Tree-ring Measurements Research Articles

Five centuries of Southern Moravian drought variations revealed from living and historic tree rings

Past, present, and projected fluctuations of the hydrological cycle, associated to anthropogenic climate change, describe a pending challenge for natural ecosystems and human civilizations. Here, we compile and analyze long meteorological records from Brno, Czech Republic and nearby tree-ring measurements of living and historic firs from Southern Moravia. This unique paleoclimatic compilation together with innovative reconstruction methods and error estimates allows regional-scale May–June drought variability to be estimated back to ad 1500. Driest and wettest conditions occurred in 1653 and 1713, respectively. The ten wettest decades are evenly distributed throughout time, whereas the driest episodes occurred in the seventeenth century and from the 1840s onward. Discussion emphasizes agreement between the new reconstruction and documentary evidence, and stresses possible sources of reconstruction uncertainty including station inhomogeneity, limited frequency preservation, reduced climate sensitivity, and large-scale constraints.

224 耐暑ラット (FOK) における耐寒性の改善

In southwestern Hokkaido, volcanic activities were high during historical times. For examination of their effects on forest ecosystem, we conducted preliminary survey using a dendroecological technique. Tree-ring samples were collected mainly in the southern part of the Ishikari Lowland where some layers of pyroclastic fall were found. The number of tree-rings was counted and tree-ring widths were measured. As a result, we could distinguish from the 1739 tree ring measurements the effect of eruption with its subsequent Ta-a volcanic deposition. This proves that the effect on tree growth changed in proportion to distance from the origin of the pyroclastic fall.

The Value of Multiproxy Reconstruction of Past Climate

Understanding the dynamics of climate change in its full richness requires the knowledge of long temperature time series. Although long-term, widely distributed temperature observations are not available, there are other forms of data, known as climate proxies, that can have a statistical relationship with temperatures and have been used to infer temperatures in the past before direct measurements. We propose a Bayesian hierarchical model to reconstruct past temperatures that integrates information from different sources, such as proxies with different temporal resolution and forcings acting as the external drivers of large scale temperature evolution. Additionally, this method allows us to quantify the uncertainty of the reconstruction in a rigorous manner. The reconstruction method is assessed, using a global climate model as the true climate system and with synthetic proxy data derived from the simulation. The target is to reconstruct Northern Hemisphere temperature from proxies that mimic the sampling and errors from tree ring measurements, pollen indices, and borehole temperatures. The forcing series used as covariates are solar irradiance, volcanic aerosols, and greenhouse gas concentrations. The Bayesian model was successful in integrating these different sources of information in creating a coherent reconstruction. Within the context of this numerical testbed, a statistical process model that includes the external forcings can improve the quality of a hemispheric reconstruction when long time scale proxy information is not available. This article has supplementary material online.

Technique to Improve Visualization of Elusive Tree-Ring Boundaries in Aspen (Populus tremuloides)

A simple, quick, and inexpensive technique to improve visualization of aspen (Populus tremuloides) tree rings under the microscope, the ‘shadow technique’, is described. The technique assumes appropriate preparation of increment cores or cross-sections and works well on the lighter portions of the sample with fungus- and bacteria-free wood. The shadow technique was used successfully to elucidate tree-ring boundaries in small diameter (<5 cm DBH) aspen from northern Utah that commonly had >100 annual rings. Crossdating verified whether the elusive rings were missing or false rings. Aspen tree-ring measurement will be greatly enhanced with the shadow technique and preliminary investigation suggests it could be used on other species such as curlleaf mountain mahogany (Cercocarpus ledifolius).

Wood density and its radial variation in six canopy tree species differing in shade-tolerance in western Thailand

Background and AimsWood density is a key variable for understanding life history strategies in tropical trees. Differences in wood density and its radial variation were related to the shade-tolerance of six canopy tree species in seasonally dry tropical forest in Thailand. In addition, using tree ring measurements, the influence of tree size, age and annual increment on radial density gradients was analysed.MethodsWood density was determined from tree cores using X-ray densitometry. X-ray films were digitized and images were measured, resulting in a continuous density profile for each sample. Mixed models were then developed to analyse differences in average wood density and in radial gradients in density among the six tree species, as well as the effects of tree age, size and annual increment on radial increases in Melia azedarach.Key ResultsAverage wood density generally reflected differences in shade-tolerance, varying by nearly a factor of two. Radial gradients occurred in all species, ranging from an increase of (approx. 70%) in the shade-intolerant Melia azedarach to a decrease of approx. 13% in the shade-tolerant Neolitsea obtusifolia, but the slopes of radial gradients were generally unrelated to shade-tolerance. For Melia azedarach, radial increases were most-parsimoniously explained by log-transformed tree age and annual increment rather than by tree size.ConclusionsThe results indicate that average wood density generally reflects differences in shade-tolerance in seasonally dry tropical forests; however, inferences based on wood density alone are potentially misleading for species with complex life histories. In addition, the findings suggest that a ‘whole-tree’ view of life history and biomechanics is important for understanding patterns of radial variation in wood density. Finally, accounting for wood density gradients is likely to improve the accuracy of estimates of stem biomass and carbon in tropical trees.

Canopy tree growth responses following selection harvest in seven species varying in shade tolerance

We used tree ring measurements to investigate the temporal response of basal area increment (BAI) of canopy trees following selection harvests by sampling across a chronosequence of stands with known harvest dates in tolerant hardwood (Great Lakes – St. Lawrence) stands in central Ontario. Seven tree species of various shade tolerances ranged widely in their responses to reduced competition. The more shade-tolerant species responded more positively: shade-tolerant species showed an average increase in BAI of 35% 4–15 years postharvest compared with 16% for mid-tolerant species and –7.5% for intolerant species. All species showed a time-lag in postharvest growth responses, with maximum growth responses occurring between 3 and 15 years postharvest. Tree size was the most important factor determining the magnitude of BAI response, with smaller trees consistently responding more than larger trees. We suggest that higher growth responses to selection harvests among shade-tolerant species may contribute to declines in mid-tolerant species abundance in selection-managed stands. More broadly, interspecific variability in canopy tree responses to forest disturbance appears to follow patterns distinct from seedling and sapling responses, with important implications to forest community dynamics in both managed and unmanaged forests.

Tree-Ring Dating Of Old-Growth Longleaf Pine (Pinus palustris Mill.) Logs From An Exposed Timber Crib Dam, Hope Mills, North Carolina, U.S.A

On 26 May 2003, intense rainfall from a series of thunderstorms in eastern North Carolina caused flooding that eventually destroyed the concrete dam in Hope Mills, draining Hope Mills Lake, and revealing a formerly submerged and buried structure that was identified as a timber crib dam. Inspection revealed these logs to be old-growth longleaf pines, which are now rare on the coastal plain landscape. Our primary objective was to develop a new multi-century longleaf pine tree-ring chronology by crossdating the tree rings from sections extracted from logs in the crib dam with an anchored tree-ring chronology created from nearby living longleaf pine trees. We also examined the climatic response in the longleaf pine trees to evaluate their potential for reconstructing climate. Using tree-ring measurements obtained from old-growth longleaf pines found at a nearby church, we were able to date the rings on 21 series representing 14 logs from the crib dam, spanning the years 1597 to 1825. Distorted sapwood in many of the logs prevented us from finding absolute cutting dates and lessened the strength of correlation during the period of overlap between the church series and crib dam series. Human disturbances, specifically related to the naval stores industry, likely influenced the growth-ring patterns of the crib dam pine samples, as well. Correlation analyses between the longleaf pine chronology and temperature, precipitation, Palmer Drought Severity Indices, and North Atlantic sea surface temperatures showed a significant response to cool and wet spring months.

Stand growth model using volume increment/basal area ratios

Estimation of stand growth is crucial for forest planning. Estimations were usually done using fixed values, and recently growth equations have been used. An alternative is through stand growth models. The objective was to develop a simple model for&lt;I&gt; Nothofagus pumilio&lt;/I&gt; stands with full density along site quality and age gradients. The sample was obtained from 125 stands. Data on forest structure and samples for tree-ring measurement were taken in all trees to estimate growths using biometric models previously developed. The growth values of each plot during the last twenty years were calculated to fit the model, using the ratio of total volume increment/basal area as an independent variable. The developed model gives a ratio between stand volume increment and basal area (m/year) in relation to the site quality and stand age. The statistics (&lt;I&gt;r&lt;/I&gt;&lt;sup&gt;2&lt;/sup&gt; = 0.819, mean error = 0.019, absolute mean error = 0.033), residual analysis and biological performance were satisfactory. The obtained stand growths varied between 1 and 20 m&lt;sup&gt;3&lt;/sup&gt;/ha/year. This simple model allowed to estimate growth values at a stand level from easy field measurements from forest inventories.

14C Measurements of Tree Rings of a Japanese Cedar During 1945 to 2000 and Core Sampling for Environmental Studies

Japanese cedar rings sampled from Aomori Prefecture, Japan, were measured to obtain tree-ring radiocarbon data covering a period of the latter half of the 20th century in the northernmost area of Honshu (mainland Japan), to obtain records of variation in atmospheric 14C concentration caused by past atmospheric nuclear testing, and to study any possible local effects. This work, carried out on a partial disk, was also intended to provide a reference for data obtained by core sampling of live, standing Japanese black pines as a part of marine environmental studies.

Nondestructive tree-ring measurements for Japanese oak and Japanese beech using micro-focus X-ray computed tomography

The purpose of this study is to establish technology for utilizing images taken by micro-focus X-ray computed tomography (CT) to perform nondestructive tree-ring measurement of wooden cultural properties. This paper covers two experiments conducted using Japanese oak as a typical example of ring-porous wood and Japanese beech as a representative example of diffuse-porous wood. In the first experiment, images of thin strip specimens of Japanese oak and Japanese beech taken by micro-focus X-ray CT are compared against those taken by soft X-ray radiography, the method conventionally used in dendrodensitometry. A discussion then follows in regard to image quality and tree-ring width measurement resulting from the two methods. In the second experiment, tomograms are taken of folk art articles made of Japanese oak and Japanese beech, demonstrating that it is possible to use nondestructive means to visualize the tree-rings of three-dimensional objects. The results show that micro-focus X-ray CT offers much promise of widespread utilization in the tree-ring dating of wooden cultural properties.

Tropical Cyclone Signals within Tree-Ring Chronologies from Weeks Bay National Estuary and Research Reserve, Alabama

This study investigates the relationship between tropical cyclones and tree-ring chronologies within a bottomland forest in coastal Alabama. Tree cores were collected from 36 slash pines in the Swift Track area of the Weeks Bay National Estuary and Research Reserve, Fairhope, Alabama. Tree cores were processed, measured to the nearest 0.01 mm, and cross-dated using standard procedures. A standardized ring index series was computed from the tree-ring measurement for each year from 1890 to 2000. The index series represents a single chronology of the entire forest stand, which we refer to as the stand-scale. An initial comparison of index series values to years of known tropical storm and hurricane strikes within the Weeks Bay area reveals no clear tropical cyclone signal. Statistical tests of the index values for 2–7 y periods before and after tropical storms and hurricanes indicate no statistically significant difference in tree-rings before and after the storms. In contrast, standardized index values computed for each individual tree-ring series (individual tree-scale) display more rapid growth (release) in years following direct hits by tropical cyclones. Individual tree-ring data also indicate slowed growth (suppression) during years when tropical cyclones are infrequent. These results indicate that researchers must be aware of scale of analysis when researching tree-ring chronologies in Gulf Coast forests. For this study, a combination of the two scales of analysis results in a recognizable tree-ring record of suppression and then release generated by tropical cyclones.

Spruce beetle outbreaks on the Kenai Peninsula, Alaska, and Kluane National Park and Reserve, Yukon Territory: Relationship to summer temperatures and regional differences in disturbance regimes

When spruce beetles ( Dendroctonus rufipennis) thin a forest canopy, surviving trees grow more rapidly for decades until the canopy closes and growth is suppressed through competition. We used measurements of tree rings to detect such growth releases and reconstruct the history of spruce beetle outbreaks at 23 mature spruce ( Picea spp.) forests on and near the Kenai Peninsula, Alaska and four mature white spruce ( Picea glauca) forests in Kluane National Park and Reserve, Yukon Territory. On the Kenai Peninsula, all stands showed evidence of 1–5 thinning events with thinning occurring across several stands during the 1810s, 1850s, 1870–1880s, 1910s, and 1970–1980s, which we interpreted as regional spruce beetle outbreaks. However, in the Kluane region we only found evidence of substantial thinning in one stand from 1934 to 1942 and thinning was only detected across stands during this same time period. Over the last 250 years, spruce beetle outbreaks therefore occurred commonly among spruce forests on the Kenai Peninsula, at a mean return interval of 52 years, and rarely among spruce forests in the Kluane region where cold winter temperatures and fire appear to more strongly regulate spruce beetle population size. The massive 1990s outbreaks witnessed in both regions appeared to be related to extremely high summer temperatures. Recent outbreaks on the Kenai Peninsula (1971–1996) were positively associated with the 5-year backwards running average of summer temperature. We suggest that warm temperature influences spruce beetle population size through a combination of increased overwinter survival, a doubling of the maturation rate from 2 years to 1 year, and regional drought-induced stress of mature host trees. However, this relationship decoupled after 1996, presumably because spruce beetles had killed most of the susceptible mature spruce in the region. Thus sufficient numbers of mature spruce are needed in order for warm summer temperatures to trigger outbreaks on a regional scale. Following the sequential and large outbreaks of the 1850s, 1870–1880s, and 1910s, spruce beetle outbreaks did not occur widely again until the 1970s. This suggests that it may take decades before spruce forests on the Kenai Peninsula mature following the 1990s outbreak and again become susceptible to another large spruce beetle outbreak. However, if the recent warming trend continues, endemic levels of spruce beetles will likely be high enough to perennially thin the forests as soon as the trees reach susceptible size.

A comparison of ring-width and event-year chronologies derived from white oak ( Quercus alba) and northern red oak ( Quercus rubra), southwestern Quebec, Canada

In dendrochronology, ring width has been a variable of choice when assessing the radial growth–climate association of tree species. We compared ring-width and event-year chronologies from a dendroclimatic perspective using both white oak ( Quercus alba L.) and northern red oak ( Quercus rubra L.). The study was conducted in three regions of the Ottawa valley in southern Québec. Twelve mixed red and white oak stands were selected and for each oak species, 12 chronologies were developed from tree-ring measurement and 12 others were derived using visual assessment of narrow or wide rings (event years). Ring-width and event-year chronologies gave almost identical results and revealed the prevalence of drought in the early growing season as the most influential factor in both species. This study emphasizes the utility of event-year chronologies in tree-ring studies and their comparativeness with ring width. Establishing event-year chronologies has the advantage of being faster than measuring ring width, it does not necessitate complex equipment and depending on the purpose of the study may prove to be at least comparable. The choice of species, their mean sensitivity, the ability to recognize narrow or large rings as well as the number of trees and sites to analyze may, however, be factors to consider when choosing to use event-year chronologies over the more commonly used ring-width ones.

An interactive method for digital tree-ring width measurement

Presentamos un nuevo método interactivo para la determinación de la anchura de los anillos de los árboles. Se usa un escaner de la alta resolución y un microordenador en los que se trabaja con un programa para estudiar imágenes de anillos de árboles que se desarrolló dentro del ambiente Interactive Data Language (IDL 5.0). La ventaja principal de este método es que lleva a cabo un análisis de imágenes de anillos de árboles de manera interactiva sin necesitar equipo complejo y de alto costo. Se usó una prueba simple para verificar la precisión de las medidas de la anchura de los anillos de una muestra del árbol Pinus taeda del sur de Brasil.

Ravning-broens alder – En af Danmarks sikreste dendrokronologiske dateringer?

Ravning-broens alder – En af Danmarks sikreste dendrokronologiske dateringer?

Tree ring growth by core sampling at the CONECOFOR Permanent Monitoring Plots. The deciduous oak (Quercus cerris L.) type

Radial growth analysis evaluates the ability of trees to grow under different site and environmental conditions, thus contributing to bio-ecological studies aimed at increasing understanding of forest stand evolution. Tree ring growth is analysed in five Permanent Monitoring Plots (PMPs) dominated by Turkey oak (Quercus cerris L.). Common structural features of these PMPs are their origin (coppice forest) and their current physiognomy as stored coppice and transitory crop. A dendroecological approach was used to analyse past radial stem growth, the influence of silvicultural background and stand age, as well as to compare the growth rhythm of stands in different site-indexes and environmental conditions. Tree coring was carried out at the time of the first inventory (winter 1996/97) by sampling 8 to 11 dominant and co-dominant trees representative of the upper storey in the buffer area of each PMP. The basic stem and crown growth variables were measured for each tree sampled and two cores collected at 1.30 m. Annual ring width was determined by the Tree Ring Measurement System SMIL3 and the data were elaborated by the ANAFUS software. Site mean curves and growth trend per social class in each stand were defined both by visual comparison and statistical analysis among individual tree series. The main results were as follows: i) social differentiation becomes established earlier with better site indexes and higher tree densities; ii) sensitivity to external disturbances is higher and more defined in the dominant class than in the co-dominant tree layer; iii) competition cycles are clearly discernible and related to both stand density and site-index in young stands under natural evolution (stored coppices); iv) when silvicultural interventions were performed in the past is quite visible readable in the stands under conversion into high forest (transitory crops); v) the mean series per site are statistically related and common periods characterized by a similar growth trend have been recognized.

A non-invasive method for reconstructing the relative mortality rates of trees in mixed-age, mixed-species forests

The death of overstory trees drives changes throughout forest ecosystems. Knowledge of mortality rates for these larger trees provides a long-term perspective on forest development and forest health. Tree mortality rates are typically determined by repeated censusing of trees over extended time intervals. We describe a method of reconstructing relative mortality rates that does not require injuring live trees on the study plots. To determine when trees died, we used cross-dating (matching tree-ring patterns of dead and live trees), identification of sapling releases, and assessment of tree decomposition. Dead trees were identified to genus or sub-genus by microscopic examination of wood. We reconstructed live tree community structure so that mortality could be relativized on a taxonomic-group- and tree-size-specific basis by the tree densities existing when mortality occurred. We modified a forest development model to operate backwards in time and validated this model by comparing past tree stem diameters predicted by the model with past stem diameters known from tree-ring measurements. All tree-ring measurements from live trees were obtained off the study plots. We report data for all trees ≥20 cm diameter at breast height (DBH) from seven oak-hickory forest sites in Arkansas, Illinois, Indiana, and Ohio, USA. Total plot area was 6.7 ha. Mortality rates were determined for the past 20 years by genus or sub-genus, DBH, and decade. The average mortality rate was 0.60% per year. The accuracy of the reconstructed mortality rates approaches that of mortality rates obtained by repeated censusing. While this mortality reconstruction method does not yield data for individual species, and may involve some compromise in accuracy, the method offers substantial benefits: long-term mortality data may be obtained from a short-term study, mortality rates may be obtained for the past, and because this reconstruction method is non-invasive, future mortality rates can be measured on the same plots.

Black spruce decline triggered by spruce budworm at the southern limit of lichen woodland in eastern Canada

Black spruce (Picea mariana (Mill.) BSP) is the dominant tree species of the southernmost (48°N) lichen woodlands in eastern Canada. Most spruce trees in mature lichen woodlands appear to be declining, as shown by the massive invasion of the epiphytic lichen Bryoria on dead branches of dying trees. A dendroecological study was undertaken to identify the main causal factors of the decline. A decline index based on the abundance of Bryoria on spruce trees was used to distinguish healthy from damaged lichen–spruce woodlands and to select sampling sites for tree-ring measurements. Three conifer species (black spruce, balsam fir (Abies balsamea (L.) Mill.), and jack pine (Pinus banksiana Lamb.)) were sampled to compare their growth patterns in time and space. In the late 1970s and mid-1980s, black spruce and balsam fir experienced sharp and synchronous radial-growth reductions, a high frequency of incomplete and missing rings, and mass mortality likely caused by spruce budworm (Choristoneura fumiferana (Clem.)) defoliation. Jack pine, a non-host species, showed no such trend. Because black spruce layers were spared, lichen woodlands will eventually regenerate unless fire occurs in the following years. Black spruce decline can thus be considered as a normal stage in the natural dynamics of the southern lichen woodlands.

An investigation of lag identification tools for vector nonlinear time series

Exploratory methods for determining appropriate lagged vsrlables in a vector nonlinear time series model are investigated. The first is a multivariate extension of the R statistic considered by Granger and Lin (1994), which is based on an estimate of the mutual information criterion. The second method uses Kendall's ρ and partial ρ statistics for lag determination. The methods provide nonlinear analogues of the autocorrelation and partial autocorrelation matrices for a vector time series. Simulation studies indicate that the R statistic reliabiy identifies appropriate lagged nonlinear moving average terms in a vector time series, while Kendall's ρ and partial ρ statistics have some power in identifying appropirate lagged nonlinear moving average and autoregressive terms, respectively, when the nonlinear relationship between lagged variables is monotonic. For illustration, the methods are applied to set of annual temperature and tree ring measurements at Campito Mountain In California.

Tree rings as indicators of growth periodicity of acacias in the Rift Valley of Ethiopia

In many arid and semi-arid parts of Ethiopia, acacia trees are important for the rural economy. However, very little is known about the dynamics of the acacia woodlands. In this study, an attempt was made to find out whether or not tree rings in acacias can be used as indicators of growth periodicity. In such a case, growth and yield models could be developed from tree-ring measurements. The study was made in the central part of the Rift Valley of Ethiopia and included samples from both, naturally regenerated and planted acacias. Standard techniques from tree-ring research were employed to study the relationship between tree-ring patterns and different moisture-related climatic variables (e.g. moisture balance, precipitation). Also, the number of rings in trees with known age was counted. The results indicate that the acacias form one ring per rainy season (year) in the dry parts of this area. In a minor complementary study using X-ray densitometry, the wood density appeared to be correlated with moisture-related climatic variables. However, the technique appeared to be of very limited use for locating growth boundaries.