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Long-term research in uneven-aged silviculture at Glentress Forest, Scotland

Silviculture Matters
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Long-term research in uneven-aged silviculture at Glentress Forest, Scotland

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This poster by Edward Wilson and Philippe Morgan was first presented at the Society of American Foresters National Convention, Silviculture Matters!, North Charleston, South Carolina, 23-27 October 2013.

The poster presents an overview of the Glentress Trial, at Glentress Forest, Scotland. The trial was established by Professor M. L. Anderson in 1952 as a demonstration area for the transformation to an irregular structure of an even-aged, planted forest. The trial area (117 ha) was set out in a large commercial plantation on an exposed, upland site (~300 m); Anderson wanted to determine if uneven-aged silvicultural systems could be adopted in such locations. The dominant species include Sitka spruce, Douglas fir, European larch and Scots pine. The most important silvicultural system that has been applied is group selection, with group sizes varying from 0.1 to 0.2 ha. Groups have been restocked by planting and natural regeneration. Recent surveys of the trial area demonstrate the gradual transformation to an irregular structure after 60 years. The Glentress Trial is recognised as one of the longest-running research sites in British forestry. The trial has been important for both primary research and for developing operational experience in uneven-aged silviculture. Over the decades since its initiation, the objectives of forestry in Britain have evolved and changed. Today the Glentress Trial has a new relevance as we recognise the importance of uneven-aged forests for their ecological resilience and potential to deliver a wide range of ecosystem services.

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Long-term research in uneven-aged silviculture at Glentress Forest, Scotland

  1. 1. Long-term research in uneven-aged silviculture at Glentress Forest, Scotland Silviculture Matters National Convention Society of American Foresters Charleston, South Carolina 23-27 October 2013 Edward Wilson1 and Philippe Morgan2 1990 0.1 1.9 Summary 1990 1.9 0.1 The Glentress Trial was initiated in 1952 to gain experience in transforming plantations to unevenaged, irregular structure forests. It continues today as one the longest-running silviculture research trials in Britain. 1.5 Change in basal area (m3 ha-1) between 1990 and 2008, by species group (Macintosh et al 2013). Site and Silviculture Inventories of the trial area have been undertaken in 1952, 1980, 1990 and 2008 (Wilson et al 1999, Kerr et al 2010). Results demonstrate the gradual transformation to an irregular structure (Figure 4). The dominant species include Sitka spruce, European larch, Scots pine and Douglas fir (Figure 5). The most important silvicultural system that has been applied is group selection, with group sizes varying from 0.1 to 0.2 ha (Figure 6). Groups have been restocked by planting and natural regeneration (Figures 7 and 8). Conclusion Figure 3. Map of the Glentress Trial area. The trial is laid out with six blocks, each approximately 20 ha. This was designed to facilitate a 6-yr management cycle. Table 1. Number of survey plots in each block at the 1990 of time the 2008 inventory. Block areas in ha. 1.9 Block Plots (No.) A 39 17.8 B 32 20.5 C 38 D 30 2.8 Groups of between 0.1 and 0.2 ha have been made; approx. 1 (left) and 20 yrs (right) after harvest. Seedlings % (2008) Spruce Area (ha) 5.7 Figure 6. 0.1 21.0 Larch 14.1 Other Conifers 15.8 20.1 F 31 22.1 Total 210 113.4 1990 750 300 800 1980 200 150 2008 700 Density (N/ha) 1991 600 500 337 400 300 165 159 200 100 0 100 Seedlings 50 0 10 20 30 40 50 60.5 0.8 Figure 7. Species composition (%) of seedlings and saplings from the 2008 Inventory (Macintosh et al 2013). A significant proportion of the seedlings and saplings are broadleaf species, adding to the diversity of the forest. 1952 0 Acknowledgements 5.8 0.4 7.7 350 Figure 4. 12.3 57.5 14.2 40 The trial has been important for primary research (e.g., Kerr and Macintosh 2012), and for gaining operational experience in uneven-aged silviculture. Over the decades since its initiation, the objectives of forestry in Britain have evolved and changed. Today the Glentress Trial has a new relevance as we recognise the importance of uneven-aged forests for their ecological resilience and potential to deliver a range of ecosystem services (Figure 9). Broadleaves 18.7 E Saplings % (2008) 18.3 Pine 60 Diameter Class (cm) Figure 2. Map of Scotland showing location of the four trial areas established in 1952 by Professor M. L. Anderson. 15.5 2.8 Stems/ha Image: © University of Edinburgh Figure 1. Mark Louden Anderson, MC, MA, DSc, FRSE (1895-1961). Professor of Forestry (1951-1961), The University of Edinburgh. Glentress Other Conifers 4.0 14.1 250 Faskally Larch Broadleaves 2.8 The four trial areas were established at Glentress, Faskally, Corrour and Cawdor (Figure 2). Of these, the trial at Glentress has been managed most consistently, and is currently (after over 60 years) the longest running silvicultural trial of its type (Kerr et al 2010). The trial area was set out (with six blocks) in a large commercial plantation on an exposed, upland site (240-550 m) (Figure 3 and Table 1). It is representative of many planted forests in southern Scotland. Corrour Pine 5.7 Figure 5. Cawdor 3.9 Spruce 14.1 Background The Glentress Trial is one of four research forests established in Scotland, in 1952, by Professor Mark L. Anderson, Professor of Forestry at the University of Edinburgh (Figure 1). At that time, the majority of woodlands in Scotland were being managed as evenaged plantations. Prof. Anderson was interested in knowing if it was possible to replicate some of the mixed-species, irregular structure woodlands he had seen in Europe (Anderson 1951, 1955, 1960). His hypothesis was that these would prove to be more sustainable and resilient in the long term, and that greater experience should be gained in a wider range of silvicultural systems that might be applied to upland forest sites in Scotland (Anderson 1953). 5.7 2008 0.3 Stem frequency distribution by size class (dbh) for Block A at the Glentress trial area on three dates: 1952, 1980 and 1991 (Wilson et al 1999). This demonstrates the transformation from a regular, even-aged structure to a more-or-less irregular structure over 40 years. Saplings Figure 8. Seedling and sapling density across the trial area, 1990 and 2008 (Macintosh et al 2013). Deer browse is thought to have a major impact on current sapling density. Figure 9. Glentress trial area (Block E) in 2012. Note the diversity of species and size classes. Also, the mountain bike trail, created as part of the plan for public use and access to the forest. The Glentress Trial area is owned by Forestry Commission Scotland. For many years the trial was managed in agreement with the University of Edinburgh. Research is currently directed and supported in partnership with Forest Research. Literature Cited • Anderson, M. L. 1951. Spaced group planting and irregularity of stand structure. Empire Forestry Review 30: 328-341 • Anderson, M.L. 1953. Plea for the adoption of the standing control or check in woodland management. Scottish Forestry 7: 38-47 • Anderson, M. L. 1955. High elevation experimental area – Glentress Forest. Unpublished Report. Glentress Archive. Forest Research, Alice Holt, Surrey • Anderson, M.L. 1960. Norway spruce-silver fir-beech mixed selection forest. Is it possible to reproduce this in Scotland? Scottish Forestry 14: 87–93 • Kerr, G., and H. Mackintosh. 2012. Long-term survival of saplings during the transformation to continuous cover. Forests 3: 787-798 • Kerr, G., M. Morgan, J. F. Blyth and V. Stokes. 2010. Transformation from even-aged plantations to an irregular forest: the world’s longest running trial area at Glentress, Scotland. Forestry 83: 329-344 • Mackintosh, H., G. Kerr and T. Connolly. 2013. Structural change during transformation in the Glentress Trial – an update. Scottish Forestry 67(3): 14-23 • Wilson, E. R., H. W. McIver and D. C. Malcolm. 1999. Transformation to irregular structure of an upland conifer forest. Forestry Chronicle 75: 407-412 Author Information 1. Edward Wilson Director, Silviculture Research International Penrith, Cumbria, England CA11 7AY email: ted.wilson@silviculture.org.uk 2. Philippe Morgan Vice-President, Association Futaie Irrégulière Plas y Wenallt, Llanafan, Aberystwyth, Wales SY23 4AX email: admin@selectfor.com

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