Spruce Planting in an Open Shelterwood Near the Timber Line

1990

S. 28-31

3 Abb., 5 Lit. Ang.

Unselbständiges Werk

200054458

Results of a 27 year old trial where spruce seedlings were planted in an open shelterwood near the timber line are reported. The objective of the trial was to investigate whether the long term yield could be increased by this system, compared to the conventional system with clear felling, followed by planting in the open. The trial is located at Enafors. The site is classified as maritime with an annual precipitation of 800 mm and 600 day degrees above 5C. Summer frosts are common. The vegetation type is a mesic herb type with blueberries and site productivity is estimated to 3.6 m3 (MAI) . The shelterwood consists of 240 stems per ha (90% spruce - 10% birch), unevenly distributed over the area, with an average diameter of 16 cm. Two thousand barerooted and four year old spruce seedlings per ha were planted. Planting was done one year after cutting. After 27 years the shelterwood trees have increased their volume from 22 to 66 m3 per ha, an increase of 44 m3 per ha. The seedlings have reached a height of 2.24 m, about 0.75 m less than would have been expected for opengrown seedlings (Figure 2). The delay in height growth corresponds to five years of development, and a loss of 18 m3 per ha over the rotation. Thus the volume gained from the shelterwood trees outweights the volume that will be lost in the new stand. It also appears that the survival under the shelterwood may be higher than on clear cut areas. This may be due to the lower risk of frost damages. 90% of the shelterwood seedlings have survived. In addition 1 300 spruce and 700 birch seedlings had been established naturally. In a spruce plantation on a clear cut area nearby the survival is 59%, with the survivors unevenly distributed. If the removal of the shelterwood trees is carefully carried out, it is unlikely that it will cause a major loss of seedlings. Underplanting of spruce in a shelterwood was clearly favourable for the volume yield in this case. In the future more attention should be paid to this regeneration system.