The forest trees we plant in Ireland

When Growing for the Future – the Strategic Plan for the Development of the Forestry Sector in Ireland was launched in Ireland in 1996, it proposed to change species selection in Ireland from a predominantly monoculture – of Sitka spruce and lodgepole pine – to a more diverse species menu. It stated: “Each grant-aided conifer afforestation project should in future be required to contain a minimum of two species and a maximum planting of 85% of any one species, site and site area permitting.”

The species mix proposed for future annual afforestation programmes was:

This decision was taken at a time when broadleaved afforestation was beginning to increase from an average of 4% of total planting during the 1970s and 1980s (Table 1). Sitka spruce and lodgepole pine dominated afforestation during this period often combining to 85% of annual programmes.

Virtually all planting (new and reforestation) was carried out by the State up until the 1980s. By then, farm planting, was beginning to increase due to EU supports and the marginal land being made available for afforestation was more suitable for high nutrient-demanding broadleaved species than the poor exposed sites planted up to the late 1980s.

Species trends have changed dramatically over the years. High conifer afforestation programmes during the 1940s of Scots pine, larch and Norway spruce were replaced with Sitka spruce and lodgepole pine from the 1950s to the 1980s. Now, lodgepole pine is rarely planted since afforestation ceased in blanket bogs and other low nutrient sites. Japanese larch is no longer planted due to its vulnerability to the disease Phytophthora ramorum. Extra state funding for broadleaves helped to switch the trend away from conifers. From 1997 to 2000, broadleaved afforestation reached 15% to 16% of all planting with further increases up to 2008 when 36% of the afforestation programme comprised broadleaves. The 2008-14 data (Table 2) refer to private afforestation by private forest owners – mainly farmers. Likewise, ash which reached an unprecedented 9% of all afforestation from 2008 to 2012 is no longer planted due to the threat of Chalara fraxinea or ash dieback.

A drop in broadleaved planting to 22% in 2014 can be partially explained by the exclusion of ash from the afforestation programme.

Ash is regarded as a commercial hardwood providing an early return from firewood and hurleys with potential later for furniture. Grown in the right site, no other hardwood comes near in terms of rotation length, yield and market potential. Replacing ash has presented a species selection dilemma for growers and it would seem that it has been replaced not by another hardwood but possibly by Sitka spruce.

However, the 20% target proposed by the 1996 strategic plan, has been exceeded over the past 10 years, averaging 27% of all planting. But farmers and other landowners who are planting some of their holdings can no longer be accused of opting for broadleaves because of attractive grants and premium payments. It is likely that the species selection mix is now influenced by economic considerations with biodiversity and other non-wood benefits maintained as part of sustainable forest management.

Species diversity comparisons

Species composition differs widely throughout Europe with conifers the dominant species in northern countries and broadleaves favoured in the south.

The conifer broadleaf ration in Ireland is approximately 74:26. The species mix comprises 52.4% Sitka spruce, 11% pine, 4.1% Norway spruce, 4.4% larch, and 2.2% other conifers, with 3.2% ash 2.6%, oak, 1.5% beech, 1.5% sycamore, 5.9% birch, 2.4% alder and 8.8% other broadleaves.

In Sweden, the conifer broadleaf ratio is approximately 81:19. According to Skogsstyrelsen, the Swedish Forest Agency, the total standing volume of trees on productive forest land in Sweden in 2011 was just under three billion cubic metres comprising 81% conifers, almost all Scots pine and Norway spruce, with broadleaves dominated by 12 % birch.

Germany has a 60:40 ratio in favour of conifers, while neighbouring Austria has a higher conifer ratio of 75:25 with 60% of forests comprising Norway spruce.

Conifers dominate global forestry, especially in the Boreal forests or Taiga which cover large tracts of land in Norway, Sweden, Finland, Russia and Alaska. Globally, according to an FAO analysis (based on results for 117 countries), coniferous species accounted for 61 % of the growing stock, which the FAO believe is “to be an underestimate of the actual situation”.

The big producing Pacific Northwest states in the US also rely heavily on conifers. For example, 85% of Oregon’s forest are coniferous comprising Douglas fir (35%), Ponderosa pine (16%) and other conifers (35%). The Pacific Northwest area, especially Washington State in the US and British Columbia in Canada, are of special interest to Ireland as many of our exotics were sourced here from the 1830s including Sitka spruce, Douglas fir, lodgepole pine and western red cedar.