Modelling Forest Development

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Springer Science & Business Media, 30 nov 2001 - 213 pagine
In an lUlffianaged woodland, forest development follows a succession of periods of undisturbed natural growth, interrupted by intermediate loss or damage of trees caused by fire or wind or other natural hazards. In a managed woodland, the most important periodic disturbances are the thinning operations, which are often carried out at regular intervals and which usually have a significant effect on the future evolution of the resource. Thus, a realistic model of forest development includes both natural growth and thinnings. The key to successful timber management is a proper understanding of growth processes, and one of the objectives of modelling forest development is to provide the tools that enable foresters to compare alternative silvicultural treatments. Foresters need to be able to anticipate the consequences of a particular thinning operation. In most cases, total timber volume is not a very appropriate measure for quantifying growth or yields, or changes caused by thinning operations. Yield in economic terms is defined by the dimensions and quality attributes of the harvestable logs, and estimating timber products is a central issue of production-oriented growth and yield research. Introduction 2 Growth modelling is also an essential prerequisite for evaluating the consequences of a particular management action on the future development of an important natural resource, such as a woodland ecosystem.
 

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Sommario

Introduction
Types of forest models
1
Data requirements
4
Permanent plots
7
Temporary plots
9
Interval plots
10
Projecting regional timber resources
13
Empirical yield functions
14
Bivariate DiameterHeight Distributions
84
Estimating Product Yields
90
Volume Ratio Methods
91
Form Quotients Splines and Polynomials
92
Parameterparsimonious Stem Profile Functions
94
Generalized Stem Profile Functions
98
Stem Quality Assessment and Prediction
101
Modelling Thinnings
107

Fully stocked forests
15
Nonfully Stocked Forests
19
Yield Functions based on MAI Estimates
21
Modelling stand development
24
Anamorphic height models
26
Disjoint Polymorphic Height Models
29
Nondisjoint Polymorphic Height Models
34
Basal area
37
Potential Density
40
The Limiting Line
41
Estimating potential density
42
Natural decline of stem number
44
State space models
45
Stand Volume and Product Yields
48
Thinning Models
51
Classical Description of Thinning Operations
52
Thinning Weight
55
Type of Thinning
57
Sizeclass Models
59
Diameter Growth
60
Projecting Diameter Distributions
61
Stand Table Projection
65
Diameter Growth as a Function of Diameter
66
Growth Modifiers
68
Change of Relative Basal Area
73
A Worked Example
75
Transition Matrices
77
DiameterHeight Relations
81
Movement of the Diameter Distribution after Thinning
112
Separation Parameters
114
Modelling Foresters TreeSelection Behavior
119
Individual Tree Growth
127
Generating Spatial Structures
128
Variables for Describing Spatial Structure
129
Size Differentiation
130
Species Segregation and Mingling
131
Aggregation
135
Using Structural Variables to Generate Positions with Attributes
138
Competition Indices
141
Overlapping Influence Zones
143
Distanceweighted Size Ratios
146
Available Growing Space
149
Shading and Constriction
151
Spatial Growth Models
157
FOREST WASIM and MOSES
158
SILVA
163
Spatial Thinning Models
166
Prescription
173
Model evaluation
179
Quantitative Evaluations
183
Statistical Tests
187
Symbols used
189
Literature
193
Index
203
Copyright

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