A Test of the Exponential Distribution for Stand Structure Definition in Uneven-aged Loblolly-Shortleaf Pine Stands

Murphy, Paul V.; Farrar, Robert M.

doi:10.2737/so-rp-164

Cited by 11 publications

(9 citation statements)

References 5 publications

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“…Tal estructura señala la existencia de una mayor cantidad de diá-metros de tamaño pequeño que de talla grande e indica una escasa regeneración. Semejante distribución es propia también de especies tolerantes a la sombra en bosques húmedos (Murphy y Farrar, 1988;Martínez-Ramos y Álvarez-Buylla, 1995). La densidad total de renuevos en los dos encinares estudiados es 269 individuos ha -1 y 175 plantas juveniles ha…”

Section: Discussionunclassified

Composición y aspectos estructurales de los bosques de encino de la Sierra de Zapalinamé, Coahuila, México

et al. 2009

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To determine the structure and floristic composition of the oak forest of the Sierra de Zapalinamé, we established sixty six plots of 500 m 2 . Density and basal area were measured for adult trees and density and cover in shrubs. Saplings were considered in concentric areas of 50 m 2 and seedlings in five areas of 1 m 2 . All the plants were collected and identified. Vegetation attributes were used to obtain the importance value for trees and shrubs. The vascular flora takes in 259 species and infraspecific taxa with 178 genera in 67 plant families. The forest associations were defined by Quercus greggii -Q. mexicana and Quercus saltillensis -Q. laeta; the most important oaks in the forest structure were Quercus greggii (1480 ind ha . Thirty seven pairs of species were analyzed and 62% have significant association. The shrubs with the highest value of covering were: Garrya glaberrima, Ageratina ligustrina and A. saltillensis. The herbs were 72.9% of the flora and the most common elements were: Artemisia ludoviciana, Pleopeltis guttata, Cheilanthes tomentosa and Achillea millefolium. The species number diminishes when the altitude increases.

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Section: Discussionunclassified

Composición y aspectos estructurales de los bosques de encino de la Sierra de Zapalinamé, Coahuila, México

et al. 2009

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“…Because the numbers of trees by diameter class were so low in the actual data, each number was multiplied by 10 before estimating the model parameters as in Bailey and Dell (1973). The third data set was from a loblolly-shortleaf pine stand (stand 3) published in Murphy and Farrar (1981). The data for stand 4 was recently collected from compartment No.…”

Section: Methodsmentioning

confidence: 99%

A finite mixture of two Weibull distributions for modeling the diameter distributions of rotated-sigmoid, uneven-aged stands

Zhang¹,

Gove²,

Liu³

et al. 2001

Can. J. For. Res.

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The rotated-sigmoid form is a characteristic of old-growth, uneven-aged forest stands caused by past disturbances such as cutting, fire, disease, and insect attacks. The diameter frequency distribution of the rotated-sigmoid form is bimodal with the second rounded peak in the midsized classes, rather than a smooth, steeply descending, monotonic curve. In this study a finite mixture of two Weibull distributions is used to describe the diameter distributions of the rotated-sigmoid, uneven-aged forest stands. Four example stands are selected to demonstrate model fitting and comparison. Compared with a single Weibull or negative exponential function, the finite finite mixture model is the only one that fits the diameter distributions well and produces root mean square error at least four times smaller than the other two. The results show that the finite mixture distribution is a better alternative method for modeling the diameter distribution of the rotated-sigmoid, uneven-aged forest stands.Résumé : La forme sigmoïde inversée est caractéristique des peuplements inéquiennes de vieille forêt. Elle est causée par les perturbations passées telles la coupe, le feu, les maladies et les attaques d'insectes. La distribution de fréquence diamétrale de forme sigmoïde inversée est bimodale avec le deuxième mode situé dans les classes intermédiaires de diamètre, plutôt qu'une courbe lisse, monotone et avec une forte pente négative. Dans l'étude, un mélange fini de deux distributions de Weibull est utilisé pour décrire la distribution diamétrale des peuplements inéquiennes de forme sigmoïde inversée. Quatre peuplements sont sélectionnés à titre d'exemple pour démontrer l'ajustement et la comparaison du modèle. Par rapport à la fonction simple de Weibull ou à la fonction exponentielle négative, la fonction de mélange fini est la seule qui s'ajuste bien à la distribution diamétrale et qui engendre une erreur standard au moins quatre fois plus petite que celles des deux autres fonctions. Les résultats montrent que la fonction de mélange fini constitue un meilleur choix pour modéliser la distribution diamétrale des peuplements inéquiennes de forme sigmoïde inversée.[Traduit par la Rédaction] Notes 1659

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“…Models of this class have different forms (Bruner and Moser, 1973;Ek, 1974;McTague and Stansfield, 1994;Murphy and Farrar, 1988). However, they can all be expressed in terms of matrices, in which the parameters are either constant (Buongiorno and Michie, 1980) or dependent on the stand state (Lin et al, 1998).…”

Section: Introductionmentioning

confidence: 98%

Non‐linear matrix modeling of forest growth with permanent plot data: The case of uneven‐aged Douglas‐fir stands

Ralston

Buongiorno

Schulte

et al. 2003

Int Trans Operational Res

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Uneven-aged forest management is acquiring increasing importance throughout the world as an alternative to clear cutting. Simple stage-structured matrix models can be used to predict the growth of uneven-aged stands, and they are easily incorporated in optimization analysis. Parameters of these models can be estimated from readily available permanent plot data. Such a growth and yield model is presented for mixed, uneven-aged Douglas-fir and hardwood stands. The model was calibrated with data from 66 permanent plots in Oregon and Washington. The density-dependent matrix model predicts the number of trees by diameter class and species type, softwood or hardwood. The parameters are based on individual tree growth equations, individual tree mortality equations, and stand ingrowth equations. The individual tree equations are a function of tree diameter, stand density, species, and site index. The stand-level ingrowth equations are a function of stand density. The model was validated in the short term by comparing the number of trees in each diameter and species class at the time of the second inventory with the number predicted by the model, given conditions at the first inventory. A long-term validation of the model was also done by comparing the steady-state stand structure and stand volume with those observed for old-growth stands. The model was applied to show the effects of different cutting cycles on productivity, diversity of tree species and size, and financial returns. The results suggest that uneven-aged management of the Douglas-fir forest type in the Pacific Northwest can be as productive as even-aged management, with the added benefits of continuous cover forestry.

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A Test of the Exponential Distribution for Stand Structure Definition in Uneven-aged Loblolly-Shortleaf Pine Stands

Cited by 11 publications

References 5 publications

Composición y aspectos estructurales de los bosques de encino de la Sierra de Zapalinamé, Coahuila, México

Composición y aspectos estructurales de los bosques de encino de la Sierra de Zapalinamé, Coahuila, México

A finite mixture of two Weibull distributions for modeling the diameter distributions of rotated-sigmoid, uneven-aged stands

Non‐linear matrix modeling of forest growth with permanent plot data: The case of uneven‐aged Douglas‐fir stands

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