Postfire seed rain of black spruce, a semiserotinous conifer, in forests of interior Alaska

2009 ◽  
Vol 39 (8) ◽  
pp. 1575-1588 ◽  
Author(s):  
Jill Johnstone ◽  
Leslie Boby ◽  
Emily Tissier ◽  
Michelle Mack ◽  
Dave Verbyla ◽  
...  
Keyword(s):  
Structural Equation ◽  
Black Spruce ◽  
Fire Severity ◽  
Seed Viability ◽  
Basal Area ◽  
Seed Rain ◽  
Equation Modeling ◽  
Viable Seed ◽  
Interior Alaska ◽  
Total Seed

The availability of viable seed can act as an important constraint on plant regeneration following disturbance. This study presents data on seed quantity and quality for black spruce ( Picea mariana (Mill.) B.S.P.), a semiserotinous conifer that dominates large areas of North American boreal forest. We sampled seed rain and viability for 2 years after fire (2005–2007) in 39 sites across interior Alaska that burned in 2004. All sites were dominated by black spruce before they burned. Structural equation modeling was used to assess the relative importance of prefire spruce abundance, topography effects, canopy fire severity, and distance to unburned stands in explaining variations in black spruce seed rain. Prefire basal area of spruce that remained standing after fire was a significant predictor of total seed rain, but seed viability was more strongly related to site elevation, canopy fire severity, and distances to unburned stands. Although positive relations between tree basal area and the size of the aerial seed bank may place a first constraint on seed availability, accurate prediction of postfire viable seed rain for serotinous conifers also requires consideration of the effects of abiotic stress and canopy fire severity on seed viability.

Black Spruce Fuel Weights and Biomass in Two Interior Alaska Stands

1973 ◽  
Vol 3 (2) ◽  
pp. 304-311 ◽  
Author(s):  
Richard J. Barney ◽  
Keith Van Cleve
Keyword(s):  
Black Spruce ◽  
Basal Area ◽  
Total Biomass ◽  
Biomass Distribution ◽  
Dead Tree ◽  
Interior Alaska ◽  
Moss Layer

This study reports the fuel weight and biomass distribution in a 51-year-old lowland and a 55-year-old upland black spruce (Piceamariana [Mill.] B.S.P.) stand in interior Alaska. Biomass distribution is shown for overstory, standing and down dead tree components, herbaceous understory, and the moss layer. The lowland stand contained over 11000 stems/acre (27170 stems/ha) and 82 ft2 of basal area per acre (18.8 m2 of basal area per hectare), and the upland stand contained 6000 stems/acre (14820 stems/ha) and 96 ft2 of basal area per acre (22.0 m2 of basal area per hectare). Moss layers contributed 54.6 and 45.5 t/acre (120.1 and 100.1 metric t/ha) to biomass totals in the lowland and upland sites, respectively. Total biomass was 64.7 t/acre (142.3 metric t/ha) in the lowland site and 58.0 t/acre (127.6 metric t/ha) in the upland site.

Reduction of black spruce seed bank by spruce budworm infestation compromises postfire stand regeneration

2005 ◽  
Vol 35 (7) ◽  
pp. 1686-1696 ◽  
Author(s):  
Martin Simard ◽  
Serge Payette
Keyword(s):  
Seed Bank ◽  
Black Spruce ◽  
Reproductive Potential ◽  
Basal Area ◽  
Spruce Budworm ◽  
Stand Age ◽  
Viable Seed ◽  
Eastern Canada ◽  
Postfire Regeneration ◽  
Fire Disturbances

In the southern boreal forest of eastern Canada, black spruce (Picea mariana (Mill.) BSP) is subjected to both defoliating insect and fire disturbances. As black spruce depends on its aerial seed bank for postfire regeneration, reduction of cone crop during a spruce budworm (Choristoneura fumiferana (Clem.)) outbreak opens a vulnerability window during which stand regeneration could be hindered in the event of a fire. To assess the long-term effect of spruce budworm outbreak on black spruce reproductive potential, cone production and viable seed bank were estimated using cone crop surveys and germination trials in black spruce – lichen woodland stands that sustained different levels of defoliation during the 1980s. Black spruce cone crop was significantly related to the defoliation history of the stands (R2 = 0.89), but not to stand age, basal area, or tree density. Black spruce stands damaged by severe defoliation showed a smaller number of cones, a higher incidence of insect-damaged cones, and a viable seed bank 3 to 17 times smaller than a lightly defoliated stand. The vulnerability window for black spruce regeneration following a spruce budworm outbreak may be as long as 20 years in the study area because black spruce seed bank in heavily defoliated stands has not yet replenished. Our work supports conclusions from stand reconstruction studies that suggest closed-crown spruce–moss stands convert to open lichen woodlands as a result of weak postfire regeneration caused by successive insect and fire disturbances.

Age and size effects on seed productivity of northern black spruce

2013 ◽  
Vol 43 (6) ◽  
pp. 534-543 ◽  
Author(s):  
Jayme N. Viglas ◽  
Carissa D. Brown ◽  
Jill F. Johnstone
Keyword(s):  
Boreal Forest ◽  
Seed Production ◽  
Fire Regime ◽  
Black Spruce ◽  
Seed Viability ◽  
Basal Area ◽  
Yukon Territory ◽  
Stand Age ◽  
Seed Productivity ◽  
Cone Production

Slow-growing conifers of the northern boreal forest may require several decades to reach reproductive maturity, making them vulnerable to increases in disturbance frequency. Here, we examine the relationship between stand age and seed productivity of black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.) in Yukon Territory and Alaska. Black spruce trees were aged and surveyed for cone production and seed viability across 30 even-aged stands ranging from 12 to 197 years old. Logistic regression indicated that individual trees had a ∼50% probability of producing cones by age 30 years, which increased to 90% by age 100 years. Cone and seed production increased steadily with age or basal area at both the tree and stand level, with no evidence of declining seed production in trees older than 150 years. Using published seed:seedling ratios, we estimated that postfire recruitment will be limited by seed availability in stands for up to 50 years (on high-quality seedbeds) to 150 years (low-quality seedbeds) after fire. By quantifying these age and seed productivity relationships, we can improve our ability to predict the sensitivity of conifer seed production to a range of disturbance frequencies and thus anticipate changes in boreal forest resilience to altered fire regime.

A Psychometric Study of the Quality Perception Questionnaire

2012 ◽  
Vol 71 (2) ◽  
pp. 101-106 ◽  
Author(s):  
Raffaele Cioffi† ◽  
Anna Coluccia ◽  
Fabio Ferretti ◽  
Francesca Lorini ◽  
Aristide Saggino ◽  
...  
Keyword(s):  
Structural Equation ◽  
Factor Model ◽  
Equation Modeling ◽  
Fit Indices ◽  
Quality Perception ◽  
Italian Survey ◽  
Confirmatory Factor ◽  
Instrument Measuring ◽  
Hospital Structures

The present paper reexamines the psychometric properties of the Quality Perception Questionnaire (QPQ), an Italian survey instrument measuring patients’ perceptions of the quality of a recent hospital admission experience, in a sample of 4400 patients (Mage = 56.42 years; SD = 19.71 years, 48.8% females). The 14-item survey measures four factors: satisfaction with medical doctors, nursing staff, auxiliary staff, and hospital structures. First, we tested two models using a confirmatory factor analysis (structural equation modeling): a four orthogonal factor and a four oblique factor model. The SEM fit indices and the χ² difference suggested the acceptance of the second model. We then did a simulation using a bootstrap with 1000 replications. Results confirmed the four oblique factor solution. Third, we tested whether there were significant differences with respect to age or sex. The multivariate general linear model showed no significant differences in the factors with respect to sex or age.

Suicide Risk Among College Student

Crisis ◽  
2015 ◽  
Vol 36 (6) ◽  
pp. 416-423 ◽  
Author(s):  
Richard Shadick ◽  
Faedra Backus Dagirmanjian ◽  
Baptiste Barbot
Keyword(s):  
Sexual Minority ◽  
Students Of Color ◽  
Structural Equation ◽  
Suicide Risk ◽  
Equation Modeling ◽  
First Year ◽  
Chi Square ◽  
First Year College ◽  
Marginalized Groups ◽  
First Year College Students

Abstract. Background: Research on young adults in the general population has identified a relationship between sexual minority identification and risk for suicide. Differential rates of suicidal ideation and attempts have also been found across racial and ethnic groups. Aims: This study examined risk for suicide among university students, based on membership in one or more marginalized groups (sexual minority and racial minority identification). Method: Data were collected from first-year college students (N = 4,345) at an urban university. Structural equation modeling was employed to model a suicidality construct, based on which a "risk for suicide" category system was derived. Chi-square and logistic regression analyses were then conducted to estimate the relationship between the background variables of interest and suicide risk. Results: Students who identified as lesbian, gay, or bisexual (LGB) were associated with higher suicide risk than their heterosexual peers. Students of color were slightly less at risk than their heterosexual peers. However, LGB students of color were associated with elevated suicide risk relative to heterosexual peers. Conclusion: Results indicate that belonging to multiple marginalized groups may increase one's risk for suicide, though these effects are not simply additive. Findings highlight the complexity of the intersection between marginalized identities and suicidality.

Low Self-Control of Emotions as an Antecedent of Self-Reported Physical Symptoms: A Longitudinal Perspective

2001 ◽  
Vol 6 (1) ◽  
pp. 26-35 ◽  
Author(s):  
Marja Kokkonen ◽  
Lea Pulkkinen ◽  
Taru Kinnunen
Keyword(s):  
Structural Equation ◽  
Negative Emotions ◽  
Physical Symptoms ◽  
Self Control ◽  
Personality Characteristics ◽  
Equation Modeling ◽  
Eysenck Personality Questionnaire ◽  
Positive Direction ◽  
Data Collections ◽  
Low Self Control

The study was part of the Jyväskylä Longitudinal Study of Personality and Social Development, underway since 1968, in which children's low self-control of emotions was studied using teacher ratings at age 8 in terms of inattentiveness, shifting moods, aggression, and anxiety. The study was based on data from 112 women and 112 men who participated in the previous data collections at ages 8, 27, and 36. At age 27, the participants had been assessed in Neuroticism (N) using the Eysenck Personality Questionnaire , and at age 36 they filled in several inventories measuring, among others, conscious and active attempts to repair negative emotions in a more positive direction as well as physical symptoms. The present study used structural equation modeling to test the hypothesis that personality characteristics indicating low self-control of emotions at ages 8 and 27 are antecedents of self-reported physical symptoms at age 36; and that this relationship is indirect, mediated by attempts to repair negative emotions in a more positive direction. The findings showed, albeit for men only, that inattentiveness at age 8 was positively related to self-reported physical symptoms at age 36 via high N at age 27 and low attempts to repair negative emotions at age 36. Additionally, N at age 27 was directly linked to self-reported physical symptoms at age 36. The mediation of an active attempt to repair negative emotions was not found for women. Correlations revealed, however, that shifting moods and aggression in girls were antecedents of self-reported physical symptoms in adulthood, particularly, pain and fatigue.

Validating the Factor Structure of the Stigma of Suicide Scale–Short Form Spanish Version Among Healthcare Students

Crisis ◽  
2020 ◽  
pp. 1-5
Author(s):  
Ruthmarie Hernández-Torres ◽  
Paola Carminelli-Corretjer ◽  
Nelmit Tollinchi-Natali ◽  
Ernesto Rosario-Hernández ◽  
Yovanska Duarté-Vélez ◽  
...  
Keyword(s):  
Factor Structure ◽  
Structural Equation ◽  
Short Form ◽  
Small Sample Size ◽  
Small Sample ◽  
Spanish Version ◽  
Equation Modeling ◽  
Cross Sectional ◽  
Healthcare Students ◽  
Spanish Speaking

Abstract. Background: Suicide is a leading cause of death among Spanish-speaking individuals. Suicide stigma can be a risk factor for suicide. A widely used measure is the Stigma of Suicide Scale-Short Form (SOSS-SF; Batterham, Calear, & Christensen, 2013 ). Although the SOSS-SF has established psychometric properties and factor structure in other languages and cultural contexts, no evidence is available from Spanish-speaking populations. Aim: This study aims to validate a Spanish translation of the SOSS-SF among a sample of Spanish-speaking healthcare students ( N = 277). Method: We implemented a cross-sectional design with quantitative techniques. Results: Following a structural equation modeling approach, a confirmatory factor analysis (CFA) supported the three-factor model proposed by Batterham and colleagues (2013) . Limitations: The study was limited by the small sample size and recruitment by availability. Conclusion: Findings suggest that the Spanish version of the SOSS-SF is a valid and reliable tool with which to examine suicide stigma among Spanish-speaking populations.

Risk Factors and Mediators of Suicidal Ideation Among Korean Adolescents

Crisis ◽  
2018 ◽  
Vol 39 (1) ◽  
pp. 4-12 ◽  
Author(s):  
Yi Jin Kim ◽  
Sung Seek Moon ◽  
Jang Hyun Lee ◽  
Joon Kyung Kim
Keyword(s):  
High School Students ◽  
Suicidal Ideation ◽  
Structural Equation ◽  
Equation Modeling ◽  
Outcome Variable ◽  
Suicidal Behaviors ◽  
Thwarted Belongingness ◽  
Perceived Burdensomeness ◽  
Korean Adolescents ◽  
Related Stress

Abstract. Background: A significant number of Korean adolescents have suicidal ideations and it is more prevalent among adolescents than any other age group in Korea. Aims: This study was conducted to attain a better understanding of the contributing factors to suicidal ideation among Korean adolescents. Method: We recruited 569 high school students in Grades 10 and 11 in Pyeongtaek, Korea. The Beck Scale for Suicidal Ideation was used to measure suicidal ideation as the outcome variable. The Interpersonal Needs Questionnaire, the Beck Hopelessness Scale, the School Related Stress Scale, the Olweus Bully/Victim Questionnaire, and the Youth Risk Behavior Surveillance questions were used to measure thwarted belongingness and perceived burdensomeness, hopelessness, school-related stress, bullying, and previous suicidal behaviors, respectively. Data analyses included descriptive statistics and structural equation modeling. Results: The findings suggest that perceived burdensomeness, hopelessness, school-related stress, and previous suicidal behaviors have significant direct effects on suicidal ideation. Hopelessness fully mediated the relation between thwarted belongingness and suicidal ideation, and partially mediated between perceived burdensomeness, school-related stress, and suicidal ideation. Conclusion: These findings provide more specific directions for a multidimensional suicide prevention program in order to be successful in reducing suicide rates among Korean adolescents.

Sign in / Sign up

Export Citation Format

Share Document