Clocaenog Continuous Cover Forestry (CCF) Research Area

Sitka spruce seedlings and saplings growing beneath a canopy of Sitka spruce in the Clocaenog experimental area. A timber stack features in the background.


The main focus of this area is to support the Welsh Government’s ‘Woodlands for Wales’ policy and produce evidence and demonstrate alternative methods of forest management to clearfelling.

The Clocaenog CCF Research Area was established by Bangor University and Forest Research in 2002 and has three main objectives:

  • To test the feasibility of late transformation of Sitka spruce using different silvicultural systems
  • To produce large plots of contrasting stand structures that can be used for other experiments
  • To produce data to support the development of the MOSES-GB model.

Background to the Clocaenog CCF Research Area (PDF-660K)

The following information summarises how each of the above objectives is being achieved and, where possible, shows results of the studies that have been completed or are in progress.

The structure of the area is that it contains five large plots each of which is managed using a different silvicultural system.  Within four of these plots there are smaller plots (labelled ‘CLG’ in the diagram below) that are being used to produce data to support the development of the model MOSES-GB.

Map of the Clocaenog experimental areas

Late transformation of Sitka spruce

The area consists of five large plots, that total an area of 45 ha, in which the overstorey has been thinned in different ways in an attempt to produce structures analogous to different silvicultural systems.  The stands were planted in the early 1950s and therefore constitute ‘late transformation’ to CCF in terms of the guidance given in Mason and Kerr (2004).  This scenario is quite common in Wales and so the area is producing useful information for forest managers.

Detail on the treatments applied in large plots

Two ways in which information from these plots has informed forestry practice are:

  • They are challenging the prediction of the windthrow model ForestGALES
  • They have informed the development of methods of harvesting and extraction in CCF where the aim is to remove trees but not damage the developing understorey (Stokes et al. 2009).

Modelling mixed-aged and mixed species stands

The area contains four permanent sample plots that are producing data to support the development of project on modelling mixed-aged and mixed species stands. These plots are shown as ‘CLG’ in the map above and are valuable as the spatial location of every tree in the plots has been mapped.

Plot CLG 2 showing some mature Sitka spruce that have paint markings on them. There are also many Sitka spruce saplings in the understorey

Other experiments

The area contains three other experimental studies:


Grassi, G. and Giannini, R. (2005). Influence of light and competition on crown and shoot morphological parameters of Norway spruce and silver fir saplings. Annals of Forest Science, 62: 269-274.

Mason, B. and Kerr, G. (2004). Transforming even-aged conifer stands to continuous cover management (PDF-88K).  Forestry Commission Information Note 40. Forestry Commission, Edinburgh.

Page, L. M., Cameron, A. D. and Clarke, G. C. (2001). Influence of overstorey basal area on density and growth of advance regeneration of Sitka spruce in variably thinned stands. Forest Ecology and Management. 151: 25-35.

Pommerening, A. (2006). Evaluating structural indices by reversing forest structural analysis. Forest Ecology and Management, 224: 266–277.

Stokes, V., Kerr, G. and Ireland, D. (2009). Seedling height and the impact of harvesting operations on advance regeneration of conifer species in upland Britain. Forestry, 82:185-198.

Further reading

Davies, O. and Kerr, G. (2011). Costs and Revenues of Transformation to Continuous Cover Forestry (PDF-568K).  Report to the Forestry Commission by Forest Research.  Alice Holt Lodge, Farnham, Surrey, England.

Gardiner, B. Leban, J. M., Auty, D. & Simpson, H. (2011). Models for predicting wood density in British-grown Sitka spruce. Forestry, 84(2):119-132.

Williams, D.T., Straw, N., Jukes, M., Fielding, N. and Price, J. (2011). Influence of forest management on bark-beetle (Scolytidae) populations inhabiting Sitka spruce plantations in Wales, UK.  IUFRO WP.7.03.05 – Ecology and Management of Bark and Wood Boring Insects.  Novel risks with bark and wood boring insects in broadleaved and conifer forests. Sopron, Hungary, 7-9 September 2011.

Williams, D.T., Straw, N., Fielding, N. and Price, J. (2012). Do forest management systems influence the abundance and diversity of the natural enemies associated with the green spruce aphid (Elatobium abietinum) in Sitka spruce plantations in Wales, UK.  Joint IUFRO WP.7.03.10 – Methodology of forest insect and disease survey, and IUFRO WP.7.03.06 – Integrated management of forest defoliating insects, working party meeting, Palanga, Lithuania, 10-14 September 2012.