A comparison of planting, sowing and natural regeneration for Pinus sylvestris (L.) in boreal Sweden

Abstract

Planting, sowing and intended natural regeneration are the main forest regeneration methods used in forest management. These methods were compared in an 11 year field trial in northern Sweden. Pinus sylvestris (L.) seeds of various origin were used. Local seeds were collected from seed-trees on site. Comparisons were made in three steps as follows. 1. (1) All three methods on the seed-tree area and with local seeds. Natural regeneration produced the greatest number of total as well as main crop plants. Planted seedlings had a height lead corresponding to 4.9 years compared with sowing and 5.6 years compared with naturally regenerated main crop plants. Planting resulted in the greatest area production (height sum) based on main crop plants. 2. (2) Sowing and planting on neighbouring clear-felled area, using local seeds. The height lead for planted seedlings corresponded to 5.6 years. The number of main crop plants decreased between the seventh and eleventh growing seasons by 18% for planting and 50% for sowing. The height sum based on main crop plants was almost three times higher for planting than for sowing. 3. (3) The local provenance was compared with seeds for other origin on the clear-felled area. The choice of seed origin had the greatest influence on survival, with seeds of northern origin giving the best production per unit area. Possible long-term effects of artificial regeneration methods, such as root deformation and lack of natural selection, are also discussed.