Direct seeding of Pinus sylvestris (L.) in the boreal forest using orchard or stand seed

• Main Author: Wennström, Ulfstand
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2001
• Subjects: Not in use; please see Agris categories; Northern Sweden
• Online Access: https://pub.epsilon.slu.se/11/; https://pub.epsilon.slu.se/11/1/91-576-6088-3.fulltext.pdf

The overall aim was to analyse the possibilities for operational forestry of using Pinus sylvestris (L.) orchard seeds (0s) for direct seeding in the boreal forest. The use of 0s instead of stand seeds (SS) increased seedling establishment by 41% two years after mechanical direct seeding at four sites in northern Sweden. 0s was advantageous to use in combination with microsite preparation to achieve desired spacing and different regeneration strategies, at low cost, and on an operational scale. On average, 0s had 16% and 12% higher seedling emergence than SS in a northern (Lat 64"N) and southern (Lat 60"N) field experimental series where six orchard seed lots and six stand seed lots of adequate geographical origins were analysed with up to six seeding years. The survival rate from year 1 to year 4 was 77% and 72% in the northern series and 58% and 49% in the southern series for orchard and stand seedlings respectively. On average, 0s were 26% and 13% taller than SS after four years in the northern and southern series, respectively. Effects on early seedling growth of seeding 0s and SS in different mixtures (100,75,50, 25, and 0% of 0s) at 4-cm target spacing were quantified in a nursery (optimal) and a field (harsh) experiment. SS in high competition vs. low competition (mixture 75% vs. 25%) were 11% taller, had 15% greater slender value, and 25% less root biomass after two years in the nursery. 0s had 9% greater slender value in mixture 100% compared to mixture 25%. In the field experiment the influence of mixture was not significant after five years. The tallest 0s in each plot compared with the tallest SS were 22% taller and had 103% larger stem volume. After thinning, leaving the tallest seedling in each plot, 79% of the seedlings in 50% mixtures would be 0s. Seedlings sown in 12-cm spacing were 79% taller and had 527% larger stem volume than seedlings in 4-cm spacing. An increase of seed weight from 3 to 7 mg increased height growth by 1845% and 10-27% in the field and nursery experiment, respectively. Seed ...