Changes In Ring Width Research Articles

Assessing earlywood-latewood proportion influence on tree-ring stable isotopes

Tree-ring stable isotopes are typically measured in latewood cellulose to mitigate potential carry-over effects from previous year storage pools. The isotopic composition of individual tree-ring segments is thought to include considerable intra-annual variability. This sampling strategy may be complicated by steep intra-annual isotope gradients that can rival the inter-annual variability, however. Consistent sampling of latewood material may not always be possible due to low sample availability or high prevalence of narrow rings or low amounts of latewood because of species-specific changes in ring width. Therefore, years that contain samples with higher portions of non-latewood (earlywood) material may influence the final chronology of isotopic variability. Here, we analyze the potential influence that changing earlywood and latewood components of individual tree rings can have on stable carbon and oxygen records from Quercus spp. and Pinus heldreichii chronologies. Analysis of stable isotopes in oak tree rings with varying amounts of latewood show no statistically significant differences in the range of isotopic composition, nor any major differences when considering the same calendric year. Similar results were found for the pine data, when comparing stable isotope measurements with earlywood-to-latewood ratio and maximum density. We argue that this simple approach should be applied to any long-term tree-ring stable isotope record in order to provide a better understanding of the potential biases that could arise from previously recorded intra-annual variability in the wood.

Growth and Wood Trait Relationships of Alnus glutinosa in Peatland Forest Stands With Contrasting Water Regimes.

Human-driven peatland drainage has occurred in Europe for centuries, causing habitat degradation and leading to the emission of greenhouse gases. As such, in the last decades, there has been an increase in policies aiming at restoring these habitats through rewetting. Alder (Alnus glutinosa L.) is a widespread species in temperate forest peatlands with a seemingly high waterlogging tolerance. Yet, little is known about its specific response in growth and wood traits relevant for tree functioning when dealing with changing water table levels. In this study, we investigated the effects of rewetting and extreme flooding on alder growth and wood traits in a peatland forest in northern Germany. We took increment cores from several trees at a drained and a rewetted stand and analyzed changes in ring width, wood density, and xylem anatomical traits related to the hydraulic functioning, growth, and mechanical support for the period 1994–2018. This period included both the rewetting action and an extreme flooding event. We additionally used climate-growth and climate-density correlations to identify the stand-specific responses to climatic conditions. Our results showed that alder growth declined after an extreme flooding in the rewetted stand, whereas the opposite occurred in the drained stand. These changes were accompanied by changes in wood traits related to growth (i.e., number of vessels), but not in wood density and hydraulic-related traits. We found poor climate-growth and climate-density correlations, indicating that water table fluctuations have a stronger effect than climate on alder growth. Our results show detrimental effects on the growth of sudden water table changes leading to permanent waterlogging, but little implications for its wood density and hydraulic architecture. Rewetting actions should thus account for the loss of carbon allocation into wood and ensure suitable conditions for alder growth in temperate peatland forests.

Axial changes in wood functional traits have limited net effects on stem biomass increment in European beech (Fagus sylvatica)

During the growing season, trees allocate photoassimilates to increase their aboveground woody biomass in the stem (ABIstem). This ‘carbon allocation’ to structural growth is a dynamic process influenced by internal and external (e.g., climatic) drivers. While radial variability in wood formation and its resulting structure have been intensively studied, their variability along tree stems and subsequent impacts on ABIstem remain poorly understood. We collected wood cores from mature trees within a fixed plot in a well-studied temperate Fagus sylvatica L. forest. For a subset of trees, we performed regular interval sampling along the stem to elucidate axial variability in ring width (RW) and wood density (ρ), and the resulting effects on tree- and plot-level ABIstem. Moreover, we measured wood anatomical traits to understand the anatomical basis of ρ and the coupling between changes in RW and ρ during drought. We found no significant axial variability in ρ because an increase in the vessel-to-fiber ratio with smaller RW compensated for vessel tapering towards the apex. By contrast, temporal variability in RW varied significantly along the stem axis, depending on the growing conditions. Drought caused a more severe growth decrease, and wetter summers caused a disproportionate growth increase at the stem base compared with the top. Discarding this axial variability resulted in a significant overestimation of tree-level ABIstem in wetter and cooler summers, but this bias was reduced to ~2% when scaling ABIstem to the plot level. These results suggest that F. sylvatica prioritizes structural carbon sinks close to the canopy when conditions are unfavorable. The different axial variability in RW and ρ thereby indicates some independence of the processes that drive volume growth and wood structure along the stem. This refines our knowledge of carbon allocation dynamics in temperate diffuse-porous species and contributes to reducing uncertainties in determining forest carbon fixation.

Growth rates of common urban trees in five cities in Great Britain: A dendrochronological evaluation with an emphasis on the impact of climate

The knowledge of the rate at which trees grow in urban areas is an important aspect to consider as it can influence our quantification and valuation of the ecosystem services provided by an urban forest. This study investigates growth variations in diameter and height for four common urban tree species (Acer pseudoplatanus, Betula pendula, Fraxinus excelsior and Quercus robur) across five cities in Great Britain (GB) and how the typical radial growth of two of those species (F. excelsior and Q. robur) changes with climate. Dendrochronology was used to identify tree age and changes in ring width and diameter at breast height (DBH) and tree height were measured in-situ at the time of coring. Results indicate a substantial variation in the mean annual growth rates and the relationships between DBH and age or height and age of each species across different cities. However, the multiple factors affecting tree growth seem to influence different species in different ways, with for example A. pseudoplatanus trees showing overall the fastest growth in Peterborough but B. pendula ones showing the slowest. Precipitation and temperature had an effect on radial growth of F. excelsior and Q. robur trees in GB, but the strength and direction of influence varied with time of year, species and city. In particular, low precipitation at the start or during the growing season was found to be a significant factor limiting radial growth. A trend towards a reduction in ring width increment was therefore identified in hot and dry years, primarily in south-eastern cities but in other cities too. This highlights the risk that a changing climate may have on the growth and, consequently, on the ecosystem service provision of healthy urban trees.

Revising midlatitude summer temperatures back to A.D. 600 based on a wood density network

AbstractAnnually resolved and millennium‐long reconstructions of large‐scale temperature variability are primarily composed of tree ring width (TRW) chronologies. Changes in ring width, however, have recently been shown to bias the ratio between low‐ and high‐frequency signals. To overcome limitations in capturing the full spectrum of past temperature variability, we present a network of 15 maximum latewood density (MXD) chronologies distributed across the Northern Hemisphere extratropics. Independent subsets of continental‐scale records consistently reveal high MXD before 1580 and after 1910, with below average values between these periods. Reconstructed extratropical summer temperatures reflect not only these long‐term trends but also distinct cooling pulses after large volcanic eruptions. In contrast to TRW‐dominated reconstructions, this MXD‐based record indicates a delayed onset of the Little Ice Age by almost two centuries. The reduced memory inherent in MXD is likely responsible for the rapid recovery from volcanic‐induced cooling in the fourteenth century and the continuation of warmer temperatures until ~1600.

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.

Response of anatomical structures in tree roots to an erosion event on the southeastern Tibetan Plateau

Exposed roots have been used in dendrogeomorphology to determine erosion rates. However, few studies have focused on the changes in ring width and in the anatomical properties of hardwood roots exposed by soil erosion at a macroscopic and microscopic level. In this study, we identified the ring width and the anatomical response of hardwood root to a denudation event and applied these anatomical findings to the reconstruction and quantification of soil erosion rates. A total of 136 cross sections (54 from buried roots and 79 from exposed roots of 25 trees) were sampled in the study area. Measurements of the widths of the growth rings, the average vessel area in earlywood, the average vessel area per ring, and the vessel number per ring were performed with WinDENDRO and ImageJ. Our results show that the analysis of vessel features is a useful tool to identify soil erosion events recorded during the life of a tree. A sharp decrease of nearly 50% in the vessel area of earlywood was an important signature indicating the exposure of tree roots caused by denudation. Soil erosion rates derived from exposed roots varied between 1.04 and 3.61mm y-1 in the southeastern Tibetan Plateau.

Historical Stand-Replacing Fire in Upper Montane Forests of the Madrean Sky Islands and Mogollon Plateau, Southwestern USA

The recent occurrence of large fires with a substantial stand-replacing component in the southwestern United States (e.g., Cerro Grande, 2000; Rodeo-Chedeski, 2002; Aspen, 2003; Horseshoe 2, Las Conchas, and Wallow, 2011) has raised questions about the historical role of stand-replacing fire in the region. We reconstructed fire dates and stand-replacing fire patch sizes using four lines of tree-ring evidence at four upper montane forest sites (>2600 m) in the Madrean Sky Islands and Mogollon Plateau of Arizona and New Mexico, USA. The four lines of tree-ring evidence include: (1) quaking aspen (Populus tremuloides) and spruce-fir age structure, (2) conifer death dates, (3) traumatic resin ducts and ring-width changes, and (4) conifer fire scars. Pre-1905 fire regimes in the upper montane forest sites were variable, with drier, south-facing portions of some sites recording frequent, low-severity fire (mean fire interval of all fires ranging from 5 yr to 11 yr among sites), others burning with stand-replacing severity, and others with no evidence of fire for >300 yr. Reconstructed fires at three of the four sites (Pinaleno Mountains, San Francisco Peaks, and Gila Wilderness) had stand-replacing fire patches >200 ha, with maximum patch sizes ranging from 286 ha in mixed conifer-aspen forests to 521 ha in spruce-fir forests. These data suggest that recent stand-replacing fire patches as large as 200 ha to 500 ha burning in upper elevation (>2600 m) mixed conifer-aspen and spruce-fir forests may be within the historical range of variability.

Multiple dendrochronological responses to the eruption of Cinder Cone, Lassen Volcanic National Park, California

Two dendrochronological properties – ring width and ring chemistry – were investigated in trees near Cinder Cone in Lassen Volcanic National Park, northeastern California, for the purpose of re-evaluating the date of its eruption. Cinder Cone is thought to have erupted in AD 1666 based on ring-width evidence, but interpreting ring-width changes alone is not straightforward because many forest disturbances can cause changes in ring width. Old Jeffrey pines growing in Cinder Cone tephra and elsewhere for control comparison were sampled. Trees growing in tephra show synchronous ring-width changes at AD 1666, but this ring-width signal could be considered ambiguous for dating the eruption because changes in ring width can be caused by other events. Trees growing in tephra also show changes in ring phosphorus, sulfur, and sodium during the late 1660s, but inter-tree variability in dendrochemical signals makes dating the eruption from ring chemistry alone difficult. The combination of dendrochemistry and ring-width signals improves confidence in dating the eruption of Cinder Cone over the analysis of just one ring-growth property. These results are similar to another case study using dendrochronology of ring width and ring chemistry at Parícutin, Michoacán, Mexico, a cinder cone that erupted beginning in 1943. In both cases, combining analysis with ring width and ring chemistry improved confidence in the dendro-dating of the eruptions.

Influences of Mechanized Thinning and Prescribed Underburning on Radial Growth of Jeffrey Pine

Forest thinning utilizing cut-to-length and whole-tree harvesting systems with subsequent underburning were assessed for their impacts on several components of radial increment in uneven-aged Jeffrey pine (Pinus jeffreyi Grev. & Balf.) on the east slope of the Sierra Nevada during a period of extended drought. At the conclusion of three growing seasons following thinning and two seasons after burning, increment cores were extracted from dominant and codominant crown class trees over a century old as well as from intermediate crown class trees that were approximately 20 years younger. Separate measurements of early wood and late wood ring width during each of the 10 growing seasons preceding treatment and three seasons subsequent to thinning were summed for each year to obtain total ring width and permitted the calculation of proportions of total increment of the respective components. Comparisons of posttreatment values or averages of each component as well as of the magnitude of change, in both absolute and relative terms, in their values following treatment from 10-year pretreatment means were made among treatments for three posttreatment phases. Thinning treatment differences in direct measurements of the several components were marginal and uncommon. However, disparities in the magnitude of shifts in radial increment resulting from thinning were highly significant. Total ring width in dominant and codominant trees averaged 14% below to 13% above the pretreatment level in thinned portions of the stand over the three postthinning phases examined, while in the unthinned control total increment was 30-53% lower than the pretreatment mean, with the lowest values in all treatments occurring during the driest period of the study and highest observed after annual precipitation increased nearer to normal. In intermediate crown class trees, changes in ring width among the thinning treatments were similar to those in the dominant and codominant trees. Differences between the cut-to-length and whole-tree treatments were more pronounced in the dominant/codominant trees and comparisons generally revealed higher relative growth in the latter than in the former, while in the intermediate crown class, trees in the cut-to-length treatment performed marginally better in this regard than those in the whole-tree treatment. Influences of prescribed fire were limited to only a few components of radial growth in both sets of trees considered. The magnitude of change in several components of radial growth following thinning was found to be negatively correlated with residual basal area, but only in dominant and codominant trees. Live crown percentage influenced radial growth preceding thinning in both the dominant/ codominant and intermediate crown classes, in which it was a positive factor, as well as changes in increment subsequent to thinning in the former alone, when it was negative. Overall, results of this study demonstrate that considerable improvement in stand productivity can be realized with density management in an older, dry site forest type, which at minimum is not diminished by subsequent underburning.

Dendrochronological responses to the 24 October 1992 tornado at Sunset Crater, northern Arizona

This paper documents tree-ring responses to a historic tornado and reevaluates prehistoric tree-ring changes seen in archaeological wood of Wupatki Ruin used to date the 11th-century eruption of Sunset Crater. The historic tornado occurred at Sunset Crater, northern Arizona, on 24 October 1992, and trees within areas damaged by the tornado survived the event and continue living today. The objectives of this research were to document their ring-growth changes and to consider the possibility of tornadoes as a candidate disturbance for the prehistoric ring-growth changes of Wupatki. About half of the trees sampled within areas damaged by the tornado show one or more dendrochronological responses to that event, including ring-width release, reaction wood, ring-width suppression, and (or) reduced latewood. Tornado damage is not a likely candidate for having caused the abrupt ring-width changes at AD 1064–1065 seen at Wupatki. However, five living ponderosa pines (Pinus ponderosa Dougl. ex P. & C. Laws.) at Sunset Crater experienced abrupt and severe suppressions in ring growth beginning decades ago and continuing today. No single disturbance seems obvious for causing these growth suppressions, but further research is merited to find the cause of these modern suppressions to propose a new candidate explanation for the AD 1064 suppression.

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.

Dendroclimatological spring rainfall reconstruction for an inner Alpine dry valley

Estimates of spring precipitation for the inner Alpine dry valley of the upper Inn (Tyrol, Austria) are made back to A.D. 1724 using a ring width chronology of Scots pine (Pinus sylvestris L.) as predictor. A highly significant agreement in year-to-year ring width changes exists between several chronologies along the dry valley. The dendroclimatic model used for climate reconstruction is a simple linear transfer function that estimates April–June precipitation from current tree-ring width. All verification statistics commonly used in dendroclimatological research are significant ( p < 0.01) and indicate that the reconstructed time series provides valuable information on past spring precipitation variability. Reconstructed spring rainfall deficiencies and surpluses ≥ 20% compared to the long-term mean in 1819, 1832, 1834, 1865, 1885, and in 1780, 1782, 1821, 1853, 1910, respectively, are also documented by local historical records. Furthermore, a comparison is made with an independent climate reconstruction based on historical weather indices valid for the northern side of the Swiss Alps. A fairly good agreement is found between both spring rainfall reconstructions at low frequency intervals during 1755–1862 and 1919–1981. This preliminary study shows that tree-rings can be used to reconstruct spring rainfall variability for inner Alpine dry valleys.

High-resolution climate signals in the Bølling–Allerød Interstadial (Greenland Interstadial 1) as reflected in European tree-ring chronologies compared to marine varves and ice-core records

Lateglacial and Holocene tree-ring chronologies are unique archives, which provide various information on past environments on a true annual time scale. Changes in ring-width can be related to past climate anomalies and dendrodated wood provides an ideal source for radiocarbon calibration. We present a 1051 year tree-ring chronology from the Late Glacial, built from subfossil Scots pines (Pinus sylvestris) that grew in different regions of Central and Southern Europe. Through a series of high-precision radiocarbon measurements we obtained a floating radiocarbon chronology, which allowed accurate wiggle-matching to the INTCAL98 calibration curve. The trees show a coherent pattern in ring-width variations throughout Central Europe, and extending into the Mediterranean, which indicates a strong external climatic factor, most probably temperature during the growing season. We identified major growth events, which appear synchronous with events seen in isotopic and tracer signals in the Greenland ice cores and with changes in the strength of upwelling in the Cariaco Basin.

Strength properties and density of SO 2 polluted spruce wood

pollution during approximately 1935 and 1992 respectively, was studied as to its mechanical properties (fracture toughness, acoustic emission (AE)) as well as its density and annual ring width changes. Earlywood and latewood width and density were measured with X-ray densitometry equipment. The mechanical tests were performed with specimens taken from the same trees using the wedge splitting technique. Using notched, rectangularly shaped specimens, the experiments allowed to determine the notch-tensile strength σNTS of each yearring in RL orientation separately by differentiating earlywood and latewood. The results show clear correlations between earlywood density and notch-tensile strength, good, inverse correlation to some extent between ring width and σNTS and also between AE emission activity and earlywood width for the less polluted trees. Data scattering with resulting less pronounced trends was found for all parameters measured for the more severely polluted trees. The results and correlations allow assuming that σNTS is influenced by the SO2 pollution to some extent via treering growth (ring width) and density. The results point to a more pronounced influence of SO2 pollution between approximately 1970 and 1985 than before that time, and a subsequent recovery of the tested wood properties in the trees that had survived this period.

Tree-ring evidence for an A.D. 1700 Cascadia earthquake in Washington and northern Oregon

Geologic evidence and radiocarbon dating indicate that a subduction earthquake, or series of earthquakes, occurred about 300 yr ago along the Pacific Northwest coast of the United States. Some radiocarbon dates come from remnants of the myriad trees drowned by coincident subsidence. At several coastal lowland locations in Washington and northern Oregon, we located two or more trees that survived partial submergence and lived to the 1990s. Many of them were damaged by shaking and/or inundation. Some survivors recorded the event(s) by anomalous changes in ring width or anatomy of their annual rings. The disturbance initiating the changes can be dated to between the growing seasons of A.D. 1699 and 1700. One killed tree has a last ring of A.D. 1699. Tree-ring dated evidence of disturbance extends along about 100 km of coastal Washington and northern Oregon. These results support the inference that a great (M w~8) earthquake or larger at the Cascadia subduction zone generated the historical tsunami that struck Japan in January 1700.