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European larch (Larix decidua Mill.) holds significant importance as a forest tree species throughout the Alps and in certain regions of central Europe. Its extensive use as construction timber has made it a subject of substantial interest in dendroarchaeological studies aimed at understanding the long-term interactions between human societies and forests. Precise dating of felling phases, accurate estimation of the age of harvested wood, and information on the geographical origin of wood play a crucial role when it comes to characterize these interactions. In this study, we compiled a large dataset of L. decidua samples from across the European Alps to provide a robust statistical model that predicts the cambial age of L. decidua trees based on the number of heartwood rings. By extension, this model can be used to estimate the number of sapwood rings so as to approximate the felling date and to more precise date archaeological larch timber. The model requires almost complete heartwood sequences (<5 missing rings) to achieve accurate estimations. Our results also evidence that the ratio between the number of sapwood and heartwood rings varies across the Alps. At the same time, the indicator developed in this work is not suitable for a determination of wood origin, raising doubts about the effectiveness of attempts aimed at dendroprovenancing L. decidua based on sapwood. [ABSTRACT FROM AUTHOR]

A steep decline in the quality and quantity of available climate proxy records before medieval times challenges any comparison of reconstructed temperature and hydroclimate trends and extremes between the first and second half of the Common Era. Understanding of the physical causes, ecological responses and societal consequences of past climatic changes, however, demands highly-resolved, spatially-explicit, seasonally-defined and absolutely-dated archives over the entire period in question. Continuous efforts to improve existing proxy records and reconstruction methods and to develop new ones, as well as clear communication of all uncertainties (within and beyond academia) must be central tasks for the paleoclimate community. [ABSTRACT FROM AUTHOR]

Abstract: The potential of dendrochronological analysis of wood found in prehistoric and historic mining areas in Tyrol has remained unattended for a long time. For the first time, systematically analysed wooden artefacts from a prehistoric mining area in Tyrol (Kelchalm near Kitzbühel) can be presented here. The investigated artefacts, related to mining and everyday life, were found in the course of archaeological excavations, which were carried out between 1932 and 1953 by Richard Pittioni and Ernst Preuschen. Taking an adequate number of tree rings and well-preserved wood wane into account, 21 pieces of mining timber were pre-selected for a dendrochronological analysis. The identified wood species are spruce (Picea abies, n=18) and fir (Abies alba, n=3). The length of the established tree-ring series ranges from 13 to 145. We cross-dated the tree-ring series of seven wooden artefacts among each other, which resulted in a spruce-fir tree-ring record of 153 values (Kelchalm mean curve). The last tree ring measured of the Kelchalm spruce-fir mean curve dates back to 1237 BC. This accurate dendro-result dates the Bronze Age mining activities at the Kelchalm to about two centuries earlier than the long-lasting assumption proposed by Richard Pittioni. His assumption was based on the typology of ceramic and metal artefacts. The established dendro-date for the Bronze Age mine at the Kelchalm matches with available 14C results from other important copper-mining areas in the north-eastern Alps (NE Alps). The activities at these other sites are dated between the 17th and 6th century BC. Furthermore, the radiocarbon dating, as well as the dendro-result from the Kelchalm, suggests a transition from earlier mined copper-ore deposits in the eastern areas of the NE Alps, to the later mined ore deposits in the western section. This has led to both parallel and sequential mining activities in several ore districts during the last two millennia BC in the NE Alps. [Copyright &y& Elsevier]

Abstract: Cubic smoothing splines with a fixed-period response are used widely in producing “expected” growth curves for ring-width and density data in dendroclimatology. A simple modification to the procedure which generates these splines enables the use of a smoothing spline with a user-specified, time-varying flexibility and hence time-varying-response characteristics. The revised procedure is presented here, along with different examples of its application in the context of Regional Curve Standardisation (RCS). The ability to generate a smoothing spline with time-dependent flexibility may have wider application in tree-ring studies. [Copyright &y& Elsevier]

• We present successful dating of 763 samples from the archaeological sites in Hallstatt. • Felling dates between the 12th and the 2nd century B.C. (with gaps). • New chronologies developed for Silver fir, Norway spruce, European larch and beech. • Precise dates of salt mining activities in Hallstatt. The prehistoric salt mine of Hallstatt together with its burial ground is one of the most prominent archaeological sites in the world, and has given its name to the "Hallstatt period", an epoch of European prehistory (800 to 400 BCE). Due to the perfect conservation in rock salt a high number of organic materials have been found, including mostly wooden artefacts and structural timber. More than 2000 samples were taken from various archaeological sites in the mines as well as at the surface. It was possible to date 763 samples by the means of dendrochronology and by 14C wiggle matching. The dendrochronological dating was possible due to crossdating with various available chronologies (like Villingen-Magdalenenberg or Dachstein/Schwarzer See). The fir (Abies alba Mill.) chronologies span the periods: -1232 to -1063; -819 to -425 and -371 to-129. The spruce (Picea abies L. Karst.) chronologies span the periods: -1228 to -1063; -813 to -669 and -342 to -123. The larch (Larix decidua Mill.) chronologies span the periods: -1393 ± 18 to-1286 ± 18 based on wiggle matching data and -252 to -164. A beech (Fagus sylvatica L.) chronology span the time -1182 to -1062. [ABSTRACT FROM AUTHOR]

For dendroclimatological Blue Intensity (BI) studies based on earlywood (EW) or latewood (LW) information, a demarcation between the two is necessary, which can be difficult to establish for species where the transition is subtle. Often, a percental value k is used that calculates an EW/LW boundary value for each tree ring individually based on the difference between maximum and minimum absorption. Several laboratories and authors have used different values for k (e.g. k = 30 % or k = 50 %), while wood anatomical and visual studies suggest that k is on the order of 80 %. Here, we test how different settings of k, and thus different definitions of the EW and LW proportions of a tree ring, influence the dendroclimatic potential of derived time series. To this end, we correlate instrumental temperature measurements with tree ring chronologies that are based on EW and LW information (e.g. EW absorption (EWBI), LW absorption (LWBI)), where the EW/LW proportion is varied by setting different values for k. The tree ring samples utilized are 30 cores of spruce (Picea abies) trees from a high-elevated site (ca. 1700 m a.s.l.) in the northern Alps, Austria. Overall, we achieve high correlations between temperature data and our tree ring chronologies. Regarding the stability of the climate signal under different k values, the results show that absorption intensity based parameters (ΔBI, EWBI, LWBI) are only mildly influenced by different settings of k, while width based parameters (EW width, LW width) show a larger dependence on k. LW width, for instance, was stronger correlated with temperature, the smaller the LW was chosen (and thus the higher k was set). Based on our results and the wood anatomical definition of the EW/LW boundary, we suggest that k = 80 % may be a good choice for future studies. However, since this is only a case study from one site, careful screening of the respective data set regarding an appropriate k value must accompany each dendroclimatological study. [ABSTRACT FROM AUTHOR]

Climate reconstructions for the Common Era are compromised by the paucity of annually-resolved and absolutely-dated proxy records prior to medieval times. Where reconstructions are based on combinations of different climate archive types (of varying spatiotemporal resolution, dating uncertainty, record length and predictive skill), it is challenging to estimate past amplitude ranges, disentangle the relative roles of natural and anthropogenic forcing, or probe deeper interrelationships between climate variability and human history. Here, we compile and analyse updated versions of all the existing summer temperature sensitive tree-ring width chronologies from the Northern Hemisphere that span the entire Common Era. We apply a novel ensemble approach to reconstruct extra-tropical summer temperatures from 1 to 2010 CE, and calculate uncertainties at continental to hemispheric scales. Peak warming in the 280s, 990s and 1020s, when volcanic forcing was low, was comparable to modern conditions until 2010 CE. The lowest June–August temperature anomaly in 536 not only marks the beginning of the coldest decade, but also defines the onset of the Late Antique Little Ice Age (LALIA). While prolonged warmth during Roman and medieval times roughly coincides with the tendency towards societal prosperity across much of the North Atlantic/European sector and East Asia, major episodes of volcanically-forced summer cooling often presaged widespread famines, plague outbreaks and political upheavals. Our study reveals a larger amplitude of spatially synchronized summer temperature variation during the first millennium of the Common Era than previously recognised. [ABSTRACT FROM AUTHOR]