- Han, Yanruo
University of Maine
The study had two major objectives. One objective was to assess soil drainage class, individual tree, and position within tree effects on physical and mechanical properties. The other objective was to examine the relationships of specific gravity, MOR and MOE to age and how the relationships were affected by soil drainage class, individual tree and position within tree. The emphasis was on red maple (Acer rubrum L.), but sugar maple (Acer saccharum Marsh.) was also included in the study.
In the first objective, 15 dominant red maple were selected from a red maple-sugar maple stand that extends across a range of drainage classes. Eight trees were taken from a well-drained site and seven from a poorly drained site. Bolts were taken at three bole positions (lower, middle, upper) from each tree. In addition, seven dominant sugar maple were selected from the well-drained site. However, a bolt was taken only from the lower portion of each bole. Specimens from each bolt were cut and tested according to ASTM Standard D143-83 and data were collected on the following properties: specific gravity, radial shrinkage, tangential shrinkage, compression parallel to the grain, shear, side hardness and end hardness. Bending speciments, 1x1x16 in., were cut from the lower bolt of red maple trees from the well-drained site. The data were analyzed using a general linear model and regression procedures.
In the second objective, microbending specimens, extending from pith to bark along two opposite radii, were cut from each bold. Part B included six additional trees from the well-drained site, making a total of 14 trees for that site. Specific gravity, MOR and MOE were determined for each specimen. Segmented regression was used to estimate the transition age from juvenile wood to mature wood for each property. A general linear model was used to test for effects of site, tree, position within tree and age.
Site, tree, position, the interaction of site and position, and the interaction of tree and position had significant ( P < 0.05) effects on the physical and mechanical properties of red maple, except for the position and the site-position interaction effects on the tangential shrinkage. All the physical and mechanical properties of red maple on the wet site were larger than those on the dry site, except for the tangential shrinkage. As compared with the book values, the results of the physical and mechanical properties of red maple on both sites are larger than those values published in ASTM 2555 and Wood Handbook. The physical and mechanical properties of sugar maple statistically larger than those of red maple.
Age, site, tree, position, the site and position interaction, and the position and tree interaction significantly affected specific gravity, MOE and MOR in the juvenile zone. Age did not significantly affect specific gravity, MOE and MOR in the mature but the effects of site, tree, the interaction of tree and position, and the interaction of position and tree were significant. Red maple has an increase in specific gravity, MOE and MOR from the pith outward, followed by a levelling off. In the mature zone, specific gravity, MOE and MOR of red maple on the wet site were larger than on the dry site. There were variation among and within trees. The average percentage increase for MOE and MOR of red maple from juvenile wood to mature wood was from 11 to 40. Specific gravity of red maple on both sites increased relatively less than MOR and MOE. Trends of microbending properties of specific gravity, MOE and MOR for sugar maple at the bottom bole position were less pronounced than those of red maple. Sugar maple had higher specific gravity, MOE and MOR than red maple.