Variation in Wood Characteristics and Rotatlon Age of Loblolly Pine for Pulpwood

Tracheid length in radial direction first gradually increases and then levels off from pith to bark.It decreases along the stem height.Variation in tracheid length-width ratio is similar to that in tracheid length.Tracheid length,length-width ratio,double wall thickness-diameter ratio and diameter-width ratio vary from 1.403 mm,46.7,0.381 and 0.711 to 4.456 mm,70.1,0.496 and 0.786 respectively within 16 years old trees of loblolly pine. Specific gravity increases from 0.324 g/cm3 at pith to 0.428g/cm3 at bark and it decreases from 0.401 to 0.314 g/cm3 along the stem height.The mean value of specific gravity at a given height between trees is not related to that of tracheid length. Cellulose content asends from pith(37.04%)to bark (43.91%),lignin and pentosan contents descends from pith (28.78% and 14. 59%)to bark(25.74% and 12.05%)and the extractives content is between 8.38% and 2.12%. The juvenile period of its wood is about 10 to 13 years old.According to basic demands of pulpwood properties,variation in wood characteristics of different age tree and the growth property of tree,rotation age of loblolly pine for pulpwood is about 12 to 13 years old.