Central England temperature since AD 1850: the potential of stable carbon isotopes in British oak trees to reconstruct past summer temperatures

In regions with seasonal temperate climatic regimes, tree growth is rarely controlled by any single environmental factor. As a consequence, the development of robust palaeoclimate reconstructions has proved challenging. Tree‐ring stable carbon isotope ratios (δ¹³C), however, are controlled primarily by photosynthetic rate, not by net growth. Therefore, at sites where climatic controls on tree‐ring growth are not strongly expressed, a robust (isotopic) palaeoclimate signal may still potentially be preserved. This hypothesis was tested using a 160‐year record of δ¹³C measured from the pooled latewood cellulose of six Quercus petraea L. (sessile oak) trees from Allt Lan‐las in West Wales, UK. Raw δ¹³C values were corrected for changes in the isotopic ratio of atmospheric carbon dioxide and for changes in the behaviour of trees due to the increasing availability of atmospheric CO₂ since AD 1850. Strong correlations with local summer temperature and sunshine are reported, and also with the Central England Temperature record over the full length of the isotopic chronology (AD 1850–2010) (r = 0.69, P < 0.001). We conclude that tree‐ring stable isotopes can be used to extract strong palaeoclimate signals even from oak trees growing in a temperate maritime climate. This demonstrates the potential for extracting robust palaeoclimatic information from the very long and well‐replicated oak chronologies which have been developed in western and central Europe primarily for dating rather than palaeoclimatic research purposes. Copyright © 2012 John Wiley & Sons, Ltd.     

柴达木盆地东北部3500年树轮定年年表的初步建立*

利用柴达木盆地东北部山地上生长的活树,尚未倒伏的死树和山前洪积扇上古墓中保存的椁木、棺木和封土柏木,在树轮年代学交叉定年技术的支持下,建立了该区长达3500年的树轮定年年表。最长的活树样本可追溯到公元404年,古木样本覆盖的时段是公元前1580年~公元793年,而死树样本覆盖了公元130~1794年。3种样本在时间上具有很长的重叠时段,为建立长定年年表提供了可行。样本间能够很好地交叉定年。此外,古木和死树在重叠时段轮宽变化的相关系数是0.51,死树和活树的是0.41,并且古木和活树的是0.61。这种极显著的相关关系说明建立长定年年表是可能的。将程序COFECHA为每个活树样点保存的定年序列、古木的定年序列和死树的定年序列放在一起,再运行程序COFECHA,就建立了一个基于621棵树的样本量组成的总定年年表。该年表的取材完全独立于已发表的都兰年表,在时间上比都兰年表向前延伸了近1000年,使其能够达到商、周朝代。与调整后的都兰年表对比,发现两者在公元前328年~公元2000年之间完全能够交叉定年。文章所建的树轮定年年表是国内目前最长的连续年表,它可为我国西北干旱-半干旱区树轮长序列的定年提供标尺。     

Up to 400‐year‐old Rhododendron shrubs on the southeastern Tibetan Plateau: prospects for shrub‐based dendrochronology

In harsh and treeless environments, shrubs constitute the dominant growth form of woody plants, thus offering the opportunity to extend dendrochronological networks beyond the uppermost and northernmost distribution limits of trees. However, shrub‐based dendrochronology has so far resulted in only a few long and climate‐responsive ring‐width chronologies at such stressful sites, particularly above the alpine tree line. A previous study on an alpine Rhododendron shrub species resulted in <80‐year‐long ring‐width chronologies. Here, we collected Rhododendron aganniphum var. schizopeplum stems from elevations between 4000 and 4500 m a.s.l. on the SE Tibetan Plateau and built six tree‐ring width chronologies. One of them is 401 years long and well replicated from AD 1670 to 2011 (EPS>0.85), thus representing the longest shrub chronology available to date. A principal component analysis (PCA) converted the total variability of all six site chronologies into PCs. Then, the six site chronologies and the PC1, accounting for 65.9% of the total variance of the tree‐ring width, were correlated with time series of monthly climate data. Based on this, the year‐to‐year variability of the ring‐width indices was positively correlated with July temperature, which thus turned out to be the dominant factor controlling growth. Accordingly, such long shrub‐ring chronologies may act as climatic and ecological proxies in treeless environments of the Tibetan Plateau.     

Dating prehistoric bog-fires in northern England to calendar years by long-distance cross-matching of pine chronologies

The ages of prehistoric fires can be approximated by radiocarbon dating of charcoal or associated material, but such dating is often inaccurate and at best imprecise. Pine trunks preserved in British and Irish peats occasionally show firescars, which might be dated through dendrochronology to yield calendar-year dates. However, unlike oak, there is no master pine chronology to provide absolute dates, so dating is dependent on interspecies cross-matching; for sites in the British Isles with no dated oaks, calendar-year dating of prehistoric pines has hitherto proved impossible. We present a first success in dating, accurately and precisely, prehistoric fire events recorded in subfossil bog-pine trunks, using long-distance cross-matching of pine chronologies between White Moss, Cheshire, and the Humberhead Levels, England. Results demonstrate a bog-fire in Cheshire in spring 2800 BC, and again in 2710 BC, between spring and summer. Further successful long-distance cross-matching of pine would permit international climatological comparisons. © 1997 John Wiley & Sons, Ltd.     

Climatic significance of D/H and13C/12C ratios in Irish oak cellulose

δD and δ¹³C analyses of cellulose nitrate from two modern Irish oak trees that form part of the 7400 year long chronology were carried out, covering a period of 123 years (1861–1983 A.D.) with a 5 year resolution so as to assess the potential of this long chronology for retrieval of palaeoenvironmental data. One of the trees (Q5293) showed significant correlations of δD, δ¹³ C and ring width with mean annual temperatures as recorded at the Armagh weather station nearby and the mean fall temperatures of Central England. The other tree (Q5296) did not exhibit any significant climatic correlations either because it grew utilizing a nearby permanent source of ground water or because the intra-ring isotopic variations in Irish oak are significant enough to mask the climatic signal. Whilst our results have given a positive indication of the usefulness of these trees for palaeoenvironmental information, more trees need to be analysed to confirm our findings. Even though one of the trees did not exhibit climatic correlations, both trees show a significant positive correlation of δ¹³C and a negative correlation of δD with ring width variations. Furthermore, two tree samples that grew during the 1620s B.C., when a volcano is thought to have erupted on the Aegean island of Santorini, show increased δD and decreased δ¹³C for one to two decades following the eruption, though the magnitudes of change seem to vary with site and trees. We have proposed a possible mechanism based on tree phenology to explain both the above effects.     

新疆阿勒泰地区小冰期特征的树轮δ13C记录

建立了新疆阿勒泰地区一个长约450a的落叶松树轮碳同位素年表.该年表一个最为明显的特点是1850年后年轮δ¹³C显著降低,这是化石燃料燃烧和土地利用方式改变的缘故.在1550—1850年期间,该年表经历了明显的距平“正负”(即暖冷)变化:17世纪年轮δ¹³C值相对偏负,气温较低,18世纪年轮δ¹³C值相对偏正,温度较高.根据已有的树轮δ¹³C温度系数,17世纪的温度相对偏低约0.67～2.46℃.广泛的区域性对比表明,该年表所揭示的小冰期温度变化具有较高的可信度。     

Alkaline Intrusives at the East Foot of the Taihang-Da Hinggan Mountains: Chronology, Sr, Nd and Pb Isotopic Characteristics and Their Implications

Based on the Rb-Sr isochron dating results, this paper suggests that the alkaline intrusive belt at the east foot of the Taihang-Da Hinggan Mountains were formed between 135 and 122 Ma. And the alkaline intrusives in the north and south sections of this belt have entirely different Sr, Nd and Pb isotopic characteristics, i.e., all the rocks in the south section have positive εSr(t) and negative εNd(t) values and all those in the north have the opposite values. On the εSr(t) versus εNd(t) correlation diagram, the samples from the south are concentrated along the enriched mantle evolution trend lines and nearby, while those from the north fall along the depleted mantle trend lines and nearby. On the Pb isotope composition diagram, most of the samples from the south section fall on the mantle Pb evolution line and nearby, while those from the north lie between the Pb evolution lines of the mantle and the erogenic belt. The above-stated isotopic characteristics not only indicate that the source rocks of     

Model evaluation for reconstructing the oxygen isotopic composition in precipitation from tree ring cellulose over the last century

The oxygen isotope composition of tree rings is controlled by many factors, including temperature, amount of precipitation, and changes in relative humidity. In this study we present a modified leaf-water model (from Dongmann et al. [Radiation and Environmental Biophysics 11 (1974) 41]) that can be used to calculate the isotopic composition of the source-water (and thus of precipitation) that a tree used during the growing season. The calibration of the model was accomplished by comparing a previously measured oxygen isotope tree ring chronology from Central Switzerland with the Swiss Network for Isotopes in the Hydrologic Cycle station at Bern from 1971 to 1995 and integrating temperature, relative humidity data, and ring-width. In particular, our efforts focused on understanding the significance of the dampening factor f, which we relate to changes in humidity, and its variability over both the calibration period (1971 to 1995) and the study period (1913 to 1995). Our results indicate that f (ranging between 0.27 to 0.49) is variable, based on correlation with relative humidity, average daily temperature and ring width index. Using this model, we have constructed a record of the oxygen isotope composition of precipitation during the growing season (May through September) for the last century in central western Europe. This approach can be potentially used in other locations where isotopic and meteorological data are available to extend records of the isotopic composition of precipitation back in time beyond observational records.     

树轮纤维素中氧同位素温度意义

树轮作为自然档案中的一种, 其同位素研究是较为新颖的领域文章比较系统地从树轮纤维素的提取、氧的来源、植物体内氧的分馏、与温度变化的关系等４ 个方面评述了树轮纤维素氧同位素组成的气候学意义已有的研究结果表明, 树轮纤维素氧同位素组成的变化是温度变化的良好载体, 但在定量恢复古温度变化时遇到了不少限制, 有待于进一步完善分馏模型     

树木年轮分析在环境变化研究中的应用

鉴于环境变化与树木生长关系密切,可以通过对树木年轮变异状况的分析,获取环境变化的信息。本文概述了树木年轮分析的基本原理、研究途径以及已经取得的进展与应用前景。     

砂岩型铀矿微区原位U-Pb同位素定年技术方法研究

铀矿物定年一直是成矿年代学中的难点,随着微区原位U-Pb同位素定年技术的发展,可以直接针对矿石矿物(铀矿物)进行同位素定年;但是其中的砂岩型铀矿由于其存在状态复杂,在原位定年中剥蚀要求高,也缺乏合适的外部校正标准物质,所以定年准确度有待提高。本文研究了两种微区原位U-Pb同位素测年的方法,对砂岩型铀矿定年进行了尝试,试图解决铀矿测年中的无基体匹配问题并提高砂岩型铀矿定年水平。一是建立了一种激光剥蚀多接收电感耦合等离子体质谱仪联合电子探针进行微区原位U-Pb同位素测年的技术(LA-MC-ICP-MS&EMPA)。通过优化实验方法,对秦岭陈家庄花岗岩型铀矿进行了测试,获得与同位素稀释热电离质谱法(ID-TIMS)一致的年龄结果,证明了微区原位U-Pb同位素测年无基体匹配标准物质分析的可行性;并利用此法获得鄂尔多斯盆地红庆河和塔然高勒砂岩型铀矿的微区原位U-Pb同位素年龄信息。二是尝试了利用飞秒激光剥蚀多接收电感耦合等离子体质谱法(fsLA-MC-ICP-MS)对红庆河和宁夏宁东砂岩型铀矿样品进行微区原位U-Pb同位素定年,并获得了微区原位U-Pb同位素年龄,表明飞秒激光剥蚀技术在砂岩型铀矿定年中有很好的应用前景。本文提出,比较单一且年龄偏老的单矿物样品可以选择LA-MC-ICP-MS&EMPA联合法进行分析,需要高空间分辨率的样品建议使用fsLA-MC-ICP-MS法。     

利用树轮宽度重建近280 a来祁连山东部地区的春季降水

利用采自祁连山东部的祁连圆柏样芯样本，建立标准化年表，并将标准年表的树轮指数与附近的乌鞘岭气象站的温度和降水进行相关分析，结果表明，年轮指数与3－4月降水呈显著正相关，相关系数为0．525，利用标准化年表与3－4月降水的线性回归方程重建了研究区近280a来的3－4月降水，统计检验表明重建结果是可靠的。     

交叉定年技术及其在高分辨率年代学中的应用

高分辨率年代学标尺是高分辨率过去环境变化的研究基础。树轮年代学中的交叉定年技术是一种较为成熟的高分辨率年代学研究方法 ,其技术的核心是找到一个受共同的环境限制因子控制的可量化指标 (如树轮宽度 ) ,通过一定数量的样本进行交叉比较 ,来得到一个高分辨率的年代学序列。该技术中一些有益的概念和方法可以推广应用于其它高分辨率过去环境变化的研究中 ,文中通过对树轮年代学中的交叉定年技术原理的研究 ,剖析交叉定年技术的方法及其核心技术内涵 ,为该技术的扩展应用提供内在的科学依据 ,并对其应用前景进行探讨。     

Stable isotope coherence in the earlywood and latewood of tree-line conifers

Annually resolved and replicated tree-ring stable isotope series have the potential to reconstruct growing season environmental parameters over multi-millennial timescales. As this archive may require only minimal statistical detrending, it has the potential to preserve a large portion of low frequency climate signals. To date, many studies have utilised only the latewood portion of the tree ring, in an attempt to minimize carry-over effects from previous year reserves and maximise the annual nature of the climate signal preserved. However, the old trees from tree-line locations, necessary to build long chronologies, often display narrow ring-widths (< 0.5 mm), making accurate earlywood–latewood separation difficult and particular time consuming. The resulting samples may also be too small for efficient cellulose purification or multiple isotopic determinations. As photosynthates from the current year are predominantly used in conifer ring formation at marginal sites with short growing seasons, latewood separation may not be especially advantageous in determining a useful climate signal and therefore unnecessary where resources are limited. To test this hypothesis, Scots pine from Northern Norway and European larch from the Swiss Alps are used. Both sites are tree-line locations where growth is predominantly temperature limited. Tree rings were cut and extracted to cellulose for both the earlywood and latewood of each annual growth ring and stable carbon isotope ratios were measured. Our results demonstrate a very high common carbon isotope signal between earlywood and latewood in both species (r_larch = 0.68 and r_pine = 0.79), which also show high correlations with summer temperature over the investigated period (AD 1980–2004 for larch and AD 1929–1978 for pine). High turnover rates and small reserve pools at these tree-line locations may account for these high common signals. These results suggest that for European tree-line conifers, the separation of earlywood from latewood is unnecessary to resolve an annual isotopic signal and make a reliable climate calibration. Using the whole ring may provide additional analytical advantages and consequently even improve climate calibrations.     

Holocene peatland development and hydrological variability inferred from bog‐pine dendrochronology and peat stratigraphy – a case study from southern Sweden

Dendrochronological analysis was applied to subfossil remains of Scots pine (Pinus sylvestris L.) buried in a South Swedish peat deposit. In combination with peat stratigraphy, this approach was explored for its potential to provide information on the local hydrological and depositional history at the site, forming the basis for a regional palaeohydrological analysis. A 726‐year ring‐width chronology was developed and assigned an absolute age of 7233–6508 cal a BP (5284–4559 BC) through cross‐dating with German bog‐pine chronologies, whereas two short additional records of older ages were radiocarbon dated. Registration of growth positions of individual trees allowed assessment of the spatial dynamics of the pine population in response to hydrological changes and peatland ontogeny. Annually resolved growth variability patterns in the pine population reveal several establishment and degeneration phases, probably reflecting fluctuations in bog‐surface wetness. A major establishment phase at 7200–6900 cal a BP reflects the onset of a period of lowered groundwater level, also indicated by increased peat humification, and a development consistent with regional temperature and lake level reconstructions revealed from other proxies. This study demonstrates that subfossil bog‐pine populations may provide annually to decadally resolved reconstructions of local groundwater variability, which are highly relevant in a long‐term palaeoclimatic context. Copyright © 2012 John Wiley & Sons, Ltd.     

树轮年代学的若干进展

树轮年代学是一门研究树木木质部年生长层，以及利用年生长层来定年的科学。由于树轮不仅是一种定年工具，它本身还可提供树轮生成时的环境要素信息，为一种环境变化的代用资料。在全球变化特别是在过去全球气候变化研究中，树轮年代学受到愈来愈广泛的重视，在近期内取得了长足的、惊人的进展。本文仅在树轮长年表的建立，树轮年代学生物基础研究──模式研究，利用树轮对环境要素变化的研究，以及树轮的图像分析等几个与环境变化研究相关的方面和本学科目前研究热点的若干进展，予以概要的论述。     

树轮氢、氧同位素研究进展

总结了树轮氢氧同位素的分馏原理及其时间序列和空间变化与气候变迁之间的关系。研究表明,树轮氢氧同位素组成的变异反映了源水同位素组成、温度、相对湿度和降水量的变化。同时,对今后树轮同位素的发展方向作了展望。     

Zircon U‐Pb/Lu‐Hf and monazite chemical dating of the Tirodi biotite gneiss: implication for latest Palaeoproterozoic to Early Mesoproterozoic orogenesis in the Central Indian Tectonic Zone

In this investigation, we reconstruct the latest Palaeoproterozoic to Early Mesoproterozoic orogenic events along the southern margin of the Central Indian Tectonic Zone (CITZ), using sensitive high resolution ion microprobe (SHRIMP) U‐Pb zircon dating and Lu‐Hf isotope analyses of zircon and Th‐U‐Pb chemical dating of monazite from samples of the Tirodi biotite gneiss (TBG) unit in the Sausar Mobile Belt (SMB), the latter constituting the southernmost litho‐tectonic component of the CITZ. U‐Pb zircon dating of one migmatitic gneiss sample from the type locality of the Tirodi biotite gneiss in the northern domain of the SMB has yielded an age of 1618 ± 8 Ma, which is considered to be the time of magmatic crystallization of its protolith. Combined U‐Pb zircon and monazite chemical dating of two granite gneiss samples from the southern domain of the SMB broadly constrain magmatic crystallization between 1603 ± 23 Ma and 1584 ± 17 Ma and an overprinting metamorphic recrystallization event at 1572 ± 7 Ma. Monazites from the granite gneiss samples also record a terminal metamorphic event at 1415 ± 23 Ma. Lu‐Hf isotopic analyses of zircons reveal fundamentally different source rock reservoirs for the protoliths of these magmatic rocks across the SMB. While the type TBG from the northern domain was derived from an Early Palaeoproterozoic source T(Hf) from 2093 to 2523 Ma, with a mean value at 2379 Ma) of essentially juvenile material with minor crustal components (εHf(t) from −3.3 to + 3.7), the granite from the southern domain had a mature crustal source (εHf(t) from −12.5 to −21.9) of Palaeoarchaean age T(Hf) from 3051 to 3630 Ma, with a mean value at 3218 Ma). When integrated with metamorphic information previously obtained from the 1.6 Ga ultra‐high temperature granulite facies metamorphic event in the SMB, the discrete magmatic and metamorphic events between 1.62/1.60 Ga and 1.42 Ga can be correlated with the formation of an Early Mesoproterozoic accretionary orogen in the CITZ. Copyright © 2011 John Wiley & Sons, Ltd.     

Accurate and High‐Precision Determination of Boron Isotopic Ratios at Low Concentration by MC‐ICP‐MS (Neptune)

We report an approach for the accurate and reproducible measurement of boron isotope ratios in natural waters using an MC‐ICP‐MS (Neptune) after wet chemistry sample purification. The sample matrix can induce a drastic shift in the isotopic ratio by changing the mass bias. It is shown that, if no purification is carried out, the direct measurement of a seawater diluted one hundred times will induce an offset of ?7‰ in the isotopic ratio, and that, for the same concentration, the greater the atomic mass of the matrix element, the greater the bias induced. Whatever the sample, it is thus necessary to remove the matrix. We propose a method adapted to water samples allowing purification of 100 ng of boron with a direct recovery of boron in 2 ml of 3% v/v HNO₃, which was our working solution. Boron from the International Atomic Energy Agency IAEA‐B1 seawater reference material and from the two groundwater reference materials IAEA‐B2 and IAEA‐B3, was chemically purified, as well as boron from the certified reference material NIST SRM 951 as a test. The reproducibility of the whole procedure (wet chemistry and MC‐ICP‐MS measurement) was ± 0.4‰ (2s). Accuracy was verified by comparison with positive‐TIMS values and with recommended values. Seawater, being homogeneous for boron isotope ratios, is presently the only natural water material that is commonly analysed for testing accuracy worldwide. We propose that the three IAEA natural waters could be used as reference samples for boron isotopes, allowing a better knowledge of their isotopic ratios, thus contributing to the certification of methods and improving the quality of the boron isotopic ratio measurements for all laboratories.     

Long‐term spruce budworm outbreak dynamics reconstructed from subfossil trees

We reconstructed the long‐term spruce budworm (SBW) (Choristoneura fumiferana Clem.) outbreak dynamics in the boreal forest of Quebec (Canada) using a dendrochronological approach with subfossil trees. Although the majority of the excavated wood belonging to the genus Picea could potentially reveal the past activity of spruce budworms in the tree rings, very few were cross‐dated due to a lack of marker rings. All cross‐dated trees were found within a particular zone of the peat bogs and the floating chronology was radiocarbon dated to ca. 5.1 cal ka BP. The results presented in this study suggest that the dynamics of SBW outbreaks in the studied area fluctuated during the last millennia and that severe outbreaks as observed during the 20th century seldom occurred in that part of the boreal forest since the end of the last glaciation. These results are in agreement with observations from other parts of eastern North America. Copyright © 2011 John Wiley & Sons, Ltd.