| 1. |
- Drössler, Lars, et al.
(författare)
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Simulated transformation of even-aged Norway spruce stands to multi-layered forests: an experiment to explore the potential of tree size differentiation
- 2014
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Ingår i: Forestry. - : Oxford University Press (OUP). - 0015-752X .- 1464-3626. ; 87, s. 239-248
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Tidskriftsartikel (refereegranskat)abstract
- The study investigated the possibility to transform normal young Norway spruce (Picea abies (L.) Karst) forests to develop more heterogeneous stand structures, aiming for multi-layered forest in the long run. On three sites in central and south Sweden, 60 per cent of stand basal area was removed by thinning mainly medium-sized trees and leaving the smallest and the largest trees. Over the next 50 years, future stand development was simulated using a single-tree growth model. Simulations were run with and without ingrowth. An additional ingrowth scenario after soil preparation was tested. Basal area was kept between 10 and 20 m(2) ha(-1) during simulations. Projected stem wood production for the next 50 years was one-third lower compared with conventional thinning regimes. After 50 years, a multi-layered forest structure was indicated for the boreal sites in central Sweden, but not for the site in south Sweden.
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| 2. |
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| 4. |
- Drössler, Lars, et al.
(författare)
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Occurrence and management of oak in southern Swedish forests
- 2012
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Ingår i: Forstarchiv. - 0300-4112. ; 83, s. 163-169
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Tidskriftsartikel (refereegranskat)abstract
- T his article describes the current proportions of forest types with oak (Quercus robur and Q. petraea) in southern Sweden, provides an overview of oak distribution over time and reviews literature about oak regeneration relevant for the region. Further we discuss silvicultural possibilities to maintain and promote oak in Scandinavia. In Götaland pure oak forest covers 1% of the forest area and mixed forest types with > 10% oak proportion cover approximately 10% of the area. Common types of mixture are spruce-oak and pine-oak forest. Both mixtures are frequent in mature forest, especially pine-oak. Additionally, about one third of spruce-oak mixtures can be found in medium-aged forest. I ntensive management would be necessary to promote single oak trees in old pine stands or spruce plantations, but the proportion of oak in coniferous forest provides some potential to maintain additional oak trees. The distribution of acorns by Jays, enhanced measures against browsing, and the release of single oak trees from competing tree species could help to maintain more oak trees for nature conservation. However, regarding management of oak for timber production, conventional methods are recommended. Planting after clear cutting of coniferous forest, or short shelter periods after mast years in oak stands, are established methods to regenerate pure oak stands. Another possibility to develop mature oak forest are mixed oak-spruce plantations, as traditionally practised in a small region in southern Sweden. The different approaches of oak management in Sweden were presented in April 2012 on the annual meeting of the section silviculture of DVFFA (German Union of Forest Research Organizations) in Wermsdorf near Leipzig to give an overview and access to recent forest research in Sweden.
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| 5. |
- Drössler, Lars, et al.
(författare)
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Stand structure and future development of a managed multi-layered forest in southern Sweden : Eriksköp - a case study
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- A heterogeneously structured forest stand with pine overstory and naturally regenerated spruce and oak trees in different size classes was documented. The effect of target diameter cutting on stand structure and growth was analyzed as a case-study. Both, systematic sample plots and forest gaps were used to describe the stand structure after cutting. Target diameter cutting in different treatments reduced the standing volume from ca. 320 to 180 m³/ha. Forest canopy gaps were created on more than 15% of the stand area. The seedling number of advanced natural regeneration was low (less than 500-1000 individuals per ha). Based on the advanced regeneration in gaps, three different scenarios for future ingrowth into the tree layer were defined. The extreme minimum ingrowth scenario assumed about 10 cm annual height growth and rather high mortality reported in literature from other experiments (resulting in one tree annually reaching 5 cm DBH during the next 50 years). Two other scenarios assumed 20 and 30 cm annual height growth. While no mortality was presumed within the latter scenario, moderate mortality rates (reported in literature) were chosen for the intermediate scenario. The maximum scenario postulates ten trees per year and ha reaching 5 cm DBH (equal to ingrowth reported from boreal single-tree selection forests). The moderate scenario assumes four new trees per year and he. Additional scenarios after soil preparation in gaps were used, defined on the base of shelterwood experiments. To describe the future basal area growth and continued target diameter cutting in the next 50 years, a single-tree growth model was applied, using stand age-independent estimations of the age of single trees. Thereby, a mean annual increment of 0.53-0.64 m2/ha was projected, similar to 5.6-6.8 m³/ha volume. Some errors to estimate the standing volume in multi-layered stands were detected during the simulation process. Compared to an evenaged spruce stand planted on the same site, the expected growth of the study stand during the next 50 years was one third lower. In average, about 120 m3/ha standing volume was removed in 20-25 years-cutting cycles. To continue without longer harvest intervals after the 50 years-simulation period, soil preparation seems necessary to achieve a sustainable number of small trees. Beside timber production, profitability was also lower by selective cutting. But, the important advantage of target diameter cutting can be more equally distributed income over time, with investments costs that can be covered by profit from timber harvest at the same time. A regular income of 17000-28000 SEK per ha every 20-25 years seems possible from today´s perspective. An additional treatment with alternative target diameters to promote particular tree species did not affect the amount of removals and the length of cutting intervals substantially. But simulations with 5 cm reduced target diameters caused very heavy removals and 35-40 years to reach 300 m³/ha standing volume again. The study includes discussions of tree species composition and development as well as a sensitivity analysis of the applied growth model.
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| 6. |
- Drössler, Lars
(författare)
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Suitability of close-to-nature silviculture for adapting temperate European forests to climate change
- 2014
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Ingår i: Forestry. - : Oxford University Press (OUP). - 0015-752X .- 1464-3626. ; 87, s. 492-503
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Forskningsöversikt (refereegranskat)abstract
- In many parts of Europe, close-to-nature silviculture (CNS) has been widely advocated as being the best approach for managing forests to cope with future climate change. In this review, we identify and evaluate six principles for enhancing the adaptive capacity of European temperate forests in a changing climate: (1) increase tree species richness, (2) increase structural diversity, (3) maintain and increase genetic variation within tree species, (4) increase resistance of individual trees to biotic and abiotic stress, (5) replace high-risk stands and (6) keep average growing stocks low. We use these principles to examine how three CNS systems (single-tree selection, group selection and shelterwood) serve adaptation strategies. Many attributes of CNS can increase the adaptive capacity of European temperate forests to a changing climate. CNS promotes structural diversity and tree resistance to stressors, and growing stocks can be kept at low levels. However, some deficiencies exist in relation to the adaptation principles of increasing tree species richness, maintaining and increasing genetic variation, and replacing high-risk stands. To address these shortcomings, CNS should make increased use of a range of regeneration methods, in order to promote light-demanding tree species, non-native species and non-local provenances.
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| 7. |
- Drössler, Lars
(författare)
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Tree species mixtures – a common feature of southern Swedish forests
- 2010
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Ingår i: Forestry. - : Oxford University Press (OUP). - 0015-752X .- 1464-3626. ; 83, s. 433-441
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Tidskriftsartikel (refereegranskat)abstract
- The proportions of forests in southern Sweden with the most common single or mixed species compositions were determined using the data provided by the Swedish National Forest Inventory. Forests including a second tree species with a basal area of at least 10 per cent, in addition to the most abundant species, were defined as mixed forests. The most common compositions were spruce, pine/spruce, pine and spruce/birch. Overall, mixed forest was more common than single-species forest, and approximately two-thirds of both spruce-dominated and pine-dominated forests included a sufficient proportion of other tree species to be classified as mixed forests, according to the above definition. Differences in composition related to age, site and ownership classes were analysed. Hypotheses that pine/birch mixtures only occur in early-successional stages and that spruce/birch mixtures occur mainly on wet sites were rejected. In fact, 90 per cent of spruce/birch mixtures were found on mesic and moist-mesic sites. The hypothesis that pine/spruce mixtures are more frequent in private forest was also rejected. In conclusion, the study found high proportions of mixed forest across age and site classes and provides background information for assessing the potential to refine silvicultural methods applicable, e.g., to young spruce/birch or very old pine/spruce stands
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| 8. |
- Drössler, Lars
(författare)
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Vorstellung einer Initiative zur Auswertung von Mischwaldexperimenten in Europa
- 2011
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Ingår i: Jahrestagung - Deutscher Verband Forstlicher Forschungsanstalten, Sektion Ertragskunde. - 1432-2609. ; , s. 81-81
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An initiative of several European countries to search for long-term experiments with comparisons of the productivity in mixed and pure stands was announced. The goal is to present all these experiments in one English publication, to conduct a meta-analysis regarding production, to reveal some rough ecological pattern, and to discuss the limitation of such an analysis
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| 9. |
- Felton, Adam, et al.
(författare)
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Adapting production forests in southern Sweden to climate change Constraints and opportunities for risk spreading
- 2010
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Ingår i: International Journal of Climate Change Strategies and Management. - : Emerald. - 1756-8692. ; 2, s. 84-97
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Tidskriftsartikel (refereegranskat)abstract
- Originality/value - Conceptual equivalents of the "risk spreading" approach are international, due to the need for many societies to adapt social-ecological systems to climate change. The issues raised from this case study/synthesis provide value insights regarding the breadth of systemic constraints which can thwart attempts at rapid adjustment to climate change, and where solutions to these constraints may be found.
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