Tree rings provide information on past growing conditions and tree responses to the environment, from ring width to stable isotope composition. Here we compare basal area increment (BAI) as a growth proxy and intrinsic water use efficiency (iWUE), derived from tree ring δ13C, in their ability to record climatic variability in a temperate-oceanic forest in southwest Germany. Local site conditions allow the comparison of five co-occurring tree species (two angiosperms, three gymnosperms) growing on shallow soils with low water holding capacity. Climate information was sourced from a combination of two widely used gridded datasets. Based on BAI and iWUE measurements for a total of 25 trees and 42 years yielding 1050 tree ring measurements), we found that carbon isotope measurements may offer more explanatory power of historic climate variation, than ring width. This result was consistent across univariate and multivariate models using both raw and detrended response variables. iWUE also had a more consistent relationship to climate than BAI for the five tested species. We suggest that iWUE, by integrating the photosynthesis and stomatal control of water loss, better captures plant-available water and atmospheric demand for evapotranspiration. BAI or ring width captures tree growth in a more integrated way and is influenced by competition, tree size, ontogeny, and species-specific traits. Our results show that the more labor-intensive isotope approach can provide additional insight into past climate conditions that may not be captured by ring width alone.

This study investigates the climate sensitivity and resilience of radial growth in eight coniferous and deciduous tree species in the Vienna Woods, Austria. Using dendrochronological methods, we analyzed tree-ring width data from 63 forest plots to assess growth responses to meteorological variability over the period 1933-2023. Historic climate records were used to develop a water balance model, from which we derived seasonal growth factors. Linear mixed effects models were applied to quantify species-specific relationships between tree-ring width and climatic conditions during the current and preceding two years. Tree-ring width responded not only to climatic conditions of the current growing season but also strongly to those of the previous year. Soil moisture and air temperature emerged as the principal drivers of radial growth, with soil moisture positively and temperature negatively affecting ring width. Climatic conditions during June-July of the current year exerted the strongest impact on ring formation. Using regional climate trends and projected air temperature and precipitation trajectories for Central Europe under RCP4.5 and RCP8.5, we forecast future growing conditions for the region. Both scenarios predict an extended growing season, increased transpiration demand, and heightened drought risk - more pronounced under RCP8.5. However, projected increases in precipitation partly offset the drought risk. By combining historical climate sensitivity of radial increment with future climate projections, we modelled expected tree-ring growth for eight tree species. Most species are predicted to experience notable declines in radial growth, with the strongest reductions in conifers, including European larch (Larix decidua), Norway spruce (Picea abies), Austrian pine (Pinus nigra) and Scots pine (Pinus sylvestris). Deciduous species - Sycamore maple (Acer pseudoplatanus), European beech (Fagus sylvatica), and sessile oak (Quercus petraea) - show moderate declines. In contrast, Turkey oak (Quercus cerris) is projected to increase radial growth under future climate scenarios. These findings suggest that forest management in the Vienna Woods and adjacent regions should prioritize the promotion of warm- and drought-tolerant tree species such as Quercus cerris to enhance forest resilience and sustainability in the face of climate change.

Stradivari's violins represent the pinnacle of classical instrument making, yet the origins of the wood used to construct their soundboards have long remained unclear. By analysing 314 tree-ring series from 284 authenticated instruments, we show that the majority of soundboards were crafted from Norway spruce (Picea abies) that grew at very high elevations during the severe climatic conditions of the Maunder Minimum. Our data reveal that Stradivari frequently used wood from the same tree for multiple instruments and that its sources can be traced to the Eastern Alps. Comparison with 197 reference chronologies indicates that Stradivari's early work drew on diverse and less easily localised sources. During his "golden age" of production from the early eighteenth century onwards, he consistently selected spruce from high-altitude forests in Trentino, Italy, and most likely from the Val di Fiemme in particular. These findings provide the first large-scale dendrochronological evidence for the geographic and environmental origins of Stradivari's wood and offer new insights into both historical instrument making and the interplay between climate, materials, and musical heritage.

Abstract Experimental data were collected from defect-free specimens of 57 wood species in Central Europe, encompassing their structural, physical, chemical characteristics, and mechanical properties. The dataset highlights the complex relationships between physical properties (shrinkage–swelling behavior in three orthotropic directions), chemical composition (holocellulose, lignin, extractive content), structural characteristics (density, fiber length), and mechanical properties (compression, tensile and bending strength, hardness, and impact resistance), emphasizing the need for efficient and interpretable methods to identify their correlations. To address this issue, we developed an importance-driven bottleneck model, by revisiting the concept bottleneck model, which consists of a system of three connected neural networks; auxiliary, input, and output, that collaboratively work to investigate the relationship between the physical, structural, chemical, and mechanical features. The input and output networks are linked by a concept c bottleneck layer, with its features defined by analyzing wood’s structural characteristics and composition via feature importance analysis conducted in the auxiliary network. Density and fiber length were identified as the most important concept c features, yielding testing $$R^2$$ R 2 scores above 0.70 for predicting mechanical properties. Predictive accuracy increased to over 0.85 when a third component, either holocellulose or lignin content, was included in the bottleneck. By adding all five chemical and structural features used in concept c layer, the prediction accuracy was slightly increased. While the importance-driven bottleneck model with three or more concept c features was narrowly outperformed by an end-to-end network using shrinkage–swelling as direct inputs, it offered a superior balance between performance and interpretability. This mathematical strategy, forcing information through a concept bottleneck, creates an interpretable physics-inspired AI framework.

Hybridization in forest tree species often results in superior growth and productivity compared to non-hybridized congeners. Earlier studies suggested that faster growth probably happens at the expense of drought tolerance and comes along with altered wood quality such as a lower wood density. Here, we test these hypotheses by comparing six different hybrid larch crossings (mother: Larix decidua, father: L. japonica or L. gmelnii) against a pure European larch provenance originating from the alpine range in a 27-year old common-garden experiment. We also examined whether the way of propagation (generative from seed vs. vegetative from cuttings) influenced growth performance, survival, drought tolerance or wood properties such as wood density. The trial site was intentionally placed in a warm and dry environment, which is climatically far outside the natural distribution of European larch with frequently occurring drought spells and heatwaves. All hybrid larch crossings showed significantly higher productivity (height growth, dbh) and had equal or even lower mortality rates compared to European larch after nearly three decades of growth. Additionally, wood density was significantly higher in hybrids compared to the slower growing European larch, which was mainly attributable to higher latewood width and latewood proportion in hybrids in years with sufficient precipitation. Hybrid larches had also faster growth recovery after an episode of severe drought which is clearly related to a drought-avoiding strategy rather than a physiological drought resistance. Our results strongly imply that the relationship between carbon-gain potential, drought vulnerability as well as wood properties is more complex than previously thought and that hybrid larch crossings may constitute a valuable and resilient alternative for the restoration of extreme and degraded forest stands in the future.

The branches of deciduous trees are optimised by nature to allow continuous adaptation and response to changing environmental conditions. As a result, the morphology and internal structure of the wood branches are often more variable than in the stem. Quantitatively, branches and stem tops represent 20–50

Soils are a major reservoir for organic carbon (C), with subsoils (> 20-30 cm soil depth) storing most of this C. Predicting the response of deep-soil C to global change remains a critical research priority; yet long-term field observations for forests are scarce. In this study, we assessed decadal C dynamics in mineral soils to 90 cm depth of 62 temperate mature stands of European beech (Fagus sylvatica) in Austria using data from sampling campaigns in 1984, 2012, and 2022. Our results show an increase in C stocks between 0 and 20 cm and a significant decrease in C stocks at 20-50 cm and 50-90 cm soil depth, suggesting substantial C losses from deep soils. These deep soil C losses outweighed the C gain in topsoils, resulting in a soil C loss of -0.44 ± 0.19 Mg C ha-1 year-1 since the 1980s. Organic-rich calcareous soils appeared to be particularly vulnerable to C loss, while soils containing high amounts of iron and manganese were less affected, probably because they stabilize C more effectively. We suggest that changes in regional climate (i.e., warmer and wetter) and factors such as changes in litter inputs and rooting depth may underlie the observed patterns of depth-dependent soil C changes. The estimated soil C loss accounted for 17% of the C accumulated in aboveground biomass over the same period, as determined by dendrochronological analysis, indicating a reduction in the ecosystem's C sink capacity since the 1980s. Our results highlight the importance of including deep-soil C storage in forest ecosystem C cycle assessments, as it plays a key role in the overall ecosystem C balance.

Tree-rings provide the longest available quantitative records of tree and forest growth conditions at a high, annual temporal resolution. Sampling designs of dendroecological studies are typically planned for local representativity, without systematic data collection at a greater spatial scale. The integration of different sampling schemes may, however, facilitate the upscaling of findings conforming the information needs of forest planning. In this study, we test the transferability of statistical models of the climate sensitivity of the radial growth of oaks between two complementing sampling designs and for two consecutive 30-year periods. Tree-ring width datasets are based on (i) single-core samples of 665 trees from the common oak species Quercus petraea and Q. robur collected at 520 stratified "extensive" sampling sites within a forest site classification project in Austria, and (ii) seven "intensive" sampling sites with 15 Q. petraea specimens sampled along two stem radii at each site. Both sampling designs span along a climatic gradient representing the entire climatic range of the species in Austria, approaching also the xeric edge of its distribution. The climate sensitivity of the radial growth, defined as the strongest-on-average correlation with climatic variables, is found to be mainly driven by the climatic water balance both along the climatic gradient and during its change over two consecutive periods of analysis. The performance of the regression models on the complementing testing datasets indicates that the main patterns of climate sensitivity can be well-captured by both sampling schemes. Moreover, the intra-population variability of climate sensitivity at the "intensive" sites was comparable in its magnitude to the variability among the "extensive" sites under similar climatic conditions. Our findings indicate that, in a regional context, the main spatiotemporal patterns of the relationships between the climatic drivers and radial growth allow for space-for-time projections under shifting climatic conditions. However, a better understanding of the intra-population variability and the temporal changes thereof can be decisive for the interpretation of dendroecological findings at different scales. Although linear estimations of the spatiotemporal variations of the climate sensitivity along the shifting climatic gradient are largely descriptive for the scope of this study, potential non-linear effects, especially in relation to the changing frequency and severity of extreme weather events may require special attention.

Globally, forests are increasingly at risk from more frequent droughts, threatening their composition, structure, and functioning. However, growth responses to drought are still unclear for many tree species making predictions of future forest dynamics highly uncertain. In this study, we compare three growth response variables to drought, namely resistance, resilience, and recovery for Abies alba, Alnus glutinosa, Acer pseudoplatanus, Fagus sylvatica, Fraxinus excelsior, Larix decidua, Picea abies, Pinus nigra, Pinus sylvestris, Prunus avium, Pseudotsuga menziesii, Quercus cerris, Quercus petraea and Quercus rubra in the Vienna Woods, Austria, a temperate forest landscape in Central Europe. We quantified species-specific drought tolerance by comparing radial growth during the 1983, 2000, 2003, and 2015 droughts to growth during pre- and post-drought periods. Species were ranked by drought tolerance to identify the most drought-tolerant species using linear mixed models. Our results show that conifer species (excluding P. menziesii) are generally more drought-tolerant than broadleaved species. Species such as L. decidua, Pinus sylvestris and P. avium were the most drought tolerant, while A. pseudoplatanus, Fraxinus excelsior, and P. menziesii were the most susceptible. Fagus sylvatica, the dominant tree species in this ecosystem, ranked only eleventh in drought tolerance among the 14 analyzed species, and exhibited a weaker recovery from the last analyzed drought event compared to all other species except P. menziesii. These results provide critical insights into species-specific drought responses, informing forest management strategies under changing climate conditions.

Drought is a significant global environmental stressor that impacts tree growth and survival, often causing substantial die-offs in temperate forests. Hence, contemporary forest management strategies increasingly aim to transition from spruce-dominated to mixed forest with more climate-resilient species such as oaks. Sessile oak (Quercus petraea (Matt.) Liebl.), a key forest tree species, is widespread across central Europe, but its response to climate extremes, especially individual intraspecific variability, remains poorly understood. In this study, we analysed tree-ring cores from 404 sessile oak trees in Thayatal National park, Austria. We assessed radial growth through tree-ring width and evaluated intrinsic water-use efficiency (iWUE) by analyzing delta 13C in latewood from wet (1987) and dry (1994) years. Further, we investigated the effects of site conditions, specifically light and water status inferred from potential daylight duration and the topographic wetness index (TWI), on key tree characteristics such as diameter at breast height (DBH), height, and the height-to-diameter ratio (HDR). We then examined how these factors affected iWUE and radial growth under wet and dry years, assessing radial growth's resistance, resilience, and recovery. As expected, iWUE was increased and radial growth was decreased during the dry year compared to the wet year, but there was high intraspecific variability. Tree age and size influenced these responses; age positively affected growth during the dry year, followed by decreased drought recovery. Increased daylight duration improved iWUE and reduced growth during the dry year but supported drought recovery. During the dry year, iWUE positively affected growth and resistance to drought. The TWI correlated with increased tree height and DBH but did not affect iWUE and growth responses under extreme years. Our findings suggest promoting mixed-age stands could enhance forest resilience against drought. Moreover, forest management strategies should integrate specific environmental conditions, including light availability and water status, to effectively mitigate impact of climate extremes.

The secondary cell wall is a highly optimised structure and large repository of carbon, making wood an efficient tool for carbon sequestration in long-lasting materials. However, the prospective material use of branch wood is not realised, as natural variability is poorly understood. To address this, we analysed the structural orientation of the secondary cell wall in radial wood strips from branches and stem wood of beech, oak and poplar using X-ray diffraction. Our position-resolved results revealed that the flat branches of beech and oak exhibited greater asymmetry, with the highest microfibril orientation on the upper side, associated with the architectural tree design. Steep branches and poplar samples showed a more uniform, stem-like structure. Herman's orientation factor showed a pith-to-bark trend with the lowest orientation in the pith region, but was interrupted by tension wood regions reaching local extremes, identified as interesting tissue for future material designs due to high cell wall quantity and orientation. Our study advances the understanding of the relationship between cell wall orientation and tree architecture, which can now be determined using non-invasive laser scanning, thus enabling the search for materials that meet certain quality criteria and help to foster the new material use of branch wood.

Silver fir (Abies alba) is a key forest tree species in Central Europe growing most commonly in its mixtures with Fagus sylvatica and Picea abies. It is also an important species to dendrochronology due to its longevity, historic timber utilization, and generally well-synchronized interannual growth series. However, a growing number of dendroecological studies focusing on climate change has left the species relatively underrepresented even compared to its lower abundance as a dominant forest tree species. It is also due to its weaker growth–climate relationship, compared to species growing in more climatically limited (first of all water-limited) environments. In forest sciences, the species has received wide attention during the complex forest decline phase after the late 1970s and during the 1980s, referred to as the “Waldsterben” in the German-speaking countries of Central Europe, highlighting the negative effects of air pollution of that time, particularly in the context of silver fir. In the era of climate change, the species is gaining renewed interest, especially for its further admixing potential to climatically more resilient forest stands.In our study, we have investigated the long-term trends and the interannual climatic signal in the radial growth chronologies from monospecific stands of silver fir at seven sites representing a broad climatic and elevational gradient along the distribution of the species. The measured chronologies reveal an increasing low-frequency growth synchrony, starting with a periodic growth increase at the investigated sites since the 1980s, regardless of tree and stand age. Preliminary correlation results suggest that the water-balance related climatic signal has been introduced or has significantly increased between the periods 1961–1990 and 1991–2020. This has been partly associated with a shift or even clear change of sign in the temperature signal. Significant relationships, yet with varying sign, have been also found with the atmospheric water vapor content at each site.The main research questions aim to focus on the pace and term of this change manifested in the climatic signal, namely (i) whether the growing conditions have changed over longer term or were rather influenced by specific years, (ii) if the change was abrupt or more gradual over time. To answer these questions, different climate data-driven models are fitted to the (detrended) growth series, and the error of the model fit is assessed by shorter windows. The temporal patterns of the change, together with the general growth trends identified, are compared to the climatic trends and the frequency of drier periods since the 1980s, with attention to the timescale of the “Waldsterben” phenomena. The interpretation of the results shall reflect a complex interplay of different drivers of forest conditions during the last decades of the 20th century and the inherent uncertainties thereof. Nevertheless, it can contribute to the dendroecological knowledge of an ecologically and silviculturally important species at the crossroads of past legacies, current and predicted challenges.

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.

With ongoing global warming, increasing water deficits promote physiological stress on forest ecosystems with negative impacts on tree growth, vitality, and survival. How individual tree species will react to increased drought stress is therefore a key research question to address for carbon accounting and the development of climate change mitigation strategies. Recent tree-ring studies have shown that trees at higher latitudes will benefit from warmer temperatures, yet this is likely highly species-dependent and less well-known for more temperate tree species. Using a unique pan-European tree-ring network of 26,430 European beech (Fagus sylvatica L.) trees from 2118 sites, we applied a linear mixed-effects modeling framework to (i) explain variation in climate-dependent growth and (ii) project growth for the near future (2021-2050) across the entire distribution of beech. We modeled the spatial pattern of radial growth responses to annually varying climate as a function of mean climate conditions (mean annual temperature, mean annual climatic water balance, and continentality). Over the calibration period (1952-2011), the model yielded high regional explanatory power (R2 = 0.38-0.72). Considering a moderate climate change scenario (CMIP6 SSP2-4.5), beech growth is projected to decrease in the future across most of its distribution range. In particular, projected growth decreases by 12%-18% (interquartile range) in northwestern Central Europe and by 11%-21% in the Mediterranean region. In contrast, climate-driven growth increases are limited to around 13% of the current occurrence, where the historical mean annual temperature was below ~6°C. More specifically, the model predicts a 3%-24% growth increase in the high-elevation clusters of the Alps and Carpathian Arc. Notably, we find little potential for future growth increases (-10 to +2%) at the poleward leading edge in southern Scandinavia. Because in this region beech growth is found to be primarily water-limited, a northward shift in its distributional range will be constrained by water availability.

Abstract Wooden ceilings were among the earliest wooden constructions in wooden houses, and stone and brick buildings. In Austria, a special type of wooden ceiling is known as the Riemenbalkendecke. In Waidhofen, in the Ybbs region, these constructions are decorated with chip carvings, year numbers, and letters. There has been no systematic study on this type of ceiling in Austria. In this study, all houses in Waidhofen an der Ybbs built before 1900 were surveyed, and their ceiling constructions described. Riemenbalkendecken decorated with chip carvings and moldings appeared in 1465 CE and lasted for almost 300 years. The number of carved years was verified using dendrochronological dating. Different chip carving patterns were identified. The letters on ten ceilings can be attributed to the initials of the house owners at the time the ceiling was installed. None of the chip carvings can be attributed to ornaments that were common at the time. The art of the chip carvings on the wooden ceilings represents a special language of form.

Abstract. Temperature reconstruction was carried out on the basis of a centuries-long dendrochronological scales from Austrian Alps. Chronologies of growth-ring width, maximum density of latewood and stable isotope content of carbon and oxygen were applied for the research. Subfossil wood and living trees originating from the area of Schwarzensee Lake were used for the construction of the chronologies. All measurements were performed with annual resolution. A very good match was found between the results obtained and the meteorological data, making it possible to precisely reconstruct the temperature of the growing season (May–September) over the years 800–2000 CE. The proportion of temperature variance explained by independent variables accounted for 52 % in the period common for the growth-ring chronologies and meteorological data. The statistics calculated during calibration and verification tests indicated that chronologies have high reconstruction skills and that the accuracy of reconstruction is good. Obtained data show the existence of significant cooling in the periods 900–1100 CE, 1275–1325 CE, 1450–1600 CE and 1800–1890 CE and evident warming around the years 1150 CE, 1250 CE, 1325–1425 CE, 1625–1775 CE. The strongest increasing trend in temperature has been observed since the beginning of the 20th century and is clearly indicative of an ongoing climate warming.

Silver fir (Abies alba) is a key forest tree species in Central Europe growing most commonly in its mixtures with Fagus sylvatica and Picea abies. It is also an important species to dendrochronology due to its longevity, historic timber utilization, and generally well-synchronized interannual growth series. However, a growing number of dendroecological studies focusing on climate change has left the species relatively underrepresented even compared to its lower abundance as a dominant forest tree species. It is also due to its weaker growth–climate relationship, compared to species growing in more climatically limited (first of all water-limited) environments. In forest sciences, the species has received wide attention during the complex forest decline phase after the late 1970s and during the 1980s, referred to as the “Waldsterben” in the German-speaking countries of Central Europe, highlighting the negative effects of air pollution of that time, particularly in the context of silver fir. In the era of climate change, the species is gaining renewed interest, especially for its further admixing potential to climatically more resilient forest stands. In our study, we have investigated the long-term trends and the interannual climatic signal in the radial growth chronologies from monospecific stands of silver fir at seven sites representing a broad climatic and elevational gradient along the distribution of the species. The measured chronologies reveal an increasing low-frequency growth synchrony, starting with a periodic growth increase at the investigated sites since the 1980s, regardless of tree and stand age. Preliminary correlation results suggest that the water-balance related climatic signal has been introduced or has significantly increased between the periods 1961–1990 and 1991–2020. This has been partly associated with a shift or even clear change of sign in the temperature signal. Significant relationships, yet with varying sign, have been also found with the atmospheric water vapor content at each site. The main research questions aim to focus on the pace and term of this change manifested in the climatic signal, namely (i) whether the growing conditions have changed over longer term or were rather influenced by specific years, (ii) if the change was abrupt or more gradual over time. To answer these questions, different climate data-driven models are fitted to the (detrended) growth series, and the error of the model fit is assessed by shorter windows. The temporal patterns of the change, together with the general growth trends identified, are compared to the climatic trends and the frequency of drier periods since the 1980s, with attention to the timescale of the “Waldsterben” phenomena. The interpretation of the results shall reflect a complex interplay of different drivers of forest conditions during the last decades of the 20th century and the inherent uncertainties thereof. Nevertheless, it can contribute to the dendroecological knowledge of an ecologically and silviculturally important species at the crossroads of past legacies, current and predicted challenges.

The future performance of the widely abundant European beech (Fagus sylvatica L.) across its ecological amplitude is uncertain. Although beech is considered drought-sensitive and thus negatively affected by drought events, scientific evidence indicating increasing drought vulnerability under climate change on a cross-regional scale remains elusive. While evaluating changes in climate sensitivity of secondary growth offers a promising avenue, studies from productive, closed-canopy forests suffer from knowledge gaps, especially regarding the natural variability of climate sensitivity and how it relates to radial growth as an indicator of tree vitality. Since beech is sensitive to drought, we in this study use a drought index as a climate variable to account for the combined effects of temperature and water availability and explore how the drought sensitivity of secondary growth varies temporally in dependence on growth variability, growth trends, and climatic water availability across the species' ecological amplitude.Our results show that drought sensitivity is highly variable and non-stationary, though consistently higher at dry sites compared to moist sites. Increasing drought sensitivity can largely be explained by increasing climatic aridity, especially as it is exacerbated by climate change and trees' rank progression within forest communities, as (co-)dominant trees are more sensitive to extra-canopy climatic conditions than trees embedded in understories. However, during the driest periods of the 20th century, growth showed clear signs of being decoupled from climate. This may indicate fundamental changes in system behavior and be early-warning signals of decreasing drought tolerance. The multiple significant interaction terms in our model elucidate the complexity of European beech's drought sensitivity, which needs to be taken into consideration when assessing this species' response to climate change.