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As climate niches of most tree species are projected to shift rapidly in the coming decades, forest-assisted migration (FAM) of populations from warmer sites is a promising silvicultural tool to help forests adapt to global changes. However, additional knowledge on species-specific local genetic adaptation and phenotypic plasticity is needed to inform the deployment of FAM in forest management. Here we applied a novel dendroecological approach to a unique network of ten 60 year-old provenance trials covering a large climate gradient in eastern Canada to assess the FAM potential of red spruce, a species unique to the Acadian-Wabanaki forest region projected to decline under climate change. We first controlled for non-climatic growth drivers by applying a Bayesian hierarchical model to individual, annual tree growth records extracted from tree-rings. Non-climatic variables explained 75.6 % and 92 % (posterior mean Bayesian R2) of tree-level and site-level growth, respectively. Across populations and sites, residual annual growth displayed the strongest correlations with summer climate, with growth declines during warm and dry summer conditions. In contrast with summer patterns, warmer and drier spring conditions were generally favorable to growth, while winter temperatures had only marginal associations with growth. To test the hypothesis that red spruce populations from warmer locations are good candidates for assisted migration, we assessed significant changes in climate-growth correlations as a function of climate transfer distance, calculated as the differences between population origin climate and climate at each trial site. We found that trees moved to colder sites, which simulates standard FAM practices, were significantly less sensitive to summer water deficit and changes in precipitation. However, additional variation in climatic sensitivity to summer temperature suggests potential risks at elevated transfer distances. Results from our application of dendroecology to existing provenance trials provides support for red spruce as a candidate species for FAM. • Forest Assisted migration (FAM) helps adjust forest composition to climate change. • FAM success requires that translocated trees outperform local populations. • We test the FAM potential of red spruce across a network of provenance trials. • Red spruce trees moved to colder sites were less sensitive to moisture stress. • Our results provide support for red spruce FAM. [ABSTRACT FROM AUTHOR]

Searching for drought tolerant species is one of the adaptative management measures that could be implemented to improve forest resilience in the context of more intense and frequent droughts brought be climate change. Western European forests are already suffering from drought-induced tree mortality, in native as well as in well-established non-native species. Novel non-native species (i.e., non-native species that have not yet undergone thorough operational testing or previously been grown at forestry scale) with high drought resistance in their original geographic range could be an alternative. To this end, the ecology and drought response of these species need to be investigated in their area of introduction. We applied a dendroecological approach on trees of Abies nordmanniana (Steven) Spach (AN), Chamaecyparis lawsoniana (A.Murray bis) (CL), and Thuja plicata Donn ex. D.Don. (TP) from Belgian arboreta (Western Europe). First, we identified the main climatic drivers of species radial growth, using Bootstrapped Correlation Coefficients between tree ring indices and climate indicators related to drought, heat, and cold stresses. Second, we assessed the species growth response to exceptional drought events, using resistance, recovery and resilience indices and an integrated index comparing the actual resilience to a theoretical full resilience. We investigated the effects of species and drought timing on these indices using linear mixed models. The radial growth of the three species was negatively influenced by the water deficit during the previous growing season (especially in fall and summer), lower precipitation in the previous October, colder temperatures in late winter-early spring, and lower minimal temperatures in May. TP is the most sensitive species to previous summer conditions as it was negatively affected by the number of days with a mean temperature above 30°C, while AN was the least sensitive species with no significant Bootstrapped Correlation Coefficients for previous summer precipitation and temperatures. AN and TP differed from CL in being negatively affected in spring by higher maximal temperatures versus lower precipitation respectively. The effects of species and drought timing on resistance and recovery were significant. Overall, early and whole growing season droughts had a stronger negative effect than late droughts. AN and CL were more resistant to early and late droughts than TP, while the opposite was observed for recovery. The species showed less pronounced differences in resilience. CL was the species the closest to the theoretical full resilience, followed by AN: these two species appear to be good candidates for improving drought resistance of Western European forests. However, one must not forget that introducing novel species is associated with ecological risks and a thorough assessment of these risks must be carried out before promoting these species in forestry. Future research could focus on a comparison of novel non-native species with already well-established species in Western Europe such as Norway spruce and Douglas fir and explore how AN, CL and TP interact with native species in mixed stands. [ABSTRACT FROM AUTHOR]

• Tree radial growth rates follow an unimodal pattern along the radius gradient. • Ontogenetic growth trends constrain the response of tree radial growth to climate. • Growth-lifespan trade-offs of trees are inherent and determined by growth kinetic mechanisms. Tree radial growth records both ontogenetic growth trends and environmental information. Although the former is usually excluded from climate-growth analyses, its gradual changes have a more profound effect on forest carbon sequestration. Elucidating the kinetic mechanism behind this intrinsic trend will greatly improve our understanding and prediction of climate-growth relationships. The iterative growth model (IGM) and its extensions link organism growth, lifespan, and respiration, providing important insights into this trend. Here, we extended the IGM to the tree-ring scale (IGMR) and used tree-ring width datasets across the Northern Hemisphere to analyse the constraints of tree ontogenetic growth trends on radial growth rate (along the radius gradient). On this basis, we further elucidated the convergence and differentiation of these growth trends across different climate types and clades. The results showed that: (i) ontogenetic growth trends of trees cause the radial growth rate to follow a typical unimodal pattern along the radius gradient. (ii) This unimodal pattern is a function of tree radial size, metabolic exponent, and maintenance metabolic rate, constraining the response of tree radial growth to climate. (iii) Ontogenetic growth trends result in an inherent trade-off between tree radial growth rate and lifespan. In conclusion, different growth drivers do not alter the constraining effect of tree size on radial growth. Ontogenetic growth trends should be considered in future studies of climate-growth relationships. [Display omitted] [ABSTRACT FROM AUTHOR]

• A wearable FBG sensor with a flexible clamp has been developed to monitor the corn growth. • Averagely corn ear grows 1.25 mm axially and 5.41 mm radially over a period of 72 h. • Both axial and radial growth were estimated with sensitivity of 0.01 and 0.04 nm/mm. • The experimental data and theoretical growth model presented an R2 of 0.9954. • Wearable FBG sensors non-invasively monitored corn ear growth over extended periods. Modern plant physiology and environmental factor quantification technologies rely on non-contact spectroscopy, airborne/satellite photography, and machine vision. Unfortunately, many plant health monitoring systems lack spatial and temporal resolution, continuous, dependable data, and the ability to track plant health or understand how biological and environmental factors influence plant growth. Some current methods are insufficient for real-time crop monitoring due to electromagnetic interference and biocompatibility. This paper presents a novel fiber Bragg grating (FBG) sensor system with flexible silicone clamps for monitoring corn ear growth over time. To measure the axial growth distance, a camera takes images of the corn ears at the same time, while a graduated circular tower is developed to measure the radial dimensions. To investigate how environmental conditions influence corn development, a unique circuit board was created to monitor temperature, humidity, and light intensity. In this experiment, the FBG sensor system was designed to measure corn ear axial and radial growth for 72 h. The experimental results demonstrate that on average the corn ear grows 1.25 mm axially and has a sensitivity of 0.01 nm/mm. Furthermore, the slope of the fitted line (= 0.04 nm/mm) indicates the radial clamps sensitivity, with an average increase in corn ear girth of 5.41 mm. This study used a low-cost integrated flexible silicone clamp to hold the FBG sensor without impeding plant growth. As a result, even in challenging field conditions, the sensor can monitor the axial and circumferential growth of corn ears. These discoveries will aid in the adoption and improvement of cutting-edge technology in smart agriculture applications, providing important data for crop yields and agricultural advantages. [ABSTRACT FROM AUTHOR]

• Dendrochronology was used to compare the radial growth of healthy and decayed fir. • Both fast growing and slow growing trees of fir are susceptible to decay. • In warm and humid areas the radial growth of decayed fir is limited. • Healthy fir trees are more climate-responsive than decayed ones. The forest loss and degradation caused by tree heart rot presents an increasingly challenging issue for the protection and utilization of forest resources. Yet, it is questionable whether heartwood-decayed trees can still function on par with healthy trees. Here, using tree ring data, we established basal area increment (BAI) series of healthy and heartwood-decayed fir trees at four sites (Abies spectabilis in Bomi; A. georgei Orr in Deqin as well as the Sygera Mountain; A. fabri Craib in Yajiageng) in the southeastern Qinghai-Tibetan Plateau (QTP). We conducted a comparative analysis of the difference in the BAI, response to climate factors and elasticity under environmental stress between the healthy and decayed fir. The results show that, in QTP, fir susceptibility to decay is uncorrelated with growth rates. However, after decaying occurs in fir trees, their radial growth is restricted in warm and humid areas (i.e., at Bomi and Yajiageng). The average BAI of healthy fir is 70.32 % and 86.32 % higher than that of decayed fir in Bomi and Yajiageng respectively (p < 0.01), but no significant difference in Deqin and Sygera (p > 0.05). Moreover, healthy fir exhibits a more pronounced response to climatic conditions. Almost all BAI series of healthy and decayed fir in the southeastern QTP is positively correlated with the temperature and vapor pressure deficit. Under temperature stress, decayed fir trees are less resistant at three sites. This empirical study supports that there is no correlation between conifer trees' radial growth rate and their likelihood of heartwood decay, and provides a compelling explanation for the constrained growth of decayed fir trees. Our findings can bolster the accurate assessment of carbon sinks and the conservation of forest resources in regions prone to high-decaying risks. [ABSTRACT FROM AUTHOR]

Forests, especially in the northern latitudes, are vulnerable ecosystems to climate change, and tree-ring data offer insights into growth-climate relationships as an important effect. Using the National Forest Inventory plot network, we analysed these correlations for the two dominant conifer species in Norway – Norway spruce and Scots pine – for the 1960–2020 period. For both species, the June climate was an important driver of radial growth during this period. Countrywide, the climate-growth correlations divided the Norwegian forests into spatial clusters following a broad shift from temperature- to water-sensitivity of growth with latitude and altitude. The clusters were delineated by a mean 1960–2020 June temperature of ca. 12°C for Norway spruce and Scots pine. The annual mean growing season and July temperatures – but not June temperature – has increased by 1.0 °C between the 1960–1990 and 1990–2020 periods, with a slight increase in precipitation. Despite this warming and wetting trend, the long-term growth-climate relationship has remained relatively stable between 1960 and 1990 and 1990–2020 for both species. The threshold between temperature and water-sensitive growth has not changed in the last two 31-year periods, following the stability of the June temperature compared with other months during the growing season. These findings highlight geographically coherent regions in Norway, segregating between temperature- and water-sensitive radial growth for the two major conifer species, temporally stable in the long-term for the 1960–2020 period studied. • Growth-climate correlations were assessed in spruce and pine in Norway. • June climate was the main driver of radial growth in the last 60 years. • Results spatially clustered along a temperature- to water-sensitivity gradient. • Climate-growth relationships have remained stable despite a warmer growing season. [ABSTRACT FROM AUTHOR]

The study of charcoal from archaeological sites often focuses on merely the identification of taxa. However, the anthraco-typological analysis of oak charcoal offers extensive evidence about the wood diameter, growth pattern, and minimum age of the trees selected for harvest. This in turn gives valuable data on palaeoecology and woodland management. This review focuses on early stage results from oak charcoal remains from three early medieval rural sites in eastern England, dating from the 5th to the 9th century AD. Over 200 fragments of oak charcoal were selected and examined to identify the size class of the wood, the growth patterns and whether the wood was sapwood or heartwood. This has then given evidence of timber and fuel wood collection strategies and woodland management regimes. The data has provided additional evidence on the nature of the sites' features. Furthermore, the analysis has allowed comparisons to be drawn between the three contemporary sites, as well as to expand the archaeobotanical record to a more detailed understanding of the environment around these settlements. Exceptional material from the early medieval site of Flixborough has allowed a unique insight into the selection of timber and possible long-term woodland management strategies undertaken in the area during the mid 8th to 9th century AD. The results will be discussed regarding the economic and environmental context, demonstrating the value of dendro-anthracological tools in adding additional detail and a new understanding of these sites. [ABSTRACT FROM AUTHOR]

Drought stress caused by global climate warming affects tree growth in both dry and wet areas. However, the differences in tree growth responses to drought in dry and wet areas are poorly understood. Here, we collected 93 tree cores to analyze the differences in the radial growth responses of larch (Larix gmelinii) under climate change and tree growth resilience under drought events in the Altai Mountains (dry area) and Changbai Mountains (wet area). The results showed that larch growth in the Altai Mountains was significantly positively correlated with the self-calibrating Palmer Drought Severity Index (sc-PDSI) in all months and precipitation in the previous growth season and May, whereas it was significantly (p < 0.05) negatively correlated with temperature in May and the previous June to August. In the Changbai Mountains, larch growth was significantly positively correlated with May maximum and mean temperature, and significantly positively and negatively correlated with precipitation in April and May，respectively (p < 0.05). The mean resistance (recovery) of larch growth to drought in wet areas were significantly stronger (weaker) than that in dry areas (p < 0.05). Moreover, strengthening the drought frequency led to a significant (p < 0.05) decline in larch resistance in dry areas. Therefore, warming-induced increases in drought stress will aggravate negative impacts on the radial growth of larch forests in temperate dry areas but not in wet areas in the future. [ABSTRACT FROM AUTHOR]

• High values of radial growth rate for A. niger strains. • Valorization of corn cob for endoglucanase production by SSF. • High purification of endoglucanase by FPLC. Agro-food by-products contain valuable nutrients which are wasted. In this work, solid-state fermentation (SSF) was carried out using corn cob as substrate for endoglucanase production. The radial growth of three fungal strains - Trichoderma harzianum T104, Aspergillus niger GH1 and Aspergillus niger NRRL3- was analyzed in order to select the most appropriate. Radial growth data were analyzed with a mixed linear model for longitudinal data and no statistically significant differences were found between both A. niger strains. Endoglucanase was separated from the extract of A. niger GH1 by fast protein liquid chromatography (FPLC).The highest endoglucanase activity was detected in fraction number three collected from FPLC corresponding to 72 h of SSF. Seven bands in a range from 24 to 50 kDa, which correspond to endoglucanase from fungal extract, were detected by zymogram analysis. According to protein quantification performed by the ImageJ software, 85% of the proteins present in the samples collected by FPLC corresponded to endoglucanase proteins. The purified endoglucanase retained about 100% of its catalytic activity at 30 °C and 50 °C and was stable in a pH range between 4.00-6.00. These properties make this isolated enzyme suitable for industrial applications such as the saccharification process for bioethanol production. [ABSTRACT FROM AUTHOR]

Abstract Forests are sensitive to climate change at high altitude and high latitude. Dahurian larch (Larix gmelinii Rupr.) has experienced an unprecedented forest retreat northward during the last century. Whether the response of growth to climate has dissimilar patterns at different altitudes, and what the "altitudinal trends" of forest development will be in the future, remains unclear. We dendroclimatically investigated the impacts of climate change on the growth of larch forests along an altitudinal gradient. In total, 721 trees from 25 forest stands, representing an altitudinal range from 400 to 950 m a.s.l. in the Great Xing'an Mountains, northeast China, were sampled and used to develop tree-ring width chronologies. The results suggest that warming caused a decline in larch growth at low altitude, while tree growth increased at high altitude. The growth–climate relationships indicate that October–February temperatures were positively correlated with larch growth at low- and high-altitude sites, but negatively correlated at medium-altitude sites (ca. 600–700 m a.s.l.). April–May (early spring) temperatures and October–January precipitation had positive effects on growth in general (ca. 75% of all sites). The effects of summer temperature/precipitation on larch growth at high-altitude sites were opposite to that at low-altitude sites. This change of response from significantly positive/negative correlation to significantly negative/positive correlation occurred gradually along the altitudinal gradient. The relationships varied significantly with altitude both in the case of temperature (R 2 = 0.425, P < 0.001) and precipitation (R 2 = 0.613, P < 0.001). The shift in response of larch forest to changes in summer temperature and precipitation occurred in the areas with a mean annual temperature of ca. −4 °C and ca. −5 °C, respectively; larch growth at temperatures lower or higher than these thresholds was limited by temperature and precipitation, respectively. Graphical abstract Unlabelled Image Highlights • The larch growth decline at low altitude and increase at high altitude. • Effects of summer temperature/precipitation on growth at high altitude was opposite to that at low altitude. • The response shift threshold of larch to temperature and precipitation of ca. –4 °C and ca. –5 °C, respectively. • The larch radial growth changed from the temperature limit at high altitude to the drought limit at low altitude. [ABSTRACT FROM AUTHOR]

• We report the first studies of tree growth dynamics of the SDTF of the Marañón valley. • Higher growth rates were found in Cordia iguaguana and Cedrela kuelapensis. • Cedrela kuelapensis presents high growth rates in relation to the congeneric species of the neotropical region. • Populations of endemic species in the area could be mainly of young individuals. Seasonally dry tropical forests (SDTF) currently occupy only 10% of the original area of their natural distribution. In the Marañón river valley, north western of Peru, occurs one of the most important SDTF of the neotropics. It has an endemic woody flora that represent 32% of the species, being threatened by its increasing fragmentation, and the knowledge of the ecology, forestry and conservation of the tree species is scarce. In this context this work presents the result of evaluation of the wood anatomy with emphasis to growth ring analysis, dating trees and stem growth rate determination of four tree species: Anadenanthera colubrina (Vell.) Brenan, Cedrela kuelapensis T.D. Penn. & Daza, Cordia iguaguana Melch. Ex I.M. Johnst., and Esenbeckia cornuta Eng., the last three being endemic and threatened with extinction. Our results determined that Cedrela kuelapensis showed the highest radial growth of the stem in relation to the other congeners of the neotropical region. Lower stem growth was observed for E. cornuta trees, according to the pattern of other tropical species. The results also indicate that populations of C. iguaguana and Esenbeckia cornuta in the zone are mainly composed by young trees exhibiting strong anthropic pressure due to the quality of their timber and, in consequence, more efforts are needed in the management of these resources to guarantee their sustainability. [ABSTRACT FROM AUTHOR]

A warmer climate will increase aridity and threaten forest persistence in xeric areas. This is the case of some Atlas cedar (Cedrus atlantica) forests showing recent growth decline, dieback and high mortality rates in North Africa. A lower resistance to drought, manifested as stronger growth loss, could increase the drought-related mortality risk in these forests as has been found for gymnosperms worldwide. It could be also expected that changes in dryness are linked to large-scale atmospheric circulation patterns such as the North Atlantic Oscillation (NAO). We tested these hypotheses by analyzing growth resilience indices (resilience, recovery, resistance) derived from tree-ring data. We sampled nine Atlas cedar plots located in north-western Algeria, where climate shifted towards drier conditions in the 1980s. In these forests, drier winters, associated to positive NAO phases, constrained tree growth and resistance, two outputs of the drought impact. During dry years, the resilience index decreased as elevation increased. The association between cedar growth resistance and drought severity is strengthening: the drier the climate conditions, the lower the growth resistance. Resistance also showed a significant higher temporal variability in 8 out of 9 plots as drought intensified. These findings have allowed identifying the increase in the temporal variability of growth resistance as a new early-warning signal of drought stress. • Aridification threatens NW-Algerian Atlas cedar forests causing growth decline. • Drought-induced decline could be caused by a long-term loss in resistance or resilience. • Cedar growth and resistance were constrained by long, severe droughts. • The association between cedar resistance and drought is strengthening. • Neither resistance nor resilience declined but showed higher variability as climate dried. [ABSTRACT FROM AUTHOR]

The adaptability of plantation ecosystems to climate change has become an important issue in many drylands worldwide. The plantation forests of the Loess Plateau, one of the driest areas in China, have greatly increased, and Picea crassifolia and Pinus tabuliformis are the dominant artificial coniferous species in this region. However, quantitative evaluations of the responses of radial growth to climate change for these two dominant artificial coniferous trees are rare. In this study, we collected tree-ring sample data from four sampling sites in Huajialing and Chankou in the arid Loess Plateau and analysed the radial growth of two artificial conifers and their climate response characteristics (precipitation, temperature, and standardised precipitation evaporation index (SPEI)) using Pearson correlation and the Climwin model. The results showed that (1) low precipitation during the growing season (April-August) and the resulting drought stress were major growth-limiting factors for plantation forests in the arid Loess Plateau, and this impact increased with the duration of drought stress. (2) P. tabuliformis was more susceptible to drought stress than P. crassifolia , and its soil water content at the 0–200 cm depth was already close to the wilting point. (3) The site conditions of planted areas, including initial planting density, elevation, and stand structure (canopy cover), significantly influenced the response of the same tree species to drought stress. (e.g., P. tabuliformis in high-density and low-elevation areas was more susceptible to drought stress than trees in low-density and high-elevation areas). We concluded that forest managers should select appropriate initial planting densities and altitudes and implement pruning and thinning measures at specific ages (15 years for P. crassifolia and 20 years for P. tabuliformis) based on basal area growth curves. Our results provide valuable information for the sustainable management of plantations against the background of climate warming. [ABSTRACT FROM AUTHOR]

Highlights • Tree-ring samples and inventory data were used to derive survival probabilities. • Characteristic U- and J-shaped mortality curves were found. • Implementation in a forest succession model yielded plausible results. • When uncertainties are considered, projections of forest dynamics become more robust. Abstract Tree mortality is caused by complex interactions between multiple biotic and abiotic factors. Processes of tree mortality that are not induced by natural disturbances are often reflected in distinct radial growth patterns of trees, which typically serve as reliable indicators of impending tree mortality. However, it remains unclear whether empirical mortality models that are based on tree size and growth result in more realistic projections of forest succession in dynamic vegetation models (DVMs). We used a combination of tree-ring and inventory data from unmanaged Swiss natural forest reserves to derive species-specific survival models for six Central European tree species (Abies alba , Fagus sylvatica , Larix decidua , Picea abies , Pinus cembra and Quercus spp.). We jointly used 528 tree-ring samples and inventory data from eight forest reserves. We implemented the estimated parameters of the survival models into the DVM ForClim and performed simulations of forest succession that were validated using the inventory data of the forest reserves. Size- and growth-dependent variables (i.e., diameter at breast height and mean ring width) over the last few years prior to tree death were reliable predictors to distinguish between dying and living trees. Very low mean ring widths over several preceding years as well as small and large trees, respectively, reflected low survival probabilities. However, the small sample sizes of small and large trees resulted in considerable uncertainty of the survival probabilities. The implementation of these survival models in ForClim yielded plausible projections in short-term simulations and for some sites improved the predictions compared to the current ForClim version. Stand basal area, however, tended to be overestimated. Long-term simulations of ForClim based on the empirical survival models resulted in realistic predictions only if the uncertainty of the predicted survival probabilities was considered. We conclude that the combination of different data sources in combination with the consideration of intra-specific trait variability yields robust predictions of tree survival probabilities, thus paving the way towards better tree mortality models and more reliable projections of future forest dynamics. [ABSTRACT FROM AUTHOR]

Climate extremes are predicted to become more frequent and intense in future. Thus, understanding how trees respond to adverse climatic conditions is crucial for evaluating possible future changes in forest ecosystem functioning. Although much information about climate effects on the growth of temperate trees has been collected in recent decades, our understanding of the influence of forest management legacies on climate-growth relationships is still limited. We used individual tree-ring chronologies from managed and unmanaged European beech forests, located in the same growth district (i.e. with almost identical climatic and soil conditions), to examine how forest management legacies (recently managed with selection cutting, >20 years unmanaged, >50 years unmanaged) influence the radial growth of Fagus sylvatica during fluctuating climatic conditions. On average, trees in managed stands had higher radial growth rate than trees in unmanaged stands during the last two decades a 50%. However, the beech trees in the unmanaged stands were less sensitive to drought than those in the managed stands. This effect was most pronounced in the forest with longest management abandonment (>50 years), indicating that the drought sensitivity of mature beech trees is in these forests the lower, the longer the period since forest management cessation is. Management-mediated modifications in crown size and thus water demand are one likely cause of the observed higher climate sensitivity of beech in the managed stands. Our results indicate a possible trade-off between radial growth rate and drought tolerance of beech. This suggests that reducing stem density for maximizing the radial growth of target trees, as is common practice in managed forests, can increase the trees' drought sensitivity. In the prospect of climate change, more information on the impact of forest management practices on the climate-growth relationships of trees is urgently needed. [ABSTRACT FROM AUTHOR]

Rising atmospheric CO 2 ( C a ) can increase tree radial growth by increasing intrinsic water-use efficiency (iWUE). However, the effects of age on the response remain unknown, particularly for forests in remote areas such as China’s Tianshan Mountains. Here, we assessed age-dependent growth trends of Picea schrenkiana using tree-ring data from low and high elevations and two detrending methods to detect robust long-term trends. We developed age-dependent relationships between basal area increment (BAI) and iWUE based on size-class isolation and separated the contributions of climate variables and iWUE to radial growth. The juvenile trees showed growth increases over time, versus growth reductions in two older age classes. An overall negative trend existed for combined data from all age classes and elevations. iWUE increased in response to increasing C a for trees in all age groups at low and high elevations, with higher values in near-mature and mature trees (100 yr < age ≤ 160 yr) at the lower sites. However, age affected radial growth and its responses to climate and iWUE. For juvenile trees (≤60 yr), BAI increased during the study period, temperature in May-July and iWUE all have positive effects on the radial growth with significantly high contribution variance from iWUE. The smaller hydraulic constraints in juvenile trees may permit higher photosynthetic rates, reduced climatic sensitivity, and increased growth by CO 2 fertilization. For older trees, BAI decreased, possibly due to stomatal closure caused by warmer temperatures and decreasing hydraulic efficiency with increasing tree age; thus, increased iWUE could not outweigh environmental stresses. The trees at high and low elevations responded consistently to environmental changes, but with different response intensity. Thus, climate and cambial age together determined whether increased iWUE could increase radial growth and the potential CO 2 fertilization effect. These age-dependent growth responses should be accounted for when assessing responses of forest dynamics to climate change. [ABSTRACT FROM AUTHOR]

Tree growth is a key ecosystem function supporting climate change mitigation strategies. However climate change may induce feedbacks on radial growth and wood density, affecting the carbon sequestration capacity of forests. Using a mixed modeling technique long-term trends in radial growth, wood density and above-ground biomass, defined as the product of the annual basal area growth with the wood density, of common beech ( Fagus sylvatica ) and sessile oak (Quercus petraea ) in the Belgian Ardennes, were determined and explained using climate drivers of change. This modeling strategy allowed us to determine if the same conclusions can be drawn when only BAI is considered, as is assumed in most carbon sequestration studies, when looking at long-term trends in carbon sequestration. The models indicate that above-ground biomass increment changes over time are more driven by changes in radial growth than by changes in wood density. Nevertheless, the assumption of constant wood density in most carbon sequestration studies is incorrect. Ignoring wood density results in an underestimation of long-term trends in above-ground biomass increment for beech, and an overestimation of above-ground biomass increment for oak. Interesting is that radial growth is mostly driven by climate variables of the current year, whereas wood density is more driven by the climate variables of the previous year. Beech radial growth and wood density is found to be negatively influenced by drought and positively by water availability. Oak radial growth and wood density is negatively affected by late frost and positively by water availability. The findings of this study suggest that radial growth in combination with wood density should be used in carbon sequestration studies as different climate driven long-term trends in radial growth and wood density are found. [ABSTRACT FROM AUTHOR]

With the intensification of climate warming, more frequent and hotter droughts are a significant risk to forest ecosystems around the globe, including temperate biomes. To accurately predict the response of forests to drought, it is necessary to provide comprehensive information on the resilience of tree growth, its spatiotemporal changes and drivers. This information is often lacking for broadleaf species in temperate regions. To fulfill this aim, we analyzed 3177 ring-width series from 1981 trees covering 40 sites for four dominant broad-leaf tree species (Fraxinus mandshurica, Phellodendron amurense, Juglans mandshurica , and Quercus mongolica) in temperate forests in northeastern China. We quantified the resilience (resistance and recovery) of tree growth to extreme droughts. Minimum temperatures in most seasons and warm conditions and drought stress in early summer were the main factors limiting growth. Among the four tree species, Q. mongolica had the weakest growth resistance to drought and the fastest growth recovery from drought. Juglans mandshurica had a significantly (p < 0.05) higher drought resilience than F. mandshurica and P. amurense. Tree resilience presented a clear spatial pattern driven by differences in site condition and local climate. The resistance (recovery) to drought decreased (increased) with increasing latitude and longitude, and increased (decreased) with elevation. Q. mongolica exhibited a decrease in resistance and increase in recovery through time, whereas the other three tree species showed the opposite pattern. Fraxinus mandshurica, J. mandshurica , and Q. mongolica had high resistance (recovery) in warmer-wetter (colder-drier) regions. In contrast, P. amurense had reduced recovery in cold sites and low resistance in warm sites. The resistance and recovery indices of these sympatric tree species confirmed that different tree species have distinct strategies to cope with drought that is influenced by tree condition and local environment. The influence of biogeographical factors is often more important than other factors and should be considered when studying forest resilience to drought. [ABSTRACT FROM AUTHOR]

• An earlier SoGS affects radial growth by regulating the cumulative growth rate. • The easing of low temperature restriction promotes radial growth in cold humid area. • Aridity counteracted the positive effect of temperature on radial growth in dry area. Climate change is profoundly affecting phenology, especially in the Northern Hemisphere. Nevertheless, how tree radial growth responds to phenological shifts remains to be explored. It is necessary to analyze the specific response process of tree growth to phenology. In this study, 61 tree-ring chronologies from Central Asia were used to analyze the effects of phenological shifts on tree radial growth. Based on previous studies and hydrothermal characteristics, we divided the study area into two parts, with 49° north latitude as the boundary. The results of the model-based simulation indicated an obvious advance to the start of growing season (SoGS) in the period from 1959 to 2010/2016. Correlation analyses showed that there were significant negative correlations between the SoGS and radial growth in the north of the study area but not in the south. Path analyses indicated that radial growth between north and south did not respond consistently to the earlier SoGS. In the north, radial growth mainly benefited from the alleviation of low temperature limitations, thereby elevating the cumulative growth rate. But in the dry south, aridity stress in the early growing season counteracted the positive effect of temperature on tree radial growth through decreasing the cumulative growth rate. In general, we determined that an earlier SoGS influences tree radial growth by regulating the cumulative growth rate. This study provides a theoretical basis for promoting the accurate assessment of carbon sink potential on a larger scale and for predicting forest dynamics. [ABSTRACT FROM AUTHOR]

Past and present environmental changes cause significant changes in tree growth in many parts of the world, where both decreasing and increasing growth trends have been detected over the last decades. The Mediterranean basin is especially sensitive to climate change and subsequent tree growth declines. In this article, we present the first study on recent tree growth trends in Turkey. Pinus nigra is a drought-sensitive species and one of the most common and economically important native conifers to Turkey. Tree-ring cores were taken from 61 Pinus nigra plots spread over the entire Lakes District (Southwest Turkey), near the species’ southern range limit. The samples cover the 1839–2013 time period. We apply the Regional Curve Standardization technique and statistical modeling to the tree ring width data to investigate long-term growth trends. Both methods show remarkably similar results: a slowly increasing growth trend until the 1970s, followed by a decreasing trend. This recent negative trend is highly correlated with increased temperature and drought in summer, which suggests that it is likely caused by climate change. [ABSTRACT FROM AUTHOR]

Although the annual diameter growth of trees is vital for assessing site suitability in terms of potential timber yield, the effects of climatic and topographic factors on this variable are poorly understood. The main objective of this study was to develop a tree-level radial growth model incorporating topographic and climatic factors for four major temperate tree species [red pine ( Pinus densiflora ), oak ( Quercus spp.), Japanese larch ( Larix kaempferi ), and Korean pine ( Pinus koraiensis )] in South Korea. The model was developed and then validated using increment cores sampled from permanent plots in the Korean National Forest Inventory country wide. The Standard Growth (SG) of each increment core, which eliminated the effect of tree age on radial growth, was derived using a SG model. Spatial autocorrelation was detected for the SGs of every species, but not for the original radial growth data. The results showed that using the SG model to standardize radial growth for age was successful for explaining the impact of topographic and climatic factors on radial growth. The influence of climatic (warmth index and precipitation effectiveness index) and topographic (topographic wetness index) factors on the SG of each species was evaluated by the estimated SG (eSG) model. Results show that for all species each variable was correlated to SG. The mean R 2 of the final radial growth model for red pine, oak, Japanese larch, and Korean pine during 2001–2009 were estimated to be 0.71, 0.73, 0.67, and 0.65, respectively. In addition, for every tree species the time sequence of estimated annual radial growth exhibited similar characteristics to that of the observed annual radial growth on an individual tree scale. Thus, this growth model can contribute to an understanding of the impacts of topographic and climatic factors on tree radial growth and predict the annual growth changes of major tree species in South Korea, given climate change. [ABSTRACT FROM AUTHOR]

Different tree species growing in the same area may have different, or even contrasting growth responses to climate change. Korean pine ( Pinus koraiensis ) and Mongolia oak ( Quercus mongolica ) are two crucial tree species in temperate forest ecosystems. Six tree-ring chronologies for Korean pine and Mongolia oak were developed by using the zero-signal method to explore their growth response to the recent climate warming in northeast China. Results showed that Mongolia oak radial growth was mainly limited by precipitation in the growing season, while Korean pine growth depended on temperature condition, especially monthly minimum temperature. With the latitude decrease, the relationships between Korean pine growth and monthly precipitation changed from negative to positive correlation, while the positive correlation with monthly temperature gradually weakened. In the contrary, Mongolia oak growth at the three sampling sites was significantly and positively correlated with precipitation in the growing season, while it was negatively correlated with temperature and this relationship decreased with the latitude decrease. The radial growth of Korean pine at different sites showed a clearly discrepant responses to the recent warming since 1980. Korean pine growth in the north site increased with the temperature increase, decreased in the midwest site, and almost unchanged in the southeast site. Conversely, Mongolia oak growth was less affected by the recent climate warming. Our finding suggested that tree species trait and sites are both key factors that affect the response of tree growth to climate change. In addition, the suitable distribution area of Korean pine may be moved northward with the continued global warming in the future, but Mongolia oak may not shift in the same way. [ABSTRACT FROM AUTHOR]

Tree ring widths provide very useful information to assess factors controlling tree radial growth and to estimate future growth trajectories under climate change. Radial growth variability has already been largely studied among tree populations that experience different environmental conditions and was most recently analyzed among individuals within populations. In the present study we assessed, over the 1960–2011 period, the growth response of silver fir ( Abies alba Mill.) individuals originating from ten populations located along two altitudinal gradients (1000–1600 m a.s.l.) in the south east of France. Tree ring increments were estimated from wood cores collected from 129 adult trees. Results showed that (i) 30% of the growth variance among individuals was explained by competition; (ii) the climates of both the current and previous years were correlated with growth. Most of the climatic variables affecting growth were consistent with those identified in previous studies and with the known physiology of the species: negative effects of summer drought of the current and past years as well as a positive effect of the spring temperature of the current year. However in our study, fir growth was also enhanced by previous year spring droughts. The growth responses to precipitation, temperature, and, relative humidity of the current and previous years varied between sites and/or altitudinal levels, reflecting population acclimation by plasticity or genetic adaptation to local conditions. By contrast, only summer rainfall induced variable responses between individual trees, result attributed to the edaphic micro local heterogeneity. The recent climate change did not significantly alter the fir growth response to climate. [ABSTRACT FROM AUTHOR]

The early culmination of maximum radial growth (RG) in late spring has been found in several coniferous species in a dry inner Alpine environment. We hypothesized that an early decrease in RG is an adaptation to cope with drought stress, which might require an early switch of carbon (C) allocation to belowground organs. To test this hypothesis, we experimentally subjected six-year-old Norway spruce saplings (tree height: 1.35 m; n = 80 trees) to two levels of soil water availability (watered versus drought conditions) and manipulated tree C status by physically blocking phloem transport at three girdling dates (GD). The influence of C availability and drought on tree growth (radial and shoot growth; root biomass) in response to girdling was analyzed in both treatments. Non-structural carbohydrates (NSCs, soluble sugars and starch) were measured in the stem, root and current leader to evaluate changes in tree C status due to girdling. The main finding was a significant increase in RG of the girdled trees compared to the controls above the girdling zone (UZ). At all girdling dates the RG increase was significantly more intense in the drought-stressed compared with watered trees ( c . 3.3 and 1.9-fold higher compared with controls in the drought-stressed and watered trees, respectively), most likely indicating that an early switch of C allocation to belowground occurs as an adaptation to maintain tree water status under drought conditions. Reactivation of the cambium after the cessation of its regular activity was detected in UZ in drought-stressed trees, while below the girdling zone no xylem formation was found and the NSC content was strikingly reduced. Irrespective of water availability, girdling before growth onset significantly reduced the progression of bud break ( P < 0.05) and the length of the current leader shoot by −47% ( P < 0.01) indicating a reduction in xylem hydraulic conductance, which was corroborated by significantly reduced xylem sap flow ( P < 0.001). Based on our findings, we conclude that during the growing season drought stress prioritizes an early switch of C allocation to the root system as an adaptation to maintain adequate tree water status in drought-prone environments. [ABSTRACT FROM AUTHOR]

Increasing frequency and intensity of drought extremes associated with global change are a key challenge for forest ecosystems. Consequently, the quantification of drought effects on tree growth as a measure of vitality is of highest concern from the perspectives of both science and management. To date, a multitude of drought indices have been used to accompany or replace primary climatic variables in the analysis of drought-related growth responses. However, it remains unclear how individual drought metrics compare to each other in terms of their ability to capture drought signals in tree growth. In our study, we employ a European multispecies tree ring network at the continental scale and a set of four commonly used drought indices (De Martonne Aridity Index, self-calibrating Palmer Drought Severity Index, Standardized Precipitation Index and Standardized Precipitation Evapotranspiration Index, the latter two on varying temporal scales) to derive species-specific growth responses to drought conditions. For nine common European tree species, we demonstrate spatio-temporal matches and mismatches of tree growth with drought indices subject to species, elevation and bioclimatic zone. Forests located in the temperate and Mediterranean climate were drought sensitive and tended to respond to short- and intermediate-term drought (<1 year). In continental climates, forests were comparably more drought resistant and responded to long-term drought. For the same species, stands were less drought sensitive at higher elevations compared to lower elevations. We provide detailed information on the month-wise performance of the four drought indices in different climate zones allowing users the selection of the most appropriate index according to their objective criteria. Our results show that species-specific differences in responses to multiple stressors result in complex, yet coherent patterns of tree growth. [ABSTRACT FROM AUTHOR]

Pedunculate oak ( Quercus robur L.) is a long-lived species that dominates the extra–zonal natural forests in the steppe landscape of southeastern Ukraine. Although Q. robur is considered to be one of the most important species in European dendrochronology, it has received little attention in the steppe zone because of its scarcity in the often-degraded steppe forests. Nevertheless, a small and unique patch of old-growth oak exists within the boundary of Donetsk, a large industrial center in Eastern Europe. This forest is a remnant of an ancient wood and includes several dozen old-age trees that can contribute to filling some of the spatial gaps in pedunculate oak dendrochronology in Eastern Europe. In this study, we aim to determine the effect of climatic variables on pedunculate oak growth in the steppe zone, and to estimate the longevity of this species in the heterogeneous conditions of an urban forest. A total of 20 trees were cored for this study, varying in age from 55 to 254. The resulting tree-ring chronology correlates strongly with local precipitation in spring and summer, and with local temperature in April, June and July. Moving correlation analysis indicates a shift over the last 80 years in the relationship between oak growth and late winter and early spring temperatures, as well as between oak growth and precipitation in February and August. These findings imply that warming has caused both an advance in oak phenology and changes in the climatic conditions in early spring. [ABSTRACT FROM AUTHOR]

[Display omitted] • Radial growth of planted P. orientalis was limited by drought stress in autumn and winter of the previous year. • Planted mixed stands have enhanced recovery capacity after extreme drought compared with pure stands. • The recovery capacity of planted P. orientalis after the extreme drought is stronger than C. korshinskii. Multispecies arbor-shrub mixed stands have long been applied in vegetation restoration of the Chinese Loess Plateau, and are expected to provide better production and ecosystem services than pure stands. However, whether higher species and structural diversity will help mitigate the limitations of drought on plantations growth remain poorly quantified. We collected samples of the arbor Platycladus orientalis Linn. and shrub Caragana korshinskii Kom. under different stand structures with the same site conditions, using dendroecological methods analyzed the resistance, recovery, and resilience of mixed and pure stands in response to extreme drought, and compared the differences of recovery capacity under different tree species and stand structures based on the theory of full resilience. Results suggest that drought has a lag effect on plantations growth. Radial growth of mixed and pure stands was mainly limited by drought stress in autumn and winter of the previous year and late spring and early summer of the current year. The recovery after the extreme drought of both planted P. orientalis and C. korshinskii mixed stands were significantly (p < 0.05) higher than pure stands, and there are tradeoffs between resistance and recovery. Comparing the different tree species, even if the drought-induced P. orientalis growth reduction reaches 58.5% (mixed stands) and 41.6% (pure stands), it still has the possibility of recover fully, while C. korshinskii is difficult to recover to the previous level, and the mixed mode also affects the response of plantations to drought stress. Therefore, the growth habits and adaptability of different planted species to drought stress should be considered in the future afforestation projects, and select tree species with complementary traits for mixed planting. Taken together, these findings have important significance for mitigating the limitations of drought on plantations growth and maintaining the ecological function stability of plantations in the western Loess Plateau. [ABSTRACT FROM AUTHOR]

• Black spruce trees formed continuous adventitious roots in water saturated soil. • Highest radial growth was registered in the younger adventitious roots. • Survival strategy: allocation of a higher amount of energy to the root system. Large areas in boreal forests are classified as peatlands, characterized by organic soils with a high water table. Black spruce (Picea mariana (Mill.) B.S.P.) is one of the species capable of growing in this inauspicious environment, where an adaptation of the root system can be expected. We studied young black spruces growing in peat moss with two different hydrological conditions over a 19 years timespan: saturated and well-drained peat. We identified the initial and adventitious roots of the trees and compiled radial growth measurements of each root. The general growth pattern of the roots was identified and compared to the annual radial growth within the stem. We observed growth reductions during the first years after the planting shock, followed by a growth increase in the roots and stems for both hydrological conditions. The continuous formation of adventitious roots in trees growing in the saturated environment was the main adaptation noticed. The largest radial growth values were registered in the younger adventitious roots growing in saturated conditions. The lowest radial growth in the adventitious roots were registered in the well-drained condition. PCA analyses revealed the influence of root depth with regard to stem height and diameter at soil level. The black spruce trees displayed the required plasticity to form adventitious roots outside the range of the water table, allowing them a better access to oxygen and nutrients. This survival strategy implies to allocate a higher amount of energy to the root system instead of the aerial part of the tree in which overall productivity is low. [ABSTRACT FROM AUTHOR]

• Drought legacies on tree growth are frequently studied, but not on reproduction. • We analyzed the legacy effects of drought on reproduction of Quercus ilex. • No negative drought legacy effects were found in the three years following drought. • Male inflorescence production did not show any significant legacy after drought. • Acorn production followed tree growth recovery with a certain lag. Droughts are becoming more frequent in the Mediterranean basin due to warmer conditions. Droughts negatively impact forests growth for several years, often generating negative legacies or carryover effects. However, these legacies differ among tree species, sites and drought characteristics and have been mainly studied considering tree growth or canopy greenness, but ignoring reproductive phenomena. Here, we compare the legacy effects of drought on acorn and male inflorescence production and radial growth by using a 19-year series of 150 Quercus ilex individuals in three stands located in north-eastern Spain. We evaluate the relationships between monthly climate variables, tree-ring width, acorn production and male inflorescence production. For the two driest years considered (2005 and 2012), when very few acorns were produced, we did not find negative legacy effects on acorn production in the three years following droughts. The production of male inflorescences did not show any significant legacy after drought, although its annual variation was related to the climatic conditions of the year before acorn ripening. Acorn production was higher than expected for some of these years, apparently following the pattern of tree growth recovery with a certain lag. This compensatory response of acorn production differed between the two analysed droughts, in accordance with different conditions of drought timing and post-drought climate conditions. Even though few negative legacy effects of growth and acorn production were found, we confirmed the negative effect of drought stress on tree growth and acorn production, linked to dry winter conditions. Our findings confirm that drought features (timing, duration, intensity) and post-drought climate conditions influence tree growth and reproduction legacies. [ABSTRACT FROM AUTHOR]

• Growth-climate relationship was comparable similar in NF and PF. • Growth responses to climate variables varied among sites both in NF and PF. • Only climate impacts on growth in PF did show seasonal latitudinal patterns. • Temperature explained most of the variations in radial growth of NF and PF. A better understanding of the relationship between tree growth and climate in natural forests (NF) and planted forests (PF) may help in predicting the potential impacts of climate change on forest growth. In this study, we compare the effects of climate variability on the radial growth of Pinus massoniana in NF and PF in the subtropical region of central-southern China along a large latitudinal gradient (24° - 32°N). Three to four plots were selected in both NF and PF at each of six sites, and core samples were taken from at least five trees in each plot. The tree rings of each core were analyzed and the ring widths measured. Our results show that growth-climate relationships are largely similar in NF and PF. Tree growth is positively correlated with temperatures in March, but negatively correlated with maximum temperature in September and November. Precipitation and the standardized precipitation evapotranspiration index (SPEI) in autumn enhance growth but those in May and June inhibit growth. Sunshine duration in autumn has a stronger negative effect on PF than NF. Growth responses to climate variables vary among sites both in NF and PF. From south to north, the effects of temperatures in summer on tree growth in PF shift from inhibiting to promoting tree growth. Precipitation in summer and winter has the opposite effect along the latitudinal gradient. The limiting effect of drought increases with latitude from south to north in PF, but not in NF. At the regional level, temperature explains most of the variance in radial growth of both NF and PF, whereas precipitation and SPEI explain more of the variance in PF than in NF. Our findings not only enrich our knowledge regarding the impacts of climate on forest growth, but also provide implications for the future forest sustainable management in the subtropical regions of central China. [ABSTRACT FROM AUTHOR]

Tree phenology is sensitive to climate warming and changes in seasonal precipitation. Long xylogenesis records are scarce, thus limiting our ability to analyse how radial growth responds to climate variability. Alternatively, process-based growth models can be used to simulate intra-annual growth dynamics and to better understand why growth bimodality varies along temperature and precipitation gradients. We used the Vaganov-Shashkin (VS) growth model to analyse the main climatic drivers of growth bimodality in eight trees and shrubs conifers (four pines and four junipers) across Spain. We selected eleven sites with different continentality degree and spring/autumn precipitation ratios since we expected to find pronounced bimodal growth in less continental sites with spring and autumn precipitation peaks. The VS model successfully simulated annual growth rates at all sites as a function of daily temperature and soil moisture data. Bimodal growth patterns clustered into less continental sites showing low spring/autumn precipitation ratios. This finding agrees with observed climate-growth associations showing that growth was enhanced by wet-cool winter-to-spring conditions, but also by wet autumn conditions in the most bimodal sites. We observed a stronger growth bimodality in pines compared to junipers. We discuss the spatial variability of climate drivers in bimodality growth pattern and how increasing continentality and shifts in seasonal precipitation could affect growth patterns. Bimodality could be an advantageous response to overcome summer drought in Mediterranean forests. The ability of some species to reactivate growth during autumn might determine their capacity to withstand increasing summer aridity. [ABSTRACT FROM AUTHOR]

Many studies have already addressed the existence of unstable and nonlinear relationships between radial growth of white spruce ( Picea glauca ) and climate variables in boreal forests along the high latitudes (>60° N). However, along the mid-latitudes, the climate-growth relationship is still poorly understood. In this study, we used a network of ring-width chronologies from 40 white spruce sites along a wide latitudinal gradients from 52° N to 58° N in Alberta, Canada and attempted to understand the complicated response of tree growth to climatic variables and to identify the main limiting factor for the radial growth of white spruce. We combined the empirical linear statistics with the process-based Vaganov-Shashkin Lite (VS-Lite) model requiring only latitude, monthly mean temperature, and monthly total precipitation information together to better clarify growth-climate relationship. The linear statistical methods indicated that the previous summer temperature imposed a strong negative impact on the radial growth of white spruce while the precipitation and climate moisture index in prior and current summer both had significant positive effects on the radial growth. Similarly, the VS-Lite model showed that the radial growth of white spruce was limited by soil moisture. This suggests that temperature-induced drought is the main limiting factor for the radial growth of white spruce. Furthermore, climate-growth relationship varied along different elevations, latitudes, and growing degree days (GDD >5 °C). The radial growth of white spruce in northern stands was often more strongly limited by temperature-induced drought due to the higher temperature and lower precipitation. As the global climate change is in progress, we suggest that more large-scale and continuous investigations are needed to address the spatial variation in growth-climate relationship due to the temperature-induced drought. [ABSTRACT FROM AUTHOR]

Schrenk spruce ( Picea schrenkiana Fisch. et Mey.) is widely distributed in the Tianshan Mountains. In this study, four Schrenk spruce trees were continuously monitored with dendrometers from 27 April to 30 September 2014 on the northern slopes of the Tianshan Mountains in northwest China. The goal of this monitoring study was to determine the main growing season of Schrenk spruce and to analyze intra-annual radial growth variability and its relation to daily meteorological factors. Our studies have shown that the critical growing season of Schrenk spruce is from late May to late July and that the rapid growth stage is from mid-June to early July. Meanwhile, in the growing season, changes in the radial growth of Schrenk spruce were negatively correlated with daily temperature, evaporation, sunshine hours and vapor pressure deficit (VPD), and were positively correlated with precipitation and relative humidity (RH). The correlation coefficient between radial growth and RH can be as high as 0.750 (Pearson, p < 0.0001, n = 60). Dates in which precipitation occurred corresponded to periods of rapid growth. The results of the climate-growth analysis show that changes in radial growth reflect the effect of water stress on tree growth, whether or not the changes are positively or negatively correlated with the above climatic factors. This indicates that moisture plays a major role in the growth of Schrenk spruce. We suggest that precipitation between late May to late June is a limiting factor for radial growth of Schrenk spruce on the northern slopes of the Tianshan Mountains. [ABSTRACT FROM AUTHOR]

Dendrometers are measurement devices proven to be useful to analyze tree water relations and growth responses in relation to environmental variability. To analyze dendrometer data, two analytical methods prevail: (1) daily approaches that calculate or extract single values per day, and (2) stem-cycle approaches that separate high-resolution dendrometer records into distinct phases of contraction, expansion and stem-radius increment. Especially the stem-cycle approach requires complex algorithms to disentangle cyclic phases. Here, we present an R package, named dendrometeR, that facilitates the analysis of dendrometer data using both analytical methods. By making the package freely available, we make a first step towards comparable and reproducible methods to analyze dendrometer data. The package contains customizable functions to prepare, verify, process and plot dendrometer series, as well as functions that facilitate the analysis of dendrometer data (i.e. daily statistics or extracted phases) in relation to environmental data. The functionality of dendrometeR is illustrated in this note. [ABSTRACT FROM AUTHOR]

Increasing frequency of extremely dry and hot summers in some regions emphasise the need for silvicultural approaches to increase the drought tolerance of existing forests in the short term, before long-term adaptation through species changes may be possible. The aim of this meta-analysis was to assess the potential of thinning for improving tree performance during and after drought. We used results from 23 experiments that employed different thinning intensities including an unthinned control and focused on the response variables: radial growth, carbon- and oxygen-isotopes in tree-rings and pre-dawn leaf-water potential. We found that thinning effects on the growth response to drought differed between broadleaves and conifers, although these findings are based on few studies only in broadleaved forests. Thinning helped to mitigate growth reductions during drought in broadleaves, most likely via increases of soil water availability. In contrast, in conifers, comparable drought-related growth reductions and increases of water-use efficiency were observed in all treatments but thinning improved the post-drought recovery and resilience of radial growth. Results of meta-regression analysis indicate that benefits of both moderate and heavy thinning for growth performance following drought (recovery and resilience) decrease with time since the last intervention. Further, growth resistance during drought became smaller with stand age while the rate of growth recovery following drought increased over time irrespective of treatment. Heavy but not moderate thinning helped to avoid an age-related decline in medium-term growth resilience to drought. For both closed and very open stands, growth performance during drought improved with increasing site aridity but for the same stands growth recovery and resilience following drought was reduced with increasing site aridity. This synthesis of experiments from a wide geographical range has demonstrated that thinning, in particular heavy thinning, is a suitable approach to improve the growth response of remaining trees to drought in both conifers and broadleaves but the underlying processes differ and need to be considered. [ABSTRACT FROM AUTHOR]

Understanding the effects of climate on the growth of trees is important to project the response of forests to climate change. Dendrochronological analysis offers a “proxy” source for the effects of climatic variation on tree growth at different spatial and temporal scales. To examine influences of temperature and precipitation on radial growth of Pinus pseudostrobus and Abies religiosa , this study combines measurements of radial growth patterns of forest trees in the Monarch Butterfly Biosphere Reserve (MBBR) in central Mexico with temperature and precipitation variables from instrumental records. Dendrochronological samples were collected as cross sections and increment cores by using a chainsaw and increment borers, respectively. Total ring-width chronologies were developed for each site. Principal component analyses (PCA) were used to identify common temperature, precipitation and tree growth variation patterns. Correlation and response function analyses between chronologies and records of temperature and precipitation were used to evaluate the relation of climate variables on tree growth. The months during which tree growth was most strongly affected by precipitation were January, February and October from the previous year; only the temperature of September from the previous year affected the tree growth. In some chronologies, May’s average monthly maximum temperature was negatively correlated with tree growth. PCA and a comparison of PCA factor scores of climatic variables and chronologies showed no significant differences between northern, central or southern portions of the MBBR. Apparently, tree growth in the MBBR is reduced in years of low January–May precipitation combined with high summer (September of the previous year) temperatures, a scenario which is likely to occur as a consequence of global climate change. [ABSTRACT FROM AUTHOR]

The genetic mechanisms underlying the relationship of individual heterozygosity (IndHet) with heterosis and homeostasis are not fully understood. Such an understanding, however, would have enormous value as it could be used to identify trees better adapted to environmental stress. Dendrochronology data, in particular the individual average radial increment growth of wood measured as the average tree ring width (AvTRW) and the variance of tree ring width (VarTRW) were used as proxies for heterosis (growth rate measured as AvTRW) and homeostasis (stability of the radial growth of individual trees measured as VarTRW), respectively. These traits were then used to test the hypothesis that IndHet can be used to predict heterosis and homeostasis of individual trees. Wood core and needle samples were collected from 100 trees of Siberian larch ( Larix sibirica Ledeb.) across two populations located in Eastern Siberia. DNA samples were obtained from the needles of each individual tree and genotyped for eight highly polymorphic microsatellite loci. Then mean IndHet calculated based on the genotypes of eight loci for each tree was correlated with the statistical characteristics of the measured radial growth (AvTRW and VarTRW) and the individual standardized chronologies. The analysis did not reveal significant relationships between the studied parameters. In order to account for the strong dependence of the radial growth on tree age the age curves were examined. An original approach was employed to sort trees into groups based on the distance between these age curves. No relationship was found between these groups and the groups formed based on heterozygosity. However, further work with more genetic markers and increased sample sizes is needed to test this novel approach for estimating heterosis and homeostasis. [ABSTRACT FROM AUTHOR]

• We monitored the sap-flux velocity and growth of several tropical peatland species. • Sap-flux velocity was mainly controlled by vapor pressure deficit and radiation. • Non-native species had up to twice the daily radial growth of native species. • Different water table-growth relationships between native and non-native species. Ecohydrological studies in tropical peatland have mostly focused on a small number of non-native commercial species. However, studies of native species are urgently needed as they are considered to be a possible solution in the restoration of millions of hectares of degraded tropical peatlands. We investigated peatland species on Padang Island, Indonesia, to assess their responses to changing environmental factors, particularly the high fluctuation of the water table due to intensive peatland draining. We monitored the sap-flux velocity and radial growth of six trees (four native and one non-native peatland species) in high temporal resolution using sap-flux meters and dendrometers up to seven months. Monitoring also included hydrological and micrometeorological parameters. We found that sap-flux velocity in the monitored species was mainly controlled by air vapor pressure deficits, photosynthetic active radiation, and to some extent, by wind speed and water-table depth. We also observed a species-specific correlation between daily sap-flux velocity and daily radial growth. Non-native Acacia crassicarpa had up to twice the radial growth of native species. This growth of non-native species was significantly higher at a shallow water-table depth, while native species did not show the same relationship. The interaction between water-table depth, sap-flux velocity, and radial growth in daily timescale was not straightforward, presumably because of the complex carbon-allocation mechanism in trees. [Display omitted] [ABSTRACT FROM AUTHOR]

• A climate-sensitive radial growth model was developed by fusing tree-ring and permanent sample plot data. • Temperature and precipitation during the growing season were the main climatic drivers of radial growth. • Growth response to thinning was positively correlated with thinning intensity. • Thinning mitigated the negative impacts of climate on radial growth. An improved understanding of the effects of thinning and climate on tree growth is essential to adopting adaptive forest management strategies under climate change. In this study, we developed a climate-sensitive individual-tree growth model for Changbai larch (Larix olgensis) in northeast China by fusing tree-ring and permanent sample plot data. We assessed the impacts of tree age, competition, site condition, thinning, and climate on radial growth using the mixed-effects modeling approach. Results showed that the radial growth rate of Changbai larch decreased with increasing cambial age and competition intensity. Radial growth was negatively associated with summer water deficit and positively associated with spring growing degree-days. Radial growth also responded positively to mean annual precipitation of the previous year. In addition, a significant positive effect of thinning on radial growth was observed. The magnitude of thinning effects was affected by thinning intensity and time elapsed since the thinning. Hierarchical partitioning analysis showed that cambial age was the most important factor affecting growth (relative contribution 35.96%), followed by competition (31.42%), climate (19.24%), thinning (8.40%), and site condition (4.98%). Compared to unthinned plots, moderate- and high-intensity thinning significantly enhanced the radial growth under unfavorable climates, indicating that thinning has great potential to mitigate the negative effects of future climate. Disentangling different sources of variations in ring width will help advance our understanding of the factors driving radial growth and reduce the uncertainty in forest management decisions. [ABSTRACT FROM AUTHOR]