The Design of Experiments: Statistical Principles for Practical Application.

INTRODUCTION BINOMIAL DATA Challenger Disaster Example Binomial Regression Model Inference Tolerance Distribution Interpreting Odds Prospective and Retrospective Sampling Choice of Link Function Estimation Problems Goodness of Fit Prediction and Effective Doses Overdispersion Matched Case-Control Studies COUNT REGRESSION Poisson Regression Rate Models Negative Binomial CONTINGENCY TABLES Two-by-Two Tables Larger Two-Way Tables Matched Pairs Three-Way Contingency Tables Ordinal Variables MULTINOMIAL DATA Multinomial Logit Model Hierarchical or Nested Responses Ordinal Multinomial Responses GENERALIZED LINEAR MODELS GLM Definition Fitting a GLM Hypothesis Tests GLM Diagnostics OTHER GLMS Gamma GLM Inverse Gaussian GLM Joint Modeling of the Mean and Dispersion Quasi-Likelihood RANDOM EFFECTS Estimation Inference Predicting Random Effects Blocks as Random Effects Split Plots Nested Effects Crossed Effects Multilevel Models REPEATED MEASURES AND LONGITUDINAL DATA Longitudinal Data Repeated Measures Multiple Response Multilevel Models MIXED EFFECT MODELS FOR NONNORMAL RESPONSES Generalized Linear Mixed Models Generalized Estimating Equations NONPARAMETRIC REGRESSION Kernel Estimators Splines Local Polynomials Wavelets Other Methods Comparison of Methods Multivariate Predictors ADDITIVE MODELS Additive Models Using the gam Package Additive Models Using mgcv Generalized Additive Models Alternating Conditional Expectations Additivity and Variance Stabilization Generalized Additive Mixed Models Multivariate Adaptive Regression Splines TREES Regression Trees Tree Pruning Classification Trees NEURAL NETWORKS Statistical Models as NNs Feed-Forward Neural Network with One Hidden Layer NN Application Conclusion APPENDICES Likelihood Theory R Information Bibliography Index

Extending the linear model with R : generalized linear, mixedeffects and nonparametric regression models

Tree-ring-based disturbance reconstruction in interdisciplinary research: current state and future directions

The mechanization of silvicultural work on forest plantations is usually driven by a decreasing supply of motivated labour which increases its relative cost. Mechanization can also result in other advantages like increased effectiveness, higher efficiency, and improved working conditions. The purpose of our review is to examine the last few decades’ endeavours to mechanize the regeneration activities of plantation forestry in the southern and northern hemisphere. In this case, regeneration activities include (1) site preparation; (2) tree planting; and (3) stand tending until the crop trees are free from vegetative competition. Originally, the mechanization of silvicultural work commenced in the northern hemisphere, but over the past decades, the most notable progress has been made in the southern hemisphere plantation forests. Although soil preparation is largely mechanized across the globe, tree planting and stand tending activities lag behind because of factors such as global variations in the manner in which they are performed, higher level of complexity, and low-cost competitiveness compared with existing labour-intensive methods. For mechanization of regeneration/silvicultural activities to progress, productive and adaptable machines will be required where economies of scale permit cost-efficient operations. These machines will probably have to be modified to the specific forestry context of different countries. Knowledge of the existing and state-of-the-art regeneration technologies available in both the northern and southern hemispheres is important for foresters to make informed decisions about the selection and application of mechanized regeneration systems.

Advances in the Mechanization of Regenerating Plantation Forests: a Review

Understanding the response of tree regeneration following commercial thinning treatments can improve planning in managed forests dependent on natural regeneration. We used long-term commercial thin...

Commercial thinning stimulates natural regeneration in spruce–fir stands

We evaluated the effectiveness of commercial thinning mainly from below (CT; 0, 26%, 32% and 40% merchantable basal area removals) in meeting wood production demands and developing structural heterogeneity in a balsam fir (Abies balsamea (L.) Mill) and spruce (Picea spp.) stand. After 10 years, 32%–40% removals showed a 12%–18% increase in mean diameter and 27%–38% increase in gross merchantable volume (GMV) per tree compared to the unthinned control. At the stand level, all thinning treatments generated as much cumulative GMV (harvested volume + GMV after 10 years) and gross sawlog volume per hectare as the unthinned control. As for stand structure, eight out of nine thinned experimental units showed increased structural heterogeneity after 10 years, i.e., irregular, positively-skewed diameter distribution with an elongated right tail toward larger trees. The diameter distribution in the unthinned control became more symmetric, unimodal and regular over time, with fewer saplings than at the beginning of the experiment and lower density of larger trees compared to CT. Regeneration density and stocking were abundant in all treatments, largely dominated by balsam fir. Results indicate that thinning can be used to meet wood production objectives and help develop structural heterogeneity in this forest.

Commercial Thinning to Meet Wood Production Objectives and Develop Structural Heterogeneity: A Case Study in the Spruce-Fir Forest, Quebec, Canada

We studied late-entry commercial thinning effects on growth, yield, and regeneration in a 48-year-old jack pine (Pinus banksiana Lamb.) stand. Applied thinning intensities were 27, 32, and 47% of merchantable basal area (BA) excluding skidding trails. After 15 years, mean diameter at breast height of surviving trees in the 47% BA removal increased by 4.9 cm (25%) compared to the unthinned control. The 47% BA removal also increased gross merchantable volume (GMV) tree−1 by 46% compared to the control. The 27% BA removal had twice as much GMV ha−1 compared to the 47% BA removal after 15 years. Moreover, cumulative GMV ha−1 was much higher in the 27% BA removal than in the unthinned control. The highest thinning intensity produced larger trees on average, while the lowest thinning intensity maximized volume production per hectare. Maintenance of acceptable growing stock throughout the 15-year period in the 27% BA removal could provide other ecosystem functions such as biodiversity enhancement or wildlife habitat by delaying senescence. Regeneration data showed that a shift in species composition occurred in the understory. After 15 years, the understory was dominated by black spruce (Picea mariana (Mill.) B.S.P.), white birch (Betula papyrifera Marsh.), and trembling aspen (Populus tremuloides Michx.). If regenerating jack pine is an objective after final overstory removal, additional efforts will be needed to re-establish this species.

/pdf/late-entry-commercial-thinning-effects-on-pinus-banksiana-49kihmkdwg.pdf

Late-entry commercial thinning effects on Pinus banksiana: growth, yield, and stand dynamics in Québec, Canada

Lack of available workforce in motor-manual operations has led to increased interest in mechanized precommercial thinning (PCT) treatments. We evaluated 15 years of growth and yield development of ...

Precommercial thinning as a silvicultural option for treating very dense conifer stands

Research Highlights: The spatial distribution of trees results from several ecological processes that can be difficult to measure. We applied a point process modelling approach that uses the diameter and species of neighbouring trees to represent inter-tree interactions through repulsive and attractive processes. Thinning treatments slightly influence the tree spatial distribution of trees in white spruce plantations. Integrating this “spatialiser” into growth models could help improve stand simulations following various thinning treatments over larger areas and longer periods. It could also allow for the use of spatially explicit models when tree position is not available. Background and Objectives: Tree spatial patterns result from several ecological processes and have important implications in forest ecology and management. The use of spatial information can significantly improve our understanding of forest structures. However, this implies intensive field work that is rarely integrated into forest inventories. The aims of this study were to develop a spatial distribution simulator of trees in white spruce plantations and to evaluate the influence of thinning treatments. Materials and Methods: A point process modelling approach was used to represent inter-tree interactions through repulsive and attractive process in white spruce (Picea glauca (Moench) Voss) plantations in eastern Quebec, Canada, that had been commercially thinned five years ago. Balsam fir (Abies balsamea (L.) Mill.) and hardwoods together can represent 30–40% of the basal area of these plantations. Results: The diameter and species of each tree’s two closest neighbours were found to be the most important predictors in explaining the observed distances between trees. Despite the short period since thinning treatments, results showed that the treatment had slight significant effects on tree interactions. However, their impact on the global spatial distribution of stands is quite limited. Conclusions: Using only a few readily-available variables (species and diameter of trees), this “spatialiser” will make it possible to assign spatial coordinates to trees and generate realistic stand spatial structures even after various silvicultural treatments.

Modelling the Spatial Structure of White Spruce Plantations and Their Changes after Various Thinning Treatments

Commercial thinning enables forest managers to meet timber production objectives. Thinning reduces tree density to alleviate competition for resources and favour growth of selected tree species. Ho...

Commercial thinning that maintained species diversity of a mixed black spruce–jack pine stand enhanced productivity

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