Advantages of the Parabolic Expression of Height-Diameter Relationships

Smith, J. Harry G.

doi:10.5558/tfc31236-3

Cited by 36 publications

(24 citation statements)

References 1 publication

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“…In FORCLIM, tree height (gH c ) is calculated from tree diameter (Dc) using the allometric relationship by Ker and Smith (1955). Leaf area and leaf mass are also predicted from tree diameter, but the allometric relationships have been improved as compared to those used by Kienast (1987) by taking into account a large set of experimental data (Burger 1945(Burger -1953.…”

Section: Model Formulationmentioning

confidence: 99%

A Simplified Forest Model to Study Species Composition Along Climate Gradients

Bugmann¹

1996

Ecology

277

276

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Forest models based on the gap dynamics hypothesis (gap models) have gained an important role in forest ecology and have grown rather complex in the last 20 yr. They have been applied extensively to study the impacts of climatic change on ecosystems although they originally were not built for this purpose. The objectives of this study were (1) to develop a new forest gap model, ForClim, that includes only a minimum number of ecological assumptions but robust parameterizations of the effects of climate on plant population dynamics; (2) to test the realism of ForClim as compared to its predecessor model, FORECE; and (3) to examine the behavior of FORECE and ForClim systematically along climate gradients in Europe. ForClim is composed of three modular submodels: ForClim—P for plant population dynamics, ForClim—S for soil carbon/nitrogen turnover, and ForClim—E for providing reliable parameterizations of the abiotic environment. For the core model, ForClim—P, it was found that only four factors are sufficient to model tree growth, another four factors are required to model tree establishment, and only two factors are required to model tree mortality. The behavior of ForClim was tested at a large number of sites in the European Alps. The model yields tree species compositions that conform to field data and are very similar to those of the predecessor model. Based on this evaluation alone, it would not be possible to favor one of the models over the other. The behavior of both models then was examined systematically in a parameter space spanned by the annual mean temperature and the annual precipitation sum. From this exercise it became evident that both the pattern of aboveground biomass and the realized niches of the dominating tree species are simulated realistically by ForClim. Extremely steep gradients are characteristic of FORECE, and many ecotones are simulated to occur in the wrong places in FORECE. Thus, some of the current forest gap models can be simplified without reducing the realism of their behavior, and models other than FORECE should be scrutinized in this respect as well. The present study also suggests that the evaluation of model behavior at scattered sites is insufficient to show their validity for simulating forest dynamics along climate gradients. Further rigorous model comparisons and validation studies are required to increase the reliability of this promising class of models.

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Section: Model Formulationmentioning

confidence: 99%

A Simplified Forest Model to Study Species Composition Along Climate Gradients

Bugmann¹

1996

Ecology

277

276

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“…Mais le choix du modèle pour représenter ces relations n'est pas neutre. Parmi les modèles souvent utilisés, citons la droite, la parabole (Ker et Smith, 1955) ou les fonctions logarithmiques (Curtis, 1967 ;Wykoff et al, 1982). Ces modèles ont l'avantage d'être facilement ajustables avec des procé-dures de régression linéaire (Curtis, 1967 ;Farr et al, 1989), mais présentent en contrepartie un comportement divergent pour des valeurs extrêmes des circonférences.…”

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Ajustement d'un modèle hauteur-circonférence pour l'épicéa commun. Effet de la densité

1996

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“…Height growth is estimated by the following equation (Ker & Smith 1955): H = 137 + b2D-b3 D2 where H is height, 137 represents breast height (in cm), D is diameter at breast height, and the constants b 2 and b 3 are derived from maximum height (Hm~) and maximum diameter (Dn~) such that H = H x and dH/dD = 0 when D = Din, x. Thus, b 2 = 2(Hm, x -137)/D x and b 3 = (Hm~ t -137)/Dm~x2.…”

Section: Methodsmentioning

confidence: 99%

Test of a forest dynamics simulator in New Zealand

DeVelice¹

1988

New Zealand Journal of Botany

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A computer simulation model of forest dynamics is described and tested against observations from Fiordland, New Zealand. The model tracks the birth, growth, and death of individual trees and is driven by species-specific attributes of maximum age, height, and diameter. Recruitment is determined stochastically and on the basis of seed production indices and establishment requirements. Simple mathematical expressions are utilised and the number of assumptions is minimised. The reasonable agreement of the simulated trends and observation suggests that forest dynamics after landslides in Fiordland may be predicted on the basis of life history characteristics and stochastic events. Modelling of forest dynamics has wide scientific and management applications including: prediction, advancement of basic understanding of forest dynamics, assistance in research planning, and information synthesis.

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Advantages of the Parabolic Expression of Height-Diameter Relationships

Cited by 36 publications

References 1 publication

A Simplified Forest Model to Study Species Composition Along Climate Gradients

A Simplified Forest Model to Study Species Composition Along Climate Gradients

Ajustement d'un modèle hauteur-circonférence pour l'épicéa commun. Effet de la densité

Test of a forest dynamics simulator in New Zealand

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