A Norway spruce tree-ring width chronology for the Common Era from the Central Scandinavian Mountains

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.     

Individual and time-varying tree-ring growth to climate sensitivity of Pinus tabuliformis Carr. and Sabina przewalskii Kom. in the eastern Qilian Mountains, China

Individual tree-ring width chronologies and mean chronologies from Pinus tabuliformis Carr. (Chinese pine) and Sabina przewalskii Kom. (Qilian juniper) tree cores were collected and analyzed from two sites in the eastern Qilian Mountains of China. The chronologies were used to analyze individual and time-varying tree-ring growth to climate sensitivity with monthly mean air temperature and total precipitation data for the period 1958–2008. Climate–growth relationships were assessed with correlation functions and their stationarity and consistency over time were measured using moving correlation analysis. Individuals’ growth–climate correlations suggested increased percentages of individuals are correlated with certain variables (e.g., current June temperature at the P. tabuliformis site; previous June, December and current May temperature and May precipitation at the S. przewalskii site). These same climatic variables also correspond to the mean chronology correlations. A decreased percentage of individuals correlated with these climatic variables indicates a reduced sensitivity of the mean chronology. Moving correlation analysis indicated a significant change over time in the sensitivity of trees to climatic variability. Our results suggested: (1) that individual tree analysis might be a worthwhile tool to improve the quality and reliability of the climate signal from tree-ring series for dendroclimatology research; and (2) time-dependent fluctuations of climate growth relationships should be taken into account when assessing the quality and reliability of reconstructed climate signals.     

Characteristics of a multi-species conifer network of wood properties chronologies from Southern Australia

Progress in quantitative wood anatomy has resulted in a growing number of increasingly understood proxies from the tree-ring archive. Much of this work has been based on tree species in the Northern Hemisphere. Here, we present and examine a relatively dense network of wood property chronologies (wood density, tracheid radial diameter, cell wall thickness and ring width) from several species in Tasmania, southern Australia. We ask how the relationships amongst the different types of chronologies differ within and amongst species. We also consider how each chronology responds to monthly climate. In general terms, and similar to findings in the Northern Hemisphere, relationships between the various wood properties and climate are stronger than those between climate and ring width chronologies. An important exception to this is the highest elevation Lagarostrobos franklinii site. Additionally, strongest response to climate for the wood properties generally occurs for the concurrent growing season compared to the prior growing season for ring width. Relationships amongst the various chronology types differ for the various species, with L. franklinii also showing some variation in these relationships by site (possibly associated with elevation). Results suggest there is considerable value in further exploring the potential for developing anatomical wood chronologies for climate reconstruction from other species for which ring widths do not exhibit a strong climate signal.     

Notes towards an optimal sampling strategy in dendroclimatology

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.     

Dendrochronology in the tropics using tree-rings of Pinus kesiya

The recent decade has witnessed considerable progress in the number of tree-ring studies using the tropical conifer taxa, Pinus kesiya. Several tree-ring networks have been established in less explored regions in Northeast India, Southwest China and Vietnam. The seasonal climate response of P. kesiya tree-rings has been examined and used to reconstruct temperature and soil moisture variability over the past century and augment the short instrumental records in South and Southeast Asia. In addition to standard approaches, the application of stable isotope, wood density, and blue intensity measurements indicates a significant development in P. kesiya studies. This review elaborates the future prospects of using multiple tree-ring parameters to establish discrete proxies besides tree-ring width. We recommend blue intensity as a cost-effective alternative to quantitative wood anatomy in tropical pines, and call for routine assessments of the temporal stability of climate-growth responses to identify and study potentially non-stationary climate signals. Efforts should be made towards developing extensive networks of long P. kesiya tree-ring chronologies to extend regional climate reconstructions.     

昌岭山两个优势树种径向生长对气候变化的响应

在气候变暖背景下,树木径向生长对气候变化的响应存在不稳定性。利用采自祁连山东部余脉昌岭山两个优势树种油松和青海云杉的树轮样芯,建立树轮宽度标准年表,通过分析树轮宽度年表与气候要素的相关关系,探讨两个树种径向生长对气候变化的响应。结果表明：（1）油松年表比青海云杉年表包含更多的气候信息,其平均敏感度、标准差、信噪比和样本对总体的代表性等统计量均高于青海云杉标准年表。（2）气候要素对不同树种径向生长限制程度不同,油松径向生长主要与降水（前一年9月和当年3-8月）和气温（前一年9月）有关,但对降水的响应更为敏感,而青海云杉径向生长则受到气温（当年9月）和降水（前一年9月、当年3月和7月）的共同作用。（3）气温突变后,油松和青海云杉年表与各气温要素的相关性显著增强,而青海云杉年表与气温要素的相关性变化更明显,指示了青海云杉径向生长对气温的响应更不稳定。（4）生长季平均最低气温的升高诱导的干旱胁迫是油松和青海云杉树木径向生长-气温响应变化的主要原因。     

Development of tree-ring width chronologies and tree-growth response to climate in the mountains surrounding the Issyk-Kul Lake,Central Asia

Three tree-ring width chronologies were developed from 75 Picea schrenkiana trees ranging from low- to high-elevation in the mountains surrounding the Issyk-Kul Lake, Northeast Kyrgyzstan. The reliable chronologies extend back to the mid-18th and late-19th centuries. Spatial correlation analysis indicates that the chronologies for the relatively high-elevation trees contain large-scale climatic signals, while the chronology at relatively low elevation may reflect the local climate variability. The results of the response of tree growth to climate show that these chronologies contain an annual precipitation signal. Furthermore, the influence of temperature indicates mainly moisture stress that is enhanced with rising elevation. The tree-ring records also captured a wetting trend in eastern Central Asia over the past decades. These new tree-ring width chronologies provide reliable proxies of precipitation variability in Central Asia and contribute to the International Tree-Ring Data Bank.     

Tree-ring analysis of white cedar (Thuja occidentalis L.) archaeological and historical wood in Québec City (Québec,Canada)

In Québec City, a segment of an old wooden palisade built for protection was found buried in situ. The palisade was excavated by the Laval University archaeology field school in 2004–2005, and 29 posts were recovered and sampled. The palisade enclosed the Intendant's Palace compound, which was the residence of the governor of New France at the end of the 17th century. Tree-ring analysis was performed on wood excavated from the Intendant's Palace archaeological site (PDI) and additional wood from two historical military buildings, the Artillery Park (ART) (early 18th century) and the Québec Citadel (CIT) (17th–19th centuries). Wood identification revealed that white cedar (Thuja occidentalis L.) was used for wood construction at the three sites. Many trees used for the construction of the PDI palisade were felled after the 1690 growing season, likely in September/October 1690. Posts probably came from trees growing close to the site on the banks of the Saint-Charles River. A white cedar ring-width chronology from the Rimouski area, approximately 300 km northeast of Québec City, along the St. Lawrence River, was used for cross-dating. Archaeological and historical wood samples from two of the three sites (PDI and ART) were first assembled in a 235-year tree-ring chronology, called the Québec chronology, extending from 1489 to 1723. The two master chronologies (Québec and Rimouski) were merged into a single 513-year tree-ring chronology (1489–2001), called the Saint-Laurent chronology.     

An investigation of the snowpack signal in moisture-sensitive trees from the Southern Canadian Cordillera

Variations in mountain snowpack in the western Canadian Cordillera have widespread and important impacts on ecosystems, environmental processes and socio-economic activities (e.g. water availability downstream). Historical records of snowpack generally span only the latter half of the 20th century offering a limited perspective on the causes and uniqueness of recently observed changes across the region. This paper explores the potential utility of a network of low elevation Douglas-fir (Pseudotsuga menziesii) and ponderosa pine (Pinus ponderosa) tree ring-width chronologies to reconstruct past snowpack variations. Correlation coefficients between the tree-ring chronologies and a set of snow water equivalent (SWE) records are calculated and mapped. Separate analyses were carried out for total ring- width (TRW) and partial-ring measurements (earlywood and latewood; EW and LW). A set of Adjusted LW chronologies was also developed; in these, the relationship between LW and the preceding EW width has been removed. The ring-width chronologies exhibit moderately strong relationships with SWE records from the western Canadian Cordillera and these relationships vary in sign across the region. Distinctive regional groups are identified where chronologies exhibit same-sign correlations with SWE, in possible accordance with the elevation and characteristics of the tree-ring chronology sample sites. The EW chronologies correlate more strongly and consistently with SWE records in regions where the growth relationship with SWE is negative. The LW chronologies, and particularly the Adjusted LW chronologies, exhibit a greater number of positive correlations with the set of SWE records. Collectively these results offer valuable insights for developing a targeted sampling and/or reconstruction strategy that can exploit these different relationships with SWE to generate more robust estimates of pre-instrumental snowpack for the region.     

Oak chronology development in the Czech Republic and its teleconnection on a European scale

A prerequisite for successful dating of wooden archaeological finds and historic wooden constructions in a specific territory is the existence of a chronology. In the Czech Republic the species most frequently dated by dendrochronology is oak (Quercus spp.). There are two territories where oak forests can be found (Bohemia and Moravia/Silesia), which are divided by an area without oak – the Highlands (Vyso?ina). The previous oak chronology for the Czech Republic from 2005 was extended in 2010, and currently we have a discontinuous oak chronology (CZGES 2010) ranging from 4682 bc to 2006 ad with a large sample size between 760 ad and the present. When comparing this chronology with European chronologies, the highest degree of similarity has been observed with chronologies for Eastern Austria, most of Germany and the Polish part of South Silesia. When comparing the chronologies for Moravia/Silesia (MORGES 2010) and Bohemia (CECHGES 2010) separately with chronologies from the Pannonian Basin, the Moravian/Silesian chronology manifests higher degrees of similarity. The Czech oak chronology enlarges the European network of chronologies, which is necessary for dendroarchaeological applications mainly.     

Species identification and tree-ring dating of wood boxes excavated from the Shinan shipwreck,Korea

The Shinan shipwreck, which was excavated in the southwestern sea of Korea in the 1970s, was a Chinese trade ship from the Yuan Dynasty, traveling from China to Japan in the early 14th century (A.D. 1323). Anatomical examination indicated that the wood boxes carrying thousands of Chinese porcelain pieces on the Shinan shipwreck were made of either Cryptomeria japonica or Cunninghamia spp. The former grows in South China and Japan, and the latter in China and Taiwan. Therefore, we could not confine the origin of the wood to a single country by wood identification. However, we could date 21 wood boxes using tree-ring chronologies of C. japonica from western Japan. The outermost ring with sapwood was dated to A.D. 1316. The results from the tree-ring dating indicated that the wood boxes on the Shinan shipwreck were of Japanese rather than Chinese origin.     

Climatic response of three tree species growing at different elevations in the Lüliang Mountains of Northern China

In this study, we present the results of a dendroclimatological investigation of three coniferous tree species, Larix principis-rupprechtii, Picea meyeri and Pinus tabulaeformis, growing along an altitudinal gradient at the Lüliang Mountains in Northern China. Totally five tree-ring width chronologies were developed to explore the climate-growth responses of these tree species. No obviously regular trend associated with the increase of elevation was found by comparing the statistical characteristics of the chronologies. Correlation analysis indicated that the chronologies from lowerest to middle-high sites (SZ, BWD, BDGL and BDGP, respectively) were highly correlated, and different species from the same site showed the highest correlation. Growth–climate analysis indicated that the chronology of Larix principis-rupprechti at the uppermost site near the tree line (XWS) did not exhibit a significant response to the seasonal climatic factors, whereas the other four lower chronologies were consistently and significantly influenced by both the mean temperature from May to July and the total precipitation from March to June, regardless of tree species and elevation. The similarity of the tree growth–climate relationships of different species growing at different elevations (except that from the tree line) suggests that the trees in this region can provide common regional climate information, and combinations of multiple species (RC) are more successful in reconstructing the climate data than single species. The results of this research are very crucial for the future forest management and dendroclimatological sampling strategy in the arid to semi-arid area of northern China.     

Tree ring imprints of long-term changes in climate in western Himalaya,India

Tree-ring analyses from semi-arid to arid regions in western Himalaya show immense potential for developing millennia long climate records. Millennium and longer ring-width chronologies of Himalayan pencil juniper (Juniperus polycarpos), Himalayan pencil cedar (Cedrus deodara) and Chilgoza pine (Pinus gerardiana) have been developed from different sites in western Himalaya. Studies conducted so far on various conifer species indicate strong precipitation signatures in ring-width measurement series. The paucity of weather records from stations close to tree-ring sampling sites poses difficulty in calibrating tree-ring data against climate data especially precipitation for its strong spatial variability in mountain regions. However, for the existence of strong coherence in temperature, even in data from distant stations, more robust temperature reconstructions representing regional and hemispheric signatures have been developed. Tree-ring records from the region indicate multi-century warm and cool anomalies consistent with the Medieval Warm Period and Little Ice Age anomalies. Significant relationships noted between mean premonsoon temperature over the western Himalaya and ENSO features endorse utility of climate records from western Himalayan region in understanding long-term climate variability and attribution of anthropogenic impact.     

The dendrochronological proof of origin of oak churches located in the Czech Republic

Transcarpathian wooden churches started to dilapidate after World War I. To preserve the architectural heritage, five oak churches were transported from the region to the territory of today's Czech Republic. However, an exact date of their construction and origin of wood have not been specified and evidenced in literature. In this study, 63 samples have been collected and processed using standard dendrochronological methods. Three Baroque churches, coming from the Mukachevo district, were absolutely dated thanks to the preserved waney edge or sapwood tree rings to periods 1734–1744, 1753–1755, and 1783–1795. Two other churches, representing Gothic architecture, were transported from a more eastern part of Transcarpathian Ukraine. One of them was dated to the period after 1655 and the other could not be reliably dated using available reference chronologies. The created mean tree-ring width series representing individual churches showed strong correlations with the reference chronologies for Slovakia and northern Romania whereas correlations with the only Ukrainian chronology (Lviv region) were negligible. This could suggest low Transcarpathian tree-ring coherency and may indicate the need to create a dense network of regional tree-ring width chronologies in the regions surrounding the Carpathian Mountains.     

Dendroclimatic analysis of Pinus peuce Griseb. at subalpine and treeline locations in Pirin Mountains,Bulgaria

Tree rings are a natural archive containing valuable information about environmental changes. Among the most sensitive ecosystems to such changes are high-mountain forests. Tree-ring series from such locations are exceptionally valuable both for climate reconstructions and for studying the effects of climate changes on forest ecosystems.The objective of our study is to present new long tree-ring width chronologies of Pinus peuce Griseb. from several locations at Pirin Mountains in southwestern Bulgaria, to explore their correlation with monthly temperatures and precipitation in the research area and to assess their potential for climate reconstruction.We built three long-term index chronologies for the radial increment of P. peuce from treeline locations in the study region. The longest chronology spans 675 years. We studied the impact of monthly air temperature and precipitation on its growth for the past 86 years using multiple regression analysis. Our analysis shows that P. peuce growth is positively influenced by high temperatures at the end of the previous growing season, especially at the two sites in Banderitsa valley until the middle of the 1970s, and negatively affected by cold winters. In some of the sample plots its growth was also positively correlated with high summer temperatures. However, even at these high altitudes in some of the locations on steep slopes P. peuce showed signs of negative impact of drought during the hottest summer months (especially in August).Our chronologies contribute to the paleoclimatic record for southwestern Bulgaria, which could provide baseline information about past climate variability and improve our understanding of current and future environmental changes.     

Drought signal in the tree rings of three conifer species from Northern Pakistan

Anthropogenic and climatic stressors have affected the forests of northern Pakistan in recent decades. Several studies have been conducted to understand forest growth and its relation to the changing climate in this region, but more work needs to be done to understand this complex environment. In this study, we have collected tree core samples of three conifer species (Pinus wallichiana, Picea smithiana, and Abies pindrow) from three different sites in northern Pakistan to understand their radial growth pattern with the goal of finding a relationship between ring-width and climatic parameters (temperature, precipitation, and drought). A 610-year (AD 1406–2015), a 538-year (AD 1478–2015), and a 306-year (AD 1710–2015) long tree-ring width chronology of Pinus wallichiana, Picea smithiana, and Abies pindrow were developed, respectively, using living trees. The ring-width chronologies of these three species showed a strong positive link with the self-calibrated Palmer Drought Severity Index (scPDSI) rather than precipitation or temperature alone, indicating that soil moisture is the primary limiting climatic factor for the growth of these species in the sampling locations. The chronologies of Pinus wallichiana and Picea smithiana exhibited growth suppressions during AD 1570–1610 and the second half of 17th century while their growth was heightened from AD 1540–1560. We have found the lowest growth in Abies pindrow and Picea smithiana from AD 1900–1920, suggesting dry conditions. All three chronologies have exhibited the most rapid increase in growth during the recent decades, suggesting that this region is experiencing climate change with a strong trend towards wetter conditions.     

Dendroclimatic signals deduced from riparian versus upland forest interior pines in North Karelia, Finland

Radial growth of boreal tree species is only rarely studied in riparian habitats. Here we investigated chronologies of earlywood, latewood, and annual ring widths and blue intensity (BI; a surrogate to latewood density) from riparian lake shore and upland forest interior pines (Pinus sylvestris L.) growing in boreal forest in eastern Finland. Riparian and upland chronologies were compared to examine differences in the pine growth variability and growth response to climatic variation in the two habitats. It was found that the climatic variables showing statistically significant correlations with the tree-ring chronologies were related to snow conditions at the start of the growing season. Deeper snowpack led to reduced upland pine growth, possibly due to delayed snowmelt and thus postponed onset of the growing season. Warm late winters were followed by increased riparian pine growth because of earlier start of the snow-melt season and thus a lower maximum early summer lake level. Moreover, riparian pines reacted negatively to increased rainfall in June, whereas the upland pines showed a positive response. Latewood growth reacted significantly to summer temperatures. The BI chronology showed a strong correlation with warm-season temperatures, indicating an encouraging possibility of summer temperature reconstruction using middle/south boreal pine tree-ring archives.     

Recent growth increase in endemic Juglans boliviana from the tropical Andes

The spatial coverage of tree-ring chronologies in tropical South America is low compared to the extratropics, particularly in remote regions. Tree-ring dating from such tropical sites is limited by the generally weak temperature seasonality, complex coloration, and indistinct anatomical morphology in some tree species. As a result, there is a need to complement traditional methods of dendrochronology with innovative and independent approaches. Here, we supplement traditional tree-ring methods via the use of radiocarbon analyses to detect partial missing rings and/or false rings, and wood anatomical techniques to precisely delineate tree-ring boundaries. In so doing we present and confirm the annual periodicity of the first tree-ring width (TRW) chronology spanning from 1814 to 2017 for Juglans boliviana (‘nogal’), a tree species growing in a mid-elevation tropical moist forest in northern Bolivia. We collected 25 core samples and 4 cross-sections from living and recently harvested canopy-dominant trees, respectively. The sampled trees were growing in the Madidi National Park and had a mean age of 115 years old, with certain trees growing for over 200 years. Comparison of (residual and standard) TRW chronologies to monthly climate variables shows significant negative relationships to prior year May-August maximum temperatures (r = −0.54, p < 0.05) and positive relationships to dry season May-October precipitation (r = 0.60, p < 0.05) before the current year growing season. Additionally, the radial growth of Juglans boliviana shows a significant positive trend since 1979. Our findings describe a new and promising tree species for dendrochronology due to its longevity and highlight interdisciplinary techniques that can be used to expand the current tree-ring network in Bolivia and the greater South American tropics.     

Assessing cross-datable distinct annual growth rings in non-native Pinus kesiya Royle ex Gordon in Zambia

The response of non-native forest plantation trees to climate change remains poorly understood.We hypothesized that precipitation and temperature modulate tree-ring width chronology at each site and that higher tree growth is exhibited at remote sites than sites near copper mines. This study investigates if the annual tree-ring boundaries in non-native Pinus kesiya Royle ex Gordon in Zambia are distinct, cross-datable, and coherent with climate signal. We collected increment cores from live trees and climate data near and further away from emission sources and developed site tree-ring width chronologies. Based on cross-dating and chronology building statistics (i.e., ESP > 0.85; Glk > 0.6 and series inter-correlation > 0.4), P. kesiya posses cross-datable distinct annual growth ring boundaries that exhibited a high climate signal at both sites. The tree-ring width chronology was positively modulated by precipitation and negatively by solar radiation and temperature. The dry season precipitation was the limiting factor for the growth of P. kesiya. The predicted decrease in dry season precipitation and increase in temperature and solar radiation may reduce tree growth of P. kesiya, reduce productivity, and extend the rotation age. The mean ring width in P. kesiya was not significantly (p = 0.296) different between sites. However, the mean basal area increment at the site near the emission source (Ichimpe) was significantly (p < 0.001) higher than at the remote site (Chati), suggesting site-specific influences that require investigation. We recommend evaluating the causes and consequences of tree growth variation between sites and their relation to environmental variation, including microclimate, soils, and pollution. In this regard, an assessment of site-specific ring-width chronology and tree growth variation in this study directly contributes to an improved understanding of non-native P. kesiya ecology, and it offers the potential to study trees' responses to edaphic and climatic factors. Knowing these responses deepens our understanding of non-native pine tree growth in the face of climate change, given the significant role of tropical forests in the global carbon cycle.