Precise tree-ring dating of building activities despite the absence of bark: A case-study on medieval church roofs in Damme,Belgium

A detailed dendrochronological survey was performed on the medieval roofs of the Church of Our Lady (CoOL) in Damme, Belgium. Seen its complex architectural history, special attention was paid to the identification of consecutive building phases, based on combined architectural historical research and tree-ring dating. In total 64 increment cores were taken throughout the roof structures of the CoOL. All roof timbers are made of European oak (Quercus robur/petraea), of which only few have surviving sapwood or bark. Tree-ring dating confirms the late 13th/early 14th century construction date of the roofs. For all chronologies that were composed, the highest correlation values are found with reference chronologies covering the catchment area of the river Meuse. From the dating results of the timbers of the CoOL it becomes clear that the same timber source was used for nearly a century. On several of the examined roof timbers, rafting joints were observed, demonstrating that the timbers were indeed tied together as a raft and floated down the river.By implementing sapwood estimates in a Bayesian chronological model (OxCal), tree-ring series with surviving sapwood from coeval roof structures were combined in order to narrow down the time range for the felling date. Based on the refined interpretation of the felling dates, several consecutive building phases can now be identified and dated, leading to a new interpretation of the architectural history of the CoOL. Intriguingly, a marked interruption in building activities is observed around 1300. Probably this is related to the instable political situation at that time, caused by the armed conflict that emerged between the Count of Flanders and the king of France. Since Damme served as the outport of the riotous city of Bruges, it was alternately seized by the French and Flemish, both consuming considerable amounts of timber and other building materials for military fortifications. Potentially this led to a shortage in building materials and provoked a stop in building activities.This paper demonstrates the power of Bayesian models to refine the interpretation of dendrochronological dates in architectural analyses of medieval historical buildings.     

Spatial and altitudinal bioclimatic zones of the Italian peninsula identified from a beech (Fagus sylvatica L.) tree-ring network

A network of 24 beech (Fagus sylvatica L.) tree-ring chronologies has been developed for the Italian peninsula. Principal component and cluster analyses were used to identify geographical and altitudinal patterns of tree growth. Correlations and response functions were then applied to the main modes of tree-ring variability to uncover climatic signals. In a landscape occupied by humans for millennia, this approach provided a detailed quantitative ecological characterization of forest types. Altitude was significantly correlated with dendrochronological parameters. The Alps and northern Apennines could be distinguished from the central-southern Apennines. In central Italy, we recognized three different vegetation belts occupied by beech forests, from low- to high-elevation sites. Summer drought impacted beech growth with different intensity at different elevations, depending on the onset and duration of the growing season. Moreover, low-elevation beech forests showed a distinct late spring climate signal, which was opposite to that of high-elevation sites. The coherent geographical and ecological patterns of tree-ring variability suggest that dendrochronological networks help define bioclimatic zones and forest types.     

Tree-ring distinctness,dating potential and climatic sensitivity of laurel forest tree species in Tenerife Island

Macaronesian laurel forests are the only remnants of a subtropical palaeoecosystem dominant during the Tertiary in Europe and northern Africa. These biodiverse ecosystems are restricted to cloudy and temperate insular environments in the North Atlantic Ocean. Due to their reduced distribution area, these forests are particularly vulnerable to anthropogenic disturbances and changes in climatic conditions. The assessment of laurel forest trees’ response to climate variation by dendrochronological methods is limited because it was assumed that the lack of marked seasonality would prevent the formation of distinct annual tree rings. The aims of this study were to identify the presence of annual growth rings and to assess the dendrochronological potential of the most representative tree species from laurel forests in Tenerife, Canary Islands. We sampled increment cores from 498 trees of 12 species in two well-preserved forests in Tenerife Island. We evaluated tree-ring boundary distinctness, dating potential, and sensitivity of tree-ring growth to climate and, particularly, to drought occurrence. Eight species showed clear tree-ring boundaries, but synchronic annual tree rings and robust tree-ring chronologies were only obtained for Laurus novocanariensis, Ilex perado subsp. platyphylla, Persea indica and Picconia excelsa, a third of the studied species. Tree-ring width depended on water balance and drought occurrence, showing sharp reductions in growth in the face of decreased water availability, a response that was consistent among species and sites. Inter-annual tree-ring width variation was directly dependent on rainfall input in the humid period, from previous October to current April. The four negative pointer years 1995, 1999, 2008 and 2012 corresponded to severe drought events in the study area. This study gives the first assessment of dendrochronological potential and tree-ring climate sensitivity of tree species from the Tenerife laurel forest, which opens new research avenues for dendroecological studies in Macaronesian laurel forests.     

Anatomy of growth rings at the Yucatán Peninsula

The dendrochronological characteristics of 52 tree species from the semi-tropical forests of the Yucatán Peninsula were opportunistically explored in a salvage dendrochronological study. The existence of clear growth rings in these trees is a key prerequisite for further studies and a convincing demonstration of the dendrochronological potential of tropical tree species will allow the development of future research programs concerning the ecology of the species and inferences about past environmental changes detected from tree rings. Many aspects of the conservation and management of Yucatec forests should be urgently addressed to aid in the development of improved strategies beyond the scope of more traditional agricultural uses. Development of tree-ring analyses from selected local species can be of substantial assistance in these initiatives.     

An assessment of growth ring identification in subtropical forests from northwestern Argentina

Most subtropical forests in South America are located in regions with a marked seasonality in precipitation, which may induce the formation of annual bands in woody species. Due to the lack of precise information on tree-ring visibility, we evaluated the wood characteristics of 37 tree species in the subtropical Yungas and Chaco forests from northwestern (NW) Argentina. Anatomical features associated with the delimitation of growth bands were examined to establish the presence of tree rings. Different forest types reflect the precipitation gradients and wood anatomical features vary accordingly. Characteristics of wood structure are closely related to the dominant climatic patterns of each forest, revealing a common pattern of anatomical arrangements in terms of water transport and safety. In the Chaco and transitional forests, ring boundaries are related to marginal parenchyma whereas in montane forests growth ring boundary is mostly associated with the presence of thicker fibers at the end of the ring. The largest proportion of species with clearly marked growth rings occurs in the montane forest type of NW Argentina. Clear growth rings is a requisite for dendrochronological applications, hence the present work represents the first regional attempt to address the potential of subtropical species in South America to be used in dendrochronological studies.     

Lauraceae: A promising family for the advance of neotropical dendrochronology

The botanical family Lauraceae is ecologically and physiognomically very important in neotropical forests. It is one of the most frequent and distributed family both in number of individuals and species. Despite of this, we have noticed that a very few Lauraceae species have been considered in dendrochronological investigations. In order to analyze the potential of Lauraceae species in dendrochronology and to facilitate future studies we: (1) reviewed the literature on wood anatomy, cambial activity, tree growth and dendrochronology and compiled a list of species’ tree-ring features throughout the Neotropics; (2) Investigated wood anatomy, growth synchronism and climate-growth relationship using dendrochronological standard techniques in 14 species from subtropical forests of southern Brazil. Our review pointed out that the majority of Lauraceae forms distinct tree-rings in several biomes and climates in the Neotropics. Seasonal growth pattern related to water stress and to seasonal air temperature were identified in Amazonia and in subtropical high elevation sites, respectively. Time series of tree-ring width of Lauraceae species were successfully cross-dated and were already used in reconstruction of fire and vegetation dynamics. Our own dendrochronological investigations brought to light that all the 14 studied species form distinct tree-rings in seasonal or even rainforests. By analyzing time series of tree-ring width we found the same growth tendency within trees of Cinnamomum amoenum and Ocotea pulchella. Moreover, year-to-year variation in the growth time-series was linked to climate variations of temperature and precipitation, showing growth decreases when summer water stress occur. We evinced Lauraceae has distinct, synchronic and climate-sensitive tree-rings. Therefore, since Lauraceae has wide distribution and high frequency in the Neotropics and since many species become centenary, we strongly encourage the use of Lauraceae’s tree-rings in autoecology, climatology and on the reconstruction of vegetation and disturbance dynamics.     

Anatomy of growth rings at the Yucatán Peninsula

The dendrochronological characteristics of 52 tree species from the semi-tropical forests of the Yucatán Peninsula were opportunistically explored in a salvage dendrochronological study. The existence of clear growth rings in these trees is a key prerequisite for further studies and a convincing demonstration of the dendrochronological potential of tropical tree species will allow the development of future research programs concerning the ecology of the species and inferences about past environmental changes detected from tree rings. Many aspects of the conservation and management of Yucatec forests should be urgently addressed to aid in the development of improved strategies beyond the scope of more traditional agricultural uses. Development of tree-ring analyses from selected local species can be of substantial assistance in these initiatives.     

Dendrochronological evidence of cockchafer (Melolontha sp.) outbreaks in subfossil tree-trunks from Tovačov (CZ Moravia)

In dendrochronological dating, we encounter the trouble that some samples cannot be dated due to the occurrence of anomalies in the tree-ring series. When dating subfossil wood for the extension of existing master chronologies, this may be an especially unwanted circumstance as subfossil wood is scarce and each sample is valuable. In Moravia (Czech Republic) outbreaks of the cockchafer (Melolontha sp.) used to appear with a disastrous effect on agricultural crops, and, for a dendrochronologist, on samples of wood to be dated. Oak ring width reduction caused by cockchafer induced defoliation can superimpose climate induced growth variations and may complicate dating of historical or subfossil samples. For this study, 33 samples of sub-fossil trunks were assessed; 19 of which were attacked by cockchafer. For comparison, we analysed a total of nine living oak trees from the forest district Strá?nice-Vracov, recently attacked by the cockchafer. Occurrence of the cockchafer was reported there in 1999, 2003 and 2007.We found clear growth patterns with cyclic narrow rings every 4 years. This allowed us to create an artificial curve expressing the recurring cycles of cockchafer outbreaks which assisted us in the detection of the same pattern in subfossil tree growth. The tree-ring series of the attacked living oak stand as well as the 19 individual tree-ring series from subfossil oak trunks could not be dated using standard chronologies and showed a high resemblance to the cockchafer life cycle. Additionally, we found out that the living oak stand was attacked in 1983, 1987, 1991 and 1995 as well. The results support the hypothesis that the periodical reduction observed in tree-rings at regular increments is caused by cockchafer infestation. This evidence is further supported by characteristic anatomical features in early wood. A mean tree-ring series was created from the individual tree-ring series of subfossil oaks even though radiocarbon dating showed completely different ages of samples. This means that the affected tree-ring series cannot be used for dendrochronological dating and dendroclimatological analyses. These series cannot be used without preceding mathematical and statistical modification.     

The effect of climate on radial growth of Quercus liaotungensis forest trees in Loess Plateau, China

Annual ring growth of Quercus liaotungensis trees in natural forests bounded by desertified region in the Loess Plateau of China was investigated for the evidence of climatic influence. Increment cores were sampled and cross-dated for 120 trees from six stands 0.5–2.5 km apart. Site tree-ring chronologies were created using general dendrochronological techniques. The results of correlation analyses between tree-ring indices and monthly climatic variables indicated that radial growth was positively correlated with precipitation in September of the previous year and that from April to June of the current year. Ring widths were negatively affected by temperature during spring and summer. In contrast, mild temperature in the previous October showed a positive influence. The results suggest that precipitation is important in the early growing season when soil and air are dry, and that high temperatures tend to reduce radial growth in this region. September rainfalls and a warm October may provide conditions that facilitate carbon storage, favor soil microbial activity, and promote root growth and shoot maturation against detrimental effects of stresses in the following seasons. There were also some differences among plots in the effects of both climatic variables probably as a result of different structures and geographical conditions that modified microenvironments. The results may contribute to the reforestation management of the area. It is expected that Q. liaotungensis forests should be ecologically established in this region on shady and half-shady slopes where air and soil drought stresses are not serious.     

No systematic effects of sampling direction on climate-growth relationships in a large-scale,multi-species tree-ring data set

Ring-width series are important for diverse fields of research such as the study of past climate, forest ecology, forest genetics, and the determination of origin (dendro-provenancing) or dating of archaeological objects. Recent research suggests diverging climate-growth relationships in tree-rings due to the cardinal direction of extracting the tree cores (i.e. direction-specific effect). This presents an understudied source of bias that potentially affects many data sets in tree-ring research.In this study, we investigated possible direction-specific growth variability based on an international (10 countries), multi-species (8 species) tree-ring width network encompassing 22 sites. To estimate the effect of direction-specific growth variability on climate-growth relationships, we applied a combination of three methods: An analysis of signal strength differences, a Principal Component Gradient Analysis and a test on the direction-specific differences in correlations between indexed ring-widths series and climate variables.We found no evidence for systematic direction-specific effects on tree radial growth variability in high-pass filtered ring-width series. In addition, direction-specific growth showed only marginal effects on climate-growth correlations. These findings therefore indicate that there is no consistent bias caused by coring direction in data sets used for diverse dendrochronological applications on relatively mesic sites within forests in flat terrain, as were studied here. However, in extremely dry, warm or cold environments, or on steep slopes, and for different life-forms such as shrubs, further research is advisable.     

A 781-year oak tree-ring chronology for the Middle Ages archaeological dating in Maramureș (Eastern Europe)

From 1997 to the present, a sustained project in the Maramureș region in Romania was completed with the construction of a 781-year oak tree-ring chronology. A total of 395 samples from living trees and 429 from archaeological wood were analysed with dendrochronological methods. The study aimed to provide the scientific community with a new oak chronology that could be applied in dendroarchaeology, dendroclimatology and dendroecology studies and also for interpreting past socio-economic events. Furthermore, we studied the number of sapwood rings and the growth pattern for different time periods. The chronology covered the continuous period of A.D. 1236‒2016. From the 824 samples collected, we separated 271 tree-ring series into a new chronology (A.D. 1406–2016), which fulfilled all the criteria necessary to reconstruct past climate and environmental changes. The resulting new tree-ring chronology indicated robust signal series intercorrelation (r = 0.55) and an average mean sensitivity of 0.21. Based on an analysis of the sapwood, we recommend estimating a number between 8 and 32 rings to the date of final ring for 95% confidence range of mean on the for felling in the Maramureș region. Additionally, we observed that the number of sapwood rings was not correlated with altitude or oak tree species.     

Automated 3D tree-ring detection and measurement from X-ray computed tomography

Tree ring analysis is essential to reveal the environmental information encoded in the wood structure. It provides quantitative data on the anatomical structure which can be used, for example, to measure the impact of the fluctuating environment on the tree growth, to support global vegetation models and for the dendrochronological analysis of archaeological wooden artefacts. Currently, several imaging-based methods for tree-ring detection and tree-ring feature estimation exist. However, despite advances in computer vision and edge recognition algorithms, detection of tree-rings is mostly limited to two-dimensional (2D) datasets and performed manually in some cases. This paper describes a new approach to estimate the three-dimensional (3D) structure of tree rings and their width automatically from X-ray computed tomography data. This approach relies on a modified Canny edge detection algorithm, which is capable of detecting fully connected tree-ring edges throughout the image stack. Our results show that this approach performs well on six tree species having conifer, ring-porous and diffuse-porous ring boundary structures. In our study, image denoising proved to be a critical step to achieve accurate results. A major advantage of this procedure is that it requires very little to no user interaction rendering it a reproducible procedure for tree-ring width measurements. As it also provides 3D representations of the ring edges, it also may be used in the future for the inspection of anatomical features.     

Are young trees suitable for climate-growth analysis? A trial with Pinus nigra in the central Apennines treeline

In the context of ecological research, tree-ring analysis often deals with short time series (< 30 years). Their crossdating and averaging can be difficult but crucial to use such data for ecological modelling, multivariate statistics, and climate-growth analysis. Several studies were conducted in the Central Apennines (Italy) on recent encroachment of European black pine (Pinus nigra J.F. Arnold) on treeless areas above the current forestline. Growth of young trees is mainly controlled by endogenous or microclimatic factors making usual dendrochronology methods less applicable and crossdating very difficult or even impossible. The potential ecological information deriving from tree-ring growth in short series is therefore limited by this methodological bias. The aim of this study is to test suitable methods for optimizing the use of short ring series for further analytical use. A dataset of 734 tree-ring series of young European black pines (mean cambial age 15 years) growing at high altitude in 8 sites was used in this analysis. At each site tree-ring series were divided in two groups based on inter-series correlation: the crossdated or selected series (SEL), and non-crossdated or rejected ones (REJ). The following dendrochronological parameters were calculated for SEL and REJ series: mean tree-ring width, mean sensitivity, Gini coefficient, first order autocorrelation, inter-series correlation, and Gleichläufigkeit (GLK). Two methods of pointer years analysis were tested in order to detect years with synchronous growth: i) Normalization in a moving Window (NW) and ii) the RElative growth change method (RE). The two methods were applied to the raw series varying the standard thresholds, in order to detect synchronous growth-years in SEL and REJ group. A sensitivity analysis was included to assess how the threshold choice in the analysis could affect the results obtained. The term “common” was used to indicate years with similar tree growth response. Differences in the detected number of common years within SEL and REJ were obtained using different time windows with the RE and NW methods. The 47 % of all series were classified as SEL, showing more common years than the REJ series. However, a similar result occurred considering all the series together without SEL/REJ discrimination. In general, a significant occurrence of common years could be a tool to select series to be averaged for a site mean chronology. These are preliminary but encouraging results contributing to a more efficient use of the ecological information provided by short time series from young trees.     

The dendrochronological proof of origin of oak churches located in the Czech Republic

Transcarpathian wooden churches started to dilapidate after World War I. To preserve the architectural heritage, five oak churches were transported from the region to the territory of today's Czech Republic. However, an exact date of their construction and origin of wood have not been specified and evidenced in literature. In this study, 63 samples have been collected and processed using standard dendrochronological methods. Three Baroque churches, coming from the Mukachevo district, were absolutely dated thanks to the preserved waney edge or sapwood tree rings to periods 1734–1744, 1753–1755, and 1783–1795. Two other churches, representing Gothic architecture, were transported from a more eastern part of Transcarpathian Ukraine. One of them was dated to the period after 1655 and the other could not be reliably dated using available reference chronologies. The created mean tree-ring width series representing individual churches showed strong correlations with the reference chronologies for Slovakia and northern Romania whereas correlations with the only Ukrainian chronology (Lviv region) were negligible. This could suggest low Transcarpathian tree-ring coherency and may indicate the need to create a dense network of regional tree-ring width chronologies in the regions surrounding the Carpathian Mountains.     

Climatic signal in growth-rings of Copaifera lucens: An endemic species of a Brazilian Atlantic forest hotspot,southeastern Brazil

In this study, we present the first tree-ring chronology for the tropical tree species Copaifera lucens and its climatic signal in southeastern Brazil. Tree-ring width series were compared with local climate indices using a drought index (Standardized Precipitation Evapotranspiration Index —SPEI), in monthly, bi-monthly and four-monthly scales. We also calculated negative pointer years over the time-span of the tree-ring width. The radial growth of C. lucens showed a positive correlation with the SPEI of the current summer and autumn in all the three analyzed time scales, while the negative pointer years matched with drier years. The species was highly sensitive to very low summer precipitation, which may lead to a 49% reduction in growth. We conclude that the long-living C. lucens has a great potential for dendrochronological studies as it shows a marked climatic signal. Our study also reinforces the importance of rainfall in regulating radial growth in tropical forests and sheds light on the local climate influence on tree growth in recent decades.     

Tree-ring growth of Gmelin larch under contrasting local conditions in the north of Central Siberia

While the forest-tundra zone in Siberia, Russia has been dendroclimatologically well-studied in recent decades, much less emphasis has been given to a wide belt of northern taiga larch forests located to the south. In this study, climate and local site conditions are explored to trace their influence on radial growth of Gmelin larch (Larix gmelinii (Rupr.) Rupr.) trees developed on permafrost soils in the northern taiga. Three dendrochronological sites characterized by great differences in thermo-hydrological regime of soils were established along a short (ca. 100 m long) transect: on a river bank (RB), at riparian zone of a stream (RZ) and on a terrace (TER). Comparative analysis of the rate and year-to-year dynamics of tree radial growth among sites revealed considerable difference in both raw and standardized tree-ring width (TRW) chronologies obtained for the RZ site, characterized by shallow soil active layer depth and saturated soils. Results of dendroclimatic analysis indicated that tree-ring growth at all the sites is mostly defined by climatic conditions of a previous year and precipitation has stronger effect on TRW chronologies in comparison to the air temperatures. Remarkably, a great difference in the climatic response of TRW chronologies has been obtained for trees growing within a very short distance from each other. The positive relation of tree-ring growth with precipitation, and negative to temperature was observed in the dry site RB. In contrary, precipitation negatively and temperature positively influenced tree radial growth of larch at the water saturated RZ. Thus, a complicate response of northern Siberian larch forest productivity to the possible climate changes is expected due to great mosaic of site conditions and variability of environmental factors controlling tree-ring growth at different sites. Our study demonstrates the new possibilities for the future dendroclimatic research in the region, as various climatic parameters can be reconstructed from tree-ring chronologies obtained for different sites.     

Can We Use Tree Rings of Black Alder to Reconstruct Lake Levels? A Case Study for the Mecklenburg Lake District,Northeastern Germany

In this study, we explore the potential to reconstruct lake-level (and groundwater) fluctuations from tree-ring chronologies of black alder (Alnus glutinosa L.) for three study lakes in the Mecklenburg Lake District, northeastern Germany. As gauging records for lakes in this region are generally short, long-term reconstructions of lake-level fluctuations could provide valuable information on past hydrological conditions, which, in turn, are useful to assess dynamics of climate and landscape evolution. We selected black alder as our study species as alder typically thrives as riparian vegetation along lakeshores. For the study lakes, we tested whether a regional signal in lake-level fluctuations and in the growth of alder exists that could be used for long-term regional hydrological reconstructions, but found that local (i.e. site-specific) signals in lake level and tree-ring chronologies prevailed. Hence, we built lake/groundwater-level reconstruction models for the three study lakes individually. Two sets of models were considered based on (1) local tree-ring series of black alder, and (2) site-specific Standardized Precipitation Evapotranspiration Indices (SPEI). Although the SPEI-based models performed statistically well, we critically reflect on the reliability of these reconstructions, as SPEI cannot account for human influence. Tree-ring based reconstruction models, on the other hand, performed poor. Combined, our results suggest that, for our study area, long-term regional reconstructions of lake-level fluctuations that consider both recent and ancient (e.g., archaeological) wood of black alder seem extremely challenging, if not impossible.     

Dendrochronological analysis and dating of wooden artefacts from the prehistoric copper mine Kelchalm/Kitzbühel (Austria)

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.     

New dendroarchaeological evidence of water well constructions reveals advanced Early Neolithic craftsman skills

The first European settlements accompanied by crop and livestock farming occurred approximately 7500 years ago. In this agrarian society, wood was one of the most important raw materials, most notably for construction, but only a little is known about wood use and woodworking technology. Hence, archaeological wooden finds are of particular importance. Dendroarchaeological studies combine the analysis of external and internal characteristics of archaeological wood: traces of tools on the wooden surfaces and the shape of timbers provide information about woodworking techniques, the tree rings allow dendrochronological dating and provide a paleoecological archive. In 2015 and 2016, two water wells with wooden linings from the Early Neolithic Period were discovered in the Czech Republic close to the towns of Velim (Bohemia) and Uničov (Moravia). The timbers were excellently preserved under waterlogged conditions. Here, we present a dendroarchaeological study including tree-ring and woodworking analyses. Furthermore, we consider former forest species composition. Overall, 15 lumbers from both wells were successfully dated by dendrochronology. The oaks used for the wells from Velim and Uničov were felled in 5196/5195 BCE and 5093–5085 BCE, respectively. Additionally, the taxa of 1859 wooden fragments, such as charcoals, branches and chips, were wood anatomically identified. The well lining from Velim with a hollowed tree trunk is already known from other Central European locations. In contrast, the construction from Uničov is unique for this period. Until now, the advanced construction design formed by four corner posts with longitudinal grooves and inserted horizontal planks was only known several thousands years later. The Early Neolithic wells from Uničov and Velim are the oldest archaeological discoveries of wooden artefacts in the Czech Republic that have been dendrochronologically dated. The tree-ring width series extend the Czech oak tree-ring width chronology more than 300 years into the past.     

Four levels of patterns in tree-rings: an archaeological approach to dendroecology

This paper introduces a method detailing how tree-ring data from subfossil and archaeological wood can be interpreted in palaeoecological terms. On the basis of a literature review concerning the effects of known impacts on tree growth, an attempt is undertaken to provide a general theoretical framework for structuring and interpreting non-recent data where the ecological context is usually missing. The most important tools are dendrotypology and the systematic analysis of tree-ring patterns on four levels. These levels are: (1) ring-anatomical patterns; (2) impact patterns in ring width series at the single-tree level; (3) stand-dynamic patterns, i.e. patterns in ring width series on a stand-wide level; (4) complex patterns that are made up of consistent combinations of the other three pattern levels with each other or additional information. The distinction of these patterns allows the disentangling of different sources of influence on tree growth, which can also potentially be applied to archaeological wood. Several types of reaction to different categories of impact are defined. On a stand-wide scale, the phases of stand development can be reconstructed by identifying characteristic combinations of events. Thus, the range of possible interpretations can be narrowed down to a few possibilities, and sometimes only one. While the general concept is thought to be applicable to a wider range of regions and ecological settings, the presented discussion focuses on gap-phase dominated lowland forests and anthropogenic stands derived from such, which form the focus of central European dendroarchaeological research.