Interactions between site preparation, seedling type and genetics on the establishment of Norway spruce

Abstract

Effects of site preparation methods on establishment and growth of different seedling types and clones of Norway spruce were examined in this project. Two studies were established in the southern parts of Sweden. The first study aimed at investigating the effects of mulch and scarification on growth of six clones of Norway spruce in the form of rooted cuttings. In the second study, interactions between scarification treatments, including non scarified control, mounding and soil inversion, and seedling types of Norway spruce were examined at two different locations. The three different seedling types used in the experiment were a 10 weeks old containerized seedling referred to as mini seedling, a 2 year-old containerized seedling and a 2 year-old hybrid seedling (grown both as a containerized- and a bare root seedling).

Mulch and scarification reduced amount of competing vegetation. Bud break occurred earlier for cuttings planted in scarification compared to control and mulch. Gas exchange and the number of new roots were higher in planting spots covered with mulch. Mulch and scarification affected survival and growth of the cuttings after the second growing season positively. Height growth was 32 mm greater and biomass increment 6 g higher in plots treated with both scarification and mulch compared to the control. Clonal differences regarding gas exchange and growth were significant. Clone 1100 had poor biomass growth, height growth and gas exchange and the lowest amount of new roots. Clone 2136 achieved the highest biomass and height growth after two years. This clone had high gas exchange values and a large number of new roots compared to clone 1100. In this study, clonal effects on growth were greater than site preparation effects.

Scarification increased survival of the mini seedlings. Differences in growth between the control and scarification treatments were relatively greater for the mini seedling than for the two larger seedling types. Interactions between seedling type and scarification method for growth indicates that the mini seedlings were able to establish faster in the soil inversion treatments compared to the larger seedling types. Comparing growth rates at the same seedling age, biomass and height growth of the mini seedlings were higher or similar as for the containerized and the hybrid seedling in all scarification treatments. At the age of 3 years in the soil inversion treatment, height of the mini seedlings was 600 mm and for the hybrid seedlings the height was 400 mm. Results from this study show that mini seedlings can grow as well as or even better than larger seedlings if they are successfully established. However, mini seedlings are more sensitive to their planting environment and proper handling is critical. Problems with frost heaving and competing vegetation can be a problem and has to be taken into consideration when choosing site preparation method.