Environment and Genetic Effects on Wood Quality of Populus

Abstract

The purpose of the research was to investigate wood properties of new poplar clones from three different environments. Specific gravity, density, and anatomical properties were studied.

Impacts of the cottonwood leaf beetle (Chrysomela scripta) on wood properties were investigated on two six-year-old clones in the first study. The results indicated that insect defoliation caused moderate to large decreases in annual growth over the first three years. Clones had different specific gravity and density for protected trees and constant values along the radius regardless of beetle attack. Fiber length was not affected by defoliation. Vessel number and diameter were impacted by defoliation and offsetting changes in vessel numbers and diameters partially cancel out changes in vessel area. Ray area was larger for unprotected trees; one clone responded to defoliation by producing more rays; meanwhile, the other produced fewer but larger rays.

The second study dealt with wood properties of eight six-year-old Populus deltoides clones of two families grown under stressful site conditions. There were no differences in growth rate between the two families; however, specific gravity was significantly influenced by family and by clone. Fiber length was affected only by clone and radial position and correlated with growth rate. Clonal averages of fiber length were different closer to the bark suggesting that the earliest selection for fiber length should start after four or five years.

The third study analyzed wood variation for four-year-old Populus deltoides trees with exceptional specific gravity and growth rate values. There were significant differences among trees in fiber length and vessel area but not in vessel numbers, vessel diameter, and in ray numbers. The age of the cambium significantly affected all wood properties. The fastest growing tree with high specific gravity had the longest fibers, the highest ray numbers but low vessel area, vessel number, and low vessel diameter representing an unusual combination of traits. Results indicate that trees with similar growth rates can have wide variation in vessel area and that exceptionally fast-growth tree can be achieved with low vessel area.