C. SIBLEY ELLIOT1
1 On loan to FAO as Technical Assistance Officer.
Assistant Chief, Division of Forest Products, Commonwealth Scientific and Industrial Research Organization, Australia
EUCALYPTS were introduced into Argentina a little more than 100 years ago, and the experiment was so successful that the practice of planting them to provide shelter on the windswept plains of the Pampa became widespread. Today, these otherwise almost treeless plains are dotted with clumps and belts of eucalypts, some of them up to 80 years old, with trees up to about 50 meters high and of butt diameter up to about 1 meter. The principal species in these shelterbelts are Eucalyptus globulus, E. viminalis and E. rostrata (camaldulensis).
Some 10 or 11 years ago recognition of the possibility of eucalypts playing an important part in meeting Argentina's shortage of home-grown timber led to the beginning of extensive planting of the above and other species of eucalypts in widely different parts of the country. In some instances, these plantations have been and are being established by government bodies such as the railways administration and provincial forestry administrations. In many others, they represent private investment ranging from substantial progressive annual plantings by estancia owners to small scale plantings by individuals who have acquired land specially for the purpose. In other cases, forestry companies have been formed and through these many people of limited means have invested their savings in eucalypts.
As would be expected, there have been some failures in experimental plantings under varied conditions of soil and climate, but these have been much more than balanced by the phenomenal growth obtained when species suited to a particular locality have been planted. Those who have invested their money in eucalypts see in this rapid growth a promise of the early returns that every investor wants. Most of them are thinking only in terms of small round posts and poles, for which there is a very big demand in Argentina and for which small to relatively small trees can be used provided satisfactory preservative practice is adopted. Important as is the building up of the country's supply of home grown posts and poles, it is not necessarily the summit of the contribution that locally grown eucalypts can make towards meeting Argentina's timber needs, and the national and provincial forestry administrations have had in mind a much wider utilization.
The suitability of many eucalypts for a wide range of high quality uses requiring sawn timber has been established in Australia. So also has the high degree of resistance to decay of some species. Nevertheless, officers of the abovementioned administrations have been concerned as to whether the rapid growth of the trees in Argentina would result in sufficient changes in the properties of the timbers to reduce their usefulness. As long ago as April 1957, Jose C. Tinto (Officer-in-Charge, Department of Dendrology, National Administration of Forests, Argentina), writing in El Forestal, recorded that eucalypts were being used in Argentina for posts and fence strainers, parquet flooring, fruit cases and furniture, as well as for veneer, hardboard and paper pulp. Apart from parquet flooring, however, use in the form of sawn timber was and still is limited to isolated instances. Moreover, it was not known whether or not the difficulties being encountered in the conversion of the timber were of the same order as those that had been experienced in Australia.
Because of this, the Government of Argentina requested, under the Expanded Technical Assistance Program, the services of someone familiar with the utilization and treatment of eucalypt timbers. The task was to assess the usefulness of the timber that would soon be available from plantations throughout the country, and to advise on its sawing, preservative treatment and seasoning. The questions of paper making and manufacture of hardboard, veneer and plywood were not included. It was the privilege of the writer to spend almost three months (August-October, 1958) in Argentina on this assignment, working in close collaboration with officers of the National Administration of Forests.
On the advice of that administration, work and observations were concentrated in the Greater Buenos Aires area and in the Provinces of Buenos Aires, Mendoza and Entre Rios. This covered the major activities in the preservative treatment of eucalypt poles and posts and the conversion of eucalypt logs to sawn timber. It also covered, insofar as E. globulus, E. viminalis and E. rostrata were concerned, trees ranging from young plantation trees to relatively old estancia shelterbelt trees comparable in size and form with eucalypts commonly sawn in Australia. Observations on the only other species studied, E. saligna, were more limited and did not include trees more than 20 years of age.
Observation of the general properties of the timber obtained from the older trees provided a valuable basis on which to assess the usefulness of the timber that will become available from the many young plantations now established if the trees are allowed to grow beyond pole size.
FIGURE 3. - Truck load of typical E. globulus logs from an 80-year-old, wide shelter belt. Mar del Plata. Province of Buenos Aires.
There seems to be no doubt that the timber of eucalypts grown in Argentina is somewhat less dense than that of the same species grown in Australia, and the red-colored timbers tend to be somewhat lighter in shade. The difference in density is not as great as was expected, however. Values obtained by the National Administration of Forests show the average basic density of E. globulus, for example, to fall just above the lower limit of the range of that species in Australia. To supplement such work as has been done there is need for a systematic study of the physical and mechanical properties of all the eucalypts being grown in the country, material from as wide an age range as possible being included in the investigation.
Width of sapwood
With a few exceptions, the thickness of sapwood in young, quickly grown trees was not as great as was expected. However, exceptionally wide sapwood was sometimes observed in logs as much as 80 centimeters in diameter, and it may be necessary to include sapwood in timber sawn from such logs and from small diameter logs. As the Lyctus borer is prevalent in Argentina, it will probably be necessary to treat the timber of Lyctus susceptible species if much sapwood is included.
Growth stresses and "spring"
As in Australia, small logs were found to "spring" considerably when sawn longitudinally, because of the presence of growth stresses. It was possible to demonstrate, however, that, by adopting a suitable breaking down pattern, "spring" could be reduced to a minimum. Again as in Australia, larger logs did not give trouble in this way.
In only a small proportion of the many logs inspected were the growth stresses sufficient to cause popping of the ends as soon as the trees were felled or the logs cross-sawn. The frequency was of much the same order as in Australia.
Checking and end-splitting due to drying
End checking and splitting of the ends of logs while waiting to be sawn, and of posts and poles while being dried prior to preservative treatment, also appeared to be of much the same order as in Australia in trees of comparable size, and less serious than it is reported to be in South Africa. These observations were made in late winter and spring, and more trouble would be expected (and was in fact reported) in logs cut in the summer.
Wastage through end checking and splitting could be reduced by adopting the following established practices:
(a) applying a suitable end-coating to the butts of trees as soon as they are felled, and to fresh ends of logs as soon as they are cross-sawn;
(b) sawing logs as soon as practicable after felling;
(c) leaving logs in as long lengths as practicable until they are sawn.
Most eucalypts have a strong tendency to check on the wide faces of tangentially sawn boards and planks, and the behavior of the Argentine-grown eucalypts was found to be no worse in this regard than that of the same species in Australia. Because of this tendency, quartersawing of eucalypts is always recommended, and it was being practiced reasonably well in Argentina.
Collapse was observed commonly in E. globulus and was of about the same severity as is usual in Australia. Experiments with a few specimens taken at random showed that, in most cases, good recovery could be obtained with the simple standard reconditioning treatment, which should undoubtedly be adopted. Apart from the fact that it gives fuller sized boards, it results in less movement of the finished board with change in atmospheric conditions. Specimens that did not respond to this treatment were found to contain tension wood, which appeared to be present in a good many logs of this species. Little obvious collapse was observed in E. rostrata, but it is a feature of this timber in Australia that sufficient collapse to justify reconditioning can be present without being noticeable, and it may be found that in Argentina, also, its treatment would result in fuller sized boards.
Severe sloping grain in the vicinity of branches was common especially in E. globulus and E. rostrata, and gave rise to serious localized distortion, especially when shrinkage was increased by collapse. This problem should be less when normal plantations, yielding trees with fewer branches, are drawn on.
As in Australia, an appreciable proportion of trees of E. rostrata had somewhat crooked boles, even when grown in plantations. The accompanying sloping grain is responsible for a tendency to warp, as is spiral grain, which was found to be very common in E. globulus.
There was found to be a need for wider application of special stacking precautions to reduce warping of boards containing sloping or spiral grain.
Unfortunately, because spiral grain is so common in E. globulus and causes poles to" wind" sufficiently to break telephone wires, the national telecommunications authority will no longer accept poles of this species.
All the timber examined was much freer from kino veins and pockets than is the average sample of eucalypt timber in Australia.
The judgment reached was that the timber of the four species observed, even when sawn from comparatively young trees, had suitable properties for a wide range of uses such as furniture, joinery, flooring, house construction and case making. Little was actually being used for any of these purposes except flooring, but the few craftsmen who had made furniture from E. rostrata and E. saligna in various parts of the country were enthusiastic about the good hand working properties of these timbers.
A considerable quantity of high grade parquetry flooring was already being made. Because of the prevailing demand for "blonde" floorings, E. globulus and E. viminalis were found to be more popular than the other species which would make equally good flooring. There was a common wastage of 30 percent to 40 percent of the dried narrow boards from which parquet blocks were cut. The two main causes were local distortion due to severe sloping grain in the vicinity of branches, and collapse, the latter increasing the severity of the former. The usual practice was to dock out the warped and undersized portions, and discard them. There is no doubt that adoption of the reconditioning treatment would reduce the wastage appreciably and a further saving could probably be obtained by using any docked portions for other purposes in which short lengths could be utilized. The parquet blocks are cut from short (approximately 2 meters) narrow boards, and in one plant any of these that contained warped areas were removed from the parquetry stock and used for making cases for machinery, etc.
Excellent, though isolated, examples of the use of these four species for the other purposes listed were seen, and there is no doubt that some of the other species being grown could be put to similar uses.
One small timber house built completely of E. rostrata had been built for approximately one year and no fault of any kind was evident. Provided the joinery, flooring, lining and sheathing were properly seasoned, eucalypt timbers could be used with satisfaction for small timber prefabricated houses such as those being erected in some parts of the country. One very good example of the use of E. globulus for roof framing timbers was seen in a house built in 1943.
FIGURE 4. - Typical saw and tog carriage used for eucalypt logs.
The builder of the E. rostrata house is a manufacturer of furniture, doors, etc., and this species comprises between 70 percent and 80 percent of the timber he uses.
Attempts to make citrus cases from green E. saligna cut from trees about 5 years old had not been successful owing to collapse and splitting at the nails. On the other hand, excellent sample export citrus cases had been made from air-dried E. saligna cut from a tree 20 years old, with a diameter of about 50 centimeters. Also, a very high quality office desk seen had been made from air-dried E. saligna said to have been cut from a tree 10 years old and about 20 to 30 centimeters in diameter.
Poles and posts
It was found that naturally durable species of eucalypts such as E. sideroxylon were being planted in the hope that, because they were used untreated as poles in Australia, they could also be used untreated in Argentina.
There is strong evidence that the resistance to decay shown by the durable eucalypts increases with the age of the tree and it is not likely that the quickly grown trees of those species which have a reputation for natural durability in Australia will have attained full durability by the time they reach pole size in Argentina. Moreover, the central core of eucalypts is notably nonresistant to fungal attack and, in the relatively small diameter poles common in Argentina, the central core of 5 centimeters to 7 centimeters, plus the sapwood, constitutes a big proportion of the pole. This means that, even if the rest of the heartwood has attained good durability, it makes up a comparatively thin annulus enclosing and surrounded by nondurable wood.
FIGURE 5. - E. rostrata log approximately 80 centimeters diameter, showing exceptionally wide sapwood. Butt log of tree was 1.20 meters in diameter and tree between 40 and 60 years old. San Pedro, Province of Buenos Aires.
Because of this, it is considered that preservative treatment of poles and round fence posts is probably essential for all eucalypts in Argentina. However, it was recommended that poles of species such as E. sideroxylon should be tested for natural durability by erecting them in nonservice lines.
As the high pressure (approximately 70 atmospheres) preservative treatment necessary for impregnating the heartwood of eucalypts would be uneconomic for fence posts, and as the heartwood of relatively small trees of any of the eucalypts is not likely to be decay resistant, split fence posts obtained from relatively small trees could not be expected to be successful. The treatment of the sapwood of poles and round fence posts as practiced in Australia, however, will give good serviceable life, and does not require abnormally high pressures. Actually, the pressure used for poles in Australia is about 13 atmospheres and for treating eucalypt poles it may be desirable for Argentina to change from the pressure of about 7 or 8 atmospheres being used for poles of other timbers. For small round fence posts lower pressure plants, such as those developed in Australia, and sap replacement treatment using suitable waterborne preservatives that fix in the timber have been recommended.
Perhaps Argentina's greatest need in the way of durable sawn timbers is for railway sleepers. Although it is not one of the most durable eucalypts, the railways administration had hopes that this need might be met, at least to some extent, by E. globulus, which was available in reasonable quantity in shelterbelts 40 years or more old in the central latitudes of the country, where the main sleeper requirements are, and which are remote from the northern native timbers.
A large trial parcel of E. globulus sleepers had been cut from trees about 40 years old, and inspection showed that many of these contained a large proportion of nonresistant core and/or sapwood and had bad ring shakes and other defects. It was obvious that bigger trees would have to be cut to provide sound sleepers. Even then, on the basis of Australian experience, the species could not be expected to yield really first class sleepers without preservative treatment at the high pressure to which reference has already been made. In view of the reported availability of adequate though distant supplies of white quebracho, an easily treated timber, it was considered that installation of high pressure plant to treat E. globulus would not be justified.
FIGURE 6. - Precut timber house built entirely of E. rostrata. San Pedro, Province of Buenos Aires.
This does not rule out the possibility of E. globulus of adequate age being a valuable source of durable timber for somewhat less exacting uses, or of other naturally more durable eucalypts which are growing well in parts of the country eventually becoming an important source of durable timber for railway sleepers and other uses. The need is to determine at which age the various species will reach maximum durability.
In this respect, it was observed that E. globulus poles not in contact with the ground and probably cut from trees about 10 to 15 years of age, had decayed completely in 8 years, whereas under similar climatic conditions a 60- to 70-year-old tree of the same species had been on the ground for about the same time and was still perfectly sound.
There is a good variety of naturally durable eucalypts up to 60 or 70 years of age available in sufficient quantity for experimental purposes, and it is hoped that a systematic investigation of the decay resistance of these species at various ages will be commenced in the near future. Specimens from mature trees grown in Australia have been offered for comparison. Laboratory soil jar tests could produce, in a relatively short time, information of great value in deciding the minimum age at which to harvest plantations of the species being grown to produce durable timbers.
It is probable that the main problems to be faced in developing the wide and wiser use of eucalypt timbers in Argentina is to encourage growers and manufacturers and the public to appreciate the value of some species for high quality use and for a variety of other uses as widely different as cases and general building timbers. Growers will have to be convinced that the increased value of the timber will justify allowing some trees to grow to a greater age than that at which they now anticipate cutting them.
In several plantations there was evidence that there would often be an advantage in early thinning. It appeared that not only do many suppressed or subdominant trees virtually stop growing but that, when not removed, they reduce the rate of growth of other trees. Thorough investigation of this possibility and of means of making profitable use of thinnings is very desirable. It appeared that there were rather unique opportunities for utilizing thinnings in Argentina, and it is believed that investigation would prove to growers that, in some cases at least, it would pay them not to look to poles as the ultimate product of their plantations. Poles might rather come to be regarded as a third thinning, following previous thinnings for minor uses and for fence posts, with sawn timber as the ultimate objective.