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Research impact highlights - Forestry

Making wood work

Niall Farrelly, Luka Kranjz and Annette Hart

Timber, and its increasing use as a construction material, plays a key role in increasing the competitiveness of the Irish forestry sector; and the long-term storage of carbon in harvested wood products can assist climate change action goals. New research conducted by Teagasc and National University of Ireland, Galway has established that increasing the rotation age of Irish-grown Sitka spruce, Norway spruce and Douglas fir to 50 years can increase the strength grade of Irish-grown timber to higher strength classes commonly associated with slower grown European timber.

The research found that thinning systems that favour the removal of larger and branchy trees should be favoured, as knottiness and excessive radial growth are the main causes of loss of structural strength in Irish-grown timber. Thinning practices that favour the retention of high quality co-dominant trees grown on longer rotations have more mature wood with thinner rings, both of which improve the structural properties of the timber.

The outcomes of this research have illustrated that, if managed properly, Irish-grown softwood has significant potential for increased usage in higher-end structural applications, offsetting carbon intensive traditional building materials. It has also contributed to the inclusion of Irish-grown Douglas fir for the first time, which can now be graded and used for structural use.

Correspondence: niall.farrelly@teagasc.ie
Other contributors: Technical staff at Teagasc and National University of Ireland, Galway, Coillte Teo, Murray Timber Group, Ballygar, Co. Galway and Microtec.
Funding: Teagasc Walsh Scholarship Programme; Teagasc grant-in-aid; Department of Agriculture, Food and the Marine; Council for Forest Research and Development (COFORD).