Variation Patterns Of Tracheid Anatomical Characteristics And Basic Density For Loblolly Pine Grown In Jiangxi Of China

In this paper variation patterns of latewood percentage, wood anatomical characteristics(Tracheid morphological features, microfibrillar angle ) and basic density at radical and axial directions for loblolly pine grown in Jiangxi of China, and the correlation among them were investigated, the results were as follows:From pith to bark, the annual ring width increases rapidly in la —4a, decreases in 4a—10a, becomes wider after 17a and then levels off gradually after 22a for the changes of environments. The variation of annual ring width is ruleless at the axial direction.The variation model of latewood percentage of loblolly pine is increases rapidly before 10a, and after 11a levels off. At axial direction the variation oflatewood percentage is ruleless.The mean values of earlywood of tracheid length, width, diameter, double wall thickness, length-width ratio, double wall thickness-diameter ratio, and diameter-width ratio is 3314μm, 47.4μm, 38.8μm, 8.6μm, 69.8, 0.23 and 0.82 respectively, the mean values of latewood is 3540μm, 41.3μm, 13.0μm, 25.5μm, 92.1,2.22和0.34. The values of latewood of tracheid length, double wall thickness, length-width ratio and diameter-width ratio in the annual ring are lager than that of earlywood. The radical variation of latewood and earlywood of tracheid length is similar to that of tracheid length-width radio, increases rapidly before 10a, the 10a—12a is the mature transition position, after 12a they level off. At the same ring tracheid length and length-width ratio increase progressively from the base upward, maximize at 3.3m and 5.3m, and then decrease to the top of the tree. In radical direction tracheid double wall thickness of latewood increases rapidly before 5a, in 5a—12a increases gradually, then after 12 years old levels off; The tracheid double wall thickness of earlywood in radical direction levels off. There is a slightly variation of tracheid double wall thickness along stem height, which is as same as tracheid length. The variations of tracheid double wall thickness-diameter ratio of earlywood and latewood of loblolly pine are similar to the tracheid double wall thickness in radial and axial directions. In tracheid width, diameter and diameter-width ratio the value of earlywood are larger than that of latewood in the same ring. Tracheid width of earlywood and latewood has the same variation in radical direction, before 6a increase rapidly, and 7a-11a increase slowly, after lla level off. Tracheid width increases progressively initially and then decreases along stem height. From pith outward the tracheid diameter of earlywood increases rapidly inla-5a, then increase slowly, after 13a levels off; the tracheid diameter of latewood decreases from pith to bark, maximize in 2a, and levels off after 5a. The variation of tracheid diameter isruleless in axial direction. From pith outward the tracheid diameter-width ratio increases slowly, or in latewood decreases rapidly before 5a, after 5a both of them level off. Along stem height, Tracheid diameter-width ratio is big at the base, minimizes at breast height , and then increases step by step. Tracheid diameter-width ratio near bark is larger than that near base.The mean value of basic density of loblolly pine is 0.4731g/cm3. The variation of basic density at different height within trees is similar with each other in radical direction. From pith outward, basic density increases according the annual ring, and then increases slowly. The variation of basic density decreases in axial direction.The mean value of microfibrillar angle of loblolly pine is 12.53° in earlywood and 11.48° in latewood. The value of earlywood is significantly larger than that of latewood in the same annual ring, in radical variation the microfibrillar angle of earlywood is similar to that of latewood, they also decrease rapidly in 2a-7a, and decreases slowly in 7a-lla, after lla levels off. The difference value between earlywood and latewood of microfibrillar angle decreases dramatically in la-4a, and decreases fluctuantly after 4a, levels off after 8a. Microfibrillar angle maximizes 13.8° at 0.3m stem height along stem height, then decreases step by step, and minimizes at 5.3m, and then increases slowly near bark.The mean value of the content of extractives of loblolly pine is 5.65%. The content of extractives decreases dramatically from pith to bark, after 5a levels off, the maximum of the content of extractives is near pith. The variation of the content of extractives is ruleless along stem height.The coefficient of variability of tracheid length, wall thickness-diameter ratio, and the content of extractives of loblolly pine is bigger within trees. The coefficient of variability of tracheid length, width, diameter, double wall thickness, length-width ratio, diameter-width ratio, basic density arid the content of extractives within trees is larger than that of among trees, which indicates that the variation within trees is larger than that among trees.There is a very significant negative correlation (p<0.01) between the earlywood and latewood of tracheid length and microfibrillar angle in radical direction at different stem height within trees, which indicates that the highly negative correlation between tracheid length and microfibrillar angle is not affected by annual ring and tree height in radical direction within trees. The negative correlation between tracheid length and microfibrillar angle of earlywood, latewood and the whole ring in radical direction among trees also is found, but the negative correlation is significant at 0.05 level in 7a-13a. Which indicates that the correlation within trees is larger than that among trees.There is negative correlation between basic density and annual ring width in the juvenile period, and positive correlation in the late mature period. Basic density is positive correlation with latewood percentage. The correlation between basic density and tracheid morphological features within annual rings is not good. There is a significantly negative correlation between basic density and tracheid diameter > diameter-width ratio among the annual rings, but the correlation of others are significant positive correlation (p<0.01). These indicate that basic density is not affected by tracheid characteristics within the annual rings, but significantly affected among the annual rings. There is significantly positive correlation among the annual rings in radical direction between basic density and the content of extractives, which indicates that basic density is significantly affected by the content of extractives.The juvenile period can be confirmed in ll~13a under the consideration of the variation of latewood percentage, tracheid morphological features, basic density, microfibbrillar angle in radial direction. There are many differences in anatomical characteristics between juvenile and mature wood, the differences of annual ring width, tracheid width and microfibrillar angle between juvenile and mature wood are not significant, but the difference of hot water extractives is significant (p<0.05), and that of the others are very significant (p<0.01), which indicates that the course of the tree annual and the variation wood in vivo structures.