Absent Rings Research Articles

Characteristics and Outcomes of Surgical Treatment for Bronchial Anomalies.

Bronchial anomalies are rare but challenging conditions to treat in children, encompassing a variety of structural abnormalities that could compromise airway patency. This includes complete rings, absent cartilage, traumatic avulsions, bronchoesophageal fistulas, and cartilaginous sleeves. The objective of this study is to describe the characteristics and outcomes of a series of pediatric cases of bronchial anomalies that were treated by slide tracheobronchoplasty. This is a single-institution retrospective case series of pediatric patients with bronchial anomalies who underwent surgical treatment between February 2004 and April 2020. Data extracted from electronic medical records included patient demographics, comorbidities, and surgical outcomes. There were a total of 29 patients included in the study, of which 14 had complete bronchial rings, 8 had absent bronchial rings, 4 had traumatic bronchial avulsions, 2 had bronchoesophageal fistulas, and one had a cartilaginous sleeve. Median follow-up time was 13 months (with a range of 0.5-213 months). The overall mortality rate was 17.2% (5 patients), all of whom had complete bronchial rings. Patients with complete bronchial rings also had a higher rate of not only cardiac (85.7%) and pulmonary comorbidities (85.7%) but also secondary airway lesions (78.6%). This is the largest series to date describing surgical treatment for bronchial anomalies. Complete bronchial rings were the most common anomaly treated, followed by absent rings and trauma. Surgical treatment can be successful but mortality rates are higher in patients with complete bronchial rings, possibly due to higher rates of pulmonary and cardiac comorbidities. 4 Laryngoscope, 133:3334-3340, 2023.

Direct effects of tephra fallout from the Puyehue–Cordón Caulle Volcanic Complex on Nothofagus pumilio ring widths in northern Patagonia

We evaluated the radial growth response of adult Nothofagus pumilio (Poepp. et Endl) Krasser trees affected by tephra deposition following historical volcanic eruptions of the Puyehue–Cordón Caulle Volcanic Complex (PCCVC) in northern Patagonia. Standard tree–ring width chronologies were developed for trees from two sites that were affected by up to 55 cm of tephra during the 2011 eruption, which allowed us to detect the general tree–growth response to eruptions VEI ≥ 3 and VEI ≤ 2. The tree growth trend satisfactorily followed the mean temperature record (r = 0.42); however, the analysis of studentized residuals identified outliers (≥ ± 2 SD) directly related to the volcanic eruptions of the years 1921–1922 and 2011 and the respective post–eruption years, while for the 1960 eruption and following year, they largely exceeded the mean value of the residuals. The large amount of tephra deposited during the 1921–22 and 2011 eruptions caused physical damage to the tree canopy leading to the appearance of white rings and to locally absent rings. The rate of change in radial growth of trees during these eruptions presented significant declines in relation to the growth of five years before the eruption and to the following year. The low amount of tephra deposited during the 1960 eruption did not cause damage to the stands and trees increased their radial growth. In general, trees that had reduced radial growth experienced a remarkable recovery starting in the second or third post–eruption year. The amount of tephra deposited and the time of year of the volcanic eruptions had an important influence on tree rings. Some ecophysiological causes that could explain the growth responses of N. pumilio to tephra fall are discussed herein. Our study may provide useful insights to clarify the uncertain characteristics of some eruptions in the past or to detect the occurrence of large, undocumented volcanic eruptions throughout the Andes.

The effects of fire on Pinus sylvestris L. as determined by dendroecological analysis (Sierra de Gredos, Spain)

Iberian populations of Scots pine (Pinus sylvestris L.) have been declining since the late-glacial period; among those that remain, relict stands have great biological and ecological value. This paper investigates the effects of a 2009 fire on tree growth in one of these small populations in the Sierra de Gredos (Spain) by examining the responses recorded in the tree-ring width series of the surviving trees. The current status and distribution of these surviving trees reveal the severity of the fire; indeed most show scars or other evidence of fire damage. Dendroecological analysis revealed narrower tree rings, indicating negative pointer years for the year of the fire and the following year. A very significant reduction in growth was recorded for the years after the fire, both in terms of tree-ring width and basal area increment; incomplete and even absent rings were also recorded. No relationship was seen between these effects and climatic events. The dates and geographical extension of former possible disturbances were also investigated, using the data from these same trees plus information collected from others in the region. The vulnerability of these populations to past fires was evident. Lastly, given the problems affecting the regeneration of these relict populations, it is strongly suggested to urgently include all these populations in conservation and environmental management programs.

Frequent locally absent rings indicate increased threats of extreme droughts to semi-arid Pinus tabuliformis forests in North China

Global climatic change indicates that some climate systems have passed tipping points, e.g. the inner East Asia; however it's still uncertain when the tipping point of forest mortality could be triggered. Absent rings are early warnings of irreversible mortality. They widely exist in Northern Hemisphere forests, but they're locally rare and under-discussed in previous studies. We reported a tree ring network, including 17 collections among the extensive distribution of Pinus tabuliformis in North China. Locally absent rings (LAR) were counted and logistic models were built to determine biotic and abiotic driving forcings of LAR. Pinus tabuliformis suffered increasing LAR frequency in recent decades, and the highest LAR frequency occurred at the driest distributional margin. At the semi-arid region, LAR frequency increased along with increasing age, decreasing previous September moisture, and decreasing May moisture. LAR risk would gradually increase, and older trees would suffer quite high LAR risk in the future. We highlight the connection between frequent LAR and extreme droughts in semi-arid pine forests, and propose that LAR can be a proxy of the potential tipping points of forest systems.

New insights into estimating the age of old Scots pine from increment cores with stem rot

Trunk inner rot is a common phenomenon in some old-growth pine dominated forests, making it impossible to determine tree age by counting annual rings. We compared the efficiency of five methods to estimate the age of hollow pine trees (Pinus sylvestris L.). Our main aims were to select the best-performing method and to test whether the age of the tree or the proportion of rot influences the accuracy of estimation. We used full increment cores (reaching the pith or within 1 cm of it) from 100 trees (54–562 years old) collected in northern Sweden and simulated rotten centres of three different sizes in order to test the methods. The lowest error rates were obtained when less than a third of the sample was missing (down to 5.0 % error rate), and by using a method based on the growth pattern of a set of healthy trees. Using linear extrapolation of the mean radial growth led to large overestimates (up to three times the number of absent rings) with error rates up to 27.3 %. We also found that the performance of all methods was reduced in cores from older trees. Our main conclusion is that non-linear methods should be preferred for age estimation of hollow pines. We also argue that more precision in the age estimation could be gained already in the field by collecting multiple cores from rotten trees or by developing alternative coring methods.

Congenital Absence of Tracheal or Bronchial Rings.

Congenital airway stenosis secondary to absent tracheal or bronchial rings is a rare congenital anomaly that is difficult to manage both clinically and surgically. This typically manifests as severe segmental tracheomalacia, and only isolated cases with short-term follow-up have been previously described. We aim to describe a series of children with absent tracheal or bronchial rings who underwent surgical management and had long-term follow-up. Case series with chart review. Tertiary care pediatric hospital. Patients with absent tracheal or bronchial rings from 2002 to 2016. Electronic and paper medical records were queried to obtain demographics, age at diagnosis and surgery, pre- and postoperative symptoms, location of absent rings, procedure performed, length of follow-up, and adjunctive procedures performed. Nine subjects were identified who underwent slide tracheoplasty for correction of congenital absent tracheal or bronchial rings. Age at diagnosis ranged from 10 days to 5 years of age (median, 4 weeks). Age at surgery ranged from 3 weeks to 5 years of age (median, 5 weeks). Six out of 9 subjects were extubated on postoperative day 1. Only 1 subject required additional intervention, which included balloon dilation, tracheobronchial stenting, and aortopexy to alleviate the obstruction. Mean follow-up time was 5.89 years. This is the largest series of children with absent tracheal rings who underwent slide tracheoplasty with long-term follow-up presented to date. Slide tracheoplasty is an effective surgical intervention for the treatment of absent tracheal or bronchial rings in infants and young children.

Thoracic Endodermal Sinus Tumor with Root Compression Mimicking Guillain–Barre Syndrome in Clinical Presentation, CSF Studies, and EMG/NCV Findings

AbstractA 2-year-old boy who presented with clinical, cerebrospinal fluid, and electrophysiological findings consistent with Guillain–Barre syndrome (GBS) was found to have a thoracic spinal cord mass due to a yolk sac tumor. On examination, he had an absent anal wink and flaccid anal ring which is atypical for GBS. This case demonstrates the need for a thorough physical examination on presentation of a child with a clinical and laboratory presentation of GBS and highlights the importance of prompt imaging studies when clinical suspicion arises because of atypical clinical signs, such as absent anal wink or low rectal tone.

Notes towards an optimal sampling strategy in dendroclimatology

Though the extraction of increment cores is common practice in tree-ring research, there is no standard for the number of samples per tree, or trees per site needed to accurately describe the common growth pattern of a discrete population of trees over space and time. Tree-ring chronologies composed of living, subfossil and archaeological material often combine an uneven distribution of increment cores and disc samples. The effects of taking one or two cores per tree, or even the inclusion of multiple radii measurements from entire discs, on chronology development and quality remain unreported. Here, we present four new larch (Larix cajanderi Mayr) ring width chronologies from the same 20 trees in northeastern Siberia that have been independently developed using different combinations of core and disc samples. Our experiment reveals: i) sawing is much faster than coring, with the latter not always hitting the pith; ii) the disc-based chronology contains fewer locally absent rings, extends further back in time and exhibits more growth coherency; iii) although the sampling design has little impact on the overall chronology behaviour, lower frequency information is more robustly obtained from the disc measurements that also tend to reflect a slightly stronger temperature signal. In quantifying the influence of sampling strategy on the quality of tree-ring width chronologies, and their suitability for climate reconstructions, this study provides useful insights for optimizing fieldwork campaigns, as well as for developing composite chronologies from different wood sources.

Cessation of annual apical growth and partial death of cambium in stem of Abies sachalinensis under intensive shading.

This study evaluated variation in the height at which absent rings and internodes were detected along stem of Abies sachalinensis trees grown under shade for 39years. Eight sample trees planted in 1974 under a secondary forest in Japan were felled in 2013 and analyzed. A. sachalinensis is a monopodial species in which it is possible to measure annual apical growth using the distinct internodes. We applied microscopic analysis on 154 stem disks from the stem base to the top to evaluate the cessation of apical and radial growth caused by intensive shading. Cessation of apical stem growth for one or more years was found in 6 out of 8 sample trees. We termed this phenomenon as "absent internode". In addition, the absent growth rings were detected more frequently in the lower part of sample stems, and the number of absent rings at the stem base did not correspond with the number of absent internodes in the six trees. From cellular level observation, the five suppressed trees had no living cambial cells at the stem base but had living cells at the stem top. The cessation of the apical and radial growth did not occur synchronously but did occur independently under a shade environment in A. sachalinensis.

开都河流域天山桦树轮宽度年表的建立及其气候响应

PDF HTML阅读 XML下载 导出引用 引用提醒 开都河流域天山桦树轮宽度年表的建立及其气候响应 DOI: 10.5846/stxb201306111650 作者: 作者单位: 中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所,中国气象局乌鲁木齐沙漠气象研究所 作者简介: 通讯作者: 中图分类号: P935.1 基金项目: 中央级公益性科研院所基本科研业务费项目(IDM201204);国家科技支撑计划项目(2012BAC23B00);国家重点基础研究发展计划(2013CB955900)和科技部公益性行业(气象)科研专项(GYHY201206014)共同资助 Development of the tree-ring width chronology of Betula tianschanica for the Kaiduhe River watershed and its climate response Author: Affiliation: Institute of Desert Meteorology,,,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用开都河流域中段采集的天山桦树芯样本,建立了这一采样点的树轮宽度年表。该年表的特征参数与其他地区已有的桦木树轮宽度年表相近,且能较好地反映研究区内天山桦树轮宽度变化的基本特征。该年表与研究区内雪岭云杉树轮宽度年表间的相关分析表明,两者在全频域、高频域及低频域上均存在显著正相关。树木生长气候响应分析结果显示,天山桦树轮宽度与降水量的相关则不显著;而与上年12月呈显著正相关(r= 0.346,P < 0.01,n=59),与当年6月的平均气温呈显著负相关(r=-0.312,P < 0.01,n=60)。该年表存在2.1、4.0a和~50a变化准周期,并且其与3月多元El Nio-Southern Oscillation (ENSO)指数存在相似的变化趋势。 Abstract:In this study, a total of 40 cores from 20 birch trees (Betula tianschanica) were obtained for one single site, named as Haerhatigou (HEX) in the middle section of the Kaiduhe River watershed in August 2011. All the tree-ring cores were naturally dried, mounted, surfaced, and cross-dated following standard dendrochronological procedures. Each ring-width was measured with a resolution of 0.001 mm by a dendrometer (Velmex Measuring System). The quality control of the cross-dating was carried out using the COFECHA program. Because of the low correlations with the master dating series, 5 cores from 3 trees were rejected. In the end, 35 cores from 18 trees were used for further analyses. The number of the absent rings is 78, and the rate of the absent rings in the samples is 2.325%. The ARSTAN program was used for de-trending and developing tree-ring chronologies. The age- and size- related variation of the tree-ring widths was removed by a single detrending process applied on each tree-ring measurement: a negative exponential curve, a kind of conservative function. After all these processes, three kinds of chronologies from one sample site were obtained: standard chronology (STD), residual chronology (RES), and Arstan chronology (ARS). The statistical characteristics of the HEX chronology are similar to other birch chronologies' in the previous studies. And the chronology can well represent the variety of the radial growth of birch trees in the study area. The significant positive correlations in the original, high-, and low- frequency domain between the HEX chronology and a chronology of spruce trees (HE4) mean that the dominant climatic factors of two kinds of trees are similar. Pearson correlation analysis was applied to investigate the relationship between the tree-ring width and the climatic data during the calibrated period (1952-2011). The monthly precipitation and mean temperature from the previous August to the current September and the average meteorological data in summer were used to assess how the climatic elements influence the growth of birch trees in the study area. The results of the tree growth-climate responses show that the HEX chronology was found to be positively correlated with the mean temperature of the previous December (r = 0.346, P < 0.01, n=59), and to be negatively correlated with the mean temperature of the current June (r = -0.312, P < 0.01, n=60). Conversely, the relationships between the HEX chronology and the precipitation are not so strong. The results of the power spectral analysis showed that the HEX chronology existed 2.1years and 4.0years cycles. The interannual cycles (2.1years and 4.0years) in our chronology fall within the range of some large-scale oscillation, such as quasi-biennial oscillation (QBO) and El Nio-Southern Oscillation (ENSO). The wavelet analysis demonstrated the existence of significant ~50years cycles of variability. The ~50years cycle suggests a possible important connection of the solar activity cycle (Gleissberg). The 50years cycle has been indicated by some previous studies in Changbai Mountains, Tianmushan Mountains, Huangshan Mountains, and the Changting region in Fujian Province. The similar trend between the chronology and the March Multivariate ENSO Index suggests that the variation of the HEX chronology has strong teleconnections with the oscillations of land-atmospheric-ocean circulation systems. 参考文献 相似文献 引证文献

The rarity of absent growth rings in Northern Hemisphere forests outside the American Southwest

We present a synthesis of locally absent (or “missing”) growth rings across the Northern Hemisphere based on 2359 publicly available tree ring‐width records. During the last millennium, widespread absent rings have been observed only in the southwestern United States and were associated with severe drought. Absent rings were uncommon during the growing seasons that followed major volcanic eruptions, including A.D. 1259 and 1816. Because these features have occurred so rarely in high‐latitude and high‐elevation tree ring‐width records, the hypothesis that the Northern Hemisphere tree ring‐width network is compromised by dating errors due to unrecognized absent rings would require that many temperature‐limited forest stands in the network exhibited a reaction to cold temperatures that have essentially never been observed anywhere. If however absent‐ring formation were to increase in forests outside of the American Southwest, that behavior would represent an unprecedented response to environmental stress.

Growth-Climate Relationships ofPinus strobusIn the Floodway Versus Terrace Forest Along the Banks of the Red Cedar River, Michigan

We examined the effects of climate (i.e. temperature, precipitation, moisture index, river discharge) on the radial growth of eastern white pine (Pinus strobus) in two contrasting microhabitats (floodway versus terrace) in relation to an elevational and moisture gradient along the banks of the Red Cedar River, Michigan. We hypothesized that trees growing on the terrace sites would have a greater sensitivity to climatic factors than trees growing in the floodway. Increment cores were sampled and crossdated from dominant and co-dominant trees in the floodway and terrace sites and standardized growth chronologies were developed. Mean sensitivity, standard deviation, percentage of absent rings, and intertree correlation were generally greater for eastern white pine on the terrace compared to the floodway forests. Dendroclimatic relationships were examined with bootstrapped correlation analysis, which indicated that radial growth of eastern white pine in both floodway and terrace sites was negatively associated with summer temperature (i.e. June and July) of the current growing season. Radial growth in both floodway and terrace sites were positively related to current May precipitation, moisture index, and river discharge. Dendroclimatic response of eastern white pine in floodway and terrace sites differed in that the effect of summer moisture stress was more persistent in the terrace sites into later summer (i.e. current July ) whereas floodway sites showed a negative response to prior-year May precipitation and moisture index. Although precipitation and hydrological conditions of the river were generally favorable during the summer months, which appeared to have promoted soil moisture recharge, flooding in early winter (i.e. prior November) had a negative impact on growth in both microhabitats. The effect of winter river discharge was significantly negative in January (t) in the floodway sites compared to the terrace sites.

Contrasting effects of wildfire and climate on radial growth of Pinus canariensis on windward and leeward slopes on Tenerife, Canary Islands

Little is known concerning the effects of wildfires on tree radial growth and their climatic response under contrasting regimes of fog water inputs on oceanic islands. On Tenerife, Canary Islands, windward slopes are humid with high-fog frequency due to influence of wet trade winds, while climate on leeward slopes is more arid. We used tree-ring records of Pinus canariensis Sweet ex Spreng. to quantify the effects of a fire of known date on radial growth and determine the main limiting climatic factors for growth. Radial growth patterns and their responsiveness to fire severity and climatic variation differed between windward and leeward slopes. Surface fire did not significantly impact growth, while crown fire caused short-term growth reduction, and even cessation, more pronounced on the windward slope. Growth rates, tree-ring common signal, and climate sensitivity were smaller on the windward slope, with cold winters, and summer water stress limiting growth. On the leeward slope, climate explained a greater amount of growth variation mainly due to negative effects of high October–December sea-level pressures causing dry winter conditions. Contrasting growth dynamics on both slopes may result from diverging physiological effects of water inputs and reduced radiation caused by fog drip. Our findings suggest that dating growth suppressions and absent rings are useful to date past high-severity crown fires in P. canariensis forests, in addition to ordinary fire scars dating indicative of low-severity surface fires.

Tree-ring growth and stable isotopes (13C and 15N) detect effects of wildfires on tree physiological processes in Pinus sylvestris L.

Forest fires may alter the physiological and growth processes of trees by causing stress in trees and modifying the availability of soil nutrient. We investigated if, after a high-severity fire, changes in tree-ring growth can be observed, as well as changes in the nitrogen and carbon isotope composition of tree rings of surviving trees. Two wildfires that occurred in Pinus sylvestris L. stands in Northern Italy, one at the beginning and one at the end of the vegetative season, were chosen as the focus of this study. After the fires, the surviving trees showed growth suppression with very narrow tree rings or locally absent rings. The carbon isotope ratio was more negative in tree rings formed in the 5 years following fire, indicating better water supply in a situation of less competition. The nitrogen isotope ratio followed opposite trends in the two wildfire stands. In trees cored in the stand where the fire happened at the beginning of the vegetative season, there was no change in the nitrogen isotope ratio, whereas in samples collected in the other fire site, higher nitrogen isotope ratios were observed in the tree rings formed after the fire, reflecting changes in the soil nitrogen supply. Modifications in the growth and isotope composition of the fire-stressed trees disappeared from 6 to 10 years after the fire. By studying trees before and after fire, we were able to show that fire affects not only the growth of surviving trees, but also their physiological processes.

TREE STEM GROWTH RING ANALYSIS—A CASE STUDY INVOLVING A MATURE CEDAR AND HOUSING DEVELOPMENT

Summary Increment core samples taken from the main stem of cedar tree (Cedrus sp) showed unusual ring width sequences that could not be explained from detailed microscopic analysis. A full trunk disc was obtained and the ring patterns investigated. The occurrence of false and locally absent rings was determined and the rings dated. The beginning of the unusual ring width sequences coincided with development of the land around the trees for housing in the late 1970s. Root damage and/or changes in the rhizosphere associated with the housing development are likely to have been responsible for the period of abnormally slow and erratic growth of the tree. Despite a near twenty-year period of slow and erratic growth the tree had returned to a reasonable, consistent and regular growth ring width sequence by the late 1990s. Caution should be exercised when undertaking ring counts and interpreting ring widths using increment core samples taken from trees that may have suffered traumas as a result of root or soil damage or from the trunks of trees directly below large pruning wounds or lost branches. Similar caution should be exercised when interpreting increment core samples showing unusual resin ducts (cedars and some other conifers) or erratic ring widths.

Frequency of partial and missing rings in Acer saccharum in relation to canopy position and growth rate

Locally absent growth rings are known to occur in trees during periods of environmental stress, but little evidence has been available on their frequency in moist temperate forests or on their potential for causing problems in dendroecological studies. In this study, 95 stem disks of Acer saccharum cut from trees representing a wide range of size and age were examined for ring anomalies using three techniques – inspection of disks for partial rings, crossdating of each tree against regional master chronologies, and use of stand history evidence. The number of ring anomalies in Acer saccharum was inversely related to growth rate and vigor. Mean percentage of ring anomalies was 1.3% in dominant canopy trees, 4.6% in trees of the intermediate crown class, and 16.2% in overtopped trees. All of the overtopped trees had partial or missing rings, with a mean of 10 per tree and a range of 2 to 20. Use of crossdating to correct for ring anomalies appeared to be successful in 88% of the canopy trees. However, crossdating results were inconclusive in 32% of the overtopped trees because of low ring width variability, multiple missing rings, and short duration of trouble-free segments. Because overtopped trees are of limited value in reconstructing disturbance history and often cannot be crossdated reliably, we suggest that they normally be excluded from disturbance chronologies.

Radiocarbon Analysis of Pinus Lagunae Tree Rings: Implications for Tropical Dendrochronology

A promising species for tropical dendrochronology is Pinus lagunae, a pine tree found in Baja California Sur (Mexico) around lat 23.5°N. In 1995, we sampled a total of 27 wood cores from 13 Pinus lagunae trees in Sierra La Victoria (23°36'N, 109°56'W), just north of Sierra La Laguna, at an elevation of 1500–1600 m. Selected trees were locally dominant, but their ring-width patterns could not be crossdated. To test the hypothesis that visible growth layers in Pinus lagunae are formed annually, we measured radiocarbon amounts in individual rings by means of accelerator mass spectrometry (AMS). Twenty-three 14C measurements were used to trace the location of the 1963–64 “bomb spike” in 3 wood increment cores. By comparing the location of that δ14C extreme with the number of visible radial wood increments, it was possible to conclude that 2 cores had a number of locally absent rings, while the 3rd one included a few years with more than one growth layer. Therefore, ring-width patterns of sampled Pinus lagunae were not consistent from one tree to another, most likely because of climatic regime in combination with microsite features. While the possibility of generating Pinus lagunae tree-ring chronologies cannot entirely be ruled out, the development of dendrochronological proxy records of climate from coniferous species in tropical North America should focus on species and sites that experience a more pronounced seasonality.

Wilson's Disease in a Saudi Family

A Saudi family with Wilson’s disease is presented. One member had symptomatic Wilson’s disease leading to liver cirrhosis, portal hypertension, and neuropsychiatric syndrome but absent Kayser-Fleischer rings, while four other sibliRis had asymptomatic Wilson’s disease- The patient with the symptomatic Wilson’s disease will be presented and the significance of early detection is discussed. It seems that Wilson’s disease may be underdiagnosed in Saudi Arabia.

A cross-dated fire history from coast redwood near Redwood National Park, California

Cross sections from coast redwood trees (Sequoiasempervirens (D.Don.)Endl.) in and near Redwood National Park were dendrochronologically cross-dated and used to develop a fire history from 1714 to 1985. A master chronology for the study area was first developed from old-growth trees and provided dating control for fire-scarred samples. Redwood offers a challenge for dendrochronology owing to partially absent rings (ring wedging) and uniform ring widths (complacency). Cross dating was successful in portions of 12 of 24 fire-scarred trees. Fire events were dated by noting the position of fire scars and other fire-associated ring structures (resin ducts, double latewood, growth releases, and ring separations) in the cross-dated ring series. Using only dates of fire scars, the mean fire interval (MFI) was 9.9 years from the first recorded fire in 1714 to the last in 1962. The MFI was 8.0 years for the best represented (greatest sample depth) presettlement period from 1714 to 1881. Using dates for all fire-associated ring features, the MFI from 1714 to 1962 was 7.0 years and from 1714 to 1881 was 6.0 years. Use of all fire-associated ring characteristics is argued to be a more complete representation of past fire frequency due to possible under-representation of fire-scar records from stump-top samples. Based upon scar positions within annual rings, fires occurred predominately late in the growing season or after growth ceased for the year. The mean fire intervals determined are shorter than those reported in all except one other fire history study from coast redwood and suggest that fire frequency in redwood may have been underestimated in many past studies.

Dendroecological studies in New Zealand 1. An evaluation of tree age estimates based on increment cores

Abstract Tree-ring counts from increment cores are widely used in ecological studies for determining tree ages. In New Zealand many canopy trees are slow-growing and long-lived, and have extremely narrow rings. Single rings or groups of rings may be absent on some radii. Such narrow and absent rings cause difficulties in ring counting and necessitate careful sample preparation. The errors associated with age estimates derived from cores which do not reach the chronological centre of the tree (partial cores) are discussed. Four partial core lengths and three methods of estimation were used on cross-sections of known age from Agathis australis, Libocedrus bidwillu, Nothofagus solandri, and Prumnopitys taxifolia. It is concluded that mean errors may be less than ± 10% where the core length represents 90% of the geometric radius (half the measured diameter) increase with shorter cores. However, much greater errors may apply to individual estimates, up to ± 78% in one case. Moreover, the direction of the error...