Despite the success achieved in the tree-ring dating of wood samples from archaeological excavations over the recent years, attempts to apply this method to relatively recent wooden constructions in central Siberia run into considerable difficulties, because the increment of wood in that area shows little variation due to the virtual absence of limiting factors. To solve this problem, we used the blue intensity method, based on measuring the optical density of wood. This method is more sensitive to environmental changes of annual growth rates and is optimal in terms of efficiency and cost. This article describes the techniques of sample preparation, measuring optical density of annual rings, and the construction of chronologies based on this indicator. The efficiency of the method is assessed by comparing it with the traditional approach based on tree-ring width for dating wood from the temperate zone of Siberia. Results of dating two wooden structures (the Gromov house (1870) and the Gafarov store (1909)) indicate the efficiency of the new method virtually without limiting factors affecting increment rates.

ЭКСТРЕМАЛЬНЫЕ КЛИМАТИЧЕСКИЕ СОБЫТИЯ В ЦЕНТРАЛЬНОМ АЛТАЕ ЗА ПОСЛЕДНИЕ 1500 ЛЕТ ПО ДАННЫМ ДРЕВЕСНО-КОЛЬЦЕВОЙ ХРОНОЛОГИИ JELO

In recent years, dendrochronological analysis in archaeology has undergone a substantial transformation, offering an opportunity to use samples of wood that were previously considered uninformative. One striking example is the analysis of charcoal excavated from archaeological sites. We have studied 448 samples of charcoal collected from metallurgical (iron smelting) furnaces in the Kurai and Chuya basins of the Russian Altai Mountains. Earlier methods of preparing such samples were slow and ineffi cient. Our approach guarantees fast, simple, and high-quality preparation of a large number of samples of virtually any size and shape. Its advantages include low cost of apparatus, high quality measurement of annual rings, the possibility of effi cient remote measurement, no need for verifi cation, and a wider range of measured parameters of the annual ring. Hopefully, the new approach will help to solve the critical problem relating to the construction of a tree-ring chronology in the arid zone of Southern Siberia. Such a c hronology will be highly prospective for assessing the age of wood from numerous mounds in the intermountain depressions of the Altai- Sayan region, and year-by-year reconstructions of the humidity regime; and for revealing extreme droughts and other climatic phenomena in this territory.

Archaeological charcoal from ancient nomad iron-smelting furnaces collected in the highland southeastern Russian Altai has great potential as a material for tree ring analysis. Dendrochronological dating was applied to 355 viable samples (>80% of the 448 collected ones), prepared using a new protocol. Individual tree ring series of 155 (~43%) samples were used to construct nine floating chronologies from 76 to 290 rings long. The archaeological and radiocarbon data on charcoal that fueled the hearths of the Kosh-Agach type bracket the floating tree ring chronologies between the second and tenth centuries AD. The results demonstrate that long tree ring “steppe” chronologies can be obtained for intermontane basins in the arid zone of Southern Siberia, using the analysis of charcoal samples. A strong climate signal imprinted in the annual growth of trees allowed for crossdating samples with relatively few rings. The revealed common climate signal for larches from different locations indicates similar paleoclimate conditions of their growth despite the strong modern southeastward aridization trend in the region, which was not so pronounced ca. 1.5 ka ago. The further matching of these chronologies to the calendar timeline will provide reference for the precise comparison of climatic conditions in the floors of intermontane basins and in the flanking mountains.

Significant air temperature and precipitation changes have occurred since the 2000s in vulnerable Siberian subarctic regions and urged updates of available chronologies towards the third millennium. It is important to better understand recent climatic changes compared to the past decades, centuries and even millennia. In this study, we present the first annually resolved triple tree-ring isotope dataset (δ¹³C, δ¹⁸O and δ²H) for the eastern part of the Taimyr Peninsula (TAY) and northeastern Yakutia (YAK) from 1900 to 2021. We found that the novel and largely unexplored δ²H of larch tree-ring cellulose was linked significantly with δ¹⁸O for the YAK site, which was affected by averaged April–June air temperatures and evaporation. Simulated by the Land Surface Processes and Exchanges (LPX-Bern 1.0) model, the water fraction per year for soil depths at 0–20 and 20–30 cm was significantly linked with the new eco-hydrological tree-ring δ²H data. Our results suggest increasing evapotranspiration and response of trees’ water relation to rising thaw water uptake from lower (20–30 cm) soil depth. A positive effect of July air temperature on tree-ring δ¹⁸O and a negative impact of July precipitation were found, indicating dry conditions. The δ¹³C in larch tree-ring cellulose for both sites showed negative correlations with July precipitation and relative humidity, confirming dry environmental conditions towards the third millennium.