scholarly journals Model of mixed effects of height dependence on tree diameters in pine stands

2021 ◽  
Author(s):  
Н.Н. Дубенок ◽  
В.В. Кузьмичев ◽  
А.В. Лебедев
Keyword(s):  
Fixed Effects ◽  
Mixed Effects ◽  
Mixed Effects Model ◽  
Fixed Effects Model ◽  
Permanent Sample Plots ◽  
Diameter At Breast Height ◽  
Breast Height ◽  
Russian State ◽  
Pine Stands ◽  
The Relationship

Основными исходными данными для определения запаса служат результаты обмеров диаметров и высот деревьев. Но обмеры диаметров деревьев на высоте груди выполнить намного проще, чем обмеры высот, поэтому ограничиваются замерами высот 15–25 деревьев. Цель исследования – по материалам измерения модельных деревьев в сосновых древостоях выбрать наиболее адекватную простую модель, которая передает зависимость между высотой деревьев и диаметром на высоте груди. Объектом исследования послужили сосновые древостои искусственного происхождения на постоянных пробных площадях в Лесной опытной даче Российского государственного агарного университета – МСХА имени К.А. Тимирязева. В работе используются данные обмеров деревьев на 17 постоянных пробных площадях с 1934 по 2005 гг. Возраст древостоев на момент проведения измерений от 50 до 125 лет. По итогам проведения 77 перечетов массив данных составил 1157 наблюдений. И модель фиксированных эффектов, и модель смешанных эффектов адекватно описали зависимость между высотами и диаметрами деревьев в культурах сосны. Но, как и ожидалось, первая модель имеет худшие значения метрик качества по сравнению со второй. Модель со смешанными эффектами более точно предсказывает значения высот по сравнению с моделью фиксированных эффектов. Недостающие значения высот большого количества деревьев на участке можно вычислить более точно с помощью модели смешанных эффектов, а не применения модели фиксированных эффектов или использования только фиксированной части (средний отклик) модели смешанных эффектов. Применение разработанной модели должно ограничиваться только в тех условиях, к которым относятся экспериментальные материалы The main data for the stock of research results is the diameter of measurements and heights of trees. But measurements of the diameter at breast height are much easier to perform than measurements of heights, therefore, they are limited to measuring the heights of 15–25 trees. The aim of the study is to select the most adequate simple model based on the measurements of model trees in pine antiquities, which conveys the relationship between the height of trees and the diameter at breast height. The object of the study was pine stands of artificial origin on permanent test plots in the Forest Experimental Station Russian State Agararian University – Moscow Timiriazev Agricultural Academy. The work uses data from tree measurements on 17 permanent sample plots from 1934 to 2005. The age of the stands at the time of measurements was from 50 to 125 years. As a result of 77 enumerations, the data array amounted to 1157 observations. Both the fixed effects model and the mixed effects model adequately describe the relationship between heights and diameters of trees in pine stumps. But, as expected, the first model has worse quality metrics than the second. The mixed effects model more accurately predicts heights from the fixed effects model. The missing heights of a large number of trees on a site can be calculated accurately using mixed effects models, rather than using fixed effects models or using only a fixed portion (mean response) of the mixed effects model. The application of the developed model should be limited only in those conditions to which the experimental materials are applied.

A note on Griffing's models for the diallel cross

1975 ◽  
Vol 85 (3) ◽  
pp. 575-576 ◽  
Author(s):  
B. K. Thompson
Keyword(s):  
Fixed Effects ◽  
Diallel Cross ◽  
Mixed Effects ◽  
Mixed Effects Model ◽  
Fixed Effects Model

SUMMARYSome misconceptions concerning the application of Griffing's fixed effects model I and mixed effects model B are discussed.

scholarly journals An individual-tree linear mixed-effects model for predicting the basal area increment of major forest species in Southern Europe

2020 ◽  
Vol 29 (3) ◽  
pp. e019
Author(s):  
Lucio Di Cosmo ◽  
Diego Giuliani ◽  
Maria Michela Dickson ◽  
Patrizia Gasparini
Keyword(s):  
Forest Inventory ◽  
Basal Area ◽  
Ordinary Least Squares ◽  
Mixed Effects ◽  
Forest Growth ◽  
Mixed Effects Model ◽  
Basal Area Increment ◽  
Individual Tree ◽  
Diameter At Breast Height ◽  
Breast Height

Aims of the study. Assessment of growth is essential to support sustainability of forest management and forest policies. The objective of the study was to develop a species-specific model to predict the annual increment of tree basal area through variables recorded by forest surveys, to assess forest growth directly or in the context of more complex forest growth and yield simulation models.Area of the study. Italy.Material and methods. Data on 34638 trees of 31 different forest species collected in 5162 plots of the Italian National Forest Inventory were used; the data were recorded between 2004 and 2006. To account for the hierarchical structure of the data due to trees nested within plots, a two-level mixed-effects modelling approach was used.Main results. The final result is an individual-tree linear mixed-effects model with species as dummy variables. Tree size is the main predictor, but the model also integrates geographical and topographic predictors and includes competition. The model fitting is good (McFadden’s Pseudo-R2 0.536), and the variance of the random effect at the plot level is significant (intra-class correlation coefficient 0.512). Compared to the ordinary least squares regression, the mixed-effects model allowed reducing the mean absolute error of estimates in the plots by 64.5% in average.Research highlights. A single tree-level model for predicting the basal area increment of different species was developed using forest inventory data. The data used for the modelling cover 31 species and a great variety of growing conditions, and the model seems suitable to be applied in the wider context of Southern Europe.   Keywords: Tree growth; forest growth modelling; forest inventory; hierarchical data structure; Italy.Abbreviations used: BA - basal area; BAI – five-year periodic basal area increment; BALT - basal area of trees larger than the subject tree; BASPratio - ratio of subject tree species basal area to stand basal area; BASTratio - ratio of subject tree basal area to stand basal area; CRATIO - crown ratio; DBH – diameter at breast height ; DBH0– diameter at breast height corresponding to five years before the survey year; DBHt– diameter at breast height measured in the survey year; DI5 - five-year, inside bark, DBH increment; HDOM - dominant height; LULUCF - Land Use, Land Use Changes and Forestry; ME - mean error; MAE - mean absolute error; MPD - mean percent deviation; MPSE - mean percent standard error; NFI(s) - National Forest Inventory/ies; OLS - ordinary least squares regression; RMSE - root mean squared error; UNFCCC - United Nation Framework Convention on Climate Change.

Repeated Measurement Designs

1983 ◽  
Vol 32 (3-4) ◽  
pp. 153-168 ◽  
Author(s):  
A, C. Mukhopadhyay ◽  
Rita Saha
Keyword(s):  
Fixed Effects ◽  
Mixed Effects ◽  
Repeated Measurement ◽  
Mixed Effects Model ◽  
Fixed Effects Model

In the present paper Repeated Measurement Designs (RMD's) have been studied under mixed effects model, assuming unit effects to be random and most of the optimality results of RMD's proved under fixed effects model by Hedayat et. al (1978), Magda (1980) and Cheng et. al (1980) have been reestablished in the context of mixed effects model.

scholarly journals Comparison of Fixed- and Mixed-effects Approaches to Taper Modeling for Scots Pine in West Poland

Forests ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 975 ◽  
Author(s):  
Karol Bronisz ◽  
Michał Zasada
Keyword(s):  
Random Effects ◽  
Scots Pine ◽  
Fixed Effects ◽  
Mixed Effects ◽  
Mixed Effects Model ◽  
Fixed Effects Model ◽  
Validation Data ◽  
Data Set ◽  
Taper Model ◽  
Model Approach

Diameter measurements along the stem, which are the basis for taper models, usually have a hierarchical structure. Mixed-effects models, where fixed and random effects are distinguished, are a possible solution for this type of data. However, in order to fully absorb the potential of this method, random effects prediction, which requires additional measurements (diameter along stem), is recommended. This article presents a comparison of various fitting methods (mixed- and fixed-effects model approaches) of the variable-exponent taper model created by Kozak for determining the outside bark diameter along the stem and predicting the tree volume of Scots pine trees in west Poland. During the analysis, it was assumed that no additional measured data were available for practical use; therefore, for the mixed-effects model approach, fixed effects prediction without random effects was applied. Both fitting strategies were compared based on modeling and an independent validation data set. The comparison of mixed- and fixed-effects fitting strategies for the diameter along the stem indicated that the taper model fitted using the mixed-effects model approach better fit the data. Moreover, the error rate for the total tree volume prediction for the independent data set was lower for the mixed-effects model solution than for the fixed-effects one.

The relationship between migraine and infant colic: A systematic review and meta-analysis

Cephalalgia ◽  
2014 ◽  
Vol 35 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Amy A Gelfand ◽  
Peter J Goadsby ◽  
I Elaine Allen
Keyword(s):  
Systematic Review ◽  
Random Effects ◽  
Odds Ratio ◽  
Fixed Effects ◽  
Meta Analysis ◽  
Random Effects Model ◽  
Fixed Effects Model ◽  
Primary Analysis ◽  
Infant Colic ◽  
The Relationship

Context Infant colic is a common and distressing disorder of early infancy. Its etiology is unknown, making treatment challenging. Several articles have suggested a link to migraine. Objective The objective of this article was to perform a systematic review and, if appropriate, a meta-analysis of the studies on the relationship between infant colic and migraine. Data sources Studies were identified by searching PubMed and ScienceDirect and by hand-searching references and conference proceedings. Study selection For the primary analysis, studies specifically designed to measure the association between colic and migraine were included. For the secondary analysis, studies that collected data on colic and migraine but were designed for another primary research question were also included. Data extraction Data were abstracted from the original studies, through communication with study authors, or both. Two authors independently abstracted data. Main outcomes and measures The main outcome measure was the association between infant colic and migraine using both a fixed-effects model and a more conservative random-effects model. Results Three studies were included in the primary analysis; the odds ratio for the association between migraine and infant colic was 6.5 (4.6–8.9, p < 0.001) for the fixed-effects model and 5.6 (3.3–9.5, p = 0.004) for the random-effects model. In a sensitivity analysis wherein the study with the largest effect size was removed, the odds ratio was 3.6 (95% CI 1.7–7.6, p = 0.001) for both the fixed-effects model and random-effects model. Conclusions In this meta-analysis, infant colic was associated with increased odds of migraine. If infant colic is a migrainous disorder, this would have important implications for treatment. The main limitation of this meta-analysis was the relatively small number of studies included.

scholarly journals Does the Credit Cycle Have an Impact on Happiness?

2019 ◽  
Vol 17 (1) ◽  
pp. 183 ◽  
Author(s):  
Tinghui Li ◽  
Junhao Zhong ◽  
Mark Xu
Keyword(s):  
Fixed Effects ◽  
Well Being ◽  
Gdp Per Capita ◽  
Subjective Well Being ◽  
Fixed Effects Model ◽  
Credit Expansion ◽  
Transmission Channels ◽  
Credit Cycle ◽  
Per Capita ◽  
The Relationship

The 2008 international financial crisis triggered a heated discussion of the relationship between public health and the economic environment. We test the relationship between the credit cycle and happiness using the fixed effects model and explore the transmission channels between them by adding the moderating effect. The results show the following empirical regularities. First, the credit cycle has a negative correlation with happiness. This means that credit growth will reduce the overall happiness score in a country/region. Second, the transmission channels between the credit cycle and happiness are different during credit expansion and recession. Life expectancy and generosity can moderate the relationship between the credit cycle and happiness only during credit expansion. GDP per capita can moderate this relationship only during credit recession. Social support, freedom, and positive affect can moderate this relationship throughout the credit cycle. Third, the total impact of the credit cycle on happiness will become positive by the changes in the moderating effects. In general, we can improve subjective well-being if one of the following five conditions holds: (1) with the adequate support from the family and society, (2) with enough freedom, (3) with social generosity, (4) with a positive and optimistic outlook, and (5) with a high level of GDP per capita.

scholarly journals Governance and Financial Difficulties of Conventional Banks

2019 ◽  
Vol 2 (2) ◽  
pp. 121-134
Author(s):  
La Ode Sumail
Keyword(s):  
Fixed Effects ◽  
Large Scale ◽  
Lagrange Multiplier Test ◽  
Fixed Effects Model ◽  
Insider Ownership ◽  
Financial Difficulties ◽  
Private Banks ◽  
Conventional Banks ◽  
Relationship Of ◽  
The Relationship

This study examines the connection between governance, financial performance, and financial difficulties of 27 conventional private banks during the pe3riod of 2015-2018. In order to meet the accuracy of the model in the regression analysis, the Lagrange Multiplier test was previously performed so that the Fixed Effects model was chosen. The relationship of insider ownership with ROA tends to be in the shape of inversed-U and the relationship between institutional ownership and ROA is significantly positive. The relationship between ROA and financial difficulties is significantly negative. Older or established large scale banks tend to have high ROA. This happens because the greater the assets, the healthier the cash flow of the bank, so that the potential for return of asset is quite high and financial difficulties tend to be low or avoidable.

scholarly journals The relationship between debt and a firm’s performance: the impact of institutional factors

2019 ◽  
Vol 45 (9) ◽  
pp. 1272-1291 ◽  
Author(s):  
Rosa Forte ◽  
José Miguel Tavares
Keyword(s):  
Fixed Effects ◽  
Negative Relationship ◽  
Research Area ◽  
Institutional Framework ◽  
Market Regulation ◽  
Fixed Effects Model ◽  
Content Type ◽  
Macroeconomic Variables ◽  
The Impact ◽  
The Relationship

Purpose The purpose of this paper is to contribute to the existing literature on the relationship between debt and firms’ performance, by focusing on the influence of the institutional framework on this relationship and on the role of macroeconomic variables in explaining performance. Design/methodology/approach The present work is based on a large sample of 48,840 manufacturing firms from nine European countries covering the 2008–2013 period and uses a fixed effects model. Findings Results show that the impact of debt on a firm’s performance depends on the measure of debt (short-term debt positively affects a firm’s performance, whereas long-term debt presents a negative relationship) and that the institutional framework is indeed affecting the relationship between debt and a firm’s performance: the positive effect of debt on a firm’s performance tends to be higher the greater the “efficiency of the legal system” and the greater the “credit market regulation.” Macroeconomic variables also play a key role in explaining performance. Originality/value Unlike most of the existing studies, which focus only on the relationship between debt and firms’ performance in a single country, the present work uses a sample of firms from nine countries with the purpose of filling a research gap and bringing new empirical evidence to this research area.

scholarly journals The Negative Effect of Smartphone Use on Academic Performance May Be Overestimated: Evidence From a 2-Year Panel Study

2020 ◽  
Vol 31 (11) ◽  
pp. 1351-1362
Author(s):  
Andreas Bjerre-Nielsen ◽  
Asger Andersen ◽  
Kelton Minor ◽  
David Dreyer Lassen
Keyword(s):  
Academic Performance ◽  
Fixed Effects ◽  
Panel Study ◽  
Student Characteristics ◽  
Fixed Effects Model ◽  
Data Set ◽  
Course Characteristics ◽  
Negative Effect ◽  
Smartphone Use ◽  
The Relationship

In this study, we monitored 470 university students’ smartphone usage continuously over 2 years to assess the relationship between in-class smartphone use and academic performance. We used a novel data set in which smartphone use and grades were recorded across multiple courses, allowing us to examine this relationship at the student level and the student-in-course level. In accordance with the existing literature, our results showed that students’ in-class smartphone use was negatively associated with their grades, even when we controlled for a broad range of observed student characteristics. However, the magnitude of the association decreased substantially in a fixed-effects model, which leveraged the panel structure of the data to control for all stable student and course characteristics, including those not observed by researchers. This suggests that the size of the effect of smartphone usage on academic performance has been overestimated in studies that controlled for only observed student characteristics.

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