Variations in fiber length within a first-thinning Scots pine (Pinus sylvestris) stem

Variations in average fiber length and fiber length distribution both in the longitudinal and horizontal directions of a first-thinning Scots pine (Pinus sylvestris) stem and between six stems of similar age (26–30 years) and height (10.7–12.8 m) were studied. As a general trend, fiber length increased from the pith (0.8–1.3 mm) to the outer part of the stem (1.9–2.9 mm) maximizing at the relative stem height of 20–40%. Variations in fiber length between stems were smaller than those within a stem. The average fiber length of different stems of the same age (28 years) or diameter at breast height (11 cm) depended typically on wood growth rate. Finally, kraft cooking experiments on different parts of the stem (i.e., butt and top as well as inner and outer parts of the stem) indicated clear differences in their pulp properties. It was concluded that due to the acceptable properties of these pulps, first-thinning wood material as such or after the suitable fractionation may offer a potential source of fiber for a variety of different purposes.