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Tŷ Rhŷg (Wales)

This forest is situated in the Preseli Mountains near Rosebush, Pembrokeshire. It was originally planted with mainly Sitka spruce by the Forestry Commission between 1956 and 1961, and acquired by the present private owners in 2004. The original plantation is now managed according to CCF principles. The forest was awarded a RFS Excellence in Silviculture Gold Award in 2015. Elevation is from 300 metres with soil ranging from brown earth on the lower slopes to ironpan soils on the upper slopes.

When first purchased, the average standing timber volume was assessed as approximately 300m³/ha having been thinned regularly by the previous owners. Tŷ Rhŷg compartment 2001:

Plot 

Gross area (ha) Net area (ha) Volume (m3/ha)Total volume (m3)Diameter at breast height (DBH) Average tree volume (m3)
7

14.00 

11.90  312  3713  21  0.3
8

16.50 

14.03  296  4151  18  0.18
Total 30.50  25.93   7864    

Photo evidence from that time shows that the ground flora was largely absent apart from a few scattered soft ferns, and that the stand biodiversity was poor. In addition, some windthrow was present and it was questioned whether it would be prudent to clearfell. Had they clearfelled, the present stand would be 17 years old. Instead, they opted for a CCF management approach to provide regular income and to enhance forest biodiversity.

The main management objectives are to enhance and maintain the capital value of the forest and to gain a regular income from timber production. These objectives are achieved by carrying out regular and frequent selective felling, every four years. This is applied according to the principles of strict selection rules.

Tree removal is limited to approximately 20% of basal area to maintain optimum standing timber and stability. Tree selection is carried out by Huw Denman, Welsh forest manager specialising in CCF, and is based on the premise of removing the worst of the biggest trees on each occasion on a 'target diameter' basis. The target diameter is 45-50cm diameter at breast height (DBH), the maximum diameter required by sawmills.
Removal of large trees ensures that harvesting costs are minimised and that the sales price is maximised, giving a good profit margin following each 4-year felling intervention.

The canopy gaps created by regular selective felling allow natural regeneration to occur, minimising the expenditure that might be required for replanting. However, some underplanting of shade-tolerant species such as Douglas fir, western red cedar, Norway spruce, and some broadleaves (e.g. small leaved lime and beech) was carried out to diversify the forest.

The forest has been thinned four times since 2001, each time yielding between 50-70 m³/ha. The timber was sold on a standing sale basis. The percentage of sawlog (the high value part of each timber sale) has increased with each successive intervention. Windthrow clearance took place in 2016.

Summary of production 2017 Tŷ Rhŷg:

Year Yield (m3Volume harvested (t/ha) Log %
2002

1620 

53.11  42
2007

1576 

51.67  67
2011

1998

65.51  93
2016

200 

6.56  75
2017

2155

70.66  85.4
Total

7549 

   

The average tree size removed during the last intervention in 2017 was 1.5m³ with an average DBH of 40-50cm. This equates to approximately 46 trees felled per hectare.

To date, a conventional, purpose-built harvester and forwarder have been used. Racks are currently 18m apart. It’s planned to extend the distance between the racks in future by combining the harvester and forwarder system with manual felling. By felling trees manually towards the rack, the harvester can reach in, "grab" and process the manually felled trees.

The standing volume in 2017 was 300-350 m³/ha of which 70-80% was sawlog. Stocking density was 350 trees per hectare. The next intervention is planned for 2020, by which time standing volume per hectare and average volume per tree will have increased. It is estimated that it would take 40 years before all the current trees are removed assuming the harvesting continues to remove 45 trees per hectare per intervention.

Bird monitoring is an important part of management at Tŷ Rhŷg using mist netting, bird ringing and a nest box scheme. Bird species usually associated with native oak woodlands are known to nest in the continuous cover Sitka spruce plantation in Tŷ Rhŷg, including wood warblers, redstarts and flycatchers. Monitoring of moths started in 2017 and almost 200 moth species have been recorded to date.