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1.
  • Björklund, Jesper, 1979, et al. (författare)
  • A definition and standardised terminology for Blue Intensity from Conifers
  • 2024
  • Ingår i: Dendrochronologia. - 1125-7865 .- 1612-0051. ; 85
  • Tidskriftsartikel (refereegranskat)abstract
    • The published literature of the past 20 years expresses inconsistent terminology for the Blue Intensity (BI) method that could lead to confusion in analysis and interpretation. In this technical note we propose a standard terminology based around the prevalent use of BI for the variant that is positively correlated with wood density derived from X-ray and equivalent wood anatomical techniques. We highlight significant practical advantages of this standard terminology for data analysis, scientific interpretations as well as archiving, and provide some cautionary examples that could occur if not adhering to this terminology. In future studies using BI, we recommend to explicitly clarify that the standard terminology is used with the following phrase: The BI data produced in this study is consistent with the ‘2024 BI standard terminology’.
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2.
  • Björklund, Jesper, et al. (författare)
  • Dendroclimatic potential of dendroanatomy in temperature-sensitive Pinus sylvestris
  • 2020
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 60
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2020 The Authors The most frequently and successfully used tree-ring parameters for the study of temperature variations are ring width and maximum latewood density (MXD). MXD is preferred over ring width due to a more prominent association with temperature. In this study we explore the dendroclimate potential of dendroanatomy based on the first truly well replicated dataset. Twenty-nine mature living Pinus sylvestris trees were sampled in North-eastern Finland at the cool and moist boreal forest zone, close to the latitudinal tree line, where ring width, X-ray MXD as well as the blue intensity counterpart MXBI were compared with dendroanatomical parameters. Maximum radial cell wall thickness as well as anatomical MXD and latewood density appeared to be the most promising parameters for temperature reconstruction. In fact, these parameters compare favorably to MXD derived from X-ray techniques as well as MXBI, in terms of shared variation and temperature correlations across frequencies and over time. The reasons for these results are thought to be the unprecedentedly high measurement resolution of the anatomical technique, which provide the optimal resolution – the cell – whereas X-ray techniques have a slightly lower resolution and BI techniques even lower. While the results of this study are encouraging, further tests on longer and multigenerational chronologies are required to more generally and fully assess the dendroclimate potential of anatomical parameters.
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3.
  • Björklund, Jesper, et al. (författare)
  • The utility of bulk wood density for tree-ring research
  • 2021
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 69
  • Tidskriftsartikel (refereegranskat)abstract
    • Bulk wood density measurements are recognized for their utility in ecology, industry, and biomass estimations. In tree-ring research, microdensitometric techniques are widely used, but their ability to determine the correct central tendency has been questioned. Though rarely used, it may be possible to use bulk wood density as a tool to check the accuracy of and even correct microdensitometric measurements. Since measuring bulk wood density in parallel with X-ray densitometry is quickly and easily done, we suspect that its omission is largely due to a lack of awareness of the procedure and/or its importance. In this study, we describe a simple protocol for measuring bulk wood density tailored for tree-ring researchers and demonstrate a few possible applications. To implement real-world examples of the applications, we used a sample of existing X-ray and Blue Intensity (BI) measurements from 127 living and dead Pinus sylvestris trees from northern Sweden to produce new measurements of bulk wood density. We can confirm that the central tendency in this sample material is offset using X-ray densitometry and that the diagnosis and correction of X-ray density is easily done using bulk wood density in linear transfer functions. However, this approach was not suitable for our BI measurements due to heavy discoloration. Nevertheless, we were able to use bulk wood density to diagnose and improve the use of deltaBI (latewood BI – earlywood BI) with regard to its overall trends and multi-centennial variability in a dendroclimatological application. Moreover, we experimented with percent of latewood width, scaled with bulk wood density, as a time- and cost-effective proxy for annual ring density. Although our reconstruction only explains about half of the variation in ring density, it is most likely superior to using fixed literature values of density in allometric equations aimed at biomass estimations. With this study, we hope to raise new awareness regarding the versatility and importance of bulk wood density for dendrochronology by demonstrating its simplicity, relevance, and applicability.
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4.
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5.
  • Büntgen, Ulf, et al. (författare)
  • Prominent role of volcanism in Common Era climate variability and human history
  • 2020
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 64
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2020 Elsevier GmbH Climate reconstructions for the Common Era are compromised by the paucity of annually-resolved and absolutely-dated proxy records prior to medieval times. Where reconstructions are based on combinations of different climate archive types (of varying spatiotemporal resolution, dating uncertainty, record length and predictive skill), it is challenging to estimate past amplitude ranges, disentangle the relative roles of natural and anthropogenic forcing, or probe deeper interrelationships between climate variability and human history. Here, we compile and analyse updated versions of all the existing summer temperature sensitive tree-ring width chronologies from the Northern Hemisphere that span the entire Common Era. We apply a novel ensemble approach to reconstruct extra-tropical summer temperatures from 1 to 2010 CE, and calculate uncertainties at continental to hemispheric scales. Peak warming in the 280s, 990s and 1020s, when volcanic forcing was low, was comparable to modern conditions until 2010 CE. The lowest June–August temperature anomaly in 536 not only marks the beginning of the coldest decade, but also defines the onset of the Late Antique Little Ice Age (LALIA). While prolonged warmth during Roman and medieval times roughly coincides with the tendency towards societal prosperity across much of the North Atlantic/European sector and East Asia, major episodes of volcanically-forced summer cooling often presaged widespread famines, plague outbreaks and political upheavals. Our study reveals a larger amplitude of spatially synchronized summer temperature variation during the first millennium of the Common Era than previously recognised.
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6.
  • Buntgen, U., et al. (författare)
  • Recognising bias in Common Era temperature reconstructions
  • 2022
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 74
  • Tidskriftsartikel (refereegranskat)abstract
    • A steep decline in the quality and quantity of available climate proxy records before medieval times challenges any comparison of reconstructed temperature and hydroclimate trends and extremes between the first and second half of the Common Era. Understanding of the physical causes, ecological responses and societal consequences of past climatic changes, however, demands highly-resolved, spatially-explicit, seasonally-defined and absolutely-dated archives over the entire period in question. Continuous efforts to improve existing proxy records and reconstruction methods and to develop new ones, as well as clear communication of all uncertainties (within and beyond academia) must be central tasks for the paleoclimate community.
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7.
  • Cairns, David M., et al. (författare)
  • Comparing two methods for ageing trees with suppressed, diffuse-porous rings (Betula pubescens ssp. czerepanovii)
  • 2012
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 30:4, s. 252-256
  • Tidskriftsartikel (refereegranskat)abstract
    • The annual growth rings of diffuse porous species such as mountain birch are often difficult to distinguish when samples are collected from trees that grow at treeline or in other harsh environments. In this study we document the differences in seedling and sapling ring counts obtained from two methods of analysis: a traditional analysis based on reflected light and low-power microscopy and one based on transmitted light with higher power magnification that uses thin-sections of the samples. Rings are easier to resolve using the more labor-intensive transmitted light method. Small rings are often missed when using the reflected light method, resulting in an underestimation of tree age. The dates estimated by the standard method agreed with those determined using the thin-sectioning method in 9.6% of the cases. Most commonly, the standard method gave a younger age than did thin-sectioning (72.4% of the trees). In only 18.03% of the cases did the standard method result in a greater age than did thin-sectioning. The reflected light method produced age estimations that were on average 1.37 years younger than those determined using the transmitted light method. The difference between the two methods was positively correlated with age and negatively correlated with mean ring-width. Age-class histograms based on the two methods show little difference at coarser aggregation levels (decades and pentads), but annualized age-class histograms have less agreement between the two methods. Therefore, we suggest using the more labor-intensive thin-sectioning method when annualized age counts are necessary in suppressed seedlings and saplings, for example, comparing tree establishment with annual climate conditions at treeline.
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8.
  • Cerrato, Riccardo, et al. (författare)
  • A Pinus cembra L. tree-ring record for late spring to late summer temperature in the Rhaetian Alps, Italy
  • 2019
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 53, s. 22-31
  • Tidskriftsartikel (refereegranskat)abstract
    • Ongoing climate change strongly affects high-elevation environments in the European Alps, influencing the cryosphere and the biosphere and causing widespread retreat of glaciers and changes in biomes. Nevertheless, high-elevation areas often lack long meteorological series, and global datasets cannot represent local variations well. Thus, proxy data, such as tree rings, provide information on past climatic variations from these remote sites. Although maximum latewood density (MXD) chronologies provide better temperature information than those based on tree-ring width (TRW), MXD series from the European Alps are lacking. To derive high-quality temperature information for the Rhaetian Alps, Pinus cembra L. trees sampled at approximately 2000 m a.s.l. were used to build one MXD chronology spanning from 1647 to 2015. The MXD data were significantly and highly correlated with seasonal May-September mean temperatures. The MXD chronology showed a generally positive trend since the middle of the 19th century, interrupted by short phases of climatic deterioration in the beginning of the 20th century and in the 1970s, conforming with the temperature trends. Our results underline the potential for using Pinus cembra L. MXD to reconstruct mean temperature variations, especially during the onset and latter part of the growing season, providing additional information on parts of the growing season not inferred from TRW. Future studies on MXD for this species will increase the availability of temporal and spatial data, allowing detailed climate reconstructions.
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9.
  • Charpentier Ljungqvist, Fredrik, et al. (författare)
  • Assessing non-linearity in European temperature-sensitive tree-ring data
  • 2020
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 59
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2019 The Authors We test the application of parametric, non-parametric, and semi-parametric calibration models for reconstructing summer (June–August) temperature from a set of tree-ring width and density data on the same dendro samples from 40 sites across Europe. By comparing the performance of the three calibration models on öpairs” of tree-ring width (TRW) and maximum density (MXD) or maximum blue intensity (MXBI), we test whether a non-linear temperature response is more prevalent in TRW or MXD (MXBI) data, and whether it is associated with the temperature sensitivity and/or autocorrelation structure of the dendro parameters. We note that MXD (MXBI) data have a significantly stronger temperature response than TRW data as well as a lower autocorrelation that is more similar to that of the instrumental temperature data, whereas TRW exhibits a öredder” variability continuum. This study shows that the use of non-parametric calibration models is more suitable for TRW data, while parametric calibration is sufficient for both MXD and MXBI data – that is, we show that TRW is by far the more non-linear proxy.
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10.
  • Drobyshev, Igor, et al. (författare)
  • Temporal mortality pattern of pedunculate oaks in southern Sweden
  • 2007
  • Ingår i: Dendrochronologia. - : Elsevier. - 1125-7865 .- 1612-0051. ; :24, s. 97-108
  • Tidskriftsartikel (refereegranskat)abstract
    • Decline of the oak forests decline in southern Sweden has been reported for more than two decades. Little empirical data exists, however, to study the temporal pattern of the phenomenon in detail. In this study we quantified the temporal pattern of non-windfall oak mortality by analyzing the dataset of 44 dendrochronologically dated dead pedunculate oak (Quercus robur L.) trees. We compared tree-ring chronologies from recently dead and living trees from the same sites (number of sites = 13) located in the nemoral and boreo-nemoral zones in southern Sweden. For each dead tree, tree-ring chronologies were analyzed for the presence of pre-death growth depressions. A growth depression was defined as a period ( of one or more years) when growth remained below the 5%, 7%, or 10% quantiles of the ring-width distribution obtained from living trees for a particular year and site. The most recent peak in oak mortality occured around the year 2000. Growth depressions were recorded in 80% (n=35) of all dead oaks and were most prominent during the 1990s. While some oaks showed an obvious reduction in growth over several decades, 51% of the dead trees had growth depression for at least 4 years prior to death. Although diameter growth rate differed between living and recently dead trees for at least 30 years, this difference started to amplify in late 1980s-early 1990s. Presence of pre-death growth depression in tree-ring chronologies implies that (a) non-windfall mortality of oaks is a decade-long process and (b) the actual death event might be lagged behind the timing of the mortality-inducing factors. ANOVA revealed significant differences in tree responses to the drought year 1992. The cumulative growth increment ration between 1992-1994 and 1989-1991, was higher in living trees than in those that had recently died. We suggest that the spring and summer drought of 1992 resulted in the mortality of oaks that was observed in southern Sweden at the end of the 20th centurey. If this time lag exists, it may complicate analyses of decline-related factors and the choise of appropriate actions by forest managers. We conclude that studies of oak decline may benefit from widening the perspective to include several decades preceding the sampling year.
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11.
  • Dukpa, Dorji, et al. (författare)
  • Applied dendroecology informs the sustainable management of Blue Pine forests in Bhutan
  • 2018
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 49, s. 89-93
  • Forskningsöversikt (refereegranskat)abstract
    • Tree ring science is a new discipline in Bhutan but has contributed substantially to our understanding of climate history and informed sustainable forest management practices in the country. This paper describes dendroecological contributions to the second aspect for Blue Pine using three case studies. i) The effects of livestock grazing impact on Blue Pine radial growth were quantified. Radial growth increment was tendentially higher after three years of livestock exclosure, as compared to continued grazing. However, differences remained statistically not significant, likely due to the brevity of the treatment period. ii) Radial growth rates of Blue Pine were characterized across a 400m elevation gradient. Cumulative radial growth over 40 years differed by a factor of more than three between the low and the high end of the gradient. However, below 2300 m, radial growth showed a continuous decline from 1990, likely as a results of drought due to climate change. iii) Effects of three levels of prescribed thinning of pole stage (DBH 30-50 cm) Blue Pine in central Bhutan showed distinct response to thinning. Heavy thinning lead to a thinning shock in the year after harvest and did not lead to significantly higher radial growth as compared to moderate thinning, which is thus recommended for the species. A positive thinning effect remained for seven years post operation. The case studies were incorporated into national guidelines on sustainable forest management in Bhutan and prove the demand for tree ring based research to inform policy and practice.
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12.
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13.
  • Esper, Jan, et al. (författare)
  • Large-scale, millennial-length temperature reconstructions from tree-rings
  • 2018
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 50, s. 81-90
  • Forskningsöversikt (refereegranskat)abstract
    • Over the past two decades, the dendroclimate community has produced various annually resolved, warm season temperature reconstructions for the extratropical Northern Hemisphere. Here we compare these tree-ring based reconstructions back to 831 CE and present a set of basic metrics to provide guidance for non-specialists on their interpretation and use. We specifically draw attention to (i) the imbalance between (numerous) short and (few) long site chronologies incorporated into the hemispheric means, (ii) the beneficial effects of including maximum latewood density chronologies in the recently published reconstructions, (iii) a decrease in reconstruction covariance prior to 1400 CE, and (iv) the varying amplitudes and trends of reconstructed temperatures over the past 1100 years. Whereas the reconstructions agree on several important features, such as warmth during medieval times and cooler temperatures in the 17th and 19th centuries, they still exhibit substantial differences during 13th and 14th centuries. We caution users who might consider combining the reconstructions through simple averaging that all reconstructions share some of the same underlying tree-ring data, and provide four recommendations to guide future efforts to better understand past millennium temperature variability.
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14.
  • Esper, Jan, et al. (författare)
  • Testing the hypothesis of post-volcanic missing rings in temperature sensitive dendrochronological data
  • 2013
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 31:3, s. 216-222
  • Tidskriftsartikel (refereegranskat)abstract
    • The precise, annual dating control, inherent to dendrochronology, has recently been questioned through a combined analysis of tree-growth and coupled climate models (Mann et al. (2012; hereafter MAN12)) suggesting single tree-rings in temperature limited environments are missing following large volcanic events. We test this hypothesis of missing, post-volcanic rings by using a compilation of maximum late-wood density (MXD) records that are typically used for reconstructing temperature and the detection of volcanic events, together with a unique set of long instrumental station data from Europe reaching back into the early 18th century. We investigate the temporal coherence between tree-ring MXD and observed summer temperatures before and after the most significant, precisely dated, volcanic event of the past 1000 years, the 1815 Tambora eruption widely known as the cause for the 1816 year without a summer. Comparison of existing and newly developed MXD chronologies from cold environments in Northern Scandinavia ((r) over bar North = 0.70, N=3) and the European Alps, including the Pyrenees, ((r) over bar central = 0.46, N=4) reveals significant interseries correlations over the 1722-1976 common period, suggesting coherence among these independently developed timeseries. Comparisons of these data with observed JJA temperatures - from 1722 to 1976, a 94-year pre-Tambora (1722-1815), and a 94-year post-Tambora (1817-1910) period - reveals significant and temporally stable correlations ranging from 0.32 to 0.68. However, if we assume the 1816 ring is missing in the MXD chronologies (i.e., shift the pre-Tambora data by one year), all proxy/instrumental correlations fall apart approaching zero. Results from an additional experiment, where the long instrumental record is replaced by an annually resolved, 500-year, summer temperature reconstruction derived from documentary evidence, corroborates the findings from the first experiment: significant positive correlations with the unmolested chronologies and zero correlation with the perturbed chronologies back to 1500 AD. These elementary analyses indicate that either the tree-ring chronologies are correctly dated, i.e., no is ring missing in the year without a summer, or that both the long instrumental and documentary records contain dating uncertainties. As the latter is unlikely, we conclude the MAN12 hypothesis on post-volcanic missing rings can be rejected based on simple comparisons of tree-ring, instrumental and documentary data over the past 300-500 years from Central and Northern Europe.
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15.
  • Frank, Thomas, et al. (författare)
  • Testing different Earlywood/Latewood delimitations for the establishment of Blue Intensity data : A case study based on Alpine Picea abies samples
  • 2020
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 64
  • Tidskriftsartikel (refereegranskat)abstract
    • For dendroclimatological Blue Intensity (BI) studies based on earlywood (EW) or latewood (LW) information, a demarcation between the two is necessary, which can be difficult to establish for species where the transition is subtle. Often, a percental value k is used that calculates an EW/LW boundary value for each tree ring individually based on the difference between maximum and minimum absorption. Several laboratories and authors have used different values for k (e.g. k = 30 % or k = 50 %), while wood anatomical and visual studies suggest that k is on the order of 80 %. Here, we test how different settings of k, and thus different definitions of the EW and LW proportions of a tree ring, influence the dendroclimatic potential of derived time series. To this end, we correlate instrumental temperature measurements with tree ring chronologies that are based on EW and LW information (e.g. EW absorption (EWBI), LW absorption (LWBI)), where the EW/LW proportion is varied by setting different values for k. The tree ring samples utilized are 30 cores of spruce (Picea abies) trees from a high-elevated site (ca. 1700 m a.s.l.) in the northern Alps, Austria. Overall, we achieve high correlations between temperature data and our tree ring chronologies. Regarding the stability of the climate signal under different k values, the results show that absorption intensity based parameters (Delta BI, EWBI, LWBI) are only mildly influenced by different settings of k, while width based parameters (EW width, LW width) show a larger dependence on k. LW width, for instance, was stronger correlated with temperature, the smaller the LW was chosen (and thus the higher k was set). Based on our results and the wood anatomical definition of the EW/LW boundary, we suggest that k = 80 % may be a good choice for future studies. However, since this is only a case study from one site, careful screening of the respective data set regarding an appropriate k value must accompany each dendroclimatological study.
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16.
  • Geijer, Håkan, 1961-, et al. (författare)
  • Dendrochronology with a medical X-ray photon counting computed tomography scanner
  • 2024
  • Ingår i: Dendrochronologia. - : Elsevier. - 1125-7865 .- 1612-0051. ; 86
  • Tidskriftsartikel (refereegranskat)abstract
    • Dendrochronology traditionally involves invasive techniques that might harm cultural heritage artifacts. Noninvasive approaches using X-ray technology and computed tomography (CT) have emerged, but dedicated CT systems are limited in availability. This study explored the viability of using a recently developed photon counting medical CT scanner for growth ring analysis. Six wood samples from pine, oak and beech with varying growth rates were studied. Comparisons were made between traditional methods and CT scanning with measurements performed on the untreated surface, a prepared surface and on CT images. For samples with annual rings wider than 0.3-0.4 mm, CT scanning performed well, while samples with thinner rings or indistinct ring boundaries presented challenges. The combination of traditional tree-ring measurements and analyses of CT scanned images might be a superior study approach generating extra data and information.
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17.
  • Gut, Urs, et al. (författare)
  • No systematic effects of sampling direction on climate-growth relationships in a large-scale, multi-species tree-ring data set
  • 2019
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 57
  • Tidskriftsartikel (refereegranskat)abstract
    • Ring-width series are important for diverse fields of research such as the study of past climate, forest ecology, forest genetics, and the determination of origin (dendro-provenancing) or dating of archaeological objects. Recent research suggests diverging climate-growth relationships in tree-rings due to the cardinal direction of extracting the tree cores (i.e. direction-specific effect). This presents an understudied source of bias that potentially affects many data sets in tree-ring research. In this study, we investigated possible direction-specific growth variability based on an international (10 countries), multi-species (8 species) tree-ring width network encompassing 22 sites. To estimate the effect of direction-specific growth variability on climate-growth relationships, we applied a combination of three methods: An analysis of signal strength differences, a Principal Component Gradient Analysis and a test on the direction-specific differences in correlations between indexed ring-widths series and climate variables. We found no evidence for systematic direction-specific effects on tree radial growth variability in high-pass filtered ring-width series. In addition, direction-specific growth showed only marginal effects on climate-growth correlations. These findings therefore indicate that there is no consistent bias caused by coring direction in data sets used for diverse dendrochronological applications on relatively mesic sites within forests in flat terrain, as were studied here. However, in extremely dry, warm or cold environments, or on steep slopes, and for different life-forms such as shrubs, further research is advisable.
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18.
  • Hartl, Claudia, et al. (författare)
  • Micro-site conditions affect Fennoscandian forest growth
  • 2021
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 65
  • Tidskriftsartikel (refereegranskat)abstract
    • The long tradition of dendroclimatological studies in Fennoscandia is fostered by the exceptional longevity and temperature sensitivity of tree growth, as well as the existence of well-preserved subfossil wood in shallow lakes and extent peat bogs. Although some of the world’s longest ring width and density-based climate reconstructions have been developed in northern Fennoscandia, it is still unclear if differences in micro-site ecology matter, and if so, whether they have been considered sufficiently in previous studies. We developed a Fennoscandia-wide network of 44 Scots pine ring width chronologies from 22 locations between 59°–70 °N and 16°–31 °E, to assess the effects of moist lakeshores and dry inland micro-sites on tree growth. Our network reveals a strong dependency of pine growth on July temperature, which is also reflected in latitude. Differences in forest productivity between moist and dry micro-sites are likely caused by associated effects on soil temperature. While trees at moist micro-sites at western locations exhibit higher growth rates, this pattern is reversed in the continental eastern part of the network, where increased ring widths are found at drier sites. In addition to the latitudinal increase in growth sensitivity to July temperature, pines at moist sites exhibit an increased dependency of summer warmth. The highest temperature sensitivity and growth coherency, and thus greatest suitability for summer temperature reconstructions, is found in those regions where July mean temperatures range between 11.5 and 13.5 °C, and May precipitation totals do not exceed 100 mm. Our study not only provides guidance for the selection of sampling sites for tree ring-based climate reconstructions, but also reveals the effect of micro-site ecology on Fennoscandian forest growth. The manifestation of micro-site effects varies substantially over the Fennoscandian boreal forest and is predominately triggered by the geographical setting of the stand as expressed by differing abiotic site factors.
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19.
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20.
  • Hopf, Sven-Eric, et al. (författare)
  • Dendrochemical indicators of tree rings reveal historical soil acidification in Swiss forest stands
  • 2023
  • Ingår i: Dendrochronologia. - 1125-7865 .- 1612-0051. ; 81
  • Tidskriftsartikel (refereegranskat)abstract
    • The deposition of acidifying nitrogen and sulphur compounds from agriculture and fossil fuel combustion has drastically altered the chemical balance of forest soils in many regions of the world, leading to soil acidification with negative impacts on nutrient availability and thus also on tree vitality. The change of nutrient concentrations in the soil solution can be assessed by long-term investigations, however meaningful indicators, reflecting environmental changes, are needed to compare the current nutrient status with past values. We used dendrochemical indicators in stem wood of different tree species to access the impact of acidifying depositions on soil quality and tree nutrition. We selected 328 stem wood samples from 96 trees of Norway spruce (Picea abies), European beech (Fagus sylvatica), Sessile oak (Quercus petrea) and English oak (Quercus robur) from 22 forest sites, which are part of the long-term Intercantonal Forest Observation Program in Switzerland. Four time periods of 20 years were defined according to the emissions of air pollutants between 1910 and 2017. Our results showed a trend of increasing Al concentrations in tree rings of spruce peaking in the most recent time period (2000–2017). Mn and Ca concentrations in spruce and beech wood have decreased significantly throughout the time period 1910–2017. These dendrochemical indicators depended on the soil pH, with higher Al and lower Mn and Ca concentrations for soils with a low pH (pH<4.2). In oak trees the observed dendrochemical changes are confounded with dendrochemical differences between heartwood and sapwood. K and Mg showed inconsistent patterns in all three tree species, which are probably caused by translocation within the stem discs. With the use of piecewise structural equation models (SEM) we highlighted the direct and indirect influences of N deposition on element concentrations in stem wood. The data suggest a relation between increased N deposition and lower base saturation values in the forest soils for all three tree species, which were linked to higher Al concentrations in spruce and lower Mn concentrations in spruce and beech. The relation between Al concentrations in tree rings of Norway spruce and measured base saturation was used to reconstruct past soil base saturation values. It revealed a progressive soil acidification in the long-term forest observation sites. These reconstructed base saturation values were further used to validate modelled values from dynamic biogeochemical models such as SAFE/ForSAFE. This comparison pointed out possible shortcomings such as the lack of organic complexation in those models. Taken together, our analyses showed that element concentrations of Al, Mn, Ca in Norway spruce and European beech stem wood were suitable dendrochemical indicators of environmental change due to soil acidification, as they reflect both direct and indirect effects of air pollutants and chemical soil properties.
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21.
  • Kirdyanov, Alexander, et al. (författare)
  • Notes towards an optimal sampling strategy in dendroclimatology
  • 2018
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 52, s. 162-166
  • Tidskriftsartikel (refereegranskat)abstract
    • Though the extraction of increment cores is common practice in tree-ring research, there is no standard for the number of samples per tree, or trees per site needed to accurately describe the common growth pattern of a discrete population of trees over space and time. Tree-ring chronologies composed of living, subfossil and archaeological material often combine an uneven distribution of increment cores and disc samples. The effects of taking one or two cores per tree, or even the inclusion of multiple radii measurements from entire discs, on chronology development and quality remain unreported. Here, we present four new larch (Larix cajanderi Mayr) ring width chronologies from the same 20 trees in northeastern Siberia that have been independently developed using different combinations of core and disc samples. Our experiment reveals: i) sawing is much faster than coring, with the latter not always hitting the pith; ii) the disc-based chronology contains fewer locally absent rings, extends further back in time and exhibits more growth coherency; iii) although the sampling design has little impact on the overall chronology behaviour, lower frequency information is more robustly obtained from the disc measurements that also tend to reflect a slightly stronger temperature signal. In quantifying the influence of sampling strategy on the quality of tree-ring width chronologies, and their suitability for climate reconstructions, this study provides useful insights for optimizing fieldwork campaigns, as well as for developing composite chronologies from different wood sources.
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22.
  • Linderholm, Hans W., et al. (författare)
  • Comparing Scots pine tree-ring proxies and detrending methods among sites in Jamtland, west-central Scandinavia
  • 2010
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 28:4, s. 239-249
  • Tidskriftsartikel (refereegranskat)abstract
    • Scots pine tree-ring width (TRW) data from Jamtland in the Central Scandinavian Mountains has been used to reconstruct summer temperatures back to 1630 BC. However, it was recently shown that this reconstruction was of limited spatial importance. In this paper, we aim to explain this limitation in the TRW data as a temperature proxy, as well as assess the temperature information from new maximum latewood density (MXD) data. Furthermore, the effect of two standardization methods is evaluated: regional curve standardization (RCS) and a more traditional standardization, termed "non-RCS" standardization. Three TRW and two MXD sites were analyzed. Our results showed that despite the proximity to the Norwegian Sea, the MXD data is a powerful temperature proxy. Difference among sites in TRW data, especially on decadal timescales, together with a lower temperature association, suggests that other factors, such as changes in the local climate regimes, weakens the temperature signal. In general the RCS method overestimates pine growth trends in the latter half of the twentieth century, a feature not seen when using "non-RCS" standardization. This is likely due to an age-bias of older trees in most recent parts of the tree-ring chronologies. This effect will have consequences when reconstructing climate with tree-ring data. To overcome this problem, all age-classes should be represented throughout a chronology. If this is not possible, the use of "non-RCS" standardization is recommended, although this method results in a loss of low-frequency variability. (C) 2010 Istituto ltaliano di Dendrocronologia.
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23.
  • Linderholm, Hans W., 1968, et al. (författare)
  • Were medieval warm-season temperatures in Jamtland, central Scandinavian Mountains, lower than previously estimated?
  • 2019
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 57:October
  • Tidskriftsartikel (refereegranskat)abstract
    • Today few high-quality tree-ring based temperature reconstructions extending over the past millennium exist, and those have, in general, low replication in their early parts. Here we present a new and updated maximum latewood density (MXD) chronology extending over the last 1200 years, built from local Scots pine wood sources (living trees, drywood preserved the ground, and subfossil wood extracted from lakes) all collected within 20 km in the Scandinavian Mountains in Jamtland. The MXD data was used to reconstruct April-September mean temperatures, where 60% of the variance in observed temperatures could be explained. The reconstruction exhibited distinct multidecadal variability, with the coldest periods centred on ca. 900, 1450, 1600 and 1900 CE, and the warmest periods on ca. 1160, 1250, 1500, 1660 CE. The last part of the 20th - early part of 21st century was the warmest period throughout the whole record, and the reconstruction suggests that, on average, the Medieval Climate Anomaly (MCA, 950-1250 CE) was only slightly warmer than the Little Ice Age (LIA, 1450-1900 CE). In fact, compared to earlier reconstructions from the region, the new reconstruction suggested lower MCA warm-season temperatures. However, despite sufficient replication during that period, high inhomogeneity among the MXD series makes this period slightly uncertain. The unique drywood on which the chronology was built, displayed a distinct regeneration pattern, where changes in Scots pine establishment was interpreted as responses to changes in forest fire activity and climate throughout the past millennium.
  •  
24.
  • Netsvetov, Maksym, et al. (författare)
  • The climate to growth relationships of pedunculate oak in steppe
  • 2017
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1612-0051 .- 1125-7865. ; 44, s. 31-38
  • Tidskriftsartikel (refereegranskat)abstract
    • Pedunculate oak (Quercus robur L.) is a long-lived species that dominates the extra–zonal natural forests in the steppe landscape of southeastern Ukraine. Although Q. robur is considered to be one of the most important species in European dendrochronology, it has received little attention in the steppe zone because of its scarcity in the often-degraded steppe forests. Nevertheless, a small and unique patch of old-growth oak exists within the boundary of Donetsk, a large industrial center in Eastern Europe. This forest is a remnant of an ancient wood and includes several dozen old-age trees that can contribute to filling some of the spatial gaps in pedunculate oak dendrochronology in Eastern Europe. In this study, we aim to determine the effect of climatic variables on pedunculate oak growth in the steppe zone, and to estimate the longevity of this species in the heterogeneous conditions of an urban forest. A total of 20 trees were cored for this study, varying in age from 55 to 254. The resulting tree-ring chronology correlates strongly with local precipitation in spring and summer, and with local temperature in April, June and July. Moving correlation analysis indicates a shift over the last 80 years in the relationship between oak growth and late winter and early spring temperatures, as well as between oak growth and precipitation in February and August. These findings imply that warming has caused both an advance in oak phenology and changes in the climatic conditions in early spring.
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25.
  • Pritzkow, C., et al. (författare)
  • Relationship between wood anatomy, tree-ring widths and wood density of Pinus sylvestris L. and climate at high latitudes in northern Sweden
  • 2014
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 32:4, s. 295-302
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, wood anatomy, tree-ring width and wood density of Pinus sylvestris at the northern timberline in Fennoscandia were used to identify relationships among the parameters and to screen them for their climatic signals. Furthermore we investigated the influence of the juvenile wood section for all parameters developed. The measurements of wood anatomy were conducted with confocal laser scanning microscopy (CLSM) while the density profiles were produced using an Itrax MultiScanner. We developed chronologies of ring width, wood density and anatomy for a period between 1940 and 2010. Correlations between wood density and wood anatomy were strong in the latewood part. For some wood anatomy and density chronologies youth trends were found in the juvenile part. Wood density decreased from the pith up to the 9th ring and stabilized afterwards, while cell lumen diameter and lumen area increased simultaneously up to the 15th ring. All chronologies contained strong summer temperature signals. The wood anatomical variables provided additional information about seasonal precipitation which could not be found in wood density and tree-ring widths. Our study confirmed previous results stating that the parameter maximum density contains the strongest climate signal, that is, summer temperatures at the northern timberline. Nevertheless, the intra-annual data on tracheid dimensions showed good potential to supply seasonal climatic information and improve our understanding of climatic effects on tree growth and wood formation.
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26.
  • Rao, Mukund P., et al. (författare)
  • A double bootstrap approach to Superposed Epoch Analysis to evaluate response uncertainty
  • 2019
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 55, s. 119-124
  • Tidskriftsartikel (refereegranskat)abstract
    • The association between climate variability and episodic events, such as the antecedent moisture conditions prior to wildfire or the cooling following volcanic eruptions, is commonly assessed using Superposed Epoch Analysis (SEA). In SEA the epochal response is typically calculated as the average climate conditions prior to and following all event years or their deviation from climatology. However, the magnitude and significance of the inferred climate association may be sensitive to the selection or omission of individual key years, potentially resulting in a biased assessment of the relationship between these events and climate. Here we describe and test a modified double-bootstrap SEA that generates multiple unique draws of the key years and evaluates the sign, magnitude, and significance of event-climate relationships within a probabilistic framework. This multiple re-sampling helps quantify multiple uncertainties inherent in conventional applications of SEA within dendrochronology and paleoclimatology. We demonstrate our modified SEA by evaluating the volcanic cooling signal in a Northern Hemisphere tree-ring temperature reconstruction and the link between drought and wildfire events in the western United States. Finally, we make our Matlab and R code available to be adapted for future SEA applications.
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27.
  • Rocha, Eva, et al. (författare)
  • A Norway spruce tree-ring width chronology for the Common Era from the Central Scandinavian Mountains
  • 2021
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 70
  • Tidskriftsartikel (refereegranskat)abstract
    • Fennoscandia is one of the most prominent regions in the world for dendroclimatological research. Yet, millennium-long tree-ring chronologies in this region have mainly been developed from Scots pine (Pinus sylvestris L.). To explore the possibility of building long-term chronologies using other dominating tree species in the region, this paper presents the first two millennia-long Norway spruce (Picea abies (L.) Karst.) ring-width chronology from Northern Europe. The chronology is composed of living trees and subfossil wood and covers the period from BCE 115 to 2012 CE. A sufficiently replicated and robust chronology is built for the past 360 years back to 1649 CE. Further back in time, the common growth signal is reduced, and hence the reliability of the earlier section of the chronology is lower. The climate calibration results show that the spruce ring-width correlation with June-July mean temperatures over the period 1901-2012 is positive and significant (r = 0.6, p < 0.01) and representing the temperature variability of a spatial domain covering west-central Scandinavia. These results show the ability of Norway spruce to serve as a proxy for paleoclimatic research and the possibility of extending the chronology far back in time in the region, and therefore present an opportunity for carrying out new inter-and intraregional proxy analyses.
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28.
  • Rydval, Milos, et al. (författare)
  • Blue intensity for dendroclimatology : Should we have the blues? Experiments from Scotland
  • 2014
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 32:3, s. 191-204
  • Tidskriftsartikel (refereegranskat)abstract
    • Blue intensity (BI) has the potential to provide information on past summer temperatures of a similar quality to maximum latewood density (MXD), but at a substantially reduced cost. This paper provides a methodological guide to the generation of BI data using a new and affordable BI measurement system; CooRecorder. Focussing on four sites in the Scottish Highlands from a wider network of 42 sites developed for the Scottish Pine Project, BI and MXD data from Scots pine (Pious sylvestris L.) were used to facilitate a direct comparison between these parameters. A series of experiments aimed at identifying and addressing the limitations of BI suggest that while some potential limitations exist, these can be minimised by adhering to appropriate BI generation protocols. The comparison of BI data produced using different resin-extraction methods (acetone vs. ethanol) and measurement systems (CooRecorder vs. WinDendro) indicates that comparable results can be achieved. Using samples from the same trees, a comparison of both BI and MXD with instrumental climate data revealed that overall, BI performs as well as, if not better than, MXD in reconstructing past summer temperatures (BI r(2) = 0.38-0.46; MXD r(2) = 0.34-0.35). Although reconstructions developed using BI and MXD data appeared equally robust, BI chronologies were more sensitive to the choice of detrending method due to differences in the relative trends of non-detrended raw BI and MXD data. This observation suggests that the heartwood-sapwood colour difference is not entirely removed using either acetone or ethanol chemical treatment, which may ultimately pose a potential limitation for extracting centennial and longer timescale information when using BI data from tree species that exhibit a distinct heartwood-sapwood colour difference. Additional research is required in order to develop new methods to overcome this potential limitation. However, the ease with which BI data can be produced should help justify and recognise the role of this parameter as a potential alternative to MXD, particularly when MXD generation may be impractical or unfeasible for financial or other reasons.
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29.
  • Stridbeck, Petter, et al. (författare)
  • Partly decoupled tree-ring width and leaf phenology response to 20th century temperature change in Sweden
  • 2022
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 75
  • Tidskriftsartikel (refereegranskat)abstract
    • The recent warming trend, and associated shifts in growing season length, challenge the principle of uniformitarianism, i.e., that current relations are persistent over time, and complicates the uncritical inferences of past climate from tree-ring data. Here we conduct a comparison between tree-ring width chronologies of Pinus sylvestris L. (Scots pine), Picea abies (L.) Karst. (Norway spruce) and Betula pubescens Ehrh. (Downy birch) and phenological observations (budburst and leaf senescence) of Fagus sylvatica L. (European beech), Quercus robur L. (European oak), Betula sp. (Birch), Norway spruce and Scots pine) in Sweden to assess to what extent the tree-ring width–temperature relationship and the timing of phenological phases are affected by increased temperature. Daily meteorological observations confirm a prolongation of the thermal growing season, most consistently observed as an earlier onset of around 1–2 weeks since the beginning of the 20th century. Observations of budburst closely mimic this pattern, with budburst of the deciduous trees occurring 1–2.5 weeks earlier. In contrast to the changes seen in phenology and observational temperature data, the tree-ring width–temperature relationships remain surprisingly stable throughout the 20th century. Norway spruce, Scots pine and Downy birch all show consistently significant correlations with at least one 30 day-long window of temperature starting in late June–early July season. Norway spruce displays the largest degree of stability, with a consistent 60 day-long temperature window with significant correlation starting around Julian calendar day 150. Thus, our results suggest that the principle of uniformitarianism is not violated during the period covered by modern meteorological observations. Further research is needed to determine at what thresholds the temperature sensitivity of these species may alter or deteriorate as a consequence of the ongoing climate change.
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30.
  • Thomas, Wieloch, et al. (författare)
  • A novel device for batch-wise isolation of a-cellulose from small-amount wholewood samples
  • 2011
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 29:2, s. 115-117
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel device for the chemical isolation of α-cellulose from wholewood material of tree rings was designed by the Potsdam Dendro Laboratory. It allows the simultaneous treatment of up to several hundred micro samples. Key features are the batch-wise exchange of the chemical solutions, the reusability of all major parts and the easy and unambiguous labelling of each individual sample. Compared to classical methods labour intensity and running costs are significantly reduced.
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31.
  • Van den Bulcke, Jan, et al. (författare)
  • 3D tree-ring analysis using helical X-ray tomography
  • 2014
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 32:1, s. 39-46
  • Tidskriftsartikel (refereegranskat)abstract
    • The current state-of-the-art of tree-ring analysis and densitometry is still mainly limited to two dimensions and mostly requires proper treatment of the surface of the samples. In this paper we elaborate on the potential of helical X-ray computed tomography for 3D tree-ring analysis. Microdensitometrical profiles are obtained by processing of the reconstructed volumes. Correction of the structure direction, taking into account the angle of growth rings and grain, results in very accurate microdensity and precise ring width measurements. Both a manual as well as an automated methodology is proposed here, of which the MATLAB (c) code is available. Examples are given for pine (Pinus sylvestris L), oak (Quercus robur L) and teak (Tectona grandis L.). In all, the methodologies applied here on the 3D volumes are useful for growth related studies, enabling a fast and non-destructive analysis.
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32.
  • Baudet, Marlène, et al. (författare)
  • New insights into estimating the age of old Scots pine from increment cores with stem rot
  • 2020
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 64
  • Tidskriftsartikel (refereegranskat)abstract
    • Trunk inner rot is a common phenomenon in some old-growth pine dominated forests, making it impossible to determine tree age by counting annual rings. We compared the efficiency of five methods to estimate the age of hollow pine trees (Pinus sylvestris L.). Our main aims were to select the best-performing method and to test whether the age of the tree or the proportion of rot influences the accuracy of estimation. We used full increment cores (reaching the pith or within 1 cm of it) from 100 trees (54-562 years old) collected in northern Sweden and simulated rotten centres of three different sizes in order to test the methods. The lowest error rates were obtained when less than a third of the sample was missing (down to 5.0 % error rate), and by using a method based on the growth pattern of a set of healthy trees. Using linear extrapolation of the mean radial growth led to large overestimates (up to three times the number of absent rings) with error rates up to 27.3 %. We also found that the performance of all methods was reduced in cores from older trees. Our main conclusion is that non-linear methods should be preferred for age estimation of hollow pines. We also argue that more precision in the age estimation could be gained already in the field by collecting multiple cores from rotten trees or by developing alternative coring methods.
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33.
  • Cao, X., et al. (författare)
  • Microdensitometric records from humid subtropical China show distinct climate signals in earlywood and latewood
  • 2020
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 64
  • Tidskriftsartikel (refereegranskat)abstract
    • Blue intensity (BI) from tree rings is a technique that has been widely explored for temperature reconstruction purposes in middle and high latitudes. However, it is still rather untested at lower latitudes and in drier climates, particularly in subtropical areas. Here, we develop the first series of BI-based tree-ring parameters (earlywood BI, EWBI; latewood BI, LWBI and ΔBI, the difference between LWBI and EWBI) in humid subtropical China from the species Pinus massiniana. Although the BI parameters have weaker inter-series correlations than do ring widths, they are generally better correlated with climate parameters. Our study shows a positive temperature response in the EWBI parameter and negative responses in the LWBI and ΔBI parameters. Interestingly, the correlation pattern is almost the opposite of that observed at high latitudes, where there is a pronounced positive sensitivity of the LWBI/ΔBI/MXBI parameters to temperature. We find the EWBI to be the most robust parameter for reconstruction purposes. The positive March–May average temperature signal of EWBI is stable across frequencies and shows consistent interdecadal variations with other temperature proxy series from the region. The compilation of new tree-ring records using the BI technique will ultimately support our understanding of climate history. For this reason, we encourage similar attempts to push the boundaries of the BI technique even further. © 2020 Elsevier GmbH
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34.
  • Drobyshev, Igor (författare)
  • Detecting changes in climate forcing on the fire regime of a North American mixed-pine forest: A case study of Seney National Wildlife Refuge, Upper Michigan
  • 2012
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 30, s. 137-145
  • Tidskriftsartikel (refereegranskat)abstract
    • The study of forests dominated by red pine (Pinus resinosa Alt.), one of the few fire-resistant tree species of eastern North America, provides an opportunity to reconstruct long-term fire histories and examine the temporal dynamics of climate forcing upon forest fire regimes. We used a 300-year long spatially explicit dendrochronological reconstruction of the fire regime for Seney National Wildlife Refuge (SNWR, 38,531 ha), eastern Upper Michigan to: (1) identify fire size thresholds with strong vs. weak climate controls, (2) evaluate effect of landform type (outwash channel vs. sand ridges) in modifying climate-fire associations, and (3) check for the presence of temporal changes in the climate control of large fire events over the time period 1700-1983. We used a summer drought sensitive red pine chronology (ITRDB code can037) as a proxy of past fire-related climate variability. Results indicated that fires >60 ha in sand-ridge-dominated portions of SNWR and >100 ha in outwash channels were likely climatically driven events. Climate-fire associations varied over time with significant climate-fire linkages observed for the periods 1700-1800 (pre-EuroAmerican), 1800-1900 (EuroAmerican settlement) and 1900-1983 (modern era). Although an increase in fire activity at the turn of 20th century is commonly associated with human sources of ignitions, our results suggest that such an increase was also likely a climatically driven episode. (C) 2012 Istituto Italiano di Dendrocronologia. Published by Elsevier GmbH. All rights reserved.
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35.
  • Drobyshev, Igor (författare)
  • Disturbance and regeneration dynamics of a mixed Korean pine dominated forest on Changbai Mountain, North-Eastern China
  • 2014
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 32, s. 21-31
  • Tidskriftsartikel (refereegranskat)abstract
    • We used dendrochronological methods to study disturbance history of a mixed Korean pine (Pious koraiensis Siebold et Zuccarini) dominated forest on the northern slope of Changbai Mountain, North Eastern China, over 1770-2000. Frequent small-scale canopy gaps and infrequent medium-scale canopy disturbances dominated natural disturbance regime in the forest, which did not experience stand-replacing disturbances over the studied period. Percentages of growth releases in subcanopy trees were below 6% in most decades, suggesting that disturbances initiating these releases were of low intensity. Strong winds were likely cause of moderate disturbance events. Two episodes with increased disturbance rates (19% and 13%) were dated to the 1920s and 1980s, timing of the 1980s event was consistent with a hurricane occurred in 1986 on the western slope of the Changbai Mountain. Age structure and growth release analyses revealed species-specific regeneration strategies of canopy dominants. Shade-intolerant Olga bay larch (Larix olgensis Henry) recruited mainly before the 1860s. Recruitment of moderately shade-tolerant P. koraiensis occurred as several regeneration waves (1820s, 1850s, 1870-1880s, 1930s, and 1990-2000s) of moderate intensity. Shade-tolerant Jezo spruce (Picea jezoensis Carr. var. komarovii (V. Vassil.) Cheng et L.K.Fu) and Manchurian fir (Abies nephrolepis (Trautv.) Maxim.) regenerated continuously over the last 220 and 130 years, respectively. Enhanced recruitment of P. koraiensis, P. jezoensis, and A. nephrolepis was observed during the 1930s and 1990s, coinciding with increased growth release frequency in the 1920s and 1980s, and suggesting disturbance events of moderate intensity. Our results indicate that the current disturbance regime of the mixed Korean pine dominated forest maintains coexistence of lightdemanding and shade-tolerant species and that change in wind climate may be particularly important for future forest composition. (C) 2013 Elsevier GmbH. All rights reserved.
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36.
  • Drobyshev, Igor (författare)
  • Growth-climate response of Jack pine on clay soils in northeastern Canada
  • 2012
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 30, s. 127-136
  • Tidskriftsartikel (refereegranskat)abstract
    • We used tree-ring data from a major North American boreal tree species. Jack pine (Pinus banksiana Lamb.), to decipher spatial and temporal tree-growth responses to climate variability within the area of northwestern Quebec and northeastern Ontario. Fifteen sites with clay soils were selected and grouped into North and South sub-regions at approximately 49 degrees N and 50 degrees N, respectively. Tree-ring chronologies were analyzed through a response function for the years 1951-2000 to identify growth-limiting climate factors. Increased precipitation in June in the previous year and a warm month of April this year favored radial growth whereas higher temperature in September and increased precipitation in October, both of the previous year, and current June precipitation were negatively related to growth. There was a clear difference in climatic response between the southern and northern sub-regions: southern sites were more responsive to temperature dynamics while on northern sites Jack pine growth appeared negatively influenced by an excess of precipitation. Soil conditions, with larger areas covered by less water permeable clay deposits in the northern sub-region, explain this result. If recently observed trends towards warmer springs continue. Jack pine may increase its radial growth in the study area. However, increases in fall precipitation, also predicted under the future climate, may offset the positive effect of previous years weather on clay sites. (C) 2012 Istituto Italian di Dendrocronologia. Published by Elsevier GmbH. All rights reserved.
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37.
  • Drobyshev, Igor (författare)
  • Spatiotemporal variation in the relationship between boreal forest productivity proxies and climate data
  • 2019
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 58
  • Tidskriftsartikel (refereegranskat)abstract
    • The impacts of climate change on high-latitude forest ecosystems are still uncertain. Divergent forest productivity trends have recently been reported both at the local and regional level challenging the projections of boreal tree growth dynamics. The present study investigated (i) the responses of different forest productivity proxies to monthly climate (temperature and precipitation) through space and time; and (ii) the local coherency between these proxies through time at four high-latitude boreal Scots pine sites (coastal and inland) in Norway. Forest productivity proxies consisted of two proxies representing stem growth dynamics (radial and height growth) and one proxy representing canopy dynamics (cumulative May-to-September Normalized Difference Vegetation Index (NDVI)). Between-proxy and climate-proxy correlations were computed over the 1982-2011 period and over two 15-yr sub-periods. Over the entire period, radial growth significantly correlated with current year July temperature, and height growth and cumulative NDVI significantly correlated with previous and current growing season temperatures. Significant climate responses were quite similar across sites, despite some higher sensitivity to non-growing season climate at inland sites. Significant climate-proxy correlations identified over the entire period were temporarily unstable. Local coherency between proxies was generally insignificant. The spatiotemporal instability in climate-proxy correlations observed for all proxies underlines evolving responses to climate and challenges the modelling of forest productivity. The general lack of local coherency between proxies at our four study sites suggests that forest productivity estimations based on a single proxy should be considered with great caution. The combined use of different forest growth metrics may help circumvent uncertainties in capturing responses of forest productivity to climate variability and improve estimations of carbon sequestration by forest ecosystems.
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38.
  • Edvardsson, Johannes, et al. (författare)
  • A statistical model for the prediction of the number of sapwood rings in Scots pine (Pinus sylvestris L.)
  • 2022
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 74
  • Tidskriftsartikel (refereegranskat)abstract
    • Dendrochronology is a well-established dating method for wooden objects, but due to surface processing of construction timber or natural degradation the dating of historical wood often relies on a prediction of the number of missing rings based on sapwood statistics. Since Scots pine (Pinus sylvestris L.) is one of the most common tree species in north-western Europe, the absence of reliable sapwood statistics and models for the prediction of missing sapwood rings for pine samples is remarkable. We have therefore produced sapwood statistics based on data from 776 pine trees with ages from 15 to 345 years. The material consists of both living trees and historical timber, with varying growth rates, geographic settings, and from different soil types. When the whole material is considered, the average age of the trees is 103 years, and the number of sapwood rings is 54 ± 15 (1 SD), but range from 18 to 129. Trees less than 100-years in age contained 46 ± 11 (1 SD) sapwood rings and had an average tree-ring width (TRW) of 1.76 mm. With increasing age, the average TRW decreased while the number of sapwood rings increased. The average TRW of 101–200-year-old trees is 0.99 mm while the samples contained 63 ± 12 (1 SD) sapwood rings. For trees older than 201 years, the average TRW is 0.64 mm while the number of sapwood rings increased to 85 ± 16 (1 SD). The two most important factors in determining the number of sapwood rings for a given tree when only heartwood statistics are available proved to be (i) the number of heartwood rings and (ii) the average TRW of the heartwood rings. For incomplete samples, we have therefore developed a statistical model based on the sample's heartwood rings (number and average width) to compute a prediction interval for the total number of rings. The sapwood and heartwood statistics suggest a statistical model for the number of sapwood rings with mean that increase with the number of heartwood rings. Furthermore, the average number of sapwood rings decreases with the mean width of the heartwood rings. However, the predictive power of the mean width is limited when the number of heartwood rings has already been taken into account. Thus, we suggest making predictions for the number of sapwood rings using only the number of heartwood rings. Predictions of the number of sapwood rings based on the statistical model where convincing in the case of the three different datasets that were analysed. The certainty in these predictions was such that the width of the 80% and 95% prediction intervals ranged 28–34 and 45–52 sapwood rings, respectively. Additionally, we demonstrate how make predictions when there is information about the number of remaining sapwood rings in a given sample. To make the sapwood model available, we present a free online R package for fitting our models and an online software dashboard.
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39.
  • Edvardsson, Johannes, et al. (författare)
  • Exploring climate forcing of growth depression in subfossil South Swedish bog pines using stable isotopes
  • 2014
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 32:1, s. 55-61
  • Tidskriftsartikel (refereegranskat)abstract
    • Comparison between growth variability, based on ring-width (RW) analysis, and moisture-sensitive signals in tree-ring carbon and oxygen stable-isotope composition provides increased understanding of how climate and hydrology influenced bog pines (Pinus sylvestris L) at two sites in southern Sweden during the mid- and late Holocene. Tree-ring sequences from two subfossil trees collected at raised bogs having different hydrology and catchment size were analyzed to probe the stable-isotope signals associated with two bog-wide episodes of growth depression, one during the Holocene Thermal Maximum and the other during the Neoglacial Transition. The occurrence of lower whole-wood delta C-13 and cellulose 813C and 8180 values immediately prior to the onset of growth depression in both trees, suggesting increased atmospheric relative humidity, is consistent with the notion that excessive effective moisture impeded tree growth. Correlation analysis indicates that the growth response lagged about three years behind the decline in delta C-13 and delta O-18 values in each tree, possibly reflecting relatively slow rise in the local water table in response to wetter climate. (c) 2013 Elsevier GmbH. All rights reserved.
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40.
  • Edvardsson, Johannes, et al. (författare)
  • South Swedish bog pines as indicators of Mid-Holocene climate variability
  • 2012
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 30:2, s. 93-103
  • Tidskriftsartikel (refereegranskat)abstract
    • Dendroclimatic investigations of subfossil Scots pine (Pinus sylvestris) from two raised bogs in southern Sweden yielded a continuous floating 1492-year long tree-ring record. By cross-dating with bog-pine chronologies from Lower Saxony, Germany, the South Swedish record was assigned an absolute age of 5219-3728 BC. The cross-match between ring-width chronologies from these two regions, separated by 500-700 km, is remarkably strong and the correlation positive, which indicates that large-scale climate dynamics had a significant impact on the growth of bog pines during the Holocene Thermal Maximum (HTM) when bog-pine distribution reached a maximum in both regions. However, local population dynamics were also influenced by peatland ontogeny and competition, as shown by differences in replication and mean tree age between the Swedish and German records. Comparisons with chronologies developed from modern bog pines in southern Sweden indicate that more coherent climate was controlling pine growth on natural peatlands during warm periods in the past. This study demonstrates the usefulness of Swedish subfossil bog-pine material as a climate proxy, with particular potential for decadal- to centennial-scale reconstructions of humidity fluctuations. (C) 2011 Istituto Italiano di Dendrocronologia. Published by Elsevier GmbH. All rights reserved.
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41.
  • Fang, K., et al. (författare)
  • Wind speed reconstruction from a tree-ring difference index in northeastern Inner Mongolia
  • 2022
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 72
  • Tidskriftsartikel (refereegranskat)abstract
    • The lack of instrumental wind speed data beyond the industrial era limits our ability to evaluate the contributions of natural versus anthropogenic processes on long-term changes in wind speed. It is thus desirable to find proxies for historical changes in wind speed. Persistent and strong winds can cause compression wood composed of wider and denser rings in conifer trees at leeward sides. This work hypothesizes that the asymmetric wind impact on tree radial growth provides information about wind speed changes. To test the hypothesis, we developed a Tree-Ring Difference Index (TRDI) representing the differences between tree ring widths at the windward and leeward sides. Thirty-four trees subjected to strong and persistent winds in a Picea mongolica forest in northeastern Inner Mongolia were analyzed. The TRDI based on 124 cores correlates significantly with the maximum wind speeds recorded from May to August, indicating that this proxy can be used for wind speed reconstruction. Our reconstruction reveals long-term changes in wind speed including an upward trend from 1940 to 1954, followed by continually decreasing wind speeds from 1955 to 1990 and increasing values from 1991 to 2010. The reconstructed wind speeds include strong multi-decadal variability and significant correlations with the Pacific Decadal Oscillation (PDO). © 2022 Elsevier GmbH
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42.
  • Francon, L., et al. (författare)
  • The timing of wood formation in peatland trees as obtained with different approaches
  • 2024
  • Ingår i: Dendrochronologia. - 1125-7865. ; 85
  • Tidskriftsartikel (refereegranskat)abstract
    • Dendrometers offer valuable insights into how tree growth responds to climatic variables and physiological processes over the course of a year. Yet, their applicability to extremely slow-growing trees, such as those in peatlands, has been limited due to the intricate and slow nature of growth, therefore rendering interpretation of results complex. In this study, we conducted a comprehensive monitoring of tree wood formation in both peatland and mineral soil ecosystems in southern Sweden (58.37 N, 12.17 E, 75 m asl) in 2021 and 2022, using both band and point dendrometers. To verify and validate the dendrometer data, we also sampled microcores every two weeks during both growing seasons. We find that peatland trees grow at approximately 30 % the rate of their neighbors on mineral soils. The onset of growth among peatland trees typically occurs between mid-May and early June, consistently lagging the start of the growing season in trees on mineral soils by one to three weeks. Notably, growth peaks are synchronized across peatland trees and coincide with the summer solstice. Both types of dendrometers exhibit varying degrees of accuracy depending on the phenological stages measured. They perform well in identifying growth onset and peak but are less effective at detecting growth cessation. Point dendrometers demonstrate superior accuracy as they better capture daily irreversible growth increments. In the case of band dendrometers, growth increments are obscured by greater reversible fluctuations in dead bark tissues. However, they remain valuable for tracking the wood phenology of trees with growth rates exceeding 2 mm/year. Based on our results, for an effective tree monitoring in peatlands, we strongly recommend (1) using point dendrometers and (2) removing the dead bark tissues on monitored trees.
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43.
  • Gundale, Kelley (författare)
  • European Dendroecological Fieldweek (EDF) 2021 in Val Mustair, Switzerland: International education and research during the pandemic
  • 2023
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 78
  • Tidskriftsartikel (refereegranskat)abstract
    • The European Dendroecological Fieldweek (EDF) is a one-week course that takes place every year at varying locations in Europe according to the principle "Bring tree-ring research to the people". The EDF welcomes early -career to advanced researchers, but also forest service and other federal agency employees and private people interested in tree-ring sciences from all over the world. It encompasses a large spectrum of dendrochronological field, laboratory and data analysis methods and scientific fields including climatology, ecology, physiology, geomorphology and archaeology. Multiple scales of observations from the individual cell to the ecosystem level and from seasonal to multi-centennial periods are covered. Work on mini research projects in topic groups al-ternates with keynote lectures and individual participants' presentations.As one of the first in-person tree-ring meetings since the start of the COVID-19 pandemic the 31st EDF was held in summer 2021 in Val Mustair, Switzerland. Topics included i) Tree age and climate sensitivity of a relict, old -growth Scots pine stand, ii) Blue intensity-based climate sensitivity of Norway spruce growth, iii) Tree rings as indicators of grey larch budmoth outbreaks, iv) Growth of larch trees along an abandoned irrigation channel, v) Wood anatomical characteristics of two alpine creeping shrub species, and vi) Historical dating of a stable and a residential house. Alongside with their educational value these projects allowed novel insight into the age structure and growth dynamics of the sub-alpine forests and beyond in the valley and provided valuable outcome to the local stakeholders such as the Nature Park Biosfera Val Mustair, the local forest service and the public of Val Mustair.Under hindered conditions due to the pandemic, the 31st EDF still demonstrated its strength as an international educational and interdisciplinary scientific field and lab course, combining teaching with the application of cutting-edge technologies.
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44.
  • Hallinger, Martin (författare)
  • Does sex matter? Gender-specificity and its influence on site-chronologies in the common dioecious shrub Juniperus communis
  • 2018
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 49, s. 118-126
  • Tidskriftsartikel (refereegranskat)abstract
    • In recent years an increasing number of studies have shown shrubs to be reliable proxies of environmental conditions in regions where Trees - due to harsh climate conditions - are absent. Although many shrubs are monoecious, some are dioecious, which poses certain questions related to gender-specific growth as observed for trees in previous studies. Here, we address the questions whether dioecious shrubs, similar to trees, show growth differences between male and female plants, and - if so - whether this difference needs to be considered in terms of sample selection. We chose Juniperus communis. L., the most widely distributed woody plant, and a common and well-studied dioecious shrub species in the northern hemisphere, especially in the Boreal, Subarctic tundra and Alpine regions. Our samples were collected from four sites - three from the Ural Mountains and one site from Kirkenes in Norway. To see if there were differences in radial growth between sexes we performed four different analyses. First, we used multivariate explorative statistics to see if there were gender biased sub-populations and generally found no differences. Secondly, to compare growth over the lifetime of shrubs we computed cumulative annual increments of basal area which revealed no gender-specific growth patterns. Thirdly, to test if differences in radial growth between male and female shrubs affect the resulting site-chronology, we compared individual shrub chronologies with the site-chronology and found a significant differentiation between normalized correlations of gender-specific chronologies to the site-chronology. This significant difference was restricted to an overall comparison, but not evident at individual site-level. Lastly, we compared correlations of gender-specific chronologies and a mean site-chronology with monthly climate records to find only very few meaningful differences in their responses. In summary, we could not detect any clear gender-specific growth pattern in Juniperus communis but observed a trend towards more non-climatic signals in female junipers which may affect the resulting site-chronology.
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45.
  • Hansson, Anton, et al. (författare)
  • The Danish royal flagship gribshunden : Dendrochronology on a late medieval carvel sunk in the Baltic Sea
  • 2021
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 68
  • Tidskriftsartikel (refereegranskat)abstract
    • The Royal flagship Gribshunden carried the Danish King Hans on its way to the city of Kalmar in Sweden when the ship sank in the summer of 1495. The ship caught fire while anchored north of the Stora Ek o Island and sank to the seafloor, where it lies to this day. The wreck was rediscovered in the 1970s and is remarkably well preserved.Since 2001, scientific investigations have been performed on the wreck by various organizations. In total, 13 dendrochronological samples from different parts of the ship construction have been collected and analyzed with standard dendrochronological methods with respect to age and provenance. The results show that all dated samples could have been felled during the winter season of 1482/83, although only one sample contains sapwood and waney edge. The highest correlations are obtained from reference chronologies that originate from the River Meuse drainage area, with correlations peaking around the city of Namur in Belgium. Most likely, theship was constructed in a shipyard close to the mouth of the River Meuse in the southern Netherlands. It seems King Hans realized the potential of the new ship type represented by Gribshunden, but his shipwrights did not have the knowledge to build such a ship in Denmark. Instead, he purchased the ship from abroad. This studyhighlights late medieval economic and political connections throughout northern Europe.
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46.
  • Li, Y. J., et al. (författare)
  • Growth decline of Pinus Massoniana in response to warming induced drought and increasing intrinsic water use efficiency in humid subtropical China
  • 2019
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 57:October
  • Tidskriftsartikel (refereegranskat)abstract
    • Pinus Massoniana is the most widely distributed coniferous species in southern China and one of the most distributed species for plantation in China. It is not uncertain about the responses of tree growth to the combined effects of regional drying and the increase in the intrinsic water-use efficiency (iWUE) due to increased atmospheric CO2. This study addressed this issue by comparing the tree growth patterns as represented by three tree-ring width chronologies with climate variables and three iWUE series derived from three tree-ring stable carbon isotope discrimination chronologies (Delta C-13) from Pinus Massoniana in Daiyun Mountain, central Fujian province of China. Among these chronologies, we reported the first tree-ring carbon isotope discrimination chronologies (Delta C-13) from Fuzhou area spanning last 210 years. It was found that tree radial growth is mainly limited by dry condition from May to October. Growth limitation by cold condition was only found in one high altitude site (780m) in early spring and late autumn. The tree-ring carbon discrimination was enhanced under conditions with low relative humidity and sufficient sunshine in late summer and autumn. In general, the iWUE showed a significantly increasing trend since the 1850s for all the sites in response to the increase in atmospheric CO2. However, the growth promotion of the increased iWUE on tree growth could not compensate the growth limitation caused by drought. Especially since the 1960s, a growth decline was found at two drought stressed sites at low altitudes. On the other hand, the increase in temperature of spring and autumn and iWUE has most likely enhanced tree growth at the high altitude site.
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47.
  • Linderholm, Hans W., 1968, et al. (författare)
  • Comparing Scots pine tree-ring proxies and detrending methods among sites in Jämtland, west-central Scandinavia
  • 2010
  • Ingår i: Dendrochronologia. - 1125-7865. ; 28:4, s. 239-249
  • Tidskriftsartikel (refereegranskat)abstract
    • Scots pine tree-ring width (TRW) data from Jämtland in the Central Scandinavian Mountains has been used to reconstruct summer temperatures back to 1630 BC. However, it was recently shown that this reconstructionwas of limited spatial importance. In this paper, we aim to explain this limitation in the TRW data as a temperature proxy, as well as assess the temperature information from new maximum latewood density (MXD) data. Furthermore, the effect of two standardization methods is evaluated: regional curve standardization (RCS) and a more traditional standardization, termed “non-RCS” standardization. Three TRW and two MXD sites were analyzed. Our results showed that despite the proximity to the Norwegian Sea, the MXD data is a powerful temperature proxy. Difference among sites in TRW data, especially on decadal timescales, together with a lower temperature association, suggests that other factors, such as changes in the local climate regimes, weakens the temperature signal. In general the RCS method overestimates pine growth trends in the latter half of the twentieth century, a feature not seen when using “non-RCS” standardization. This is likely due to an age-bias of older trees in most recent parts of the tree-ring chronologies. This effect will have consequences when reconstructing climate with tree-ring data. To overcome this problem, all age-classes should be represented throughout a chronology. If this is not possible, the use of “non-RCS” standardization is recommended, although this method results in a loss of low-frequency variability.
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48.
  • Linderholm, Hans W., 1968, et al. (författare)
  • Exploring teleconnections between the summer NAO (SNAO) and climate in East Asia over the last four centuries – a tree-ring perspective
  • 2013
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 31:4, s. 297-310
  • Tidskriftsartikel (refereegranskat)abstract
    • The summer North Atlantic Oscillation (SNAO), derived from the first EOF of mean sea level pressure over the extratropical North Atlantic in July and August, has a close association with climate variability over the North Atlantic region, and beyond, on both short and long time scales. Recent findings suggested a teleconnection, through the SNAO, linking climate variability over Northern Europe with that of East Asia in the latter part of the twentieth century. Here we investigate the temporal stability of that teleconnection for the last four centuries using 4261 tree-ring width series from 106 sites and, additionally, ten climate reconstructions from East Asia. Our results showed a great potential in using tree-ring width (TRW) data to extend analyses of the SNAO influence on East Asian climate beyond the instrumental period, but preferably with a denser network. The strongest SNAO-TRW associations were found in central East Asia (in and around Mongolia) and on the eastern edge of the Tibetan Plateau. In addition, the analysis showed that the association between the SNAO and East Asian climate over the last 400 years has been variable, both among regions and at specific sites. Moreover, a clear difference in the SNAO-TRW associations was found on two examined time scales, being stronger on longer timescales. Our results indicate that TRW data can be a useful tool to explore the remote influence of the SNAO on East Asian climate in the past.
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49.
  • Seim, Andrea, et al. (författare)
  • Diverse construction types and local timber sources characterize early medieval church roofs in southwestern Sweden
  • 2015
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 35, s. 39-50
  • Tidskriftsartikel (refereegranskat)abstract
    • A vast number of early medieval roof structures are still preserved in Swedish churches, yet countrywide surveys and detailed dendrochronological investigations, in tandem with building archaeology, are largely lacking. Here, we present new findings from four parish churches (Forsby, Forshem, Gökhem and Marka) in Västergötland, southwestern Sweden. The roof constructions, made from local oak and pine trees, were dated to the period between AD 1131 and 1157, making these some of the oldest preserved roof structures in Sweden and Europe. With the development of new regional pine and oak tree-ring chronologies covering the 10th to 13th centuries, we open up the discussion about medieval timber technology, wood utilization and the potential for future tree-ring based paleo-environmental exploration.
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50.
  • Tigabu, Mulualem (författare)
  • Climate response of radial growth and early selection of Larix olgensis at four trials in northeast China
  • 2022
  • Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865. ; 73
  • Tidskriftsartikel (refereegranskat)abstract
    • The objective of this study was to evaluate the age trends of genetic variation in radial growth of different provenances and growth-climate relationship in different locations. Tree-ring cores of 10 L. olgensis provenances were sampled from four representative trials with different climatic conditions in 2019. The results of ANOVA show that significant differences for DBH at different ages were detected among provenances within sites, except for 10, 11, 37, and 38 years at LS. The phenotypic and genetic coefficient of variation in different sites were generally decreased with age. Although there were large fluctuations for provenance repeatability at different ages across sites, they all belonged to high repeatability. Age-age correlations show that the early selection for DBH could be made at the age of 10 years at the semi-arid area in Heilongjiang province and the southeast slope of Xiaoxing'an Mountains, while the ages for early selection at the southeastern slope of Daxing'an Mountains and the western slope of Zhangguangcai Mountain were 13 and 12 years old, respectively. The results of growth climate relationships showed that temperature and precipitation played key roles in the radial growth of larch at each site. In the semi-arid area in Heilongjiang province, radial growth showed significant correlations with August temperature (positive) of the current year, and with previous May temperature (negative) and November temperature (positive), and previous December precipitation (positive). The current June temperature (negative) and precipitation (positive) were important factors affecting the radial growth at the southeastern slope of Daxing'an Mountains. July temperature of the current year had a negative relationship with larch growth at the southeast slope of Xiaoxing'an Mountains, while there were no significant correlations between radial growth and climatic factors at the western slope of Zhangguangcai Mountain. The results reported in this study provide a valuable insight about early selection for different sites and can serve as a reference for future breeding and improvement research.
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