FR01

In October 2023, Pro Silva Ireland arranged a short study tour to learn about continuous cover forestry (CCF) in central Jutland. The group was hosted by Pro Silva Danmark and focused on conifer plantations at various stages of transformation to CCF. This report provides a brief description of each forest visited during the excusion and includes three galleries of images that illustrate the species, silvicultural systems and woodland conditions discussed at each site.

Forests in Denmark

There are 640,835 ha of forest in Denmark, corresponding to 14.9% of the land area. Danish forests comprise state-owned forests, managed by the Nature Agency’s local units, as well as many privately-owned forests and woodlands.The public forest estate amounts to 115,000 ha (18% of total forest area) and the private sector extends over 525,835 ha (82%), made up of small private woodlots and large forest holdings. (All statistics quoted are from the Danish Ministry of Environment 2023.)

The forests are unevenly distributed from region to region, with concentrations of woodland along the high ridge of Jutland (the focus of the study visit), in northern Zealand and on the island of Bornholm. Smaller areas of wood are located near large towns and cities. More than 17% of the Capital Region, which includes northern Zealand and Bornholm, is forested, compared with 11.2% forest cover in the Southern Denmark region.

The forest composition is 44% broadleaves, 35% conifers and 11% mixed forest. Most broadleaved species, including oak, birch, beech and aspen, are native to Denmark, while many conifer species have been introduced over the past 200-300 years. The most common tree species is Norway spruce (19% of forest area), which was introduced from other European countries including Sweden and Germany, while species such as Sitka spruce and Douglas fir were introduced from North America. Native conifers include Scots pine, juniper and yew.

Denmark is among the least forested countries in the EU. In this regard, it shares a very similar forest history to that of Ireland and the UK. Most of Denmark was originally covered by woods, but after centuries of uncontrolled felling and clearance for agriculture, just 2-3% of Denmark was covered by forest around 1800. Since the Danish Forest Act was passed into law in 1805, forest clearance has been banned in Denmark, and at the same time great efforts were initiated to plant more forests. The national forest estate has therefore increased significantly. Large areas of woodland were established from the 1860s in central Jutland on land that was abandonned or unsuitable for agriculture. Forestland continues to be established throughout Denmark, in particular on moorland and sand-dunes in central and west Jutland.

Non-native conifers have been very successful in Denmark. Annual precipitation ranges from around 800-1000 mm. Most species thrive on soil that is relatively poor in nutritional value, and many grow well on heaths and dunes, which are prevalent in Jutland. Conifers have been favoured throughout this region because they are generally more profitable for forest owners than broadleaved trees. Nonetheless, the important role of native broadleaves is recognised for soil improvement, diversity and habitat values.

Closer-to-Nature Forestry

As elsewhere in Europe, forest policy in Denmark has evolved and aims to balance a range of environmental, economic and social values. A key objective is to preserve the biodiversity and habitat value of natural forests. The Nature Agency now manages all their forests in accordance with close-to-nature principles. Enhancing species and structural diversity of the forests are important features of current stewardship, to promote forest resilience in response to threats from climate change and forest pathogens. The work of Pro Silva Danmark is especially important as a forum for sharing knowledge and experience in the application of CCF principles.

Excursion Itinerary

The excursion took place from 12-15 October 2023 and focused on three woodlands in central Jutland, all located in the forested region to the south of Silkeborg. The dominant physiographic features include a high ridge of glacial origin, numerous lakes and heathland. The woodlands represent three distinct types of ownership and management structure. The first visit (13 Oct. 2023) was to a large private estate. The second visit (14 Oct. 2023) was to an extensive area of woodland under multiple ownerships but managed by a single forestry company. The third visit (15 Oct. 2023) was to a small private woodlot. All three woodland areas are now undergoing transformation to continuous cover forestry following a long history of even-aged/plantation forest management. Most of the stands visited on the tour were 2nd or 3rd rotation plantations now being managed on shelterwood and selection silvicultural systems to make greater use of natural regeneration and to promote stand structural irregularity. The group was based throughout the visit in the city of Silkeborg. The detailed itinerary is here.

Day 1. St. Hjøllund Plantage (Estate), Hampen, Central Jutland

Hosts: Poul-Arne Madden and Søren Strunge.

At this forest, the group learned about the history of the region and the development of the St. Hjøllund Estate. Cultivation of the heath began in the 1860s with large-scale afforestation using a range of conifer species, including Pinus mugo. The forest is now transitioning from its 2nd to 3rd rotation with the dominant species including Norway spruce, Sitka spruce, silver fir, grand fir, and others.

The focus of the visit was the transformation of monocultures of Norway spruce and Sitka spruce to a “3rd generation” forest-structure with a mixture of several tree species (mostly conifers). Both natural regeneration and under-planting are being used to secure the future mixed-species forest. The long-term objective is to continue the transformation process primarily based on self-rejuvenation.

The dominant silvicultural systems are shelterwoods, both in large- and small-scale patches, with examples of uniform, group and irregular shelterwood. This is leading to a woodland that is more structurally-diverse than before, and allowing for the inclusion of deadwood, snags and coarse woody debris. Creating appropriate light and environmental conditions are critical for the regeneration of species with different shade tolerance requirements, and the forestry team have to consider the balance between natural regeneration and planting at this stage in the forest’s development. As elsewhere, red deer are a major concern and their management is critical to the success of stand transformation.

The forest is in the ownership of the LEGO company. The forest area extends over 1,400 ha and over 90% is conifer of plantation origin. In addition to transformation of the forest estate, the owners are also committed to afforestation of an additional 10,000 ha in Denmark over the next 10 years. This programme of forest management and expansion is strongly linked to the LEGO company’s environmental commitments and ethics.

Gallery: St. Hjøllund Plantage

Day 2. Salten Langsø Skov, Addit, Brædstrup, Central Jutland

Hosts: Niels Peter Dalsgaard Jensen and Jan Klinkby Østergaard.

Salten Langsø Skov A/S (SLS A/S) is a forest management company that is collectively owned by 74 woodland owners and Christmas tree producers. Established in 2006, SLS provides a full range of forest management services, including production of decorative greenery and Christmas trees. Other functions include hiring hunting in individual forests and managing 25 leases in the surrounding municipalities of Ry, Them and Brædstrup.

The forest visited on this study trip comprised a 600 ha block of woodland that has 10 indivudal or corporate owners. Taken as a single entity, the forest encompasses a diverse range of species, age-classes and site conditions. The current management policy is to transform most of the area to continuous cover forestry, with the long-term goal of maintaining high quality timber production, enhancing wildlife habitat and delivering a range of other ecosystem services.

Gallery: Salten Langsø Skov

Day 3. Kogleskoven Forest, Rye Sønderskov, Central Jutland

Host: Niels Peter Dalsgaard Jensen

Kogleskoven is a small private woodland with an area of approximately 10 ha. This site visit aimed to demonstrate that it is possible to transform a relatively small woodland, not just large, extensive areas of forest. Kogleskoven is predominantly composed of spruce, grand fir and larch plantations, with a small amount of European silver fir and native broadleaves. The long-term objectives are to retain the productive potential of the woodland, promote habitat and biodiversity opportunities, and increase forest resilience by working with a more diverse range of species and stand structures. The owner is an active member of Pro SIlva Danmark and has adopted closer-to-nature forest management principles.

The woodland has been under transformation to continuous cover forestry for 15 years (since 2008). Small gaps have been created during thinning interventions. Natural regeneration and under-planting are being used for stand renewal and to promote forest resilience. Oak, birch, Norway spruce and grand fir are naturally-regenerating. A small component of eastern white pine (Weymouth pine) is also present. Species enrichment includes Douglas fir, western red cedar, western hemlock, lodgepole pine and small group planting of sycamore and beech.

Many habitat features are now being incorporated into the planning and silviculture, including the retention of snags, coarse woody debris, and areas of ground cover for birds and mammals. Cavities are present in some of the older trees, serving as nesting sites for woodpeckers. Deer fencing is being used to protect some of the more valuable areas where underplanting is taking place and smaller exclosures have been placed as a temporary measure to protect patches of natural regeneration. Deer control and management is necessary to reduce browsing damage and for the over-all health and vitality of the forest.

Gallery: Kogleskoven Forest

Conclusions

The excursion provided an opportunity to learn about forests that had a similar plantation history to those in Ireland and the UK, especially the use of Sitka spruce in some of the stands that were visited. Soil and site conditions were perhaps the most important points of difference. Most of the woodlands visited were on former heathlands with mostly podzolic and brown earth soils, as opposed to gleys that are more common in Irish and British spruce forests. Free draining sites allowed for good rooting and tree stability, without the need for drainage and intensive site preparation. The relatively low nutrient status of many sites meant there was generally less competitive vegetation for tree regeneration. Light scarification (screefing) was a common practice to expose mineral soil and create suitable microsites for planting or seed germination. Some of the key learning points were as follows:

• The importance of a close working relationship between forestry professionals and woodland owners in sharing a vision and implementing strategies for stand transformation.
• The value of thinning to promote structural development of forest stands and “individual tree stability” versus “social stability”.
• The use of both shelterwood and selection silvicultural systems to develop an irregular forest structure and facilitate natural regeneration of tree species with diverse ecological requirements. There was recognition that transformation is a long-term endeavour and that attainment of a fully irregular forest structure may take several generations.
• The wide interest in promoting resilience by under-planting a mix of tree species, both conifers and broadleaves, within stands under transformation and to enrich natural regeneration. A long-term objective is a more structurally-diverse and species-rich forest that will generate more options for forest managers in the future.
• The advantage of continuous timber production from the forests, and the capacity to respond to short-term and specific market requirements. This generates a positive cash-flow for forest owners and supports ongoing management activities. The economic performance of each forest supports other non-timber activities and ecosystem services, especially increased potential for wildlife habitat.
• Wind damage can be incorporated within CCF management. Wind is an important natural disturbance in Denmark. There was evidence at each forest visited of damage at a local scale in the form of wind-snap and windblow. Wind damage in most cases has created small canopy gaps for forest regeneration, increased the amount of coarse woody debris and produced snag trees for birds and wildlife.
• The need for continuing deer control and management to reduce the browse pressure on planted seedlings and natural regeneration. Cultivating strong working partnerships between foresters and hunters is essential for achieving long-term objectives at the landscape scale.
• The value of an adaptive management approach where there is continuous development of silvicultural practices in response to close monitoring of forest management outcomes, growth and development, and forest health.
• The potential of closer-to-nature/continuous cover forestry across a range of scales, from small private woodlots to large forest estates.

Acknowledgements

Thanks to Pro Silva Ireland for arranging this fascinating study tour. In particular, I would like to acknowledge the work of Olive Leavy (Administrator), Manus Crowley (Chairperson) and Liam Byrne (past-Chairperson) of Pro Silva Ireland for making all the travel and logistic arrangements. I would also like to thank our wonderful hosts Poul-Arne Madden, Søren Strunge, Niels Peter Dalsgaard Jensen (Chair, Pro Silva Danmark) and Jan Klinkby Østergaard (International Representative, Pro Silva Danmark) for there generous welcome, sharing their expert knowledge and arranging the individual site visits. Finally, my gratitude to all members of Pro Silva Ireland who took part in this excursion, which was memorable for the rich learning, collective insights and enjoyable social time.

Further Information

• Pro Silva Danmark – www.prosilva.dk
• Pro Silva Ireland – www.prosilvaireland.com
• Pro Silva – www.prosilva.org
• Salten Langsø Skovadministration A/S (SLS A/S) – www.slsas.dk
• Ministry of Environment of Denmark – www.eng.mst.dk/industry/forestry
• European Forest Institute | Implementing Closer-to-Nature Forest Management – www.efi.int/publications-bank/closer-nature-forest-management
• Silviculture Research International | Continuous Cover Forestry – www.silviculture.org.uk/continuous-cover-forestry

Additional Reading

• Hoskins, S. 2023. Strong roots in sandy soils: Pro Silva Ireland Study Tour to Denmark 2023. Pro Silva Ireland [Online]. Uploaded: 4 December 2023. URL: https://prosilvaireland.com/study-tour-denmark-2023

Download: Pro Silva Ireland Visit to Central Jutland, Excursion Programme

Image Note: Images on this webpage are free to use for educational purposes. Please inform me of image use via my contact page here. It is also possible to request hi-res copies of images for publication purposes. Any material used should include the following credit: © 2023 Edward R. Wilson/Silviculture Research International.

Citation

Wilson, E. R. 2023. Continuous cover forestry in central Jutland, Denmark. Report on the Pro Silva Ireland Excursion, 12-15 October 2023. Forest Report. SRI-2023-FR01. Silviculture Research International. Published: 05 Nov 2023. URL: http://silviculture.org.uk/continuous-cover-forestry-ccf-in-central-jutland-denmark

Date uploaded: 5 Nov 2023

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