Some of the most remarkable Neolithic finds encountered in central Europe are wells with a wooden construction. These features provide unusual insights into Neolithic societies, their subsistence strategies and the landscape they inhabited. In the last fifteen years, four Early Neolithic wells out of a total of seven such wells known since the 1970s have been discovered in Czechia. One of them is the well at Ostrov, the wooden construction and sedimentary infill of which have made it possible to study diverse topics by taking a multi-proxy approach using a range of complementary methods. The study presented here compares different periods of the well's existence, examines the carpentry skills of the first farmers, investigates sedimentary processes, reveals details about the use and decline of the well, addresses its location relative to that of the settlement, and reconstructs the environment of the well itself and the surrounding landscape. The water well at Ostrov is a highly unusual find because it probably existed outside of a settlement. The grooved wooden lining used is identical to that of previously investigated wells inside settlements, as are the processes of its use and decline. However, environment-related indicates that the Ostrov well was located in an open landscape with sparse vegetation and was perhaps only used by-passing herdsmen.

Annually resolved and absolutely dated multi-century to multi-millennium tree-ring width (TRW) chronologies are essential for the precise dating of wooden artefacts and for climate reconstruction or dendro-paleoclimate studies. Although Transcarpathian basin region is largely forested and rich in historic buildings, a long and well-replicated oak TRW chronology has so far been lacking. This paper describes how we developed a new composite chronology, determined the number of sapwood rings and assessed positive and negative pointer years in relation to weather and climate extremes. We took 429 oak TRW measurements of 247 samples from living trees and 182 from historical buildings, gathered within Transcarpathian basin. The new Transcarpathian TRW chronology spans the period from 1400 to 2020 CE. The number of sapwood rings ranged from 6 to 23 within 95 % confidence limits. Our results revealed a total of 38 negative and 41 positive pointer years. While CRU gridded meteorological data indicated significant correlations only for positive extremes and high June-July precipitation, documentary data confirmed the importance of wet summers for positive and dry summers for negative pointer years. The new Transcarpathian oak TRW chronology shows a strong growth coherence and will allow historical and archaeological wood artefacts in the eastern Pannonian Plain to be dated. In addition, the use of the chronology for past climate reconstruction is conditioned by improved replication at the transition from recent and relict samples together with its extension further back.

Increasing forest CO2 absorption is ensured by enhanced gross primary production (GPP) which exhibited increasing trends as documented by CO2 flux measurements or by global vegetation models. Considering the simultaneous increase in ecosystem respiration, it is, however, uncertain how the growing GPP imprints in tree stem biomass increase. There is still a certain discrepancy between estimates of forest biomass trends derived from standardized tree-ring series, information acquired from repeated re-measurements of stem biomass at permanent plots, and information derived from vegetation models or flux-tower measurements. Standardization procedures of tree-ring series related to age/size trend removal make this data source unique for the assessment of climate-growth relationships and for climatic reconstruction, however it also increases uncertainty of this data source for biomass trends assessment. Here, we present an approach mimicking repeated data collection at permanent plots based on an extensive data set of tree-ring sites. In this way, we connected two strong benefits of above-mentioned data – reliable age-independent estimates of stem biomass by repeated measurements at permanent plots and a dense network of highly replicated data covering wide environmental gradients provided by tree-ring time series. Our tree-ring network captures core parts of distribution ranges of five main European temperate tree species. Density of tree-ring network is roughly 1 site per 25 km2 of forested area in Central Europe namely Czech Republic (area of 78 000 km2) making this tree-ring network probably densest in the world. We first manipulated original tree-ring data sets by their truncation in 1990 (data set mimicking sample collection in 1990) and then adapt the original data set so that it has similar age structure as the 1990 data set mainly by excluding old age classes (data set 2015) assuring age independency of our data. For both data sets and all sites included, we calculated mean stem diameter at breast height (DBH) of average 100-year old tree based on basal area increments. We then tested for differences in DBH between 1990 and 2015. We found that all species except Pinus sylvestris showed a significant increase in stem dimension as indicated by DBH between 1990 and 2015. The highest DBH increase exhibited Abies alba (+13.5%), followed by Fagus sylvatica (+5.5%), Quercus sp.(+5.2%) and Picea abies (+4.7%). Differences in DBH between 2015 and 1990 were relatively homogenous across environmental gradients suggesting prevailing influence of large-scale factors independent on local conditions. Picea abies and Fagus sylvatica exhibited lesser increase in stem dimensions in colder areas. Furthermore, Picea abies and Quercus sp. showed a significant enhancement of growth at productive sites with fast growing individuals. Quercus also significantly enlarged DBH at locations with more positive trends in SPEI, i.e. those experiencing a trend towards wetter climate. Our results corroborate the pervasive growth acceleration in core region of European temperate forests leading to presence of larger canopy-level trees in current forests than in the past. Increasing stem size makes trees more sensitive to disturbances and potentially leads to their shorter life spans as reported in other studies.

The impact of atmospheric pollution on the growth of European forest tree species, particularly European beech, Silver fir and Norway spruce, is examined in five mesic forests in the Czech Republic. Analyzing of basal area increment (BAI) patterns using linear mixed effect models reveals a complex interplay between atmospheric nitrogen (N) and sulphur (S) deposition, climatic variables and changing CO2 concentrations. Beech BAI responds positively to N deposition (in tandem with air CO2 concentration), with soil phosphorus (P) availability emerging as a significant factor influencing overall growth rates. Fir BAI, on the other hand, was particularly negatively influenced by S deposition, although recent growth acceleration suggests growth resilience in post-pollution period. This fir growth surge likely coincides with stimulation of P acquisition following the decline of acidic pollution. The consequence is the current highest productivity among the studied tree species. The growth dynamics of both conifers were closely linked to the stoichiometric imbalance of phosphorus in needles, indicating the possible sensitivity of exogenous controls on nutrient uptake. Furthermore, spruce BAI was positively linked to calcium availability across sites. Despite enhanced water-use efficiency under elevated CO2, spruce growth is constrained by precipitation deficit and demonstrates weakening resilience to increasing growing season air temperatures. Overall, these findings underscore the intricate relationships between atmospheric pollution, nutrient availability, and climatic factors in shaping the growth dynamics of European forest ecosystems. Thus, incorporating biogeochemical context of nutrient availability is essential for realistic modelling of tree growth in a changing climate.

Better insights into spatio-temporal climate signals are needed to understand more clearly the applicability to palaeoclimatic analysis and dendrochronological dating of the long tree-ring oak chronologies currently being compiled in Eastern Europe. This study investigates the climate sensitivity of two recent oak tree-ring width (TRW) chronologies from Transcarpathian and Ciscarpathian Ukraine and their coherence with 35 oak chronologies from Ukraine, Poland, Slovakia, Romania, and Hungary. The new Transcarpathian chronology consists of 247 TRW series of living trees from 13 sites covering the period 1836-2020, while the new Ciscarpathian chronology consists of 215 TRW series from 13 sites and spans the period 1775-2020. Despite the strong similarity between these two chronologies, their responses to climate differ significantly. Growing-season precipitation and particularly drought (three-month SPEI index) were found to be the primary drivers of oak growth on the border between the Carpathians and the northeastern Pannonian Basin. Spatial correlations of the Transcarpathian chronology show particularly high explained variability in the April-August SPEI index, roughly between 18.5-28.5°E and 45-52°N. In the Ciscarpathian, June precipitation primarily influenced oak radial growth but the spatial correlation was quite low. While the Transcarpathian TRW chronology was strongly correlated with eastern Slovakian and northwestern Romanian chronologies, the Ciscarpathian chronology revealed very low correlations with surrounding chronologies. This study indicates the great dendroarchaeological and palaeoclimatic potential of the Transcarpathian chronology and points to the need to analyse additional living trees from the Ciscarpathian region to understand the spatial variability of oak growth and its climate signal better.

Forests are undergoing increasing risks of drought -induced tree mortality. Species replacement patterns following mortality may have a significant impact on the global carbon cycle. Among major hardwoods, deciduous oaks ( Quercus spp.) are increasingly reported as replacing dying conifers across the Northern Hemisphere. Yet, our knowledge on the growth responses of these oaks to drought is incomplete, especially regarding post -drought legacy effects. The objectives of this study were to determine the occurrence, duration, and magnitude of legacy effects of extreme droughts and how that vary across species, sites, and drought characteristics. The legacy effects were quantified by the deviation of observed from expected radial growth indices in the period 1940 -2016. We used stand -level chronologies from 458 sites and 21 oak species primarily from Europe, north-eastern America, and eastern Asia. We found that legacy effects of droughts could last from 1 to 5 years after the drought and were more prolonged in dry sites. Negative legacy effects (i.e., lower growth than expected) were more prevalent after repetitive droughts in dry sites. The effect of repetitive drought was stronger in Mediterranean oaks especially in Quercus faginea . Species -specific analyses revealed that Q. petraea and Q. macrocarpa from dry sites were more negatively affected by the droughts while growth of several oak species from mesic sites increased during post -drought years. Sites showing positive correlations to winter temperature showed little to no growth depression after drought, whereas sites with a positive correlation to previous summer water balance showed decreased growth. This may indicate that although winter warming favors tree growth during droughts, previous -year summer precipitation may predispose oak trees to current -year extreme droughts. Our results revealed a massive role of repetitive droughts in determining legacy effects and highlighted how growth sensitivity to climate, drought seasonality and species -specific traits drive the legacy effects in deciduous oak species.

The radial growth of trees significantly contributes to climate change mitigation by sequestering carbon into woody biomass. Radial growth trends observed in European temperate forests during the recent period of climate warming vary between growth acceleration due to longer growing seasons and growth declines due to amplified drought stress. Assessing the spatial variation of growth trends is challenging due to the point relevance of available empirical data including forest inventories and tree-ring width chronologies. Here, we used a database of tree-ring width chronologies from 596 sites and spatial models to describe the growth trends of five tree species across the Czech Republic between 1990 and 2018. The resulting map highlights multiple sources of variation in growth trends including differences between species and prominent spatial gradients along elevation, latitude, and longitude. The knowledge of spatially explicit growth trends is essential for the adaptation of the forestry sector to ongoing climate change. Differences among species, regions, and over time shape current growth trends of European temperate forests.Abies alba shows mostly positive growth trends. By contrast, Fagus sylvatica and Picea abies currently decline across most of their species ranges.Growth trends shift from negative to positive with increasing elevation for species covering a broad elevation range.The growth trends of some species follow latitudinal (Abies alba) or longitudinal (Quercus spp.) gradients.The growth trends tend to be more negative in the recent period 2005-2018 compared to the 1990-2005 baseline for most species and regions.

The importance of stable carbon and oxygen isotopes in tree-ring-based climate reconstructions is increasingly recognized, especially in regions where traditional dendrochronological parameters, such as tree-ring width, usually fail. However, the effects of elevation and other site conditions on climate signals in tree-ring stable isotope (TRSI) chronologies remain unclear. Here, we assess the sensitivities to precipitation and drought of tree-ring width (TRW) and δ13C and δ18O TRSI chronologies of 136 living oaks (Quercus spp.) from five different elevational zones between 130 and 630 m asl in eastern Slovakia. Our results show that while the mean δ13C values were stable across the elevational gradient, TRW gradually decreased with increasing elevation, and the mean δ18O values significantly differed between the lower and higher sites. Despite these variations, we observed strong coherency among all the elevation-specific TRW and TRSI chronologies. We also found that mainly mid-May to July precipitation and mid-May to August drought controlled TRW and the δ13C values, whereas the δ18O reflected an overall lower climate signal. Our results show a relatively stable drought signal across the elevational range, with shorter seasonal response windows at higher elevations. Furthermore, our study indicates that carbon TRSI and TRW oak chronologies capture distinct summer drought signals independently of elevation and therefore have a strong paleoclimatic potential across eastern Europe.

The efficiency of water use in plants, a critical ecophysiological parameter closely related to water and carbon cycles, is essential for understanding the interactions between plants and their environment. This study investigates the effects of ongoing climate change and increasing atmospheric CO2 concentration on intrinsic (stomata -based; iWUE) and evaporative (transpiration -based; eWUE) water use efficiency in oak trees along a naturally small altitudinal gradient (130-630 m a.s.l.) of Vihorlat Mountains (eastern Slovakia, Central Europe). To assess changes in iWUE and eWUE values over the past 60 years (1961-2020), stable carbon isotope ratios in latewood cellulose (delta 13Ccell) of annually resolved tree rings were analyzed. Such an approach was sensitive enough to distinguish tree responses to growth environments at different altitudes. Our findings revealed a rising trend in iWUE, particularly in oak trees at low and middle altitudes. However, this increase was negligible at high altitudes. Warmer and drier conditions at lower altitudes likely led to significant stomatal closure and enhanced efficiency in photosynthetic CO2 uptake due to rising CO2 concentration. Conversely, the increasing intracellularto -ambient CO2 ratio (Ci/Ca) at higher altitudes indicated lower efficiency in photosynthetic CO2 uptake. In contrast to iWUE, eWUE showed no increasing trends over the last 60 years. This suggests that the positive impacts of elevated CO2 concentrations and temperature on photosynthesis and stomatal closure are counteracted by the rising atmospheric vapor pressure deficit (VPD). These differences underscore the importance of the correct interpretation of stomata -based and transpiration -based WUEs and highlight the necessity of atmospheric VPD correction when applying tree -ring 613C -derived WUE at ecosystem and global levels.

Sitka spruce has been one of the most planted tree species in Iceland since the mid-twentieth century. Here, we use different dendrochronological methods to identify the controlling climatic factors of its growth and possible changes in their influence over time. We develop annually resolved and absolutely dated measurements of tree-ring width (TRW) from 21 trees and oxygen (delta 18O) and carbon (delta 13C) stable isotopes from six trees to evaluate growth trends and climate sensitivity in Iceland's Hallormsstaour National Forest over the past 54 years (1965-2018). Warmer and wetter summers in the last few decades have resulted in significantly increasing radial growth. While TRW and delta 13C reflect strong July-August temperature signals, with the highest correlation for July, delta 18O is mainly controlled by the temperature in March. The occurrence of negative pointer years in TRW decreases with increasing temperature in July but increases with excessive precipitation in August. Our study shows great continued potential for Sitka spruce cultivation in Iceland.

AbstractEurope is expected to experience major climatic shifts during the 21st century but the impact on agricultural productivity from such changes is uncertain. Here, we combine proxy, instrumental, and model data to assess interannual to multi‐centennial changes in central European agroclimate over the past 2,000 years and projections into the near future. Whereas early 21st century conditions are rare but not fully unprecedented, more than half of the area that was considered highly productive throughout the Common Era in central Europe currently falls outside of that definition. This trend will likely continue as even the most conservative climate projections push central Europe outside the range of past natural variability of changes to agroclimatic zones. Reconstructed extremes prior to the instrumental record align well with contemporary documentary records of societal upheaval. Forecasted changes to the main agroclimatic drivers require substantial adaptation in land use and agricultural management strategies of considerable costs.

Variations in the growth of aboveground biomass compartments such as tree stem and foliage significantly influence the carbon cycle of forest ecosystems. Yet the patterns of climate-driven responses of stem and foliage and their modulating factors remain poorly understood. In this study, we investigate the climatic response of Norway spruce (Picea abies) at 138 sites covering wide spatial and site fertility gradients in temperate forests in Central Europe. To characterize the annual growth rate of stem biomass and seasonal canopy vigor, we used tree-ring chronologies and time-series of NDVI derived from Landsat imagery. We calculated correlations of tree-ring width and NDVI with mean growing season temperature and standardized precipitation evapotranspiration index (SPEI). We evaluated how these climate responses varied with aridity index, soil category, stand age, and topographical factors. The results show that the climate-growth responses of tree rings shift from positive to negative for SPEI and from negative to positive for temperature from dry (warm) to wet (cold) areas. By contrast, NDVI revealed a negative response to temperature across the entire climatic gradient. The negative response of NDVI to temperature likely results from drought effects in warm areas and supporting effects of cloudy conditions on foliage greenness in wet areas. Contrary to NDVI, climate responses of tree rings differed according to stand age and were unaffected by local topographical features and soil conditions. Our findings demonstrate that the decoupling of stem and foliage climatic responses may result from their different climatic limitation along environmental gradients. These results imply that in temperate forest ecosystems, the canopy vigor may show different trends compared to stem growth under ongoing climate change.

Temperate forests are undergoing significant transformations due to the influence of climate change, including varying responses of different tree species to increasing temperature and drought severity. To comprehensively understand the full range of growth responses, representative datasets spanning extensive site and climatic gradients are essential. This study utilizes tree-ring data from 550 sites from the temperate forests of Czechia to assess growth trends of six dominant Central European tree species (European beech, Norway spruce, Scots pine, silver fir, sessile and pedunculate oak) over 1990-2014. By modeling mean growth series for each species and site, and employing principal component analysis, we identified the predominant growth trends. Over the study period, linear growth trends were evident across most sites (56% increasing, 32% decreasing, and 10% neutral). The proportion of sites with stationary positive trends increased from low toward high elevations, whereas the opposite was true for the stationary negative trends. Notably, within the middle range of their distribution (between 500 and 700 m a.s.l.), Norway spruce and European beech exhibited a mix of positive and negative growth trends. While Scots pine growth trends showed no clear elevation-based pattern, silver fir and oaks displayed consistent positive growth trends regardless of site elevation, indicating resilience to the ongoing warming. We demonstrate divergent growth trajectories across space and among species. These findings are particularly important as recent warming has triggered a gradual shift in the elevation range of optimal growth conditions for most tree species and has also led to a decoupling of growth trends between lowlands and mountain areas. As a result, further future shifts in the elevation range and changes in species diversity of European temperate forests can be expected.

Intrinsic water-use efficiency ( iWUE ) of trees is an important component of the Earth’s coupled carbon and water cycles. The causes and consequences of long-term changes in iWUE are, however, still poorly understood due to the complex interplay between biotic and abiotic factors. Inspired by the role calcium (Ca) plays in plant transpiration, we explore possible linkages between tree ring-derived iWUE and Ca availability in five central European forest sites that were affected by acidic air pollution. We show that increasing iWUE was directly modulated by acid air pollution in conjunction with soil Ca concentration. Responses of iWUE to rising atmospheric CO 2 concentrations accelerated across sites where Ca availability decreased due to soil acidity constraints, regardless of nitrogen and phosphorus availability. The observed association between soil acidity, Ca uptake, and transpiration suggests that Ca biogeochemistry has important, yet unrecognized, implications for the plant physiological upregulation of carbon and water cycles.

The Arctic is one of the regions most sensitive to global warming, for which climate and environmental proxy archives are largely insufficient. Arctic driftwood provides a unique resource for research into the circumpolar entanglements of terrestrial, coastal and marine factors and processes – past, present, future. Here, first dendrochronological and wood anatomical insights into 639 Arctic driftwood samples are presented. Samples were collected across northern Norway (n =430) and north-western Iceland (n =209) in 2022. The overall potentials and limitations of Arctic driftwood to improve tree-ring chronologies from the boreal forest, and to reconstruct changes in sea ice extent and ocean current dynamics are discussed. Finally, the role driftwood has possibly played for Arctic settlements in the past hundreds of years is examined.

To enhance our understanding of forest carbon sequestration, climate change mitigation and drought impact on forest ecosystems, the availability of high-resolution annual forest growth maps based on tree-ring width (TRW) would provide a significant advancement to the field. Site-specific characteristics, which can be approximated by high-resolution Earth observation by satellites (EOS), emerge as crucial drivers of forest growth, influencing how climate translates into tree growth. EOS provides information on surface reflectance related to forest characteristics and thus can potentially improve the accuracy of forest growth models based on TRW. Through the modelling of TRW using EOS, climate and topography data, we showed that species-specific models can explain up to 52 % of model variance (Quercus petraea), while combining different species results in relatively poor model performance (R2 = 13 %). The integration of EOS into models based solely on climate and elevation data improved the explained variance by 6 % on average. Leveraging these insights, we successfully generated a map of annual TRW for the year 2021. We employed the area of applicability (AOA) approach to delineate the range in which our models are deemed valid. The calculated AOA for the established forest-type models was 73 % of the study region, indicating robust spatial applicability. Notably, unreliable predictions predominantly occurred in the climate margins of our dataset. In conclusion, our large-scale assessment underscores the efficacy of combining climate, EOS and topographic data to develop robust models for mapping annual TRW. This research not only fills a critical void in the current understanding of forest growth dynamics but also highlights the potential of integrated data sources for comprehensive ecosystem assessments.

Tree-ring stable isotopes are typically measured in latewood cellulose to mitigate potential carry-over effects from previous year storage pools. The isotopic composition of individual tree-ring segments is thought to include considerable intra-annual variability. This sampling strategy may be complicated by steep intra-annual isotope gradients that can rival the inter-annual variability, however. Consistent sampling of latewood material may not always be possible due to low sample availability or high prevalence of narrow rings or low amounts of latewood because of species-specific changes in ring width. Therefore, years that contain samples with higher portions of non-latewood (earlywood) material may influence the final chronology of isotopic variability. Here, we analyze the potential influence that changing earlywood and latewood components of individual tree rings can have on stable carbon and oxygen records from Quercus spp. and Pinus heldreichii chronologies. Analysis of stable isotopes in oak tree rings with varying amounts of latewood show no statistically significant differences in the range of isotopic composition, nor any major differences when considering the same calendric year. Similar results were found for the pine data, when comparing stable isotope measurements with earlywood-to-latewood ratio and maximum density. We argue that this simple approach should be applied to any long-term tree-ring stable isotope record in order to provide a better understanding of the potential biases that could arise from previously recorded intra-annual variability in the wood.

Study region: The Morava River basin, Czech Republic, Danube Basin, Central Europe.Study focus: Hydrological summer extremes represent a prominent natural hazard in Central Europe. River low flows constrain transport and water supply for agriculture, industry and society, and flood events are known to cause material damage and human loss. However, under-standing changes in the frequency and magnitude of hydrological extremes is associated with great uncertainty due to the limited number of gauge observations. Here, we compile a tree-ring network to reconstruct the July-September baseflow variability of the Morava River from 1745 to 2018 CE. An ensemble of reconstructions was produced to assess the impact of calibration period length and trend on the long-term mean of reconstruction estimates. The final estimates represent the first baseflow reconstruction based on tree rings from the European continent. Simulated flows and historical documentation provide quantitative and qualitative validation of estimates prior to the 20th century. New hydrological insights for theregion: The reconstructions indicate an increased variability of warm-season flow during the past 100 years, with the most extreme high and low flows occurring after the start of instrumental observations. When analyzing the entire reconstruction, the negative trend in baseflow displayed by gauges across the basin after 1960 is not unprecedented. We conjecture that even lower flows could likely occur in the future considering that preinstrumental trends were not primarily driven by rising temperature (and the evaporative demand) in contrast to the recent trends.

Starting in the Middle Ages, charcoal production was essential for industrial development, in the manufacture of metals, glass and gunpowder. However, the ancient craft of charcoal burning and other commercial forest activities remain little understood. In this study, we used data from aerial laser scanning (ALS) to identify relic charcoal kilns in deciduous and coniferous forests at three different sites in the Drahany Highlands of the Czech Republic. We applied anatomical, archaeological, dendrochronological and radiocarbon methods to describe and analyse six selected kilns (two from each site) in detail. The ALS method revealed 245 potential relic charcoal kilns, of which 116 were confirmed during a field survey. Five of the six selected kilns dated from the 18th and 19th centuries, which corresponds to the period of greatest charcoal consumption by the region's metallurgical industries. While oak and birch charcoal dominated at one of the three sites under study, fir, oak and beech prevailed at another, while only fir and beech were identified at the third. These results from the anatomical identification of charcoal samples reflect historical as well as potential forest species composition but do not match the current composition. The results of our multidisciplinary research coincide with the peak and decline of charcoal production in the region. Thanks to the clear identification and dating of relic charcoal kilns in this study, an appropriate degree of protection from forest management practices that contribute to their gradual disappearance can be proposed.