Tree-ring and varve scales combined,c. 13500 B.C. to A.D. 1977

Varve chronologies are of several kinds but glacial varves respond to summer temperature and fluvial varves to summer rainfall.Tree-ring chronologies near the timberline respond to summer temperature but European oak chronologies respond to summer rainfall.Certain global features of the weather of the summer season, notably the Biennial Index, are therefore parameters that can be used for cross-dating both varves and tree-rings in different continents.Characteristic curves for different parameters in the Late Glacial (Zones Ia, Ib and II) and in the past thousand years are presented. A moisture curve is given for the North European Plain (200 B.C.–A.D. 1100). A conversion chart for tree-rings and radiocarbon dates is extended back into the Late Glacial on the tentative assumption that the radiocarbon error was about 950 years at the beginning of the Holocene (III/IV), i.e. that 10300 b.p. should be 11250 B.P. or 9300 B.C.Supplementary sources of information useful in obtaining approximate dates include: (a) palaeomagnetism; (b) tephrochronology and X-ray analysis; (c) cycle analysis; (d) climatic peculiarities associated with specific radiocarbon centuries; (e) X-ray analysis of specific varves; and (f) new methods of varve-analysis.The varve-series used for the Late Glacial, if the author's cross-dating between North America and Scandinavia is acceptable, constitute a floating chronology of about 4000 years. Given approximate ¹⁴C dates for any long series of varves or tree-rings in one part of the world, it is now possible to obtain cross-dating with any other long series in another part of the world, and it will be easy to replace the tentative ‘950-year’ error by a precise figure determined from a combined varve and tree-ring scale extending back from the present day to (say) the zero of Sauramo's scale for varves in Finland. In the meantime the ‘950’ is mnemonically convenient, as this would make the year on the B.C. scale one thousand less than the year on the b.p. scale.     

Spectral analysis on mountain pine tree-ring chronologies

The present study applies classic spectral analysis techniques to investigate cyclic patterns in four tree-ring chronologies of Pinus montana Miller from the Central Italian Alps (Valle del Gallo). Three of the chronologies were derived from mountain pine populations located in relatively undisturbed areas of the valley bottom and valley slopes, and one from a population located in an area of the valley bottom occasionally affected by sheetfloods. Each chronology consists of raw, standard, and residual data. We estimated power spectra by applying the Blackman–Tukey Method, the Maximum Entropy Method, the Multitaper Method, and the Lomb–Scargle Fourier transform, and tested the results against appropriate red noise models. The power spectra of the standard chronologies from undisturbed areas yielded statistically significant and reproducible interdecadal-scale cyclicities with main peaks closely spaced around a mean value of 0.05 cycle/year, in association with statistically non-significant albeit reproducible peaks at higher frequencies. The chronology of trees affected by sheetfloods yielded no statistically significant cyclicities, probably because sheetfloods altered tree growth. Raw chronologies, instead, yielded power spectra dominated by the growth trend, while residual chronologies yielded flat power spectra. Our analysis suggests that tree growth, if not disturbed by external geomorphological factors, was controlled by environmental and/or climatic conditions that oscillated in the last 150 years on interdecadal (20 years) to decadal scales.     

Dendroclimatic signals in the pine and spruce chronologies in the Solovetsky Archipelago

Searching for a robust tree-ring parameter useful for paleoclimatic purposes is one of the most demanding topics in the modern paleoscience. Since Blue Intensity has already expressed itself in different geographical locations all over the world as a possible replacement for maximum density, close attention is paid to investigate features of the inferred signal. The Solovki Islands is a unique location in Northern Russia where two important factors that make this territory attractive for developing a long tree-ring chronology have been met: modern long-living trees and building activities using old trees that were started by monks in the middle of the 16th century. The main goal of the research is to develop pine and spruce chronologies based on tree-ring width (TRW) and delta Blue Intensity (dBI) and to assess the ability of these parameters to be used as climate predictors. As a result, 14 conifer chronologies from 7 sites (4 for pine and 3 for spruce) were developed. The composite pine and spruce chronologies span a period of 474 and 378 years each. Cross-correlation of dBI-based chronologies of both conifers is high (r = up to 0.71 while for TRW-based chronologies it is lower on average (−0.18 to 0.63). Intra-species correlation of TRW chronologies in some cases achieved even negative values (r = −0.18. Discrepancies found between TRW chronologies of pine and spruce could be explained by differences in climatic signals. Response function analysis with monthly temperatures revealed that growth of pine depends on the previous August, while spruce has a temporally stable and strong relation to June temperatures. Compared to TRW, dBI-based chronologies have a high correlation with summer temperatures (r = 0.64 and 0.66 for spruce and pine, respectively). Presented research points out the importance of the response function analysis suggesting that depending on goals of the study several tree-ring parameters could be used, e.g., tree-ring width of spruce responses to June temperatures, while dBI to the whole summer.     

Spectral analysis on mountain pine tree-ring chronologies

The present study applies classic spectral analysis techniques to investigate cyclic patterns in four tree-ring chronologies of Pinus montana Miller from the Central Italian Alps (Valle del Gallo). Three of the chronologies were derived from mountain pine populations located in relatively undisturbed areas of the valley bottom and valley slopes, and one from a population located in an area of the valley bottom occasionally affected by sheetfloods. Each chronology consists of raw, standard, and residual data. We estimated power spectra by applying the Blackman–Tukey Method, the Maximum Entropy Method, the Multitaper Method, and the Lomb–Scargle Fourier transform, and tested the results against appropriate red noise models. The power spectra of the standard chronologies from undisturbed areas yielded statistically significant and reproducible interdecadal-scale cyclicities with main peaks closely spaced around a mean value of ∼0.05 cycle/year, in association with statistically non-significant albeit reproducible peaks at higher frequencies. The chronology of trees affected by sheetfloods yielded no statistically significant cyclicities, probably because sheetfloods altered tree growth. Raw chronologies, instead, yielded power spectra dominated by the growth trend, while residual chronologies yielded flat power spectra. Our analysis suggests that tree growth, if not disturbed by external geomorphological factors, was controlled by environmental and/or climatic conditions that oscillated in the last ∼150 years on interdecadal (∼20 years) to decadal scales.     

Radiocarbon and dendrochronology

The radiocarbon dating method relies on calibration through an independent dating method. Dendrochronology is an ideal partner of radiocarbon, because tree-rings are close-to-perfect archives of the atmospheric ¹⁴C level, and the tree-ring time scale can be built beyond doubt with high replication. Over the past 30 years, several stages of ¹⁴C calibration data sets have been constructed from the work of tree-ring laboratories in Europe and North America. This process is outlined and the present state is documented. In turn, ¹⁴C age fluctuations, caused mainly by helio-magnetic changes, can be used to anchor floating tree-ring sections to the calendar scale with a precision of a few decades.     

Landscape history in the subalpine karst region of Moncodeno (Lombardy Prealps, Northern Italy)

In situ larch stumps have been found above the present forest line in the karst region of Moncodeno, Grigna Settentrionale, northern Italy, an area where very few trees currently grow. Samples from living trees at the treeline and in the forest nearby were collected to develop a reference chronology for cross-dating the stumps. The latter span the period between 1218 and 1900, and together with the living trees, which cover the last 150 years, they have led to the development of a 784-year larch tree-ring chronology (1218–2001). Age and location of the stumps reflect past human activity. Deforestation and grazing have intensified the erosion processes in the area. The soil has thinned out and fragmented allowing karst landforms, previously buried by the soil, to emerge. Presently, the rocky outcrops limit the establishment of young larches so that only few scattered trees are currently found.     

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.     

沈阳市区古油松年轮宽度年表的建立

以沈阳城区昭陵古油松为样本,建立了古油松标准化年表、差值年表和自回归年表. 结果表明,年表与沈阳1月和4月的极端最低气温显著相关;与2月的降水量、年均水汽压分别为显著和极显著相关,年表对4、5、9和10月的水汽压响应较强,且均与自回归年表显著相关.年表与相对湿度的年指标,4、5、6、9、10和11月月指标的相关性较高,其中与年值和5月值分别为显著相关（差值年表除外）和极显著相关.蒸发与油松的生长在全年和绝大部分月份呈负相关,其中5月最明显,而1月的蒸发量与油松年表呈正相关.年表的窄化突变佐证了1 700年以来32次历史资料记录的主要旱灾年.沈阳地区的油松生长也受全球或半球尺度温度波动的影响.3种年表对以往太阳黑子的变化和地磁的活动呈现明显负相关,其中与太阳黑子活动存在显著的11年、23年和50年左右的公共周期,与地磁指标在10.5年、20年和45年左右存在共同的周期变化.     

沈阳市区古油松年轮宽度年表的建立

以沈阳城区昭陵古油松为样本,建立了古油松标准化年表、差值年表和自回归年表．结果表明,年表与沈阳1月和4月的极端最低气温显著相关;与2月的降水量、年均水汽压分别为显著和极显著相关,年表对4、5、9和10月的水汽压响应较强,且均与自回归年表显著相关．年表与相对湿度的年指标,4、5、6、9、10和11月月指标的相关性较高,其中与年值和5月值分别为显著相关（差值年表除外）和极显著相关．蒸发与油松的生长在全年和绝大部分月份呈负相关,其中5月最明显,而1月的蒸发量与油松年表呈正相关．年表的窄化突变佐证了1700年以来32次历史资料记录的主要旱灾年．沈阳地区的油松生长也受全球或半球尺度温度波动的影响．3种年表对以往太阳黑子的变化和地磁的活动呈现明显负相关,其中与太阳黑子活动存在显著的11年、23年和50年左右的公共周期,与地磁指标在10．5年、20年和45年左右存在共同的周期变化．     

North Atlantic Oscillation influences on radial growth of Pinus pinea on the Italian mid-Tyrrhenian coast

The North Atlantic Oscillation (NAO) is the most important source of winter atmospheric variability in the northern hemisphere. NAO inversely reflects the precipitation regime, which plays a fundamental role in Mediterranean regions, e.g., by recharging the water table. As no attempt has been made thus far to analyze the relationship between NAO variability and tree radial growth in coastal Mediterranean conifers, this paper identifies the monthly, winter, annual, and decadal influence of NAO on tree-ring chronologies of six planted Pinus pinea L. populations distributed along the Tyrrhenian coasts of central Italy. Through multidimensional analyses, we identified tree-ring chronology associations in two main groups. The influence of NAO on the regional chronologies was identified with correlation functions for the comparison period between 1949 and 2003 at both annual and decadal timescales. Results indicate that winter NAO influence on radial tree growth at annual and decadal timescales may depend on geographical location, site characteristics, and the age structure of tree-ring chronologies. These results contribute to a better understanding of the P. pinea coastal forest ecology and provide evidence of large-scale climatic forcings that influence forest Mediterranean ecosystems.     

Climate–growth relationships of the dominant tree species from semi-arid savanna woodland in Ethiopia

Long-term climate–growth relationships, were examined in tree rings of four co-occurring tree species from semi-arid Acacia savanna woodlands in Ethiopia. The main purpose of the study was to prove the presence of annual tree rings, evaluate the relationship between radial growth and climate parameters, and evaluate the association of El Niño and drought years in Ethiopia. The results showed that all species studied form distinct growth boundaries, though differences in distinctiveness were revealed among the species. Tree rings of the evergreen Balanites aegyptiaca were separated by vessels surrounding a thin parenchyma band and the growth boundary of the deciduous acacias was characterized by thin parenchyma bands. The mean annual diameter increment ranged from 3.6 to 5.0 mm. Acacia senegal and Acacia seyal showed more enhanced growth than Acacia tortilis and B. aegyptiaca. High positive correlations were found between the tree-ring width chronologies and precipitation data, and all species showed similar response to external climate forcing, which supports the formation of one tree-ring per year. Strong declines in tree-ring width correlated remarkably well with past El Niño Southern Oscillation (ENSO) events and drought/famine periods in Ethiopia. Spectral analysis of the master tree-ring chronology indicated occurrences of periodic drought events, which fall within the spectral peak equivalent to 2–8 years. Our results proved the strong linkage between tree-ring chronologies and climate, which sheds light on the potential of dendrochronological studies developing in Ethiopia. The outcome of this study has important implications for paleoclimatic reconstructions and in restoration of degraded lands.     

Multi-proxy crossdating extends the longest high-elevation tree-ring chronology from the Mediterranean

Annually precise dating is the cornerstone of dendrochronology. The accurate crossdating of relict wood is, however, frequently challenged during early chronology periods when sample replication is typically low. Here we present a multi-proxy approach in which stable carbon (δ¹³C) and radiocarbon (¹⁴C) isotope data are used to evaluate and correct dating errors in the early period of the longest high-elevation tree-ring chronology from the Mediterranean Basin. The record was initially developed using 878 tree-ring width (TRW) and 192 maximum latewood density (MXD) series from living and relict Bosnian pines (Pinus heldreichii) from Mt. Smolikas in Greece to reconstruct hydroclimate and temperature variability back to the 8th century. New annually resolved and non-pooled δ¹³C series now suggest a re-dating of first millennium relict pine samples during a period when sample replication was too low for proper TRW and/or MXD crossdating. The associated correction shifts the start of the Mt. Smolikas chronology from 575 back to 468 CE, a change independently confirmed by wiggle-matching annual ¹⁴C data along the 774/775 CE cosmic event. Our study demonstrates the importance of independent age validation for robust chronology development and shows how multi-proxy crossdating can improve dating success during periods of low sample replication.     

Validation of yellowedge grouper, <Emphasis Type="Italic">Epinephelus flavolimbatus</Emphasis>, age using nuclear bomb-produced radiocarbon

Age validation and estimates of longevity of yellowedge grouper (Epinephelus flavolimbatus) from the Gulf of Mexico (GOM) are needed to inform fishery management decisions. Yellowedge grouper sagittal otoliths (n = 100) were collected, aged using conventional means, and cores were submitted for radiocarbon (¹⁴C) measurement. Radiocarbon values of yellowedge grouper otoliths were compared to established radiocarbon chronologies in the region to validate the age and ageing methodology of this species. The yellowedge grouper chronology displayed a similar sigmoidal trend as previously published chronologies. In addition to the core analysis, multiple areas on otolith sections from eight specimens were analyzed for Δ¹⁴C to validate age estimates for fish born prior to the ¹⁴C increase. Our results indicate that yellowedge grouper live longer than previously reported (minimum of 40 years based on radiocarbon measurements). The validated ageing methodology supported an estimated maximum longevity of 85 years and established that yellowedge grouper have the longest lifespan currently known for any species of grouper in the GOM. Results also indicate a depth-age interaction in that material extracted from adult otolith sections assigned to post-bomb dates exhibited lower Δ¹⁴C values than cores (juvenile material) assigned to the same post-bomb dates. This finding is likely explained by lower ¹⁴C levels reported from water masses at deeper depths (>100 m) which are inhabited by adults.     

Dendrochronology of maritime pine in the middle of the Atlantic Ocean

The Azores Archipelago, located in the North Atlantic Ridge, experiences heavy rainfall and mild temperatures with weak seasonal differences due to oceanic influence. To our knowledge, there have been no dendrochronological studies in the Azores. The aim of this study is to explore the dendrochronological potential of Pinus pinaster Ait. growing in this archipelago and to determine what limiting factor is regulating tree growth. To do so, we have sampled adult maritime pine trees growing in a plantation, in the Pico island of the Azores.Tree ring boundaries were not always easily distinguished, suggesting that in some years cambial activity did not stop during winter. Despite this, it was possible to successfully crossdate the tree-ring series and to establish a tree-ring width chronology with a strong common signal. Climatic correlations revealed a positive response to spring precipitation but no temperature signal in the tree-ring width chronology. Tree-ring width was also negatively correlated with the North Atlantic Oscillation (NAO) and the sea level pressure (SLP) in May − June.Intra-annual density fluctuations (IADFs), which are anatomical features formed in response to variations in environmental conditions during the growing season, were present in 85% of the tree rings. IADFs were identified based on its position within the ring: type E⁺, characterized as a transition wood from early- to latewood; type L, the most frequent, characterized as earlywood-like cells within latewood; and type L⁺, characterized as earlywood-like cells between latewood and earlywood of the next tree ring. Each IADF type presented a unique climatic signal: type E⁺ was positively correlated with early summer precipitation and early spring temperature; type L was positively correlated with early autumn precipitation and temperature; and type L⁺ was positively correlated with late autumn precipitation.In conclusion, the tree-ring width chronology established for maritime pine growing in the Pico Island of Azores contains a clear climatic signal for spring precipitation, whereas IADFs frequency correlated better with precipitation later in the growing season. For this reason, we suggest that IADFs should be included in future dendrochronological studies in the Macaronesia Biogeographical region since they can improve the climatic signal present in tree-ring width chronologies.     

Comparison of living-tree and subfossil ringwidths with summer temperatures from 18, 19 and 20 centuries in Northern Finland

This work seeks to analyse the importance of summer-temperatures an the tree-ring growth of Scots pine (Pinus sylvestris L.) during the past three centuries. Three living-tree chronologies, subfossil pine chronology and one composite tree-ring chronology were constructed from latitudinal and altitudinal forest-limits of pine in northern Finland and compared with meteorological data comes from three localities. These data include early instrumental temperature observations from 18^th and 19^th centuries. The modern meteorological data covers the period from 1860 to present. Response functions were derived by means of Pearson correlations using five subperiods as follows: 1738–1748, 1802–1822, 1825–1835, 1861–1926 and 1927–1992. It was demonstrated that the correlations between ringwidths and mid-summer (July) temperatures did not vary significantly as a function of time. Early(June) and late-summer (August) mean temperatures were secondary in relation to mid-summer temperatures in controlling the radial growth. Early-summer temperatures governed pine radial growth most clearly during the 19^th century, whereas late-summer temperatures had strongest influence an ring-widths during the 18^th century and later part of the 20^th century. There was no clear signature of temporally reduced sensitivity of Scots pine ring-widths to mid-summer temperatures over the periods of early meteorological observations. Subfossil pine chronology, constructed using pines recovered from small Jakes along the forest-limit zone, showed a consistent pattern of response to summer-temperatures in relation to living-tree chronologies.     

Reconstruction of pre-monsoon weather conditions in northwestern Thailand from the tree-ring widths of Pinus merkusii and Pinus kesiya

Two pine species, Pinus merkusii and Pinus kesiya, native in Thailand were studied for their potential to reconstruct past weather conditions from their tree rings. Altogether, cores from 209 Merkus pines and from 205 Khasi pines were sampled at 16 sites. Standard methods were applied to assemble tree-ring chronologies for each site and tree species. The longest site chronology of Merkus pine and Khasi pine covered 314 and 183 years, respectively. Principal component analysis (PCA) illustrated a close clustering of all, except two, site chronologies on the PC1 axis, indicating a strong signal common for both pine species throughout NW Thailand. However, along the PC2 axis, there was a distinct separation between the Merkus pine and the Khasi pine site chronologies, which was possibly due to the species-specific differences in site altitudes. Simple correlations between the PC1 time series and a regionalized climate data set showed a highly negative association with temperature during the pre-monsoon period from March to May. Since, pre-monsoon temperature and rainfall were negatively correlated with each other, we used the PC1 as a direct proxy for pre-monsoon weather conditions (warm/dry vs. cool/wet) back to 1834 AD.     

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.     

芦芽山华北落叶松(Larix principis-rupprechtii)树轮宽度年表对气候因子的响应

在芦芽山地区采集3个不同海拔的华北落叶松(Larix principis-rupprechtii),在传统去趋势的基础上,采用"signal-free"方法对拟合曲线进行修正,避免了中等频率的气候信息引起的拟合偏差,最终建立3个不同海拔树轮宽度标准年表(STD)。同时以10a为界对上述年表进行滤波处理,得到3个低频年表。年表特征值表明,随着海拔升高,年轮平均轮宽变窄,敏感性和高频信息增强,低频信息减弱,这可能与逐渐恶劣的生境有关。中、低海拔年表的低频信息更一致,中、高海拔的高频信息更接近,而高、低海拔无论是标准年表还是高频、低频年表相似性均较差。树轮气候响应分析显示,低海拔STD年表与5月最低温负相关最为显著,STD和低频年表均与5、6月份土壤温度显著负相关,说明生境暖干,树木主要受生长季的干旱胁迫;中海拔STD年表与当年5月最高温正相关最为显著,STD和低频年表与土壤温度相关均不显著,说明生境逐渐变得冷湿,生长季的低温成为树木生长的限制因子;高海拔STD年表与气象要素相关不显著,低频年表与当年4月土壤温度正相关,说明高海拔最为冷湿,并有季节性冻土分布,生长季的土壤低温成为树木生长的限制因子。因此,全球变暖的趋势将更有利于高海拔树木的生长,而低海拔树木的干旱胁迫进一步加剧。