By DR. ROBERT W. HESS, The Mengel Company
This paper was delivered at the fifth meeting of the FAO Technical Committee on Wood Chemistry held at Appleton, Wisconsin, U.S.A., September, 1951.
Any discussion on tropical forests soon brings out the tremendous scope and the interminable ramifications of the subject. If the extent of these forests, their composition, wood volumes, forestry requirements, and utilization are considered, the subject becomes vast. The experience of temperate forestry is inadequate to span the extremes found in all these regions and it is difficult to make a logical generalization from the enormous number of variants. That the forests can be studied and classified into workable forest types is evident by the excellent work done in some regions. The extent of this detailed classification and enumeration is, however, pitifully small in comparison with the needs. The development of forestry practices and adequate utilization studies lag far behind. Fortunately, taxonomic botanists have explored most regions of the earth and have identified most of the important species.
Prospects of obtaining any large amount of additional information in the near future are not promising. It is true that worthwhile projects of significant scope are being carried on in various parts of the world; the fact remains, however, that for almost any given tract of timber in the less heavily populated regions of the tropics very little information can be found concerning the physical, chemical, or processing properties of the woods, the natural characteristics of the trees, or the silvicultural methods applicable to the type of forest. More forums and publications are needed to bring out available information, and greatly increased facilities for studies of tropical timbers and forests are required to supply basic data.
The dearth of specific information should not deter the utilization of tropical forests. Scattered information points out the trends, fundamental principles are applicable, and carefully directed applied can yield answers in a comparatively short time.
Available Timber Supplies
While the area of tropical forest land of all types is very large, that which is capable of continued production of wood for pulp is less than half of most published figures. Many forest regions of the tropics support a much higher population than is generally realized. A large proportion of these people practice some form of shifting cultivation which removes the timber and in some areas depletes the soil, thus preventing the reestablishment of good forests for very long periods. A large percentage of the tropical soils are clay, some are coarse sand and in both cases there is a layer which is very high in organic matter on top of the mineral soil. After exposure to sun and heavy rains for one to two years, as with farming, the organic matter is virtually all lost. It is not surprising that recently abandoned agricultural lands frequently support only a poor growth of weed tree species. The amount of such cut-over land and the condition of the re-stocked farms is a matter for conjecture, but the area is huge and the quality of the new forest generally very poor. Thus, the search for forests suitable for the production of pulpwood must take into consideration the timber, soil, and land history.
Coniferous Forests
The coniferous forests of the tropics are relatively small in extent and most are being heavily cut. The pines of Mexico and Central America offer possibilities for pulp and lumber production in certain areas, particularly if a planting program is started at an early date to supplement the acreage of old growth now in existence. In most regions considerable railroad or main automobile road construction will be required before pulpwood can be hauled to a suitable mill site. Large rivers are available at lower levels, but the suitability of their water for pulp production is usually unknown.
No coniferous forests are available in the northern portion of South America. The heavy cutting of the Paraná pine in southern Brazil for lumber and veneer makes use of this species in its natural state for pulp problematical. Mexican pines can probably be grown rapidly in this area, offering a means of establishing a permanent source of supply.
Conifers have been largely cut out in Chile except in remote mountain areas, and plantations would appear to be the only suitable source of large quantities of coniferous pulpwood in most of this region.
The pine forests of the West Indies are of limited extent and heavily cut-over. The same is true of coniferous forests of the Mediterranean region. In South Africa, extensive areas of exotic pines have been planted and have attained saw-log size. The podocarps and red cedar of north-east Africa are of little interest for new pulp exploitation. Conifers exist in the mountains of south-east Asia and on some of the islands of the southwest Pacific; it is possible that certain areas could be found here which would be suitable for pulp production.
The development of forestry practices for securing a sustained yield in tropical pine forests would not be exceptionally difficult for an experienced forester. Local observations and adaptations of practices in the southern pine areas of the United States would permit a start on a limited basis. Reproduction can probably be obtained satisfactorily wherever there is a fully stocked stand of pine and where intrusive hardwoods are not too plentiful. In areas where hardwoods and pine are mixed, particularly at highest elevations and in the moister areas at lower elevations, it may prove difficult to prevent replacement of conifers by vigorous hardwoods. As in temperate zone forests, it is important to determine the rate of growth and productive capacity of any tropical coniferous forest selected for possible pulpwood production. Not all tropical forests grow rapidly and many have a low volume yield per acre.
One of the most promising future sources of pulpwood from the tropical regions is from pine plantations. The Australians, New Zealanders and South Africans have demonstrated the practicability of obtaining very rapid growth and high volume yields from planted exotic pines, and it is reasonable to assume that similar success can be obtained in Central and South America. Careful analysis of the problem and considerable research should precede any large development, but there is every reason to believe that it can be accomplished in a comparatively short period of time. Examination of planted individual trees and any small plantations in the region will yield much information if soil conditions, elevation, rainfall and other factors are taken into consideration. Studies of natural reproduction in the locality may yield vital data. Provisions for detection and control of disease and insect epidemics should be an integral part of such a program. While sufficient information exists to permit a reasonably sound selection of species, good management requires a continuing study of better species and strains for increased yields. Location of suitable soil types may prove difficult, especially in areas where farming is extensive. It is assumed that no attempt would be made to establish pines in climatic conditions not known to be suitable for their growth and development.
A reasonable solution to the time factor involved in the production of pulpwood with plantations of tropical conifers would be to obtain a tract of timber sufficiently large to supply the required volume of pulpwood and to pay for planting costs until the plantations begin to produce. Complications will obviously arise in the future as the reproduction of cut-over land and the planted stock of the same age classes reach maturity. It should be possible to overcome this maladjustment of the first cutting cycle by varying the growth of natural as compared with planted stock, the age and size at time of cutting, the use of thinnings while growing a stand of saw-log timber on part of the area, the purchase of pulpwood during part of the-period, and similar methods. Careful adherence to well made long-range plans would be required.
In optimum areas rapid rates of growth may be expected and volume yields of pulpwood may be expected in twelve years, although this may not be the age at which the greatest volume yield per acre is obtained.
Hardwood Forests
The great bulk of the forests in tropical regions consists of hardwoods in varying degrees of mixture. Along the coast a riparian type, often predominately mangrove, is commonly found, usually forming a narrow band adjacent to, and partly in, the salt water. Immediately behind this in deep swamps and along the large rivers often lie more or less similar swamp types, characteristically one or more species with stilt roots, and others with abnormal (sometimes grotesque) developments of root flanges.
These vast areas of mangrove, black mangrove, and swamp forests are a challenge. In addition to the large volume of wood and the comparatively few species involved is the interesting high tannin content of the bark of some species. Reproduction from seed and sprouts will probably be excellent, at least for the second generation. If the wood can be processed to advantage there remains the development of an efficient, presumably water-borne, means of harvesting the trees from their interlocked stilt-like or high flanged stumps. The adaptation of a barge as a combined skidder and loader, using a cable haul from a spar tree, should permit low logging and hauling costs. Stumpage costs or fees should be extremely low for this at present almost worthless timber.
Above and inland from the swamp forests lie the great tropical evergreen hardwood forests. 1 These range from periodically inundated lands along the rivers to pockets high on the mountain slopes, and even to forests in the nearly perpetual cloud cover of mountain tops. The forests are evergreen, although some of the trees may lose their leaves periodically. This is the forest that covers enormous areas of eastern Central America, northern South America, the Amazon Valley, West Africa, the Congo River basin, Malaya, Borneo and the Philippines. It is primarily the extreme heterogeneity of this type of forest that has so far prevented extensive exploitation of its many valuable timbers.
1 The term is used loosely here to apply both to rain forests and to moist evergreen forests. Moist and dry deciduous forests are not considered.
Contrary to the usual conception, within reasonably restricted regions the number of forest types in the tropical evergreen forest is not excessive. In fact, over hundreds of square miles it may be possible to classify the forests into a dozen major types; a given area of the eastern United States might have as many. Here, however, enters a complicating factor.
The occasional or rare species in the majority of the tropical rain forest types make up a significant percentage of the total. There are not only a great many of these rare species, but they also occur with varying frequency in different parts of the same or similar type of forest. Thus, it is the usual practice to consider the frequency and value of only the predominant species, except for a few rare kinds which are particularly valuable (e.g. mahogany and rosewood). This procedure appreciably lowers the usable volume per acre.
There seems to be little chance of successful pulpwood operation in the more heterogeneous types of tropical evergreen forests. Until a universal pulping process is developed, which will utilize all kinds of wood, the possibility of harvesting sufficient volume per acre appears remote. The most practicable operation in forests of this type would appear to require complete removal of the existing forest stand and replacement with one or two planted species. The traditional practice of shifting cultivation is being used to a limited extent to obtain such clearing and planting. As most of this farming is of one to two years' duration, the rate of timber removal is significant in populated regions.
An additional detriment in the use of the mixed tropical hardwood forest for pulp production is the forestry aspect for continued reproduction. In most of the forests there are one or two tiers of smaller trees below the dominants. Even in forests which are composed predominantly of a single species there are scattered individuals (often large) of other species. The second generation is, therefore often difficult to determine and commonly impossible to control advantageously.
One solution to the exploitation of mixed evergreen forests is multiple usage. With a wide variety of wood properties represented among the species, the manufacture of a variety of products would make most efficient use of the forest. It is not unreasonable to assume that a mixed tropical hardwood forest could be cut for pulpwood, lumber, veneer logs, piling, and railroad ties. Such a combined operation would distribute the costs of transportation facilities and reduce the logging costs inherent in forests with a comparatively low volume per acre. Unfortunately, most companies are not interested in such a diversified enterprise and few are capable of finding profitable uses for a large number of tropical hardwoods.
There are certain natural forest types within the tropical evergreen forests in which a single species constitutes a major part of the wood volume. A few of these offer interesting possibilities for pulp production. The woods of some have been tested in the past - generally with discouraging results. Despite this, anyone interested in the exploitation of tropical hardwood for pulp would be well advised to attempt to overcome the pulping deficiencies of species which are locally very abundant, rather than to search for comparatively rare species with good pulping possibilities.
Considerable areas of new land are formed on bars and deltas in some large tropical rivers. The trees which spring up on these have been suggested as a source of pulpwood, although it is not definitely known whether there is sufficient volume and whether the woods are suitable for pulp.
In most moist tropical regions cleared land that is abandoned or neglected is quickly covered by a heavy growth of trees, brush, and vines in varying proportions. Most of these plants grow very rapidly but, with a few exceptions, do not generally attain any great size. The rapidity of growth and ability to grow well in the open suggests that these areas might be subjected to clear cutting for pulpwood. Unfortunately, there is usually a mixture of species varying widely in wood properties. A number of the woods are light and soft, indicating a low unit volume yield, and often short fibers, even if their properties are satisfactory. More over, there is the problem of losing the tract to, or expensively combatting, the adventitious vines that choke all growth in many areas, particularly those with poor soil or which have suffered repeated clearing or burning. In few areas will it prove practicable to manage or harvest for pulp the natural growth that follows agriculture or other clearcutting operations.
Although not all of the variants and possibilities have been considered here, it is evident that only a limited number of the evergreen tropical hardwood forest types are at all suitable for the production of paper pulp by methods in use today. Where large volumes of one or more species having suitable technical properties occur over a limited area, the natural forest may be used to produce pulpwood, at least for one crop. The alternative is the establishment of plantations of one or more hardwood species. These will presumably be rapidly growing types, such as those which characteristically encroach on abandoned land. On fairly good soil with selected species, it is not unreasonable to expect an average diameter growth of one inch per year and the theoretical productivity per acre will be very high. Poor soil or unsuitable moisture conditions will drastically reduce the rate of growth in the tropics, as elsewhere.
When the species has been selected the operator will probably be faced with the problem of establishing a nursery, raising seedling stock, and conducting planting and cultural operations with little, if any, information or experience to guide him. Control of diseases, insects, and competitive plants will be problems of the moment; fortunately, recently developed chemicals give material aid in this phase of the work. Also, the extremely rapid growth will permit early observations and, therefore, a more rapid accumulation of experience. There appear to be great possibilities in the production of cellulose or pulp with rapid-growing planted tropical hardwoods, and among the hundreds of promising species that have not been tested are probably several excellent producers.
One important factor will be the labor involved in clearing areas or lines for planting and for the protection of planted stock during the first two years. Probably similar cultural work will be advisable to assure survival and to stimulate the growth of seedlings in naturally reproduced forests. While this type of labor is not costly in tropical regions, the size of the areas to be dealt with, and the frequency of clearing required, makes the operation one of the highest per acre costs associated with the growing of planted tropical hardwoods. Sprays or other applications of chemicals may prove economical methods of controlling invading vegetation in certain instances, but often these will be more costly than manual operations with the machete.
There is a practicable approach to the utilization of an existing tropical hardwood forest for pulp and for obtaining successive cuttings from the same area. As the initial cutting proceeds, the entire area is cleared of vegetation; it should then be thoroughly burned. Perhaps some of this clearing and burning operation can be carried out without direct charge by permitting villagers to grow one crop of maize on the cut-over land. (This practice would deplete already poor soil and might seriously shorten the life of the operation). Following clearing, seedling stock would be planted and protected for two years. Such an operation would probably require the establishment of a nursery prior to cutting. A period of research into nursery and planting practices might be necessary to ensure success. The species would then have to be selected for planting and seeds or "cutting slips" obtained a year before beginning harvesting the pulpwood. However, if carefully planned and organized, an operation combining the cutting of old growth timber and complete replanting should prove successful in tropical hardwood regions.
Bamboo and Palms
The use of bamboo as a source of pulpwood has many advocates. Among its advantages is the continuing production of stems for harvest, eliminating the need for replanting. One serious difficulty is that of obtaining sufficient plants to start operating on a large scale. A further obstacle is the five-year period which must elapse before the first cutting. The large gross volume of stems per unit weight or volume of cellulose may add to production costs. In spite of these deterrents, bamboo must always be considered in any proposed program for the production of pulpwood in tropical regions.
Hundreds of species of palms occur, often abundantly, in the tropics. Some kinds grow rapidly, often in close stands; in isolation they may reach large dimensions. Their woods vary from soft and spongy to extremely hard and heavy, sometimes with a density greater than that of water. Characteristically, the logs have a soft inner core and a harder outer shell. The wood is composed of long, very hard strands of fibers imbedded in a tissue of short parenchymatous cells. It is the abundance and spacing of these strands that causes most of the density variation in the log and among the species of palm. In lower density wood, the amount of long-fibered material obtained would constitute only a small percentage of the total volume of material. Certain species of palms could presumably be grown for their wood just as some are now grown for oil, dates, and coconuts.
Deterioration of Pulpwood
In tropical regions, and particularly during rainy periods, the rate of sapwood deterioration from stain, decay, and insects is extraordinarily high. Water storage might be a partial answer, although brackish water must be avoided. Water spraying is probably not sufficiently effective. Certain chemical sprays or dips will control the insects and reduce stain if they are not too expensive for this application. The best solution would seem to be utilization very soon after cutting.
Seasonal Consideration
Throughout the tropics there is a general belief that logging cannot be done during the rainy season. The extremely heavy rainfall, lack of all-weather roads, and the soft character of some soil types makes the wet season a formidable obstacle. However, with recent improvements in transportation facilities and equipment, more and more operations are working throughout the year. Better roads, improved bridges, good drainage, clearing of rights-of-way to admit sunlight, etc. are required for road haul. Light rail equipment is economical under certain conditions. Cable skidding should be used to a greater extent. Tractors are frequently used, but full advantage is not made of the attached winch for bunching preparatory to skidding. Vehicles with extra large tires can probably be used in some instances for pulpwood of relatively small diameter. In general, logging during the wet season requires preliminary preparation, the use of special equipment, and ingenuity. Few tropical hardwood forests will be as difficult to log during the rainy season as were the tupelo swamps of the southern United States.
Location of Pulp Mills
There are many factors in favor of locating the pulp mill near the timber, in the tropics. Reduction of volume and weight in shippings is obvious; deterioration of pulpwood will be reduced and costly chemical dips or sprays will be at least partly eliminated; closer scheduling of woods operations is possible; labor costs are lower; tax rates are very favorable. Moreover, a better local political situation is established, which is a very important factor. (In most countries, there is a strong feeling against the export of raw material without at least preliminary manufacture in the country of origin. This feeling and the attendant pressures are increasing). In all but a few countries, foreign investments in manufacturing enterprises are encouraged and protected, and, if it is possible to include one or more carefully selected residents of the country as stockholders or sub-contractors, the position of the company can be very strong.
Weighing against the establishment of a pulpmill in tropical regions are equally imposing deterrents. There is always the reluctance to make larger than necessary investments in a foreign country. Lack of familiarity with the language and customs of the people is a real obstacle. Technical men and supervisors require salary and other compensations for working in tropical countries. (Lower diving costs and tax advantages partially offset this. Rapid air transport at reasonable rates has further reduced the objections). There is insufficient knowledge of the properties of the woods, the processing methods best adapted to each species, the life habits of the trees and the best methods of forest management. Fear of political upheaval or entanglement resulting in unreasonable costs, or even expropriation, is undoubtedly the single factor which is most retarding the development of tropical resources.
A logical sequence for the development of a source of tropical pulpwood might be as follows: first, the study of various locations, forests, and land types and the selection of one. Second, the obtaining of a concession, contracting for the timber or purchase of the area. Simultaneously arrangements for taxes and liabilities should be agreed upon with the government - additional stated benefits to accrue when a pulp mill is established. Third, if planting is involved, a nursery should be started and experiments conducted. A properly balanced area will permit five years of nursery development before the first plantings are made. Fourth, installation of equipment, transportation facilities, etc. Fifth, commencement of operations. Initially, the pulpwood would be sent to an established mill, and eventually, if everything went well, a mill would be built near the wood source.
The economic and technical problems of tropical wood utilization are great, but not insurmountable. The manufacture of pulp from these sources is entirely practicable if careful and comprehensive planning, technical control, and judicious diplomacy are practiced.
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International Union of Forest Research Organizations The Joint Bibliography Committee of the International Union of Forest Research Organizations and the Food and Agriculture Organization of the United Nations met at Wageningen, Netherlands from 30 August to 4 September, 1951, for its fourth session. Prof. E. Saari of Helsinki, Finland, presided. The Committee reviewed the progress on the adoption of the Oxford System proposed for classification of forestry literature, now officially adopted by FAO and the Union for this purpose. The Committee also considered at length the organization of international documentation in forestry, analyzing the current work of existing centers, the gaps which still exist in such services and the possible methods of remedying them. Its recommendations will be presented to the pertinent organizations for action. Afterwards the Permanent Committee of the International Union of Forest Research Organizations met from 4-8 September. Seven members were in attendance plus an equal number of the leaders of technical research sections. Professor H. Burger presided. The Committee reviewed the general activities of the Union and the progress made by various research sections in facilitating contact between technical workers and in formulating research problems of international importance. The Committee also made tentative plans for its next Congress, proposed for Rome in 1953. |
