Landscape-level variability in the age underestimation of understory black spruce in the northern boreal forest of Quebec

2005 ◽  
Vol 35 (3) ◽  
pp. 633-642 ◽  
Author(s):  
Marc-André Parisien ◽  
Luc Sirois ◽  
Sylvain Parent
Keyword(s):  
Boreal Forest ◽  
Mixed Models ◽  
Black Spruce ◽  
Ground Level ◽  
Simple Linear Regression ◽  
Linear Regression Models ◽  
Growth Rings ◽  
Age Correction ◽  
The Relationship ◽  
Landscape Level

This study examines the variability of the potential aging error for saplings (height ≤1.5 m) of black spruce (Picea mariana (Mill.) B.S.P.) in mature fire-dominated stands (n = 14 stands) of the northern boreal forest of northwestern Quebec. Age underestimation was determined by counting the number of underground bud scars of saplings. The magnitude and variability of age underestimation was compared within and among stands. The relationship between corrected ages (the sum of age underestimation and the number of growth rings at ground level) and ground-level ages was strongly linear and was therefore described with simple linear regression models. To evaluate landscape-level variability in this relationship, the regressions were compared among stands using mixed models. Despite high variability in age underestimation at the stand level, the relationship between corrected and ground-level age was highly significant (p < 0.0001) for all stands except one. However, there were many significant statistical differences between these regressions, indicating high landscape-level variability. The magnitude of age underestimation was found to be highly site specific (means of 7–26 years), the phenomenon being more marked and variable in older stands. Given high landscape-level variability, age underestimation of understory black spruce saplings in northern boreal stands must be documented for every sampled stand to apply a valid age correction in studies that involve multiple stands.

scholarly journals Wet Heartwood Distribution in the Stem, Stump, and Root Wood of Black Spruce in the Quebec Boreal Forest, Canada

2005 ◽  
Vol 22 (1) ◽  
pp. 12-18 ◽  
Author(s):  
Cornelia Krause ◽  
Réjean Gagnon
Keyword(s):  
Moisture Content ◽  
Boreal Forest ◽  
Black Spruce ◽  
Ground Level ◽  
Stem Height ◽  
High Moisture ◽  
Stem Base ◽  
Maximum Value ◽  
Crown Shape ◽  
Field Measure

Abstract Wet heartwood has been studied since the beginning of the 20th century. The present work focused on wet heartwood of 44 black spruces (Picea mariana (Mill.) B.S.P.) from boreal forest swampy sites Quebec, Canada. Trees were studied to characterize their tree crown shape, quickly identify them in the field, measure their moisture content, establish their moisture content distribution pattern, evaluate the wet heartwood volume inside their stem, and find the possibility of water entrance in this species. Black spruces with wet heartwood were characterized by a typical tree shape with a small number of living branches, short branches, and a clump of green needles at the top of the tree. The wet heartwood was characterized by high moisture content at the stem base and decreased with stem height. Wet heartwood was observed as high as 5 m above stem base for trees around 10.5 m in height. Moisture content of sapwood along the stem varied from 81 to 161%, whereas in dry heartwood, it was around 43% but reached more than 100% in the wet heartwood. Wet heartwood volume in the first 3.25 m of black spruce stems averaged 13% with variations between 2 and 35% per study site. Twelve stumps had wet heartwood moisture contents reaching 143% or higher. Moisture content of wet heartwood in root sections closest to the stump varied along a gradient: lower or absent at ground level and increasing with depth up to a maximum value before decreasing again. North. J. Appl. For. 22(1):12–18.

Prediction of throughfall quantities under different forest stands

1982 ◽  
Vol 12 (3) ◽  
pp. 474-481 ◽  
Author(s):  
M. K. Mahendrappa ◽  
D. G. O. Kingston
Keyword(s):  
Regression Models ◽  
Balsam Fir ◽  
Simple Linear Regression ◽  
Linear Regression Models ◽  
Quantitative Distribution ◽  
Rain Gauges ◽  
Case Application ◽  
The Difference ◽  
And Control ◽  
The Relationship

The quantitative distribution of throughfall in fertilizer-treated and control plots under six softwood and three hardwood stands and rainfall in open areas close to these stands were intensively measured during 1977–1978. Standard rain gauges and improvised funnel-type collectors were used for measuring both throughfall and rainfall in the open. The improvised funnel-type collectors with an orifice smaller than that of the standard rain gauges were found to be suitable for accurately measuring quantities of both open rainfall and throughfall. Simple linear regression models of the form Y = b − a were sufficient to predict throughfall quantities (Y) based on rainfall (X) measurements. The relationship between the quantities of throughfall and rainfall was highly significant in each case. Application of urea at a rate of 225 kg N ha−1 did not affect either the slope (b) or the elevation (a) of the relationship. No significant differences were found between the relationships calculated for 1977 and 1978 for any species except balsam fir (Abiesbalsamea (L.) Mill) and larch (Lurixlaricina (Du Roi) K. Koch). The difference for balsam fir was probably a result of extensive defoliation by the spruce budworm (Choristoneurafumiferana (Clem.)). In most cases, values of the slopes (b) of the models for the different species were not significantly different. The nine species did, however, differ significantly from one another in terms of the minimum quantity of rain (a/b) that must fall before throughfall was measurable in the collectors.

Spatiotemporal variation in black spruce cone and seed crops along a boreal forest - tree line transect

2000 ◽  
Vol 30 (6) ◽  
pp. 900-909 ◽  
Author(s):  
Luc Sirois
Keyword(s):  
Boreal Forest ◽  
Black Spruce ◽  
Forest Tree ◽  
Line Transect ◽  
Tree Line ◽  
Cone Production ◽  
Forest Sites ◽  
Seed Crops ◽  
The Relationship ◽  
Filled Seeds

To assess the relationship between the regenerative potential of black spruce (Picea mariana (Mill.) BSP) and the latitudinal and thermal gradients, the cone crop was monitored in the same selection of trees during the 1989-1995 period in the northern boreal forest (sites A, n = 49, and B, n = 48), in the southern forest-tundra transition zone (site C, n = 35), and at the tree line (site D, n = 21). The size of the cone crop, the amount of seeds extracted per cone, along with the percentages of filled seed and germination were measured on each tree. There was no south to north trend associated with the cone crop. The cone crop at tree line was not significantly lower than in either of the southerly sites in six of the seven observed years. The number of seeds extracted per cone, the percentage of filled seeds, and the germination of filled seeds showed significant decrease northward according to year. Although there was no significant relationship between temperature and the cone production over the study area, the percentages of filled seeds and germination were significantly (0.51 [Formula: see text] r2 [Formula: see text] 0.44; p < 0.001) associated with the regional variation in heat sum.

scholarly journals Snag use by Foraging Black-Backed Woodpeckers (Picoides Arcticus) in a Recently Burned Eastern Boreal Forest

The Auk ◽  
2003 ◽  
Vol 120 (2) ◽  
pp. 505-511 ◽  
Author(s):  
Antoine Nappi ◽  
Pierre Drapeau ◽  
Jean-François Giroux ◽  
Jean-Pierre L. Savard
Keyword(s):  
Boreal Forest ◽  
Boreal Forests ◽  
Black Spruce ◽  
High Quality ◽  
Salvage Logging ◽  
Northeastern North America ◽  
Picoides Arcticus ◽  
One Year ◽  
The Relationship ◽  
Wood Boring

Abstract We studied snag use for foraging by Black-backed Woodpeckers (Picoides arcticus) one year after a fire in an eastern black spruce (Picea mariana) boreal forest in Quebec, Canada. We searched for signs of foraging (bark flaking and excavation holes) by Black-backed Woodpeckers on 6,536 snags sampled in 56 plots located in portions of the burned forest that had not been salvage logged. A logistic regression model was developed based on the presence or absence of foraging signs. Results showed that Black-backed Woodpeckers used larger snags that were less deteriorated by fire (qualified as high-quality snags). Direct field observations of individuals foraging on 119 snags also indicated that used snags corresponded to those of high predicted quality. Finally, we assessed the relationship between food availability and snag characteristics by measuring the density of wood-boring beetle larvae holes on 30 snags of different size and deterioration classes. High-quality snags contained higher prey densities (wood-boring beetle holes) than smaller and more deteriorated snags. We recommend that forest blocks characterized by large and less deteriorated trees be preserved from salvage logging in recently burned boreal forests in northeastern North America.

The relationship between site and tree characteristics and the presence of wet heartwood in black spruce in the boreal forest of Quebec, Canada

2006 ◽  
Vol 36 (6) ◽  
pp. 1519-1526 ◽  
Author(s):  
Cornelia Krause ◽  
Réjean Gagnon
Keyword(s):  
Boreal Forest ◽  
Black Spruce ◽  
Significant Proportion ◽  
Organic Soil ◽  
Average Height ◽  
Groundwater Levels ◽  
Site Characteristics ◽  
Content Classification ◽  
Study Sites ◽  
The Relationship

Wet heartwood in black spruce (Picea mariana (Mill.) BSP) causes considerable problems during the drying process. Forest companies try to avoid harvesting stands with wet heartwood, but no relationship has been yet established between the incidence of wet heartwood and tree or site characteristics. To characterize areas containing a significant proportion of black spruce affected by wet heartwood, a total of 635 black spruce trees were sampled in eighteen 400 m2 study plots under management in the central boreal forest of Quebec. A total of 18 study sites were analysed and classified as wet, intermediate, or dry, based on the proportion of individuals with wet heartwood. Thirteen of the study sites were classified as wet, two as intermediate, and three as dry. The average age calculated for trees on wet sites was significantly (p = 0.0001) higher than that of the other two classes, whereas growth rate was significantly lower on wet sites. No difference was noted in the average height or diameter of the individuals from all three classes. The wet sites contained organic soil, whereas Podzols characterized two of the three dry study sites. An additional sampling of black spruce (n = 509) revealed a significant relationship between the groundwater level and heartwood moisture content classification (i.e., dry, intermediate, or wet). Trees in the dry heartwood class grew on sites with the lowest groundwater levels (p = 0.002) compared with trees in the wet or intermediate classes.

scholarly journals Identifying Molecular Features Associated with Psychoneurological Symptoms in Women with Breast Cancer Using Multivariate Mixed Models

2015 ◽  
Vol 14s2 ◽  
pp. CIN.S17276 ◽  
Author(s):  
Qing Zhou ◽  
Colleen Jackson-Cook ◽  
Debra Lyon ◽  
Robert Perera ◽  
Kellie J. Archer
Keyword(s):  
Breast Cancer ◽  
Mixed Models ◽  
Linear Regression Models ◽  
Multivariate Models ◽  
Cpg Sites ◽  
Molecular Features ◽  
Psychoneurological Symptoms ◽  
Anxiety Depression ◽  
The Relationship ◽  
Compare And Contrast

Breast cancer (BC) is the second most common cancer among women. Research shows many women with BC experience anxiety, depression, and stress (ADS). Epigenetics has recently emerged as a potential mechanism for the development of depression. 1 Although there are growing numbers of research studies indicating that epigenetic changes are associated with ADS, there is currently no evidence that this association is present in women with BC. The goal of this study was to identify high-throughput methylation sites (CpG sites) that are associated with three psychoneurological symptoms (ADS) in women with BC. Traditionally, univariate models have been used to examine the relationship between methylation sites and each psychoneurological symptom; nevertheless, ADS can be treated as a cluster of related symptoms and included together in a multivariate linear model. Hence, an overarching goal of this study is to compare and contrast univariate and multivariate models when identifying methylation sites associated with ADS in women with BC. When fitting separate linear regression models for each ADS scale, 3 among 285,173 CpG sites tested were significantly associated with depression. Two significant CpG sites are located on their respective genes FAM101A and FOXJ1, and the third site cannot be mapped to any known gene at this time. In contrast, the multivariate models identified 8,535 ADS-related CpG sites. In conclusion, when analyzing correlated psychoneurological symptom outcomes, multivariate models are more powerful and thus are recommended.

scholarly journals Identifying change points for linear mixed models: a solution through evolutionary algorithms

Respuestas ◽  
2020 ◽  
Vol 25 (S2) ◽  
pp. 69-78
Author(s):  
Ehidy Karime Garcia-Cruz ◽  
Hugo Fernando Castro-Silva ◽  
Juan Carlos Salazar-Uribe
Keyword(s):  
Linear Regression ◽  
Evolutionary Algorithms ◽  
Loss Function ◽  
Mixed Models ◽  
Linear Mixed Models ◽  
Risk Function ◽  
Target Population ◽  
Change Points ◽  
Simple Linear Regression ◽  
The Relationship

Mathematical models are used to describe the relationship between two or more variables or features over the target population. Statistically, Simple Linear regression model has been extensively applied and the properties of their estimators are well known. However, this kind of model is not correctly applied in most cases, such as a longitudinal setting. Linear mixed models (LMMs) are useful when the measurements have been done over a specific interval of time. One of the most important assumptions, on both models, has been established as that the model holds for the whole data. In latter case, we could find one or several points which the function changes into. This proposal allows us to estimate the points where the model changes by minimizing a specific risk function or a loss function associated with the fitted model.

Camouflaging in non-autistic adults is associated with poorer mental health

2019 ◽  
Author(s):  
Mark Somerville ◽  
Sarah E. MacPherson ◽  
Sue Fletcher-Watson
Keyword(s):  
Mental Health ◽  
Executive Function ◽  
Autistic Traits ◽  
Self Report ◽  
Linear Regression Models ◽  
Mental Health Symptoms ◽  
Health Symptoms ◽  
Autistic People ◽  
Autistic Adults ◽  
The Relationship

Camouflaging is a frequently reported behaviour in autistic people, which entails the use of strategies to compensate for and mask autistic traits in social situations. Camouflaging is associated with poor mental health in autistic people. This study examined the manifestation of camouflaging in a non-autistic sample, examining the relationship between autistic traits, camouflaging, and mental health. In addition, the role of executive functions as a mechanism underpinning camouflaging was explored. Sixty-three non-autistic adults completed standardised self-report questionnaires which measured: autistic traits, mental health symptoms, and camouflaging behaviours. In addition, a subset (n=51) completed three tests of executive function measuring inhibition, working memory, and set-shifting. Multiple linear regression models were used to analyse data. Results indicated that autistic traits are not associated with mental health symptoms when controlling for camouflaging, and camouflaging predicted increased mental health symptoms. Camouflaging did not correlate with any measure of executive function. These findings have implications for understanding the relationship between autistic traits and mental health in non-autistic people and add to the growing development of theory and knowledge about the mechanism and effects of camouflaging.

scholarly journals Assessing Wildfire Burn Severity and Its Relationship with Environmental Factors: A Case Study in Interior Alaska Boreal Forest

2021 ◽  
Vol 13 (10) ◽  
pp. 1966
Author(s):  
Christopher W Smith ◽  
Santosh K Panda ◽  
Uma S Bhatt ◽  
Franz J Meyer ◽  
Anushree Badola ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Ground Truth ◽  
Burn Severity ◽  
Classification Methods ◽  
Spectral Indices ◽  
Ground Truth Data ◽  
Burn Scar ◽  
Interior Alaska ◽  
Remote Sensing Methods ◽  
The Relationship

In recent years, there have been rapid improvements in both remote sensing methods and satellite image availability that have the potential to massively improve burn severity assessments of the Alaskan boreal forest. In this study, we utilized recent pre- and post-fire Sentinel-2 satellite imagery of the 2019 Nugget Creek and Shovel Creek burn scars located in Interior Alaska to both assess burn severity across the burn scars and test the effectiveness of several remote sensing methods for generating accurate map products: Normalized Difference Vegetation Index (NDVI), Normalized Burn Ratio (NBR), and Random Forest (RF) and Support Vector Machine (SVM) supervised classification. We used 52 Composite Burn Index (CBI) plots from the Shovel Creek burn scar and 28 from the Nugget Creek burn scar for training classifiers and product validation. For the Shovel Creek burn scar, the RF and SVM machine learning (ML) classification methods outperformed the traditional spectral indices that use linear regression to separate burn severity classes (RF and SVM accuracy, 83.33%, versus NBR accuracy, 73.08%). However, for the Nugget Creek burn scar, the NDVI product (accuracy: 96%) outperformed the other indices and ML classifiers. In this study, we demonstrated that when sufficient ground truth data is available, the ML classifiers can be very effective for reliable mapping of burn severity in the Alaskan boreal forest. Since the performance of ML classifiers are dependent on the quantity of ground truth data, when sufficient ground truth data is available, the ML classification methods would be better at assessing burn severity, whereas with limited ground truth data the traditional spectral indices would be better suited. We also looked at the relationship between burn severity, fuel type, and topography (aspect and slope) and found that the relationship is site-dependent.

scholarly journals Factors Influencing Creatine Kinase Response in Youth National Team Soccer Players

2021 ◽  
pp. 194173812199938
Author(s):  
Gabor Schuth ◽  
Gyorgy Szigeti ◽  
Gergely Dobreff ◽  
Peter Revisnyei ◽  
Alija Pasic ◽  
...  
Keyword(s):  
Creatine Kinase ◽  
Prediction Models ◽  
Soccer Players ◽  
Linear Regression Models ◽  
Level Of Evidence ◽  
Internal Load ◽  
Youth Soccer ◽  
National Team ◽  
Weekly Training ◽  
The Relationship

Background: Previous studies have examined the relationship between external training load and creatine kinase (CK) response after soccer matches in adults. This study aimed to build training- and match-specific CK prediction models for elite youth national team soccer players. Hypothesis: Training and match load will have different effects on the CK response of elite youth soccer players, and there will be position-specific differences in the most influential external and internal load parameters on the CK response. Study Design: Prospective cohort study. Level of Evidence: Level 4. Methods: Forty-one U16-U17 youth national team soccer players were measured over an 18-month period. Training and match load were monitored with global positioning system devices. Individual CK values were measured from whole blood every morning in training camps. The dataset consisted of 1563 data points. Clustered prediction models were used to examine the relationship between external/internal load and consecutive CK changes. Clusters were built based on the playing position and activity type. The performance of the linear regression models was described by the R2 and the root-mean-square error (RMSE, U/L for CK values). Results: The prediction models fitted similarly during games and training sessions ( R2 = 0.38-0.88 vs 0.6-0.77), but there were large differences based on playing positions. In contrast, the accuracy of the models was better during training sessions (RMSE = 81-135 vs 79-209 U/L). Position-specific differences were also found in the external and internal load parameters, which best explained the CK changes. Conclusion: The relationship between external/internal load parameters and CK changes are position specific and might depend on the type of session (training or match). Morning CK values also contributed to the next day’s CK values. Clinical Relevance: The relationship between position-specific external/internal load and CK changes can be used to individualize postmatch recovery strategies and weekly training periodization with a view to optimize match performance.

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