Thinning response and growth trends of seeded Scots pine stands at the arctic timberline

• Published in: Silva Fennica
• Main Authors: Varmola, Martti, Salminen, Hannu, Timonen, Mauri
• Format: Article in Journal/Newspaper
• Language: English
• Published: Finnish Society of Forest Science 2004
• Subjects: Forestry; SD1-669.5; Arctic
• Online Access: https://doi.org/10.14214/sf.436; https://doaj.org/article/df6463242a8f4aaab170c671f1c94097

Growth patterns and reactions of Scots pine (Pinus sylvestris L.) to thinning in extremely harsh climatic conditions were studied in two seeded Scots pine stands located on the arctic timberline. Coniferous trees usually do not form closed stands at the timberline, but occur only in scattered tree groups. The trial was established in two stands in 1985â1986 when the trees were at an age of 47 and 56 years and an average dominant height of 6.0â6.9 m. The trial was remeasured in 1998. The thinning treatments reduced the stem number for five different levels; final density of 300, 550, 800, 1050, and 1300 stems haâ1 and unthinned. The experiment had a randomised block design with four replications in each stand. The increased growing space provided by thinning accelerated diameter growth after a delay of 2â3 years. The differences between the radial growth of the thinning treatments were very clear during the whole 13- to 14-year observation period. Annual increment of the mean diameter was regularly the higher, the larger the spacing. Dominant diameter was less influenced by treatments. There were no significant differences in dominant height between any of the treatments. Both basal area and volume were regularly the greater the higher the stem number was. Even a relatively light thinning had a distinct positive effect on tree growth, i.e. not carrying out thinning resulted in a production loss of merchantable wood. According to the results, seeded stands on the arctic timberline can grow surprisingly well in favourable conditions and reach a dominant height of 12â14 m in 100 years and a mean annual increment of 1.0â1.5 m3 haâ1 yâ1 over a rotation period of 130â160 years. Based on increment figures and thinning reactions, a spacing of ca. 1000 stems haâ1 can be recommended.