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• Trends of basal area growth and mean height were studied in the period 1983–2020. • The study was made for 20 to 60 year old pines and spruces in Sweden. • On average, mean height at a given age of both species has increased by 2 m. • The basal area growth level was stable in the period. • Current trees are becoming taller and slenderer in Swedish forests. Changes over time in annual basal area growth and mean height for Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) over the period, 1983–2020 were studied using sample tree data from temporary plots recorded in the Swedish National Forest Inventory. The annual basal area growth was derived from the last measured full ring on increment cores. Using 20 to 60-year-old dominant trees, the mean height and annual basal area growth were examined as functions of tree, stand and site conditions, and trends were assessed mainly using residual analyses over time. A significant increase in mean height at a given age was found for both species, but the annual basal area growth level remained stable over the 38-year period. Currently, at a given age of 50 annual rings at breast height, the mean heights of pines and spruces increased on average by 10.1% (i.e. ∼2 m), compared to 50 year-old pines and spruces in the 1980s, and the increase was similar in the different regions. The results suggest that trees have become taller and slenderer in Swedish forests. Increasing tree height over time at a given age in Northern Europe has been documented in several reports and many causes have been suggested, such as changed forest management, increasing temperatures and nitrogen deposition. We suggest that elevated CO 2 in the air and improved water-use efficiency for the trees might also be strong drivers. [ABSTRACT FROM AUTHOR]

Abstract: We tested hypotheses on the effect of growing space and biomechanics on tree growth, using data from two field experiments where Scots pine seedlings had been planted in a fixed but systematically irregular pattern. After 16 or 18 years, respectively, stem diameter was measured at 1.3m (d 1.3) and 0.3m above ground (d 0.3). Total tree height, length and diameter of the crown, and height to crown gravity point were also measured. Analyses were split in two parts: influence of growing space on tree and crown dimensions, and biomechanical influence of the crown on stem diameter. The results showed that crown size was closely related to tree height, and that there was a small but statistically significant effect of growing space on both crown size and shape. The biomechanical model explained about 85% of the variation in stem diameter, but growing space had no influence on this relationship, indicating that the wind load absorbed by a given crown size was not affected by growing space. The results were discussed in relation to future growth modelling and new ways of estimating site productivity. [ABSTRACT FROM AUTHOR]

Abstract: Natural mortality in a 30-year period was examined in thinning and fertilisation experiments with 48 blocks in Scots pine (Pinus sylvstris L.) and 23 blocks in Norway spruce (Picea abies (L.) Karst.) with up to 12 different treatments. Of about 90,000 living trees at start of the experiments 18.7% were registered as dead by natural mortality in the 30-year observation period. In non-thinned stands about 20% of the volume growth disappeared by natural mortality, in thinned stands about 10%. In normally thinned pine stands (repeated thinning from below with moderate intensity) the annual mortality of the basal area at start of an average 7-year period was 0.34%. In spruce stands, on more fertile sites, the corresponding figure was about 0.6%. In an effort to model the mortality, severe damage not leading to final felling was identified in 1.7% of the observation periods. It was assumed that this part of the mortality, representing 24% of the total volume mortality, could be recovered by active thinning. The probability for severe damage increased sharply with stand top height, as shown in a logistic regression. The more sparse mortality was expressed as a function of site fertility, stand density, disturbance by thinning and form of treatment (thinned from above or below or non-thinned). The naturally dead trees were approximately of mean size in normally thinned stands while the self-thinning in non-thinned stands tended to occur amongst smaller than average trees. Diagrams were presented for basal area development and stem number reduction in the non-thinned stands. [Copyright &y& Elsevier]

Abstract: Two field experiments, located in Central and Northern Sweden, were used to study the influence of standing volume on volume increment and ingrowth in uneven-aged Norway spruce (Picea abies (L.) Karst.) stands subjected to different thinnings. Each experiment had a 3×2 factorial block design with two replications. Treatments were thinning grade, removing about 45, 65, and 85% of pre-thinning basal area, and thinning type, removing the larger or the smaller trees, respectively. Each site also had two untreated control plots. Plot size was 0.25ha. Volume increment was 0.5–6.8m3 ha−1 year−1 for the plots, and significantly positively (p <0.01) correlated with standing volume. Within treatment pairs, plots thinned from Above had consistently higher volume increment than plots thinned from Below. Ingrowth ranged from 3 to 33stemsha−1 year−1, with an average of 14 and 21stemsha−1 year−1 at the northern and southern site, respectively. At the southern site ingrowth was significantly negatively (p <0.01) correlated with standing volume, but not at the northern site. Mean annual mortality after thinning was 2 and 7stemsha−1 year−1at the northern and southern site, respectively. [Copyright &y& Elsevier]

Retention of live and dead trees in harvested stands has become a common practice in Scandinavian forestry. We examined how retained Scots pines (Pinus sylvestris L.) grow and to what extent they compete with the new generation. In a mixed stand of about 5 ha in Northern Sweden, 44 retained pines and adjacent growth of the new stand was measured for the last 90 years. After liberation in 1912, the pines, then with a mean age of 180 years, doubled their annual ring width to a culmination after about 30 years. The trees below mean height showed the biggest response to liberation. The lower part of the stem (0.5–1.3 m) showed the largest growth relative to the decade before release during the first two decades after release. In the last decade the relative growth was largest at 6 m height. Growth of the new generation was measured on 9.5 m radius plots, centred on the retained pines. The growth of the new stand was reduced by 20% in the inner third of the plot area. With 10 evenly dispersed retained pines per hectare the production loss in the new generation was estimated at 2.5% over one rotation. The growth of retained trees more than compensated for this loss. The volume of the new stand was positively correlated with retained tree size and negatively correlated with retained tree growth. Of 17 species and species groups identified in the forest floor vegetation, only lichen occurrence correlated with distance to retained trees. Lichen was more common close to small and fast-growing retained trees. [Copyright &y& Elsevier]

Woody growth at five sites, covering a range of precipitation (620–785 mm) and soil conditions in North Sudan zone in Burkina Faso was investigated 5–14 years after clear-cutting. Woody growth ranged from 0.7 to 1.7 Mg ha−1 per year, corresponding to 1.0–2.4 m3 ha−1 per year in terms of green volume when species-specific basic densities were applied. Trunks (girth more than 10 cm), branches and stemlets made up about a third each of the yield and about one-third of the trunk was bark. Thus, the actual trunk wood production ranged from 0.2 to 0.7 Mg ha−1 per year corresponding to 0.3–0.9 m3 ha−1 per year. Woodfuel yield was reduced to about a fourth of the total yield, when excluding small dimensions and trunk-bark, species with low calorific value or multiple use, e.g. fruit bearing or forage. Each site was dominated by some few species in terms of percentage of dry mass: Sclerocarya birrea (13%), Anogeissus leiocarpus (57%), Acacia seyal (38%), Combretum glutinosum (17%) and Combretum nigricans (37%). Mean stool growth per site ranged from 0.5 to 1.7 kg per year. Largest stool growth was recorded for S. birrea and A. leiocarpus with 4.1 and 3.6 kg per stool per year, respectively. [Copyright &y& Elsevier]

Describes the large-scale introduction of exotic lodgepole pine Pinus contorta in Sweden after reviewing its species-specific properties and environmental requirements in native environment. Area covered by the lodgepole pine plantations in Sweden; Discussion on experiences of silvicultural practices; Analysis of ecological and environmental consequences of management alternatives.

Studies the ecological effects and management aspects of an exotic North American lodgepole pine tree Pinus contorta in Sweden. Area covered by the lodgepole pine tree plantation in Sweden; Suggestion on management of the plantations of these species to minimize the harmful effects of their introduction on ecosystem; Strategy to observe the adverse effects from the plantations for better Pinus contorta management.

Examines the effects of thinning and nitrogen fertilization on growth of 56-year-old Scots pine trees in northern Sweden. Measurement of response to treatments through dry weight biomass change in above and below ground components; Response to fertilization in radial and volume growth.

Examines the stand structure and fire trends in twelve virgin boreal forest reserves in Sweden. Average fire intervals in forests of the country; Standing volume of living trees and dead trees in forests; Effect of fire on spruce and sparse regeneration of pioneer species; Management practices to increase species diversity within forest reserves.

Examines three general methods for construction of site index equations for Pinus sylvestris using permanent plot data in Sweden. Comparison of growth functions with the construction methods; Results of the difference equation method; Indications of a changed growth pattern.

• Square design does not maximize productivity over rectangular designs. • No effect of rectangular designs on wood properties or stand heterogeneity. • Rectangular designs could provide higher flexibility in forest operations. • Rectangular spacing provides an opportunity for a flexible plantation layout. Historically square or almost square spacing design has been used in plantation forest, as it has been claimed to maximize productivity. In this study, based on field experiments established in the mid-1980s, we tested the effect of square or different rectangular planting designs (2 × 2, 1.33 × 3, 1 × 4, 0.8 × 5, 1.46 × 1.46 × 4 m) on productivity, stand heterogeneity, and external wood properties of three coniferous species: Scots pine, Lodgepole pine, and Norway spruce. Stand production (volume, diameter), external wood properties (ovality, branch thickness, living crown height, height-diameter ratio), and stand heterogeneity (Gini coefficient) were not significantly affected by the different rectangular designs. Based on this evidence, we propose that more flexibility is available than previously thought for rectangular spacing layouts and consequently for the choice of planting spots and machinery operations. [ABSTRACT FROM AUTHOR]