Vegetation responses to stand structure and prescribed fire in an interior ponderosa pine ecosystem (1)

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Date: May 2008
From: Canadian Journal of Forest Research(Vol. 38, Issue 5)
Publisher: NRC Research Press
Document Type: Report
Length: 6,639 words
Lexile Measure: 1400L

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Abstract: A large-scale interior ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) study was conducted at the Blacks Mountain Experimental Forest in northeastern California. The primary purpose of the study was to determine the influence of structural diversity on the dynamics of interior pine forests at the landscape scale. High structural diversity (HiD) and low structural diversity (LoD) treatments were created with mechanical thinning on 12 main plots. Each plot was then split in half with one-half treated with prescribed fire. During the 5 year period after the treatments, the LoD treatments showed slightly higher periodic annual increments for basal area (BA) and significantly higher diameter increments than did the HiD treatments, although HiD carried twice as much BA as LoD did immediately after the treatments. Prescribed fire did not affect growth, but killed and (or) weakened some trees. No interaction between treatments was found for any variable. Stand density was reduced from the stands before treatments, but species composition did not change. Old dominant trees still grew and large snags were stable during the 5 year period. Treatments had minor impacts on shrub cover and numbers. These results suggest that ponderosa pine forest can be silviculturally treated to improve stand growth and health without sacrificing understory shrub diversity.

Resume : Une etude a grande echelle sur le pin ponderosa continental a ete realisee dans la Foret experimentale Blacks Mountain situee au nord-est de la Californie. Le but principal de l'etude etait de determiner l'influence de la diversite structurale sur la dynamique des pinedes continentales a l'echelle du paysage. Des traitements de diversite structurale eleve e (HiD) et faible (LoD) ont ete crees a l'aide d'eclaircies mecanisees dans 12 parcelles principales. Par la suite, chaque parcelle a ete divisee en deux et l'une des deux moities a recu un brulage dirige. Pendant la periode de cinq ans qui a suivi l'application des traitements, les traitements LoD ont produit un accroissement annuel periodique en surface terriere legerement superieur et un accroissement en diametre significativement plus eleve que ceux des traitements HiD, meme si la surface terriere des traitements HiD immediatement apres les traitements etait deux fois plus grande que celle des traitements LoD. Le brulage dirige n'a pas eu d'effet sur la croissance, mais a affaibli ou cause la mort de certains arbres. Aucune interaction entre les traitements n'a ete detectee quelle que soit la variable consideree. Par rapport aux conditions avant l'application des traitements, la densite des peuplements a ete diminuee mais la composition en espece n'a pas change. Les vieux arbres dominants ont continue de croytre et le nombre de gros arbres morts sur pied est demeure stable pendant la periode de cinq ans. Le traitement a cause un impact mineur sur le nombre et le couvert d'arbustes. Ces resultats indiquent que les forets de pin ponderosa peuvent recevoir des traitements sylvicoles pour ameliorer la croissance et l'etat de sante des peuplements sans sacrifier la diversite des arbustes sous couvert.

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Introduction

Ponderosa pine...

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Gale Document Number: GALE|A180697302