Arne Albrektson
Swedish University of Agricultural Sciences
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Featured researches published by Arne Albrektson.
Forest Ecology and Management | 1996
Göran Örlander; Gustaf Egnell; Arne Albrektson
Abstract Effects of soil scarification on long-term site productivity up to 70 years, and soil content of carbon (C), nitrogen (N), and macro nutrients, were studied in five site preparation experiments, established between 1922 and 1965 on Scots pine ( Pinus sylvestris L.) heathland, on poor sandy sediments. The soil was inverted by spade, hoed, harrowed or ploughed. All scarification methods disturbed close to 100% of the soil surface, the most radical treatments to a depth of approximately 20 cm. Some of the experiments had an inadequate original design. However, by comparing the experiments some general characteristics were found. Site productivity measured as top height was higher on scarified plots than on control plots ( P
Forest Ecology and Management | 1993
Urban Nilsson; Arne Albrektson
Abstract It has been suggested that the allocation of carbon to stem wood growth has low priority, and that productivity of needles (above-ground tree biomass increment per unit leaf weight) decreases as competition between trees increases. To test this, carbon allocation to different growth components and productivity of needles were compared between trees of different tree classes (dominant, codominant, intermediate and suppressed). The study was carried out in two 16-year-old Scots pine (Pinus sylvestris L.) stands, planted at different initial densities: 40 000 and 10 000 seedlings ha−1. It was found that the allocation of carbon to stem wood production, and probably also fine root production, has high priority for trees under hich competitive stress. It was also found that production per unit weight of needles increases with competition; at least for as long as the trees are experiencing approximately the same light regime.
Scandinavian Journal of Forest Research | 1988
Arne Albrektson
Current annual needle litterfall was analysed in 16 Scots pine stands of different ages, site qualities and latitudes. As a mean, the current needle litterfall was 1605 kg (dw) per ha and year, corresponding to a current annual volume increase of 7.9 m3. It was shown that the needle litterfall 1) increased with increasing site quality, 2) decreased with increasing stand age, and 3) decreased with increasing latitude. An increase in the number of living age classes of needles in the tree crowns with increasing latitude was observed. This should be considered if total needle biomass in the crowns is to be estimated from litterfall. A method is proposed for calculating current annual needle litterfall in Pinus sylvestris stands of any age, site quality or latitude in Sweden.
Scandinavian Journal of Forest Research | 1992
Annikki Mäkelä; Arne Albrektson
An allometric relationship between foliage biomass and crown surface area is investigated in a data set consisting of 54 fertilized and 99 unfertilized Scots pine (Pinus sylvestris L.) trees from 16 stands in Central Sweden. The allometric ratios for the unfertilized trees are shown to be weakly correlated with competition defined as tree height relative to dominant height (r = 0.475), and with crown coverage (r = ‐0.563). A slight level difference in the ratios can be detected between stands of different site moisture index. The overall relationship is nonlinear but becomes linear if the coefficient of proportionality is made dependent on stand average crown coverage. This also improves the percentage of explanation, which suggests that the allometry of the crown is related to the light conditions of the tree. Under fertilization, the relationship between foliage biomass and crown surface area seems less stable, at least if measured shortly after fertilization.
Scandinavian Journal of Forest Research | 2002
Anders Karlsson; Arne Albrektson; Björn Elfving; Clas Fries
Reducing competition by point cleaning may be an attractive alternative to conventional precommercial thinning in forestry. In this study, survival and development of main stems of Scots pine (Pinus sylvestris L.) following point cleaning were examined in a mixed stand of mainly Scots pine and birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Sweden. Treatments studied were: no precommercial thinning, conventional precommercial thinning, point cleaning of all secondary stems, and point cleaning of only the secondary stems that were higher than the main stem, within a radius of 0.8 m from the main stem, respectively. A randomised complete block design with three replicates was used. Measurements taken 13 growing seasons after these treatments showed that conventional precommercial thinning was the best treatment for retaining Scots pines as main stems. However, conventional precommercial thinning resulted in the poorest timber quality of the remaining Scots pines in terms of stem taper, thickest branch diameter and relative live crown height. In conclusion, point cleaning has to be followed by a complementary cleaning operation if the objective is to retain Scots pines as main stems in such mixed stands.
Scandinavian Journal of Forest Research | 2003
Karin Fällman; Daniel Ligné; Anders Karlsson; Arne Albrektson
Topping may provide an attractive alternative to traditional precommercial thinning, offering several advantages. The main stem quality of birch (Betula pubescens Ehrh. and Betula pendula Roth, species not separated) was examined seven growing seasons after such topping in a dense, even-aged and naturally regenerated stand in northern Sweden. The height development and survival of main and secondary stems of birch and secondary stems of willow (Salix spp.) were also studied. At a main stem height of 1.8 m, the following treatments, leaving 3100 main stems ha−1, were applied to secondary stems: traditional precommercial thinning (cutting just above ground), top-cutting at either 40% (71 cm above ground) or 70% (120 cm above ground) of main stem mean height, and no precommercial thinning. For main stems, topping resulted in fewer forks, straighter stems, higher live crown height and smaller diameter of the thickest branch compared with traditional precommercial thinning. In these respects, topping at the higher level above ground gave the best quality. The main stems were no longer at risk of becoming overtopped by the secondary stems following any of these treatments (except for no precommercial thinning).
Scandinavian Journal of Forest Research | 2000
Anders Karlsson; Arne Albrektson
Karlsson, A. and Albrektson, A. (Swedish University of Agricultural Sciences (SLU), Department of Silviculture, SE-901 83 Umeå, Sweden). Height de6elopment of Betula and Salix species following precommercial thinning at 6arious stump heights: 3-year results. Received April 8, 1999. Accepted September 19, 1999. Scand. J. For. Res. 15: 359–367, 2000. Topping, to reduce competition, may be an attractive alternative to traditional precommercial thinning in forestry for both biological and financial reasons. In this study, the height development of secondary and main stems of birch (Betula pubescens Ehrh. and Betula pendula Roth, species not separated), and secondary stems of willow (Salix spp.) was examined in a field experiment in northern Sweden. Treatments studied were: traditional precommercial thinning, topping at 40% of main stem mean height, topping at 70% of main stem mean height, and controls (untreated). Post-treatment damage to the trees was frequent for both genera, but especially for the willows. Treatment rankings for all of the secondary stems, and for undamaged secondary stems, according to height development after three growing seasons, were topping at 70%]no treatment] topping at 40%] traditional precommercial thinning. The results also indicated that the cross-cutting level could be raised to a level of at least 40% of main stem height, without risking the main stems becoming overtopped. During the study period, 67% of the main stems exchanged their leading shoots at least once.
Scandinavian Journal of Forest Research | 1997
Anders Karlsson; Arne Albrektson; Johan Sonesson
Site index and productivity of artificially regenerated stands of silver birch (Betula pendula Roth) and downy birch (Betula pubescens Ehrh.) on former farmland in southern and central Sweden were examined. The material comprised sample plots in 27 stands, measured in both 1990 and 1993. Silver birch was the dominating species in most stands, and the average site index (SI) was nearly 28 m. Site quality ranged from 5.3 m3 ha−1 yr−1 (equivalent, from tables, to a SI of 22 m) to 11.4 m3 ha−1 yr−1 (equivalent to an extrapolated SI of 32 m). Soil moisture was the only site factor tested that significantly affected SI for silver birch. Moist sites were found to be inappropriate for this species especially on fine‐textured sediment soils. On moist sites, SI for downy birch was as high as SI for silver birch. Growth of artificially regenerated silver birch on former farmland differed significantly from growth of naturally regenerated birch on forest sites, according to two Swedish growth simulators.
Forest Ecology and Management | 1994
Urban Nilsson; Arne Albrektson
Abstract Two neighbouring young stands of Scots pine ( Pinus sylvestris L.) with different initial densities were analysed, allowing the study of competition on an individual tree basis. The development of growth and self-thinning of trees of different competitive status was examined over a period of time, from planting until the time for late pre-commercial thinning. Differentiation into different tree classes took place relatively early. About 6–7 years after planting, trees that were classified at year 16 as dominant, were significantly larger in stem volume than trees that were classed as suppressed. The conclusion was that events that take place early in the stand development have great importance for later stand structure.
Scandinavian Journal of Forest Research | 2004
Per Magnus Ekö; Marie Larsson Stern; Arne Albrektson
The interest in growing hybrid larch (Larix×eurolepis A. Henry) in Sweden has increased during the past few decades. This is mainly due to expectations concerning rapid growth, resistance to butt rot and durability of the wood. A yield study in hybrid larch was conducted based on 28 plots in southern Sweden. The plots were established on fertile sites in stands managed in practical forestry. A growth model was developed, including regression functions for basal area increment, stand form-height development and initial basal area. Top height growth curves from a Norwegian study were also included in the model. A yield table was calculated for the age span 15–45 yrs. The calculations showed that the yield of hybrid larch in southern Sweden compared with Norway spruce was slightly higher and especially more rapid when young. On fertile sites the mean annual volume growth peaked at an age of 35 yrs, at a level of 13 m3 ha−1.