Research is underway into a new technique which will both increase resilience and improve the quality of Ireland’s sprawling Sitka Spruce forests, which make up over half of this country’s woodland and support some 12,000 jobs.
The five-year Teagasc project is investigating a new way of managing these forests to promote the growth of better quality wood and make the trees more resilient to climate change and the threat posed by the advent of new pests and new diseases.
Native to the West Coast of the US, Sitka spruce was introduced to Ireland in the 19th century and is now the backbone of this country’s modern multi-million euro timber industry.
“At the moment these forests are thriving,” explains Edward Wilson of Teagasc’s Forestry Development Department and the UCD School of Agriculture and Food Science, who is spearheading the TranSSFor project.
“They are highly productive. However, climate change and the threat of new pests and diseases arising from climate change are posing a challenge to Ireland’s sitka spruce forests.
The standard way of managing Sitka spruce plantations is through rotation. This means that 15 years after the forest is planted, trees are 'thinned out' every four or five years. After 30 to 40 years, the entire forest is clear-felled and the whole process recommences on bare ground.
“This is a very efficient way of producing timber,” said Mr Wilson, who added, however, that because this method of managing forests involves the cutting down of the forest while it is still relatively young, it does not deliver the benefits of a mature forest in terms of bio-diversity, contribution to carbon and positive impact on landscape and wildlife.
“You don’t get some of the features you would find in an older or permanent forest because of the way we manage it.”
The focus of his project, he explains is investigating an alternative approach, widely used in Europe, called Continuous Cover Forestry, on two forests in Co Laois and in Co Wicklow: “In other words, this means having a permanent tree canopy; the forest as a whole is never clear-felled.” Instead what happens, he explains, is that after about 15 years, and every three to five years from then on, the trees are 'thinned out' in a different way, one aimed at improving the quality of the timber while at the same time creating “gaps” allowing the forest to regenerate itself.
“In essence, we make small gaps in the canopy which would be no more than the size of one tree or a group of trees.” The forest is continually thinned with the removal of individual or small groups of trees, without being clear-felled.
Read about transforming sitka spruce plantations where the TranSSFor project is comparing conventional thinning in sitka spruce plantations with two alternative thinning regimes in the latest edition of TResearch. #TResearch https://t.co/2FSz5UcvVF pic.twitter.com/rvKkZaa2nm— Teagasc (@teagasc) April 17, 2020
“You will have seedlings regenerating in these gaps, so there is natural regeneration; this management system allows the forest to renew itself and if you leave it long enough you will get other species coming in, birch or oak or other broadleaf trees, so the forest’s ecosystem is diversifying.
"It is this diversity that makes it more resilient because there are new and different generations of trees in the forest.
“This research adds to the options for forest owners, particularly the owners of private wooded areas who want a woodland that is beautiful and has wildlife and this continuous cover forest is very suited to that,” he said, adding that last year the government introduced a special grant for forestry owners interested in this technique which is also included in the latest programme for government.