EFFECT OF SITE CHARACTERISTICS ON JUVENILE WOOD TRANSITION IN LODGEPOLE PINE IN THE INLAND NORTHWEST

Juvenile wood (core wood) in softwood species is typically characterized as being less dimensionally stable and having lowermechanical properties thanmature wood.Determining the age of transition between juvenile wood and mature wood is important when making judgments about utilization options for naturally occurring stands of trees in the intermountain west region of the United States. Lodgepole pine (Pinus contorta Dougl. ex. Loud.) trees were harvested from four different sites in the US Inland Northwest to include site variations that affect growth, such as elevation, precipitation, and length of growing season. Longitudinal shrinkage was measured in each sample as it dried fromgreen to oven-dry conditions. Later, averagemicrofibril angle was determined for the same samples. Although the two methods for estimating the juvenile wood transition period were not in agreement regarding the number of years to mature wood, there was agreement in a ranking of the four sites from shortest transition period to longest transition period. A significant difference in the juvenile wood transition period was found among sites; longer transition periods were attributed to stands in which trees exhibited persistent lower branches rather than to geographic influences. Thiswork illustrates that stand conditions for sources of lodgepole pine can have a substantial influence on physical characteristics of this material when it is used as structural roundwood or solid-sawn products.