois, la perte de cellulose préférentiel a rendu le bois très fragile, ce qui exclus l'utilisation de méthodes dendrochronologiques usuelles afin de preparer la surface. Comme pour les charbons de bois archéologiques, en brisant le bois momifié, il est possible de visualiser avec acuité les frontières des arbres-anneau et l'anatomie du bois. Cependant, ceci produit souvent des surfaces irrégulières qui rendant l'examen microscopique difficile. Par conséquent, une pince en aluminium simple a été construite afin de briser des transects radiaux de bois de manière contrôlée, dans le but de recueillir des données dendrochronologiques et des données de l'aspect anatomique du bois, afin d'établir des reconstructions paléoclimatiques. Parce que l'utilisation de traitements chimiques ou de résines de stabilisation n'est pas néccessaire, le fossile de bois reste chimiquement inchangé, ce qui permet des analyses chimiques et isotopiques. Les études futures de bois fragiles peuvent bénéficier de notre méthode de rupture contrôlée si le ponçage est inefficace.

This report describes an international summer course, “Tree Rings, Climate, Natural Resources, and Human Interaction”, held in Valsaín, Spain, in summer of 2012. The course, with 14 participants from three countries (Spain, Algeria, and Russia), included basic training in dendrochronology skills as well as applied projects in dendroclimatology, dendroecology and dendrogeomorphology.