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The current study is a dendroarchaeological/dendroarchitectural investigation of the remains of a historically important multi-phase building, nicknamed 'Enetiko', located in Nafplio. Timber was used for the floors, the roof, and timber-framed walls of the building. Timber elements were also embedded in masonry. Particularly important are the architraves; ground storey timber lintels on the southern façade. According to prior research, the earliest phase was thought to date to the early 18th century with a later 19th century modification. Therefore, we applied dendrochronology to check whether it represents an early construction phase of the building and to confirm the previously mentioned different phases. Timber examination revealed six tree species and 60% of the 85 samples collected in total were dated. Imported deciduous oaks (Quercus spp.), dated c.1530 or after, represent an early Venetian or Ottoman phase of the building. Turkish origin of oaks suggests Ottoman period. Imported fir, most likely Abies alba, was dated in the 17th and 18th centuries. Black pine (Pinus nigra) from Greece and juniper (Juniperus sp.) from the East were used in interventions of the late 19th and 20th centuries. [ABSTRACT FROM AUTHOR]

Trees provide important ecosystem services such as hillslope stabilization from landslides and rockfall protection, and may also be useful indicators of likelihood of those events in the future. Anatomical changes of tree wood are caused by various physical and biological phenomena. There are several geomorphic processes that change tree‐ring characteristics, including hillslope movement, and if detectable, these changes may be used as bioindicators of terrain surface stability. This type of proxy data is vital to places that lack systematic monitoring infrastructure. In the present study, we have evaluated the effects of a heavy rainfall that happened on 11–13 September 2013 in the Colorado Front Range (CFR), which triggered more than 1300 debris flows. We intensely studied one large debris flow that was triggered in the region and the surrounding trees. We explored potential tree‐based records of hillslope instability including compression wood and the method of eccentricity index of tree rings prior to the 2013 event. In addition, the response index was correlated with daily precipitation totals of the previous and current year in a moving window mode. We also evaluated rockfall patterns to explore the frequency and spatial distribution of tree‐scar‐based records. Our primarily goal was to test the method in dry climate conditions and to reconstruct possible soil instability episodes and rockfalls that led to hillslope degradation and tree mortality. In this study, we aimed to fill a significant knowledge gap on debris flows and rockfalls frequency in a dry montane forest system. We were able to distinguish 5 years of increased response index (>25% of trees recording slope instability): 1955 (30%), 1982 (27%), 2002 (27%), 2006 (31%), and 2009 (26%). A spring and early summer season daily precipitation totals of the previous year and summertime daily precipitation totals of the current year explained part of the response index variability. Significant correlation coefficients were up to 0.27. Almost 30 historical rockfall events were dated but only one coincided with an earthquake. In total 138 scars visible on growing trees were mapped. Some of them were found even 3.1 m above the ground level. We conclude that trees can be effective bioindicators of hillslope instability related to debris flows and rock falling. However, extreme climate events such as heavy rainfall causing a high number of debris flows can be difficult to predict based on the method adopted in the present study. [ABSTRACT FROM AUTHOR]

Aims: Woody plant encroachment is a widespread phenomenon affecting treeless or sparsely treed habitats. We aimed to determine the extent and timing of tree and shrub encroachment into rock barrens of eastern Ontario over the last century, and to assess implications for their ongoing management. Location: Queen's University Biological Station in the Frontenac Arch ecoregion. Methods: We quantified the extent of change in woody vegetation in 290 rock barrens using aerial photography from 1925, 1965, and 2008. Composition and structure of woody plant communities in 10 barrens was subsequently quantified in the field using plot‐based sampling. Cores or cross‐sections were obtained from individuals >1.5 m height and dendrochronological techniques were used to determine their age and identify temporal patterns of any woody encroachment. Results: Aerial photography indicated that the mean proportion of woody plant cover in barrens increased 22.5% from 1925 to 2008. Dendroecological analysis supported this. Few trees were present prior to 1900 and most established since 1960. Fraxinus americana, Juniperus virginiana, and Juniperus communis were the most common woody species colonizing the barrens. Remnants of large Pinus strobus stumps with extensive charring were found in 90% of the sampled barrens at a mean density of 22.6 stumps ha−1. Conclusions: Rock barrens on the Frontenac Arch have changed substantially over the past century; gradually being colonized by trees and shrubs and losing their distinctly open character. Active management — including prescribed fire and mechanical thinning — may be necessary if there is a desire to maintain these barrens and the rare species they support as components of the region's biodiversity. However, identification of a reference state for restoration is complicated by the fact that the structure and composition of these habitats were undoubtedly altered by European land clearance in the 19th century, and that some of these areas likely existed as pine woodlands before that. [ABSTRACT FROM AUTHOR]

Longleaf pine woodlands of the North American Coastal Plain are proposed to be resilient to climate change impacts, but little is known about changes in limiting factors to longleaf pine growth as climate has changed in late 20th century and early 21st century. Moreover, the role that neighborhood trees play in the context of climate change remains largely unexplored. We used static and moving window tree ring and climatic analyses to measure the effects of climate on longleaf pine growth at a site in southwest Georgia, USA. We then performed maximum likelihood analysis to examine the influence of neighboring hardwoods on the response of longleaf pine growth to the joint effects of competition and climate. Analysis of climate data from local stations in southwest Georgia over six decades indicated that mean air temperature decreased until the late 20th century then began to rise, and that the variability of spring and summer precipitation has increased. Tree ring and climate analyses indicated longleaf pine radial growth is sensitive to precipitation and air temperature, and that the strength of correlation of longleaf pine growth to summer air temperature and summer precipitation increased since the 1950s. Likelihood models, which were applied over a shorter (23‐year) period and explicitly incorporated competition, did not support a link between summer temperature and growth but did indicate summer precipitation increased growth. Furthermore, basal area (BA) of neighboring hardwoods was correlated with greater pine growth per millimeter of precipitation. BA of neighboring longleaf pine negatively affected growth of conspecific trees; the presence of hardwoods increased the competitive effect when BA of neighboring pine trees was low (<10 m2 ha−1) but decreased the competitive effect when BA of neighboring pine trees was high (≥10 m2 ha−1). These results suggest that retention or recruitment of hardwood trees when restoring longleaf pine woodlands may contribute to increased ability to withstand dry summers and may help to allay concerns of managers that retention of hardwoods will unduly affect growth of residual mature longleaf pines. [ABSTRACT FROM AUTHOR]

Much is still unknown about the growth and physiological responses of trees to global change at the northern treeline. We combined tree‐ring width data with century‐long stable carbon and oxygen isotope records to investigate growth and physiological responses of white spruce at two treeline sites in the Canadian Arctic to concurrent increases in temperature, atmospheric CO2 concentration (ca), and decline in sea ice extent over the past century. The tree‐ring records were assessed during three periods with contrasting climatic conditions: (a) the early 20th century warming, (b) the 1940–1970 cooling period, and (c) the anthropogenic late 20th century warming period. We found opposing growth trends between the two sites, but similar carbon isotope discrimination (Δ13C) and intrinsic water‐use efficiency (iWUE) trajectories. While tree growth (defined as basal area increment) increased at the site nearer to the Arctic Ocean during the 20th century following the rise in temperature and sea ice loss, growth declined after 1950 at the more interior site. At both sites, Δ13C slightly increased over these periods. However, trees showed a nonlinear response to increased ca, shifting after 1970 from a passive stomatal response (i.e., no changes in iWUE) to an active response (i.e., a moderate ∼12% increase in iWUE). Further, our isotope‐based findings do not support the idea that temperature‐induced drought stress caused the divergent growth trends at our treeline sites. This study thus highlights nonlinear and complex physiological and growth adjustments to concomitant changes in temperature, sea ice extent, and ca over the last century at the northern treeline. Plain Language Summary: In the last decades, Arctic ecosystems have experienced unprecedented warmer temperatures, higher atmospheric carbon dioxide concentrations, and a decline in sea ice extent. However, it is still unknown how these changes in environmental factors have impacted tree populations at their northern distribution limits. Here, we examine how the growth and water‐use efficiency of white spruce trees have changed over the last century in response to warmer temperatures, higher carbon dioxide concentrations, and sea ice decline at two treeline sites in the Canadian Arctic. We found that tree growth increased at the site nearer to the Arctic Ocean during the 20th century following the rise in temperature and sea ice loss, while growth declined after 1950 at the more interior site. At both sites, the water‐use efficiency of trees was stable until 1970. Following the rapid temperature and carbon dioxide increase since the 1970s, trees have become more efficient in using water. The contrasting growth trends found at our study sites highlight complex growth and physiological adjustments of white spruce trees to rapid and simultaneous changes in temperature, sea ice extent, and carbon dioxide concentrations in the Arctic. Key Points: Complex growth and physiological responses of white spruce trees to changes in temperature and sea ice extent inferred from stable isotopesWhite spruce radial growth at Arctic latitudinal treeline decreased at an interior site and increased at a site closer to the Arctic OceanWhite spruce shifted from a passive to an active water‐use efficiency response to rising CO2 concentration over the 20th century [ABSTRACT FROM AUTHOR]

Key message: Beech and pine respond differently to climate change. June precipitation is of particular influence for beech, and February/March temperature for pine. Climate warming exposes forests to increasing abiotic stress, demanding for difficult silvicultural decisions about the right choice of future timber species. Scots pine (Pinus sylvestris) and European beech (Fagus sylvatica) are major timber species in the North German Lowlands, which have suffered from recent hot droughts, thus raising concern about their suitability for future production forests in the region. We investigated the climate sensitivity of tree growth and long-term growth trends of ten paired beech and pine forests along a precipitation gradient in the North German Lowlands with the aim to compare the species' climate sensitivity and to search for species-specific climatic thresholds. In the majority of beech stands, basal area increment (BAI) has lost its positive trend since the 1980s or growth declined since then, while the BAI of pine has continually increased. Long-term change in June precipitation is in the study region a more important determinant of beech growth trends than the amount of MAP, while pine growth is largely dependent on the warmth of February/March. Yet, pine growth is also sensitive to dry mid summers, with sensitivity increasing toward low MAP. Climate sensitivity of growth has significantly declined since the 1980s in beech, while the dominant drought signal of June persisted in pine. We conclude that recent climate change is affecting radial growth of beech and pine differently with both species revealing signs of vulnerability to hot droughts, suggesting for the drier part of the study region the preference of more drought-tolerant hardwood timber species over beech and pine. [ABSTRACT FROM AUTHOR]

Key message: An exceptionally high number of blue rings were formed within and between Scots pine trees from Estonia in 1976: a year that is well known for its outstanding summer heatwave over Western Europe, but its extreme autumnal cooling over Eastern Europe has so far been neglected in scientific literature. 'Blue rings' (BRs) are visual indicators of less lignified cell walls typically formed towards the end of a tree's growing season. Though BRs have been associated with ephemeral surface cooling, often following large volcanic eruptions, the intensity of cold spells necessary to produce BRs, as well as the consistency of their formation within and between trees still remains uncertain. Here, we report an exceptionally high BR occurrence within and between Scots pine (Pinus sylvestris L.) trees at two sites in Estonia, including the first published whole-stem analysis for BRs. Daily meteorological measurements from a nearby station allowed us to investigate the role temperature has played in BR formation since the beginning of the twentieth century. The single year in which BRs were consistently formed within and amongst most trees was 1976. While the summer of 1976 is well known for an exceptional heatwave in Northwest Europe, mean September and October temperatures were remarkably low over Eastern Europe, and 3.8 °C below the 1961–1990 mean at our sites. Our findings contribute to a better eco-physiological interpretation of BRs, and further demonstrate their ability to reveal ephemeral cooling not captured by dendrochronological ring width and latewood density measurements. [ABSTRACT FROM AUTHOR]

Key message: Use of co-occurring species with varying temporal sensitivities to summer soil moisture may be used as a diagnostic to determine summertime drought intensification or amelioration. The use of tree-ring data from co-occurring species with different summertime soil-moisture responses provides an opportunity to evaluate the occurrence and direction of soil-moisture changes. Here, we present a method that compares adjusted latewood growth between longleaf pine (Pinuspalustris Mill.) and chestnut oak (Quercusprinus L.) from 1969 to 2018 in the Uwharrie Mountains of central North Carolina, USA. We found that adjusted latewood sensitivity to soil moisture varied between species with the strongest response in September PDSI for longleaf pine (r = 0.47), and July PDSI for chestnut oak (r = 0.61). Large (> 0.20 or < − 0.20) radial growth differences between species occurred during 22 years of the 50-year study period and were strongly correlated with PDSI differences (r = 0.74, p < 0.001), while the correlation with the whole dataset (r = 0.34, p < 0.05) was less sensitive. Major growth difference years were predominately negative (n = 17), suggesting that this method is more effective at detecting summers with decreasing soil moisture between mid and late summer. Overall, these results indicate that a differential response between species with dissimilar latewood formation periods may provide a means to examine potential intermonthly changes in summertime soil-moisture conditions as opposed to a single proxy value (e.g., anomalously dry, or wet) characterizing the entire summer. [ABSTRACT FROM AUTHOR]

In a complex system of natural and human-caused disturbance, shifting climate, and documented, widespread decline and recovery of red spruce populations prior to and following the United States (US) Clean Air Act and amendments (CAAA)—all within the last century—a better understanding of the potential influence of these disturbances on the climate sensitivity and resiliency of red spruce under projected future conditions is needed. We investigated the potential recovery of annual growth in southeastern US red spruce populations following the CAAA and the influence of this recovery vs. ongoing climate change. Using a recently collected network of red spruce tree-ring data from across the southern Appalachian range, we examined temporal trends in stand-level growth and climate sensitivity in the context of acidic (acid) deposition and recovery and modern climate change. We demonstrated that in recent decades, spruce growth is becoming synchronous and climate sensitive in conjunction with a reduction in acid deposition coupled with changes in climate conditions. The emergence of synchronous growth across sites is a new phenomenon that highlights the potential of and the need for region-wide management. Our results provide a temporal perspective that can aid future management strategies in an era of reduced air pollution and a changing climate. [ABSTRACT FROM AUTHOR]

Western juniper (Juniperus occidentalis Hook.) woodlands have persisted for millennia in semiarid parts of the northern Great Basin, USA, providing critical habitat for plant and animal species. Historical records suggest that the establishment of western juniper is strongly associated with regional climatic variability. For example, the abundance of western juniper pollen and macrofossils measured in lake sediment cores increased rapidly in the mid-1500s, concurrent with a regional increase in winter precipitation. However, little is known about how climatic factors interact with landscape structure to control the spatial distribution of western juniper at fine scales and at lower treelines. We used tree rings to reconstruct a spatially distributed history of establishment for 421 western juniper trees across 130 ha on Horse Ridge in central Oregon. Establishment occurred between 845 and 1961 CE, but most trees established after the mid-1550s. The pronounced sixteenth century pulse of establishment represents a transition from more open wooded shrublands to persistent woodlands and coincides with an increase in cool-season moisture and generally cool summer temperatures. Ancient trees that established before this were limited to certain microsites, suggesting that local topoedaphic conditions influenced juniper woodland demography and distributions, although we could not identify consistent environmental drivers. In the future, warmer and drier growing season conditions and a potential increase in wildfire activity may broadly limit western juniper recruitment and its distribution across the region, but at finer scales landscape features that buffer climate change impacts or provide fire safe niches may serve as refugia. [ABSTRACT FROM AUTHOR]

Summary: Intrinsic water‐use efficiency (iWUE), a key index for carbon and water balance, has been widely estimated from tree‐ring δ13C at annual resolution, but rarely at high‐resolution intraseasonal scale.We estimated high‐resolution iWUE from laser‐ablation δ13C analysis of tree‐rings (iWUEiso) and compared it with iWUE derived from gas exchange (iWUEgas) and eddy covariance (iWUEEC) data for two Pinus sylvestris forests from 2002 to 2019.By carefully timing iWUEiso via modeled tree‐ring growth, iWUEiso aligned well with iWUEgas and iWUEEC at intraseasonal scale. However, year‐to‐year patterns of iWUEgas, iWUEiso, and iWUEEC were different, possibly due to distinct environmental drivers on iWUE across leaf, tree, and ecosystem scales. We quantified the modification of iWUEiso by postphotosynthetic δ13C enrichment from leaf sucrose to tree rings and by nonexplicit inclusion of mesophyll and photorespiration terms in photosynthetic discrimination model, which resulted in overestimation of iWUEiso by up to 11% and 14%, respectively.We thus extended the application of tree‐ring δ13C for iWUE estimates to high‐resolution intraseasonal scale. The comparison of iWUEgas, iWUEiso, and iWUEEC provides important insights into physiological acclimation of trees across leaf, tree, and ecosystem scales under climate change and improves the upscaling of ecological models. [ABSTRACT FROM AUTHOR]

This article examines the archaeological timber remains from HMS Buffalo (built 1813), held in the Mercury Bay Museum, New Zealand, and the preserved hull of Edwin Fox (built 1853), sitting in dry dock in Picton, New Zealand. Both ships were constructed near Calcutta (Kolkata), India. Archaeological recording methodologies included detailed timber recording, dendrochronology, archaeometallurgy, organic resinous analyses, and wood-species and fiber identification. The results are then presented to highlight differences and similarities in resource choices and technological development pertaining to ship-construction elements. This contributes to understanding how shipwrights were adapting to new environments while maintaining their learned knowledge in a 19th-century colonial context. [ABSTRACT FROM AUTHOR]

Multi-year drought and climate change can impact tree growth, especially in California's Mediterranean climate where growing season rainfall is limited or absent. Active forest restoration has the potential to mitigate climate impacts by reducing stand density and conversion towards more resilient species' composition. We used dendrochronology methods to examine climate–growth relationships for coast Douglas-fir (Pseudotsuga menziesii var. menziesii) trees in mixed multiaged stands near the species' natural southern range margin. We found positive correlations of ring width with spring–early summer and prior October precipitation and an evapotranspiration index. Additionally, cooler spring temperature was negatively correlated with growth. We also studied tree resistance, resilience, and recovery from two multi-year drought events. Restoration treatments enhanced resistance and resilience to drought relative to trees growing in untreated plots. We did not detect differences in drought resistance and resilience between two common restoration methods, giving managers options for restoration to lessen drought impacts on tree growth. [ABSTRACT FROM AUTHOR]

In the context of climate change, the stable isotope analysis of tree rings may play a crucial role in deciphering the eco-physiological mechanisms underlying forest decline and dieback phenomena. However, this technique is often considered expensive, time-consuming, and with several methodological constraints. Specifically, milling and transferring the material from jars to vials during the different steps of sample preparation involve risk of contamination among samples and loss of sample material. When dealing with declining trees (i.e., trees affected by loss of vitality with strong percentage of defoliation and reduction in growth) and trees subjected to extreme events or negative pointer years (characterized by extremely narrow ring) the sample preparation is particularly difficult because of scarce amount of wood material. In such a case, pooling rings from several years to achieve the minimum weight of wood is often necessary, thus losing information at the annual resolution. In order to overcome such limitations, we developed a novel protocol for quick and accurate whole-wood pre-processing, testing it on oak tree rings of different widths taken from living trees. The main novelty introduced by our protocol was freezing tree-ring samples at −80 °C and milling multiple samples at a time by using a 24-tube plate. The results showed that our novel simplified protocol significantly reduced the pre-processing time with respect to the standard protocol (12 vs. 284 sec/sample), while achieving the same wood particle size, limiting the loss of wood material and reducing the risk of contamination among samples. [ABSTRACT FROM AUTHOR]

The resin tapping of pine trees in Poland ended in the early 1990s. However, we can still find individual trees, and sometimes larger groups of trees, that were tapped. This study focused on the effect of the mechanical wounding of trees during resin tapping on the growth and climatic sensitivity of pine trees. The study concerned a 160-year-old pine stand in northwestern Poland in which resin tapping was last performed in the 1970s. All the trees had remained standing because of their high quality, which had destined them for seed collection. The stand included both resin-tapped (RT) and non-RT (NRT) trees. Our study was based on a dendrochronological analysis of two signals—annual tree ring widths (TRWs) and their delta blue intensity (DBI). We observed a significant increase in annual TRW after resin tapping had ceased, alongside a decrease in the DBI. The temporal stability in growth response was examined using daily climatic correlations from 1921 to 2021. It was found that the climatic sensitivity of RT and NRT pines was similar. There were differences in only some of the years, most while resin tapping was occurring, and then approximately 20 years after the resin tapping had ceased. However, these were small differences that mainly related to the strength of the correlation. It was also discovered that we can obtain different types of information from the study of TRWs and DBI. [ABSTRACT FROM AUTHOR]

Climate change is expected to lead to higher temperatures in the Mediterranean region of northern California in the Sierra Nevada. Dendroclimatic studies typically focus on large, old trees, but there relatively limited understanding on how climatic sensitivity can vary with trees of different size classes. We collected tree increment cores and compared radial growth responses of small (20.32 to ≤40.64 cm), medium (40.64 to ≤60.96 cm), and large (>60.96 cm) diameter mixed conifer species in the Sierra Nevada to different climate variables (temperature, precipitation, and climate moisture index (CMI)). The most common tree species encountered were white fir (Abies concolor (Gord. & Glend.) Lindl.), followed by sugar pine (Pinus lambertiana Dougl.), ponderosa pine (Pinus ponderosa Dougl. Ex P. & C. Laws), and incense cedar (Calocedrus decurrens (Torr.) Florin). One of the most coherent responses from all diameter groups and across all species was the positive response to increasing minimum winter temperatures. All diameter groups and species also responded positively to precipitation and CMI at some point in the analysis period, which is the seasonal window of April of the prior year to October of the current year of ring formation. Perhaps the most notable difference when comparing the three diameter groups to climate was the higher occurrence of negative responses to the temperature of the previous year from the largest diameter group, as well as the higher number of negative responses to temperature in general. These results suggest that larger trees may be more sensitive to future climate projections compared with smaller trees and they may carry those effects into the next year. The use of dendroclimatology to assess how mixed conifer species in the Sierra Nevada responded to past climate is a key resource that can be used to infer how trees may respond to a future changing climate. [ABSTRACT FROM AUTHOR]

Pandora moths (Coloradia pandora subsp. davisi Barnes and Benjamin) have been observed to reach epidemic populations on the Kaibab Plateau, resulting in relatively small, localized defoliation events of ponderosa (Pinus ponderosa Lawson). We reconstructed the historical pandora moth outbreak regime using tree rings and forest health records to explore how exogenous factors, climate, and fire, are related to outbreak dynamics close to the driest range of ponderosa pine. We collected eight tree-ring chronologies dating back 400 years, geographically dispersed around the plateau, and inferred past outbreaks by comparison with non-host tree-ring chronologies, weather records, and historical observations. Eleven outbreaks were detected between 1744 and the present, many of them occurring at all the sites. Outbreaks were found to be synchronous, typically lasting 10 years at 25-year intervals. Interruption of the frequent fire regime that prevailed prior to 1880 was associated with a shift to shorter, less frequent outbreaks. Dry to wet oscillations in climate were correlated with outbreak initiations. Pandora moth outbreaks appear to have been an intrinsic part of the Kaibab Plateau's forest ecosystems, though more research is needed to understand outbreak effects on the ecosystem and future directions of the moth–host relationship under climate warming. [ABSTRACT FROM AUTHOR]

The article reports the AMS (accelerator mass spectrometry) radiocarbon investigation of the historic Grand Baobab of Mahajanga. The largest African baobab of Madagascar exhibits a cluster structure, which consists of 6 fused ordinary stems and of 3 small binding stems. Two samples were collected from the largest stem and from a primary branch, out of which several tiny segments were extracted and dated by radiocarbon. The oldest dated sample segment had a radiocarbon date of 214 ± 17 BP, which corresponds to a calibrated age of 265 ± 25 calendar years. The dating results indicate that the Grand Baobab of Mahajanga is 275 ± 25 years old. [ABSTRACT FROM AUTHOR]

We compared climate–growth relationships (1956–2013) of two natural pedunculate oak (Quercus robur L.) stands with different water-holding capacities growing at the species distribution limit of the Mediterranean Region in NW Iberia. For this, tree-ring chronologies of earlywood vessel size (separating the first row from the other vessels) and latewood width were obtained. Earlywood traits were coupled to conditions during dormancy, whereby an elevated winter temperature appears to induce a high consumption of carbohydrates, resulting in smaller vessels. This effect was reinforced by waterlogging at the wettest site, whose correlation to winter precipitation was strongly negative. Soil water regimes caused differences between vessel rows, since all earlywood vessels were controlled by winter conditions at the wettest site, but only the first row at the driest one; radial increment was related to water availability during the previous rather than the current season. This confirms our initial hypothesis that oak trees near their southern distribution boundary adopt a conservative strategy, prioritizing reserve storage under limiting conditions during the growing period. We believe that wood formation is highly dependent on the balance between the previous accumulation of carbohydrates and their consumption to maintain both respiration during dormancy and early spring growth. [ABSTRACT FROM AUTHOR]

A dendrochronological investigation was undertaken on subfossil Scots pine (Pinus sylvestris L.) stumps following their discovery during conservation management at Wem Moss, a small (28 ha) former raised mire in Shropshire, UK. Two ring-width chronologies were constructed from 14 of the 17 trees sampled spanning 198 and 208 years, respectively. Whilst dendrochronological dating was not possible, radiocarbon assays provided an estimated age for this mire-rooting woodland of between 3015 and 2505 years cal. BCE, coinciding with the age traditionally associated with the widespread mortality of pine trees throughout much of the UK and Ireland, often referred to as the Pine Decline (ca. 4000 radiocarbon years BP). Placed in a wider geographical context, the Wem Moss pines are located within the lowland Meres and Mosses region, where previous studies on subfossil pine have demonstrated protracted declines in mire-rooting trees. These have included tree mortality significantly post-dating the Pine Decline, especially at larger peatland sites that exceed 5 km2. Such macrofossil evidence for the presence of Scots pine into the late Holocene is supported by continuous Pinus pollen representation at peatland sites in the Welsh Marches (English–Welsh border), suggesting the possible survival of native Scots pine trees in this area up to the present day. The investigation of Wem Moss bog pines and their wider geographical context highlights the incomplete and patchy nature of palaeo-vegetational records and also the need for future genetic research on living Scots pine in possible refugial areas in Britain and Ireland. [ABSTRACT FROM AUTHOR]

In the Mediterranean basin, agriculture and other forms of human land use have shaped the environment since ancient times. Intensive and extensive agricultural systems managed with a few cultured plant populations of improved varieties are a widespread reality in many Mediterranean countries. Despite this, historical cultural landscapes still exist in interior and less intensively managed rural areas. There, ancient fruit tree varieties have survived modern cultivation systems, preserving a unique genetic heritage. In this study, we mapped and characterized 106 living fruit trees of ancient varieties in the Basilicata region of southern Italy. Tree ages were determined through tree ring measurements and radiocarbon analyses. We uncovered some of the oldest scientifically dated fruit trees in the world. The oldest fruit species were olive (max age 680 ± 57 years), mulberry (647 ± 66 years), chestnut (636 ± 66 years), and pear (467 ± 89 years). These patriarchs hold a unique genetic resource; their preservation and genetic maintenance through agamic propagation are now promoted by the Lucan Agency for the Development and Innovation in Agriculture (ALSIA). Each tree also represents a hub for biodiversity conservation in agrarian ecosystems: their large architecture and time persistence guarantee ecological niches and micro-habitats suitable for flora and fauna species of conservation significance. [ABSTRACT FROM AUTHOR]

Dendroclimatology offers the unique opportunity to reconstruct past climate at annual resolution and wood from historical buildings can be used to extend such information back in time up to several millennia. However, the varying and often unclear origin of timbers affects the climate sensitivity of individual tree‐ring samples. Here, we compare tree‐ring width and density of 143 living larch (Larix decidua Mill.) trees at seven sites along an elevational transect from 1400 to 2200 m asl and 99 historical tree‐ring series to parametrize state‐of‐the‐art classification models for the European Alps. To achieve geographical provenance of the historical series, nine different supervised machine learning algorithms are trained and tested in their capability to solve our classification problem. Based on this assessment, we consider a tree‐ring density‐based and a tree‐ring width‐based dataset for model building. For each of these datasets, a general not species‐related model and a larch‐specific model including the cyclic larch budmoth influence are built. From the nine tested machine learning algorithms, Extreme Gradient Boosting showed the best performance. The density‐based models outperform the ring‐width models with the larch‐specific density model reaching the highest skill (f1 score = 0.8). The performance metrics reveal that the larch‐specific density model also performs best within individual sites and particularly in sites above 2000 m asl, which show the highest temperature sensitivities. The application of the specific density model for larch allows the historical series to be assigned with high confidence to a particular elevation within the valley. The procedure can be applied to other provenance studies using multiple tree growth characteristics. The novel approach of building machine learning models based on tree‐ring density features allows to omit a common period between reference and historical data for finding the provenance of relict wood and will therefore help to improve millennium‐length climate reconstructions. [ABSTRACT FROM AUTHOR]

Increasingly severe and prolonged droughts are contributing to tree stress and forest mortality across western North America. However, in many cases, we currently have poor information concerning how drought responses in forests vary in relation to competition, climate, and site and tree characteristics. We used annual tree ring evidence of 13C discrimination (Δ13C) and growth metrics to assess drought resistance and resilience for six conifer species at the intersection of several bioregions in northern California. Within each species' range in northern California, we collected competition and tree characteristics from 270 focal trees across sites that varied from wetter to drier habitat conditions (54 sites). Across sites, all six conifer species weathered the severe 2013–2015 drought with reasonably high resistance and post‐drought resilience. However, we found important differences in drought responses between coastal and montane species based on annual growth and Δ13C metrics. Broadly, the two coastal species showed consistent declines in drought resistance across successive drought years, whereas the four montane species maintained high drought resistance across drought years. More specifically, we found lower Δ13C and growth during drought years in coastal species, suggesting stomatal closure during drought with the potential for vulnerability to carbon depletion during long‐term drought. Conversely, Δ13C and growth were stable in montane species throughout the drought, which may contribute to hydraulic failure under increased drought frequency and/or severity. We also evaluated environmental factors that affect Δ13C using data from before and during the drought. These physiological models were consistent for the two coastal species, with a positive relationship between annual precipitation and Δ13C and a negative relationship between tree density and Δ13C. Conversely, the four montane models illustrated a greater importance of site conditions on drought responses for these species. Our findings show differential risk for drought stress across diverse conifers during severe drought. This work highlights the importance of site and tree characteristics in determining drought responses across cool, annually humid coastal habitats to seasonally dry montane habitats. [ABSTRACT FROM AUTHOR]

In the course of renovating the Estonian Knighthood (Ritterschaft) House in the autumn of 2022, a magnificent find came to light in the ceiling of a first floor room - a figural plafond painting on a canvas attached to the ceiling. This find is sensational since it adds to the number of rare and fragile canvas plafonds, only a few of which survive in Estonia. This article demonstrates how archival research and dendrochronology can work together hand in hand. According to historical documents, this part of the Knighthood House was built around the year 1690, because it was described as nearly finished in the spring of 1691. By applying dendrochronological dating, it was possible to ascertain that the trees that form the main wooden structures were felled after the growing season of 1689 and were used in construction, probably in 1690. The Üxküll family of Vigala manor sold their newly completed town palace to the Knighthood of Estonia in 1694 for unknown reasons. The plafond painting probably originates from the period between those two dates, 1690 and 1694. Thus, the Knighthood House's plafond ceiling is the only firmly dated painting of this kind in Estonian architecture. It originates from an earlier period than most other plafond paintings in Tallinn, which are assessed using stylistic comparison as dating from the period after the Great Northern War, specifically from 1721 to 1760. The nearly 60 m2 plafond is certainly the largest in Estonia. The use of distemper and oil paint techniques together makes this painting remarkable. It is also the only known plafond with more than one painting layer from different periods. At the time of writing, the painting has not yet been exposed to view. Its thematic subject matter and the details of its technical realisation will be revealed only after its restoration. The question of the authorship of the plafond painting also remains unanswered at this stage. The overpainting with Rococo ornamentation covering the original painting can be cautiously associated with the name of the guild painter, Gotthard Holm, who was paid for work done in the Knighthood House in the 1760s. [ABSTRACT FROM AUTHOR]

Abstract In the past century, most eruptions of Steamboat Geyser in Yellowstone National Park's Norris Geyser Basin were mainly clustered in three episodes: 1961–1969, 1982–1984, and ongoing since 2018. These eruptive episodes resulted in extensive disturbance to surrounding trees. To characterize tree response over time as an indicator of geyser activity adjustments to climate variability, aerial and ground images were analyzed to document changes in tree coverage around the geyser since 1954. Radiocarbon dating of silicified tree remnants from within 14 m of the geyser vent was used to examine geyser response to possible variations in decadal to centennial precipitation patterns. We searched for atypical or absent growth rings in cores from live trees in years associated with large geyser eruptions. Photographs indicate that active eruptive phases have adversely affected trees up to 30 m from the vent, primarily in the dominant downwind direction. Radiocarbon dates indicate that the geyser formed before 1878, in contrast to the birthdate reported in historical documents. Further, the ages of the silicified trees cluster within three episodes that are temporally correlated with periods of relative drought in the Yellowstone region during the 15th–17th centuries. The discontinuous growth of trees around the geyser suggests that changes in eruptive patterns occur in response to decadal to multidecadal droughts. This inference is supported by the lack of silicified specimens with more than 20 annual rings and by the existence of atypical or missing rings in live trees during periods of extended geyser activity.

Boreal forests are experiencing severe climatic changes that vary widely across the broad geographic distribution of the biome. The changes are greatest near the subarctic treeline where trees often exhibit high climatic sensitivity because climatic conditions approach the limits of their physiological tolerance. Despite the importance of subarctic boreal forests, the lack of field-acquired growth data remains a critical issue that limits the generalization of forest productivity models across the entire boreal biome. Using tree-ring chronologies from remote stands distributed along three latitudinal gradients ranging from 65 to 102°W, we investigated recent trends in black spruce growth and their relationships with recent climate warming near the subarctic treeline in eastern Canada. Our results show a generally positive effect of temperature and a negative effect of precipitation, both indicating that black spruce growth is temperature-limited near its northern range limit. However, we observed a strong gradient in temperature-growth coupling within a small latitudinal gradient (about one degree of latitude), where strong temperature constraints appear limited to the northernmost, coldest stands. Moreover, the positive growth response to temperature decreased from wetter to dryer sites and climate-growth coupling declined over the study period in the driest sites. These results suggest that the growth increase associated with warmer temperature may be limited by reduced precipitation and potential moisture limitation. Lastly, our results suggest that acute climatic events have the potential to induce abrupt shifts in tree climate-growth relationships. Such results indicate that the expected beneficial effect of warming on high latitude tree growth may be less generalized and more complex than previously thought in northeastern Canada, perhaps due to factors other than temperature, which might confound the climate-growth coupling southwards. Thus, our results highlight the need for a better understanding of additional growth drivers in these poorly studied regions and for physiologically informed definitions of acute climatic events, in order to refine broad-scale forest productivity modeling.

In this work, we propose that small wood core samples (≤10 cm length), taken from 0.3 m above the soil, represent an accurate means of correlating forest growth with remote sensing data. Short-term correlations between the Normalized Difference Vegetation Index (NDVI) and tree-ring components of the last three to four decades were tested, using 210 Pinus hartwegii wood cores collected at two locations, Tláloc (TLA) and Jocotitlán (JOCO) in central Mexico. The NDVI time series were generated with the Google Earth Engine (GEE) using Landsat 8 images. Also, seasonal trends in NDVI (e.g., spring, summer, autumn, winter) were analyzed through longitudinal analysis. The results showed more statistically significant dendrochronological indices in TLA than in JOCO, but both locations consistently showed an NDVI decrease in 2018 and 2020, indicating a reduction in vegetation vigor. At the two locations, the minimum and maximum NDVI occurred in April and October, respectively. Seasonal NDVI changes for spring were mainly seen at TLA with a decreasing trend, which may be related to a less defined dry season. The significant correlations (p < 0.05) between tree-ring components and the NDVI occurred in the dry season, indicating that the productivity of a given year is defined by the tree vigor shown in April and May, in the case of TLA, and between January and March, for JOCO. Although the NDVI values of JOCO were higher than those of TLA, tree growth, expressed by tree-ring indices, was lower. Our proposed field method to correlate tree-ring information and the NDVI is reliable and can be used in other coniferous forests.

The long-term effects of climate change and climate extremes have been associated with changes in tree growth and forest productivity worldwide, and dendrochronological analyses are important tools that can be used to investigate the influence of climatic forces on tree growth at a particular site. In this study, a 180-year tree ring width chronology (spanning from 1843 to 2022) of living pine trees (Pinus latteri) in Tak province, northwestern Thailand, was developed. The analysis of the climate–tree growth relationship indicated the influences of the annual total rainfall (r = 0.60, p < 0.001) and annual averaged relative humidity (r = 0.47, p < 0.001) on tree growth in this area. Anomalously high (for example, in 1853, 1984, 2011, and 2018) and low growths (for example, in 1954, 1983, 1992, and 1996) were found. Growth anomalies in the Thai pine in this study were related to changes in abnormal and extreme rainfall (r = 0.94, p < 0.001) and the El Niño Southern Oscillation (ENSO). Our results confirm that rainfall and relative humidity are the main climatic factors regulating the radial growth of Thai pine. This finding could be an important contribution to further research on the effects of climate change and extreme weather events on the vulnerability of tropical and subtropical trees in this region.

Future climate change will exacerbate drought stress in water-limited ecosystems. However, topography can alter the fine-scale climatic and hydrologic conditions that mediate plant response to meteorological drought. Here, with six new valley oak ( Quercus lobata ) tree-ring width chronologies, we assess how topography acts as a mediating factor on tree growth and drought sensitivity. Because valley oaks are known to be highly dependent on subsurface water, we predicted that trees growing in riparian sites would be less sensitive to precipitation variability due to greater access to groundwater. Trees were sampled in the Tehachapi Mountains of California across a landscape gradient of sites ranging from 375–1650 m elevation and across upland (55–69 m mean height above nearest drainage) and riparian (2–6 m mean height above the nearest drainage) hillslope positions. Interannual tree growth patterns and drought sensitivity varied substantially in association with hillslope position and elevation. Valley oak radial growth showed a consistently weaker response to precipitation at riparian sites. The influence of hillslope position on drought sensitivity varied with elevation, such that the riparian buffering effect was weakest at sites higher in the watershed and strengthened, progressively, toward the lower elevation sites with greater climatic water deficit. Upland tree growth exhibited a strong response to high-frequency interannual precipitation variability at the high elevation site, whereas trees at lower elevation upland sites responded more to low-frequency decadal trends in precipitation, possibly reflecting hydrogeological processes by which precipitation feeds groundwater lower in the watershed. Our results are consistent with groundwater-dependence of valley oak and indicate that riparian habitats are the most likely refugia for the species during prolonged drought.

Traditionally, investigations into the climatic response of various tree species have spanned different regions. However, dendrochronological studies within a single region, characterized by minor climatic differences, have received comparatively less attention. Therefore, this study collected 230 tree cores from four prevalent conifer species (P. yunnanensis, A. forrestii, P. likiangensis, and T. dumosa) in the Lugu Lake Wetland Nature Reserve of southwestern China, a region undergoing climate warming and drying. This study employed dendrochronological methods to investigate tree growth–climate static responses, individual tree responses to climate, and dynamic tree–climate interactions. Our findings revealed that as the trend of warming and drying persists, tree growth exhibits an initial increase followed by a subsequent decrease. Dynamic response analyses, along with standardized assessments, indicate that in the early stages of warming, tree growth benefits from elevated temperatures. However, in the later stages of warming, the combined effects of warming and drying become more pronounced. During this phase, the facilitating impact of temperature diminishes, while the controlling influence of moisture conditions intensifies. Looking ahead, with the ongoing intensification of warming and drying, tree growth in the region is anticipated to become increasingly reliant on the water supply. This shift may lead to the decline or mortality of tree species intolerant to drought, such as T. dumosa.

Fire is a disturbance that serves to maintain the diverse mosaic of vegetation in the Eastern Deciduous Forest. However, our ability to reconstruct fire occurrence from hardwood tree scars still lags far behind our expertise in reconstructing fire history from conifers in the western United States. This study examines the fidelity of fire scaring in multiple tree species in the Big Oaks National Wildlife Refuge in Indiana, which is located in the central hardwood region of the Eastern Deciduous Forest. All 15 species, except for red oak, showed evidence of past fires, and most samples recorded multiple fire events. No fire scars were recorded in the latewood of the samples. Most of the fires scars occurred in the earlywood (May) suggesting the dormant season fires are likely associated with fires in March to April before the growing season begins. No synchronous fires were recorded across all sites, but fires occurred in 1981, 1982, 1984, 1985, and 1988 across multiple sites. This suggests that these were larger spreading fires. Establishment pulses were documented in association with fire events in 1981, 1984, and 1995, suggesting that fire may benefit the establishment or root sprouting of some hardwood species. Fourteen of the fifteen species that we sampled preserved fire scars, suggesting that the diverse suite of species in the Eastern Deciduous Forest is a viable sampling pool for examining fire history across this forest type.

Determining the spatio-temporal patterns of rockfalls, such as the zonation of hazards and the assessment of associated risks, can be challenging due to poor historical archives. Dendrogeomorphological methods cover this lack of data and provide reliable reconstructions of rockfall activities over several centuries. These methods are based on the signals recorded in the tree rings that are affected by the mechanical impact of falling rock fragments. In this study, we analyzed the spatial and temporal distribution of rockfalls in a 0.19 ha forest area in the Southern Carpathians. We collected 170 samples (100 increment cores and 70 stem discs) from all 40 Picea abies (L.) Karst trees identified in the study area (1 tree/47 m2). This allowed us to date 945 events between 1817 and 2021, which we then compared with available weather records. Our results show the main trajectory of falling rock fragments from the source area, as well as significant temporal variations in process activity. These variations correlate only slightly with fluctuations in meteorological parameters. Despite the expected intensification of natural hazards due to climate warming, our study area shows a general trend towards a slight decrease in rockfall activity at present.

Turkey oak (Quercus cerris L.) is a thermophilic oak species that is gaining importance in the context of ongoing climate change because of its better resistance to climatic extremes and drier conditions. Therefore, this article focuses on Turkey oak’s role and growth properties in the coppice forests of Southern Europe (Italy, Bulgaria) compared to similar site conditions in Central Europe (Slovakia, Czechia). The aims are to evaluate the basic dendrometry indicators, stand biodiversity, growth dynamics, and the effect of climatic factors on tree-ring increment on specific site chronologies. We found that the tree density in coppices of 50–60 years varied between 475 and 775 trees ha−1, and the stand volume ranged from 141 to 407 m3 ha−1. The complex stand diversity of all plots ranged from a monotonous to uniform structure. The size of tree-ring growth was closely related to indicators of stand density. The lowest influence of climatic factors on tree-ring growth was found in sites in Italy and the highest in Slovakia. The primary limiting factor for growth was the lack of precipitation during the growing season, especially in June and July. In contrast, temperature had a marginal effect on radial growth compared to precipitation. The radial growth in research plots in Southern Europe goes through longer 6 to 8-year growth cycles, and in Central European sites, it goes through shorter cycles of 2.4 to 4.8 years, which confirms better growth conditions in this region. The studied coppice stands exhibit a stable reaction to climate change. Yet, regarding cyclical growth, the Central European stands benefit from an advantageous climate and grow better than in Southern Europe. As part of the changing environmental conditions, Turkey oak is becoming an important tree species that can achieve high production potential even in drier habitats due to its regeneration characteristic as coppice and may play a critical role in its northerly introduction in Europe.

Dendrochronology is a technique that can be applied as a retrospective monitoring (RM) approach to evaluate the performance of nutrient application in forest ecosystems. Applying the RM approach across operations lacks experimental controls, which may adversely affect accuracy and precision of estimates due to greater mismatches in stand conditions between treated and untreated plots. To test the rigor of the RM approach, we collected increment cores of coastal Douglas fir (Pseudotsuga menziesii var. menziesii) at eight sites of an experiment where stands were fertilized in 1971. First, we tested the approach under ideal conditions by sampling from treated and untreated plots of the experiment. Second, we tested the approach using newly established surrogate control (SC) plots, which differed in ecological site classification from those of the treated plots to understand how robust the approach was to mismatches in conditions between treated and untreated samples. We hypothesized that detrending ring width would mitigate error in responses to nutrient application resulting from mismatches in site classification. Within the experiment, the approach indicated an average increase of 15% (5% to 26%, p < 0.05) growth response to operational doses of urea. Different responses were found when the analysis relied on SC plots. Detrending low-frequency variation in ring widths eliminated differences in results arising, at least in part, to mismatches in site class. However, it also reduced the growth response using the experimental control plots to 10%. Dendrochronology with detrending shows promise in the ability to mitigate variation introduced by mismatches in ecological site classification that may occur in operational monitoring. Based on these results, we see potential to implement RM with operations to evaluate and optimize stand selection criteria.

Species-specific responses of plant intrinsic water-use efficiency (iWUE) to multiple environmental drivers associated with climate change, including soil moisture (θ), vapor pressure deficit (D), and atmospheric CO2 concentration (ca ), are poorly understood. We assessed how the iWUE and growth of several species of deciduous trees that span a gradient of isohydric to anisohydric water-use strategies respond to key environmental drivers (θ, D and ca ). iWUE was calculated for individual tree species using leaf-level gas exchange and tree-ring δ13 C in wood measurements, and for the whole forest using the eddy covariance method. The iWUE of the isohydric species was generally more sensitive to environmental change than the anisohydric species was, and increased significantly with rising D during the periods of water stress. At longer timescales, the influence of ca was pronounced for isohydric tulip poplar but not for others. Trees' physiological responses to changing environmental drivers can be interpreted differently depending on the observational scale. Care should be also taken in interpreting observed or modeled trends in iWUE that do not explicitly account for the influence of D.

Abstract Whitebark pine (Pinus albicaulis Engelm.) has experienced rapid population declines and is listed as threatened under the Endangered Species Act in the United States. Whitebark pine in the Sierra Nevada of California represents the southernmost end of the species' distribution and, like other portions of its range, faces threats from an introduced pathogen, native bark beetles, and a rapidly warming climate. Beyond these chronic stressors, there is also concern about how this species will respond to acute stressors, such as drought. We present patterns of stem growth from 766 large (average diameter at breast height >25 cm), disease‐free whitebark pine across the Sierra Nevada before and during a recent period of drought. We contextualize growth patterns using population genomic diversity and structure from a subset of 327 trees. Sampled whitebark pine generally had positive to neutral stem growth trends from 1970 to 2011, which was positively correlated with minimum temperature and precipitation. Indices of stem growth during drought years (2012 to 2015) relative to a predrought interval were mostly positive to neutral at our sampled sites. Individual tree growth response phenotypes appeared to be linked to genotypic variation in climate‐associated loci, suggesting that some genotypes can take better advantage of local climatic conditions than others. We speculate that reduced snowpack during the 2012 to 2015 drought years may have lengthened the growing season while retaining sufficient moisture to maintain growth at most study sites. Growth responses may differ under future warming, however, particularly if drought severity increases and modifies interactions with pests and pathogens.

Abstract Longleaf pine woodlands of the North American Coastal Plain are proposed to be resilient to climate change impacts, but little is known about changes in limiting factors to longleaf pine growth as climate has changed in late 20th century and early 21st century. Moreover, the role that neighborhood trees play in the context of climate change remains largely unexplored. We used static and moving window tree ring and climatic analyses to measure the effects of climate on longleaf pine growth at a site in southwest Georgia, USA. We then performed maximum likelihood analysis to examine the influence of neighboring hardwoods on the response of longleaf pine growth to the joint effects of competition and climate. Analysis of climate data from local stations in southwest Georgia over six decades indicated that mean air temperature decreased until the late 20th century then began to rise, and that the variability of spring and summer precipitation has increased. Tree ring and climate analyses indicated longleaf pine radial growth is sensitive to precipitation and air temperature, and that the strength of correlation of longleaf pine growth to summer air temperature and summer precipitation increased since the 1950s. Likelihood models, which were applied over a shorter (23‐year) period and explicitly incorporated competition, did not support a link between summer temperature and growth but did indicate summer precipitation increased growth. Furthermore, basal area (BA) of neighboring hardwoods was correlated with greater pine growth per millimeter of precipitation. BA of neighboring longleaf pine negatively affected growth of conspecific trees; the presence of hardwoods increased the competitive effect when BA of neighboring pine trees was low (

Insect outbreaks are proven to harm trees, reducing their biomass accumulation due to the defoliation of leaves during the growing season. Various defoliators are responsible for the formation of extremely narrow tree rings in different tree species. In climate reconstructions based on tree-ring width, such narrow rings are often considered as noise, because their formation is not entirely caused by climatic conditions. Thus, the impact of defoliators should be removed (nullified) for unbiased climate reconstructions. This study mainly describes a statistical approach to disentangle the effects of Larch budmoth(LBM) (Zeiraphera diniana) and climate for an unbiased temperature reconstruction in the Bai-Ma mountain area in Southwest China using Larix potaninii. After applying our new approach, growth-climate relationships improved significantly (p

Tree rings are an ecological indicator, useful for studying the adaptation of trees in a changing environment, especially in the unique habitat of high-elevation cliff forests. The main aim of this study was to characterize tree-ring changes in Stone pine (Pinus cembra L.) growing in the extreme conditions of cliff forests of the Western Carpathians (at elevation 1300–1600 m a.s.l.), in order to reconstruct the growth release pattern and to better understand the influence of climate. The study was based on 104 tree ring series covering a 449-year-long chronology (1561–2009). In the last century, mean annual temperature has increased by +2.0 °C and precipitation has decreased slightly in the Tatras. The growth of stone pine was strongly related to summer temperature of June and July. In the last decades, the negative influence of summer precipitation on tree growth has abated; this may be related to warmer summers and decreasing precipitation. Temperature of the previous autumn, winter, and early spring, which had a significant influence on stone pine growth in the past, is not an important factor now. In the extreme environment of mountain cliffs, the influence of temperature and precipitation on tree growth is not stable over time under changing climate. The current changes in climate seem to promote stone pine and its potential upward elevational shift. The numerous past disturbance events have affected a limited number of trees, suggesting that single individuals have been randomly eliminated from the cliff stands during the last three centuries. Our results highlight the complex pattern of the reaction of stone pine on cliffs to changes in the environment. Swiss stone pine, a long-lived tree species, shows high adaptability for colonization of mountain cliffs and is an excellent object for studying the response of plants to changing climate. Understanding the effect of interactions between climate, disturbances, and the radial growth of trees in extreme environments of cliff forests on different temporal scales (monthly, seasonal, yearly) should increase our knowledge of such ecologically valuable areas.

Abstract Increasingly severe and prolonged droughts are contributing to tree stress and forest mortality across western North America. However, in many cases, we currently have poor information concerning how drought responses in forests vary in relation to competition, climate, and site and tree characteristics. We used annual tree ring evidence of 13C discrimination (Δ13C) and growth metrics to assess drought resistance and resilience for six conifer species at the intersection of several bioregions in northern California. Within each species' range in northern California, we collected competition and tree characteristics from 270 focal trees across sites that varied from wetter to drier habitat conditions (54 sites). Across sites, all six conifer species weathered the severe 2013–2015 drought with reasonably high resistance and post‐drought resilience. However, we found important differences in drought responses between coastal and montane species based on annual growth and Δ13C metrics. Broadly, the two coastal species showed consistent declines in drought resistance across successive drought years, whereas the four montane species maintained high drought resistance across drought years. More specifically, we found lower Δ13C and growth during drought years in coastal species, suggesting stomatal closure during drought with the potential for vulnerability to carbon depletion during long‐term drought. Conversely, Δ13C and growth were stable in montane species throughout the drought, which may contribute to hydraulic failure under increased drought frequency and/or severity. We also evaluated environmental factors that affect Δ13C using data from before and during the drought. These physiological models were consistent for the two coastal species, with a positive relationship between annual precipitation and Δ13C and a negative relationship between tree density and Δ13C. Conversely, the four montane models illustrated a greater importance of site conditions on drought responses for these species. Our findings show differential risk for drought stress across diverse conifers during severe drought. This work highlights the importance of site and tree characteristics in determining drought responses across cool, annually humid coastal habitats to seasonally dry montane habitats.

Abstract Dendroclimatology offers the unique opportunity to reconstruct past climate at annual resolution and wood from historical buildings can be used to extend such information back in time up to several millennia. However, the varying and often unclear origin of timbers affects the climate sensitivity of individual tree‐ring samples. Here, we compare tree‐ring width and density of 143 living larch (Larix decidua Mill.) trees at seven sites along an elevational transect from 1400 to 2200 m asl and 99 historical tree‐ring series to parametrize state‐of‐the‐art classification models for the European Alps. To achieve geographical provenance of the historical series, nine different supervised machine learning algorithms are trained and tested in their capability to solve our classification problem. Based on this assessment, we consider a tree‐ring density‐based and a tree‐ring width‐based dataset for model building. For each of these datasets, a general not species‐related model and a larch‐specific model including the cyclic larch budmoth influence are built. From the nine tested machine learning algorithms, Extreme Gradient Boosting showed the best performance. The density‐based models outperform the ring‐width models with the larch‐specific density model reaching the highest skill (f1 score = 0.8). The performance metrics reveal that the larch‐specific density model also performs best within individual sites and particularly in sites above 2000 m asl, which show the highest temperature sensitivities. The application of the specific density model for larch allows the historical series to be assigned with high confidence to a particular elevation within the valley. The procedure can be applied to other provenance studies using multiple tree growth characteristics. The novel approach of building machine learning models based on tree‐ring density features allows to omit a common period between reference and historical data for finding the provenance of relict wood and will therefore help to improve millennium‐length climate reconstructions.

The science of tropical dendrochronology is now emerging in regions where tree-ring dating had previously not been considered possible. Here, we combine wood anatomical microsectioning techniques and radiocarbon analysis to produce the first tree-ring chronology with verified annual periodicity for a new dendrochronological species, Neltuma alba (commonly known as "algarrobo blanco") in the tropical Andes of Bolivia. First, we generated a preliminary chronology composed of six trees using tradi tional dendrochronological methods (i.e., cross-dating). We then measured the 14C content on nine selected tree rings from two samples and compared them with the Southern Hemisphere (SH) atmospheric 14C curves, covering the period of the bomb 14C peak. We find consistent offsets of 5 and 12 years, respectively, in the calendar dates initially assigned, indicating that several tree rings were missing in the sequence. In order to identify the tree-ring boundaries of the unidentified rings we investigated further by analyzing stem wood microsections to examine anatomical characteristics. These anatomical microsections revealed the presence of very narrow terminal parenchyma defining several tree-ring boundaries within the sapwood, which was not visible in sanded samples under a stereomicroscope. Such newly identified tree rings were consistent with the offsets shown by the radiocarbon analysis and allowed us to correct the calendar dates of the initial chronology. Additional radiocarbon measurements over a new batch of rings of the corrected dated samples resulted in a perfect match between the dendrochronological calendar years and the 14C dating, which is based on good agreement between the tree-ring 14C content and the SH 14C curves. Correlations with prior season precipitation and temperature reveal a strong legacy effect of climate conditions prior to the current Neltuma alba growing season. Overall, our study highlights much potential to complement traditional dendrochronology in tree species with challenging tree-ring boundaries with wood anatomical methods and 14C analyses. Taken together, these approaches confirm that Neltuma alba can be accurately dated and thereby used in climatic and ecological studies in tropical and subtropical South America. [ABSTRACT FROM AUTHOR]

Tree ring information dominates in dendrochronology, climatology, ecology, disaster, and environmental science. This study aims to accurately and rapidly obtain the tree ring information, particularly with the low labor intensity and simple operation. An analysis system was also designed for the tree annual ring information. The electro-mechanical design integrated with the hardware of the system, including a slide table module, a rotary encoder, a stepper motor, a shelf table, a hand wheel, two limiters, an industrial camera, an optical microscope, a computer and components, as well as the control boxes (integrated with self-designed collector and controller circuits). The upper computer software of the system was designed to communicate with the industrial camera, collector, and controller using C# language and OpenCvSharp toolkit. The annual information was then collected, processed, and stored in this case. The position calculation, motor control and image recognition were also utilized to design the image recognition using gray component and gray projection analysis. Two methods were designed for the tree ring information analysis in this system: 1) Electronic micro-position method. The spiral ranging method was utilized to measure the linear displacement of the sliding table using the rotary encoder and the collector. The tree ring line was then observed using the industrial camera instead of the traditional microscope. 2) Graph-motor assisted method. The electronic micro-position method was used to combine image recognition and stepper motor control. A field test was carried out to verify the measured tree ring width, the identified tree ring line, and the performance of the analysis system, compared with the traditional microscopes and optical calibration plate. Taking the Chinese pine, larch, poplar, and birch as the research objects, the wood cores of four tree species were collected as the tree ring samples for testing. The test results showed: firstly, the electronic micro-position method performed a 5.68 μm mean absolute error (MAE) and a 6.31 μm root mean square error (RMSE), whereas, the MAE and RMSE of the graph-motor assisted method was 7.84 and 8.62 μm respectivly, which was fully met the National Standards in China; secondly, the accuracy rates of the identification of tree ring line for Chinese pine, larch, poplar and birch species were 83.3%, 93.7%, 55.0%, and 68.3% respectively, and the average recall rates of identification of tree ring line for the coniferous and broad-leaved species group were 96.4%, and 72.6%, respectively, indicating the better performance to identify the annual ring line; thirdly, the average collection time of each tree ring was 1.58 s for the electronic micro-position method, while 1.24 s was for the graph-motor assisted method, which were about 19% and 36% more efficient than the conventional microscopic positioning method, respectively. In conclusion, the improved system presented strong practicability, high accuracy, high efficiency, low working fatigue, and low cost (less than 10 000 Yuan). Therefore, the information system of tree rings can also be expected to promote broad application prospects in multiple subject areas. [ABSTRACT FROM AUTHOR]

The frequency and intensity of drought events are increasing worldwide, challenging the adaptive capacity of several tree species. Here, we evaluate tree growth patterns and climate sensitivity to precipitation, temperature, and drought in the relict Moroccan fir Abies marocana. We selected two study sites, formerly stated as harboring contrasting A. marocana taxa (A. marocana and A. tazaotana, respectively). For each tree, dendrochronological methods were applied to quantify growth patterns and climate–growth sensitivity. Further, ddRAD-seq was performed on the same trees and close saplings to obtain single nucleotide polymorphisms (SNPs) and related genotype–phenotype associations. Genetic differentiation between the two studied remnant populations of A. marocana was weak. Growth patterns and climate–growth relationships were almost similar at the two sites studied, supporting a negative effect of warming. Growth trends and tree size showed associations with SNPs, although there were no relationships with phenotypes related to climatic sensitivity. We found significant differences in the SNPs subjected to selection in the saplings compared to the old trees, suggesting that relict tree populations might be subjected to genetic differentiation and local adaptation to climate dryness. Our results illustrate the potential of tree rings and genome-wide analysis to improve our understanding of the adaptive capacity of drought-sensitive forests to cope with ongoing climate change. [ABSTRACT FROM AUTHOR]

Dendrochronology (tree-ring analysis) allows us to precisely date and identify the origin of timber from historic contexts. However, reference datasets to determine the origin can include timber of non-local origin. Therefore, we have applied Sr isotopic on timbers from three buildings in Jutland, Denmark, mostly dating from the late 16th and early 17th centuries CE to improve and refine the provenance identification. The dendrochronology suggested that some timbers analysed were imported from the Swedish side of Øresund/Kattegat while others were local, and others again might be from south Norway. By adding the Sr isotopic analysis, a far more detailed interpretation of the origin of these timbers can be presented for non-Danish timbers. In this paper we suggest that Danish ports in the provinces of Halland and Skåne played a major role in the timber trade between the Danish and Swedish parts of the Danish kingdom. For Danish timbers dendroprovenancing proved better than Sr isotopic analysis. Furthermore, a small number of Sr isotopic analyses were performed to contribute to the base-line along the Göta-river in Southern-Sweden. [ABSTRACT FROM AUTHOR]

Climate warming at high latitudes has contributed to the growing interest in shrub tree-ring analysis. Shrub architecture presents new challenges for dendrochronology, such as the seemingly lower and inconsistent climatic sensitivity of stems vs. root collars. Shrub stems may thus be considered as sub-optimal to study climate–growth relationships. In this paper, we propose that the lower climatic sensitivity of stems could be caused by the use of unsuitable detrending methods for chronologies spanning decades rather than centuries. We hypothesize that the conversion of the ring width (RW) to basal area increment (BAI) is better suited than traditional detrending methods to removing age/size-related trends without removing multi-decadal climate signals. Using stem and root collar samples collected from three sites in the forest–tundra ecotone of eastern Canada, we compared the climate–growth relationships of these two approaches for stems and root collars using mixed-effects models. The climate sensitivity was, on average, 4.9 and 2.7 times higher with BAI than with detrended (mean-centered) RW chronologies for stems and root collars, respectively. The climatic drivers of radial growth were identical for stems and root collars when using BAI (July temperature and March precipitation), but were inconsistent when using detrended RW series (root collars: July temperature and March precipitation at all sites; stems: April and June temperature, depending on the site). Although the use of BAI showed promising results for studying long-term climate signals in shrub growth chronologies, further studies focusing on different species and locations are needed before the use of BAI can become broadly used in shrub dendrochronology. [ABSTRACT FROM AUTHOR]

The Lagunas de Montebello National Park, Chiapas, Mexico, is one of the most important protected areas in terms of ecology and the provision of ecosystem services in the state of Chiapas; however, it lacks long-term climate information to support comprehensive plans for the conservation of endangered species and ecosystem restoration actions. The objectives of this work were to analyze: (i) the interannual variability of the annual rings of Pinus oocarpa Schiede in the Lagunas de Montebello National Park, as influenced by climate; and (ii) the ocean-atmosphere phenomena influence on both the interannual variability of the total ring-width series. A dendrochronological series of P. oocarpa was built for the period 1857-2018 (162 years), which indicates the presence of extreme hydroclimatic events in the region. Of these, the 1998 drought was a milestone for the management of this natural area due to the high-intensity fires that affected the area and caused unprecedented ecological, social, and economic damage in the site history. The climatic variables with the greatest influence on the annual radial increase of the species are precipitation and maximum temperature in winter-spring, when growth is positively associated with precipitation and negatively associated with temperature, attributed to increases in evapotranspiration. El Niño Southern Oscillation was the phenomenon with the highest correlation with climatic variability and the radial growth of the species, in frequencies of less than five years, although the positive influence of the Atlantic Multidecadal Oscillation was also assessed annually. Global warming, characterized by increasing temperature, threatens the persistence of plant communities in the study area; therefore, knowing its impact on the growth of species of economic importance is essential to support conservation actions. [ABSTRACT FROM AUTHOR]