scholarly journals Is blue intensity ready to replace maximum latewood density as a strong temperature proxy? A tree-ring case study on Scots pine from northern Sweden

2013 ◽  
Vol 9 (5) ◽  
pp. 5227-5261 ◽  
Author(s):  
J. A. Björklund ◽  
B. E. Gunnarson ◽  
K. Seftigen ◽  
J. Esper ◽  
H. W. Linderholm
Keyword(s):  
Image Data ◽  
Base Line ◽  
Sample Treatment ◽  
X Ray ◽  
Maximum Latewood Density ◽  
Latewood Density ◽  
Climate Signals ◽  
Temperature Proxy ◽  
Annual Scale ◽  
Blue Intensity

Abstract. At high latitudes, where low temperatures mainly limit tree-growth, measurements of wood density (e.g. Maximum Latewood Density, MXD) using the X-Ray methodology provide a temperature proxy that is superior to that of TRW. Density measurements are however costly and time consuming and have lead to experimentation with optical flatbed scanners to produce Maximum Blue Intensity (BImax). BImax is an excellent proxy for density on annual scale but very limited in skill on centennial scale. Discolouration between samples is limiting BImax where specific brightnesses can have different densities. To overcome this, the new un-exploited parameter Δ blue intensity (ΔBI) was constructed by using the brightness in the earlywood (BIEW) as background, (BImax − BIEW = ΔBI). This parameter was tested on X-Ray material (MXD − earlywood density = ΔMXD) and showed great potential both as a quality control and as a booster of climate signals. Unfortunately since the relationship between grey scale and density is not linear, and between-sample brightness can differ tremendously for similar densities, ΔBI cannot fully match ΔMXD in skill as climate proxy on centennial scale. For ΔBI to stand alone, the range of brightness/density offset must be reduced. Further studies are needed to evaluate this possibility, and solutions might include heavier sample treatment (reflux with chemicals) or image-data treatment (digitally manipulating base-line levels of brightness).

scholarly journals Chemical destaining and the delta correction for blue intensity measurements of stained lake subfossil trees

2020 ◽  
Vol 17 (18) ◽  
pp. 4559-4570 ◽  
Author(s):  
Feng Wang ◽  
Dominique Arseneault ◽  
Étienne Boucher ◽  
Shulong Yu ◽  
Steeven Ouellet ◽  
...  
Keyword(s):  
Ethylenediaminetetraacetic Acid ◽  
Black Spruce ◽  
Temperature Reconstruction ◽  
Sodium Dithionite ◽  
Sodium Ascorbate ◽  
Maximum Latewood Density ◽  
Intensity Measurements ◽  
Latewood Density ◽  
Canadian Boreal Forest ◽  
Blue Intensity

Abstract. The stain of wood samples from lake subfossil trees (LSTs) is challenging the wide application of the blue intensity (BI) technique for millennial dendroclimatic reconstructions. In this study, we used seven chemical destaining reagents to treat samples of subfossil black spruce (Picea mariana (Mill.) B.S.P.) trees from two lakes in the eastern Canadian boreal forest. We subsequently compared latewood BI (LBI) and delta BI (DBI) time series along with conventional maximum latewood density (MXD) measured from the stained and destained samples. Results showed that the stain of our samples is most likely caused by postsampling oxidation of dissolved ferrous iron in lake sediments that penetrated into wood. Three reagents (ascorbic acid, sodium ascorbate, and sodium dithionite all mixed with ethylenediaminetetraacetic acid) could remove >90 % of Fe. However, even for the best chemical protocol, a discrepancy of about +2 ∘C compared to MXD data remained in the LBI-based temperature reconstruction due to incomplete destaining. On the contrary, the simple mathematical delta correction, DBI, was unaffected by the Fe stain and showed very similar results compared to MXD data (r>0.82) from annual to centennial timescales over the past ∼360 years. This study underlines the difficulty of completely destaining lake subfossil samples while confirming the robustness of the DBI approach. DBI data measured from stained LSTs can be used to perform robust millennial temperature reconstructions.

Temperature sensitivity of blue intensity, maximum latewood density, and ring width data of living black spruce trees in the eastern Canadian taiga

2020 ◽  
Vol 64 ◽  
pp. 125771
Author(s):  
Feng Wang ◽  
Dominique Arseneault ◽  
Étienne Boucher ◽  
Gabrielle Galipaud Gloaguen ◽  
Anne Deharte ◽  
...  
Keyword(s):  
Temperature Sensitivity ◽  
Black Spruce ◽  
Ring Width ◽  
Intensity Maximum ◽  
Maximum Latewood Density ◽  
Latewood Density ◽  
Blue Intensity

Comparison between Blue Intensity (BI) and Maximum Latewood Density (MXD) tree-ring chronologies from the North American Boreal forests

2020 ◽  
Author(s):  
Laia Andreu-Hayles ◽  
Rosanne D'Arrigo ◽  
Rose Oelkers ◽  
Kevin Anchukaitis ◽  
Greg Wiles ◽  
...  
Keyword(s):  
High Resolution ◽  
North America ◽  
Tree Ring ◽  
Boreal Forests ◽  
Ring Width ◽  
Maximum Latewood Density ◽  
Latewood Density ◽  
Tree Ring Data ◽  
Summer Temperatures ◽  
Blue Intensity

<p>Tree ring-width (TRW) and Maximum Latewood Density (MXD) series have been largely used to develop high-resolution temperature reconstructions for the Northern Hemisphere. The divergence phenomenon, a weakening of the positive relationship between TRW and summer temperatures, has been observed particularly in northwestern North America chronologies. In contrast, MXD datasets have shown a more stable relationship with summer temperatures, but it is costly and labor-intensive to produce. Recently, methodological advances in image analyses have led to development of a less expensive and labor-intensive MXD proxy known as Blue Intensity (BI). Here, we compare 6 newly developed BI tree-ring chronologies of white spruce (<em>Picea glauca</em> [Moench] Voss) from high-latitude boreal forests in North America (Alaska in USA; Yukon and the Northwestern Territory in Canada), with MXD chronologies developed at the same sites. We assessed the quality of BI in relation to MXD based on mean correlation between trees, chronology reliability based on the Expressed Population Signal (EPS), spectral properties, and the strength and spatial extent of the temperature signal. Individual BI chronologies established significant correlations with summer temperatures showing a similar strength and spatial cover than MXD chronologies. Overall, the BI tree-ring data is emerging as a valuable proxy for generating high-resolution temperature spatial reconstructions over northwestern America.</p>

Maximum latewood density records of the oldest trees in the world: Great Basin Bristlecone pine (Pinus Longaeva)

2020 ◽  
Author(s):  
Tom De Mil ◽  
Matthew Salzer ◽  
Charlotte Pearson ◽  
Valerie Trouet ◽  
Jan Van den Bulcke
Keyword(s):  
Great Basin ◽  
Ring Width ◽  
Volcanic Eruptions ◽  
Temperature Sensitive ◽  
Climate Signal ◽  
Maximum Latewood Density ◽  
Latewood Density ◽  
Pinus Longaeva ◽  
Bristlecone Pine ◽  
Temperature Proxy

<p>Great Basin Bristlecone pine (Pinus longaeva) is known for its trees that attain old age. The longest chronology is more than 9000 years long, and the temperature-sensitive upper treeline chronology extends back to 5000 years. The ring width pattern of upper treeline bristlecone pine trees are strongly influenced by temperature variability at decadal to centennial scales. To infer a climate signal on annual scales, MXD is shown to be a better temperature proxy. Here, we present a preliminary Maximum Latewood Density (MXD) chronology of bristlecone pine to investigate the temperature signal in upper treeline and below. Maximum latewood density (MXD) from 24 dated cores (from various sites ranging from the upper treeline and below, oldest sample dates back to 776 AD) was determined with an X-ray CT toolchain. Ring and fibre angles were corrected and a MXD chronology was constructed. The resulting MXD chronology will be correlated to summer temperature. Future scanning will allow constructing a + 5000 year MXD chronology and could reveal the cooling effect of volcanic eruptions through this period.</p>

Blue Intensity for dendroclimatology: The BC blues: A case study from British Columbia, Canada

The Holocene ◽  
2014 ◽  
Vol 24 (11) ◽  
pp. 1428-1438 ◽  
Author(s):  
Rob Wilson ◽  
Rohit Rao ◽  
Miloš Rydval ◽  
Cheryl Wood ◽  
Lars-Åke Larsson ◽  
...  
Keyword(s):  
British Columbia ◽  
Tree Ring ◽  
Large Scale ◽  
Ring Width ◽  
Frequency Information ◽  
Maximum Latewood Density ◽  
Latewood Density ◽  
Summer Temperatures ◽  
Two Parameters ◽  
Blue Intensity

Maximum latewood density (MXD) is a strong proxy of summer temperatures. Despite this, there is a paucity of long MXD chronologies in the Northern Hemisphere, which limits large-scale tree-ring-based reconstructions of past temperature which are dominated by ring-width (RW) data – a weaker temperature proxy at inter-annual time-scales. This paucity likely results from the relative expense of measuring MXD and the lack of laboratories with the facilities to measure it. Herein, we test the ability of a relatively new, less expensive, tree-ring parameter, Blue Intensity (BI), to act as a surrogate parameter for MXD. BI was measured on Engelmann spruce samples from British Columbia where MXD had previously been measured to allow direct comparison between the two parameters. Signal strength analyses indicate that 8 MXD series were needed to acquire a robust mean chronology while BI needed 14. Utilising different detrending methods and parameter choices (RW + MXD vs RW + BI), a suite of reconstruction variants was developed. The explained variance from the regression modelling (1901–1995) of May–August maximum temperatures ranged from 52% to 55%. Validation tests over the earlier 1870–1900 period could not statistically distinguish between the different variants, although spectral analysis identified more lower frequency information extant in the MXD-based reconstructions – although this result was sensitive to the detrending method used. Ultimately, despite the MXD-based reconstruction explaining slightly more of the climatic variance, statistically robust reconstructions of past summer temperatures were also derived using BI. These results suggest that there is great potential in utilising BI for dendroclimatology in place of MXD data. However, more experimentation is needed to understand (1) how well BI can capture centennial and lower frequency information and (2) what biases may result from wood discolouration, either from species showing a distinct heartwood/sapwood boundary or from partly decayed sub-fossil samples.

scholarly journals Chemical de-staining and the delta correction for blue intensity measurements of stained lake subfossil trees

2020 ◽  
Author(s):  
Feng Wang ◽  
Dominique Arseneault ◽  
Étienne Boucher ◽  
Shulong Yu ◽  
Steeven Ouellet ◽  
...  
Keyword(s):  
Ethylenediaminetetraacetic Acid ◽  
Black Spruce ◽  
Temperature Reconstruction ◽  
Sodium Dithionite ◽  
Sodium Ascorbate ◽  
Maximum Latewood Density ◽  
Intensity Measurements ◽  
Latewood Density ◽  
Canadian Boreal Forest ◽  
Blue Intensity

Abstract. The stain of wood samples from lake subfossil trees (LSTs) is challenging the wide application of the blue intensity (BI) technique for millennial dendroclimatic reconstructions. In this study, we used seven chemical de-staining reagents to treat samples of subfossil black spruce (Picea mariana (Mill.) B.S.P.)) trees from two lakes in the eastern Canadian boreal forest. We subsequently compared latewood BI (LBI) and delta BI (DBI) time series along with conventional maximum latewood density (MXD) measured from the stained and de-stained samples. Results show that the stain of our samples is most likely caused by post-sampling oxidation of dissolved ferrous iron in lake sediments that penetrated into wood. Three reagents (ascorbic acid, sodium ascorbate and sodium dithionite all mixed with ethylenediaminetetraacetic acid) could remove > 90 % of Fe. However, even for the best chemical protocol, a discrepancy of about +2 °C compared to MXD data remains in the LBI-based temperature reconstruction due to incomplete de-staining. On the contrary, the simple mathematical delta correction, DBI is unaffected by Fe stain and shows very similar results compared to MXD data (r > 0.82) from annual to centennial timescales over the past ~ 360 years. This study underlines the difficulty of completely de-staining lake subfossil samples, while confirming the robustness of the DBI approach. DBI data measured from stained LSTs can be used to perform robust millennial temperature reconstructions.

Different maximum latewood density and blue intensity measurements techniques reveal similar results

2018 ◽  
Vol 49 ◽  
pp. 94-101 ◽  
Author(s):  
Ryszard J. Kaczka ◽  
Barbara Spyt ◽  
Karolina Janecka ◽  
Ilka Beil ◽  
Ulf Büntgen ◽  
...  
Keyword(s):  
Maximum Latewood Density ◽  
Intensity Measurements ◽  
Latewood Density ◽  
Blue Intensity

scholarly journals COVID-19 diagnosis from chest X-ray images using transfer learning: Enhanced performance by debiasing dataloader

2021 ◽  
Vol 29 (1) ◽  
pp. 19-36
Author(s):  
Çağín Polat ◽  
Onur Karaman ◽  
Ceren Karaman ◽  
Güney Korkmaz ◽  
Mehmet Can Balcı ◽  
...  
Keyword(s):  
Transfer Learning ◽  
Critical Time ◽  
Image Data ◽  
Mapping Method ◽  
Fine Tuning ◽  
Learning Stage ◽  
X Ray ◽  
Testing Dataset ◽  
X Ray Imaging ◽  
Chest X Ray

BACKGROUND: Chest X-ray imaging has been proved as a powerful diagnostic method to detect and diagnose COVID-19 cases due to its easy accessibility, lower cost and rapid imaging time. OBJECTIVE: This study aims to improve efficacy of screening COVID-19 infected patients using chest X-ray images with the help of a developed deep convolutional neural network model (CNN) entitled nCoV-NET. METHODS: To train and to evaluate the performance of the developed model, three datasets were collected from resources of “ChestX-ray14”, “COVID-19 image data collection”, and “Chest X-ray collection from Indiana University,” respectively. Overall, 299 COVID-19 pneumonia cases and 1,522 non-COVID 19 cases are involved in this study. To overcome the probable bias due to the unbalanced cases in two classes of the datasets, ResNet, DenseNet, and VGG architectures were re-trained in the fine-tuning stage of the process to distinguish COVID-19 classes using a transfer learning method. Lastly, the optimized final nCoV-NET model was applied to the testing dataset to verify the performance of the proposed model. RESULTS: Although the performance parameters of all re-trained architectures were determined close to each other, the final nCOV-NET model optimized by using DenseNet-161 architecture in the transfer learning stage exhibits the highest performance for classification of COVID-19 cases with the accuracy of 97.1 %. The Activation Mapping method was used to create activation maps that highlights the crucial areas of the radiograph to improve causality and intelligibility. CONCLUSION: This study demonstrated that the proposed CNN model called nCoV-NET can be utilized for reliably detecting COVID-19 cases using chest X-ray images to accelerate the triaging and save critical time for disease control as well as assisting the radiologist to validate their initial diagnosis.

Chest Imaging with Dual-Energy Subtraction Digital Tomosynthesis

1993 ◽  
Vol 34 (4) ◽  
pp. 346-350 ◽  
Author(s):  
S. Sone ◽  
T. Kasuga ◽  
F. Sakai ◽  
H. Hirano ◽  
K. Kubo ◽  
...  
Keyword(s):  
Low Voltage ◽  
Image Data ◽  
Dual Energy ◽  
Processing Unit ◽  
Digital Tomosynthesis ◽  
Chest Imaging ◽  
Layer Height ◽  
Pulmonary Lesions ◽  
X Ray ◽  
Energy Subtraction

Dual-energy subtraction digital tomosynthesis with pulsed X-ray and rapid kV switching was used to examine calcifications in pulmonary lesions. The digital tomosynthesis system used included a conventional fluororadiographic TV unit with linear tomographic capabilities, a high resolution videocamera, and an image processing unit. Low-voltage, high-voltage, and soft tissue subtracted or bone subtracted tomograms of any desired layer height were reconstructed from the image data acquired during a single tomographic swing. Calcifications, as well as their characteristics and distribution in pulmonary lesions, were clearly shown. The images also permitted discrimination of calcifications from dense fibrotic lesions. This technique was effective in demonstrating calcifications together with a solitary mass or disseminated nodules.

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