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Resilience to drought represents an important focus for trees during climate change, with the aim of predicting the resistance and recovery of species worldwide. Previous studies mainly linked tree growth resilience to plant functional traits that are related to resource acquisition and investment. Here, we investigate a potential link between resilience and the amount of parenchyma tissue in wood, a multifunctional tissue that may provide various physiological benefits to drought‐related mechanisms. We compiled a global tree‐ring data set to evaluate the relationship between growth resistance, resilience or recovery from drought and xylem parenchyma tissue fractions of 50 angiosperms, which was complemented with a local study of nine species from Mt. Tiantong in China. We also assessed the influence of climate and phylogeny on these relationships. We found that growth recovery after drought was positively related to the fractions of total parenchyma locally and globally. This association remained statistically significant when accounting for the effects of climate and phylogeny. No other associations between parenchyma fractions and growth resilience metrics were statistically significant. Our results suggest that drought recovery of angiosperm trees is affected by the amount of parenchyma. Incorporating xylem parenchyma fraction with other traits, such as hydraulic traits, could therefore enhance our comprehension of how various angiosperm tree species will respond to future droughts. Further studies should focus on unravelling the physiological roles of xylem parenchyma fraction. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Based on the need to protect previous ancient trees and the development of dendroclimatology, the use of non-destructive technologies in tree-ring research has gained increasing attention. This study focuses on the ancient Pinus tabulaeformis in Yu Xiang Forest Farm in Henan Province. Firstly, samples were collected using the traditional Increment borers and the Resistograph, a non-destructive method. Subsequently, the peak-valley analysis was used to filter the data obtained by the Resistograph to extract the tree ring width sequence, and the data's accuracy was verified by correlation analysis with tree ring width sequence by the Increment borers. Then, the optimal filtering method and an appropriate comprehensive threshold were determined, and tree ring width and density sequences were successfully extracted. Following that, the growth trend and residual resistance in the measurement process were corrected using linear fitting and Ensemble Empirical Mode Decomposition (EEMD) technology, thereby establishing the tree-ring width and density index series, which were further validated through correlation analysis and t-tests. Finally, analysis of the correlation with climatic factors, identified the main limiting factors for tree growth, and the accuracy of the tree-ring information extracted by the Resistograph was further verified. The results showed that spite of certain differences between the tree-ring width indices extracted by the Resistograph and the Increment borer, they were generally reliable. The radial growth of the ancient P. tabulaeformis in Yu Xiang Forest Farm is primarily influenced by temperature, with the maximum density of the tree rings responding more significantly to the mean maximum temperature, while the minimum density of the tree rings responded more significantly to the mean minimum temperature. These results not only provide a scientific and accurate age for the protection of ancient trees and verify the reliability of the data obtained by the Resistograph, but also facilitate the use of non-destructive technology for in-depth study of ancient trees, therefore enhancing our understanding of how climate change affects tree growth and provide valuable insights for the future protection and management of these ancient trees. [ABSTRACT FROM AUTHOR]

We present new climate field reconstructions (CFR) of tropical Pacific ENSO sea surface temperatures (HadISST) for the boreal winter season using a circum‐Pacific tree‐ring network from known El Niño rainfall impact regions. We use two different CFR methods: Point‐by‐Point Regression (PPR) and reduced‐space Orthogonal Spatial Regression (OSR). Both methods produce reconstructions with high validation skill, but OSR is preferred because it has less spatial noise and is more efficient. Only the leading EOF of the SST field (EOF1) can be skillfully reconstructed by either method; EOF2 does not validate. The success of EOF1 reflects its importance for ENSO rainfall impacts over land; the failure with EOF2 is from the lack of these impacts. EOF1 allows for the reconstruction of many ENSO indices, including the ENSO Longitudinal Index (ELI). We also find evidence in our reconstructions for a recent increase in ENSO activity. Plain Language Summary: Earth's climate is strongly affected by how warm the tropical Pacific Ocean "El Niño" region is. This is especially true for the delivery of rainfall over many parts of the globe. Tree growth can thus be strongly affected by El Niño impacts on rainfall. We use this relationship to reconstruct tropical Pacific sea surface temperatures associated with El Niño over most of the past millennium from a network of annual tree‐ring chronologies located in regions known to be impacted by El Niño rainfall. Only the leading mode of variability in Pacific sea surface temperatures associated with El Niño can be reconstructed well, but it reflects most of the long‐term variability of El Niño exceptionally well. The reconstruction extends back to 1500 with exceptional skill and back to 1100 with acceptable skill. We can thus compare recent El Niño variability, perhaps affected by global warming, with what happened over the previous centuries unaffected by human activity. We find evidence for an increase in El Niño activity, and for an overall warming in recent decades. Key Points: Tree‐ring series from ENSO rainfall impact regions reconstruct tropical Pacific SSTs with high degrees of skill back to 1500 CE and 1100 CETwo very different reconstruction methods produce similar results and each can only reconstruct the leading EOF mode of SST variabilityReconstructions extending back 1100 CE indicate a recent increase in El Niño variability, and overall SST warming in the equatorial Pacific [ABSTRACT FROM AUTHOR]

Key message: This article presents ring width chronologies derived from samples extracted from historical timber buildings in the French central Pyrenees. Two chronologies for fir (Abies alba Mill.) were dated for two periods: 1446–1655 and 1679–1952 AD. These chronologies are suitable for dendroarchaeological and paleoenvironmental studies, or for reconstructing past climates. Dataset access is at https://doi.org/10.48579/PRO/KH6HPC and associated metadata at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/edba546e-3769-4f06-959b-f0d8db7fbcdb. [ABSTRACT FROM AUTHOR]

I outline the "definitional problem" in forest insect outbreak analytics and show how it is related to the "counting problem" in dendroentomology and the "forecasting problem" in forest insect population dynamics, through the ubiquitous presence of non-stationary complex periodicity. Using real-world examples from the spruce budworm (Choristoneura fumiferana Clem.) system, I show that regardless how outbreak patterning is characterized—whether by peak impact, cycle frequency, interval duration, or interval severity—the distribution in pattern attributes appears to be extremely variable, regardless how the data are processed through definitional filters. I show that this extreme variability is an unavoidable and key feature of the system's dynamics and argue that it needs to be viewed as an object of study, instead of a nuisance problem to be swept under the rug. The single biggest opportunity for rapid gains in spruce budworm predictive ecology is determining the environmental and ecological factors that separate high-intensity from low-intensity outbreak cycling. [ABSTRACT FROM AUTHOR]

Hydrologic stress is increasing in Fremont cottonwood (Populus fremontii) forests across the southwestern United States because of increased temperature and streamflow diversion. The spatial variability of this stress is large yet poorly understood. Along the Yampa and Green Rivers in Colorado and Utah, vapour pressure deficit and flow diversions increase downstream. To investigate effects of this gradient on cottonwoods, we measured the percent live canopy and height of randomly selected trees at three sites: Deerlodge Park on the Yampa River (DLP), Island Park on the upper Green (ILP) and Canyonlands National Park on the lower Green (CAN). From these same trees, we took increment cores to understand differences in tree growth in each forest over time. We then related tree metrics to local water availability, streamflow and climatic data. Cottonwoods at CAN were shorter and had lower percent live canopy and growth rate than similarly aged trees upstream. CAN trees that grew higher above the water surface also tended to have lower tree growth, height and live canopy percentage. Furthermore, the correlation between tree growth and maximum vapour pressure deficit showed a much stronger negative shift since 1990 at CAN than at the other sites. All of these differences suggest higher hydrologic stress at CAN, which we attribute to the combined effects of peak flow declines from Flaming Gorge Reservoir, flow diversion and the higher and increasing vapour pressure deficit at CAN. Further research on the variability of hydrologic stress on cottonwoods could help managers anticipate and mitigate the effects of drought stress in these iconic forests. [ABSTRACT FROM AUTHOR]

Copyright of Fire Ecology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

During the sixteenth and seventeenth centuries, the Dutch Republic heavily relied on imported timber for the construction of its cities, dikes, and ships. This timber originated from the Baltic Sea, the German Rhineland, and the "Little East," but primarily from the coastal areas of southern Norway. This article examines the archaeological remains of the timber trade between the Dutch Republic and Norway, emphasizing the study of material culture recovered from archaeological excavations and dendrochronology to complement historical sources from the era. [ABSTRACT FROM AUTHOR]

Introduction: Coastal forests occupy low-lying elevations, typically adjacent to tidal salt marshes. Exposed to increased flooding with sea level rise, coastal forests have retreated as salt marshes advance upslope. Coastal forests likely currently experience periodic tidal flooding, but whether they temporarily accommodate or quickly succumb to rising sea level under changing climatic conditions remains a complex question. Disentangling how tidal flooding and climate affect tree growth is important for gauging which coastal forests are most at risk of loss with increasing sea levels. Methods: Here, dendrochronology was used to study tree growth relative to climate variables and tidal flooding. Specifically, gradients in environmental conditions were compared to species-specific (Pinus taeda, Pinus rigida, Ilex opaca) growth in coastal forests of two estuaries (Delaware and Barnegat Bays). Gradient boosted linear regression, a machine learning approach, was used to investigate tree growth responses across gradients in temperature, precipitation, and tidal water levels. Whether tree ring widths increased or decreased with changes in each parameter was compared to predictions for seasonal climate and mean high water level to identify potential vulnerabilities. Results: These comparisons suggested that climate change as well as increased flood frequency will have mixed, and often non-linear, effects on coastal forests. Variation in responses was observed across sites and within species, supporting that site-specific conditions have a strong influence on coastal forest response to environmental change. Discussion: Site- and species-specific factors will be important considerations for managing coastal forests given increasing tidal flood frequencies and climatic changes. [ABSTRACT FROM AUTHOR]

Correlation coefficients are widely used to identify and quantify climate signals in proxy archives. Significant relationships between tree-ring chronologies and meteorological measurements are typically applied by dendroclimatologists to distinguish between more or less relevant climate variation for ring formation. While insignificant growth-climate correlations are usually found with cold season months, we argue that weak relationships with high summer temperatures not necessarily disprove their importance for xylogenesis. Here, we use maximum latewood density records from ten treeline sites between northern Scandinavia and southern Spain to demonstrate how monthly growth-climate correlations change from narrow unimodal to wide bimodal seasons when vegetation periods become longer and warmer. Statistically meaningful relationships occur when minimum temperatures exceed 'biological zero' at around 5° C. We conclude that the absence of evidence for statistical significance between tree growth and the warmest summer temperatures at Mediterranean sites is no evidence of absence for the physiological importance of high summer temperatures for ring formation. Since correlation should never be confused with causation, statistical values require mechanistic understanding, and different interpretations are needed for insignificant correlations within and outside the growing season. [ABSTRACT FROM AUTHOR]

The quantity and distribution of summer rainfall in Poland is one of the main elements of weather and makes a strong impact on the economy, mostly agriculture, stockbreeding, and forestry and the associated industries. Droughts or heavy rains, occurring increasingly more frequently in summer, are a threat for human activity. This study presents a nearly 500-year-long reconstruction of precipitation in the June–July period for northwestern Poland based on an analysis of tree-ring widths in the native oak species (Quercus spp.) from 24 study plots located in Western Pomerania. Due to the frequent droughts occurring in the last four decades, and due to strong air pollution in the 1960s–1990s, we chose the period 1901–1941 as the calibration period. The performed reconstruction is characterized by a high annual variability in precipitation sums for June and July of the year of the tree-ring formation from 1565 to 2020, with an average rainfall sum for this period equal to 131.7 mm (standard deviation: 28.4 mm). Periods with rainfall shortages in summer occurred in the following years: 1579–1596, 1629–1637, 1650–1655, 1669–1672, 1703–1706, 1739–1748, 1757–1760, 1765–1768, 1808–1811, 1838–1841, 1856–1859, 1958–1961, 1965–1968, 1981–1983, and 2002–2006. Periods with higher than average rainfall in June and July occurred in the following years: 1573–1578, 1605–1609, 1613–1617, 1638–1642, 1694–1698, 1776–1780, 1791–1794, 1828–1831, 1852–1855, 1863–1866, 1877–1879, and 1944–1946. Our reconstruction was verified based on the historical records, available from the XVI century onward. Not all the reconstructed summer precipitation values, however, were confirmed by historical records. Notably, however, the historical data are often incomplete and imprecise. Further, the tree-ring width in the oak depends not only on the precipitation in June and July but also, e.g., on the pluvial conditions late in the previous growth season. [ABSTRACT FROM AUTHOR]

We used cluster analysis on 200-year-old tree-ring chronologies to examine the patterns that emerge from self-organization, driven by environmental heterogeneity, that might drive diversification in ponderosa pine (Pinus ponderosa). We determined the natural patterns on the landscape and then tested these groups against historically separated varieties within this species that could be evidence of diversification. We used 178 previously collected tree-ring chronologies from the western United States that were archived in the International Tree-Ring Databank. We explored a variety of clustering techniques, settling on Ward's clustering with Euclidian distance measures as the most reasonable clustering process. These techniques identified two (p = 0.005) to ten (p = 0.01) potential natural clusters in the ponderosa pine chronologies. No matter the number of clusters, we found that the ponderosa pine varieties ponderosa and benthamiana always cluster together. The variety scopulorum differentiates clearly on its own, but brachyptera is a mix of diverse groups, based on the environmental driving factors that control tree-ring chronology variability. Cluster analysis is a useful tool to examine natural grouping on the landscape using long-term tree-ring chronologies, enabling the researcher to examine the patterns of environmental heterogeneity that should lead to speciation. From this analysis, we suggest that the brachyptera variety should be more varied genetically. [ABSTRACT FROM AUTHOR]

The short and biased observational record of tropical cyclones (TCs) limits scientific understanding of how these destructive storms respond to climate forcing. Paleohurricane records use natural archives (tree rings, coarse‐grained sediment) to reconstruct TC properties (frequency and intensity of rainfall, wind) over the past few hundreds to thousands of years. However, different sensitivities and sampling biases in the various paleohurricane proxies restrict our ability to compile these records into regional or basin‐scale TC estimates. Here we test how well pseudo tree‐ring records of paleohurricanes capture TC rainfall and occurrence. Using a large set of statistically downscaled storms forced with the Max Planck Institute (MPI‐ESM‐P) model as boundary conditions for the past millennium, we generate a 1000‐member ensemble of pseudo tree‐ring records of latewood width from southern Mississippi using a Poisson process‐based random draw. Pseudo records convert synthetic TC rainfall into latewood width using a previously published statistical calibration and seasonal sensitivity. We show that fourth quantile thresholds applied to pseudo latewood data successfully identify years with TC strikes. Comparing pseudo tree‐ring records with pseudo sediment records from the Gulf Coast indicates promise in combining proxies sensitive to TC rainfall with proxies sensitive to storm overwash. Sediment records that are sensitive to lower intensity storms (≥Saffir Simpson Category 1) are more compatible with tree‐ring records, suggesting a need for more of these low intensity threshold records in the Gulf to facilitate future multi‐proxy efforts to reconstruct past TC properties. Key Points: Applying quantile thresholds to latewood tree‐ring records from the Gulf Coast identifies years with at least one tropical cyclone (TC)Low threshold paleohurricane sediment proxies strongly covary with tree ring proxies suggesting promise in future multiproxy comparisonsWe need a wider network of low‐threshold sediment proxies combined with tree ring sites to reconstruct regional TC strikes [ABSTRACT FROM AUTHOR]

Copyright of Canadian Water Resources Journal / Revue Canadienne des Ressources Hydriques is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Key message This article presents ring width chronologies derived from samples extracted from historical timber buildings in the French central Pyrenees. Two chronologies for fir (Abies alba Mill.) were dated for two periods: 1446–1655 and 1679–1952 AD. These chronologies are suitable for dendroarchaeological and paleoenvironmental studies, or for reconstructing past climates. Dataset access is at https://doi.org/10.48579/PRO/KH6HPC and associated metadata at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/edba546e-3769-4f06-959b-f0d8db7fbcdb .

Ecosystem reliance on groundwater, defined here as water stored in the saturated zone deeper than one meter beneath the surface, has been documented in many semi-arid, arid, and seasonally-dry regions around the world. In California, groundwater sustains ecosystems and mitigates mortality during drought. However, the effect of groundwater on carbon cycling still remains largely unresolved. Here we use 20 years of eddy covariance, groundwater, and tree growth measurements to isolate the impact of groundwater on carbon cycling in a semi-arid Mediterranean system in California during the summer dry season. We show that daily ecosystem groundwater use increases under positive groundwater anomalies and is associated with increased carbon assimilation and evapotranspiration rates. Negative groundwater anomalies result in significantly reduced ecosystem groundwater uptake, gross primary productivity, and evapotranspiration, with a simultaneous increase in water use efficiency. Three machine learning algorithms better predict gross primary productivity and tree growth anomalies when trained using groundwater data. These models suggest that groundwater has a unique effect on carbon assimilation and allocation to woody growth. After controlling for the effect of soil moisture, which is often decoupled from groundwater dynamics at the site, wet groundwater anomalies increase canopy carbon assimilation by 179.4 ± 25.7 g C m−2 (17 % of annual gross primary productivity) over the course of the summer season relative to dry groundwater anomalies. Similarly, annual tree growth increases by 0.175 ± 0.035 mm (17.7 % of annual growth) between dry and wet groundwater anomalies, independent of soil moisture dynamics. Our results demonstrate the importance of deep subsurface water resources to carbon assimilation and woody growth in dryland systems, as well as the benefits of collocated, long-term eddy covariance and ancillary datasets to improve understanding of complex ecosystem dynamics.

Abstract Socio‐ecological resilience is the capacity of a system to adapt to changing ecological and social disturbances. Its assessment is extremely important to integrate long‐term management of ecological and social features of natural ecosystems. This is especially true for Sacred Natural Sites, such as sacred forests and groves, where it can reveal the influence of social processes in ecosystem recovery or degradation. Using tree ages determined through dendrochronology and tree population size‐class distributions collected in five sacred forests in Epirus (NW Greece), we explore spatial and temporal dynamics of resilience in a socio‐ecological system, identifying which cultural and social elements characterize resilience in space and time. Our main results show that over past centuries sacred forests in Epirus underwent periods of varying tree establishment rate, depending on the intensity of human activities and historical disturbance events. We also identified strong evidence of the role of the social component (i.e. the church and associated cultural praxis) in determining the spatial extent of the forests' current recovery phase, and thus the overall resilience of the system. Policy implications. Appreciation of the ways sacred forests' ecological resilience is linked to changing socio‐cultural praxis over both temporal and spatial scales is crucial for guiding conservation and restoration strategies. We argue that greater attention should be paid to the role of the social component of socio‐ecological systems and specifically for sacred natural sites that provide both a nucleus of established forest habitat and the conditions necessary for forest recovery and restoration. Read the free Plain Language Summary for this article on the Journal blog.

Simple Summary: Climate change will cause a reduction in the provision of goods and services of Mediterranean forests, including those of stone pine (Pinus pinea), an economically important species. We used a dendrochronological approach to address climate impact on the growth of stone pine natural stands and plantations. Our results indicate that increasingly arid conditions will affect both natural stands and plantations in native and exotic countries. Adaptive management will be essential to ensure the maintenance of the stands and their multifunctionality. Pinus pinea is an important Mediterranean species due to its adaptability and tolerance to aridity and its high-quality pine nuts. Different forest types located in Mediterranean native and non-native environments provide the opportunity to perform comparative studies on the species' response to climate change. The aims of this study were to elucidate growth patterns of the species growing in native and exotic habitats and to analyze its response to climatic fluctuations, particularly drought, in both geographical contexts. Understanding stone pine (Pinus pinea) growth responses to climate variability in native and exotic habitats by comparing natural stands and plantations may provide useful information to plan adequate management under climate change. By doing so, we enhance the understanding of P. pinea's adaptability and provide practical approaches to its sustainable management. In this study, we reconstructed and compared the stem radial growth of seven stone pine stands, two in southern Spain and five in central–southern Chile, growing under different climatic conditions. We quantified the relationships between growth variability and climate variables (total rainfall, mean temperature, and SPEI drought index). Growth was positively correlated with autumn rainfall in plantations and with autumn–winter rainfall in natural stands. Growth was also enhanced by high autumn-to-spring rainfall in the driest Chilean plantation, whereas in the wettest and coolest plantation, such correlation was found in winter and summer. A negative impact of summer temperature was found only in one of the five Chilean plantations and in a Spanish site. The correlation between SPEI and tree-ring width indices showed different patterns between and within countries. Overall, exotic plantations showed lower sensitivity to climate variability than native stands. Therefore, stone pine plantations may be useful to assist in mitigating climate change. [ABSTRACT FROM AUTHOR]

Anticipating future impacts of climate warming and aridification on drylands requires understanding how coexisting woody plant species respond to climate variability. However, we lack knowledge of the growth resilience capacity of Mediterranean shrubs. Do coexisting trees and shrubs differ in their response to climate? Do coexisting shrub species have comparable post‐drought growth resilience?This study was conducted in two Mediterranean shrublands with sparse trees in semi‐arid north‐eastern Spain. We selected sites situated in formerly agricultural or grassland areas in two regions subjected to semi‐arid Mediterranean climate conditions. We sampled six shrubs' species (Juniperus phoenicea, Juniperus oxycedrus, Pistacia lentiscus, Pistacia terebinthus, Rhamnus lycioides and Rhamnus alaternus) and one tree species (Pinus halepensis) to measure their radial growth and to reconstruct their past growth patterns using dendrochronology. We quantified climate–growth relationships of trees and shrubs, as well as the growth resilience capacity after drought events of the six shrubs.Growth patterns differed between species but a prevalent trade‐off between growth and longevity was found. Growth responses to climate were comparable between species but differed between sites. Most species responded positively to precipitation and negatively to temperature. The most negative correlations of growth with drought severity were found at the driest Valcuerna site. Shrubs differed in their resilience capacity. Across sites, species were more resistant and resilient in Alcubierre, the wettest site. The shrubs P. terebinthus and R. lycioides were more resistant and resilient than the rest of species, which required longer growth recovery times and accumulated stronger growth reductions, particularly J. phoenicea.Synthesis. These results highlight the importance of drought as a driver of growth in Mediterranean scrublands. Growth resilience strategies differed between species with junipers being less resilient to drought than other coexisting shrubs. Further research should investigate how this difference in post‐drought resilience is related to functional traits, particularly those related with plant water‐use strategies. [ABSTRACT FROM AUTHOR]

In response to concerns that increment coring with an increment borer might contribute to the dieback of pine trees in Thailand, this research aimed to evaluate the effects of increment coring on the growth of Khasi pine (Pinus kesiya Royle ex Gordon) at Doi Khuntan National Park in northern Thailand. Increment coring is commonly used in dendrochronology, but its impact on tree growth needs to be better understood. This study involved the selection of pine trees of varying diameters, categorizing them into control (uncored) and experimental (cored) groups. Subsequently, data were collected bimonthly from September 2018 to April 2023, except for interruptions from February 2020 to December 2021 due to the COVID-19 pandemic. Tree diameters at breast height were measured, and image analysis was used to monitor the wound healing every two months. A repeated-measures ANOVA was used to compare the growth of cored and uncored groups and the wound healing rates among small-, medium-, and large-tree groups. The growth of cored and uncored Khasi pines within the same and different diameter classes showed no significant differences nor did the wound healing rates. The findings indicated that increment coring had an insignificant impact on the tree growth across all diameter classes, with wounds healing effectively within 14 months. These results support the continued and safe use of increment coring with an increment borer as a non-destructive method for collecting tree-ring and wood samples for climate research and for providing valuable insights into forest management practices. [ABSTRACT FROM AUTHOR]

While snowpack is the main influence on Rio Grande water year streamflow, spring hydroclimate can play a role in moderating this influence in a subset of years. Through an investigation of the relationship between winter snowpack and spring hydroclimate conditions and Rio Grande streamflow, we find low snowpack years with relatively cool, wet springs coincide with slightly above median streamflow in 18% of the years in the instrumental record (1936–2018), while the opposite conditions occur during 24% of years. Over this period, an increase in years with low snowpack/cool wet springs is evident, likely due to a significant decreasing trend in snowpack. We analyze two 15‐century tree‐ring reconstructions to provide long‐term context for the variable relationship between snowpack and spring hydroclimate. Results suggests irregular but quasi‐multidecadal periods when spring conditions may have moderated the effect of a relatively dry winter or reduced the effect of a relatively wet winter. The reconstructions also provide context for the observed trend in the increasing importance of spring conditions over the instrumental period, which appears to be related to both natural climate variability and climate change. In the Rio Grande basin, as mountain snowpack declines due to warming temperatures, spring conditions may be playing an increasingly important role for water resources, at least in the near term. Plain Language Summary: Winter snowpack is the dominant source of water for Rio Grande streamflow. Spring moisture is typically a minor contributor, but in a subset of years, spring conditions can make a difference, ameliorating the impact of a low snowpack or moderating the influence of a high snowpack on water year (October–September) streamflow. Instrumental climate data suggest that spring conditions have become increasingly important with regard to streamflow, concurrent with declining snowpack. Tree‐ring reconstructions of snowpack and spring hydroclimate that extend 1,500 years into the past suggest that both natural climate variability and the influence of warming temperatures on snowpack are likely to be responsible for recent increasing influence of spring conditions on Rio Grande streamflow. Streamflow declines are not yet evident in the headwaters of this river, and the contribution of spring moisture may be part of the reason. However as temperatures continue to warm, spring moisture will be less of a mitigating factor in low snowpack years. Key Points: Snowpack is the main influence on Rio Grande streamflow, but spring can play an important conditioning factor in a subset of yearsSprings are not becoming cooler and wetter but are increasingly more influential to streamflow due to snowpack declinePaleo data reflect the increasing importance of spring and suggest the trend is due to both natural variability and climate warming [ABSTRACT FROM AUTHOR]

The Migazzi palace in Cogolo (Val di Pejo, Trentino, Italy), an important alpine noble residence of medieval origin, was analysed through dendrochronology. The floor and ceiling beams, cladding boards, door lintels, loose timber, and anything that could be dendrochronologically dated were examined. For each room, at least one sample containing the "waney edge" (the last ring before the bark) was found, allowing for precise dating of the different building phases. The results completely changed our knowledge of the palace's history. Initially thought to date back to the 15th century, the tower around which the successive structures were built was dated to the first half of the 14th century (1332). In the space between the floor and the ceiling below, materials used as filler were found, including wooden elements and parts of footwear. The sole of one shoe was dated to 1501, which frames the cultural context of Lombard influence in which the palace flourished. This work has accurately reconstructed the history of the building, demonstrating the potential offered by intensive and widespread dendrochronological sampling. [ABSTRACT FROM AUTHOR]

Key message: Dendroclimatic sensitivity varies by axial position for Sequoiadendron giganteum: negative correlations with June temperature strengthen with height, while positive correlations with snow water are strongest in the lower trunk. Increment cores collected along trunks of mature Sequoiadendron giganteum provide new and updated ring-width chronologies ideal for assessing how height above ground affects sensitivity of radial growth to climatic variation. Chronologies from 61 living trees at nine locations across the geographic distribution span 1973 yr. Analyses of subsets of 18–44 trees reveal that correlations between radial increments and climate (temperature, water availability) vary with axial position. Negative correlations with maximum and minimum June temperature intensify with height and are strongest at the highest position analyzed (60 m above ground). Sensitivity to the hydroclimate variable of April-1 snow water equivalent is stronger at lower trunk positions (10 m) compared to breast height or the upper trunk, and a similar relationship is identified for the standardized precipitation evapotranspiration index using a 12-month window ending in September. Drought-induced low-growth years computed as radial increment relative to the mean of 10 yr before and after are more weakly expressed at breast height compared to higher on the trunk (10–60 m). Analysis of regional upper (maximum core height = 87 m) versus lower trunk (above buttress) chronologies corroborate differing inter-annual correlations with climate depending on height above ground. Accounting for axial variation in dendroclimatic sensitivity can maximize the quality of environmental reconstructions using tree rings and improve biophysical understanding of Sequoiadendron, especially in the context of an increasingly arid climate. [ABSTRACT FROM AUTHOR]

Tree rings are the most widely‐used proxy records for reconstructing Common Era temperatures. Tree‐ring records correlate strongly with temperature on an interannual basis, but studies have found discrepancies between tree rings and climate models on longer timescales, indicating that low‐frequency noise could be prevalent in these archives. Using a large network of temperature‐sensitive tree‐ring records, we partition timeseries variance into a common (i.e., "signal") and non‐climatic (i.e., "noise") component using a frequency‐resolved signal‐to‐noise ratio (SNR) analysis. We find that the availability of stored resources from prior years (i.e., biological "memory") dampens the climate signal at high‐frequencies, and that independent noise reduces the SNR on long timescales. We also find that well‐replicated, millennial‐length records had the strongest common signal across centuries. Our work suggests that low‐frequency noise models are appropriate for use in pseudoproxy experiments, and speaks to the continued value of high‐quality data development as a top priority in dendroclimatology. Plain Language Summary: Tree rings contain valuable information about past variations in Earth's climate, but this information can be obscured by biological influences over tree‐ring formation, particularly when slow changes in climate are integrated with long biological trends. In this study, we measured the strength of the common signal and random noise in a network of tree‐ring records from across the Northern Hemisphere. We find that the emergence of non‐climatic trends decreases the similarity of nearby tree‐ring records to each other on long timescales. Key Points: Temperature‐sensitive tree‐ring records had the highest signal‐to‐noise ratios on an interannual basisNoise showed a positive relationship with timescale indicating presence of independent trends over long time periodsSignal‐to‐noise ratios were highest in tree‐ring density records and in records comprised of a greater number of individual trees [ABSTRACT FROM AUTHOR]

Understanding the dynamics of tree growth is extremely important to develop effective forest conservation and management strategies. Generally, tree growth is well fitted by non-linear regression models. However, it can commonly present problems caused by heteroscedasticity or possible asymmetry in the distribution of residues. An alternative to overcome this problem is quantile regression, which allows estimates at different quantiles, thus generating a more complete mapping of the development of the forest under study. The objective of this study was to compare the adjustment of the non-linear models Logístico, Gompertz, von Bertalanffy, Brody, Chapman-Richards and Weibull using the least squares method and quantile regression, for data on diameter at breast height (DBH) accumulated over the overtime for 56 trees sampled in native forest using a non-destructive technique. The coefficient of determination, the mean absolute deviation and the Akaike information criterion were used to evaluate the quality of the adjustments and the suitability of the models was verified through residual analysis, with the Brody model being the one that best adhered to the data. All computational analysis was carried out using the free software R. [ABSTRACT FROM AUTHOR]

Europe experienced severe heat waves during the last decade, which impacted ecological and societal systems and are likely to increase under projected global warming. A better understanding of pre-industrial warm-season changes is needed to contextualize these recent trends and extremes. Here, we introduce a network of 352 living and relict larch trees (Larix decidua Mill.) from the Matter and Simplon valleys in the Swiss Alps to develop a maximum latewood density (MXD) chronology calibrating at r = 0.8 (p > 0.05, 1901–2017 CE) against May–August temperatures over Western Europe. Machine learning is applied to identify historical wood samples aligning with growth characteristics of sites from elevations above 1900 m asl to extend the modern part of the chronology back to 881 CE. The new Alpine record reveals warmer conditions in the tenth century, followed by an extended cold period during the late Medieval times, a less-pronounced Little Ice Age culminating in the 1810s, and prolonged anthropogenic warming until present. The Samalas eruption likely triggered the coldest reconstructed summer in Western Europe in 1258 CE (-2.32 °C), which is in line with a recently published MXD-based reconstruction from the Spanish Pyrenees. Whereas the new Alpine reconstruction is potentially constrained in the lowest frequency, centennial timescale domain, it overcomes variance biases in existing state-of-the-art reconstructions and sets a new standard in site-control of historical samples and calibration/ verification statistics. [ABSTRACT FROM AUTHOR]

Deformation and failure of the talus slope in the cold region significantly threaten engineered structures. Its driving mechanism of the deformation process is the most challenging issue. In this study, we try to explore these issues using tree ring characteristics. Fifty samples from 21 trees of Pinus densiflora growing on the talus slope in the Huanren area of Northeast China are tested to investigate the characteristics of tree rings and their relation to climate change. The deformation and its driving mechanism of this talus slope are then studied by combining the analysis of tree-ring width and mutation identification with the local meteorological data. The results present that the studied talus slope in Huanren has deformed to varying degrees at least 60 times since 1900. It is reasonable to speculate that the deformation mode of this slope is probably of a long-term and slow type. The local precipitation and seasonal temperature difference are the vital inducing factors of the mutation of tree-ring width and slope deformation. Repeated freezing and thawing are believed to be the driving factors of this talus slope in the cold region. A theoretical model is proposed to capture and predict the deformation of the talus slope. This work presents a new perspective and insight to reveal the deformation and its driving mechanism of similar talus slopes in the cold region. It is of great significance to practical engineering treatment and disaster prevention for this kind of cold region environment. [ABSTRACT FROM AUTHOR]

Disentangling the factors influencing the climate sensitivity of trees is crucial to understanding the susceptibility of forests to climate change. Reducing tree-to-tree competition and mixing tree species are two strategies often promoted to reduce the drought sensitivity of trees, but it is unclear how effective these measures are in different ecosystems. Here, we studied the growth and physiological responses to climate and severe droughts of silver fir and Douglas-fir growing in pure and mixed conditions at three sites in Switzerland. We used tree-ring width data and carbon (δ13C), oxygen (δ18O) and hydrogen (δ2H) stable isotope ratios from tree-ring cellulose to gain novel information on water relations and the physiology of trees in response to drought and how tree species mixture and competition modulate these responses. We found significant differences in isotope ratios between trees growing in pure and mixed conditions for the two species, although these differences varied between sites, e.g. trees growing in mixed conditions had higher δ13C values and tree-ring width than trees growing in pure conditions for two of the sites. For both species, differences between trees in pure and mixed conditions regarding their sensitivity to temperature, precipitation, climatic water balance and vapor pressure deficit were minor. Furthermore, trees growing in pure and mixed conditions showed similar responses of tree-ring width and isotope ratios to the past severe droughts of 2003, 2015 and 2018. Competition had only a significantly negative effect on δ13C of silver fir, which may suggest a decrease in photosynthesis due to higher competition for light and nutrients. Our study highlights that tree species mixture may have only moderate effects on the radial growth and physiological responses of silver fir and Douglas-fir to climatic conditions and that site condition effects may dominate over mixture effects. [ABSTRACT FROM AUTHOR]

The aluminum smelter in the Žiar nad Hronom region of central Slovakia was a substantial source of pollution in the past. Five trees were sampled in close proximity to the smelter and the tree rings were chemically processed and analyzed with the PIXE technique. Elevated concentrations of Mg, Al, Si, P, S, K, Ca, Fe, and Zn were observed in tree rings, however, they did not show a significant correlation with PM, HF and SO2 emission rates. Concentration trends show a significant effect of the heartwood-sapwood boundary layer, where a substantial drop or increase was observed between tree-ring sections. [ABSTRACT FROM AUTHOR]

A progressive decline in tree growth may be induced by global warming, affecting tree health and eventually resulting in death, particularly for trees growing in rocky mountainous regions where seasonal droughts have become more pronounced. However, tree growth dynamics in areas experiencing pronounced climate change have received little attention. In this study, a total of 100 (10 m × 10 m) grid plots were investigated in planted forests of Chinese cork oak (Quercus variabilis Blume), which were established in the 1960s and 1970s in a rocky mountainous area near Beijing, northern China. Furthermore, the radial growth of Q. variabilis (a total of 843 trees sampled from the dominant [D], co-dominant [CD], and suppressed [S] crown classes) was analyzed using retrospective dendrochronology and generalized additive models. The effects of meteorological changes between 1962 and 2020 on radial growth across the three crown classes were examined using correlation analysis. The results indicated that the growth of Q. variabilis initially increased and then decreased after 2010 at the regional level, and these trends varied according to crown class. The radial growth of the D trees responded more positively to an increase in temperature and drought severity index (<0 for dry and >0 for wet conditions) compared with that of the CD and S trees. The growth of the D and CD trees continuously increased under higher temperatures during the rainy seasons (June to September); however, the increases were higher for D than for CD trees. In contrast, the radial growth of S trees declined. We confirmed the historical effects of rising temperatures on tree growth and health, which are linked to water availability. Our data suggested that Q. variabilis trees will be considerably affected by intensified droughts. This study furthers our knowledge regarding the impact of climate change on tree and forest growth and provides management strategies for afforestation projects in rocky mountainous areas that are facing climate change. [ABSTRACT FROM AUTHOR]

Introduction: Trees from flooded forests have to adjust their xylem hydraulic structure to face the annual flooding and the climatic conditions of the atmosphere. Usually, this adjustment of anatomical tissues in the tropics is driven by drought events inducing conservative behavior and can be recorded annually in tree rings. However, how the flood pulse and the climatic conditions influence the xylem hydraulic structure in floodplain trees is unknown. Methods: To fill this gap, we explore if flooded periods and monthly climate variation affect the annual tree growth and xylem anatomy structure for the tree species Hydrochorea corymbosa (Fabaceae) from the varzea flooded forest in the Central Amazon. We developed a 41-year ring width chronology (1971-2018) and a 30-year time series of xylem anatomy parameters (1988-2018) as mean hydraulic vessel diameter (Dh), vessel frequency (VF), and parenchyma quantity (PQ). We correlated the series with monthly hydrological and climatic data. Results: The hydrological regime did not correlate with annual tree growth in that species as we previously expected but showed correlations with the xylem anatomical structure. High flood levels during the end of the flooding period induced conservative patterns of the anatomical structure, with a negative correlation with Dh (rho June = -0.40, p < 0.05) and a positive correlation with the PQ (rho September/October = 0.42, p < 0.05). These responses show that these trees are responding to flooding similar to the tree responses to drought. Regarding the climatic variation, the annual tree growth showed a negative correlation with the vapor pressure deficit (VPD), after the second half of the flooded period with the strongest correlation happening during the non- flooded period (rho December = -0.66, p < 0. 01). These conservative patterns in tree behavior also happened when the maximum temperature negatively affected the vessel diameter (rho September = -0.42, p < 0.05). Discussion: In that case, we recognized two different moments that the environment is inducing conservative patterns in the xylem structure of those trees: 1) increasing the flood levels and 2) the high evaporative demand during the non-flooded period. In this way, the intensification of the hydrological regime, as well as the strong drought conditions during the non-flooded periods, can be a risk for H. corymbosa in the Central Amazonian floodplains. [ABSTRACT FROM AUTHOR]

The impact of climates on the radial growth of muti-species remains insufficiently understood in the climate-sensitive southeastern Tibetan Plateau, and this hampers an effective assessment of forest growth under the background of global warming. Here, we studied the growth–climate relationships of three major species (Abies georgei, Larix potaninii, and Picea likiangensis) on the Baima Snow Mountain (BSM) by using dendrochronology methods. We constructed basal area increment (BAI) residual chronologies based on the dated ring-width measurements and correlated the chronologies with four climate factors. We also calculated the contributions of each climate factor to species growth. We found that photothermal conditions played a more important role than moisture in modulating radial growth, and P. likiangensi presented the strongest sensitivity to climate change among the three species. The growing season (June and July) temperature positively affected the radial growth of three species. Winter (previous December and current January) SD negatively impacted the tree growth of A. georgei and P. likiangensis. Significant correlations between growth and precipitation were detected only in A. georgei (January and May). Warming since the beginning of the 1950s promoted the growth of A. georgei and P. likiangensis, while the same effect on L. potaninii growth was found in the recent 50 years. [ABSTRACT FROM AUTHOR]

Since the discovery of the Newport Medieval Ship in 2002, many studies have tried to establish a chronology for its construction and subsequent abandonment. Whilst conventional ring-width dendrochronology has been able to identify the provenance and provide a terminus post quem for the ship, until now a felling date for timbers associated with the original construction of the vessel has proved elusive. This study reports results from the application of stable isotope dendrochronology to date timbers from the ship. Using a combination of dendrochronologically-dated timbers and stable oxygen isotopic data from dated and undated samples, we can provide an independent verification of the ring-width dendrochronology and to return the first felling dates for an assemblage of the ship's framing timbers. Our results indicate that the ship was likely constructed shortly after the winter of AD 1457/8 with an operational lifetime of less than a decade. The study highlights the potential for the use of stable isotope dendrochronology for the precise, absolute dating of archaeological ship remains where ring-width dendrochronology alone has not proved effective. [ABSTRACT FROM AUTHOR]

Point of Pines Pueblo has long been central to discussions about ancient migrations and interactions between locals and immigrants in the U.S. Southwest. However, a lack of systematic analyses of collections from the site and a dearth of published data about them have left generations of researchers in the position of having to make assumptions about social processes that unfolded in the Point of Pines region. Here, we present the results of new analyses establishing basic facts that will eventually allow a more accurate reconstruction of social dynamics at Point of Pines Pueblo. We focus on stratigraphy, ceramics, dendrochronological data, and wall bonding/abutment information. We conclude that most of the pitstructures at the site date to the thirteenth century, the earliest above-ground architecture was built during the late 1200s, the early pueblo architecture was constructed by immigrants, and the Kayenta immigrant occupation involved considerable planning and coordinated action. [ABSTRACT FROM AUTHOR]

The origin and development of agriculture and its relationship with climate change are hotly debated topics among environmental archaeologists. In this study, we analyzed wood charcoal materials from the Neolithic Xinglong site in northern China in order to understand the woody vegetation around the site and how early millet farmers shaped local woodlands. Our results suggest that the area around the Xinglong sites during 8700–7000 yr BP was primarily woodlands, including Prunus sibirica shrubs, Ulmus and Acer forests, and Populus stands near waterways. From 8000 to 7000 yr BP, the warm and humid climate probably contributed to the expansion of Acer, Rhamnus, and Juniperus, and may have facilitated the development of early millet agriculture. Among these ancient wood fragments that we studied, the high percent of Prunus charcoal appears to indicate an abundance of fruit trees, which might have constituted the main component of local vegetation. Meanwhile, the wood taxa illustrate the existence of a variety of ecological habitats, and it is logical to assume that people made full use of the locally available wood resources. Notably, Populus and Ulmus were the dominant sources of fuel. The results of tree-ring curvature analyses indicate that people mainly collected trunks or large branches of Ulmus, Populus, Acer, and Juniperus timbers. We interpret the increasing use of Prunus twigs and the declining percentage of Prunus charcoal in the period between 8000–7000 yr BP as indicating that people started to protect and manage wild fruit trees. They may have started pruning to acquire more food resources as part of the cultural responses and adaptation strategies employed by these early millet cultivators. [ABSTRACT FROM AUTHOR]

The link between climate and war has long been a topic of great scientific and social interest. In this study, we investigate the influence of climate on warfare in China's Hexi Corridor region since 241 A.D. Using the superposed epoch analysis of tree-ring data and historical war data, we observe a notable correlation between interannual dry-wet variations and wars instigated by nomadic groups in the Hexi Corridor. However, this relationship is dynamic and influenced by the region's relative unity. During periods in which the Hexi Corridor was ruled by multiple regimes, wars tended to follow dry climatic conditions, which may be due to the fact that unusual drought during these periods likely heightened competition for resources and land. Conversely, during times of regional unity, wars were more likely to occur when climatic conditions were wet because the expansion of rangelands and the accumulation of resources helped fuel the nomads' outward conquest. These findings underscore the complexity of the relationship between war and climate change. To gain a more comprehensive understanding of this relationship, continuous, high-resolution historical temperature and humidity datasets with broader and more uniform coverage are needed across multiple regions. In addition, collecting and examining disaggregated historical war data for regions with distinct characteristics is essential. [ABSTRACT FROM AUTHOR]

Recent developments in tree-ring research offer great potential for reconstructing past climate changes; determining the frequencies of natural hazards; and assessing the availability of freshwater resources over timescales that extend well into the pre-instrumental period. Here, we review the state of dendrochronological research in the Himalaya and outline future directions for tree-ring-based hydrological reconstructions in a region that has a pressing societal need to understand the causes and consequences of past, present and future changes in the hydrological cycle. We used 'tree ring' and 'Himalaya' as keywords to identify scholarly articles from the Web of Science that were published between 1994 and 2022. The resulting 173 publications were separated by their spatial coverage into the western, central and eastern Himalaya, as well as their scientific purpose (e.g. reconstructing growth-climate relationships, temperature, precipitation, streamflow, floods, droughts, etc.). Our analysis shows that dendrochronological research in the Himalaya primarily focused on understanding growth-climate relationships using annual tree-ring widths measurements obtained for coniferous species, and their application in climate reconstructions. Reconstructions of hydrological processes such as streamflows, and extremes such as glacial and landslide lake outburst floods, have received less attention. Recent advances in dendrochronology, including blue intensity (BI), quantitative wood anatomy (QWA), and tree-ring stable isotopes (TRSI) should be combined to improve the resolution and accuracy of hydrological reconstructions in all parts of the Himalaya. Such studies may allow us to better understand the effects of climate change and the Himalayan water resources for its lowland surroundings. They may also facilitate decision-making processes for mitigating the impacts of climate change on natural hazards, and for better managing water resources in the region. [ABSTRACT FROM AUTHOR]

Climate changes have dramatically affected forest succession. However, how trees at different successional stages respond to climate warming is unclear in the subtropics. Here, we compared the radial growth (RW) and xylem features of the early-successional stage Castanea mollissima and late-successional stage Quercus fabri in subtropical forests and assessed their response to climate changes. All parameters, including RW, number of vessels (VN), vessel density (VD), mean (MVA) and total (TVA) vessel area, percentage of conductive area within xylem (RCTA), theoretical (Kh) and xylem-specific (Ks) hydraulic conductivity, except for MVA of C. mollissima were significantly higher than those of Q. fabri. During the drought period, a notable adverse correlation between two cluster parameters of Q. fabri, associated with hydraulic safety and efficiency, suggested a pronounced hydraulic trade-off in Q. fabri under drought conditions. Castanea mollissima was more sensitive to climate and more prone to hydraulic failure than Q. fabri. Temperatures and moisture conditions positively and negatively affected the hydraulic efficiency-related parameters of C. mollissima. Moisture conditions in the previous summer and winter were significantly negatively and positively related to the radial growth of both species. The impact of generalized warming was not evident due to variations in hydraulic strategies and species characteristics, trade-offs between non-growing and growing season climates, and specific competition. If climate warming continues, C. mollissima growth will probably significantly decline due to the increasing risk of hydraulic failure. Warming may accelerate species replacement and forest succession in the study area by changing their lifespans and competitive relationships. [ABSTRACT FROM AUTHOR]

The Mediterranean region is projected to experience severe drying trends and more extreme hydroclimate events as a consequence of anthropogenic climate change over the next century. In some places this signal may have already emerged from natural variability, but uncertainty in long-term paleoclimate reconstructions can be a significant challenge to the detection of the influence of rising CO 2 on droughts. Here we provide expanded context for recent and future hydroclimate changes with a new high-resolution (0.5 o ) spatial reconstruction of the Palmer Drought Severity Index (PDSI) using a tree-ring network that spans much of the last millennium. This network provides new perspective on the existing Old World Drought Atlas (OWDA) and allows us to characterize differences between OWDA and our reconstruction. In light of the uncertainties we identify, we also reexamine previous conclusions about the severity of recent droughts in the context of earlier centuries. We find that, in both the western Mediterranean and the Levant, recent dry periods remain the worst in at least the last 500 years, but our assessment of the significance and confidence in this finding is affected by differences in the tree-ring networks used for the reconstructions. Long millennium-length hydroclimate reconstructions in the Mediterranean do provide the opportunity to understand variability and trends in the hydroclimate of the region, but extant uncertainties arising from the existing tree-ring chronology network and methodological choices call attention to locations that require further proxy collection, chronology updates, and statistical scrutiny. [ABSTRACT FROM AUTHOR]

Climate change (CC) necessitates reforestation/afforestation programs to mitigate its impacts and maximize carbon sequestration. But comprehending how tree growth, a proxy for fitness and resilience, responds to CC is critical to maximize these programs' effectiveness. Variability in tree response to CC across populations can notably be influenced by the standing genetic variation encompassing both neutral and adaptive genetic diversity. Here, a framework is proposed to assess tree growth potential at the population scale while accounting for standing genetic variation. We applied this framework to black spruce (BS, Picea mariana [Mill] B.S.P.), with the objectives to (1) determine the key climate variables having impacted BS growth response from 1974 to 2019, (2) examine the relative roles of local adaptation and the phylogeographic structure in this response, and (3) project BS growth under two Shared Socioeconomic Pathways while taking standing genetic variation into account. We modeled growth using a machine learning algorithm trained with dendroecological and genetic data obtained from over 2600 trees (62 populations divided in three genetic clusters) in four 48‐year‐old common gardens, and simulated growth until year 2100 at the common garden locations. Our study revealed that high summer and autumn temperatures negatively impacted BS growth. As a consequence of warming, this species is projected to experience a decline in growth by the end of the century, suggesting maladaptation to anticipated CC and a potential threat to its carbon sequestration capacity. This being said, we observed a clear difference in response to CC within and among genetic clusters, with the western cluster being more impacted than the central and eastern clusters. Our results show that intraspecific genetic variation, notably associated with the phylogeographic structure, must be considered when estimating the response of widespread species to CC. [ABSTRACT FROM AUTHOR]

We present an annual-resolution, millennium-long tree-ring chronology for northern Japan. The chronology is based on 5309 measurements of tree-ring δ18O from 37 samples of Hiba arbor-vitae (Thujopsis dolabrata var. hondae). Although the exact geographical origin of 27 of the samples is unknown because they were extracted from excavated archaeological material, pattern matching of the tree-ring δ18O variations was robust among all 37 samples. The floating chronology constructed using all samples was cross-dated against a previously published δ18O chronology from central Japan, yielding a correlation coefficient of 0.26 (t = 9.0; p < 0.01), resulting in a temporal coverage of 417–1595 CE (i.e., 1179 yrs). The global 14C spike event at 774–775 CE was clearly recorded in the annual 14C data, which provides independent support for the dating of tree rings using oxygen isotopes. Furthermore, this δ18O chronology from northern Japan was used to successfully cross-date a wood sample buried during the "Millennium Eruption" of Baitoushan, which is located on the border between China and North Korea. [ABSTRACT FROM AUTHOR]

This study suggests that there may be considerable difficulties in providing accurate calendar age estimates in the Roman period in Europe, between ca. AD 60 and ca. AD 230, using the radiocarbon calibration datasets that are currently available. Incorporating the potential for systematic offsets between the measured data and the calibration curve using the ΔR approach suggested by Hogg et al. (2019), only marginally mitigates the biases in calendar date estimates observed. At present, it clearly behoves researchers in this period to " caveat emptor" and validate the accuracy of their calibrated radiocarbon dates and chronological models against other sources of dating information. [ABSTRACT FROM AUTHOR]

As a feature of global warming, climate change has been a severe issue in the 21st century. A more comprehensive reconstruction is necessary in the climate assessment process, considering the heterogeneity of climate change scenarios across various meteorological elements and seasons. To better comprehend the change in minimum temperature in winter in the Jinsha River Basin (China), we built a standard tree-ring chronology from Picea likiangensis var. balfouri and reconstructed the regional mean minimum temperature of the winter half-years from 1606 to 2016. This reconstruction provides a comprehensive overview of the changes in winter temperature over multiple centuries. During the last 411 years, the regional climate has undergone seven warm periods and six cold periods. The reconstructed temperature sensitively captures the climate warming that emerged at the end of the 20th century. Surprisingly, during 1650–1750, the lowest winter temperature within the research area was about 0.44 °C higher than that in the 20th century, which differs significantly from the concept of the "cooler" Little Ice Age during this period. This result is validated by the temperature results reconstructed from other tree-ring data from nearby areas, confirming the credibility of the reconstruction. The Ensemble Empirical Mode Decomposition method (EEMD) was adopted to decompose the reconstructed sequence into oscillations of different frequency domains. The decomposition results indicate that the temperature variations in this region exhibit significant periodic changes with quasi-3a, quasi-7a, 15.5-16.8a, 29.4-32.9a, and quasi-82a cycles. Factors like El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and solar activity, along with Atlantic Multidecadal Oscillation (AMO), may be important driving forces. To reconstruct this climate, this study integrates the results of three machine learning algorithms and traditional linear regression methods. This novel reconstruction method can provide valuable insights for related research endeavors. Furthermore, other global climate change scenarios can be explored through additional proxy reconstructions. [ABSTRACT FROM AUTHOR]

Background and objectives: The Hyrcanian forests in northern Iran exhibit diverse rainfall and air temperature patterns. Altitude above sea level is a crucial topographical factor that influences plant growth and development, prompting trees to adopt different morphological, anatomical, and physiological strategies for survival and growth at varying elevations. This study aims to understand the impact of altitude on radial growth and tree-ring width by examining the rate of radial growth of Oriental beech (Fagus orientalis Lipsky) across different age classes in three altitude zones: low, middle, and high altitudes of the Hyrcanian forests in Kordkuy and Asalem habitats. Methodology: t three selected sites, located at approximately 700, 1400, and 2000 meters above sea level, tree-ring cores were extracted from 62 beech trees using an increment borer. Following core extraction, the holes on the trees were completely sealed with grafting wax. The surface of each core was prepared using a sequence of 100-, 400-, and 1000-grit sandpaper. Tree-ring widths (TRWs) were measured using LINTAB 5 and TSAP software. Measurements were taken from one side of the core and then from the other side. The obtained TRW series were analyzed using statistical parameters such as sign test, correlation coefficient, and Student's t-test. After cross-dating, average TRW chronologies were prepared for each tree. This method was then used to match the trees within each site. TRW chronologies for each site were verified using statistical methods. A one-way analysis of variance (ANOVA) test was performed to compare TRW chronologies. Meteorological data such as rainfall and temperature were obtained from the nearest weather stations. Meteorological data for Kordkuy and Asalem were obtained from the Gorgan and Astara meteorological stations, respectively. Results: The findings demonstrated that the elevation gradient had a significant impact on the radial growth of beech trees. TRW in the examined habitats is influenced by elevation above sea level in trees aged 50 to 150 years. The average radial growth of these trees in the middle elevations of Asalem and the lower elevations of Kordkuy is substantially higher than in other altitude areas. The mean growth of trees aged 100-150 years in the middle elevations of Asalem was the highest, amounting to 3.98 mm. Statistical analysis revealed a significant difference between the TRW of trees aged 100-150 years in the highland of Kordkuy with a mean annual growth of 1.94 mm and the lowerland of Kordkuy with a mean annual growth of 2.97 mm. During this age period, no significant difference was observed between trees from the upperland of Kordkuy and the moderate altitudes of Kordkuy, but there was a statistical difference between trees from moderate altitudes and the lowerland. A comparison of trees aged 200-250 years revealed a statistically significant difference between Kordkuy and Asalem moderate altitudes. The mean radial growth of trees aged 300-350 years in the upperland and moderate altitudes of Asalem is 1.25 and 1.32 mm, respectively. Statistical analysis demonstrated that there is no statistically significant difference between the mean radial growth of trees aged 300-350 years in the upper and middle altitudes of Asalem and the lowerlands of Kordkuy. Conclusion: This study demonstrated that radial growth and tree-ring width of beech trees exhibited notable variations along an east-west transect across the Hyrcanian forests. The observed variations in beech radial growth and tree-ring sensitivity along the elevational gradient highlight the ability of beech trees to develop adaptive functional traits in response to environmental changes. [ABSTRACT FROM AUTHOR]

Numerous studies involving tree rings have been conducted in the Himalayas on a wide variety of species for paleoclimate reconstructions. Each species responds differently to precipitation and temperature variability in different ecological settings. Therefore, an improved understanding is required to reconcile the mechanisms behind the different responses of tree growth with changing climate regimes. The review is focused primarily on the studies undertaken in the field of dendrochronology in the western Indian Himalayan region (WIH) and explores the relationships between climate and forest response. The study embraces a dual strategy by surveying the literature of tree-ring studies conducted in WIH and using metadata to synthesize results and their global implications. Our review reveals that 553 years (A.D. 1452–2004) long tree-ring chronologies from high altitudes in WIH have indicated anomalous higher tree growth in the recent past strongly associated with warming trends over the region. Correlation and response function analysis between tree-ring widths and climatic parameters have shown a significant negative correlation with pre-monsoon March–April–May (MAM) temperature and a positive correlation with precipitation during the same period in the region influenced mainly by Indian summer monsoon (ISM). However, a positive correlation with winter months' temperature has also been observed owing to the availability of water from snowmelt due to increased warming trends. Of all the potential datable tree rings, Cedrus deodara was the most studied tree species followed by Pinus spp. while Betula utilis was the least studied. [ABSTRACT FROM AUTHOR]

An international summer course in dendrochronology, "Tree Rings, Climate, Natural Resources, and Human Interaction", was held in Amman, Jordan, in summer 2023. Drs. Ramzi Touchan and David M. Meko from the University of Arizona Laboratory of Tree-Ring Research were course instructors. The course, with 10 students from Jordan, Algeria, Tunisia, Pakistan, Greece, and the USA, included training in core-sample collection, sample preparation, crossdating, detrending, and climate signal identification. Students applied their training in group precipitation reconstruction projects. Fifty-two Pinus halepensis core samples were collected at Dibeen Forest Reserve, Jordan, which were used to develop a tree-ring chronology (1925-2022) and then used for the reconstruction models. Two reconstructions extended precipitation for Dibeen using: (1) measured October-April precipitation data (R²adj. = 0.63), and (2) gridded November-April precipitation data (R²adj. = 0.61). A third reconstruction used the Dibeen chronology and three low-elevation tree-ring chronologies in Cyprus to extend gridded December-April precipitation data for the eastern Mediterranean region (R²adj. = 0.55). Results from the class projects demonstrated the success of reconstruction techniques in regions with sparse measured climate data and tree-ring chronologies. Future training classes in these regions will also promote the importance of understanding historic climate variability, which is essential for water resource managers and planners. [ABSTRACT FROM AUTHOR]

Historic harvesting and mortality from air pollution drastically reduced the abundance of red spruce (Picea rubens), a late-successional dominant of cool-temperate forests of the northeastern U.S. and southeastern Canada, leaving few opportunities to understand the natural growth and disturbance responses of this species. Timbers salvaged from the Moosilauke Ravine Lodge, a structure built from trees harvested in the late 1930s, provided an opportunity to reconstruct radial growth patterns and dynamics of a former old-growth red spruce stand located in Jobildunc Ravine on Mount Moosilauke in the White Mountains of New Hampshire. Ravine Lodge tree-ring series were compared with data from a 255-year-old red spruce found living in Jobildunc Ravine, from the Nancy Brook site in the White Mountains, and from other dendroecological studies across the region. Ring counts provide minimum tree ages of 187-286 years for timbers from Jobildunc Ravine, suggesting they established between the mid-Seventeenth and mid-Eighteenth Centuries. Dendroecological analyses identified early decades of suppression in the understory followed by 2-5 growth releases and 2-4 growth declines for each sample, indicating occasional, small-scale disturbances of the canopy before the 1930s. A growth decline in 1834-1835 coincides with an outbreak of spruce budworm (Choristoneura fumiferana) in eastern Canada, perhaps reflecting a regional defoliation event that occurred as far south as Mount Moosilauke. This study illustrates the insights that can be gained from wood from historic structures on the dynamics of now-scarce old-growth red spruce forests. [ABSTRACT FROM AUTHOR]

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Earth’s climate has changed throughout history. Just in the last 800,000 years there have been eight cycles of ice ages and warmer periods, with the end of the last ice age about 11,700 years ago marking the beginning of the modern climate era and of human civilization. Most of these climate changes are attributed to very small variations in Earth’s orbit that change the amount of solar energy our planet receives. The current warming trend is different because it is clearly the result of human activities since the mid-1800s, and is proceeding at a rate not seen over recent millennia. It is undeniable that human activities have produced abundance of gases in the atmosphere that have trapped more of the Sun’s energy in the Earth system. This extra energy has earned the ocean and lands, which lead to widespread and rapid changes in the environment. In this paper there are analysed anthropogenic changes, nature’s own role and climate disasters in comparing the results obtained into perspective with incidents in the year 536.

Abstract We present new climate field reconstructions (CFR) of tropical Pacific ENSO sea surface temperatures (HadISST) for the boreal winter season using a circum‐Pacific tree‐ring network from known El Niño rainfall impact regions. We use two different CFR methods: Point‐by‐Point Regression (PPR) and reduced‐space Orthogonal Spatial Regression (OSR). Both methods produce reconstructions with high validation skill, but OSR is preferred because it has less spatial noise and is more efficient. Only the leading EOF of the SST field (EOF1) can be skillfully reconstructed by either method; EOF2 does not validate. The success of EOF1 reflects its importance for ENSO rainfall impacts over land; the failure with EOF2 is from the lack of these impacts. EOF1 allows for the reconstruction of many ENSO indices, including the ENSO Longitudinal Index (ELI). We also find evidence in our reconstructions for a recent increase in ENSO activity.