GROWTH STRAINS IN PURE STANDS OF JACK PINE

Growth stresses in pure stands of jack pine (Pinus banksiana LAMB.) we re investigated. Longitudinal released strains were measured in relati on to tree ages, diameters, and widths of annual rings. The lower limi t of released strains was -0.03%, and the most frequent value was -0.0 1 to -0.015%. There is no significant correlation between released str ain and the three factors of tree age, diameter of tree trunk, and wid th of annual ring as regards normal trees without compression wood. Re leased strain was a function of the S2 microfilbril angle between tree s. Tree age was associated with changes of tracheid length and microfi bril angle. Therefore, released strain may not be controlled by microf ibril angle alone between the stands. In jack pine, the microfibril an gles in latewood were larger than those in earlywood in contrast to th e generally described trend.