Much to consider in planting a forest

About 90% of the original trees in a forestry plantation are removed as thinnings over the rotation — or about 50% of the volume.

If you are considering a long-term investment like forestry, it is worth considering every angle.

Don’t base the decision to plant solely on the amount of premium payments available for a particular species, says Co Cavan Teagasc forestry development officer Kevin O’Connell.

In the current issue of the Today’sFarm Teagasc magazine, Kevin says the potential value of the crop itself is key.

A well- managed sitka spruce crop at yield class 24m“/ha/year could have an annual equivalent value of €566/ha.

Species selection is important; some sites are suitable for growing a good conifer crop and are marginal for broadleaves.

However, there are cases where broadleaves, or slowergrowing conifers, are planted because of the initial higher premium.

Fast forward 15 to 18 years, and the faster- growing conifer is ready for first thinning, and is generating income. The slower conifers/ broadleaves are not.

However, broadleaves have a higher biodiversity value, also worth considering.

Always consult a qualified forester prior to planting.

Familiarise yourself with the needs of the individual tree species, such as their nutrient requirements, their light requirements, their rooting and branching habits and their speed of growth.

Think also about how to manage the trees from the time they are planted until they are felled.

What are the best management techniques to adopt to produce a sustainable crop of timber?

The Forest Service has produced excellent leaflets on the silvicultual characteristics of tree species, which are available to download from www.agriculture.gov.ie/forestservice

Planting density

In general, our forests are plantation forests, comprised mainly of exotic conifer species, the majority of which come from the west coast of north America.

Most broadleaf trees planted are native species like oak, alder and birch (ash can no longer be planted, because of the ash die back disease).

Exotic species like beech and sycamore are also planted. The majority of our forest plantations, broadleaves as well as conifers, are monocultures, comprised of one species.

At establishment, trees are planted at a close spacing, usually 2.0m by 2.0m apart for conifers, to give a stocking of 2,500 trees per hectare.

Broadleaf trees are planted even closer together.

Why plant so many trees? Well, some of these trees will die of natural causes (such as frost damage, poor plant handling, weed competition, suppression, etc), so it is important to have enough trees to reach maturity.

Also, by planting trees close together, their ‘taper’ is reduced, producing a more cylindrical log.

There is more recovery of sawn timber from the logs when they go for processing in the sawmill.

Closer spacing also results in smaller branch size and natural pruning, smaller knots and cleaner timber.

Thinning

Another reason for planting so many trees is that there are more to remove when thinning starts. This is a vital operation. The normal practice is to remove some of the trees (a proportion of the standing volume) at intervals over a period of years.

This provides more growing space, reduces competition and the risk of diseases/ pests, ensures a reasonably equal distribution of final crop trees throughout the area and, importantly gives an intermediate financial return. It is important to carry out thinning at the right time. Delaying the operation can result in windblow.

Plan early for thinning, and have everything in place to start the operation at the appropriate time.

First thinning in conifers takes place a few years after canopy closure, usually when a top height of about 10 metres is reached.

First thinning in broadleaves takes place at a top height of about 12 metres.

About 90% of the trees are removed as thinnings over the rotation, or about 50% of the volume.

So if 2,500 sitka spruce are planted at day one, there will be only about 400 stems per hectare at clearfell, the rest will be removed as thinnings.

First thinnings will not yield a bonanza. If owners can get their infrastructure in place, with roads, loading bays, and turntables, and break even, they are doing very well.

It is in the subsequent thinnings where money can be made, as there is no major expenditure.

Taking the species, access and location of the stand into account, if you are being offered big money for your first thinnings you are strong-ly advised to get an approved forester to carry out thinning control as the thinning operation is taking place. Remember, you are only removing the smaller diameter trees.

Final harvest

How long should the trees be left grow before they are clear felled? Some people are under the impression that trees, particularly conifers, can be felled after 20 years, as soon as the premium payments run out.

This is untrue. Trees are really only in their prime at about year 20, and there is a lot more g rowth needed before they are at a size to make sawlog — from 35 years for fast-growing conifers to over 80 years for most broadleaves. Remember, the big money is in the saw log.

All is not lost, of course, because the trees still need to be thinned, and the thinning will be carried out on a three-to five-year cycle, depending on the species and the growth rates. In each subsequent thinning, larger size trees are removed, resulting in more money for the grower.

The logistics of forest operation like establishment, road construction and harvesting might seem daunting, but they shouldn’t be.

The Teagasc Forestry Development Department provides free, independent and objective advice on all your forestry queries. Our www.teagasc.ie/forestry web-site is full of forestry facts and information.

Why not sign up for our forestry e-news magazine, and get information forwarded to you regularly. There are 26 forest owners group in the country, why not join one and share information and experiences with other owners.


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