Extracts from a formal report submitted to the Government of Brazil
by L. J. ROGERS, FAO Technical Assistance Officer
Paraná pine (Araucaria angustifolia) is in the main confined to the southern states of Brazil, the exception being a small area of forest in the State of Missiones, Argentina. It extends over the high plateau country to the west of the Serra do Mar between latitudes 22° S. and 30° S.
The climate ranges from sub-tropical to temperate, although the northern areas, i.e. from 22° S. to 23.5° S., are within the tropics, the altitude at which the tree occurs modifies the climate so that it may be classed as subtropical.
In the northern part of its range this Araucaria does not appear below elevations of 800 meters above sea level but towards the southern limits it is found at lower altitudes, although in no place below 500 meters. It grows on a wide variety of soils derived from granites, basalts, diorites, phyllites, sandstones, schists and shales. The amount of plant food available in the soil plus the ability of the soil to retain moisture appear to be of greater importance than texture or depth.
The species extended originally in an almost unbroken belt from the Serra da Mantiqueira in southern Minas Gerais, southwesterly and southerly through the States of São Paulo, Paraná and Santa Catarina into northern Rio Grande do Sul. Today, remnants only of the original forest are found in southern Minas and in the State of São Paulo; areas of virgin forest exist in western Paraná, Santa Catarina and Rio Grande do Sul, but the area of forest that has been totally devastated is considerable. It is realized that the clearing of forest for agricultural purposes is a feature of the development of many countries, but it does seem that the devastation which has occurred in this part of Brazil cannot be justified by this purpose only. Moreover, the present day cut remains large and the life of the remaining stands at the present rate of felling may optimistically be estimated at only 40 years.
As one travels through the forests of Paraná pine from north to south, the differences in their composition are striking.
In northern Paraná for example, the forest consists of an upper storey of pine, a second storey of rain forest species such as Cedrela, Aspidosperma, Nectandra, Phoeve perosa, etc., and a third storey of fairly dense undergrowth of various woody shrubs, with an almost complete absence of small-diameter pine and pine regeneration. Towards southern Paraná the forest consists in places almost purely of pine of all sizes, with practically complete absence of rain forest species and only light undergrowth. This type of forest is encountered in Santa Catarina, whilst in the higher elevations and higher rainfall areas of Rio Grande do Sul the forest becomes much denser, both pine and rain forest species of large diameter being common, while there is also a good distribution of all diameter classes of pine from regeneration to the biggest sizes.
It seems therefore that the possibility of regenerating the forests in southern Paraná Santa Catarina and Rio Grande do Sul by natural means is worthy of further investigation. Knowledge of the silvicultural requirements of the species is still insufficient to enable prescriptions to be laid down for the treatment of the forests to secure natural regeneration, but the following points have been noted:
1. Araucaria angustifolia is a strong light demander;
2. the rate of growth of shaded seedlings is very slow;
3. most regeneration occurs in groups in openings made by the removal of trees, along roads, or along the edge of the forest, that is, wherever there is ample overhead light;
4. seed is readily eaten by pigs, and large quantities are gathered for food;
5. seed and seedlings are apparently not damaged by grazing cattle;
6. seedlings of 1.5 meters or more in height are severely damaged, and in many cases killed, by horses and donkeys browsing on the bark;
7. seedlings are easily killed by fire, but trees of 40 cm, or more in diameter appear to be fire resistant;
8. as far as can be ascertained, there is a regular and reasonable seed-fall each year throughout the whole range of Paraná pine.
Despite the fact that in the southern part of the range of Paraná pine it may be possible to regenerate the forests naturally, it is obvious that the bulk of the new forests required will have to be established by artificial regeneration. Some 14,000 hectares have been planted to date by government agencies and private enterprise, but no research work as to the best techniques and methods has been carried out. It has been generally accepted that the cheapest and best method of establishing plantations is by direct seeding on sites which have been either previously burned, or plowed and cultivated. In the writer's opinion, this is not so.
Figure 1. Virgin forest of Araucaria angustifolia in southern Paraná. This pine is the timber species of the highest economic importance in Brazil, used for timber and pulp. It makes up perhaps one-third of the softwood resources of Latin, America, Argentina and Uruguay are established customers for lumber exports and there is a small export to Europe and elsewhere overseas, partly as a result of Brazil's drive to provide a source of softwood material for European reconstruction after the 1939-45 war.
Although the cost of the actual planting of seed should be less than that when plants are used, experience has shown that expensive preparation of the site is necessary in order to secure early survival and satisfactory growth. Moreover, during the first year of the seedlings' life, the area has to be tended at least four times, whereas if plants were used instead of seed, the first year of the seedlings' life would be spent in a nursery and at least one year's costly tending eliminated. It is difficult to make an accurate comparison between the cost of establishing a plantation by seed and by the use of plants, but the writer has come to the conclusion that the use of plants should result in a lower overall cost by the end of, say, three years from the sowing of seed.
Another reason given for adopting direct seeding is that it is impossible to transplant seedlings of Araucaria angustifolia either from seed beds to transplant beds, or from seed beds to plantations. This is stated to be due to the development by the seedling of a very long taproot in relation to the height of the plant above the ground, and the complete absence of lateral roots on the upper section of the taproot. The root system does in fact develop in this way, but this is very similar to the root development of seedlings of Araucaria cunninghamii in Australia. It is considered, therefore, that the adoption of a nursery system developed for this species could also he successful in the case of Araucaria angustifolia.
Briefly, the nursery system for the production of planting stock of Araucaria cunninghamii is as follows: the nurseries use high shade giving about 50 percent light, the beds are 15 meters long by 3 meters wide, and the seed is sown in September in drills 20 centimeters apart; the rate of sowing aims at a stocking of 26 plants per meter of drill, seventeen months after sowing, the seedlings are root-wrenched or root-pruned to a depth of 15-18 centimeters below ground level and, following wrenching, the seedlings remain in the seed beds until the following July, when they are lifted for culling, grading and tubing, by the end of September the first tubed plants are ready for planting in the plantation.
The object of root-wrenching is to sever the long taproot and encourage the development of laterals. By wrenching the plants in situ and by leaving them in the seed beds for a period of five mouths following the wrenching, very few losses are incurred: a callus forms over the cut taproot and quite a good growth of lateral root is obtained. Seed beds are kept well watered following root-wrenching, and the resulting plant is well-balanced in respect to crown and root and can be tubed with only very minor losses.
In Queensland, it has been found that, with the lower rainfall and the short periodic droughts which occur during the planting out season, plus the following winter and spring drought, the use of tubed stock is essential for satisfactory survival in the field.
Research needed in Brazil
For experiments in connection with the establishment of plantations it is desirable to have plants of comparable size and crown development, and this is only possible if nursery plants are available, from which to select the stock for the purpose of the experiment.
The most important investigations which need to be tackled in Brazil are, first, to determine whether it is possible to produce satisfactory planting stocks of Araucaria angustifolia, and if the production of quell stock is possible; second, to ascertain whether more effective and more economical plantations can he established by using such stock than by the present method of direct seeding. 1
1 The proposals that follow err intended for applications at Hangua and Fernando Pinheiro. If successful in these more difficult areas, it should not be difficult to modify nursery and field techniques for the balance of the Paraná pine region.
For such investigations care must he exercised in the selection of seed. As has already been said, Araucaria angustifolia appears to produce an adequate crop of seed each year, the seed maturing from late April to late May. The male and female cones are borne on separate trees, i.e. the species is dioecious. Generally speaking, the average tree is of reasonably good form, hut in certain regions numerous trees may be found with an unusual crown development of what appear to be epicormic shoots; such trees are referred to locally as "Pinhafilhado". Some authorities consider that it is characteristic of soils of low pH and of young forest; others consider the shoots to be the result of insect or fire damage many years ago. However, it is possible that the branching habit is hereditary and if so, the collection of seed from such trees would be undesirable.
Following collection, the seed should be subjected to a flotation test and infertile seed discarded. The fertile seed should then be sown in mid-May in drills 20 centimeters apart and with 6 seeds per 30 centimeters of drill. It will be necessary to place each seed in the drill so that the long axis of the seed is at right angles to the length of the drill and the seed is all pointing in one direction. Depth of cover should not exceed 2.5 centimeters and soil may be used to cover the seed. Ten beds should be sown, sufficient for approximately 15 hectares of plantation under a spacing of 2 x 2 meters.
From sowing in May until the following February the beds should be kept free of weeds, the space between the drills being cultivated at three-weekly intervals, and watering should be carried out so that the beds are kept moist during the period of germination. Once the seedlings are well-established, waterings may be reduced to two or three per week, each the equivalent of 20 millimeters of rain.
In mid-February the plants should be root-wrenched by means of a well-sharpened spade, so that the roots are cut at a depth of 15 to 18 centimeters below ground level, and care should be taken to disturb the plants as little as possible during the operation. Watering, weeding, cultivating must be continued after root-wrenching as required.
At the beginning of July the plants must be carefully lifted; weak, spindly and unbalanced plants should be discarded and the balance graded and tubed. The tubed plants will need to be kept under the nursery high shades until ready for despatch to the plantation. A period of ten to twelve weeks in the tube should be sufficient to enable the plant to recover from the shock of tubing and to become established.
The use of galvanized iron tubes made from flat sheets of 28 gauge galvanized iron, 20 x 15 centimeters, in size is recommended. The initial cost of such tubes may be high but they have a life of at least 12 years. In Queensland the annual cost per tube is equivalent to approximately. 125 of a Brazilian cruzeiro.
If it can be demonstrated that the economic production of tubed, root-wrenched, drill-sown nursery stock is possible, then research into the best procedures for the establishment of plantations using tubed stock will be necessary. (In Santa Catarina and Rio Grande do Sul the use of open root, root-wrenched seedlings has possibilities).
An area of 30 hectares of uniform second-growth forest should be selected, where the soil and topography are also uniform, and this area should be divided into two units each of 15 hectares. One unit should be prepared for direct seeding according to current methods (clearing by bulldozer, plowing, harrowing and planting at 2 meters x 50 centimeters, with the object of thinning to 2 meters x 2 meters by the end of the third year), as follows:
April-July 1954: brush and burn forest cover, clear stumps, and dispose of stumps, logs and roots. Plow to a depth of 30 centimeters and harrow.
July 1954: plant 2 meters x 50 centimeters.
July-December 1954: tend as required.
January-December 1955: tend as required and replant if necessary.
January-December 1956: tend as required and thin to 2 meters x 2 meters.
The procedure for the other unit of 15 hectares, to be planted with tubed stock, should be as follows:
May 1954: sow seed in the nursery.
August-September 1955: brush and burn the area.
October 1955: plant with tubed nursery stock at 2 meters x 2 meters.
October-December 1955: tend as required.
January-December 1956: tend as required and refill if necessary.
By December 1956 the seedlings in the first unit will be two years five months old from seed, and those in the second unit two years seven months old from seed. At this stage a comparison can be made between the two areas in respect to stocking and average height of plants and at the end of 1957 the areas could again be compared.
Detailed and accurate costs for all operations on the two units should be kept, so that a full comparison can be made between the two methods of forming plantations. If it is demonstrated that the use of tubed plants is superior to direct seeding, then research can be instituted for the following points.
The most important point to be decided will probably be the period of time which should elapse between the completion of the brushing and the burning of the brushed material.
(a) Season of planting. Experience in Queensland, Australia, has indicated that the area should be planted as soon after the burn as possible and that planting should be completed before 31 December. Planting commences irrespective of weather conditions although if soil conditions are not good, planting proceeds at a reduced rate until they improve. In the case of Araucaria angustifolia it is suggested that a season of planting experiments should cover the period October through February. If the ability of Araucaria angustifolia to withstand drought is less than that of A. cunninghamii, it may be necessary to postpone planting until the rains of November and December have begun.
(b) Depth of planting. This is important, as shallow planting has an adverse effect on survival, and plots should be put out which cover a range of from, say, plants set 5 centimeters too shallow to those planted centimeters too deep.
(c) Spacing. The spacing recommenced is 2 meters x 2 meters but experiments will be necessary to cover also the following: 1 meter x 1 meter, 1.5 meters x 1.5 meters, 2.5 meters x 2.5 meters, 3 meters x 3 meters, and x 2 meters (the rows 3 meters apart with the plants 2 meters apart along the rows). Information obtained from such experiments should cover cost of planting, cost of tending, branch size, natural pruning, form, height and diameter growth, and volume production per unit area for the various spacings. The thinning schedules to be applied will have to be determined later.
Season of refilling
If planting can be begun immediately following the burn, it may be possible to carry out the necessary refilling by the following January-March. Experimental work should cover refilling in these months plus refilling in the months of August, September and October of the following year. Refilling should not be carried out beyond the second year.
The present method of tending on burnt and brushed areas is to use hoes or knives for the chipping or cutting of the weed growth. This type of work is not effective. The success of tending on rain forest areas depends on frequent and quick removal of undesirable weed growth by grubbing or by hand-pulling, while the weeds are still small. For example, a seedling of Solanum auriculatum pulled out by hand when it is not more than 10 centimeters high is finished with, but if it is allowed to grow until it is 90 centimeters high and then chipped off at ground level or cut by a knife, only that portion of the plant above ground has been destroyed and the rootstock will continue to produce shoots for many years, calling for an expenditure of money several times each year during the first few years of the life of the plantation.
The use of a maize cover-crop does not assist materially in controlling weed growth. It may reduce its rate of growth but it does not prevent germination or survival of weeds. It also has an adverse effect on the planted tree as the root competition from a crop of corn is very great.
An experiment using the following treatments is recommended:
1. control - no tending;
2. tending by grubbing and hand pulling:
3. tending by chopping or cutting;
4. maize cover-crop and tending by chopping or cutting.
The information to be secured will cover frequency of tending, cost of tending, height growth of plants and effects of various tendings on weed succession - the control plot will give an indication of the normal weed succession.
Pruning and thinning
The plantations will not be ready for pruning until at least eight years after planting, and for thinning until probably twelve years, so that the experimental work necessary can be determined later.
Araucaria angustifolia in the adult tree is very frost-resistant but frost in the low-lying sections of plantations in southern Paraná Santa Catarina and Rio Grande do Sul are recorded which are sufficiently severe to kill seedlings if newly planted, or until about 3 meters high. It is therefore necessary to locate frost hollows and either plant them with a frost-resistant species or with pine under the protection of a frost-resistant nurse species.
Since the area of Paraná pine forest that has been devastated is so large, the need for reforestation is obvious. This was acknowledged by the Brazilian authorities as far back as 1940 when the Instituto Nacional do Pinho was set up with, as one of its main objects, reforestation of cut-over areas with Araucaria. The Institute began making plantations in 1944, but the area established is still small. Much more needs to be done, even though reforestation is also being carried out by private enterprise, which in addition is under-taking afforestation of large areas of campo limpo, the natural treeless grasslands which occur over extensive areas in the Paraná pine region.
There are different opinions as to the origin of these grasslands, some people claiming that they originally carried forest whilst others think that they are remnants of the original climax vegetation of the area and were never at any time forested. The latter, according to scientific authorities, appears to be the more feasible theory - "the campos of today represent edaphic relics of a former climate period".
It seems to the writer that, with fire protection, forest would advance into the campo although the pioneering species would not be Araucaria angustifolia but some of the broadleaved understorey species. Once the latter were established it is possible that stocking with Araucaria would occur, but satisfactory growth could not be expected until a suitable forest climate had been developed which would not be a matter of a few years only.
It is for this reason, and not because of any differences which may exist in the chemical and physical composition of the soils, that the writer considers campo soils to be incapable of producing site duality 1 or even site quality 2 plantations. Chemical and physical analyses of forest and campo soils that have been made do not reveal any outstanding differences between soils; however, an examination of the soil microflora and microfauna would undoubtedly reveal differences..
Nevertheless, the establishment of plantations on campo, using methods currently practiced, is relatively easy - much easier than planting on forest land, but it is more expensive.