Modeling dynamics of competing vegetation in young conifer plantations of northern California and southern Oregon, USA (1)

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Date: Oct. 2006
From: Canadian Journal of Forest Research(Vol. 36, Issue 10)
Publisher: NRC Research Press
Document Type: Article
Length: 5,250 words
Lexile Measure: 1520L

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Abstract: This paper describes the development of growth equations for competing vegetation in young conifer plantations, consistent with an individual-tree growth model architecture. Response variables were height increment, basal diameter increment, and change in crown width for a 2-year growth interval. The results for three common competing shrub and three competing hardwood species are presented. Fit statistics for hardwoods were generally much better than those obtained for shrub species. Crown width growth equations generally had very poor fit statistics. Static crown equations also relate crown area to plant height. The equations were developed for use in an individual-tree plant growth model for young plantations.

Resume : Cet article decrit le developpement d'equations de croissance pour la vegetation concurrente dans de jeunes plantations de coniferes, consistante avec une architecture de modele de croissance pour arbre individuel. Les variables independantes etaient l'accroissement en hauteur, l'accroissement en diametre au collet et le changement dans la largeur de la cime apres un intervalle de croissance de 2 ans. Les resultats sont presentes pour trois especes feuillues et trois arbustes communs concurrents. Les statistiques d'ajustement etaient generalement bien meilleures dans le cas des feuillus que celles obtenues pour les especes arbustives. Les equations de croissance en largeur de la cime avaient generalement un tres mauvais ajustement statistique. Les equations statiques de la cime mettent aussi en relation la superficie de la cime et la hauteur de la plante. Les equations ont ete developpees pour etre utilisees dans un modele de croissance d'arbre individuel et de plante pour les jeunes plantations.

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Introduction

Early phases of stand establishment require substantial investment to ensure adequate growth and survival of conifer species. Growth of planted conifers may be hindered by competing vegetation in the early stages of plantation establishment. Treatment of competing vegetation is often an important consideration if planted conifers are to establish dominance.

Numerous species of hardwoods and shrubs compete with planted conifer seedlings in southern Oregon and northern California. Here, the key planted species are ponderosa pine (Pinus ponderosa P. and C. Laws.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco).

The importance of competition on ponderosa pine is well established. Dahms (1950) observed height growth losses that ranged from 57% to 68% in ponderosa pine growing in competition with manzanita (Arctostaphylos sp.) and snowbrush (Ceanothus velutinus Dougl. ex Hook). Oliver (1979) found brush competition reduced diameter growth by 17%-30% and height growth reduced by 10%-14% over a 12 year period. McDonald and Fiddler (1990) observed similar competing vegetation impacts, up to a 48% reduction in diameter growth attributed to competing shrubs. Powers et al. (2005) observed reductions in crop tree volume growth of over 50% because of competition from whiteleaf manzanita (Arctostaphylos viscida Parry) on productive site and nearly 70% on a poor site. Similarly, studies in Douglas-fir have found significant reductions in diameter and height growth attributed to competing vegetation in young plantations (Tesch and Hobbs 1989; White 1989; Knowe 1994; Hanson 1997).

Several growth and yield simulators have gained wide acceptance...

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Gale Document Number: GALE|A155476236