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Dendrochronology is a discipline that uses tree rings to study the history and dynamics of the earth system, such as climate change, natural disasters, and human activities. This study aims to evaluate the development of dendrochronology and its track in China from 1990 to 2022 using a bibliometric analysis approach. We screened the Web of Science Core Collection for documents related to dendrochronology and analyzed them according to indicators related to production, cooperation, citation, and keywords. Our study revealed that the number of dendrochronological publications increased continuously, reaching more than 800 in 2021, with the USA and China being the top two countries. The cooperation network of dendrochronology was mainly centered between North America and Europe, with China having a moderate level of collaboration with other countries and regions like the USA and Canada. Comprehensive research has been conducted within diverse fields of dendrochronology in the world and in China, but dendrochronological research focusing on forestry and climatology represented a slightly higher proportion of research originating from China. The integration of dendrochronology with other disciplines and techniques, such as remote sensing, artificial intelligence, and modeling, may be hotspots in future research, as indicated by the increasing co-occurrence analysis of keywords in the most recent years. This study suggests that Chinese Dendrochronology still requires improved international collaboration, diversified research topics beyond climate reconstructions, and more emphasis on tree-ring methods to advance this discipline globally, despite of increasing rank of publications in the past decade. [ABSTRACT FROM AUTHOR]

Subtropical forests are an important carbon sink, yet our understanding on tree growth response to inter-annual climate variability remains limited. This study investigated the growth-climate relationships of four evergreen broad-leaved tree species (Stewartia pteropetiolata W. C. Cheng, Schima noronhae Reinw. ex Bl. Bijdr, Machilus gamblei King ex J. D. Hooker, and Machilus yunnanensis Lec) in the subtropical evergreen broad-leaved forests (EBFs) in the Ailao Mountains of Yunnan province, southwest China. We constructed tree ring-width residual chronologies for each species and correlated them with daily and monthly climate data. Ring-width chronologies of S. pteropetiolata and S. noronhae were positively correlated with precipitation, relative humidity, and self-calibrated Palmer drought index (scPDSI) during autumn of the previous year and spring-to-early summer of the current year, indicating that these two Theaceae species were sensitive to moisture availability. Tree radial growth of two Machilus species was primarily limited by excessive precipitation and dense cloud cover during the rainy season in this middle montane cloud forest. Moving correlations between climate variables and radial growth of all species were temporally unstable, with a weakening response to climate variability in recent decades. We highlight the dendroclimatic potential of evergreen broad-leaved tree species in moist subtropical forests. The findings offer a pertinent perspective, emphasizing the necessity of separately considering distinct ecological indicators for trees in order to obtain a comprehensive understanding of climate-growth responses within highly diverse subtropical forests. • Radial growth of two Theaceae species showed moisture sensitivity during previous autumn and current spring-to-early summer. • The growth of Machilus spp. was mainly limited by excessive precipitation and cloud cover during the rainy season. • We highlight the dendroclimatic potential of evergreen broad-leaved tree species in moist subtropical forests. [ABSTRACT FROM AUTHOR]

Quercus -dominated forests are among the most important broad-leaved evergreen forests of the Hindu Kush ranges and are currently prone to drastic anthropogenic and climatic changes. The aim of this study was to provide basic data for the development of a regional oak forest ecosystem framework for ecological restoration and management plan development to maintain local peoples' livelihoods. Hence, we analyzed distribution patterns and environmental factors that affect regional oak forests' species composition and diversity. Ward's Agglomerative clustering divided oak-dominated forest communities into three groups: i.e., Group I, dominated by Quercus baloot had an importance value index (IVI) of 89.87 ± 4.31, Group II, dominated by Quercus dilatata had an IVI of 32.16 ± 15.01, and Group III, dominated by Quercus oblongata had an IVI of 83.14 ± 4.67, respectively. The environmental factors which vary significantly within these communities were latitude, elevation, clay content and bulk density of the soil. Wilting point, saturation point, and electrical conductivity were also considered as ecosystem structural variables. Canonical correspondence analysis (CCA) indicated that community structure was affected by various environmental factors including precipitation, slope angle, elevation, clay content, and relative humidity. [ABSTRACT FROM AUTHOR]

Abstract Located in the western Mediterranean basin, the island of Corsica (France) is expected to be strongly affected by climate change. With its diverse topography and altitudinal gradients from sea level to 2700 m asl, it hosts two pine species, i.e. Pinus pinaster in lower areas and P. nigra ssp. laricio in higher regions up to the upper tree line. However, the growth performance of these two dominant forest tree species along different elevation belts is still unknown, so it is not clear how climate change will affect their distribution. The relationships between tree age, elevation, and growth performance were evaluated using growth trajectories derived from tree-ring analysis of pines in different age classes at 13 sites across the island, ranging from sea level to 1600 m asl. Results show that the growth performance of both species under the same environmental conditions is very similar. For both species, we found that growth rates change over time, whereby trees younger than 50 years grew faster than older trees. We also found that P. pinaster is becoming common at higher elevation sites, indicating a migration upslope. [ABSTRACT FROM AUTHOR]

Highlights • Drought resilience of two tropical tree species was studied. • Species-specific and temporal variability in drought tolerance were observed. • LMEM revealed that growth rates before and after the drought events had a dominant role in drought responses. Abstract The frequency and intensity of drought events have increased during the recent decades, particularly in the tropics. Yet, the growth and physiological responses of many tropical tree species to drought are still inadequately understood. We studied the drought resilience of two functionally different canopy tree species (Chukrasia tabularis and Toona ciliata) from a moist tropical forest in Bangladesh during two extreme drought events (1984 and 1999). We quantified four resilience components (resistance, recovery, resilience and relative resilience) of both species to infer drought tolerance of selected trees. Tree radial growth dropped by 44–56% in the drought years, varying with species and drought events. Two species showed no differences in their drought resistance during any of the drought events. However, C. tabularis showed higher recovery and resilience than T. ciliata after the 1999 drought event. T. ciliata showed higher resilience after the 1984 drought event. Linear mixed effect model (LMEM) revealed that growth rates in the two years before and after the drought events had a dominant role in drought responses over tree age, height, diameter, basal area increment and crown exposure, although crown exposure had significant influence on the resistance and the resilience of light demanding T. ciliata. We conclude that diffuse porous and intermediate shade tolerant C. tabularis is more drought tolerant than the ring-porous and light demanding T. ciliata. Since both study species are widely used as plantation species throughout the tropics, our results have important implications for forest managers to take decision on species suitability for plantation programs and to adopt forest management to future climate change conditions. [ABSTRACT FROM AUTHOR]

Abstract Multiple sources of evidence suggest an increasing frequency of extreme climatic events during the past century. In Bangladesh, a country strongly influenced by the South Asian monsoon climate, the years 1999 and 2006 were the most severe droughts among the ten drought events identified over the last four decades. We investigated the impact of these two drought events on radial growth and xylem anatomical features of the brevi-deciduous tree species Chukrasia tabularis in a moist tropical forest in Bangladesh. Tree radial growth declined by 54% during the 1999 and 48.7% during the 2006 droughts, respectively. Among the wood anatomical features, the number of vessels (NV) showed the highest sensitivity to drought, with a 45% decrease in the 1999 drought year, followed by total vessel area (TVA) and mean vessel area (MVA). On the other hand, Vessel density (VD) increased by 13% during the 1999 drought but the increase in VD was very low in the drought year 2006. The decreasing vessel area and increasing vessel density indicate xylem hydraulic adaptation of C. tabularis to minimize drought induced cavitation risk and to avoid hydraulic failure. The significant correlations between the Standardized Precipitation Evapotranspiration Index (SPEI) and time series of tree-ring width and vessel variables imply that decline in radial growth and changes in vessel features in C. tabularis are likely to be caused by drought induced water stress. Our analyses suggest that radial growth and wood anatomical features of C. tabularis are highly sensitive to extreme drought events in South Asian moist tropical forests and can be used to reconstruct past droughts and to model tree response to drought stress under future climate conditions. [ABSTRACT FROM AUTHOR]

Highlights • Validation of simulation results with long-term field data, e.g. biomass, timber volume. • Quantification of mean recovery times of multiple forest attributes after selective logging. • Variation of dbh of lower cutting threshold of commercial trees and impacts on forest dynamics. • Very intense logging has 2× longer recovery times of biomass and timber volume than moderate. • To allow for forest recovery within 65 years, we recommend dbh of lower cutting cycle ≥0.55 m. Abstract There is increasing concern, to what extent production forests in the Neotropics are sustainably managed. The implementation of effective forest management strategies that are ecologically beneficial plays thus a central role to prevent forest degradation. However, to identify effective forest management strategies, there is a need for methods supporting the decision-making process. The main objective of our study is to analyze the mid- and long-term impacts of different management intensities, such as varying the minimum stem diameter of harvestable commercial trees, on the dynamic and structure of a species-rich tropical lowland forest of French Guiana. Therefore, we have applied the management module of a dynamic forest model and analyzed simulation experiments for undisturbed forest growth and selective logging. For the first time we were able to quantify the mean recovery times of multiple ecosystem functions and properties (biomass, gross primary production, leaf area index, Shanon diversity, timber volume) after selective logging. Accordingly, we validated simulation results (biomass, number of trees harvested) of selective logging with forest inventory data from the last 32 years. The forest model reliably reproduces the observed pre-logging biomass, tree-size distribution, and logging intensity (10 trees/ha, 39 m3/ha). In addition, it became clear how strongly management with higher logging intensities influences the forest in the long term: (1) the mean recovery times of the investigated ecosystem functions were significantly extended. With very intensive logging (116 m3/ha), the average recovery time of forest biomass was almost twice as long as in a moderate simulation scenario (t int 138 a, t mod 77 a). Similar patterns were observed for other ecosystem functions, e.g. timber volume (t int 158 a, t mod 62 a). (2) Additionally, the functional composition shifted, as up to 30% pioneer tree species in particular invaded the forest. This innovative use of forest growth models may help in the development of ecologically reasonable forest management strategies. [ABSTRACT FROM AUTHOR]

We developed the first tree-ring width chronology from Quercus brantii Lindel for the period 1796–2015 in the southern Zagros Mountains, Iran, using standard dendrochronological procedures. Climate-growth relationships revealed that DecemberöFebruary precipitation has strong positive effects (r = 0.66; P < 0.01) on the species’ growth while mean temperature during the growing season has strong negative effects. Spatial correlations with Palmer Drought Severity Index (PDSI) and gridded precipitation data revealed that the chronology contains regional climate signals and tree growth variations may represent precipitation fluctuations over large areas of the Middle East. The linear regression model accounts for 44% of the actual DecemberöFebruary precipitation variance. The reconstructed precipitation revealed that over the period 1850–2015 extreme dry years occurred in 1870-71, 1898, 1960 and 1963-64, and extreme wet years occurred in 1851, 1885, 1916 and 1921 in the southern Zagros region. The longest dry period lasted 16 years and occurred from 1958 to 1973. Two-year consecutive wet and dry events showed the highest frequencies and the average length of dry and wet events were 2.9 and 3.6 years over the reconstructed period. Correlations between the long-term reconstructed precipitation and the North Atlantic Oscillation (NAO), Southern Oscillation Index (SOI), and Pacific Decadal Oscillation (PDO) confirmed the effects of teleconnection patterns on precipitation in the southern Zagros region. [ABSTRACT FROM AUTHOR]

Wood anatomical features such as vessels record paleo climatic and environmental signals through their physiological adjustment during the environmental stress condition. Using vessel features as environmental proxy is relatively new in tropical dendrochronology but very useful to study plant ecophysiological responses to changing environmental conditions. Here, we developed the first vessel chronologies of diffuse porous Chukrasia tabularis from a Bangladeshi moist tropical forest and assessed their suitability for Dendroclimatic and ecophysiological studies in moist tropical forests. Standard chronologies of ring-width (RW), vessel number (NV), mean vessel area (MVA), total vessel area (TVA), total vessel area % (TVAP), mean vessel tangential diameter (MVTD), mean vessel radial diameter (MVRD), and vessel density (VD) were developed which spanned the period 1925–2015. Principal component analysis revealed that all chronologies were related among each other, the first two principal axis explaining 80% of the common variance. Hence, all chronologies shared a common environmental signal, except TVAP and MVRD which were excluded from further dendroclimatic analysis. Bootstrap correlation function was used to test the relationship between the chronologies and climate variables over 1950–2015. All chronologies were significantly correlated with monthly, seasonal and annual climate variables but varied in their magnitude. Spring temperatures (March–April) and late monsoon precipitation had the dominant influence on the vessel features and radial growth of Chukrasia tabularis . Decreased vessel area (Hydraulic efficiency) and increased vessel density (Hydraulic safety) were observed in response to stress environmental condition particularly in the spring (hot and dry) when evapotranspiration became higher and soil moisture deficit occurs due to high temperatures. Moving correlation functions revealed stable climate tree-ring variable relationships during March–April and October with an increasing tendency of climate interaction in other months. Our study shows that vessel features in Chukrasia tabularis are highly sensitive to inter-annual climate variability and can be used for paleoclimatic and ecophysiological studies in moist tropical forests. [ABSTRACT FROM AUTHOR]

Forests provide fundamental ecosystem services. Environmental changes are predicted to affect forest growth directly through increased environmental stressors, and indirectly by amplifying disturbance. To increase our understanding of effects of environmental changes and disturbance on Afromontane forest growth, we used tree-ring data collected from Juniperus procera trees from church forests in the northwest highlands of Ethiopia. We used structural change models to detect structural shift in growth trends. We applied Linear Mixed Effect Models (LMM) to compare growth rate differences between successive tree generations. The running mean method and radial growth pattern analysis were used to detect disturbance events. Three groups of generations were identified based on Basal Area Increment (BAI) rates. There are significant differences (χ 2  = 204.64, P < .001) among generations in pace of BAI, indicating that old generation trees grew at a slower pace than younger ones. Radial growth patterns were homogeneous for the old generation, but diverse in young trees. The observed high growth rates in the younger generation may have a negative effect on the longevity of the individuals and positively affect carbon accumulation in the biomass. Disturbance was detected in all generations, but worsened in the 20th century. About 35% of disturbances matched with climate extreme events, providing evidence that the disturbance is both human-induced (i.e., site-specific) and climate-induced. Thus, forest management plans should emerge from a sound understanding of climate-forest-human interaction. [ABSTRACT FROM AUTHOR]

Knowledge of drought variability and their possible mechanisms during the past hundred years is still limited in the mountainous region of south-central Tibetan Plateau (TP). In this study, a long-term tree-ring width chronology dating back to 1190 CE was combined using 328 increment cores from the Nagqu region. Based on the relationships between this tree-ring width chronology and climate data, we reconstructed May–June self-calibrated Palmer Drought Severity Index (scPDSI) for the past 821 years (1190–2010 CE). Additional comparisons with other available precipitation or drought reconstructions were conducted. We further investigated the influence of the South Asian summer monsoon (SASM) on the drought variability in our study region. Results indicated that our tree-ring width chronology contained stable drought signal in the early summer season (May–June). During the past 821 years, the longest dry and wet periods lasted for 116 and 90 years, respectively, based on a 21-year Fast Fourier transform filter. Specifically, longer than ten years’ dry periods prevailed during 1211–1245 CE, 1280–1358, 1421–1471, 1500–1571, 1580–1598, 1650–1691, 1782–1807 and 1867–1982; while wet intervals occurred in 1190–1210 CE, 1246–1279, 1359–1420, 1472–1499, 1599–1649, 1692–1781, 1808–1866 and 1983–2010. Generally consistent dry and wet intervals across the southern TP were found by comparisons with other available datasets during their common periods. Interestingly, we detected an unstable influence of the SASM on the May–June drought variability in our study region, at least for the past three and a half centuries. This study therefore gives a new perspective of drought variability as well as their relationships with the SASM over a long-term period on the south-central TP. [ABSTRACT FROM AUTHOR]

Climatic harshness is expected to increase at higher elevations; however, elevational trends of tree radial growth response of high-elevation forests to climate change need to be investigated at different locations because of existing local variability in site-specific climatic conditions. We developed tree-ring width chronologies of Yunnan fir ( Abies georgei ) along elevation gradients at two sites in the central Hengduan Mountains (HM). High-elevation forests of A. georgei showed growth synchronicity and common growth signals along elevation gradients, indicating a common climatic forcing, although tree radial growth rates decreased with increasing elevation. Radial growth of Yunnan fir showed positive correlations with summer temperatures and February precipitation and moisture availability, but were negatively correlated with spring temperatures. The strongest positive relationship indicated summer (July) mean and minimum temperatures are the most important growth determining climatic factors for tree radial growth in the cold environment of HM, and this relationship revealed a clear elevational trend with stronger correlations at higher altitudes. In contrast, tree radial growth was negatively correlated with June precipitation and moisture availability. The whole study period 1954–2015 was split in two sub-periods of equal length. Comparing the early sub-period (1954–1984) to the later sub-period (1985–2015), tree growth response to the summer temperatures strongly increased, while it became weaker to June precipitation and moisture availability. High-elevation Yunnan fir forests in the HM currently benefit from elevated growing season temperatures under humid summer conditions. However, increasing temperatures may induce drought stress on tree radial growth if the observed decreasing trend in humidity and precipitation continues. [ABSTRACT FROM AUTHOR]

We developed the first tree-ring chronology of Chukrasia tabularis from a moist tropical forest in Bangladesh, spanning the 102-year period 1911–2012. The species showed wood anatomically clear annual tree-ring boundaries which crossdated between tree individuals. Bootstrapped correlation analyses revealed that the ring-width index was significantly negatively correlated with current year mean and minimum temperatures. This relationship was stronger during the dry season (November–March), the pre-monsoon (February–April) and the post-monsoon season (September–November) than during the main monsoon season (May–August). We interpret this result as an indication that temperature-driven higher evapotranspiration outside the main rainy season leads to water stress limiting tree growth. This is confirmed by negative correlations of the ring-width index with the Palmer Drought Severity Index (PDSI) during the dry season. Precipitation did not show significant relationships to tree growth, except in current year June. However, cloud cover strongly negatively affected tree growth, likely by reducing photosynthetic capacity particularly during the rainy summer (May–August) monsoon season. On a regional scale, the ring-width index was correlated with both Indian Ocean and Pacific Ocean sea surface temperature (SST) anomalies, but during different seasons. Ring width of C. tabularis was also significantly correlated with the El Niño Southern Oscillation (ENSO). Monthly Niño 3.4 region positive temperature anomalies enhanced current year tree growth but negative temperature anomalies reduced tree growth in the following year mainly through modulating local climate. Hence, tree-ring variations of C. tabularis in Bangladesh record local and regional climate signals and are a potential proxy to reconstruct local and regional paleoclimatic variability during the past centuries. [ABSTRACT FROM AUTHOR]

Response of climate warming on tree-ring formation has attracted much attention during recent years. However, most studies are based on statistical analysis, lacking understanding of tree-physiological processes, especially in the mountainous regions of the Tibetan Plateau (TP). Herein, we firstly use an updated new version of the tree-ring process-based Vaganov-Shashkin model (VS-oscilloscope) to simulate tree-ring formation and its relationships with climate factors during the past six decades. Our analyses covered 341 sampled trees growing within elevations ranging from 2750 to 4575 m a.s.l. at five sampling sites across the TP. Simulated tree-ring width series are significantly ( p < 0.01) correlated with actual tree-ring width chronologies during their common interval periods. Starting dates of tree-ring formation are determined by temperature at all five sampling sites. After the initiation of tree stem cambial activity, soil moisture content has a significant effect on tree radial growth. Ending dates of cambial activity are driven by temperature over the whole study region. Simulated results indicate differences between wide and narrow tree-rings are mostly induced by soil moisture content, especially during the first half of the growing season, when effects from temperature variations are minor. Interestingly, we detected significantly ( p < 0.001) increased relative growth rates due to higher soil moisture content after the year 1985 at the five sampling sites. However, the variability of mean relative growth rates due to temperature is negligible before and after that. Based on the successful application of VS-oscilloscope modeling on the high-elevation tree stands on the TP, our study provides a new perspective on tree radial growth process and their varying relationships to climate factors during the past six decades. [ABSTRACT FROM AUTHOR]

The fieldweek associated with the 4th Asian Dendrochronological Association Conference was an excellent opportunity for education, networking, and research. The participants and group leaders worked together for five days in an area that was new to some of the group leaders and new to some of the participants which enabled us to learn about forest ecology around Kathmandu and Nagarkot, Nepal. The fieldweek was an excellent networking opportunity and the group leaders and participants bonded which strengthened international research in dendrochronology and continues to foster new research collaborations. All of the group leaders and participants had the opportunity to learn about tree-ring formation in Pinus roxburghii at 1500 masl elevation, to explore its wood anatomy, and to examine specific research questions in our field area. In the end we developed a better understanding of the stand-age structure of a stand of trees in Nagarkot, explored the erosion history from exposed roots, and investigated tree health issues on closely related sites. We found that P. roxburghii poses some dating issues with false and micro rings at this elevation, but we were still able to develop a tree-ring chronology from this species and make preliminary assessments of stand dynamics and health. [ABSTRACT FROM AUTHOR]

Variations of stable isotopes ratios in tree rings are indicators of climate fluctuations. The current study examines the relationships between precipitation and temperature variations and stable oxygen isotopes ratios ( δ 18 O) of the last 50 years in cellulose extracted from growth rings of Juniperus polycarpus and Quercus macranthera in northern Iran. We sampled at high-elevation sites in the Alborz Mountains, where J. polycarpus covers south-facing slopes and Q. macranthera covers north-facing slopes, respectively. δ 18 O values of tree-ring cellulose in oak and juniper show site-specific differences in their mean and standard deviation, but temporal variations are significantly correlated, indicating a common forcing. Correlation functions of tree-ring δ 18 O with local and modelled climate data reveal positive effects of temperature on δ 18 O values in J. polycarpus during January–June, with significant correlations in January and May. Moreover, juniper δ 18 O is influenced by winter precipitation, probably due to an influence of snow melt on the isotopic composition of soil water during spring. Negative correlations were found between juniper δ 18 O and early vegetation period precipitation, when new xylem cells are formed. In contrast, δ 18 O of oak contains a late summer (September) precipitation signal. Besides, δ 18 O values in oak are positively affected by temperatures during summer and winter, with strongest connections with temperatures of September during the previous and current growing seasons. By combining stable isotope signals of species growing under different site conditions, there is a potential to reconstruct moisture variations during different seasons in the mountain areas of north Iran. [ABSTRACT FROM AUTHOR]

Extreme climatic events such as droughts are likely to result in huge and long-lasting effects on regional ecosystem health if large numbers of foundation tree species continue to die. Although deforestation is severe in the Ethiopian highlands, some remnants of dry afromontane forests still exist. However, the resilience of these forests under climate change scenarios is unknown. Therefore, we studied (1) the extent and spatial patterns of standing dead stems along an elevational gradient and (2) the effects of dieback on forest carbon sequestration potential and aboveground carbon stocks, in Juniperus procera and Olea europaea dominated dry afromontane forest in northern Ethiopia, using allometric models combined with tree ring analysis. Juniperus procera and Olea europaea constitute 67% of the total tree population. Tree dieback affected a quarter of the total population. This loss is critical because 92.2% of snags belong to J. procera and O. europaea , which are the foundation species of the study forest. The total estimated mean aboveground C-stock was 19.3 (±3.9) Mg C ha −1 . Of this estimate, snags contributed 34.5% of total C-stock. The estimated annual C-sequestration potential of the study forest was 0.33 (±0.03) Mg C ha −1 year −1 , which is 27% less when compared to the pre-tree dieback C-sequestration potential. We found a decreasing trend in tree dieback with increasing elevation, which implies that the aboveground C-stocks and climate change mitigation potentials of the forest, was highly affected at lower elevations which is the drier part of the landscape. Tree ring analysis showed that trees reach medium-sized stem diameter (i.e., 20–25 cm) after no less than 100 years, indicating that the effect of forest dieback on C-sequestration potential and ecosystem function is long-lasting. Our results provide information on the magnitude of tree dieback and its long-lasting impact on forest carbon fluxes and forest ecosystem services. Evidently, the results substantiate the importance of protecting such forest to maintain the quality of the environment and to reduce efforts and cost for forest restoration after major loss. Finally, the information gained by this study provides baseline information for comparison of future carbon sequestration estimates. [ABSTRACT FROM AUTHOR]

The response of plant species to varying climate conditions in tropical Africa remains poorly understood but can be assessed using wood anatomical traits. These traits play an important role for the adaptive capacity of a species to environmental stress, since environmental conditions can modify the proportion, size, and morphology of wood anatomical elements. This study reports quantitative data on vessel characteristics of the diffuse porous angiosperm Spiny monkey orange (Strychnos spinosa Lam.) in Benin in tropical West Africa. The vessel-related anatomical traits varied with high amplitude (coefficient of variation CV ˃ 25%) between different sites located in different climate zones. The variability of the traits is higher within one climatic zone than between climatic zones, and even more pronounced within trees. Consequently, the climatic zones have less influence on the studied features than local site conditions. However, the study showed that S. spinosa individuals that have numerous vessels also have a high lumen fraction and total ring area. On the other hand, individuals presenting a high vessel density also display vessels of smaller size. The correlation between vessel number and total ring area on the one hand, and between vessel size and lumen fraction on the other hand are highly significant and positive. In Benin, S. spinosa wood anatomical traits are likely linked to local site factors rather than to regional climatic factors. [ABSTRACT FROM AUTHOR]

Highlights: [•] Trees in Africa may form annual rings and grow to multicentury age. [•] Dendroecology helps to reconstruct climate trends and atmospheric circulation patterns. [•] Tree rings can fill the knowledge gaps in ecosystem productivity and hydrological cycle. [•] It contributes to validation of climate models for improved climate scenarios. [•] Tree ring analyses can complement allometric models to estimate carbon. [ABSTRACT FROM AUTHOR]

• Radial growth of Abies delavayi in southwest China is mainly limited by high temperatures and low moisture availability. • Tree growth rate of A. delavayi has been declining since the 1950s, accompanied with a remarkable increase of iWUE. • Xylem stable carbon (δ13C) and oxygen (δ18O) isotopic composition shifted to higher values from cold to warm years. • Growth declines of A. delavayi were driven by increasing drought stress and stomatal closure under a warming climate. Long-term tree growth trends and physiological responses to environmental changes, i.e., climate warming, and the rise of atmospheric [CO 2 ] (C a), need to be investigated across diverse forest ecosystems. We detected long-term trends in tree growth and δ13C derived intrinsic water use efficiency (iWUE) of Abies delavayi in the Cangshan Mountains, at its southern distribution edge in the Hengduan Mountains in southwestern China. We applied a dual-isotopic approach (δ13C, δ18O) to detect the shifts of tree physiological responses (photosynthetic, stomatal conductance) from colder to warmer conditions. Annual basal area increment (BAI) of A. delavayi in the Cangshan Mountains was decreasing since the 1950s, whilst the declining trend of tree growth was not obvious during the earlier period (1800–1951) after removing tree age- and size-related growth signals. Tree growth correlated negatively with temperatures and positively with relative humidity and self-calibrated Palmer drought severity index (scPDSI) during the early growing season (February to June), indicating a predominant growth limitation by moisture availability. Leaf inter-cellular [CO 2 ] (C i) derived from tree-ring δ13C of A. delavayi increased over time, with a rate slower than atmospheric C a rise, resulting in a decrease in the C i /C a ratio. Intrinsic water-use efficiency (iWUE) was increasing, especially after the 1950s. Dual-isotopic analyses revealed a reduction of stomatal conductance and stable or declined photosynthetic assimilation under warmer and drier environmental conditions. Recent growth decline of A. delavayi in the Cangshan Mountains was mainly related to the increase of warming-mediated drought stress and the resulting stomatal closure, while a positive effect of CO 2 fertilization was diminished under warming and drying environmental conditions. Our results serve as an early warning for tree growth and productivity of A. delavayi forests at the southern distribution limits under the ongoing warming climate. [ABSTRACT FROM AUTHOR]

Abstract: Podocarpus falcatus is an indigenous evergreen conifer species of tropical mountain forests in southeastern Ethiopia, showing potential tree ages of around 500 years. To study the influence of seasonal climate on the growth pattern of P. falcatus, we combined high-resolution electronic dendrometer measurements with wood anatomical investigations of microcores from the outermost stem parts collected in monthly intervals. At any time of the year sufficient rain events are able to cause cambial activity in P. falcatus. This permanent growing readiness leads to irregular wood formation with the formation of intra-annual density fluctuations and missing rings. Wood anatomical studies of microcores collected around the circumference of a mature P. falcatus revealed locally different activity status of the cambium on different lobes of the stem. Tree-ring width measurements of stem disks resulted in tentative tree ages that were confirmed by radiocarbon dating of selected wood samples. Although our efforts to cross-date ring-width series from several stem disks were not successful, further sampling in areas with different rainfall regimes, additional radiocarbon dating and measurements of stable isotopes hopefully would enable the establishment of a multi-century-long tree-ring series for climate reconstruction. [Copyright &y& Elsevier]

Abstract: Improved understanding of tree-growth responses to climate is needed to model and predict forest ecosystem responses to current and future climatic variability. We applied dendroclimatological techniques to assess the effects of inter-annual climate variations on radial growth of high-elevation conifers in the central Hengduan Mountains, southwestern China. Eight tree-ring width chronologies of the major tree genera Abies and Picea that are aligned along an elevation gradient from 3200 to 4200m a.s.l. were developed. Correlation and principal component analyses for the eight chronologies identified three groups of sites, representing different patterns of growth–climate relationships. Correlation and redundancy analyses with regional climate data revealed that radial growth of fir growing at high-elevation sites is enhanced by normal or warm summer temperatures (June and July) during the current growing season. In addition, radial growth of trees growing from high to middle elevations is sensitive to low temperatures during winter season. At low-elevation sites, trees display low sensitivity to temperature variation. However spring moisture availability becomes crucial for radial growth regardless of tree species. High- to middle-elevation conifers in the central Hengduan Mountains may benefit from the current climate warming, especially from rising winter temperatures. [Copyright &y& Elsevier]

Abstract: We developed five tree ring-width chronologies from one fir (Abies georgei) and four spruce (Picea brachytyla) stands near the upper treeline in the central Hengduan Mountain, northwestern Yunnan, China. Similar growth patterns and significant correlations are embodied among the five chronologies. A principal component analysis for the four spruce chronologies indicated that the first component accounts for 54.8% of the total variance over the period 1750–2003. Climate–growth response analysis revealed that radial growth is mainly controlled by temperature variations, especially in the winter season. The first principal component of the spruce chronology network accounts for 43% of the annual mean temperature (from previous October until September) variance during the common period 1959–2003. By using a linear regression approach, we reconstructed annual mean temperature for the past 250 years. The reconstruction shows that the central Hengduan Mountain experienced some cool episodes during the 1810s, 1860s, and during 1960–1980. Warm intervals occurred during the 1780s, 1850s, 1940–1960 and in the past two decades. These general patterns are in general accordance with other records from nearby regions. [Copyright &y& Elsevier]

Abstract: Dwarf shrubs cover large areas above the upper tree line in mountain areas. Their potential for dendroecological analyses has not yet been explored comprehensively. In order to study the growth reactions of dwarf shrubs on the impact of environmental factors the ring widths of Empetrum hermaphroditum were measured. We analysed dwarf shrubs along micro-topographic and altitudinal gradients in the continental Norwegian Scandes. Beside ring width, basal area increments were measured and serial sectioning was implemented to evaluate growth variability and cross-dating reliability. E. hermaphroditum shows highly individual growth histories. Thus, cross-dating of growth curves is restricted to several radii within an individual and to mean curves of individuals growing at the same micro-site. Wedging rings and missing rings as well as eccentricity and asymmetric geometry of the stem constrict the synchronisation of growth curves. However, varying micro-site conditions are clearly reflected by differences in the mean growth rates and the frequency of frost rings. [Copyright &y& Elsevier]

• Quantifying climate change impacts on forest attributes of selectively logged neotropical forests. • Validating simulation results with field data. • Repeated logging led to degradation of forests for most climate change scenarios. • Assuming severe climate change (RCP 8.5), timber yields decreased by ca. 40%, regardless of applied rotation cycles. • Logging damages should be reduced to maintain carbon storage and timber supply. Logging is widespread in tropical regions, with approximately 50% of all humid tropical forests (1.73 × 109 ha) regarded as production forests. To maintain the ecosystem functions of carbon sequestration and timber supply in tropical production forests over a long term, forest management must be sustainable under changing climate conditions. Individual-based forest models are useful tools to enhance our understanding about the long-term effects of harvest and climate change on forest dynamics because they link empirical field data with simulations of ecological processes. The objective of this study is to analyze the combined effects of selective logging and climate change on biomass stocks and timber harvest in a tropical forest in French Guiana. By applying a forest model, we simulated natural forest dynamics under the baseline scenario of current climate conditions and compared the results with scenarios of selective logging under climate change. The analyses revealed how substantially forest dynamics are altered under different scenarios of climate change. (1) Repeated logging within recovery times decreased biomass and timber harvest, irrespective of the intensity of climate change. (2) With moderate climate change as envisaged by the 5th IPCC Assessment Report (representative concentration pathway 2.6), the average biomass remained the same as in the baseline scenario (−1%), but with intensive climate change (RCP 8.5), the average biomass decreased by 12%. (3) The combination of selective logging and climate change increased the likelihood of changes in forest dynamics, driven mainly by rising temperatures. Under RCP 8.5, the average timber harvest was almost halved, regardless of the logging cycle applied. An application-oriented use of forest models will help to identify opportunities to reduce the effects of unwanted ecosystem changes in a changing environment. To ensure that ecosystem functions in production forests are maintained under climate change conditions, appropriate management strategies will help to maintain biomass and harvest in production forests. [ABSTRACT FROM AUTHOR]

• We developed a new ring-width chronology (227 years) of shrub Rhododendron (R. campanulatum) from the central Himalaya. • Minimum winter temperature is the most important factor that determines radial growth of Rhododendron shrubs. • Cool-warm episodes in the central Himalaya coincide with other regional temperature records from the Himalaya and vicinities. • Winter temperature in the central Himalaya is teleconnected with the December-February India-Burma trough. • The shift in winter temperature during recent decades coincides with continental-scale warming. Himalayan Mountains provide unique opportunities for the extension of shrub-ring based dendroclimatology beyond the upper tree limit. However, little is known about limiting climate factors of shrub growth under harsh environmental conditions. We established a new ring-width chronology of a Himalayan shrub rhododendron (Rhododendron campanulatum D. Don) at the upper Krummholz treeline in the Mt. Gaurishankar massif, central Himalaya, Nepal. Bootstrapped correlation analysis showed positive relationships between radial growth and temperatures of all months from previous November to current October. Correlations were the highest with winter (December-February) minimum temperature (r = 0.781, p < 0.001), indicating that radial growth of R. campanulatum is strongly sensitive to winter minimum temperature. The linear regression model explained 61 % of the actual winter minimum temperature variance during the calibration period 1960–2013. Periods of low and high minimum winter temperatures in the central Himalaya were consistent with cool and warm episodes found by other regional winter temperature reconstructions from the Himalayas and the Tibetan Plateau. Spatial correlation analysis with land surface temperatures revealed the spatial representativeness of our reconstruction for a larger geographical territory over the Himalayas and the Tibetan Plateau. Furthermore, winter temperature in the central Himalaya is teleconnected with the December-February India-Burma trough. The persistent increasing winter temperature in recent decades in the central Himalaya coincides with continental-scale warming. Alpine vegetation in humid regions of the Himalayas may benefit from winter warming via an earlier start and extension of the growing season, as long as moisture availability is sufficient. [ABSTRACT FROM AUTHOR]

Dendrometers are vital tools for studying the response of trees to intra-annual environmental changes in different temporal resolutions, ranging from hourly, daily to weekly time resolution. Dendrometers are increasingly used in forest management and tree physiological studies. Besides the data analysis, data processing is also challenging, time-consuming and potentially error-prone due to the immense number of measurements generated by self-registering electronic dendrometers. We present the package 'dendRoAnalyst' based on R statistical software to process and analyse dendrometer data using various approaches. This package offers algorithms for handling and pre-cleaning of dendrometer data before the application of subsequent data analytical steps. This includes identifying and erasing artefacts in dendrometer datasets not related to actual stem circumference change, identifying data gaps within records, and the possibility of change(s) in temporal resolution. Furthermore, the package can calculate different daily statistics of dendrometer data, including the daily amplitude of tree growth. The package dendRoAnalyst is therefore intended to facilitate researchers with a collection of functions for handling and analysing dendrometer data. [ABSTRACT FROM AUTHOR]

• Annual radial increment growth of Afzelia africana was similar across climatic zones. • High rainfall increases tree height growth and xylem vessel size while reduces vessel density. • High arid conditions reduce tree height and xylem vessel size while increase vessel density. • Complex environmental factors drive tree growth and xylem anatomical adjustments of Afzelia africana. Tropical West African savannas are exposed to high climatic variability with potential impacts on tree growth, forest dynamics and ecosystem productivity. In such context, understanding the long-term ecological responses of savanna trees to changing environmental conditions is of great relevance for taking appropriate conservation actions. We conducted the first study on tree-ring analysis and quantitative wood anatomy on Afzelia africana Sm. in Burkina Faso, to investigate the life-span growth trajectories and wood anatomical adjustment to site and to climate variations. A total of 24 stem discs was collected in four protected forests along the Sudano-sahelian and the Sudanian climatic zones. Wood samples were analyzed using standard dendrochronological methods and quantitative wood anatomy. The mean annual growth rates varied from 1.002 (± 0.249) mm. year−1 in the Sudanian zone to 1.128 (± 0.436) mm. year−1 in the Sudano-sahelian zone. Analysis of growth trajectories showed high variations within sites and between climatic zones. Wood anatomical traits significantly varied between sites. Principal Component Analysis revealed strong relationships between ring width, wood density and vessel traits, with 82.81 % of the total variance explained. Vessel size significantly increased from the pith to the bark, highlighting the ontogenetic effects on xylem anatomical variations. Inverse relationships were found between vessel size and vessel density across the driest site and the wettest site, suggesting that the higher the rainfall, the taller the tree, the larger vessel size, but the lower vessel density. By contrast, more arid conditions and high evapotranspiration lead to smaller vessel sizes and higher vessel density. Such anatomical adjustments highlight the trade-offs between water conductance efficiency and hydraulic safety, and emphasize physiological responses to climate variability. These variations on the long-term dynamics and xylem anatomical patterns underline complex interactions between ontogenetic effects and contrasting environmental factors that affect the eco-physiological functioning of A. africana throughout the Sudanian region. [ABSTRACT FROM AUTHOR]

• Summer temperature is the most important climatic factor to determine radial growth of Himalayan fir. • Himalayan fir showed an elevational trend in tree radial growth response. • Tree growth is increasingly limited by spring moisture availability at low-to-middle elevations with ongoing climate change. • No obvious temporal shift has been observed in temperature sensitivity of Himalayan fir. A better understanding of growth-climate responses of high-elevation tree species across their distribution range is essential to devise an appropriate forest management and conservation strategies against adverse impacts of climate change. The present study evaluates how radial growth of Himalayan fir (Abies spectabilis D. Don) and its relation to climate varies with elevation in the Manaslu Mountain range in the central Himalaya. We developed tree-ring width chronologies of Himalayan fir from three elevational belts at the species'upper distribution limit (3750−3900 m), in the middle range (3500−3600 m), and at the lower distribution limit (3200−3300 m), and analyzed their associations with climatic factors. Tree growth of Himalayan fir varied synchronously across elevational belts, with recent growth increases observed at all elevations. Across the elevation gradient, radial growth correlated positively (negatively) with temperature (precipitation and standardized precipitation-evapotranspiration index, SPEI-03) during the summer (July to September) season. However, the importance of summer (July to September) temperatures on radial growth decreased with elevation, whereas correlations with winter (previous November to current January) temperatures increased. Correlations with spring precipitation and SPEI-03 changed from positive to negative from low to high elevations. Moving correlation analysis revealed a persistent response of tree growth to May and August temperatures. However, growth response to spring moisture availability has strongly increased in recent decades, indicating that intensified spring drought may reduce growth rates of Himalayan fir at lower elevations. Under sufficient moisture conditions, increasing summer temperature might be beneficial for fir trees growing at all elevations, while trees growing at the upper treeline will take additional benefit from winter warming. [ABSTRACT FROM AUTHOR]

Precise knowledge how tree growth will respond to future climate change is essential for the adapted management of forest ecosystems. By conducting sensitivity tests, tree-ring process-based cambial growth models can provide an innovative way to better understand wood formation under different climate change scenarios. As a case study in semi-arid north central China, we used artificially increased or decreased daily climatic data as input to the Vaganov-Shashkin dynamic growth model to investigate the response of wood formation to climatic change. By calibrating the tree-ring model using daily climate data over the period 1951–2010, we found that 81% of radial growth was driven by soil moisture, while 13% of growth was controlled by temperature. During the main growing season June–August, significant differences in the integral growth rate occurred after changing precipitation by ± 30% or by decreasing temperature by 3.0 °C (p < 0.05). However, increasing temperature showed only modest effects on tree radial growth rate. During the past 60 years, a significant advancement of the starting dates of growth was detected, whereby non-significant variability was found for the ending dates of growth. Contemporaneously, the effect of previous winter temperature (previous December to current January) on cambial growth initiation declined after 1980. Significant differences in the growth onset dates only occurred when temperature was reduced by 4.5 °C or increased by 5.5 °C. Moreover, both the onset and ending dates of growth in the study region were more sensitive to cooling rather than to warming. If temperature will increase by 2°C and precipitation will increase by 30% at the end of this century as predicted by some Earth system models, tree radial growth might increase by 19% in the study region, compared to the average during the period 1952–2010. Consequently, tree stem radial growth is expected to increase under a warming and wetting climatic scenario, but will decrease under drying conditions. [ABSTRACT FROM AUTHOR]