Treatments applied in large plots

Clocaenog Continuous Cover Forestry (CCF) Research Area

Each Block has been thinned in 2004, 2009 and 2012 aiming to achieve a residual basal area of 25 m2 ha-1. The criteria to consider for tree removal are:

  • Location of tree (i.e. to achieve stand structure objectives)
  • Stability (preference to remove less stable trees)
  • Presence of the Great spruce bark beetle (Dendroctonous micans)
  • Tree form.

Block 1 – Uniform shelterwood (14.1 ha)

The majority of this area has been thinned using the standard Forest District practice of transformation of Sitka spruce to a simple structure (one or two canopy strata).  The area also contains an unthinned control, which is a 1 ha assessment plot (Labelled “CLG1” in the map of the Clocaenog experimental areas) and a 50 m surround.

An area of Block 1 showing a Sitka spruce overstorey with regenerating Sitka spruce seedlings.

Block 2 – Irregular shelterwood (4.4 ha)

The aim in this area is to produce a more irregular stand structure and heterogeneous regeneration compared with the uniform shelterwood in Blocks 4 and 5.  This is being achieved by:

  • Increasing the size of existing canopy gaps and the producing 1 or 2 new gaps at each thinning
  • Removing trees competing with marked Frame trees (40 ha-1 unevenly distributed)
  • Silvicultural improvement of the matrix.
An area of Block 2 showing a Sitka spruce overstorey with regenerating Sitka spruce seedlings in the understorey.

Block 3 – Group strip shelterwood system (9.7 ha)

This is the most innovative treatment in any of the Blocks and is aiming to produce an irregular stand structure as quickly as possible.  This is being achieved by:

  • Enlarging the eight large canopy gaps in the area, some of which contain regenerated trees from past canopy disturbances
  • Increasing the width of the strip on the north-eastern side of the Block by 25-30 m during each thinning intervention
  • No silvicultural thinning of the matrix other than to clear-up any wind damage.
A Large canopy gap located in Block 3. There is an area of dense Sitka spruce regeneration in the centre of the gap.

Blocks 4 and 5 – Uniform shelterwood (8.0 ha and  5.9 ha respectively)

The aim of these two blocks is to produce a simple CCF structure by judicious thinning of the canopy to aid the growth and development of regeneration. To achieve this the priorities for tree removal are:

  • To ensure the continued stability, growth and development of the seed trees (80 ha-1 evenly distributed)
  • To improve growth and development of selected matrix trees.
An area of Block 5 showing Sitka spruce managed using a uniform shelterwood. An aerial photograph of the experimental area at Clocaenog taken in 2007. There are several prominent group fellings that can be seen.