Per-Magnus Ekö

The effects of shelterwood density and site preparation on natural regeneration of Fagus sylvatica in southern Sweden

Abstract The natural regeneration of beech (Fagus sylvatica) was studied under various shelterwood densities and soil preparations in a 130-year-old beech stand in southern Sweden. Between 1990 and 1996, seedling emergence, survival, growth and damage were followed in a clear-cut and in two shelterwoods with different densities, in plots with undisturbed ground, bare mineral soil or ridges with mineral soil on top of humus. Irradiation, soil and air temperatures, soil moisture and precipitation were continuously recorded during the first three growing seasons. The seedling emergence was higher in the shelterwoods than in the clear-cut. The mortality was the highest during the first year. The seedling number was the highest on bare mineral soil and the lowest on undisturbed ground, for all cutting regimes. The increase in seedling height and dry mass was greater in the clear-cut and in the sparse shelterwood than in the dense shelterwood. Damage due to frost was more frequent in the clear-cut than in the shelterwoods. Effects of most kind of damage had only minor influence on the seedling height, whereas in seedlings experiencing frequent damage height was reduced.

Scarification and seedfall affects natural regeneration of Scots pine under two shelterwood densities and a clear-cut in southern Sweden.

A study was undertaken to evaluate the effect of Scots pine (Pinus sylvestris) shelterwood density and timing of removal on the regeneration of forests with improved wood quality. This paper focuses on the effect of scarification and seedfall on the success of natural regeneration of Scots pine under two shelterwood densities and in a clear-cut. Wood quality aspects will be addressed later in the study. After 4 yrs, natural regeneration of Scots pine under a 200 stems ha-1 shelterwood reached 90000 seedlings ha-1, 53000 under a 160 stems ha-1 shelterwood and 3700 in a clear-cut. The high natural regeneration under the densest shelterwood resulted from a high seedfall, slower invasion by competing vegetation, consequent prolonged recruitment and low mortality. Since mortality largely decreased for both shelterwood densities and recruitment seems to continue, the success of regeneration should be maintained in the future if proper release operations are conducted. The latter could begin when seedlings reach a height of about 0.5 m and the cover should be maintained until they reach a height of about 6 m. Therefore, it may be possible to use 200 stems ha-1 Scots pine shelterwoods in southern Sweden to obtain dense stands and thus improve wood quality (stem taper, wood density, etc.).

Tree Properties and Yield of Picea abies Planted in Shelterwoods

Tree properties affecting timber quality and yield were examined in six stands of Norway spruce [Picea abies (L.) Karst.] planted in shelterwoods. For each stand a pairwise comparison was made with trees planted in the open. When compared 16 - 32 yrs after planting, the sheltered trees were generally shorter and had thinner trunks than the open - grown ones. Furthermore, sheltered Norway spruce had thinner branches, a lower average annual ring width and a lower frequency of defects such as spike knots, forked stems and sharp bends. The reduction in ring width was significant for ring numbers 1 - 5 and 6 - 10. No significant differences in basic density were detected between treatments. The yield of Norway spruce was lower for sheltered trees than for those growing in the open. Total volume yield, however, including shelter trees, was higher on the sheltered plots.

Influence of precommercial thinning grade on branch diameter and crown ratio in Pinus sylvestris in southern Sweden

Precommercial thinning is regarded as one of the most important measures for influencing timber quality in stands of Scots pine (Pinus sylvestris L.). The present study considers the influence of both thinning intensity and tree height at the time of thinning on diameter of the thickest branch and crown ratio. A total of 115 plots (either naturally regenerated, planted or sown, and either thinned down to 528–8000 stems ha−1 or untreated) included in 20 sites in southern Sweden were analysed. The average tree height after thinning varied from 1.2 to 8.3 m. An increasing number of remaining stems resulted in a reduction in branch diameter, although the reduction appeared to be only minor if the number of stems after thinning was more than 3000 stems ha−1. It was found that late thinning reduced the diameter of the thickest branch. The crown ratio decreased with stand height, number of stems after thinning and average height at thinning. The results were consistent for all trees and for the 500 thickest trees per hectare.

Current growth differences of Norway spruce (Picea abies), Scots pine (Pinus sylvestris) and birch (Betula pendula and Betula pubescens) in different regions in Sweden

Abstract The choice of species in forestry is important, and a real issue as large areas of wind-damaged forest land in southern Sweden need to be regenerated. To compare the growth potential between the most common tree species in Sweden, ratios between site quality derived from site index values determined with site properties were used. A regression function to determine site index for birch from site properties was used to complement the known relationships between site properties and site index for spruce and pine. In large regions of Sweden the distribution of site quality classes was calculated to compare the special characteristics and demands of the three species. On average, the growth difference for pine compared to spruce was about 60% in southern Sweden and 95% in northern Sweden. Corresponding figures between birch and spruce were 40% and 60%. Birch was expected to produce around 60% of pine in northern Sweden and about 70% in southern Sweden. However, it must be stressed that the comparison is based on survey data encompassing mainly naturally regenerated birch, whereas spruce and pine are mainly planted.

Effects of wide spacing and thinning strategies on wood quality in Norway spruce (Picea abies) stands in southern Sweden

Abstract The initial density of a stand influences both the prethinning growth and the quality of the harvested trees. This study investigated the effects of different square spacings (2.0, 2.5 and 3.0 m) with thinning from above and thinning from below on stand development and tree characteristics in a 33-year-old Norway spruce [Picea abies (L.) Karst.] plantation in southern Sweden. Before thinning the total standing volume was not significantly different between treatments. Diameter at breast height (dbh) and diameter of the thickest branch were positively correlated. Before thinning, dbh of the trees and their thickest branches were significantly higher in the stands with 3.0 m spacing. After thinning, the dbh and the diameter of the thickest branch did not significantly differ between the 3.0 m spacing with thinning from above and 2.0 and 2.5 m spacing with thinning from below. Spacing did not significantly influence the presence or size of spike knots. The results suggest that a combination of wide spacing with thinning from above may yield timber of similar quality to denser spacing with thinning from below.