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"Trees Age determination."
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Improving estimates of total tree ages based on increment core samples
Accurate (i.e., annual resolution) determination of total tree ages with increment core samples is difficult because of the improbability of intercepting the pith at the root collar for most trees. For the xeric conifer Austrocedrus chilensis (D. Don) Florin and Boutelje in northern Patagonia (Argentina), we developed and tested a three-stage procedure for improving estimates of total tree ages. i) For increment core samples not reaching the pith, a graphical technique is used to estimate the missing length of the tree radius. ii) Cumulative radial growth curves are used to estimate the numbers of rings in the missing lengths at variable heights above the root collar. And, iii) number of years required to reach coring height are derived from height-growth curves for seedlings growing under different site conditions. Approximately 500 seedlings (< 100 cm tall) were uprooted and sectioned for determination of height-growth curves and radial-growth curves at different stem heights. From these curves, total ages were estimated for trees sampled with increment borers. These procedures may reduce errors resulting from assumptions of circular ring symmetry or constant radial growth rate. However, where age determination requires estimation of the location of the missed pith, complete accuracy is not likely in all cases. For example, for slow-growing Austrocedrus trees, a missing core length of just 1 cm may result in errors of 10 to 20 years. Differences in rates of tree growth among stands of Austrocedrus indicate that the most accurate estimates of total tree ages require determination of seedling growth rates for each homogeneous site sampled for age structure. Best estimates must also take into account the differential growth rates of subpopulations of seedlings within each stand due to microsite variation and competitive influences.
Journal Article
Estimation of changes in carbon sequestration and its economic value with various stand density and rotation age of Pinus massoniana plantations in China
Plantations actively participate in the global carbon cycle and play a significant role in mitigating global climate change. However, the influence of forest management strategies, especially planting density management, on the biomass carbon storage and production value of plantations for ensuring carbon sink benefits is still unclear. In this study, we estimated the carbon sequestration and economic value of
Pinus massoniana
plantations with various stand densities and rotation ages using a growth model method. The results revealed that with increasing stand age, low-density plantations at 2000 trees·ha
−1
(358.80 m
3
·ha
−1
), as well as high-density plantations at 4500 trees·ha
−1
(359.10 m
3
·ha
−1
), exhibited nearly identical standing volumes, which indicated that reduced inter-tree competition intensity favors the growth of larger trees during later stages of development. Furthermore, an increase in planting density led to a decrease in the average carbon sequestration rate, carbon sink, and number of trees during the rapid growth period, indicating that broader spacing between trees is favorable for biomass carbon accumulation. Further, extending the rotation period from 15 to 20 years or 25 years and reducing the optimal planting density from 3000 to 2000 trees·ha
−1
increased the overall benefits of combined timber and carbon sink income by 2.14 and 3.13 times, respectively. The results highlighted that optimizing the planting density positively impacts the timber productivity and carbon sink storage of
Pinus massoniana
plantations and boosts the expected profits of forest managers. Thus, future afforestation initiatives must consider stand age and planting density management to shift from a scale-speed pattern to a quality-benefit design.
Journal Article
Sediment source fingerprinting: benchmarking recent outputs, remaining challenges and emerging themes
PurposeThis review of sediment source fingerprinting assesses the current state-of-the-art, remaining challenges and emerging themes. It combines inputs from international scientists either with track records in the approach or with expertise relevant to progressing the science.MethodsWeb of Science and Google Scholar were used to review published papers spanning the period 2013–2019, inclusive, to confirm publication trends in quantities of papers by study area country and the types of tracers used. The most recent (2018–2019, inclusive) papers were also benchmarked using a methodological decision-tree published in 2017.ScopeAreas requiring further research and international consensus on methodological detail are reviewed, and these comprise spatial variability in tracers and corresponding sampling implications for end-members, temporal variability in tracers and sampling implications for end-members and target sediment, tracer conservation and knowledge-based pre-selection, the physico-chemical basis for source discrimination and dissemination of fingerprinting results to stakeholders. Emerging themes are also discussed: novel tracers, concentration-dependence for biomarkers, combining sediment fingerprinting and age-dating, applications to sediment-bound pollutants, incorporation of supportive spatial information to augment discrimination and modelling, aeolian sediment source fingerprinting, integration with process-based models and development of open-access software tools for data processing.ConclusionsThe popularity of sediment source fingerprinting continues on an upward trend globally, but with this growth comes issues surrounding lack of standardisation and procedural diversity. Nonetheless, the last 2 years have also evidenced growing uptake of critical requirements for robust applications and this review is intended to signpost investigators, both old and new, towards these benchmarks and remaining research challenges for, and emerging options for different applications of, the fingerprinting approach.
Journal Article
A Complete Terrestrial Radiocarbon Record for 11.2 to 52.8 kyr B.P
Radiocarbon (¹⁴C) provides a way to date material that contains carbon with an age up to ~50,000 years and is also an important tracer of the global carbon cycle. However, the lack of a comprehensive record reflecting atmospheric ¹⁴C prior to 12.5 thousand years before the present (kyr B.P.) has limited the application of radiocarbon dating of samples from the Last Glacial period. Here, we report ¹⁴C results from Lake Suigetsu, Japan (35°35'N, 135°53'E), which provide a comprehensive record of terrestrial radiocarbon to the present limit of the ¹⁴C method. The time scale we present in this work allows direct comparison of Lake Suigetsu paleoclimatic data with other terrestrial climatic records and gives information on the connection between global atmospheric and regional marine radiocarbon levels.
Journal Article
Resolution of ray-finned fish phylogeny and timing of diversification
Ray-finned fishes make up half of all living vertebrate species. Nearly all ray-finned fishes are teleosts, which include most commercially important fish species, several model organisms for genomics and developmental biology, and the dominant component of marine and freshwater vertebrate faunas. Despite the economic and scientific importance of ray-finned fishes, the lack of a single comprehensive phylogeny with corresponding divergence-time estimates has limited our understanding of the evolution and diversification of this radiation. Our analyses, which use multiple nuclear gene sequences in conjunction with 36 fossil age constraints, result in a well-supported phylogeny of all major rayfinned fish lineages and molecular age estimates that are generally consistent with the fossil record. This phylogeny informs three longstanding problems: specifically identifying elopomorphs (eels and tarpons) as the sister lineage of all other teleosts, providing a unique hypothesis on the radiation of early euteleosts, and offering a promising strategy for resolution of the \"bush at the top of the tree\" that includes percomorphs and other spiny-finned teleosts. Contrasting our divergence time estimates with studies using a single nuclear gene or whole mitochondrial genomes, we find that the former underestimates ages of the oldest ray-finned fish divergences, but the latter dramatically overestimates ages for derived teleost lineages. Our time-calibrated phylogeny reveals that much of the diversification leading to extant groups of teleosts occurred between the late Mesozoic and early Cenozoic, identifying this period as the \"Second Age of Fishes.\"
Journal Article
A refined guide for aging muskoxen (Ovibos moschatus) based on mandibular examination
Accurately aging wildlife is essential for effective management and conservation efforts because it supports the estimation of demographic parameters used to model population dynamics and determine harvest quotas. Currently, accurately aging muskoxen is limited by the lack of validated and standardized protocols specific to this species. We investigated three methods for aging muskoxen: tooth eruption pattern, mandible morphometrics, and cementum annuli analysis (CAA). We examined 260 mandibles from community-harvested muskoxen with known harvest dates from Nunavut and the Northwest Territories and radiographed 89 of these mandibles with erupting teeth to track eruption stages. From these data, we developed a key to estimate age of muskoxen from newborn until all permanent teeth have completely erupted (60 months). Next, we assessed the relationship between muskox mandible morphometrics and age using 178 archived mandibles from Banks Island, Northwest Territories. Caudal mandible length was the strongest predictor of age in months (Adjusted R 2 = 0.917) up to 5 years old (60 months), after which growth was negligible. This regression model included linear, quadratic, and interaction terms for caudal mandible length with sex. To evaluate accuracy of CAA for aging, we compared cementum results from incisors of 14 captive muskoxen to their known age using linear regression (Adjusted R 2 = 0.847). We applied this model, fitted to captive muskox data, to predict the age of 32 community harvested adult muskoxen over 60 months old (5 yo + ) using cementum age results. While there was a tendency to underestimate age, this method provided a more informative estimate than classifying all animals as adults once all teeth have erupted. Integrating these methods, we developed a decision tree to guide aging based on the putative age class and available sample type. This framework improves age estimation accuracy for harvested muskoxen, supporting population models and enabling more effective management and conservation.
Journal Article
The use of decision tree analysis for improving age estimation standards from the acetabulum
Accurate, reliable and easy-to-use statistical methods in multifactorial age estimation from the skeleton remains a much-debated issue. In this paper, we explore the use of decision trees in adult age estimation. For this purpose, a dataset from 100 acetabula of South Africans, previously used for age estimation using transition analysis, were used to build a basic decision tree. A test sample of 25 individuals were then employed to assess the newly developed decision tree. Using the decision tree, 20 of the 25 individuals were classified into the correct age group (young, middle or older adults), with the remaining 5 falling within the adjacent age group. The decision tree provided a more accurate outcome as compared to the previous study using transition analysis. Although much research is still needed, this analysis suggests that decision trees may be usable in adult age estimation and may handle the non-linear relationship between chronological and biological age somewhat better than other traditional statistical methods.
•The study explores the use of decision tree analysis for estimation age from the acetabulum.•A comparison is drawn between the accuracy and error rates of transition analysis and decision tree analysis.•The study highlights the importance of exploring new statistical methods for age estimation f, as this remains a challenging area in constructing a demographic profile.
Journal Article
Statistical age determination of tree rings
Dendrochronology, the study of annual rings formed by trees and woody plants, has important applications in research of climate and environmental phenomena of the past. Since its inception in the late 19.sup.th century, dendrochronology has not had a way to quantify uncertainty about the years assigned to each ring (dating). There are, however, many woody species and sites where it is difficult or impossible to delimit annual ring boundaries and verify them with crossdating, especially in the lowland tropics. Rather than ignoring dating uncertainty or discarding such samples as useless, we present for the first time a probabilistic approach to assign expected ages with a confidence interval. It is proven that the cumulative age in a tree-ring time series advances by an amount equal to the probability that a putative growth boundary is truly annual. Confidence curves for the tree stem radius as a function of uncertain ages are determined. A sensitivity analysis shows the effect of uncertainty of the probability that a recognizable boundary is annual, as well as of the number of expected missing boundaries. Furthermore, we derive a probabilistic version of the mean sensitivity of a dendrochronological time series, which quantifies a tree's sensitivity to environmental variation over time, as well as probabilistic versions of the autocorrelation and process standard deviation. A computer code in Mathematica is provided, with sample input files, as supporting information. Further research is necessary to analyze frequency patterns of false and missing boundaries for different species and sites.
Journal Article
Venerable trees of tropical Chinese Wuzhishan city: Distribution patterns and drivers
In this study, we investigated the relationships among species composition, diversity, distribution, growth status, and habitats of venerable trees (VTs) in Wuzhishan City, Hainan, China. VT are defined as venerable tree. VTs bear witness to changes in human society and culture; VTs that once occurred in open or forested areas are now often surrounded by or adjacent to new infrastructure and urban development. In spite of urban development, protecting VTs is important for preserving the history they contain as a part of their carbon sequestration, maintaining their unique ecological services, and continuing to appreciate and advance their cultural symbolism and meaning. We studied VTs and their habitats based on literature reviews, field surveys, interviewing local people, and tree-age determination in the laboratory. Our results revealed 216 VTs in Wuzhishan City of 100 or more years old, belonging to nine families, 13 genera and 21 species. Among families, Sapindaceae comprised the largest number of VTs with 79 species and was especially represented by the fruit tree,
Litchi chinensis
Sonn (Lychee). Perhaps unsurprisingly, we also found that older VTs were rarer than younger ones with the age structure being 192 VTs 100–299 years old, 21 trees 300–499 years old, and only three trees 500 years old or older. The average age was 163 years. Tree height, trunk girth, and crown width had normal distributions, with means of mean 32.1 m, 423 cm, 17 m, respectively. Overall, VTs were more-or-less evenly distributed across the study area, though there were biases in location when age was taken into account with older trees tending to occur at mid-elevations within the study area, but at higher elevations than other VTs. We applied a general linear model (GLM) to analyze the association between attributes of VTs and environmental data. The models revealed significant correlations between tree height and precipitation of the wettest month (
p
= 8.69 × 10
–4
), trunk girth and mean annual temperature (
p
= 9.30 × 10
–4
) and precipitation of the coldest quarter (
p
= 3.06 × 10
–4
), and crown width and mean temperature of the warmest quarter (
p
= 8.28 × 10
–3
). In conclusion, Wuzhishan City is home to diverse VTs with distributions driven at least in part by environmental factors (e.g.,temperature, precipitation, elevation, etc.). VTs can be maintained through enhanced conservation measures that acknowledge their cultural, ecological, and historical value.
Journal Article