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

Several important environmental influences of tree growth and carbon sequestration have changed over the past several decades in eastern North America, specifically, more frequent pluvial conditions, increased carbon dioxide (CO2) concentrations, and decreased acidic deposition. These factors could lead to changes in the relationship between tree growth and water availability, and perhaps even decouple the two, having large implications on how future climate change will impact forest productivity and carbon sequestration. Here, we examine the concurrent influence of the climatic water balance (precipitation minus potential evapotranspiration), CO2 concentrations, and sulfate and nitrogen deposition on radial tree growth, carbon isotopes, and intrinsic water-use efficiency (iWUE) for several hardwood tree species in the Midwestern United States. We found that when considering the simultaneous influence of these factors, the climatic water balance is the dominant influence on annual growth. Therefore, the recent pluvial period is the primary cause of the weakening relationship between radial growth and water availability. Even during pluvial periods, water availability is the primary control on growth, with increasing CO2 concentrations and decreased SO4 deposition being secondary factors. Importantly, the weakening in the climate-growth relationship is species specific, with Acer species having stable relationships with the climatic water balance, Liriodendron tulipifera showing a strengthening relationship, and Quercus species and Populus grandidentata exhibiting weakening. Thus, interannual variations in soil moisture unevenly impact tree growth and carbon sequestration. Our findings suggest that, despite recent pluvial conditions, increasing CO2 concentrations and decreasing acidic deposition have not buffered the impact of water availability on tree growth and carbon sequestration.

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

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

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

Changing climate can strongly affect tree growth and forest productivity. The dendrochronological approach to assessing the impact of climate change on tree growth is possible through climate–growth correlation analysis. This study uses an individual tree-based approach to model Pinus wallichiana (P. wallichiana) radial growth response to climate across the physiographic gradients in the lower distributional range of Nepal. This study sampled six sites across the Makwanpur district of central Nepal that varied in elevation and aspect, obtaining 180 tree-ring series. Climate data series were obtained from Climate Research Unit (CRU 4.0). The pair correlation approach was used to assess P. wallichiana growth response to climate and site-level physiographic variables such as site-level environmental stress. The study also determined long-term growth trends across the elevation and aspect gradients. Trees at sites with higher elevation and northeast aspect (NEA) were more responsive to winter and spring precipitation, whereas trees with lower elevation and northwest aspect (NWA) were more responsive to winter and spring precipitation. Basal area increment (BAI) analysis showed the variation of growth at site-level environmental stress, suggesting that the sensitivity of forest ecosystems to changing climate will vary across the lower growth limit of P. wallichiana due to differences in local physiographic conditions. [ABSTRACT FROM AUTHOR]

Though rising atmospheric CO2 concentrations (Ca) harm the environment and society, they may also raise photosynthetic rates and enhance intrinsic water-use efficiency (iWUE). Numerous short-term studies have investigated tree growth under elevated CO2 (eCO2) conditions, but no long-duration study has investigated eCO2 impacts on tree growth and iWUE under natural conditions. Utilizing a new dendrochronological experimental design in a heavily-touristed nature preserve in Southwest China (Jiuzhaigou National Nature Reserve), we compared tree growth (e.g., basal area increment) and iWUE in two biophysically and environmentally similar valleys with contrasting anthropogenic activities. Trees in the control valley with ambient CO2 benefited from increasing Ca, possibly due to the CO2 fertilization effect and optimal environmental conditions. However, trees in the treatment valley with intensive tourism experienced comparatively higher localized eCO2 and growth rate declines. While iWUE increased (1959–2017) in the control (25.3%) and treatment sites (47.8%), declining tree growth rates in the treatment site was likely because comparatively extreme CO2 exposure levels encouraged stomatal closures. As the first long-term study investigating eCO2 impacts on tree growth and iWUE under natural conditions, we demonstrate that increased forest iWUE is unlikely to overcome negative drought stress and rising temperature impacts. Thus, forest potential for mitigating eCO2 and global climate change is likely overestimated, particularly under dry temperate conditions.

Spatial interactions between trees influence forest community succession. The objective of this study was to investigate how shifts in forest composition and proximity between tree species affect stand development over time in mixed forest systems. At six locations across the Fishlake National Forest, Utah, USA, in stands where facilitation has been documented previously, tree‐ring samples were collected from aspen and subalpine fir trees. Basal area increment was calculated to characterize the effects of the proximity of overstory trees on multidecadal growth responses of aspen and subalpine fir in aspen‐dominant and mixed aspen–conifer stands. Subalpine fir seedlings were established next to aspen (within 10 cm) when aspen was between 15 and 120 years old with a mean age of 60 years. Aspen and subalpine fir growth rates were reduced with increasing conifer abundance. Aspen trees growing next to a proximate subalpine fir tree had slower growth rates over time than aspen trees growing independently. Growth rates of subalpine fir in aspen‐dominated stands were similar when growing independently or near aspen trees. However, subalpine fir in conifer‐dominated stands maintained higher growth rates when growing next to an aspen tree than when growing independently. The data suggest that as stand competition increases with conifer abundance, the proximity of overstory trees increases competitive exclusion of aspen while having a beneficial growth effect on subalpine fir. These results underscore the importance of maintaining natural fire regimes in forest systems that keep competitive interactions in balance. [ABSTRACT FROM AUTHOR]

Abstract Spatial interactions between trees influence forest community succession. The objective of this study was to investigate how shifts in forest composition and proximity between tree species affect stand development over time in mixed forest systems. At six locations across the Fishlake National Forest, Utah, USA, in stands where facilitation has been documented previously, tree‐ring samples were collected from aspen and subalpine fir trees. Basal area increment was calculated to characterize the effects of the proximity of overstory trees on multidecadal growth responses of aspen and subalpine fir in aspen‐dominant and mixed aspen–conifer stands. Subalpine fir seedlings were established next to aspen (within 10 cm) when aspen was between 15 and 120 years old with a mean age of 60 years. Aspen and subalpine fir growth rates were reduced with increasing conifer abundance. Aspen trees growing next to a proximate subalpine fir tree had slower growth rates over time than aspen trees growing independently. Growth rates of subalpine fir in aspen‐dominated stands were similar when growing independently or near aspen trees. However, subalpine fir in conifer‐dominated stands maintained higher growth rates when growing next to an aspen tree than when growing independently. The data suggest that as stand competition increases with conifer abundance, the proximity of overstory trees increases competitive exclusion of aspen while having a beneficial growth effect on subalpine fir. These results underscore the importance of maintaining natural fire regimes in forest systems that keep competitive interactions in balance.

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

Key message: Large sugar pine mortality was associated with recent growth and defense measures. Many old-growth pine forests across the western United States have encountered widespread and concerning increases in tree mortality attributed to increased competition and reduced vigor associated with prolonged fire exclusion that can make trees more vulnerable to bark beetles. We investigated the importance of growth and resin duct defense on recent mortality of large sugar pine (Pinus lambertiana) in a fire-excluded, mixed-conifer forest of the Sierra Nevada, in California, USA. Growth and defense were measured from tree rings for 33 pairs of live and dead sugar pine. The 10-year trend in basal area increment prior to sampling declined by 1.78 cm2 year− 1 in sugar pine that died and increased by 0.34 cm2 year− 1 in paired live sugar pine. The 10-year trend in resin duct total area showed declines of 0.0154 mm2 year− 1 in trees that died and increases of 0.0068 mm2 year− 1 in trees that survived. The most informative models of large sugar pine mortality included measures of both growth and defense. The top model included the trends of basal area increment and resin duct total area 10 years before mortality, and growth variability 5 years before mortality. In general, trends and variability in growth and defense over shorter time windows (< 10 years) were more informative than average measures or longer time windows. The results from our study suggest treatments that result in neutral to positive trends in allocation to growth and defense may contribute to conditions that reduce probability of mortality in the future. [ABSTRACT FROM AUTHOR]

The influence of climate on the vitality and growth of European beech (Fagus sylvatica L.) has become a focus of forest research over the last decade. Beech locally reaches its continental xeric limit in Hungary within its European distribution area, giving a unique opportunity to study the climatic sensitivity of the species, based on tree-ring analysis. A comparison of four geographically and climatically different sites is presented from Hungary, combining data collected on stand level with systematic forest inventory plots. Tree-ring width chronologies covering the past 90-100 years of the lifetime of mature and middle-aged trees and different climatic variables were used to evaluate the growth-climate relationships and recent growth trends of the selected beech stands by multivariate regression analysis. Strong relationships were found between annual radial growth and (mainly water availability related) meteorological variables of the vegetation season, exceeding previous results from elsewhere in Europe. A clear spatiotemporal variability of the growth sensitivity was also revealed, following a (climatic) gradient from the northern to the southwestern parts of the country. In the northern sites, climatic sensitivity was found to be more fluctuating, while southwestern sites facing more continuous effects of changing climatic conditions seem to show weakening correlation over time. Trends of relative basal area increments and climatic sensitivity of growth over the past decades may be due to unfavorable climatic changes, though extreme and recurrent drought events superimposed on the long-term trends seem to have a decisive impact on growth patterns and associated resilience of beech. [ABSTRACT FROM AUTHOR]

Edge effects are a major cause of natural dynamics of fragmented forests; however, studies that evaluate edge effects during the lifetime of trees are relatively rare. Through a long-term perspective of tree growth, dendroecology can contribute to a better understanding of the influence of edge effects. In order to frame our interpretation, we raised the following hypotheses: (1) trees located close to a forest edge have lower growth rates compared to trees growing far from edges, and (2) climate sensitivity of trees naturally growing on the forest edge is different from the trees in the interior. This study was conducted in Southern Brazil, where 21 Araucaria angustifolia located 50mfrom the edge and 19 individuals located 4000 m from the forest edge were sampled. Dendrochronological study followed the usual procedures and growth patterns were evaluated using basal area increment, specific threshold value of fast and slow growth, and principal components analysis. During the 54 years analyzed, results indicated that the edge effect reduced growth by 30% in diameter increment and wood production of A. angustifolia trees. Regarding the influence of climatic variability on tree growth, we observed that edge effects may exert strong pressure on growth responses to climate in A. angustifolia located on forest edges, making individuals in those environments potentially more sensitive to variations in temperature and rainfall, mainly at warmer times of year. We therefore emphasize the importance of considering edge trees as potential bioindicators of historical environmental changes and forest fragmentation. Future studies should be carried out in other forest types and with different tree species (e.g. pioneer vs. shade-tolerant, trees vs. shrubs) to test the reliability of our results and provide more robust conclusions about this phenomenon. [ABSTRACT FROM AUTHOR]

Several important environmental influences of tree growth and carbon sequestration have changed over the past several decades in eastern North America, specifically, more frequent pluvial conditions, increased carbon dioxide (CO2) concentrations, and decreased acidic deposition. These factors could lead to changes in the relationship between tree growth and water availability, and perhaps even decouple the two, having large implications on how future climate change will impact forest productivity and carbon sequestration. Here, we examine the concurrent influence of the climatic water balance (precipitation minus potential evapotranspiration), CO2 concentrations, and sulfate and nitrogen deposition on radial tree growth, carbon isotopes, and intrinsic water‐use efficiency (iWUE) for several hardwood tree species in the Midwestern United States. We found that when considering the simultaneous influence of these factors, the climatic water balance is the dominant influence on annual growth. Therefore, the recent pluvial period is the primary cause of the weakening relationship between radial growth and water availability. Even during pluvial periods, water availability is the primary control on growth, with increasing CO2 concentrations and decreased SO4 deposition being secondary factors. Importantly, the weakening in the climate‐growth relationship is species specific, with Acer species having stable relationships with the climatic water balance, Liriodendron tulipifera showing a strengthening relationship, and Quercus species and Populus grandidentata exhibiting weakening. Thus, interannual variations in soil moisture unevenly impact tree growth and carbon sequestration. Our findings suggest that, despite recent pluvial conditions, increasing CO2 concentrations and decreasing acidic deposition have not buffered the impact of water availability on tree growth and carbon sequestration. Plain Language Summary: In recent decades, many factors that influence tree growth have changed across the Midwestern United States, including more precipitation, higher carbon dioxide concentrations in the atmosphere, and fewer pollutants. Changes in these environmental factors could result in tree growth being less sensitive to water availability. While a weakening relationship between water availability and tree growth is present, it is difficult to determine the cause. Here, we examine the simultaneous influence of a wetter climate, higher carbon dioxide concentrations, and a decrease in pollutants deposition on tree growth and how efficiently trees use water. We found that when considering all three variables, increased moisture was the leading influence on tree growth. Therefore, the recent wet period is behind trees being less sensitive to soil moisture, not increases in carbon dioxide or decreases in pollutants. It is important to note that some species such as oak and aspen did become less sensitive to soil moisture, other species such as maple and tuliptree did not. This is important because when drought conditions return to the region, trees will still be sensitive despite higher carbon dioxide concentrations or decreases in sulfate and nitrate deposition. Key Points: Recent weakening of the relationship between climatic water balance and radial growth and C isotopes was species specificWater availability is the dominant factor influencing long‐term radial growth even when considering the simultaneous influence of other factors such as increasing atmospheric CO2 and decreasing acidic depositionIncreasing atmospheric CO2 concentrations increased water‐use efficiency but not growth of most tree species [ABSTRACT FROM AUTHOR]

Highlights • Growth rings are relevant ecological indicators of historical environmental changes. • Edge effects reduced the basal area increment of the trees for at least 10 years. • Release events did not reflect higher growth of edge trees compared to interior trees. • The resumption of the common growth pattern was related to edge evolution. Abstract Although the Amazon Forest comprises the world's largest rainforest, providing fundamental ecosystem services to human well-being, vicissitudes imposed by deforestation, climate change, widespread use of fire and development of new infrastructure make the region critically vulnerable to the consequences of the creation of new forest edges. In this forest fragmentation scenario, temporal assessment of edge effects influences throughout the life of the trees become necessary for a better understanding of how species are affected and react when exposed to altered environments. In this study, we evaluated the temporal influence of the edge effect on the growth dynamics of Scleronema micranthum (Ducke) Ducke by tree-ring analysis based on basal area increment and release events. This species is one of the most frequent tree species of terra firme type of forest in Central Amazonia at the Biological Dynamics of Forest Fragment Project (BDFFP) study sites. The results showed that edge effects changed the growth dynamics of the trees for at least 10 years after the disturbance, inducing an 18% reduction in tree growth during this period, and records of increased release events. We concluded that growth rings of edge trees are a valuable bioindicators for evaluating the temporal extent of edge effects, and therefore, they must be considered as relevant ecological indicators of historical environmental changes and forest fragmentation, promoting new insights into the resilience ability of trees when exposed to forest fragmentation processes. [ABSTRACT FROM AUTHOR]

Accurately assessing the impact of climate changes on tree growth or forest productivity is vital to better understand global carbon cycles. Here, we carried out dendroclimatological research on Yezo spruce ( Picea jezoensis var. microsperma ) along an elevation gradient in two sites to investigate the effect of rapid warming on spruce growth in northeast China. Results indicated that trees at two low-elevation sites had significantly wider ring widths and higher basal area increment (BAI) compared with high-elevation sites. Ring widths and BAI of Yezo spruce at low elevations showed a clear growth increase during the 1940s–1970s followed by a significant decline after 1980. However, trees at high elevations showed a relatively stable growth during the 1940s–1970s followed by a significant increase after 1980. Rapid warming after 1980 increased the radial growth of Yezo spruce at high-elevation sites, but reduced tree growth at low-elevation sites. Winter precipitation and growing season temperature were positively correlated with radial growth of Yezo spruce at high elevations, but negatively correlated with tree growth at low elevations. A clear pattern of growth and growth-climate relationship changed in 1980. The temperature threshold for determining the impact of climate on Yezo spruce could change with latitude or site. Difference in drought caused by warming may be the main reason for the opposite response of tree growing at different altitudes in northeast China. The mechanism of rapid warming driving contrasting growth at different elevations should also be investigated in other tree species in NE Asia. In the context of future climate warming, our findings are of great significance for tree growth in assessing forest dynamics and carbon cycling. [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]

Chaparral wildfires typically create even-aged stands of vegetation that grow quickly in the first 2 decades following a fire. Patterns of this growth are important for understanding ecosystem productivity and re-establishment success, but are logistically challenging to measure over long time periods. We tested the utility of a novel method of using shrub growth rings to estimate stand-level biomass accumulation at an annual time scale in southern California chaparral. We examined how temporal variation in precipitation and spatial variation in solar irradiation influence that accumulation. Using field measurements and a relationship between stem basal area and aboveground biomass, we estimated current biomass levels in an 11-year-old chaparral stand, and used growth-ring diameters to estimate growth in each year from age 4 to 11 years. We found that annual growth as measured by shrub growth rings tracked closely with patterns of annual precipitation, but not with time since fire. Solar irradiation was not found to be a significant covariate with total biomass by plot, possibly due to sampling area limitations. The close relationship of annual biomass accumulation with annual precipitation indicates that shrub growth-ring measurements can provide a useful metric of stand-level recovery. [ABSTRACT FROM AUTHOR]

Wood formation is the primary biological process through which carbon is durably sequestered in woody plants, and is thus a major contributor to mitigate climate change. We analyzed the tree growth patterns of four conifer species across the Iberian Peninsula (IP) based on a dense dendrochronological network (179 sites) combined with a high resolution climate dataset. Generalized linear-mixed models were used to predict the potential tree growth of different pine species under different climate conditions considering different age classes. We found a strong age dependency of tree growth, significant variations across the climate gradients, and a significant interaction of both age and climate effects on the four species considered. Overall, Pinus halepensis was the species with the highest climate sensitivity and the highest growth rates in all age classes and across its distribution area. Due to its stronger plastic character and its potential adaptability, Pinus halepensis was demonstrated to be the most suitable species in terms of tree growth and potentiality to enhance carbon sequestration in the IP. Since its potential distribution largely exceeds its actual distribution, P. halepensis arises as a key species to cope with future climate conditions and to keep fixing carbon regardless of the climatic circumstances.

The Tibetan Plateau holds some of the world's highest undisturbed natural treelines and timberlines. Such extreme environments constitute potentially valuable monitoring sites of the effects of climate warming on high-elevation forests. Here, we analyze a network of 21 Smith fir forests situated in the Sygera Mountains, southeastern Tibetan Plateau, using tree-ring width (TRW) and basal area increment (BAI) chronologies. Sampled sites encompassed a wide elevation gradient, from 3600 to 4400 m, including some treeline sites and diverse aspects and tree ages. In comparison with TRW series, BAI series better capture the long-term warming signal. Previous November and current April and summer temperatures are the dominant climatic factors controlling Smith fir radial growth. The mean inter-series correlations of TRW increased upwards, but the forest limit presented the highest potential to reconstruct past temperature variability. Moreover, the growth responses of young trees were less stable than those of trees older than 100 years. Climate warming is accelerating radial growth of Smith fir forest subjected to mesic conditions. Collectively, these findings confirm that the effects of site elevation and tree age should be considered when quantifying climate-growth relationships. The type of tree-ring data (BAI vs. TRW) is also relevant since BAI indices seem to be a better climatic proxy of low-frequency temperature signals than TRW indices. Therefore, site (e.g., elevation) and tree (e.g., age) features should be considered to properly evaluate the effects of climate warming on growth of high-elevation forests. [ABSTRACT FROM AUTHOR]

It is expected that extreme climate events such as droughts will increase in both severity and intensity as a consequence of forecasted climate change. Complementarity among tree species in resource acquisition strategy may reduce interspecific competition and increase the occurrence of facilitative interactions, resulting in an improved tree growth and resilience to extreme climatic events. However, the response of individual trees growing in more functionally diverse stands to extreme events is still under debate., We investigate the growth response of silver fir ( Abies alba) to an extreme drought event which occurred in 1985-1986 in the Central Spanish Pyrenees and how the growth and resilience of trees relate to their neighbourhood functional diversity, stand heterogeneity and intraspecific and interspecific competition. Dendroecological methods were used to reconstruct radial growth. We recorded all tree species living around each sampled tree and calculated indices of intra- and interspecific competition among coexisting trees. Functional diversity around each focal tree was calculated by using the Rao's quadratic entropy., Silver fir growth decreased significantly in response to the drought in the vast majority of trees, but most of them showed a growth recovery 3 years later. Despite most trees showed negative growth trends following the drought event (70%), those trees growing in more functionally diverse stands were more resilient, recovered more quickly and displayed greater growth and growth trends., Synthesis. The presented findings support the growing body of evidence that shows a positive impact of diversity on forest function. In addition, we provide a direct linkage between tree growth response to climate at the individual tree scale and a direct quantification of neighbourhood functional diversity and competition. An enhanced functional diversity facilitating a more efficient use of resources at the interspecific level and potentially increasing facilitative interactions contributes to lessening the negative impacts of extreme events as droughts on forest growth. [ABSTRACT FROM AUTHOR]

Funderburk, W.R.; Carter, G.A., and Anderson C.P., 2016. Evaluating the Influence of elevation and impact of hurricane Katrina on radial growth in slash pine ( Pinus elliottii var. elliottii Engelm) on Cat Island, Mississippi, U.S.A. Hurricane Katrina heavily affected the Mississippi barrier islands, in the northern Gulf of Mexico, on 29 August 2005. On Cat Island, Mississippi, field observations of geographic patterns in poststorm survival of slash pine ( Pinus elliottii var. elliottii Engelm) suggested that its growth and resiliency to storm impact may depend substantially on ground elevation. This hypothesis was tested by evaluating the lifetime mean radial growth rate (in millimeters per year), stem (trunk) diameter (in centimeters), the percentage of change in the radial growth rate for the initial 5-y period after the storm (2006-10) vs. the 5-y period before the storm (2001-05), and the yearly percentage increase in stem radius and basal area for 2001-10 with respect to high-accuracy GPS measurements of growth-site elevation. Radial growth declined after the storm and remained suppressed in 2006-10. However, simple regressions indicated no relationship between growth and elevation, either over the lifetime of the trees or on a yearly basis in 2001-10. Instead, radial growth was related to tree age and, most strongly, to reciprocal age. Notably, the relationship with age diminished while growth was suppressed in 2005-10. Although tree growth was not related to elevation, a future study will explore the mechanisms underlying an observed 0.5-m elevation threshold for slash pine existence on Cat Island. [ABSTRACT FROM AUTHOR]

Soil properties can buffer forest response to global climate change. However, it is unclear how soil characteristics, water availability and their interactions can affect drought response of trees. The aim of this study was to assess the influence of soil nutrients and physical soil properties on the growth sensitivity of Fagus sylvatica, Quercus spp., Fraxinus excelsior, Abies alba, Picea abies and Pinus sylvestris to drought in Central Europe., Yearly growth data from increment cores were obtained from 538 trees and combined with forest inventory and soil data at 52 sites covering a large gradient of water availability and C/N ratios in soil. Linear mixed-effects models were used to assess the species-specific growth responses to climate and soil properties for the period 1957-2006. The growth of the species was further projected across the full range of C/N and water availability observed at 1029 sites where soil and species cover-abundance data were available., Temperature, water and nutrient availability (C/N) were the most important factors for tree growth. Drought and low nutrient availability significantly reduced the growth of beech, ash, fir and spruce along the gradient. In contrast, the growth of pine and oak was little reduced on poor and dry sites, hence showing their competitive advantage over nutrient-demanding species under such conditions. The growth of ash and pine was enhanced at sites with high species abundance, whereas an opposite response was found for spruce. No clear relationships between growth and species abundance were found for beech, oak and fir., Synthesis. Our results suggest that assessing tree responses to climate change without considering simultaneously soil properties and climate may be misleading since soil nutrients can influence growth response of trees to drought. A detailed analysis of the influence of the soil characteristics on growth responses of trees is necessary to understand the sensitivity of tree species to global climate change. [ABSTRACT FROM AUTHOR]

Long-term (10 years) growth responses of residual trees to prescribed fire and thinning were evaluated using standard dendrochronological protocols to understand the broader effects of the treatments on mixed-oak forest ecosystems in southern Ohio. Analysis of 696 increment cores (348 trees ≥ 25 cm DBH; five species) from 80 0.1 ha permanent plots distributed evenly across four treatments (control, thin, thin + burn, burn) indicated substantial increase in tree basal area increment (BAI) following the treatment. Post-treatment mean BAI of trees from the three active treatments ranged from 20.52 to 23.55 cm 2 y −1 compared with pre-treatment values of 16.86–17.07 cm 2 y −1. BAI rates (averaging 15.13 and 16.33 cm 2 y −1, respectively, for pre- and post-treatments) in the control plots did not change much over time. Mechanical treatments were more effective than prescribed fire at enhancing BAI of trees. However, basal area growth depended to some degree on the severity of prescribed fire. Analysis of percent BAI change revealed an interesting temporal trend with moderate to major growth releases during the first 5-year post-treatment period, and a slight attenuation thereafter, suggesting the need for periodic application of treatments to sustain growth over a longer timescale. Growth responses varied greatly among species, with yellow-poplar and hickories exhibiting the highest and lowest post-treatment BAI rates of 31.11 and 15.71 cm 2 y −1, respectively. Given their variable growth responses, integrating residual trees into current monitoring programs may help in elucidating the consequences of prescribed fire and thinning on forest dynamics and development. [ABSTRACT FROM AUTHOR]

The effect of extreme climate events on ecosystems is an important driver of biotic responses to climate change. For forests, extreme drought has been linked to negative effects such as large-scale mortality and reduced primary production. However, the response of plant communities to extreme drought events remains poorly understood., We used mortality data from a long-term monitoring programme in the core of the focal species' ranges, in combination with annual growth data from tree-rings, to study the effect of, and recovery from, an extreme drought event. We examined both the intraspecific and interspecific drought response and explored how differential responses affect competitive dominance between the dominant species Fagus sylvatica and Quercus petraea., Mortality for the most drought-susceptible species, F. sylvatica, occurred alongside a temporary reduction in competition-induced mortality of Q. petraea, resulting in the long-term alteration of the relative abundance of the two species., Significant intraspecific variation occurred in post-drought recovery in surviving F. sylvatica, with two distinct cohorts identified. A prolonged recovery period was coupled with the failure to regain pre-drought growth levels in this species, whereas for Q. petraea, no severe drought impacts were observed. This species instead experienced competitive release of growth., Our results demonstrate that ecosystem responses to extreme drought can involve rapid, nonlinear threshold processes during the recovery phase as well as the initial drought impact. These sudden changes can lead to the reordering of dominance between species within communities, which may persist if extreme events become more frequent. [ABSTRACT FROM AUTHOR]

Abstract: To what extent do mistletoes contribute to growth decline in drought-prone forests? Can the rising atmospheric CO2 concentrations offset the negative impacts of drought and mistletoe infestation on tree growth? Long-term data on growth and intrinsic water use efficiency (iWUE) may allow answering both questions. We used dendrochronology to assess long-term changes in radial growth and iWUE in Scots pine (Pinus sylvestris) trees severely infested by mistletoe (Viscum album) as compared to non-infested trees. The relationships among tree variables and mistletoe infestation were quantified using structural equation models. Linear mixed-effects models of basal area increment as a function of climate were fitted to severely infested and non-infested trees. Infested trees showed higher stem and crown diameters because they grew faster than non-infested trees in the past. Mistletoe infestation enhanced defoliation and reduced radial growth for more than 10years prior to sampling, while iWUE was significantly lower on severely infested trees only for the last 5years. Severely infested trees had higher growth responsiveness to drought stress than non-infested trees. Although infested and non-infested trees displayed similar rising iWUE temporal trends, the combined effect of drought stress and mistletoe infestation caused a reduction in growth and reversed the CO2-induced increase of iWUE in infested trees. We conclude that rising atmospheric CO2 concentrations cannot compensate for the impacts of drought and mistletoe on tree growth and iWUE. [Copyright &y& Elsevier]

1. It is expected that climate warming will enhance tree growth of mountain conifer forests in cold regions. However, trees have shown unstable, age-related and site-dependent growth responses to climate throughout the past century, but information on the drivers controlling such responsiveness at the site and tree scales is lacking. We evaluated whether such changing growth responses are more influenced by site features, such as altitude, or by tree features, such as size and sapwood area. 2. We quantified the growth trends at the site and tree levels in Iberian Pinus uncinata forests using dendrochronology. Tree-ring width was converted to basal area increment (BAI) to assess the relationships between growth and site and tree variables over three time periods (1901-1994, 1901-1947, 1948-1994) using structural equation models. 3. Trees were older at higher altitudes, and the amount of sapwood decreased as trees aged. BAI trends were lower in the period 1948-1994 than in the period 1901-1947, that is, tree growth is decelerating, despite BAI values of both periods showing the reverse pattern. Sapwood area and, to a minor extent, tree age were the main positive and negative drivers, respectively, controlling BAI during the 20th century, whereas altitude played a minor role. 4. Synthesis. Our results highlight the relevance of tree individual characteristics as the main drivers modulating growth responses to climate warming. We conclude that climate warming will have a lower effect on radial growth in slow-growing high-elevation trees than in fast-growing low-elevation trees, which produce a greater sapwood area. Trees may become relatively insensitive to climate as they age and reach a size-related functional threshold linked to reduced sapwood production. [ABSTRACT FROM AUTHOR]

Forest decline has been attributed to the interaction of several stressors including biotic factors such as mistletoes and climate-induced drought stress. However, few data exist on how mistletoes are spatially arranged within trees and how this spatial pattern is related to changes in radial growth, responses to drought stress and carbon use. We used dendrochronology to quantify how mistletoe (Viscum album L.) infestation and drought stress affected long-term growth patterns in Pinus sylvestris L. at different heights. Basal area increment (BAI) trends and comparisons between trees of three different infestation degrees (without mistletoe, ID1; moderately infested trees, ID2; and severely infested trees, ID3) were performed using linear mixed-effects models. To identify the main climatic drivers of tree growth tree-ring widths were converted into indexed chronologies and related to climate data using correlation functions. We performed spatial analyses of the 3D distribution of mistletoe individuals and their ages within the crowns of three severely infested pines to describe their patterns. Lastly, we quantified carbohydrate and nitrogen concentrations in needles and sapwood of branches from severely infested trees and from trees without mistletoe. Mistletoe individuals formed strongly clustered groups of similar age within tree crowns and their age increased towards the crown apex. Mistletoe infestation negatively impacted growth but this effect was stronger near the tree apex than in the rest of sampled heights, causing an average loss of 64% in BAI (loss of BAI was ∼51% at 1.3 m or near the tree base). We found that BAI of severely infested trees and moderately or non-infested trees diverged since 2001 and such divergence was magnified by drought. Infested trees had lower concentrations of soluble sugars in their needles than non-infested ones. We conclude that mistletoe infestation causes growth decline and increases the sensitivity of trees to drought stress. [ABSTRACT FROM PUBLISHER]

Juniperus thurifera L. is an endemic conifer of the western Mediterranean Basin where it is subjected to a severe climatic stress characterized by low winter temperatures and summer drought. Given the trend of increased warming-induced drought stress in this area and the climatic sensitivity of this species, we expect a negative impact of climate change on growth and ecophysiological performance of J. thurifera in the harsh environments where it dominates. To evaluate this, we measured long- and short-term radial growth using dendrochronology, photosynthesis and water-use efficiency in males, females and juveniles in three sites in Central Spain. Climate was monitored and completed with historical records. Mean annual temperature has increased +0.2 °C per decade in the study area, and the main warming trends corresponded to spring (+0.2 °C per decade) and summer (+0.3 °C per decade). Radial growth and maximum photosynthesis peaked in spring and autumn. Positive photosynthetic rates were maintained all year long, albeit at reduced rates in winter and summer. Radial growth was enhanced by wet conditions in the previous autumn and by warm springs and high precipitation in summer of the year of tree-ring formation. Cloud cover during the summer increased growth, while cloudy winters led to impaired carbon gain and reduced growth in the long term. We argue that maintenance of carbon gain under harsh conditions (low winter temperatures and dry summer months) and plastic xylogenesis underlie J. thurifera's ability to profit from changing climatic conditions such as earlier spring onset and erratic summer rainfall. Our results highlight that not only the magnitude but also the sign of the impact of climate change on growth and persistence of Mediterranean trees is species specific. [ABSTRACT FROM PUBLISHER]

This study uses data from the International Tree-Ring Data Bank website and tree cores collected in the field to explore growth rate (basal area increment, BAI) relationships across age classes (from young to old) for eight tree species in the eastern US. These species represent a variety of ecological traits and include those in the genera Populus, Quercus, Pinus, Tsuga and Nyssa. We found that most trees in all age classes and species exhibit an increasing BAI throughout their lives. This is particularly unusual for trees in the older age classes that we expected to have declining growth in the later years, as predicted by physiological growth models. There exists an inverse relationship between growth rate and increasing age class. The oldest trees within each species have consistently slow growth throughout their lives, implying an inverse relationship between growth rate and longevity. Younger trees (< 60 years of age) within each species are consistently growing faster than the older trees when they are of the same age resulting from a higher proportion of fast-growing trees in these young age classes. Slow, but increasing, BAI in the oldest trees in recent decades is a continuation of their growth pattern established in previous centuries. The fact that they have not shown a decreasing growth rate in their old age contradicts physiological growth models and may be related to the stimulatory effects of global change phenomenon (climate and land-use history). [ABSTRACT FROM PUBLISHER]

[Display omitted] • Growth trend analysis in dry-marginal populations of 5 tree species in SE Europe. • Declining growth in Fagus and Tilia due to a deteriorating climate water balance. • Stable growth of the 3 Quercus species despite increasing climatic aridity. • Results suggest future species shifts from beech to oak in a warming climate. • Admixing oaks will make silviculture less susceptible to climate warming. Global warming and increasing drought severity are exposing temperate forests to increasing stress, challenging silvicultural decision making. Growth analyses in marginal tree populations at drought-induced range limits may provide valuable information on tree species' adaptive potentials and species-specific climate turning points. We studied the climate sensitivity and resilience to drought of radial growth, and long-term growth trends of mesic and rear-edge populations of Fagus sylvatica in comparison to three oak species (Quercus petraea, Q. frainetto, Q. cerris) and Tilia tomentosa in natural ecotones from mesic beech to xeric oak forests along three elevation transects in western Romania. Radial growth of all species was positively influenced by summer precipitation and low drought intensity, and negatively by high summer temperatures. The basal area increment (BAI) of F. sylvatica and T. tomentosa has declined in the last 10–20 years with warming and a deterioration of the summer water balance, while the three Quercus species maintained stable growth rates, though at lower BAI levels, suggesting a negative relationship between mean BAI and drought resistance among the five species. Growth reductions during three severe drought events (2000, 2003, 2012) were stronger, and growth resilience lower, in F. sylvatica and T. tomentosa than in the Quercus species, pointing at a thermal limit of beech at June–August temperatures of 20–21 °C. As the climate of the studied ecotones is similar to the predicted climate at colline/submontane elevation in Central Europe in about 50 years, a decline in beech growth and vitality is likely also in drought-affected regions in the distribution centre with future warming. Our results demonstrate that choosing stress-tolerant Q. petraea (as well as Q. frainetto and Q. cerris) instead of more productive timber species is a relatively safe option for Central European forestry in a warmer climate. [ABSTRACT FROM AUTHOR]

Productivity of old-growth beech forests in the Mediterranean Basin was measured by average stem basal area increment (BAI) of dominant trees at two mountain sites in the Italian Apennines. Both forests could be ascribed to the old-growth stage, but they differed markedly with regard to elevation (1000 vs. 1725 m a.s.l.), soil parent material (volcanic vs. calcareous), mean tree age (less than 200 years vs. 300 years), and stand structure (secondary old-growth vs. primary old-growth forest). Drought at the two sites was quantified by the self-calibrated Palmer Moisture Anomaly Index ( Z-index), and by the self-calibrating Palmer Drought Severity Index (PDSI) for summer (June through August) and the growing season (May through September). Dendroclimatological analyses revealed a moisture limitation of beech BAI at interannual (water availability measured by Z-index) and decadal scales (water availability measured by PDSI). Both BAI and water availability increased from 1950 to 1970, and decreased afterwards. Trees were grouped according to their BAI trends in auxological groups (growth-type chronologies), which confirmed that growth of most trees at both sites declined in recent decades, in agreement with increased drought. Because BAI is not expected to decrease without an external forcing, the patterns we uncovered suggest that long-term drought stress has reduced the productivity of beech forests in the central Apennines, in agreement with similar trends identified in other Mediterranean mountains, but opposite to growth trends reported for many forests in central Europe. [ABSTRACT FROM AUTHOR]

Abstract: Oak-dominated forests in northwestern Arkansas have recently experienced an oak mortality event associated with an unprecedented outbreak of a native insect, the red oak borer, Enaphalodes rufulus (Haldeman). To determine whether prior drought was associated with increased E. rufulus infestation level of Quercus rubra L. trees, we employed a suite of dendrochronological measurements from Q. rubra in affected forest stands. We examined patterns of tree growth and physiological indicators of stress including α-cellulose δ13C, intrinsic water-use efficiency (W i) and photosynthetic discrimination (Δ) in Q. rubra from 1954 to 2002. Basal area increment measurements revealed that Q. rubra with lower levels of E. rufulus infestation experienced approximately 20% greater stem growth than Q. rubra more severely infested for ∼17 years prior to the onset of high rates of Q. rubra mortality. This trend emerged immediately following a severe drought in 1979–1981 and continued through 2002, suggesting that drought influenced E. rufulus infestation levels of some Q. rubra trees. Indicators of tree carbon and water relations (δ13C, W i, and Δ) revealed no relationship with degree of E. rufulus infestation, except for Δ in 2000, when physiology likely was responding to the advanced stage of decline in heavily infested trees. δ13C, W i, and Δ responded to drought periods as predicted early in the study period, but lost their sensitivity to drought after differences emerged in stem growth rate with degree of infestation. Though reduced stem growth in heavily infested trees suggests these trees were negatively influenced by E. rufulus infestation, the lack of infestation response of δ13C, W i, and, for much of the study period, Δ, suggests that infestation had negligible influence on C–water relations. The study highlights how δ13C and δ13C-based parameters may not indicate variation in tree C–water relations when forest disturbances are associated with reductions in tree growth rates. [Copyright &y& Elsevier]

At 94 sites throughout the Gaspésie peninsula, Québec, tree growth patterns and variation in growth rate were examined to determine relationship of tree growth to specific pollutants. Canopy dominant Black Spruce ( Picea mariana, (Mill.) BSP) were selected at each site. Basal area increment (BAI) values were derived from increment cores and disks taken at breast height. A sigmoid model (Gompertz) to tree basal area was fitted and used as an estimate of tree growth. The residuals were used in association with other landscape variables to test the hypothesis that the tree-growth was reduced at the vicinity of the Murdochville smelter. Results showed that residuals were well explained by smelter distance, elevation, and slope exposition to the smelter emissions. On the intense activity period, tree growth was reduced within a 25-km radius of the smelter, on slopes exposed to the contaminant flow and located at elevation lower than 580 m. With the interruption of smelting activities, growth was recovered for survival trees. [ABSTRACT FROM AUTHOR]

The carbon isotope composition (δ13C, ‰) and discrimination (Δ, ‰) of old grown North American Pinus ponderosa Dougl. Ex P. et C. Laws. and European Pinus sylvestris L. were determined using trees grown under almost identical growing conditions in a mixed stand in Bralitz, Northeast Germany. Single-tree δ13C analyses of tree-ring cellulose of both species were carried out at a yearly resolution for the period 1901-2001 and the results compared with growth (basal area increment). Annual mean δ13C values for P. ponderosa ranged from-21.6 ‰ to-25.2 ‰ and for P. sylvestris from-21.4 ‰ to-24.4 ‰. Accordingly, 13C discrimination (Δ) showed higher values for P. ponderosa throughout the investigation period. Five characteristic periods of Δ were identified for both the tree species, reflecting positive and negative influences of environmental factors. Good growing conditions such as after-thinning events had a positive effect on Δ, reflecting higher values, while poor conditions like aridity and air pollution had a negative influence, reflecting lower values. The dynamics of Δ were likewise reflected in the growth (basal area increment, BAI). Higher 13C discrimination values of P. ponderosa led to higher BAIs of P. ponderosa in comparison with P. sylvestris. Correlation function analyses confirmed that P. sylvestris was more dependent on precipitation than P. ponderosa, which showed a closer relationship with temperature. The results confirm that under predominantly dry growing conditions, P. ponderosa showed better growth performance than P. sylvestris, indicating better common intrinsic water-use efficiency and, therefore, higher rates of net photosynthesis at a given transpiration. In view of the prospect of climate change, the results are very significant for assessing both trees' physiological properties and, hence, their potential for coping with future growing conditions. [ABSTRACT FROM AUTHOR]

• Tree diameter estimated from the sum of ring-widths of tree-rings underestimates the true diameter. • Forest productivity metrics that rely on tree-ring-estimated diameters are underestimated due to diameter estimation bias. • A model calibrated with diameter measurements performed better at estimating diameter from tree ring data. • Model-estimated diameter produced better estimations of BAI and biomass than diameter derived from the sum of ring widths. Above-ground forest productivity can be reliably estimated from tree-ring width measurements. In doing so, annual growth is linked to the tree's basal area increment (BAI), which is the change in cross-sectional area associated with each annual ring. When BAI is estimated from ring-width series, a value for the diameter of the tree is required. This diameter is ideally measured in the field, but can also be estimated as the sum of the annual ring widths. Tree biomass can also be estimated directly from the diameter estimates derived from tree-rings. Summing the ring widths, however, typically underestimates the tree's true diameter. To evaluate this potential bias in diameter, we compared field-measured diameter and diameter estimated from the sum of the ring widths using tree-ring chronologies for seven common species in the eastern United States. We then evaluated the impacts of using the biased diameter estimates on derived BAI and biomass values. To simulate field-sampling error (i.e., failure to reach the pith when obtaining a core sample), we re-calculated BAI and biomass after removing a portion of the innermost rings from each tree. Comparisons of these various methods quantify the substantial and consistent underestimations in forest productivity estimates. To reduce the bias in diameter when using ring widths, we developed a regression model to adjust the diameter using core samples. This model is predicated on having some field-measured diameter values available at a site to calibrate and validate the model, but it can then be used to produce estimates at similar sites with similar species where no field-measured diameter values are available. Values of BAI and biomass derived from model-estimated diameter were more accurate at representing absolute growth than values produced by using the sum of the ring widths. Assessing the interannual variations in tree-growth is dependent on having metrics that accurately reflect the area and mass of wood produced. Our results suggest that published estimates of BAI and biomass using the sum of the ring widths to estimate diameter have substantially underestimated these productivity metrics. Our new procedure allows for more reliable estimates of productivity metrics that use diameter-at-breast height derived from tree rings. [ABSTRACT FROM AUTHOR]

Using a dendrochronological approach, we determined the resistance, recovery and resilience of the radial stem increment towards episodes of growth decline, and the accompanying variation of 13C discrimination against atmospheric CO2 (Δ13C) in tree rings of two palaeotropical pine species. These species co-occur in the mountain ranges of south–central Vietnam (1500–1600 m a.s.l.), but differ largely in their areas of distribution (Pinus kesiya from northeast India to the Philippines; P. dalatensis only in south and central Vietnam and in some isolated populations in Laos). For P. dalatensis, a robust growth chronology covering the past 290 years could be set up for the first time in the study region. For P. kesiya, the 140-year chronology constructed was the longest that could be established to date in that region for this species. In the first 40 years of the trees' lives, the stem diameter increment was significantly larger in P. kesiya, but levelled off and even decreased after 100 years, whereas P. dalatensis exhibited a continuous growth up to an age of almost 300 years. Tree-ring growth of P. kesiya was negatively related to temperature in the wet months and season of the current year and in October (humid transition period) of the preceding year and to precipitation in August (monsoon season), but positively to precipitation in December (dry season) of the current year. The P. dalatensis chronologies exhibited no significant correlation with temperature or precipitation. Negative correlations between BAI and Δ13C indicate a lack of growth impairment by drought in both species. Regression analyses revealed a lower resilience of P. dalatensis upon episodes of growth decline compared to P. kesiya, but, contrary to our hypothesis, mean values of the three sensitivity parameters did not differ significantly between these species. Nevertheless, the vigorous growth of P. kesiya, which does not fall behind that of P. dalatensis even at the margin of its distribution area under below-optimum edaphic conditions, is indicative of a relatively high plasticity of this species towards environmental factors compared to P. dalatensis, which, in tendency, is less resilient upon environmental stress even in the "core" region of its occurrence. [ABSTRACT FROM AUTHOR]

• Urban forest patches experience warmer air temperatures than reference forests. • Elevated calcium, magnesium, and heavy metal concentrations found in urban forest soils. • Faster tree growth in urban vs. reference forest sites, particularly in recent decades • Urban vs. reference basal area increment varies by species, by city, and over time. • Changes in white oak latewood ratio may relate to urban precipitation patterns over time. [ABSTRACT FROM AUTHOR]