Silviculture and timber properties - background

 

Production and demand

The production of timber from British conifer forests is due to rise substantially over the next twenty-five years, with annual sawlog output forecast to be double current levels by 2020 (Whiteman, 1996).

Domestic demand for sawn timber is forecast to remain static over this period, so that homegrown production will have to increase market share in the face of strong competition from the imported sector.

The lower value pallet, packaging and fencing markets, which currently absorb more than two-thirds of UK produced sawn timber, are likely to be over-supplied (McIntosh, 1997), with the result that greater penetration of the higher value construction market will be necessary.

In order to achieve the required increase in market share it is essential that sawn timber meets defined structural grading requirements, i.e. at least strength class C16 and preferably C24 or better (CEN, 1995). These issues are particularly pronounced with Sitka spruce which is the major species being grown in upland Britain.

Research

Existing studies of Sitka spruce timber quality have concentrated on experimental plantings established before the major expansion of Sitka spruce forests between 1950-1980. For example, Brazier and Mobbs (1993) have clearly demonstrated that the out-turn of Strength Class 3 (~ C16) Sitka spruce sawn timber is reduced when trees are established at wider initial spacings. Material from more recent plantings has been less studied and may provide different results because of being grown on more exposed sites with better establishment including fertiliser inputs.

There has been little research examining site and nutritional impacts upon timber quality in Sitka spruce.

References

Brazier, J.D. and Mobbs, I.D. (1993). The influence of planting distance on structural wood yields of unthinned Sitka spruce. Forestry 66(4)333-352.

CEN 1995 EN 338 Structural Timber – Strength Classes. EuropeanCommittee for Standardization, Brussels.

McIntosh, R. (1997). Timber quality creates marketing challenge. Forestry& British Timber August 1997, 17-20.

Whiteman, A. (1996). Revised Forecasts of Supply and Demand for Wood in the United Kingdom. Forestry Commission Technical Paper 19, Forestry Commission, Edinburgh.