Ceisteanna—Questions. Oral Answers (resumed). - Increase in Tree Planting Distances.

Wednesday, 5 December 1956

Dáil Éireann Debate
Vol. 160 No. 13

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Mr. Moher: Information on John W. Moher  Zoom on John W. Moher  asked the Minister for Lands if he will state (a) why the current tree planting distance has been increased from 5' × 5' to 6' × 6', (b) the technical reasons for such change, (c) the number and location of the experiments, and the soil types on which such experiments were carried out, (d) whether the quality of the ground to be planted is similar to that planted heretofore, and (e) the reduction in the number of working days in the current financial year caused by the difference between a lay-out per acre of 1,750 plants and 1,250 plants.

Mr. Blowick: Information on Joseph Blowick  Zoom on Joseph Blowick  The Deputy appears to be under a misapprehension. There has in fact been no general increase in planting distances but the practice of using 6' x 6' spacing for certain species when planted pure has been extended. The only important species in question are Sitka Spruce, Douglas Fir, and Japanese Larch but 6' spacings are [1863] used also for some numerically less significant species, e.g. Silver Fir, Abies Grandis and Ash. Six foot spacing cannot be termed revolutionary from a silvicultural point of view. In forestry wide spacing is usually considered to mean spacings in the region of 10' x 10' such as are widely used in South Africa, New Zealand and Australia. The limited silvicultural difference between 6' and 5' spacing can best be illustrated by the fact that on the 6' spacing the side branches have only to spread a further 6” (from 2½' to 3') before closing of canopy is effected. In terms of growth, other things being equal, this would probably mean a delay in closing the canopy of from one to two years.

The species for which the wider spacing has been specified are the Pacific and Japanese conifers which are of more rapid growth rate both in height and lateral spread than the European conifers. The only exceptions are Pinus Contorta and Abies Mobilis. In the case of the Pinus Contorta the closer 5' spacing is used on account of the mutual shelter which is thus provided on the exposed sites where this species is normally used, and also to provide a wider field of selection of final crop stems in a species which is prone to crooked growth. In the case of Abies Nobilis growth in the early years is very slow and the closer spacing hastens closing of canopy. Mutual shelter is also important in this species as it is largely used on exposed sites.

Of the plantings for which 6' spacing is used Sitka Spruce accounts for some 85 per cent. of the total. It has been possible in recent years to prepare the planting site more intensively for this species by ploughing and to hasten initial growth on poorer sites by the application of phosphates. Close canopy stage can now be reached in the same time at 6' spacing as was possible in the past with less intensive site preparation at 5' spacing.

In the case of Japanese Larch planted on suitable soils, early growth is rapid and competing weed growth is soon controlled.

[1864] General Irish experience of Douglas Fir has been that it responds well to wide planting on suitable sites and satisfactory quality can be obtained from plantations established at 6' x 6'. The same applies to Silver Fir and Abies Grandis.

The planting of Ash at wider spacing is being carried out with a view to promoting rapid girth growth for the purpose of producing timber of sports quality on a short rotation.

The remaining species planted at 6' x 6' spacings are used only to a limited extent and largely as edgings and screens where special considerations apply.

It should be emphasised that the total production in cubic feet per acre over the rotation is not affected by the adoption of 5' or 6' spacings.

One of the chief arguments in favour of close spacing is the early closing of the canopy and elimination of weed growth but these beneficial effects are now obtained by the more intensive site preparation generally adopted, especially with the principal species-Sitka Spruce.

Closer spacing is also conducive to the production of cleaner timber but this is not affected in any significant way by a difference of one foot in the planting spacing. On the other hand the wider spacing allows of the first thinnings being deferred by about two years, thus giving produce of a larger size which is more economical to handle. Very small first thinnings are more difficult to dispose of since some of them are under minimum pulp wood size and they cost more to handle per cubic foot. Thinning must be carried out whether the material is saleable or not. With the wider spacing the produce will be of larger dimension both in girth and length and thus will afford a better monetary return.

A wider selection for the final crop is obtained by closer spacing but sufficient stems of reasonable form can be obtained from the 6' by 6' planting in the case of the species concerned.

My Department's technical experts are still in the process of working out the best silvicultural treatment for [1865] these exotic species of which we have very limited experience of pure crops over a full rotation but the use of 6' planting for these species under suitable conditions cannot be described as experimental.

Wider spacing enables a saving to be made in the cost of establishing plantations under the heads of plants and planting, estimated in the current year at £25,000.

Mr. MacEntee: Information on Seán MacEntee  Zoom on Seán MacEntee  Arising out of the Minister's prolonged reply, is it not a fact that the principal reason——

Mr. Dillon: Information on James Matthew Dillon  Zoom on James Matthew Dillon  Deputy Moher is on his feet behind the Deputy.

Mr. Moher: Information on John W. Moher  Zoom on John W. Moher  The Minister's reply sounds like a defensive statement.

Mr. Blowick: Information on Joseph Blowick  Zoom on Joseph Blowick  A what? By the time the Deputy and the person who prompted him to put down the question have digested the reply, they might think differently about it.

Mr. Dillon: Information on James Matthew Dillon  Zoom on James Matthew Dillon  Hear, hear!

Mr. MacEntee: Information on Seán MacEntee  Zoom on Seán MacEntee  Is it not a fact that the principal reason for adopting the wider spacing for the species of trees mentioned is that it will enable the Minister to brag that he has planted a 40 per cent. greater acreage than last year?

Mr. Blowick: Information on Joseph Blowick  Zoom on Joseph Blowick  I would endeavour to give some kind of a reply to that supplementary question if I thought the Deputy knew anything about forestry, but he does not.

Major de Valera:  That is not forestry. It is a simple question.


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