Inter-Tree and Intra-Tree Variations in Moisture Content and Wood Density in Red Cypress (Chamaecyparis formosensis Matsum)

Inter-tree and intra-tree variations in green moisture content, green specific gravity, and basic density in stems of red cypress (Chamaecyparis formosensis Matsum) were investigated in seventy-five 46-yr-old plantation trees. In addition, the relationships of growth characteristics and wood properties were explored. The results provide basic information for nondestructive evaluation and calculations of the dynamic modulus of elasticity, biomass, and carbon storage of standing trees. The average green moisture content value among the sampled trees at breast height position was around 147%, and ranged from 102.9 to 208.5%, with a difference of 19.4%. Five radial positions were defined: a core piece (including the pith), inner heartwood, outer heartwood, transition wood, and sapwood. Results showed that average values of the green moisture content obtained from transition wood were significantly lower than those for the other positions. According to a statistical analysis, no significant differences (p > 0.05) existed for the green moisture content between sapwood and heartwood, but significant differences (p < 0.05) existed between sapwood and heartwood in the live crown. The inter-tree variation in average basic density was around 0.392 g cm-3, and ranged from 0.337 to 0.432 g cm-3, with a difference of 10%. Basic density in sapwood was higher than in heartwood, and that in stems of live crowns was higher than that in basal stems. The average green specific gravity was around 0.963, and ranged from 0.772 to 1.137, with a difference of 11.5%. Average values of the green specific gravity obtained from transition wood were significantly lower than those for the other positions; however, no significant differences existed in different tree height positions. According to a variance component analysis, within-tree variations in green moisture content, green specific gravity, and bulk density were greater than tree-to-tree variations.
There was a significant negative relationship between the basic density and green moisture content, but a positive relationship between green specific gravity and basic density. The values of green specific gravity increased with an increase in the moisture content. Their relationships could be represented by a 2nd-order polynomial regression model. Trees with stronger characteristics not only had wider crown widths, but also larger diameters at breast height (DBH). The DBH values tended to increase with increasing moisture content and green specific gravity, but there was no significant relationship between DBH and basic density.