FIBER DIMENSIONS AND THEIR RELATIONSHIP WITH THE TRANSITION AGE BETWEEN JUVENILE AND MATURE WOOD OF <i>Eucalyptus grandis</i> W. Hill ex Maiden

Trevisan, Rômulo; Rosa, Magda; Haselein, Clovis Roberto; Santini, Elio José; Gatto, Darci Alberto

doi:10.5902/1980509830220

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Artigos • Ciênc. Florest. 27 (04) • Oct-Dec 2017 • https://doi.org/10.5902/1980509830220 copy

FIBER DIMENSIONS AND THEIR RELATIONSHIP WITH THE TRANSITION AGE BETWEEN JUVENILE AND MATURE WOOD OF Eucalyptus grandis W. Hill ex Maiden

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT

This study was undertaken to evaluate the fiber dimensions and the transition age between juvenile and mature wood of Eucalyptus grandis. It was selected, based on the Assmann’s dominant diameter, four trees of an experimental stand located in the northern coast of Rio Grande do Sul state, with 18 years of age. After cutting down, in the disk corresponding to the region of the DBH (diameter at breast height) were marked and sectioned central baguettes, where crafted fragments were selected at regular intervals in pith-to-bark direction for maceration and, thereafter, determination of the length, the total diameter, the lume diameter and the wall thickness of the fibers with the aid of an optical microscope with a graduated eyepiece. The segregation of both types of wood was determined by the radial variation of the fiber length and using simple and multiple linear regressions; and a transitional age through simple linear regression. The lower values for the dimensions of length, total diameter and wall thickness of the fibers were observed near the pith, with an increasing trend toward the bark, suggesting the existence of differences between wood near the pith and the bark. However, this standard was not observed in the lume diameter of the fibers, which showed an increase to the middle position of the radius followed by a decrease to the outer portion. The transition zone between juvenile and mature wood has been established between the ages of 4.2 and 4.7 up to 8.1 and 9.1 years, range termed juvenile wood that corresponding to 4.2 and 4.7 years; and adult wood exceeding 8.1 and 9.1 years. The transition between adult and juvenile wood occurred at 10 cm from the pith, that is, in the age of about 6.1 years. The definition of the age at which the transition between the juvenile and mature wood occurs facilitates the wood transformation processes once the juvenile portion constitutes an obstacle to the viability of its industrial use.

Keywords:
anatomical elements; segregation of wood; wood quality

TABELA 2: Valores médios do comprimento, do diâmetro do lume, do diâmetro total e da espessura da parede das fibras para as árvores dominantes de Eucalyptus grandis e análise de variância dessas variáveis em função da posição radial no sentido medula-casca.

Dimensões das fibras	Ẍ(σ)	QMe	F cal.	Prob.>F
Comprimento de fibra (µm)	1175,8 (±222)	25542,26	280,49	0,0001**
Diâmetro do Lume da fibra (µm)	14,1 (±3,51)	11,46	23,53	0,0001**
Diâmetro total da fibra (µm)	23,9 (±4,17)	13,7	81,64	0,0001**
Espessura da parede da fibra (µm)	4,9 (±1,30)	1,27	100,29	0,0001**

TABELA 3: Análise de variância das dimensões das fibras da madeira das árvores dominantes de Eucalyptus grandis em função da posição no sentido medula-casca.

		Posições amostradas no sentido medula-casca
Dimensões das fibras	Interna (CV)	Central (CV)	Externa (CV)
Comprimento de fibra (µm)	960,33 c (16,0)	1234,75 b (13,2)	1332,33 a (12,5)
Diâmetro do Lume da fibra (µm)	13,20 c (23,1)	15,30 a (21,6)	13,96 b (29,3)
Diâmetro total da fibra (µm)	21,20 b (16,6)	24,94 a (14,4)	25,48 a (16,5)
Espessura da parede da fibra (µm)	4,00 c (25,5)	4,82 b (23,2)	5,76 a (23,0)

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[TFN1] Em que: d100 = diâmetro da árvore dominante de Assmann, em cm; h100 = altura da árvore dominante de Assmann, em m; σ = desvio padrão da média, em cm para d100 e m para h100.