Dated Tree Rings Research Articles

Stable isotopic and chemical indicators of volcanic eruptions in tree rings from Parícutin, Mexico

Annual growth rings obtained from well dated tree ring cores from Parícutin, Mexico are examined for unique chemical signatures that reflect a known local volcanic eruption and its subsequent atmospheric and terrestrial inputs. Stable carbon isotopic profiles are combined with elemental analyses to construct a chemical profile before, during, and after the known eruptive years (1943-1952) when a cinder cone formed near the town of Parícutin. Data from this well documented eruption are combined with controls obtained from outside the ash fall zone. Carbon isotopes exhibit an enriched spike (~3‰) during the eruptive period followed by a subsequent return to baseline values. This in combination with other stable isotopic indicators and increases in phosphorus, sulfur, and possibly other elements, suggest a unique set of chemical inputs from the eruption. The analytical approach developed here potentially can be used to date unknown eruptions which in the past have often relied on the common dendrochronologic technique of tree ring width determination, or on historic human records. The former method can be somewhat subjective as changes in ring width can be attributed to multiple causes in addition to volcanically induced environmental stresses; the latter method is restricted to eruptions occurring in the last few thousand years. The quantitative approach of chemical analyses presented in this preliminary study can potentially be combined with standard dendrochronological and/or 14C dating to accurately identify eruption events and place them in an anthropologic context.

Climate response of cell characteristics in tree rings of Picea crassifolia

Abstract Dimensions of dated tree rings are an important tool of dendroclimatology. However, the relationships between climatic variables and cell diameter and cell wall thickness are not yet clearly elaborated. In the present article, year-to-year cell characteristics, ring width, and wood density of Picea crassifolia trees growing in northwestern China have been measured with high resolution by means of the instrument SilviScan-3. The response function analysis showed that climate explained 51% of the variation of cell radial diameter chronology, 48% of wood density, 40% of cell wall thickness, and 37% of ring width. Cell wall thickness and wood density responded significantly and positively to temperature, and the response to precipitation was negative, while the opposite was true for cell radial diameter and ring width. Cell wall thickness and wood density were pronounced (statistically significant) to temperature in September and precipitation in May and August. Cell radial diameter responded significantly to temperature in June and July, and precipitation, in August. For ring width, the temperature in July was important. Accordingly, cell characteristics are sensitive to climate, and the findings could be useful in the field of dendroclimatology.

Dendrochemistry of Multiple Releases of Chlorinated Solvents at a Former Industrial Site

Trees can take up and assimilate contaminants from the soil, subsurface, and groundwater. Contaminants in the transpiration stream can become bound or incorporated into the annual rings formed in trees of the temperate zones. The chemical analysis of precisely dated tree rings, called dendrochemistry, can be used to interpret past plant interactions with contaminants. This investigation demonstrates that dendrochemistry can be used to generate historical scenarios of past contamination of groundwater by chlorinated solvents at a site in Verl, Germany. Increment cores from trees at the Verl site were collected and analyzed by energy-dispersive X-ray fluorescence (EDXRF) line scanning. The EDXRF profiles showed four to six time periods where tree rings had anomalously high concentrations of chlorine (Cl) as an indicator of potential contamination by chlorinated solvents.

Distribution and trends of mercury in deciduous tree cores

The distribution of total mercury (THg) within common deciduous trees and the applicability of tree cores as biomonitors of historical environmental THg trends were assessed for both contaminated and reference sites around Kingston, Ontario. Samples were collected from Acer spp., Quercus spp. Populus spp. and Salix spp. Bark and wood THg concentrations were found to be highly correlated whereas soil and wood THg concentrations were not. There were no temporal relationships for THg in dated tree rings corresponding with any other known environmental Hg trends. The shoreline speciess, Populus and Salix spp., had the greatest bark and wood Hg concentrations reaching 18 ng/g, significantly higher than for inland trees Quercus and Acer spp. with maximum values of 7 and 1.2 ng/g for bark and wood respectively. While tree cores cannot be reliably used as temporal THg biomonitors, there is promise for tree species such as Populus spp and Salix spp as spatial indicators of local long-term Hg contamination.

Investigating the influence of sulphur dioxide (SO 2) on the stable isotope ratios (δ 13C and δ 18O) of tree rings

This study reports the influence of a 20th century pollution signal recorded in the δ 13C and δ 18O of absolutely dated tree rings from Quercus robur and Pinus sylvestris from southern England. We identify a correspondence between the inter-relationship and climate sensitivity of stable isotope series that appears to be linked to recent trends in local SO 2 emissions. This effect is most clearly exhibited in the broadleaved trees studied but is also observed in the δ 13C values of the (less polluted) pine site at Windsor. The SO 2 induced stomatal closure leads to a maximum increase of 2.5‰ in the isotope values (δ 13C). The combined physiological response to high pollution levels is less in δ 18O than δ 13C. The SO 2 signal also seems to be present as a period of reduced growth in the two ring-width chronologies. Direct, quantitative correction for the SO 2 effect represents a significant challenge owing to the nature of the records and likely local plant response to environmental pollution. Whilst it appears that this signal is both limited to the late industrial period and demonstrates a recovery in line with improvements in air quality, the role of atmospheric pollution during the calibration period should not be underestimated and adequate consideration needs to be taken when calibrating biological environmental proxies in order to avoid development of biased reconstructions.

L'apport des séries dendrochronologiques françaises au prolongement de la chronologie européenne absolue et à la calibration du radiocarbone

Absolutely dated tree ring chronologies have been used to establish a high precision radiocarbon data set. That serves as a backbone for the absolute calibration of the radiocarbon time-scale back to 12594 cal BP (Schaub et al., 2008 a). Lateglacial floating tree ring chronologies exist but a gap still remains between them and the absolute European chronology. The challenge is to link absolute and Lateglacial chronologies, overcoming uncertainties due to changes in the reservoir age of marine data used for the radiocarbon calibration before the onset of the Holocene. In this paper (1) we will give the actual 'state of the art 'of existing absolutely dated tree-ring chronology and floating tree-ring chronologies of the LateGlacial and (2) we will present potential revealed by floating chronologies (Pinus silvestris,) from Southern French Alps. The French Lateglacial floating chronologies are dated to Bôlling-Allerôd and to onset of Younger Dryas. By means of wiggle-matching method, these new tree-ring based I4C records bridge the gap between European tree-ring based radiocarbon dating series.

Dendrochronological Investigation on Castanea Sativa Mill. in Belasitza Mountain and Western Balkans (Berkovitza Mountain)

ABSTRACTChestnut blight, or chestnut bark disease, is caused by an introduced fungus, Cryphonectria parasitica (Murrill) Barr, (formerly Endothia parasitica [Murrill] Anderson & Anderson). The fungus have been suggested in several studies to be a main factor to the problem of chestnut decline in Europe. Nevertheless, it is interesting to make a more detailed analysis of the factors which can influence chestnut health. Dendrochronology is the science of extracting ecological information from dated tree rings. Information about environmental occurrences or changes is documented in a tree in various ways. To further the understanding of the dendrochronological characteristics that are important for dating purposes this poster discusses an investigation based on dendrochronological assessment of living chestnut trees. The analysis was performed by the crossdating of chestnut chronologies of different provenances (Belasitza mountain and Western Balkans-Berkovitza mountain), and the interspecific synchronization with oak stands.

Use of Dendrochronology and Dendrochemistry in Environmental Forensics: Does It Meet the Daubert Criteria?

Dendrochronological methods have been in use for more than 100 years, providing us a record of climate, human activities (archaeology), floods, fire, mudslides and other geological and biological events. More recently, dendrochemisty has been used to assess the time frames of the onset and existence of environmental contamination. This article assesses the scientific status of dendrochronology and dendrochemistry with respect to the admissibility of expert testimony and Daubert legal criteria. The purpose of this article is to identify the crucial scientific aspects of dendrochronology and dendrochemistry that address the Daubert criteria and Rule 702 as amended in 2000. To clarify terminology, dendrochronology is the precise and reliable assignment of the year of formation of tree rings. Dendroecology is the use of dendrochronology to understand ecological and environmental processes (Schweingruber, 1996). Dendrochemistry is a subdiscipline of dendrochronology that analyzes and interprets the wood chemistry of precisely dated tree rings. Forensic dendrochemistry applies dendrochemistry to resolve environmental disputes and generally deal with questions regarding the timing and/or the source of environmental incidents. One significant application of forensic dendrochemistry to expert testimony is to address issues of anthropogenic contamination. Forensic dendroecology is a similar term to forensic dendrochemistry, but forensic dendrochemistry will be used in this discussion as the latter term emphasizes the use of chemical detection methods. Because dendrochemistry is based on the foundation of dendrochronology, both the former specialty and the latter broader discipline will be discussed.

Compton suppression system at Penn State Radiation Science and Engineering Center

A Compton suppression system is used to reduce the contribution of scattered gamma-rays that originate within the HPGe detector to the gamma-ray spectrum. The HPGe detector is surrounded by an assembly of guard detectors, usually NaI(T1). The HPGe and NaI(T1) detectors are operated in anti-coincidence mode. The NaI(T1) guard detector detects the photons that Compton scatter within, and subsequently escape from the HPGe detector. Since these photons are correlated with the partial energy deposition within the detector, much of the resulting Compton continuum can be subtracted from the spectrum reducing the unwanted background in gamma-ray spectra. A commercially available Compton suppression spectrometer (CSS) was purchased from Canberra Industries and tested at the Radiation Science and Engineering Center at Penn State University. The PSU-CSS includes a reverse bias HPGe detector, four annulus NaI(T1) detectors, a NaI(T1) plug detector, detector shields, data acquisition electronics, and a data processing computer. The HPGe detector is n-type with 54% relative efficiency. The guard detectors form an annulus with 9-inch diameter and 9-inch height, and have a plug detector that goes into/out of the annulus with the help of a special lift apparatus to raise/lower. The detector assembly is placed in a shielding cave. State-of-the-art electronics and software are used. The system was tested using standard sources, neutron activated NIST SRM sample and Dendrochronologically Dated Tree Ring samples. The PSU-CSS dramatically improved the peak-to-Compton ratio, up to 1000:1 for the 137Cs source.

Causes and timing of the 8200 yr BP event inferred from the comparison of the GRIP 10Be and the tree ring Δ 14C record

We analyse the 8200 yr BP cold event by comparing the high-resolution 10Be record from the GRIP ice core from Central Greenland with the well-known tree ring Δ 14 C record. By transferring the absolute dated tree ring chronology to the ice core time scale, we show that the coldest phase in the GRIP record occurred around 8150 yr BP. Furthermore, this method allows us to disentangle production and climate effects on 10Be and 14C with important implications for the reconstruction of past solar activity, and changes in the carbon cycle and 10Be transport. We show that, in principle, it is possible to infer changes in ocean circulation by comparing 10Be and 14C records. However, the duration of the 8200 yr BP event is too short to assign unambiguously a significant change in atmospheric 14C concentration to changes in the global ocean circulation. Based on the comparison of 10Be with climate records, one could argue that the 8200 yr BP cold event is triggered by a change towards lower solar activity. However, this link is questioned by the fact that around this period there are other similar and even stronger changes in solar activity that have no apparent connection to climate changes.

Suitability of chestnut earlywood vessel chronologies for ecological studies.

• Wood anatomical features measured in dated tree rings have often proven to be of ecological value. However, little is known about the suitability and power of such measurements studied in a year-to-year basis as is done in dendrochronology. • The present work is based on a comparative analysis of 60 dated time-series of earlywood features of chestnut (Castanea sativa) grown in the climatic context of the Southern part of the Swiss Alps. • It has been shown that the earlywood vessel area is a suitable ecological indicator. This variable, although not very sensitive, contains environmental information that is different from that stored in all other ring-width and earlywood features we considered. The vessel size is mainly related to the temperature during two physiologically crucial periods for vessel growth: the end of the previous vegetation period (during reserve storage) and the onset of cambial activity (during cell division and vessel differentiation). • Our work shows that the mean vessel size of the ring-porous chestnut contains ecophysiological information that can be used for research in dendrochronology.

Do volcanic eruptions enhance or diminish net primary production? Evidence from tree rings

Low growth rates of atmospheric CO2 were observed following the 1991 Pinatubo (Luzon) volcanic eruption. One hypothesis for this CO2 anomaly is that since diffuse light is more efficiently used by forests than direct light, the increase in the diffuse fraction of sunlight due to scattering by volcanic sulfur aerosol in the years following the eruption substantially increased forest net primary production (NPP). However, other observations suggest a decrease in northern forest NPP because of the cooler conditions following the eruption. Here we used a global database of dated tree ring widths (which correlate with forest NPP) to test this hypothesis. Ice core records of sulfur deposition allowed us to identify the timing and magnitude of 23 Pinatubo‐scale eruptions since 1000 CE. We found a significant decrease in ring width for trees in middle to high northern latitudes (north of 45°N) following eruption sulfur peaks. Decreases in tree ring widths were in the range of 2–8% and persisted for ∼8 years following sulfur peaks, with minima at around 4–6 years. Ring width changes at lower latitudes in the Northern Hemisphere (30°N to 45°N) and in the Southern Hemisphere (30°S to 56°S) were not significant. In the tropics (30°N to 30°S) the paucity of tree ring records did not permit the evaluation of NPP changes. Given that elevated aerosol levels and summer cooling last only ∼2–3 years after an eruption, the persistence of declines in northern tree growth for up to 8 years after eruptions implies some additional mechanism that links these shorter‐lived global eruption effects to sustained changes in tree physiology, biogeochemistry, or microclimate. At least for this sample of trees, the beneficial effect of aerosol light scattering appears to be entirely offset by the deleterious effect of eruption‐induced climate change.

Tracing the history of nuclear releases: determination of 129I in tree rings.

Concentrations of the long-lived radioisotope 1291 were measured in dated tree rings in order to determine whether the distribution of this isotope reflects the history of nuclear deposition. 129I concentrations and 129I/127I ratios were analyzed in tree rings and bark samples from four trees at West Valley, NY, and from one tree at Rochester, NY. West Valley was the site of short-lived nuclear fuel reprocessing activities (1966-1972), while Rochester, located 115 km to the northeast, provided a regional control site for the study. The selected trees reflect different modes of fluid and nutrient transport in trees, with three species of ring-porous trees (elm, oak, and locust), one semidiffuse (cherry), and one diffuse-porous tree (maple). The results show that 1291 levels in ring-porous trees, in which xylem or hydrologic tissue is localized in the outermost growth ring, are generally well correlated with the expected 1291 deposition pattern for the region. In contrast, tree rings of the more common semidiffuse to diffuse-porous wood, where xylem is disseminated throughout the trunk, show a less well developed 129I signal, probably due to the transport of iodine ions across annual rings. Iodine concentrations in the tree rings range from 0.04 to 2 mg/kg, 129I/127I ratios from 6 x 10(-10) to 3.8 x 10(-6). Tree bark and the outermost rings show significantly higher 129I concentrations than the wood of the trunk. The 129I/127I ratios for bark are very similar to values obtained for surface soil and water at the two localities, while inner rings have ratios similar to those in deeper layers of the soil, reflecting different pathways for 129I uptake and the differences in ambient 1291 levels between the atmosphere and deep soil. Although ring porous trees preserve the depositional pattern of nuclear releases, rings older than or close to the onset of the nuclear age have 129I/127I ratios significantly above the preanthropogenic level, suggesting that even in these trees some redistribution of 129I occurs throughout the trunk. Our results indicate that growth rings from ring-porous wood are useful in time-series analyses of regional 129I deposition, yielding reliable information on relative changes in 129I concentrations but requiring caution in the reconstruction of absolute ambient concentrations during any given time.

Network of tree-ring series in Estonia connected with north European chronologies

The present paper describes the course of building up the tree ring network of Scots pine (Pinus sylvestris L.) in Estonia. Although the construction timber in this region of the Baltic comes from two tree species, Scots pine and Norway spruce ( Picea abies Karst.), only the former was used for comparisons between the average tree ring series in Estonia and tree ring chronologies of Scots pine from other neighbouring areas: Sweden, Finland, Latvia and Poland. The dated tree ring series were compared using Student's t-criterion. It appeared that Estonian tree ring series of pine generally showed the greatest similarity with the chronology of Gotland pine in Sweden (the t-value with the average series of growing pines in north-western Estonia reaching 9.59). The similarities with other matched tree ring chronologies were also significant. It can be concluded that Estonia belongs together with other Baltic Sea countries to the same dendroclimatological region of uniform tree growth. This fact enables to use dated tree ring chronologies from the neighbouring areas to confirm the dating of tree ring sequences in Estonia.

INTCAL98 Radiocarbon Age Calibration, 24,000–0 cal BP

The focus of this paper is the conversion of radiocarbon ages to calibrated (cal) ages for the interval 24,000–0 cal BP (Before Present, 0 cal BP = AD 1950), based upon a sample set of dendrochronologically dated tree rings, uranium-thorium dated corals, and varve-counted marine sediment. The 14C age–cal age information, produced by many laboratories, is converted to Δ14C profiles and calibration curves, for the atmosphere as well as the oceans. We discuss offsets in measured l4C ages and the errors therein, regional 14C age differences, tree–coral 14C age comparisons and the time dependence of marine reservoir ages, and evaluate decadal vs. single-year 14C results. Changes in oceanic deepwater circulation, especially for the 16,000–11,000 cal BP interval, are reflected in the Δ14C values of INTCAL98.

Absolute Dating of the Last 7000 Years of the Vostok Ice Core Using 10Be

Ice cores have proven to be very valuable sources of palaeoclimatic information. Complete exploitation of this information requires reliable dating of the ice. In regions of relatively high ice accumulation, seasonal variations in several parameters (stable isotopes, conductivity, trace impurities, dust etc) have been used to obtain continuous year by year dating, at least in the upper portion of the core where these signals are still identifiable. Over large areas of the Antarctic plateau however, the accumulation rates are too low to record such yearly signals. In these cases chronologies have largely relied on modelling and/ or stratigraphic correlation with parameters assumed to be globally synchronous (for example volcanic horizons or methane trapped in bubbles in the ice). As has been previously pointed out, variation in cosmogenie 1~ can also been used for stratigraphie correlation (Raisbeck and Yiou, 1989). The cosmogenie production rate of l~ depends on (i) the primary cosmic ray intensity, (ii) the strength of the geomagnetic field, (iii) the level of solar magnetic activity. In the Antarctic, and over the time scales of interest here, this last parameter is likely the most important. However, independent of their origin, variations of 1~ production offer a globally synchronous and potentially very high resolution signal for stratigraphic correlation. In addition, if these variations can be correlated with those in an absolutely dated reservoir, they offer a way of obtaining absolute dating for the ice. We discuss such an application in the present paper. Using the Gif sur Yvette accelerator mass spectrometry facility, a nearly continuous profile of l~ concentrations with 0.5 m resolution has been measured in a 178 m ice core at Vostok station. On the basis of the EGT time scale (Jouzel et al, 1993), this depth corresponds to ~ 6700 years BP. This profile shows significant secular variations which are believed to be mainly the result of variable solar modulation. Assuming that the cosmogenic a4C production rate was proportionnal to the l~ concentrations on the EGT time scale, the l~ data have been used as input data in a carbon cycle model to simulate an atmospheric 14C record (Bard et al, 1997). This 14C record was then compared to the observed 14C profile in dendrochronologically dated tree rings. Differences between the simulated and observed 14C curves were then used to modify the assumed ice ages, and the process repeated iteratively to obtain a maximum in the correlation coefficient between the simulated and observed 14C curves. The resulting age for the Vostok core is older than the originally assumed EGT time scale by a gradually increasing amount which eventually reaches -400 years at 7000 BP.

Reconstruction of Tritium Release History from Contaminated Groundwater Using Tree Ring Analysis

The history of tritium releases to the groundwater from buried waste was reconstructed through dendrochronology. Wood from dated tree rings was sectioned from a cross-section of a tree that was thought to tap the groundwater. Cellulose was chemically separated from the wood. The cellulose was combusted and the water of combustion collected for liquid scintillation counting. The tritium concentration in the rings rose rapidly after 1972 which was prior to the first measurements made in this area. Trends in the tritium concentration of water outcropping to the surface are similar to the trends in tritium concentration in tree rings..

400 Year record of Δ14C in tree rings: The solar-activity cycle before, during and after maunder minimum and the longer cyclesin tree rings: The solar-activity cycle before, during and after maunder minimum and the longer cycles

The analysis of Δ14C in dated tree ring series from 1600 to 1940 AD is presented. The data series is divided into two parts, namely before and after 1780 AD to better study the characteristic of its cyclicities before, during and after the Maunder Minimum period. The data after 1780 AD show the presence of significant cyclical variations in the 10–12 year range, similar to the ones observed in other solar-activity index series. On longer time scales, only the «Gleissberg» cycle, which appears to modulate the 11 y cycle, seems to be significant. The origin of this last fluctuation in radiocarbon production is influenced by cosmic-ray intensity variations connected to long-term solar-wind flux variations. The analysis of Δ14C in two independent series of dated tree rings during 1564–1780 AD shows that there is an enhancement in radiocarbon level during the Maunder Minimum. Our data show that there are time variations of14C production rate even during the Maunder Minimum, as cosmic rays were modulated by the Sun in spite of the very low solar activity.

Stable isotopes in tree ring cellulose and climatic change

Relationships between the stable isotope contents ( δ 2 H, δ 13 C) in dendrochronologically dated tree rings of firs (Abies alba, Black Forest) and air temperature, relative humidity, as well as precipitation rate were investigated for the period 1959 to 1980. Only the late wood of each ring was used, since isotope data from early wood, grown during spring, does not unambiguously reflect the climate of the respective growth season. The δ 13 C-values, but not the δ 2 H-values show significant correlations with temperature, humidity, and precipitation. Based on this observation, δ 13 C-values were used to construct a paleoclimatic record for the past millenium. This required correction for anthropogenic 13 C -inputs since about 1850. The reconstructed temperatures are largely in agreement with presently-accepted variations in the recent past, whereby a “climatic optimum” appears during the Early Middle Ages with August temperatures about 0.5 °C higher than today. DOI: 10.1034/j.1600-0889.1991.t01-2-00005.x

Radiocarbon Activity Variation in Dated Tree Rings Grown in Mackenzie Delta

We measured the Δ14C values in 57 rings (from AD 1824 to 1880) of a white spruce grown in Mackenzie Delta (68°N, 130°W), as part of our continuing study of the Δ14C variation related to solar activities. The values exhibit a 10‰ fluctuation with an 11-year periodicity anti-correlated with the solar activity cycle. We also measured the Δ14C values in 6 rings (from AD 1940 to 1945). The abnormally high value in the 1943 ring may be due to two large solar flares occurring in 1942.