Abstract
Regional yield models,used for large-scale resource forecasting, estimate the standing volume of a timber resource for different ages, site qualities and degrees of stocking. Stand models predict average tree dimensions and area-based quantities for whole stands, while size-class models project the development of a limited number of representative trees, which possess average attributes within a cohort of similar trees.
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Notes
It may, of course, be preferable to use other size variables, such as height, crown length or crown volume.
The sampling technique is known as the structural group of 4. Samples are taken on systematic grid points. The group of 4 consists of the tree nearest to the sample point and its 3 nearest neighbors (Füldner, 1995). It is a simple and effective method for obtaining distributions of mingling and differentiation.
A total enumeration would be a fairly hopeless endeavour. For example, in a forest containing 47 trees (with 20 trees of species 1, 15 of species 2 and 12 of species 3), there are different ways in which the species can be assigned to the available positions.
A distinction must be made between competition and density. Competition refers to the spatial interaction between neighboring trees, while density is a population attribute, a measure of how completely a site is occupied by trees. The term point density is sometimes used in the North American literature as a synonym for competition.
See applications by Newnham (1966), Opie (1968), Bella (1971), Araey (1973), Ek and Monserud (1974).
See also applications by Lorimer (1983); Martin and Ek (1984).
If two competitors are located alongside each other, facing the reference tree, they are both classified as active. The adjective alongside is true if the horizontal distance to the reference tree is within specified bounds of the distance to the already established active competitor and if the horizontal angle relative to the reference tree is greater than a given threshold angle (Lee and Gadow, 1997).
refer also to the distance-independent model PROGNAUS which is using the BAL-index of competition (Sterba and Monserud, 1997).
See details about these variables at the beginning of Chapter 5.
Note that with 3 neighbors, the variable M can assume 4 possible values.
The diameter/height ratio HD of a tree represents the tree height [m] as a percentage of the breast height diameter [cm].
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© 1999 Springer Science+Business Media Dordrecht
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Von Gadow, K., Hui, G. (1999). Individual Tree Growth. In: Modelling Forest Development. Forestry Sciences, vol 57. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-4816-0_5
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