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The legacy of disturbance on individual tree and stand-level aboveground biomass accumulation and stocks in primary mountain Picea abies forests

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... The structure of a street tree assemblage affects its supply of ecosystem services in an analogous manner to natural forests in which forest structure (e.g. age structure, density and canopy cover) affects ecosystem services (Trotsiuk et al. 2016). ...
... This result is consistent with those of other studies on urban ecosystem services (Liu et al. 2019b, Li et al. 2020a), but is not attributable to the issue of limited apace. Total stored carbon is linked to aboveground biomass accumulation, which is positively related to tree size at the individual tree level (Trotsiuk et al. 2016). As noted by Trotsiuk et al. (2016), competition is a crucial factor affecting the trajectory of aboveground biomass variation at the stand level. ...
... Total stored carbon is linked to aboveground biomass accumulation, which is positively related to tree size at the individual tree level (Trotsiuk et al. 2016). As noted by Trotsiuk et al. (2016), competition is a crucial factor affecting the trajectory of aboveground biomass variation at the stand level. However, unlike trees in stands, those in street tree assemblages do not interact. ...
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Urban afforestation is an important strategy for promoting sustainable urban development. In cities where large new green spaces are not available, the planting of curbside trees is deemed to be an important afforestation strategy. However, variations in the ecosystem services provided by street tree assemblages across socioeconomic gradients have been unexplored. We examined such variations in ecosystem services provided by street tree assemblages along an urban–suburban continuum. Our findings were as follows. (i) Not all ecosystem services showed increasing trends along the urban–suburban continuum. Some ecosystem services at the street tree assemblage level, such as air purification and rainfall interception were prominent in areas of high urbanization intensity. (ii) Diverse ecosystem service trends were found in relation to differential characteristics of street trees assemblages. Structural properties of street tree assemblages, such as tree density and age structure, are likely key factors influencing variations. (iii) Although street tree density could partially compensate for the loss of large old trees, the protection of such trees is important because of their close associations with key ecosystem services, such as total carbon storage. To maximize the value of street trees in promoting urban sustainable development, trade-offs among multiple ecosystem services should be integrated within the overall planning process and adjustments of planting regimes.
... The study of a tree's growth patterns, that is, the changes in treering width from the pith to the last formed ring, helps to overcome this problem by making it possible to identify growth releases and also determine how the tree reacted to this release Trotsiuk et al., 2016). However, the identification of growth patterns has tended to be, at least partially, based on a subjective process, thereby limiting its use (Frelich, 2002;Lorimer & Frelich, 1989;Niukkanen & Kuuluvainen, 2011). ...
... Most of the studied trees were defined by a sine or ascending growth pattern, indicating that black spruce and balsam fir reacted vigorously to the canopy openings caused by spruce budworm outbreaks. Both patterns are generally defined by a major increase in radial growth, a phenomenon observed in coniferous-dominated old-growth forests in North America and Europe Morin, 1994;Trotsiuk et al., 2016). Trees defined by a linear pattern were generally the smaller and younger individuals, reflecting suppressed trees that did not benefit from a canopy opening (Rossi et al., 2009;Trotsiuk et al., 2016) or that were unable to sufficiently increase their growth following gap creation. ...
... Both patterns are generally defined by a major increase in radial growth, a phenomenon observed in coniferous-dominated old-growth forests in North America and Europe Morin, 1994;Trotsiuk et al., 2016). Trees defined by a linear pattern were generally the smaller and younger individuals, reflecting suppressed trees that did not benefit from a canopy opening (Rossi et al., 2009;Trotsiuk et al., 2016) or that were unable to sufficiently increase their growth following gap creation. ...
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en In boreal landscapes, emphasis is currently placed on close‐to‐nature management strategies, which aim to maintain the biodiversity and ecosystem services related to old‐growth forests. The success of these strategies, however, depends on an accurate understanding of the dynamics within these forests. While moderate‐severity disturbances have recently been recognized as important drivers of boreal forests, little is known about their effects on stand structure and growth. This study therefore aimed to reconstruct the disturbance and postdisturbance dynamics in boreal old‐growth forests that are driven by recurrent moderate‐severity disturbances. We studied eight primary old‐growth forests in Québec, Canada, that have recorded recurrent and moderately severe spruce budworm (Choristoneura fumiferana [Clem.]) outbreaks over the 20th century. We applied an innovative dendrochronological approach based on the combined study of growth patterns and releases to reconstruct stand disturbance and postdisturbance dynamics. We identified nine growth patterns; they represented trees differing in age, size, and canopy layer. These patterns highlighted the ability of suppressed trees to rapidly fill gaps created by moderate‐severity disturbances through a single and significant increase in radial growth and height. Trees that are unable to attain the canopy following the disturbance tend to remain in the lower canopy layers, even if subsequent disturbances create new gaps. This combination of a low stand height typical of boreal forests, periodic disturbances, and rapid canopy closure often resulted in stands constituted mainly of dominant and codominant trees, similar to even‐aged forests. Overall, this study underscored the resistance of boreal old‐growth forests owing to their capacity to withstand repeated moderate‐severity disturbances. Moreover, the combined study of growth patterns and growth release demonstrated the efficacy of such an approach for improving the understanding of the fine‐scale dynamics of natural forests. The results of this research will thus help develop silvicultural practices that approximate the moderate‐severity disturbance dynamics observed in primary and old‐growth boreal forests. Résumé fr Dans les paysages boréaux, l'accent est désormais mis sur des stratégies de gestion proches de la nature afin de maintenir la biodiversité et les services écosystémiques liés aux vieilles forêts. Le succès de ces stratégies dépend toutefois d'une compréhension fine de la dynamique de ces forêts. Les perturbations de sévérité modérée ont ainsi été récemment reconnues comme étant d’importants moteurs de la dynamique des forêts boréales, mais l’on sait encore peu de choses de leur influence sur la structure et la croissance des peuplements. Par conséquent, l'objectif de cette étude est de reconstruire les dynamiques de perturbation et post‐perturbation dans les vieilles forêts boréales causées par des perturbations récurrentes de sévérité modérée. Nous avons étudié huit vieilles forêts primaires au Québec, Canada, ayant enregistré des épidémies de tordeuse des bourgeons de l'épinette (Choristoneura fumiferana [Clem.]) récurrentes et de sévérité modérée au cours du 20ème siècle. Nous avons utilisé une approche dendrochronologique innovante combinant l’étude des patrons et des reprises de croissance pour reconstruire la dynamique de perturbation et post‐perturbation de ces forêts. Nous avons identifié neuf patrons de croissance, observés dans des arbres d'âge, de taille ou de strate de canopée différents, indiquant des dynamiques particulières. Ces patrons ont mis en évidence la capacité des arbres opprimés à rapidement combler les trouées dans la canopée en un unique et significatif accroissement de circonférence et de hauteur. En revanche, les arbres déjà situés dans la canopée ont eu peu d'influence sur la fermeture de ces trouées. En conséquence, les arbres dominants et codominants étaient les plus fréquents dans la canopée. Les résultats de cette étude soulignent la résistance des vieilles forêts boréales aux perturbations récurrentes et de sévérité modérée, car les arbres du sous‐étage peuvent rapidement combler les trouées qui en résultent. Cependant, les arbres incapables d’atteindre le sommet de la canopée à la suite d’une perturbation resteront ensuite souvent dans les strates inférieures de la canopée, même si des perturbations subséquentes créent ensuite de nouvelles trouées. La combinaison de la faible hauteur des arbres typique des forêts boréales, des perturbations périodiques et de la rapide fermeture des trouées forme des peuplements avec une structure verticale ressemblant à celle des forêts équiennes. Globalement, cette étude souligne la résistance des vieilles forêts boréales en raison de leur capacité à supporter des perturbations répétées de sévérité modérée. De plus, l’étude combinée des patrons et des reprises de croissance démontre l’efficacité de cette approche pour reconstruire la dynamique à échelle fine des forêts naturelles. Les résultats de cette recherche contribueront ainsi à développer des pratiques sylvicoles analogues à la dynamique de perturbation de sévérité modérée observée dans les vieilles forêts primaires des paysages boréaux.
... Small-scale canopy disturbances would be caused by the death of a single or a few trees, partial tree breakage or decline due to disease, repeated drought, or other factors (Manion, 1981) rather than large-scale synchronous disturbances like logging, wind-throw or crown fires (Runkle, 1985). Low tree slenderness and relatively open canopies in our study forest reduce the probability of large disturbances from agents like wind-throw compared to closed-canopy forests (Trotsiuk et al., 2016;Martin-Benito et al., 2020) because less slender trees have a lower risk of wind breakage (Jackson et al., 2019). In addition, tree external characteristics and ring patterns showed no signs of pollarding, common in many old oaks in northern Spain (Rozas, 2005), further evidencing the old-growth state of our study forest. ...
... Productivity of old-growth forests is usually lower than that of younger or secondary forests (Kutsch et al., 2009). Our estimated annual wood productivity of trees present at the time of sampling (~1.47 Mg·ha −1 ·year −1 ) was on the low end of temperate forests (Keeling and Phillips, 2007;Dye et al., 2016;Trotsiuk et al., 2016) but remained stable for the last few decades. Because mortality rates are unknown for the study forest, information about trees that died before the time of sampling and were not present in the forest in 2018 (so-called ghost trees) is not inherently present or obvious (Foster et al., 2014). ...
... Biomass accumulation over long periods of time leads to large amounts of carbon stored in forests (Luyssaert et al., 2008). Above ground biomass in our study forest (200-400 Mg·ha −1 ) was within the range of mature oak-dominated forests (Druckenbrod et al., 2005;Balboa-Murias et al., 2006;Saniga et al., 2014) and other temperate old-growth forests (Keeling and Phillips, 2007;Trotsiuk et al., 2016). The average biomass stocks and the low productivity observed in our plots resulted in long turnover times (153-229 years) compared to estimates for other temperate forests (Keeling and Phillips, 2007;Berner et al., 2017). ...
Article
Most information on the ecology of oak-dominated forests in Europe comes from forests altered for centuries because remnants of old-growth forests are rare. Disturbance and recruitment regimes in old-growth forests provide information on forest dynamics and their effects on long-term carbon storage. In an old-growth Quercus petraea forest in northwestern Spain, we inventoried three plots and extracted cores from 166 live and dead trees across canopy classes (DBH ≥ 5 cm). We reconstructed disturbance dynamics for the last 500 years from tree-ring widths. We also reconstructed past dynamics of above ground biomass (AGB) and recent AGB accumulation rates at stand level using allometric equations. From these data, we present a new tree-ring-based approach to estimate the age of carbon stored in AGB. The oldest tree was at least 568 years, making it the oldest known precisely-dated oak to date and one of the oldest broadleaved trees in the Northern Hemisphere. All plots contained trees over 400 years old. The disturbance regime was dominated by small, frequent releases with just a few more intense disturbances that affected ≤20% of trees. Oak recruitment was variable but rather continuous for 500 years. Carbon turnover times ranged between 153 and 229 years and mean carbon ages between 108 and 167 years. Over 50% of AGB (150 Mg·ha⁻¹) persisted ≥100 years and up to 21% of AGB (77 Mg·ha⁻¹) ≥300 years. Low disturbance rates and low productivity maintained current canopy oak dominance. Absence of management or stand-replacing disturbances over the last 500 years resulted in high forest stability, long carbon turnover times and long mean carbon ages. Observed dynamics and the absence of shade-tolerant species suggest that oak dominance could continue in the future. Our estimations of long-term carbon storage at centennial scales in unmanaged old-growth forests highlights the importance of management and natural disturbances for the global carbon cycle.
... The study of a tree's growth patterns, that is, the changes in treering width from the pith to the last formed ring, helps to overcome this problem by making it possible to identify growth releases and also determine how the tree reacted to this release Trotsiuk et al., 2016). However, the identification of growth patterns has tended to be, at least partially, based on a subjective process, thereby limiting its use (Frelich, 2002;Lorimer & Frelich, 1989;Niukkanen & Kuuluvainen, 2011). ...
... Most of the studied trees were defined by a sine or ascending growth pattern, indicating that black spruce and balsam fir reacted vigorously to the canopy openings caused by spruce budworm outbreaks. Both patterns are generally defined by a major increase in radial growth, a phenomenon observed in coniferous-dominated old-growth forests in North America and Europe Morin, 1994;Trotsiuk et al., 2016). Trees defined by a linear pattern were generally the smaller and younger individuals, reflecting suppressed trees that did not benefit from a canopy opening (Rossi et al., 2009;Trotsiuk et al., 2016) or that were unable to sufficiently increase their growth following gap creation. ...
... Both patterns are generally defined by a major increase in radial growth, a phenomenon observed in coniferous-dominated old-growth forests in North America and Europe Morin, 1994;Trotsiuk et al., 2016). Trees defined by a linear pattern were generally the smaller and younger individuals, reflecting suppressed trees that did not benefit from a canopy opening (Rossi et al., 2009;Trotsiuk et al., 2016) or that were unable to sufficiently increase their growth following gap creation. ...
... More recently, a method called 'curve intervention detection' (CID) was developed to characterize disturbance history and quantify the effects of disturbance trends on individual RW series and chronology structure (Druckenbrod, 2005;Druckenbrod et al., 2013;Rydval et al., 2016). Previous studies have demonstrated that the CID method can be used to successfully identify disturbance events (Trotsiuk et al., 2016), represent land use history , characterize associated chronology trends , and isolate, remove and reduce the influence of disturbance trends on RW chronologies, leading to improved climate signal strength (Rydval et al., , 2017b(Rydval et al., , 2018. ...
... The timing and magnitude of disturbance trends in RW chronologies, represented by the difference between disturbance-affected (RW_dis) and disturbance-corrected (RW_dis_CID) chronologies, was generally consistent with the disturbance history (represented by the percentage of series with a release in a particular period), although these two datasets were not entirely synchronized. The disturbance impact on tree growth can persist for years (Jacquet and Altermatt, 2020;Thom et al., 2017;Trotsiuk et al., 2016) due to the longer-term changes in resource availability and competitive changes, which can offset the recorded timing of the disturbance event (i.e., release year) and the actual growth release trend in the series or chronology. Furthermore, differences in the magnitude of disturbance trends varied among sites, with BEL, BYS and URS displaying more considerable differences in chronology structure compared to HLI and FA2 (Figs. 3 and 4). ...
Article
Tree radial growth is influenced by climatic and various non-climatic factors, which can complicate the extraction of climate signals from tree rings. We investigated the influence of disturbance on tree-ring width (RW) and latewood blue intensity (BI) chronologies of Norway spruce from the Carpathian Mountains to explore the extent to which disturbance can affect temperature signals in tree rings. Overall, ∼15000 high-elevation Norway spruce tree cores from 34 sites grouped into four regions (Slovakia, Ukraine, North and South Romania) were analyzed. The curve intervention detection (CID) method was applied to detect and correct identified disturbance trends. RW chronology structural comparisons were performed among disturbance-affected and disturbance-corrected chronologies for various spatial (regional / site) scales and sampling subsets. Structural comparisons were also performed for RW and BI chronologies developed from separate groups of series (i.e., disturbed, and undisturbed) for five sites exhibiting clear disturbance trends. Temperature sensitivity was assessed for all chronology variants of both parameters. We found that disturbance trends only affected RW chronologies at the site/subset scale with relatively small series replication and were not detected at the regional scale. Unlike RW, BI chronologies were generally unaffected by disturbance. BI data also contained much stronger growing season temperature signals, which appeared to be both spatially and temporally more coherent. Whereas highly replicated and spatially extensive datasets can help minimize or eliminate disturbance trends in RW chronologies, this potential influence should be considered when interpreting climatic signals in tree rings and reconstructing historical climate in weakly replicated periods. On the other hand, BI is a promising alternative tree ring parameter with stronger and more stable growing season temperature signals, whose seemingly disturbance-free chronology structure does not appear to suffer from this ecological bias, and therefore represents a more suitable parameter for dendroclimatological research.
... As LOTs eventually do get removed from the canopy, the postdisturbance advanced regeneration will undoubtedly benefit carbon sequestration Pugh et al., 2019;Trotsiuk et al., 2016), and offset potential increases in heterotrophic respiration from dead wood decomposition (Luyssaert et al., 2008). ...
... ecosystem dynamics. LOTs accumulate a disproportionately higher amount of biomass compared to smaller and younger trees(Fauset et al., 2015;Trotsiuk et al., 2016), and have a longer carbon residence time after a mortality event (i.e., as standing dead trees; Shu-miao et al., 2019). If LOTs continue responding incrementally to improving growing conditions, rising temperatures could elevate carbon uptake and increase forest biomass, which would certainly benefit carbon storage, at least in areas that avoid large-scale mortality events(Calfapietra et al., 2015;Gunn et al., 2014;Lindenmayer et al., 2012;Liu et al., 2013;Senf & Seidl, 2021a). ...
Article
In a world of accelerating changes in environmental conditions driving tree growth, tradeoffs between tree growth rate and longevity could curtail the abundance of large, old trees (LOTs), with potentially dire consequences for biodiversity and carbon storage. However, the influence of tree‐level tradeoffs on forest structure at landscape scales will also depend on disturbances, which shape tree size and age distribution, and on whether LOTs can benefit from improved growing conditions due to climate warming. We analyzed temporal and spatial variation in radial growth patterns from ~ 5000 Norway spruce (Picea abies (L.) H. Karst) live and dead trees from the Western Carpathian primary spruce forest stands. We applied mixed‐linear modeling to quantify the importance of LOT growth histories and stand dynamics (i.e. competition and disturbance factors) on lifespan. Finally, we assessed regional synchronization in radial growth variability over the 20th century, and modelled the effects of stand dynamics and climate on LOTs recent growth trends. Tree age varied considerably among forest stands, implying an important role of disturbance as an age constraint. Slow juvenile growth and longer period of suppressed growth prolonged tree lifespan, while increasing disturbance severity and shorter time since last disturbance decreased it. The highest age was not achieved only by trees with continuous slow growth, but those with slow juvenile growth followed by subsequent growth releases. Growth trend analysis demonstrated an increase in absolute growth rates in response to climate warming, with late summer temperatures driving the recent growth trend. Contrary to our expectation that LOTs would eventually exhibit declining growth rates, the oldest LOTs (> 400 years) continuously increase growth throughout their lives, indicating a high phenotypic plasticity of LOTs for increasing biomass, and a strong carbon sink role of primary spruce forests under rising temperatures, intensifying droughts, and increasing bark beetle outbreaks.
... Using the tree ring dataset [21], we also estimated contemporary carbon sequestration (mean rates of change in forest carbon stocks) based on total plot-level aboveground biomass increment (AGBI) averaged over the last 10 years [47]. Based on allometric models [43] (see the electronic supplementary material, table S1), we used annual DBH increases to estimate AGBI for all living plot trees for each year in the most recent 10 year interval preceding field surveys. ...
... As soon as the forest canopy closed, reduced light availability and more homogeneous forest structure resulted in decreased biodiversity potential. Meanwhile, carbon sequestration was highest immediately following disturbance, bolstered by the rapid growth of younger trees already in the understory owing to advanced regeneration [47]. By contrast, aboveground carbon storage was higher in old-growth forest development stages, particularly in large stems and dead wood [58,59]. ...
Article
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With accelerating environmental change, understanding forest disturbance impacts on trade-offs between biodiversity and carbon dynamics is of high socioeconomic importance. Most studies, however, have assessed immediate or short-term effects of disturbance, while long-term impacts remain poorly understood. Using a tree-ring-based approach, we analysed the effect of 250 years of disturbances on present-day biodiversity indicators and carbon dynamics in primary forests. Disturbance legacies spanning centuries shaped contemporary forest co-benefits and trade-offs, with contrasting, local-scale effects. Disturbances enhanced carbon sequestration, reaching maximum rates within a comparatively narrow post-disturbance window (up to 50 years). Concurrently, disturbance diminished aboveground carbon storage, which gradually returned to peak levels over centuries. Temporal patterns in biodiversity potential were bimodal; the first maximum coincided with the short-term post-disturbance carbon sequestration peak, and the second occurred during periods of maximum carbon storage in complex old-growth forest. Despite fluctuating local-scale trade-offs, forest biodiversity and carbon storage remained stable across the broader study region, and our data support a positive relationship between carbon stocks and biodiversity potential. These findings underscore the interdependencies of forest processes, and highlight the necessity of large-scale conservation programmes to effectively promote both biodiversity and long-term carbon storage, particularly given the accelerating global biodiversity and climate crises.
... Thus, are confirmed the previous observations (Assmann, 1970;Sillett et al., 2010) made in multi-storey stands with wide age differences, mostly for individual trees over 300 years old, according to which wood production of the entire tree (or stand) makes irregular progress, but the growth of diameter (and, consequently, of the volume) may continue long after height growth has slowed down. These findings suggest that the growth rate of older trees continuously increases with increasing size (Stephenson et al., 2014;Trotsiuk et al., 2016). ...
... Instead, after a period of accumulation, the growth rate remained constant or was diminished and other trees, of the same species in this studied case, took the initiative in biomass accumulation, so the community maintains the same pace of development as a whole. The same finding was reached in a study in primary mountain Norway spruce forests (Trotsiuk et al., 2016). ...
Article
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The trees’ ability to respond and adjust to very different growing conditions during their lifespans varies depending on tree species and the site-specific situations. Identifying the underlying mechanisms and the individual drivers that may affect the patterns of tree growth is crucial in ecological and economic terms. How long can forest trees grow and sustain biomass accumulation, with increasing age, is still under debate. In order to determine the factors that influence growth releases for silver fir (Abies alba Mill.) trees in a temperate old-growth forest of Romania's Southern Carpathians, an analysis of radial and basal area growth patterns was initiated. Dendroecological methods were used to reconstruct radial growth both at the individual level, but especially at the group level, in four clusters obtained by a prior k-cluster analysis depending on social status. The study results showed that the growth rate of older trees increases continuously for this species at stand level, even after the typical harvesting age in managed forests. Although the direction and intensity of the climate-growth correlations at individual level were very different, the considered climatic variables explaining little to none of the growth variation, the cumulative response of the analysed trees to climate change is directly correlated with the mean July-August temperature, confirming the capacity of the silver fir to tolerate drought. Our results demonstrate that the trees of the same species are able to obtain together a temporal plasticity in strategies, exceeding the adaptability of individuals considered separately and suggest the positive impact of facilitative intraspecific interactions on forest growth.
... A escolha do espaçamento de plantio influencia o desenvolvimento das plantas (Bouillet et al., 2013) e, como o crescimento está diretamente relacionada com a acumulação de biomassa (Trotsiuk et al., 2016), o que permite favorecer o reservatório de carbono de uma floresta. A aplicação de fertilizantes nitrogenados e calcário são práticas frequentemente utilizadas na condução e desenvolvimento deste tipo de espécies florestais (Vieira et al., 2015). ...
... O desenvolvimento da espécie nos primeiros anos é superior nos espaçamentos reduzidos (Lopes et al., 2017), porém com o passar dos anos, a maior competição por luz, nutrientes (Ghezehei et al., 2015) e menor taxa de mortalidade (Schumacher et al., 2011), faz com que os espaçamentos mais amplos consigam obter produtividades (Silva et al., 2016) e estocagem de carbono similares. O crescimento e maior volume de madeira das plantas tem relação direta com a estocagem de carbono, e são afetadas por fatores como qualidade do solo (Ueda et al., 2017), competição por luz (Coonen & Sillett, 2015), resistência a seca (Hänke et al., 2016), temperatura do local (Chen et al., 2017) e a susceptibilidade a pragas e doenças (Bett et al., 2016). ...
Article
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As plantações de eucalipto podem compensar as emissões de gases com efeito estufa (GEE) das atividades de fertilização e plantio, devido à capacidade das árvores em armazenar carbono na forma de biomassa. O objetivo deste estudo foi estimar o sequestro de carbono em plantações de eucalipto com diferentes densidades de instalação. O estudo foi conduzido no município de Lamim, no estado de Minas Gerais - Brasil, numa plantação de eucalipto dividida em quatro áreas de 0,25 ha com diferentes densidades de instalação. O diâmetro à altura do peito e altura total dos indivíduos foram obtidos por inventário florestal. A biomassa foi calculada pela multiplicação do volume e densidade básica da madeira. As emissões de GEE foram calculadas a partir dos dados de fertilização e calagem. O reservatório de carbono (90,94 MgCO2eq ha-1) e as emissões de GEE foram superiores no espaçamento de 2 x 1 m. A menor emissão de GEE por m3 de madeira produzido foi no espaçamento 2 x 2 m. O balanço de carbono foi positivo em todos os espaçamentos avaliados. Foi possível concluir que as florestas de Eucalipto são capazes de compensar as emissões de GEE da fertilização nitrogenada e calagem em plantações pouco tecnificadas.
... This interpretation is consistent with our second hypothesis, and is supported by our findings that both the date of the time since disturbance and the basal area of standing dead trees varied widely among plots within each stand. Time since disturbance was the most important variable in explaining variability in biomass at the within-stand scale, consistent with other studies in the Carpathian Mountains that found strong relationships between biomass and time since disturbance (Trotsiuk et al., 2016, Seedre et al., 2015. The high variability in time since disturbance within stands suggests that individual stands typically represent fine-grained mosaics of smaller patches that have had different time available for forest development since the last severe disturbance. ...
... We found that the negative correlation between time since disturbance and basal area of living trees was strengthened by disturbance severity (Sup. Fig. 5), indicating that stands recovering from similar disturbance severity follow similar developmental trajectories (Trotsiuk et al., 2016). Our model results showed that northness was moderately important for withinstand scale basal area, but not at the between-stand scale, suggesting that environmental effects can operate at small scales if within-stand variation in environmental characteristics is high. ...
Article
Disentangling the importance of developmental vs. environmental drivers of variation in forest biomass is key to predicting the future of forest carbon sequestration. At coarse scales, forest biomass is likely to vary along major climatic and physiographic gradients. Natural disturbance occurs along these broad biophysical gradients, and depending on their extent, severity and frequency, could either amplify or dampen spatial heterogeneity in forest biomass. Here we evaluate spatial variation in the basal area of late-successional Picea abies (L./Karst.) forests across the Carpathian Mountain Range of central Europe and compare the roles of coarse-scale biophysical gradients and natural disturbances in driving that variation across a hierarchy of scales (landscapes, stands, and plots). We inventoried forest composition and structure, and reconstructed disturbance histories using tree cores collected from 472 plots nested within 30 late-successional stands, spanning the Carpathian Mountains (ap-proximately 4.5 degrees of latitude). We used linear mixed-effects models to compare the effect of disturbance regimes and site conditions on stand basal area at three hierarchical scales. We found that the basal area of late-successional Picea abies forests varied across a range of spatial scales, with climatic drivers being most important at coarse scales and natural disturbances acting as the primary driver of forest heterogeneity at fine scales. For instance, the stand-level basal area varied among landscapes, with the highest values (48-68 m 2 ha −1) in the warmer southern Carpathian Mountains, and lower values (37-52 m 2 ha −1 on average) in cooler areas of the eastern and western Carpathians. Finer-scale variation was driven by local disturbances (mainly bark beetle and windstorms) and the legacies of disturbances that occurred more than a century ago. Our findings suggest that warming could increase the basal area of northern sites, but potential increasing disturbances could disrupt these environmental responses.
... In contrast, periodic low-to moderate-severity disturbances (e.g., windthrow or partial insect outbreaks) create multi-layered canopies that contribute to more structurally complex forests (i.e., old-growth forest structure; Halpin and Lorimer 2016). Mixed-severity disturbance regimesdefined by high spatiotemporal variability in both severity and frequency-also influence forest structural features, such as biomass and age structure, as observed by, for example, Trotsiuk et al. (2016) and Janda et al. (2017) in forests dominated by Norway spruce (Picea abies (L.) Karst.) in the Carpathian Mountains. We know of no existing literature that explores forest spatial patterns and accounts the local disturbance history. ...
... Plot age was estimated using the mean age of the five oldest trees at each plot; this is considered to be a suitable method for estimating plot age in multi-cohort stands subjected to mixedseverity disturbance regimes (Di Filippo et al. 2016, Trotsiuk et al. 2016, Janda et al. 2017). To estimate the stand age, the mean of all plot ages was calculated. ...
Article
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The role of density dependence in shaping spatial patterns in tree distributions presumably changes throughout stand development. However, empirical investigations into developmental processes are often limited by a lack of long-term data on disturbance history, which further limits the ability to assess the role of spatial variation in site conditions (e.g., slope, aspect, mean annual temperature). This study included data from 289 plots within 26 primary forest stands of the Carpathian Mountains; stands were dominated by Norway spruce (Picea abies) and driven by mixed-severity disturbance regimes. We assessed spatial patterns in living tree positions, tree diameters, and the relative position of living trees to dead trees. Random forest classification was used to discriminate between disturbance history, tree density, and site conditions and their effects on the observed spatial patterns. At the stand scale, distances between trees of equal diameter were more uniform that expected (tree diameter was showing repulsion), while tree positions and dead trees were mostly distributed randomly. The processes that best explained the spatial patterns were identified as self-thinning mortality and past disturbances (100–150 yr). This study demonstrated that the plot and stand-scale spatial patterns resulted from the combination of past disturbances and density-dependent legacies derived from earlier forest development stages.
... Trotsiuk et al. 2012). The long history of human land-use and small tracts of old-growth forest (Nagel et al. 2007) might be the reason that many tree-ring studies have been conducted in secondgrowth forests (Cherubini et al. 1996;Emborg et al. 2000;Rozas 2001Rozas , 2004Rozas et al. 2008) or at small spatial scales in old-growth forests (Piovesan et al. 2005;Splechtna et al. 2005;Nagel et al. 2007;Svoboda et al. 2012;Trotsiuk et al. 2016). Dendroecological research at broad spatial scales will help in testing the hypothesis that regional to continental-scale disturbance is important in the longterm development of TMFs in Europe. ...
... While there are many potential reasons for this, we focus on a few key factors. First, the small scale of most dendroecological studies likely limits the potential to observe the full spatial extent of past disturbance, though see (Rentch 2003;D'Amato and Orwig 2008;Trotsiuk et al. 2014Trotsiuk et al. , 2016. Second, there is a miniscule amount of remaining old-growth forest in TMFs, and the common longevity of trees in these forests, from 300-400 years (Di Filippo et al. 2015), likely limits the discovery of LIDs. ...
Chapter
Temperate, mesic forests (TMFs) are generally viewed as being in a shifting-mosaic or a kind of dynamic equilibrium at broad spatial scales. Gaining insight to the potential dynamics of TMFs at large-scales is crucial because these species-rich, highly productive forests are important drivers of regional water and carbon cycles for approximately one billion people.
... Carbon stock data include aboveground and belowground biomass, as well as deadwood, consisting of snags and CWD necromass. The aboveground biomass carbon increment was calculated based on the aboveground biomass increment (Trotsiuk et al. 2016) for the last ten years according to the increase determined from annual rings and converted to biomass according to allometric equations. Due to different years of collecting data, we set 2013 as the final year for analysis. ...
... cattle grazing) use of forest resources (Coelho et al. 2020;Lingner et al. 2020). Forest stand story, especially the magnitude of past disturbances and time since disturbance can decrease present AGB (Pflugmacher et al. 2014;Trotsiuk et al. 2016). ...
Article
Background: Above-ground biomass (AGB) and its temporal dynamics are key parameters of forest ecosystems, related to their resilience and capacity to fix atmospheric carbon. AGB is related to species richness, composition, forest structure, soils and climate. In human-modified landscapes, fragmentation and human pressure may change the nature of these relationships. Aims: Our aim was to quantify how species richness and composition, leaf area index, and edge effect were related to biomass stocks and growth in fragmented subtropical secondary forests. Methods: We tested the relationship between leaf area index, tree species richness and composition, edge effect and AGB stocks in secondary forest stands in the Atlantic Forest using multiple linear models on data from 104 sites. Results: Our results show that biomass stocks were related to species richness, distance to forest edge and the interaction of both (R 2 = 0.25; p < 0.05). Biomass change showed positive relationships with pioneer species richness and distance to edge, and negative relationship with the interaction of total species richness and distance to edge (R 2 = 0.15; p < 0.05). Conclusion: Edge effect can affect AGB dynamics directly and indirectly, by weakening the positive effects of species richness and composition on biomass. AGB loss at some sites suggests that some fragments are under chronic disturbance or may be experiencing delayed mortality due to fragmentation.
... By 20 years of age, the forests showed a substantial increase in biomass, reaching an average of 102.3 tons per hectare. This phase represents a critical period in forest development where biomass accumulation is stabilized, reflecting the attainment of a nearly mature forest structure characterized by a closed canopy and maximum tree size [26]. Finally, at 25 years old, the forests reached their peak biomass levels, with an average of 235.65 tons per hectare. ...
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Understanding the ecological dynamics of forest ecosystems, particularly the influence of forest age structure on soil carbon (C), nitrogen (N), and phosphorus (P) content, is crucial for effective forest management and conservation. This study aimed to investigate the nutrient storage and ecological stoichiometry across different-aged stands of Chinese fir forests. Soil samples were collected from various depths (0–15 cm, 15–30 cm, and 30–45 cm) across four age groups of Chinese fir forests (8-year-old, 12-year-old, 20-year-old, and 25-year-old) in the Forest Farm, Pingjiang County, China. Soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) were measured, and their stoichiometries were calculated. The results showed that both individual tree biomass and stand biomass, along with SOC, TN, and TP content, increased with stand age, highlighting the significant importance of stand age on biomass production and nutrient accumulation in forests. Specifically, soil C and P contents significantly increased as the forest aged, while variation in N content was relatively minor. Soil C/N and C/P ratios exhibited variation corresponding to forest age, suggesting alterations in the ecological stoichiometry characteristics of the forests over time. These findings are crucial for understanding the dynamics of ecosystem functioning and nutrient cycling within Chinese fir forests and provide a solid scientific basis for the effective management and conservation of these vital forest ecosystems.
... Forests play a crucial role in mitigating climate change by sequestering carbon dioxide from the atmosphere (Khaine and Woo, 2015), and their conservation and sustainable management are essential for maintaining global carbon balance (Köhl et al., 2020). Trees, as the primary components of forest ecosystems, are major contributors to carbon storage through biomass accumulation (Trotsiuk et al., 2016). Monitoring and quantifying biomass and carbon in trees are fundamental tasks for understanding the carbon dynamics in forests (Goetz et al., 2012), assessing the effectiveness of reforestation efforts, and informing climate change mitigation strategies (Canadell and Raupach, 2008). ...
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Comparative analysis at Brackenhurst Campus, Nottingham, explores the effectiveness of LiDAR versus manual measurements for carbon quantification in trees across varying areas. LiDAR provides detailed 3D scans remotely, aiding in accurate carbon quantification, while manual methods offer a cost-effective solution for larger areas. Choice between methods should consider area size and research objectives, with LiDAR favored for smaller, data-intensive projects and manual methods for larger-scale assessments.
... Prolonged meteorological drought can result in soil moisture deficiency, adversely affecting vegetation growth and even causing vegetation death Li et al., 2020;Chang et al., 2016). As a crucial component of the ecosystem, vegetation contributes to mitigating the greenhouse effect and maintaining the global carbon balance (Trotsiuk et al., 2016;Simon et al., 2012). The rising carbon dioxide (CO 2 ) concentration in the atmosphere, however, contributes to further warming of the Earth, leading to more widespread and severe droughts (Gauthier et al., 2014;Barkhordarian et al., 2019;Swann, 2018). ...
... associated with the growth curves of trees because annual net carbon sequestration has been shown to be positively correlated with middleaged forests, which exhibit the maximum growth rate (Trotsiuk et al. 2016, Yao et al. 2022. Therefore, the number of middle-aged trees in a given area of green space has a greater influence on ESS CS compared with the area of a green space. ...
Article
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It is widely acknowledged that synergetic supplies of multiple ecosystem services (ESs) can improve the efficiency of multifunctional landscape management. However, even though the satisfaction of demands for ESs clearly and comprehensively reflects their efficiency, little is known about the efficiency of co-benefits for multiple ESs when both the supply and demand sides are considered. For the first time, we analyzed the co-benefits of the supply of and demand for multiple ESs in urban areas according to the degrees of synergy found among five typical urban ESs. We found that although supplies of multiple ESs were synergetic, and the degrees of synergy of single ES supply-demand were positively correlated with each other, the co-benefits of supply-demand for multiple ESs were not substantial. We also found that the demand for ESs critically affects ES efficiency, which should therefore be assessed from the perspectives of both supply and demand. Any initiative that focuses on just one aspect cannot bring about genuine synergy; nor can it prompt the re-entry of the natural ecosystem in urban areas into a positive cycle. We elucidated the different patterns of synergy that foster a balance in the supply and demand of multiple ESs, which can provide a basis for their differentiation and for grouped management approaches to enhance the co-benefits of the supply of and demand for multiple ESs. Evidently, the supply side of ESs requires attention, especially the key aspect of ecological processes that affect the synergy of ES supplies. Consequently, an in-depth exploration of the key ecological process affecting ES supplies and their synergy is warranted in the future.
... Drought is one of the most economically and ecologically destructive extreme events, profoundly impacting terrestrial ecosystem processes (Yi et al., 2012;Allen et al., 2015;Gao et al., 2018). Vegetation also plays a crucial role in terrestrial ecosystems, contributing to mitigation of the greenhouse effect and promoting balance in the global carbon flux (Simon et al., 2012;Trotsiuk et al., 2016). Of all the vegetation types, forests may be the most vulnerable to drought . ...
Article
Since the 1990s, global warming has substantially affected the dynamic responses of forest ecosystems to drought by altering tree growth and ecosystems carbon cycling. The Loess Plateau is a typical vegetation recovery region with an arid and semiarid climate. However, the responses of the vegetation in this region to drought have not been fully studied. We therefore aimed to characterize these responses in tree-ring samples, which were obtained by drilling tree cores with a growth cone, for establishing the tree-ring width chronologies. In addition, we investigated the main factors controlling the radial growth of Chinese pine (Pinus tabulaeformis) and its dynamic responses to drought in the Loess Plateau using correlation analysis. Our results show that radial growth in Chinese pine had a positive correlation with precipitation during the last growing season, pre-growing season, and entire current growing season. The correlation between the radial growth and temperature was inconsistent between different sampling sites and time periods. These suggest that precipitation was more likely to affect radial vegetation growth than temperature. Moreover, the drought indices calculated using data before the year 2000 more accurately reflected the vegetation drought situation in Loess Plateau than data from the last 20 years. The drier the place, the more accurately the drought indices represented the responses of vegetation to drought. However, these indices cannot satisfactorily capture the drought responses of vegetation in wet regions. Furthermore, the PDSI was more accurate than the SPEI at capturing the effects of drought on radial vegetation growth. Understanding the response mechanism of the radial growth of Chinese pine to drought can provide theoretical support for ecological protection, forest management, and ecological construction under climate change.
... Additionally, a range of recent studies highlights the negative effects of salvage logging on forest biodiversity, such as bird species , saproxylic insects (Koz ak et al., 2021), fungi and other specialist species that require a diverse forest structure with high amounts of deadwood (e.g., Zemanov a, 2017; Thorn et al., 2018). The relevance of suppressing bark beetle outbreaks in commercial forests is foremost understandable (e.g., Toth et al., 2020), but bark beetle attacks do not necessarily have a negative impact on the forest ecosystem, as was found in particular in studies on the long-term effect of large disturbances on forest biomass (Trotsiuk et al., 2016;Seedre et al., 2020), forest hydrology (Kop a cek et al., 2020) and water quality (Beudert et al., 2014). While most arguments about bark beetle attacks as a negative effect on ecosystem services are currently contradicted by other studies, the perception of the public and of policy makers on bark beetle outbreaks generally remains negative (Werner et al., 2006;Müller, 2011;Mikusi nski and Niedziałkowski, 2020). ...
Article
Temperate mountain forests have experienced an increase in frequency and severity of natural disturbances (e.g., droughts, fires, windstorms and insect outbreaks) in recent decades due to climate and environmental change. Outbreaks of bark beetles have caused significant dieback of conifer forests in Central Europe and it is essential to model and predict the potential severity of future bark beetle outbreaks. However, to predict future bark beetle activity, historical baseline information is required to contextualize the magnitude of current and potential future outbreaks. A fossil beetle record from a forest hollow in the Tatra Mountains, Slovakia; one of the best-preserved national parks in Central Europe, was produced to identify insect outbreaks during the last millennia. Sub-fossil bark beetle re-mains were compared with parallel pollen and charcoal to assess whether peaks in conifer bark beetle remains correspond with indications of disturbance documented in historical or sedimentary fossil records. Three peaks in bark beetle remains were detected (1) post-2004, (2) AD 1140-1440, and (3) AD930-1030. The abundance of speciesPityogenes chalcographusandPityophthorus pityographus in the two top samples can be linked directly to large bark beetle outbreaks in the High Tatra Mountains after 2004. P. chalcographus and P. pityographus are also the abundant species in the second peak (AD 1140e1440) while the third peak (AD 930e1030) consists of the species Polygraphus poligraphus. The most prominent conifer bark beetle in Central Europe, Ips typographus, was found to be present in most of the samples but always at very low numbers. It is plausible that P. chalcographus and P. pityographus fossils might be useful proxies for past conifer bark beetle outbreaks in Central Europe, as they occur together with fossils of I. typographus but appear to be well-preserved. A significant correlation was found between primary bark beetles and macroscopic charcoal densities in the sediment, highlighting the complex interactions between disturbance agents, bark beetles and fire, in this long-term regime of natural disturbances. Our 1400-year disturbance record shows how bark beetle outbreaks have been an important component of the regional natural disturbance regime for over a millennium and have intensified with increasing anthropogenic activity. Bark beetle outbreaks are likely one of the drivers promoting the future ecological stability of the temperate conifer ecosystem over decades to centuries.
... Unlike forest stand biomass estimation, forest biomass and tree size are strongly related at the individual tree scale [45,46]. LiDAR remote sensing has been shown to be able to measure forest biophysical parameters automatically with high accuracy [47]. ...
Article
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Accurate forest biomass estimation at the individual tree scale is the foundation of timber industry and forest management. It plays an important role in explaining ecological issues and small-scale processes. Remotely sensed images, across a range of spatial and temporal resolutions, with their advantages of non-destructive monitoring, are widely applied in forest biomass monitoring at global, ecoregion or community scales. However, the development of remote sensing applications for forest biomass at the individual tree scale has been relatively slow due to the constraints of spatial resolution and evaluation accuracy of remotely sensed data. With the improvements in platforms and spatial resolutions, as well as the development of remote sensing techniques, the potential for forest biomass estimation at the single tree level has been demonstrated. However, a comprehensive review of remote sensing of forest biomass scaled at individual trees has not been done. This review highlights the theoretical bases, challenges and future perspectives for Light Detection and Ranging (LiDAR) applications of individual trees scaled to whole forests. We summarize research on estimating individual tree volume and aboveground biomass (AGB) using Terrestrial Laser Scanning (TLS), Airborne Laser Scanning (ALS), Unmanned Aerial Vehicle Laser Scanning (UAV-LS) and Mobile Laser Scanning (MLS, including Vehicle-borne Laser Scanning (VLS) and Backpack Laser Scanning (BLS)) data.
... Considering that episodes of disturbance had occurred in many of the studied stands, up until 1970s in the most recent cases (Fig. 3), they can be considered as recovering high levels of live biomass. The capacity for biomass recovery was also reported by Trotsiuk et al. (2016), who concluded that 40-50 years is sufficient for recovery of 90% of aboveground stand biomass after low disturbance (20-40% of canopy removed) in primary Picea abies mountain forests. ...
Article
The important role that forests play in the global carbon cycle has led to the implementation of management practices to enhance long-term carbon storage in forests. Obtaining information about how forest biomass varies at different successional stages is therefore essential. In this study, we aimed (i) to determine the relationship between stand live biomass and the degree of naturalness (i.e. the degree to which forests dynamics are driven by natural processes in the absence of anthropogenic influences) in undisturbed, mature forests, and (ii) to establish the upper threshold of live biomass stock that is dependent on site quality, by using the site form (SF) index (dominant height-diameter relationship). We assessed live biomass stocks in a total of 10 undisturbed mixed and pure mature silver fir (Abies alba Mill.) and European beech (Fagus sylvatica L.) stands across the Spanish Pyrenees. We used dendrochronology and chrono-functional indicators to assess the degree of naturalness and to detect growth releases as proxies for past disturbance. We compared data from the mature plots and data from the Spanish National Forest Inventory (NFI), for similar forest types and SF values, to determine whether maximum live biomass values were reached in the plots. We observed that live biomass stock was generally independent of naturalness. The forests characterized by the lowest degrees of naturalness held similar amounts of live tree biomass as those characterized by the highest degrees of naturalness, including old-growth forests. Although some stands had undergone severe disturbance in the past, in all but two plots the live biomass stocks reached maximum values at the respective SF values, unlike in the NFI plots. The study findings contribute to the body of evidence supporting the existence of an upper threshold of live biomass stock represented by undisturbed mature stands. Maximum live carbon stock appears to be reached at earlier stages than the old-growth stage. This finding has consequences for biomass and carbon management and may be useful for developing forest policies involving carbon sequestration aimed at mitigating climate change.
... Forest energy plantations play an essential role in the carbon storage. Fast-growing forest plantations are considered highly efficient carbon sinks capable of contributing to the mitigation of the increase of CO 2 levels in the atmosphere (Laclau 2003;Coleman 2018;Trotsiuk et al. 2015;Bhattacharya 2019). ...
Article
Key message The use of reduced planting spacings is an important strategy to increase the carbon storage in the above-belowground biomass and should be recommended for future exploitation of forest energy plantations when the purpose intended is the production of biomass for energy. ContextRecent concerns about global warming have resulted in more concerted studies on quantifying carbon storage in forest systems. Forest energy plantations play an essential role in the carbon storage.AimsWe proposed to evaluate the carbon storage and partitioning in short-rotation forest plantations and to characterize the elemental composition and energetic properties of the forest species Eucalyptus grandis W. Hill ex Maiden, Mimosa scabrella Benth, and Ateleia glazioviana Baill, grown under four planting spacings in Southern Brazil.MethodsA field study was conducted in order to evaluate forest carbon stock and wood composition using samples collected by direct method. The four spacings evaluated were 2.0 × 1.0, 2.0 × 1.5, 3.0 × 1.0, and 3.0 × 1.5 m.ResultsThe Eucalyptus grandis stored 327.1 Mg C ha−1 at 2.0 × 1.5-m spacing. When compared with the 3.0 × 1.5-m spacing, we observed a reduction of 29% in carbon stored. All forest species showed higher carbon storage in the following partitioning pattern: trunk>roots>branches>leaves>litter. Forest species energetic properties and elemental composition were not affected by planting spacing. On the other hand, variations according the tree portions were observed. For the carbon stocks in the soil, we observed an average accumulated carbon stock for the forest species studied of 77.4 Mg C ha−1 (0–40 cm).Conclusion Forest managers can accelerate growth and increase the forest carbon storage and biomass yield by using reduced planting spacing that are smaller than the current pattern used by the majority of the forest producers, which is 3.0 × 1.5 m. For Eucalyptus grandis and Mimosa scabrella, the planting spacings recommended to produce biomass and improve carbon stocks were 2.0 × 1.5 and 2.0 × 1.0 m, respectively.
... Our first objective was to identify growth rate anomalies in individual tree growth series indicative of disturbances and the subsequent recruitment of the individual to the canopy stratum. Doing so required us to identify two unique growth patterns reflecting distinct modes of canopy recruitment: a high initial growth rate in the first 15 years of a tree's life, termed Gap Recruited Trees (GRT), or an abrupt and sustained increase in growth following an interval of competitive suppression, termed Released Trees (RT) (Lorimer and Frelich, 1990;Svoboda et al., 2014;Trotsiuk et al., 2016). ...
Article
While shifting disturbance rates and climate change have major implications for the structure of contemporary forests through their effects on adult tree mortality, the responses of regenerating trees to disturbances and environmental variation will ultimately determine the structure and functioning of forests in the future. Assessing the resilience of forests to changing conditions requires information on what constrains tree performance during recruitment and whether recruitment dynamics have changed throughout history. We analyzed growth patterns in a large sample of tree cores (n = 14 793) collected from primary Picea forests throughout the Carpathian Mountains. Growth rate anomalies recorded in tree-rings permitted the reconstruction of several key recruitment and disturbance parameters: (1) whether individuals were recruited after a period of competitive suppression (Released Trees; RT; 66% of trees) or immediately following gap formation (Gap Recruited Trees; GRT; 33%), (2) growth rates during recruitment, (3) the duration of recruitment and (4) historical disturbance severity variation. High neighborhood density led to lower growth rates in RTs, but favored a higher growth rate in GRTs. Winter temperatures were positively correlated with Picea growth during recruitment, GRTs were also more sensitive to winter precipitation. Recent increases in growth during recruitment and reductions in recruitment intervals suggest that rates of canopy replacement have increased over recent decades. Assessments of forest resilience must recognize that constraints on tree growth differ during recruitment and interact with disturbance severity. An individual's experience prior to competitive release and factors altering the immediate abiotic conditions of a recruiting individual (competition and disturbance severity) are important determinants of canopy replacement rates; these recruitment parameters will certainly interact with shifting disturbance regimes. Ultimately, increasing growth rates and decreasing recruitment intervals suggest that forest dynamics are accelerating, and are potentially compensating for recent increases in tree mortality rates.
... For example, bimodal or multimodal trends have been observed in these forests [51,84,85], which are two patterns that are absent from our results. However, the patterns identified in this study are very similar to those highlighted by Trotsiuk et al. [86] in European primary forests dominated by Norway spruce (Picea abies (L.) Karst.). Nevertheless, it is likely that slow-growth patterns, i.e., low-descending, linear, and high-ascending patterns, can be divided into several sub-patterns. ...
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Research Highlights: Radial growth patterns of trees growing in old-growth boreal forests in eastern Canada can be grouped into a small number of simple patterns that are specific to different old-growth forest types or successional stages. Background and Objectives: Identifying the main radial growth trends in old-growth forests could help to develop silvicultural treatments that mimic the complex dynamics of old-growth forests. Therefore, this study aimed to identify the main radial growth patterns and determine how their frequencies change during forest succession in old-growth forests, focusing on boreal landscapes in eastern Canada. Materials and Methods: We used dendrochronological data sampled from 21 old-growth stands in the province of Quebec, Canada. Tree-ring chronologies were simplified into chronologies of equal length to retain only primary growth trends. We used k-means clustering to identify individual growth patterns and the difference in growth-pattern frequency within the studied stands. We then used non-parametric analyses of variance to compare tree or stand characteristics among the clusters. Results: We identified six different growth patterns corresponding to four old-growth forest types, from stands at the canopy breakup stage to true old-growth stands (i.e., when all the pioneer cohort had disappeared). Secondary disturbances of low or moderate severity drove these growth patterns. Overall, the growth patterns were relatively simple and could be generally separated into two main phases (e.g., a phase of limited radial increment size due to juvenile suppression and a phase of increased radial increment size following a growth release). Conclusions: The complexity of old-growth forest dynamics was observed mainly at the stand level, not at the tree level. The growth patterns observed in true old-growth forests were similar to those observed following partial or stem-selection cuts in boreal stands; thus, these silvicultural treatments may be effective in mimicking old-growth dynamics.
... This was partially due to the release of shade-tolerant species such as balsam fir and red spruce in the understories and lower canopy positions of the stands. Other studies have documented recovery of stand-level biomass and rapid accumulation of biomass on shade-tolerant trees that were suppressed in lower canopy positions following low-severity disturbance (Trotsiuk et al. 2016). Trees in the upper canopy positions that survived disturbances also benefited from increased resource availability and higher resistance to drought (D'Amato et al. 2013), which resulted in increased stand-level C stocks over time. ...
Article
Carbon (C) storage and accumulation in forests is of growing importance as climate change focuses our attention on rising greenhouse gas emissions. In 2012, we measured total ecosystem C pools (including live vegetation, dead wood, and soils) in two unmanaged, mixed-species stands in central Maine, USA. The stands are adjacent to one another and serve as references against which silvicultural treatments can be compared. The soil parent material of the stands was different (marine sediments versus glacial till), which provided an ideal opportunity to compare C stocks between these stands. We used tree ring analysis and repeated forest inventories to estimate tree and dead wood recruitment patterns and past disturbance severity. Site quality influenced C trajectories through its influence on tree species composition, which in turn strongly determined stand susceptibility to insect outbreaks. In 2012, total ecosystem C stocks were 196.3 ± 9.6 Mg ha–1 (mean ± SD) in the stand on soils derived from marine sediments and 247.0 ± 17.7 Mg ha–1 in the stand on soils derived from glacial till. Differences in average total ecosystem C stocks were primarily driven by the live tree C pool. Despite the occurrence of several partial disturbance events from 1954 to 2012, live tree C stocks increased over time in both stands. Average C accumulation in recruited dead wood was also positive, indicating that aboveground biomass served as a C sink. Our results can be used to inform decisions related to C objectives in unmanaged stands of similar species composition and soils.
... In these forests, stand-replacing disturbances are uncommon, and forest dynamics is driven by disturbances highly varying in severity (Meigs et al., 2017). Since mostly not all trees are killed, structural development after disturbances continues in diverse paths with varying amounts of live and dead tree biomass (Trotsiuk et al., 2016). This is fundamentally different from a stand-replacing disturbance, after which development starts from a state of near zero live biomass. ...
Article
Accurate estimations of changes in the forest carbon (C) pools over time are essential for predicting the future forest C balance and its part in the global C cycle. While the overall understanding of global forest C dynamics has improved, some significant forest ecosystem processes have been largely overlooked, resulting in possible biases. As an example, the effects of low and moderate severity disturbances have received disproportionately little attention. In this study, we use an extensive database of 9610 tree increment cores from 400 plots in primary uneven-aged Norway spruce (Picea abies) forests in the Carpathian Mountains, to explore the dynamics of live and dead wood C after disturbance. The data represents a chronosequence of more than 250 years since disturbance, varying highly in severity. We found that disturbance severity had a substantial impact on the post-disturbance long-term accumulation of C. Initially, live tree C accumulated at a similar rate independent of disturbance severity. However, the increase in C leveled off earlier after low disturbance severity while the most heavily disturbed forests continued to accumulate C to the latest stages of stand development. These results stress the importance of taking disturbance severity into account when predicting the long-term dynamics of C storage in forests under climate change. The results also highlight the importance of these forests as significant C pools. If harvested and turned into managed forest they would not reach their maximum C storing capacity.
... The plots, where tree cores were sampled, were established following approaches outlined in Trotsiuk et al. (2016) and Schurman et al. (2018). ...
Article
A tree's radial growth sequence can be thought of as an aggregate of different growth components such as age and size limitations, presence or absence of disturbance events, continuous impact of climate variability and variance induced by unknown origin. The potentially very complex growth patterns with prominent temporal and spatial variability imply that our understanding of climate-vegetation feedbacks essentially benefits from the expansion of large tree ring networks into data-poor regions, and our ability to disentangle growth constraints by comparing ring series at multiple scales. In this study, we analyze Central-Eastern Europe's most substantial assemblage of primary Norway spruce forests found in the Carpathian arc. The vast data set, >10,000 tree-ring series, is stratified along a prominent gradient in climate response space over four separate landscapes. We integrated curve intervention detection and dendroclimatic standardization to decompose tree growth variance into climatic, disturbance and residual components to explore the behavior of the components over increasingly larger spatial hierarchies. We show that the residual variance of unknown origin is the most prominent variance in individual Carpathian spruce trees, but at larger spatial hierarchies, climate variance dominates. The variance induced by climate was further explored with common correlation analyses, growth response to extreme climate years and forward modeling of tree growth to identify leading modes of climate response, and potentially non-linear and mixed climate response patterns. We find that the climatic response of the different forest landscapes overall can be described as an asymptotic response to June and July temperatures, most likely intermixed with influence from winter precipitation. In the collection of landscapes, Southern Romania stands out as being the least temperature sensitive and most likely exhibiting the most complicated mixed temperature and moisture limitation.
... The ITRDB is a treasure trove for records of tree growth variability, both in space and time. However, in order to answer broad-scale ecological questions, and improve our understanding of forest vulnerability to climate change across forest biomes, dendrochronological sampling designs must be more representative-not just within a site 29 , but also spatially by covering an ecological gradient 30,31 or with a systematic grid 20,32 . We are optimistic that the establishment of a new data standard on the ITRDB (TRiDaS 33 ) that allows additional information about sites (slope, aspect, stand density, soil depth, etc.) and trees (diameter, height, pith offset, etc.) to be readily shared will improve the value and versatility of publicly available data for ecological forecasts of forested ecosystems. ...
Article
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Climate−tree growth relationships recorded in annual growth rings have recently been the basis for projecting climate change impacts on forests. However, most trees and sample sites represented in the International Tree-Ring Data Bank (ITRDB) were chosen to maximize climate signal and are characterized by marginal growing conditions not representative of the larger forest ecosystem. We evaluate the magnitude of this potential bias using a spatially unbiased tree-ring network collected by the USFS Forest Inventory and Analysis (FIA) program. We show that U.S. Southwest ITRDB samples overestimate regional forest climate sensitivity by 41–59%, because ITRDB trees were sampled at warmer and drier locations, both at the macro- and micro-site scale, and are systematically older compared to the FIA collection. Although there are uncertainties associated with our statistical approach, projection based on representative FIA samples suggests 29% less of a climate change-induced growth decrease compared to projection based on climate-sensitive ITRDB samples.
... We cannot expect productivity to be strictly associated with asymmetry if factors other than size dominance play a major role in creating stand biomass growth dynamics. To date, no clear consensus has emerged regarding the primary factor driving structural biomass growth in diverse temperate forests, although evidence suggests climate (Pederson et al. 2014), disturbance legacies (Trotsiuk et al. 2016), competition (Zhang et al. 2015), and stand age (Foster et al. 2016) can be important factors. Most likely, size-growth dynamics result from a complicated interaction of each of these factors and others. ...
Article
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Modeling and forecasting forests as carbon sinks require that we understand the primary factors affecting productivity. One factor thought to be positively related to stand productivity is the degree of asymmetry, or the slope of the relationship between tree size and biomass growth. Steeper slopes indicate disproportionate productivity of big trees relative to small trees. Theoretically, big trees outcompete smaller trees during favorable growth conditions because they maintain better access to light. For this reason, high productivity forests are expected to have asymmetric growth. However, empirical studies do not consistently support this expectation, and those that do are limited in spatial or temporal scope. Here, we analyze size–growth relationships from 1970 to 2011 across a diverse network of forest sites in the eastern United States (n = 16) to test whether asymmetry is consistently related to productivity. To investigate this relationship, we analyze asymmetry-productivity relationships between our 16 forests at non-overlapping annual, 2-, 5-, 10-, and 20-year sampling intervals and find that asymmetry is negatively related to productivity, but the strength depends on the specific interval considered. Within-site temporal variability in asymmetry and productivity are generally positively correlated over time, except at the 5-year remeasurement interval. Rather than confirming or failing to support a positive relationship between asymmetry and productivity, our findings suggest caution interpreting these metrics since the relationship varies across forest types and temporal scales.
... Biomass accumulation in high-elevation forests 29 2007), wind throws and wildfires (Seidl et al. 2011;Trotsiuk et al. 2016), and insect activity (Hicke et al. 2012;Klapwijk et al. 2013). This array of physiological, ecological, biogeographical, and environmental controls on tree growth generates uncertainty in predicting the future role of European forests as a carbon sink (Ciais et al. 2008;Nabuurs et al. 2013). ...
Thesis
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Conifers show a biogeographical distribution across a wide range of contrasting environmental conditions, stretching from the Arctic Circle to the equator and Southern Hemisphere. In mountainous ecosystems, conifers can dominate at high elevations with low temperatures severely limiting tree growth and survival. Conifers growing at sites with temperature limiting conditions are highly sensitive to ongoing climatic change, where warmer and drier conditions will impact their growth. Understanding how high-elevation conifers will respond to these changes in climate is critical, as they play a role in regulating terrestrial carbon storage (facilitated by the formation of woody tissue) and water balance (by releasing water to the atmosphere via transpiration). The environmental regulation of wood formation (i.e., tracheid development in conifers), which dictates annual ringwidth patterns, is commonly associated with the tree’s photosynthetic activity, while other growth-limiting factors might also be relevant. For example, tree growth requires turgidity in the cambium to exert the pressure necessary for cell expansion, assimilates to lengthen and thicken cell walls, warmth to allow the metabolic reactions to take place, and time for these processes to be completed. Yet, an in-depth study on how important tree hydraulics (i.e., transpiration dynamics) are in regulating “turgor-driven” growth in high elevation forests is lacking. As part of the LOTFOR project, the general objective of this work is to develop a better mechanistic understanding on how tree hydraulics and environmental factors interact in regulating wood formation and shaping tree rings in highelevation conifer trees. More specifically, the coupling between stem hydrological cycles and structural carbon dynamics is investigated in the context of increasing temperature and water scarcity. This thesis combines multi-annual records of both intra-annual wood formation data and high-resolution hydraulic measurements within a mechanistic growth model to explain inter- and intra-annual tree growth patterns. To simulate the impact from recent climate change on these mechanisms, a space-for-time experimental setting is applied within the Lötschental, located in the Swiss Alps, where we collected data of two commonly occurring conifer species (Larix decidua Mill. and Picea abies Karst. L.) along an elevation/thermal gradient and contrasting wet and dry sites. Additionally, evaluations are performed on existing methodologies for measuring sap flow and handling large wood anatomical datasets.
... Individual tree growth is also influenced by competition from neighboring trees, and in a carbon accounting context it becomes critical to quantify, understand, and project such demographydriven changes in forest growth (Chen et al., 2016;Trotsiuk et al., 2016). Capturing the influence of competition on individual tree growth is also key to scaling step B (Fig. 4) because individual tree growth both influences and is influenced by forest stand basal area, forming a self-regulating (density-dependent) feedback. ...
Article
The demand for large-scale and long-term information on tree growth is increasing rapidly as environmental change research strives to quantify and forecast the impacts of continued warming on forest ecosystems. This demand, combined with the now quasi-global availability of tree-ring observations, has inspired researchers to compile large tree-ring networks to address continental or even global-scale research questions. However, these emergent spatial objectives contrast with paleo-oriented research ideas that have guided the development of many existing records. A series of challenges related to how, where, and when samples have been collected is complicating the transition of tree rings from a local to a global resource on the question of tree growth. Herein, we review possibilities to scale tree-ring data (A) from the sample to the whole tree, (B) from the tree to the site, and (C) from the site to larger spatial domains. Representative tree-ring sampling supported by creative statistical approaches is thereby key to robustly capture the heterogeneity of climate-growth responses across forested landscapes. We highlight the benefits of combining the temporal information embedded in tree rings with the spatial information offered by forest inventories and earth observations to quantify tree growth and its drivers. In addition, we show how the continued development of mechanistic tree-ring models can help address some of the non-linearities and feedbacks that complicate making inference from tree-ring data. By embracing scaling issues, the discipline of dendrochronology will greatly increase its contributions to assessing climate impacts on forests and support the development of adaptation strategies. https://authors.elsevier.com/c/1XWsP-4PRq7xR (free access until Sep 27)
... The long-term spontaneous development of forest ecosystems in the study area will lead to the creation of valuable habitats for numerous endangered species (Götmark 2013). As non-interventionist forest management undoubtedly contributes to an increase of dead wood in the ecosystem, it will affect the biodiversity of organisms that depend on dying trees and various forms of decomposing wood (Trotsiuk et al. 2016). A gradual increase in dead wood biomass (notably fallen spruce trees on the ground) will probably lead to the natural regeneration of spruce, as spruce seedlings in mountain areas grow best on the decaying trunks of dead trees (Senfeldr & Maděra 2011). ...
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... (1810) (Zemanová et al., 2017;Olsson et al., 2011;Pechacek and d'Oleire-Oltmanns, 2004). In addition, salvage logging seriously hampers various ecosystem processes in primary forests, including natural regeneration, nutrient cycling, and carbon storage (Bače et al., 2012;Trotsiuk et al., 2016;Anderegg et al., 2016). ...
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Primary forests are characterized by high vertical and horizontal stand diversity, which provides habitat for a diverse range of species with complex habitat requirements. Detailed knowledge of related ecological processes and habitat development of primary forest species are essential to inform forest management and biodiversity conservation decisions, but relationships are not well documented. We collected dendrochronological data and inventoried numerous structural elements in permanent plots throughout the primary temperate forests within the Carpathian Mountains. We fit and compared multiple predictive models to quantify the importance of 200 years of natural disturbance dynamics on the occurrence probability of an umbrella species – the capercaillie (Tetrao urogallus). We showed that a mixed-severity disturbance regime ranging from low through moderate to high severity disturbances is required to generate diverse forest habitats suitable for capercaillie. The variation in natural disturbance severity and its timing promoted key structural habitat elements, such as low natural regeneration density, low mature tree density, high ground vegetation cover, availability of forest gaps, and abundance of standing deadwood. This study demonstrates the importance of natural disturbance in maintaining the variety of conditions necessary to support primary forest specialist species. Managers of protected areas should be mindful that natural disturbances generate habitat for the capercaillie in mountain Norway spruce forests. Further intervention is unnecessary. Conservation planning and forest reserve design should shift focus to the large-scale spatial requirements needed to ensure that a wide range of forest developmental phases are represented in protected areas.
... Forest inventory data, satellite imaging, and model simulations often show non-consistent patterns of forest net primary productivity and biomass responses to climate change (Fang et al., 2001;Nemani et al., 2003;Etzold et al., 2014;Wu et al., 2014). Some of this uncertainty is caused by challenges in adequately incorporating various drivers affecting forest productivity, including: management practises, forest age and structure (Lindner et al., 2010;Nabuurs et al., 2013;Pretzsch et al., 2014), nutrient and CO 2 fertilization (Hyvönen et al., 2007), windthrows and wildfires (Seidl et al., 2011;Trotsiuk et al., 2016), and insect activity (Hicke et al., 2012;Klapwijk et al., 2013). This array of physiological, ecological, biogeographical, and environmental controls on tree growth generates uncertainty in predicting the future role of European forests as a carbon sink (Ciais et al., 2008;Nabuurs et al., 2013). ...
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Forest biomass growth is almost universally assumed to peak early in stand development, near canopy closure, after which it will plateau or decline. The chronosequence and plot remeasurement approaches used to establish the decline pattern suffer from limitations and coarse temporal detail. We combined annual tree ring measurements and mortality models to address two questions: first, how do assumptions about tree growth and mortality influence reconstructions of biomass growth? Second, under what circumstances does biomass production follow the model that peaks early, then declines? We integrated three stochastic mortality models with a census tree-ring data set from eight temperate forest types to reconstruct stand-level biomass increments (in Minnesota, USA). We compared growth patterns among mortality models, forest types and stands. Timing of peak biomass growth varied significantly among mortality models, peaking 20-30 years earlier when mortality was random with respect to tree growth and size, than when mortality favored slow-growing individuals. Random or u-shaped mortality (highest in small or large trees) produced peak growth 25-30 % higher than the surviving tree sample alone. Growth trends for even-aged, monospecific Pinus banksiana or Acer saccharum forests were similar to the early peak and decline expectation. However, we observed continually increasing biomass growth in older, low-productivity forests of Quercus rubra, Fraxinus nigra, and Thuja occidentalis. Tree-ring reconstructions estimated annual changes in live biomass growth and identified more diverse development patterns than previous methods. These detailed, long-term patterns of biomass development are crucial for detecting recent growth responses to global change and modeling future forest dynamics.
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Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle-particularly net primary productivity and carbon storage-increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.
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A methodology is proposed for developing a disturbance chronology in stands by identifying the probable date of canopy accession for each sample tree. Canopy disturbance intensity is defined as the percentage of sample trees with canopy accession events in each decade. Rotation periods for disturbances of various intensities are calculated from the chronology. The method was evaluated using 893 increment cores from 70 plots in northern hardwood stands of W Upper Michigan. Average disturbance rate for all plots and decades was 5.7-6.9% of land area per decade, with an implied average canopy tree residence time of 145-175 yr. -from Authors
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Questions: How have the historical frequency and severity of natural disturbances in primary Picea abies forests varied at the forest stand and landscape level during recent centuries? Is there a relationship between physiographic attributes and historical patterns of disturbance severity in this system? Location: Primary P. abies forests of the Eastern Carpathian Mountains, Romania; a region thought to hold the largest concentration of primary P. abies forests in Europe’s temperate zone. Methods: We used dendrochronological methods applied to many plots over a large area (132 plots representing six stands in two landscapes), thereby providing information at both stand and landscape levels. Evidence of past canopy disturbance was derived from two patterns of radial growth: (1) abrupt, sustained increases in growth (releases) and (2) rapid early growth rates (gap recruitment). Thesemethods were augmented with non-metricmultidimensional scaling to facilitate the interpretation of factors influencing past disturbance. Results: Of the two growth pattern criteria used to assess past disturbance, gap recruitment was the most common, representing 80% of disturbance evidence overall. Disturbance severities varied over the landscape, including stand-replacing events, as well as low- and intermediate-severity disturbances. More than half of the study plots experienced extreme-severity disturbances at the plot level, although they were not always synchronized across stands and landscapes. Plots indicating high-severity disturbances were often spatially clustered (indicating disturbances up to 20 ha), while this tendency was less clear for lowand moderate-severity disturbances. Physiographic attributes such as altitude and land form were only weakly correlated with disturbance severity. Historical documents suggest windstorms as the primary disturbance agent, while the role of bark beetles (Ips typographus) remains unclear. Conclusions: The historical disturbance regime revealed in this multi-scale study is characterized by considerable spatial and temporal heterogeneity,which could be seen among plots within stands, among stands within landscapes and between the two landscapes. When the disturbance regime was evaluated at these larger scales, the entire range of disturbance severity was revealed within this landscape.
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Aim Large trees (d.b.h. ≥ 70 cm) store large amounts of biomass. Several studies suggest that large trees may be vulnerable to changing climate, potentially leading to declining forest biomass storage. Here we determine the importance of large trees for tropical forest biomass storage and explore which intrinsic (species trait) and extrinsic (environment) variables are associated with the density of large trees and forest biomass at continental and pan‐tropical scales. Location Pan‐tropical. Methods Aboveground biomass ( AGB) was calculated for 120 intact lowland moist forest locations. Linear regression was used to calculate variation in AGB explained by the density of large trees. Akaike information criterion weights ( AICc ‐wi) were used to calculate averaged correlation coefficients for all possible multiple regression models between AGB /density of large trees and environmental and species trait variables correcting for spatial autocorrelation. Results Density of large trees explained c . 70% of the variation in pan‐tropical AGB and was also responsible for significantly lower AGB in Neotropical [287.8 (mean) ± 105.0 ( SD ) M g ha ⁻¹ ] versus Palaeotropical forests (Africa 418.3 ± 91.8 M g ha ⁻¹ ; Asia 393.3 ± 109.3 M g ha ⁻¹ ). Pan‐tropical variation in density of large trees and AGB was associated with soil coarseness (negative), soil fertility (positive), community wood density (positive) and dominance of wind dispersed species (positive), temperature in the coldest month (negative), temperature in the warmest month (negative) and rainfall in the wettest month (positive), but results were not always consistent among continents. Main conclusions Density of large trees and AGB were significantly associated with climatic variables, indicating that climate change will affect tropical forest biomass storage. Species trait composition will interact with these future biomass changes as they are also affected by a warmer climate. Given the importance of large trees for variation in AGB across the tropics, and their sensitivity to climate change, we emphasize the need for in‐depth analyses of the community dynamics of large trees.
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Stem diameter at breast height (DBH) and tree height (H) are commonly used measures of tree growth. We examined patterns of height growth and diameter growth along a stem using a 20-year record of an even-aged hinoki cypress (Chamaecyparis obtusa (Siebold & Zucc.) Endl.) stand. In the region of the stem below the crown (except for the butt swell), diameter growth rates (ΔD) at different heights tended to increase slightly from breast height upwards. This increasing trend was pronounced in suppressed trees, but not as much as the variation in ΔD among individual trees. Hence, ΔD below the crown can be regarded as generally being represented by the DBH growth rate (ΔDBH) of a tree. Accordingly, the growth rate of the stem cross-sectional area increased along the stem upwards in suppressed trees, but decreased in dominant trees. The stem diameter just below the crown base (DCB), the square of which is an index of the amount of leaves on a tree, was an important factor affecting ΔDBH. DCB also had a strong positive relationship with crown length. Hence, long-term changes in the DCB of a tree were associated with long-term changes in crown length, determined by the balance between the height growth rate (ΔH) and the rising rate of the crown base (ΔHCB). Within the crown, ΔD's were generally greater than the rates below the crown. Even dying trees (ΔD ≈ 0 below the crown) maintained ΔD > 0 within the crown and ΔH > 0 until about 5 years before death. This growth within the crown may be related to the need to produce new leaves to compensate for leaves lost owing to the longevity of the lower crown. These results explain the different time trajectories in DBH–H relationships among individual trees, and also the long-term changes in the DBH–H relationships. The view that a rise in the crown base is strongly related to leaf turnover helps to interpret DBH–H relationships.
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