Björn Hånell

Effects on the flora in Norway spruce forests following clearcutting and shelterwood cutting

Abstract Clearcutting and shelterwood cutting of mature Norway spruce peatland forests were compared regarding the effects on the forest flora. Repeated observations of the field and bottom layer vegetation were made before and until 7 or 8 years after harvesting at four sites located along a gradient from southern to northern Sweden. Clearcutting resulted in a greater change of species composition compared with shelterwood cutting. Diversity, measured as Simpsons index, and species number per subplot were lower in the clearcut than in the shelterwood after 7 or 8 years. By applying Ellenbergs indicator values, it was concluded that shelterwood regimes may preserve species preferring shaded and moist conditions, whereas those species decreased after clearcutting. Species preferring high levels of nitrogen increased in the clearcut. According to both multivariate and univariate analyses, the vegetation changed in a similar direction at all sites, although the level of response differed considerably. Despite these similarities, there was a marked site effect, which was not surprising considering the large geographic variation between sites. It is concluded that shelterwood cutting might be a better alternative than clearcutting for forests on fertile peatland sites, with respect to conservation of vascular plants and bryophytes.

Productivity and Costs in Shelterwood Harvesting

Harvesting costs have a significant influence on the application and potential use of the shelterwood system. These costs are strongly related to the time needed for the logging operations. In this study, which was carried out in Norway spruce [Picea abies (L.) Karst.] stands in northern Sweden, the effective time (E 0) of a single-grip harvester in shelterwood cutting, thinning of shelterwoods and clearcutting was measured. Based on these data the costs of shelterwood harvestings and clearcutting were calculated and compared. It was found that (1) the time per tree in shelterwood cutting and thinning of shelterwoods was greater than in clearcutting, (2) the time per cubic metre was higher in sparse shelterwoods than in dense shelterwoods, (3) most of this increase was due to longer driving time because fewer trees were harvested, and (4) the longer time and higher logging costs in the shelterwood system (compared with the clearcutting system) were mostly related to the establishment of the shelterwood. It was concluded that the shelterwood alternative is especially competitive when it is desirable to maximize the share of saw logs at the expense of pulpwood.

Greenhouse gas fluxes from drained organic forestland in Sweden

Abstract The objective of this study was to estimate the contribution of drained organic forestlands in Sweden to the national greenhouse gas budget. Drained organic forestland in Sweden collectively comprises an estimated net sink for greenhouse gases of −5.0 Mt carbon dioxide (CO2) equivalents year−1 (range −12.0 to 1.2) when default emission factors provided by the Good practice guidance for land use, land-use change and forestry are used, and an estimated net source of 0.8 Mt CO2 equivalents year−1 (range −6.7 to 5.1) when available emission data for the climatic zones spanned by Sweden are used. This discrepancy is mainly due to differences in the emission factors for heterotrophic respiration. The main uncertainties in the estimates are related to carbon changes in the litter pool and releases of soil CO2 and nitrous oxide.

Changes in the vascular plant vegetation after different cutting regimes on a productive Peatland site in Central Sweden

We studied the changes in vascular plant vegetation in the first five years after final felling of a mature Norway spruce (Picea abies (L.) Karst.) forest on a productive peatland. Vegetation changes following clearcutting and selective cutting (shelterwoods with the density 140 and 200 stem ha‐1) were compared. The total cover of the understory increased three times on the clearcut and more than twice in the shelterwoods. The relative decrease of the three most common species was from 73% to 3% on the clearcut and 79 to 28% under the shelter trees. Six of the 16 most common species in the mature forest almost disappeared on the clearcut. In contrast, in the shelterwoods, few species decreased and twelve of the most common species remained the same or increased their cover.

Diameter Increment in Picea abies Shelterwood Stands in Northern Sweden

In this study, the effect of shelterwood density on radial increment and stem form changes was evaluated after 9 yrs for a trial in a forest in northern Sweden dominated by Norway spruce [Picea abies (L.) Karst.]. Radial increment increased after the shelterwood cut, compared with control stands. The effect was of the same magnitude for sparse and dense shelterwoods. The response started in the third growing season and increased until the seventh season after release. The relative increment response was highest in the lower parts of the tree trunk, which indicates a reallocation of increment during the shelterwood period, causing a slight taper deterioration.

Regeneration of Picea abies forests on highly productive peatlands—clearcutting or selective cutting?

The study was focused on severe forest regeneration problems that are typical for highly productive peatlands. The aim of the study was to give recommendations for practical forestry on how to renew the forests. Experiments with different forest regeneration methods on highly productive peatlands were set up in nine mature Norway spruce (Picea abies (L.) Karst.) forests in northern, central and southern Sweden. The treatments in the study were natural regeneration in shelterwoods (at densities of 140 and 200 stems ha‐1), planting of bare‐root spruce seedlings after site preparation (mounding) in the shelterwoods and on clearcuts, and planting without site preparation on clearcuts. Judging from the extent of windthrow in the denser shelterwoods and the stocking of natural regeneration under remaining shelter trees 4–5 years after final cut, shelterwood regeneration is a promising method. On clearcuts, planting without site preparation resulted in poor seedling survival, large extent of damage to the seedli...

Windthrow after Shelterwood cutting in Picea abies Peatland forests

The aim of the study was to address the question of whether shelterwood cutting should be discouraged as a forest regeneration method in Norway spruce (Picea abies (L.) Karst.) forests on highly productive peatlands due to a higher risk of windthrow in such forests. The total extent of windthrow was observed during six years after shelterwood cutting in nine spruce forests on fertile peatlands in north, central and south Sweden. Shelterwoods at densities of 140 and 200 stems ha‐1 were studied. At the end of the six year study period, 43% of all trees in the sparser shelterwoods and 38% of the trees in the denser shelterwoods had blown down. With respect to results from recent studies of the development of naturally regenerated and planted seedlings under the shelter trees, the extent of windthrow was regarded acceptable. Analysis of wind data from national weather stations close to the experiments showed that the acceptable extent of windthrow could not be explained by low frequencies of high winds during...

Afforestation of low-productivity peatlands in Sweden — the potential of natural seeding

In 1971, a series of five afforestation trials were established along a north-south gradient on open peatlands in Sweden. All areas were drained, fertilized and planted with Scots pine (Pinus sylvestris). Survival and height of the planted trees as well as the amount of natural establishment, i.e. downy birch (Betula pubescens), silver birch (Betula pendula), Norway spruce (Picea abies (L.) Karst.), Scots pine (Pinus sylvestris L.), and other deciduous species: (e.g. Salix sp., Sorbus aucuparia), by seeding from nearby forests were measured 18–22 years later. The amount of naturally established trees exceeded the number of living planted trees in all five areas. Next to downy birch, Scots pine was the most common naturally established species. Large variations in both amount and height of natural establishment were found along the climatic gradient. Planted trees were taller than naturally established trees, except for the northernmost area. Number and height of naturally established trees correlated positively to closeness to nearest forest and to nearest ditch. These trees also responded positively to PK fertilization in the three southernmost areas. In the two northernmost areas no such response was found. It was concluded that natural seeding from neighbouring forests can be counted on and recommended in afforestation of low-productive peatlands in Sweden, provided that downy birch is accepted as a dominant tree species.

Swedish forest research and higher education ‐ challenging issues and future strategies of forest research and education in Sweden

This paper gives an overview of current forest education in Sweden and its historical development. In Sweden, education and research is dominated by one actor, the Faculty of Forest Sciences at the Swedish University of Agricultural Sciences (SLU). In this paper, we discuss the values of a solid academic base, a close cooperation between research and development, and the best balance between theory and practise. We conclude that the overall challenge for Swedish Forest education, and indeed for comparable natural sciences programmes in other countries, is to widen the scope to include more social and humanistic aspects of forests and forestry. Management of “multifunctional forestry” best describes the vision we aim at. The change in syllabus, compared to current education, must of course differ among countries due to different forest and land use history and conditions. We wish to emphasize that in case of Sweden, a country where production forests are the economically most important natural resource, this recommendation is not a general shift of focus away from forest production. We do mean however, that the academics working in forestry must be equipped with sufficient knowledge about environmental issues and other functions of forests to be able to cope with future demands. We also wish to emphasise the international perspective of forestry. At the individual level students should be provided possibilities to take full master degrees (majors) in other subjects than Forest Management (e.g. Biology, Soil Science, Economics). We believe that there are some important requirements to keep higher education in Forest Sciences competitive and successful in the long term: a solid academic/ scientific base; a close association between research and teaching; and a mix of theory and practise/field studies. Forestry studies should be challenging to the students and provide them possibilities for personal development that enables them to meet unknown demands in the future.