Extracts from a paper submitted to the Asia-Pacific Forestry Commission
by A.B. WALTON, R.C. BARNARD, and J. WYATT SMITH, Malayan Forest Service
1 Tropical wet evergreen Dipterocarp forest type, Manual of General Silviculture for India, (Champion and Griffith, 1948).
THE object of Malayan forest management in the silvicultural practices described below is the conversion of the virgin forest containing trees of all ages and sizes (the largest of which are overmature and moribund) and a mixture of both good quality and, at present, unutilisable timber species, into an even-aged forest containing a high proportion of the best quality indigenous timber species. Though even-aged, the new crop will not be even-sized on account of natural variation in growth rates of the different species, genera. etc., and will develop into two or more storeyed high forest with a lower storey of species which do not grow beyond pole size and a natural undergrowth . Intermediate fellings of timber-sized trees will be carried out in the new crop of the shorter-lived species on reaching their technical rotation, together with commercial thinnings of any species. The rotation age of the final crop is expected to be between 60 and 70 years for the rapid growing light-hardwoods and 100 to 120 years for the heavier primary hardwoods by which times the trees will be 6 to 8 feet (1.8 to 2.4 m.) girth above buttresses.
The silvicultural system now practiced after some 30 years' experience and research may best be termed clear felling over natural seedling regeneration. This short title will bring an incorrect picture to the mind of foresters without experience of tropical rain forest and a short description of the appearance of the forest after felling is necessary to correct this.
The actual felling consists of the exploitation of all timber, firewood and pole trees which the contractor working under felling permit will or can be persuaded to take. The completeness of the operation depends on the proportion of utilisable timber trees in the growing stock, the distance from the market or sawmill and the local demand for firewood and mining or building poles. After exploitation there is always left a number of large overmature defective trees or trees of a species not at present utilisable on account of hardness, silica content or poisonous sap; also trees or poles of valuable or other species below the minimum exploitable girth limit for timber (now about 4 ½ feet or 1.4 m. girth but varying with local timber demands) which cannot be exploited owing to species, form or market conditions. When, therefore, exploitation has been completed according to present standards in Malaya, there may he half or mole of the growing stock still standing, an undergrowth of woody species and palms and a tangled mass of crowns and branches.
Standing trees and poles down to 2 inches (5 Cm.) diameter (except those of timber species which are of good form and undamaged) are poisoned either progressively as felling is completed or over the whole compartment immediately afterwards, before the extraction tracks become overgrown. A number of the poisoned trees will be dead within a month or two and a high percentage by the end of a year, while a few will remain alive due either to faulty treatment or to the species being unaffected by poison girdling.
A year later there will be a very dense re-growth of innumerable species, mostly high forest forms with some secondary growth species up to 15 feet (4.6 m.) tall entangled with woody and herbaceous climbers; and standing over this will be the dead poisoned trees already starting to drop their branches and a few stems of timber species of pole to young tree size usually responding vigorously to full light. Thus Malayan "clear felling" is a mixture of felling and poisoning, and the ground is by no means "clear" at any time during the operation except in the immediate vicinity of felled stems and along the extraction tracks.
This system has been evolved from a cautious shelterwood system with several successive seeding fellings at intervals of a few years, partly on account of the development of exploitation methods from selective hand sawing (with single buffalo extraction) to sawmills (with lorry, light railway and winch extraction), and partly as a result of research and observations which are briefly summarised in the following paragraphs.
Conditions in virgin forest are ideal for the germination of high forest species and large numbers of seedlings will survive for several years, though development is negligible until the canopy is opened. Good seed years of the more popular timber species (Dipterocarps for the most part) are infrequent, localised and unpredictable, but the large number of species now acceptable for sawmilling has increased the economic seed potential enormously.
Undergrowth, with the exception of certain stemless palms which are abundant in some localities, is comparatively sparse under virgin jungle but, within a fey. months of partial or complete opening of the canopy, a very dense growth of woody and herbaceous species and climbers develops. For three to five years this re-growth is so dense that there is small chance of survival for any subsequent seed which germinates; there-after, seedlings appearing in the new crop have little prospect of development without frequent assistance.
Experimental treatment plots have shown that most of the popular meranti (soft-wooded Shorea spp.) respond and develop most vigorously when exposed to full overhead light, and other economic species respond similarly.
Results of survey
Observations of areas over which uncontrolled timber felling took place during the Japanese occupation, areas clear-felled for cultivation but never burned or planted, and areas laid flat by wind storms where regeneration received no assistance in the early stages have shown that the dense herbaceous climber stage is ephemeral and that a good stocking of timber species will survive undamaged, develop rapidly and win through to crop dominance without assistance, while slower growing economic species survive as sub-dominants. These areas also confirmed that seedling regeneration must have been present on the ground at the time fellings or wind storms occurred, as no seed-bearers of the predominant timber species remained within seed dispersal range of much of the regeneration.
Some three to five years after a complete opening of the canopy, the re-growth, if left untouched, develops into a dense young pole crop comparatively free of undergrowth. In this stage it is a cheap and easy operation to improve the value of the composition and reduce excessive competition by poison-girdling undesirable stems and cutting surviving climbers.
Thus the essentials for the successful establishment and early development of natural regeneration in Malayan lowland forests are:
(a) adequate stocking of seedlings of economic species;(b) complete removal of the canopy in one operation;
(c) no tending until the re-growth has passed the dense climber stage and become comparatively clear below the canopy;
(d) maintenance of an adequate new canopy to prevent the re-development of climbers.
The first operation in the regenerative sequence, therefore, is to ascertain the frequency and distribution of seedling regeneration of economic species by milliacre sampling which provides figures of the percentage of the area stocked with seedling regeneration, its distribution and its composition. At the same time, a 10 percent or 20 percent enumeration of trees over 14 inches (36 cm.) d.b.h. is done to ascertain the numbers of seed bearers and the volume of exploitable timber available.
During the last three years, milliacre sampling has been carried out over approximately 7,500 acres (3,000 ha.) of compartments at ½ to 2 percent intensity and up to the present time adequate seedling regeneration has been recorded in all cases except a few in Kedah and Perlis where the forest approaches the tropical semi-evergreen type. A 40 percent well-distributed stocking of approved economic species is considered sufficient for prospective successful regeneration. By approved is meant species and genera which can be identified in the seedling stage, are known to grow into acceptable timber trees and to exploitable size, and are not usually hollow when of timber size. Thus the figures obtained give the worst possible picture of regeneration prospects and will always be supplemented by seedlings whose future development is uncertain. The approved list contains, at present, the names of some 120 tree species or genera of Malayan-wide distribution, whereas more than double this number are known to be utilised for timber, and species reaching timber size exceed 600.
This milliacre sampling also records the occurrence of any valuable or locally desirable species to which preferential treatment may be accorded under the objects of management for the working circle. Summaries of typical compartments which have been sampled in this way are given below:
TABLE 1. - TYPICAL SUMMARIES OF SAMPLED COMPARTMENTS
|
State |
Reserve & Compt. |
No. |
Area, acres |
Area, ha. |
% sampled |
% sample stocked |
No. of species recorded |
|
Kedah |
G. Jerai |
8 |
275 |
111 |
1/2 |
48 |
19 |
|
Negri Sembilan |
Sg. Menyala |
10 |
409 |
166 |
1/2 |
65 |
23 |
|
Johore |
G. Arong |
81 |
223 |
90 |
1 |
77 |
14 |
|
Johore |
Jemaluang |
6 |
450 |
182 |
1 |
58 |
16 |
Not more than 18 months before a compartment is clue for exploitation under working plan, milliacre sampling is done and, if the seedling stocking and distribution are satisfactory, the felling permit is issued when due. Trees to be felled are marked progressively over the compartment and poison girdling of unexploited trees and poles carried out as described above, the whole operation being completed within two years, in order to ensure sufficient uniformity in the size of the new crop to enable it to be treated as a whole. If exploitation is prolonged over many years, one part of a compartments might be ready for silvicultural treatment while other parts had not yet been felled Large compartments may be sub-divided as necessary when the rate of exploitation is too slow.
If seedling stocking is found to be inadequate, a study is made of the frequency and abundance of seed-bearers, as shown by the enumeration of economic trees of exploitable size. If seed-bearers are well distributed, the compartment should be retained untouched, if possible, under plan, until a seed year occurs. If seed-bearers are scarce, postponement of felling is unlikely to result in any appreciable increase in seedling frequency or distribution and the same sequence of regenerative operations is carried out; if insufficient regeneration is established, it may be supplemented by artificial regeneration.
Sampling and treatment
Between three and five years after exploitation the dense re-growth has reached small pole size, passed through the dense herbaceous climber stage and is comparatively free of undergrowth. If cleaning (i.e. cutting climbers and saplings of useless species and thinning out desirable stems) is done before this stage, as was done in the past, the growth climbers is encouraged, the spaced-out stems are quickly smothered and, without numerous surrounding stems to support them, frequently broken or bent over by the weight of the climbers. Under these conditions, therefore, cleanings have, to be repeated several times at short intervals before the retained stems form a canopy dense enough to suppress the growth of climbers and became capable of developing into a satisfactory crop.
The density of the re-growth resulting after felling makes it difficult to compile reliable information about the regeneration and the amount of assistance it requires. It is obvious that this information should be obtained before any treatment is started, and to this end linear regeneration sampling was evolved. This has been fully described in The Malayan Forester, Vol. XIII, p. 129. Briefly, it consists of recording the species, size and dominance class of the most promising economic stem in each sample unit area and the incidence of climbers and undesirable dominating trees or palms. Analysis of the figures so obtained (usually a 5 or 10 percent sample) gives reliable information on the stocking, distribution, composition, development and competition status of the economic stems in the new crop and provides a basis for tending prescriptions and future management. Again only approved species are recorded as in milliacre sampling of seedlings, and the size classes taken into consideration cover only those likely to occur in the general level of the canopy; small suppressed stems are difficult and expensive to assist, and advanced regeneration which survived the felling is above the re-growth and in no need of immediate assistance.
Between three and five years after felling is completed, 1/160 acre (1/400 ha.) regeneration sampling is done of regeneration between five feet tall and four inches diameter and the first treatment, if necessary, prescribed and carried out. At approximately 10 years after the felling, 1/140 acre (1/350 ha.) regeneration sampling is done, recording stems of 2 inches (5 cm.) diameter and larger, and any further necessary treatment decided or the compartment passed as regenerated.
These treatments normally include some or all of the following operations:
(a) cutting all climbers and rotan;(b) cutting stemless undergrowth palms;
(c) poison-girdling any surviving useless trees of the old crop;
(d) poison-girdling weed-tree species (very fast growing, persistent, "wolf" species not acceptable for timber) and stemmed palms in the new crop;
(e) poison-girdling all badly shaped, damaged or diseased stems;
(f) selective thinning (by poison girdling) in favour of desirable species where these are subjected to the competition of less valuable forms.
A general undergrowth cutting or elimination of all uneconomic species should never be done; the aim is to remove undesirable competition while retaining as complete a canopy as possible. In the early stages of their development, many desirable species compete, in height growth with fast growing and less valuable forms and may reach 25 feet (7.6 m.) in height whilst still only ½ to ¾ inch (1.3 to 1.9 cm.) diameter. Removal of the surrounding vegetation in the circumstances would he disastrous.
By the time the new crop is 10 years old, further tending is unlikely to be required. Marked commercial thinnings of poles, exploitation (on reaching timber size) of trees which were immature at the time of the final felling and exploitation of species reaching their technical rotation will take place between 20 and 40 years after original felling.
In conclusion, the following table summarises the sequence of operation:
TABLE 2. - SEQUENCE OF OPERATION
(n = the year in which exploitation commences)
|
YEAR |
OPERATION |
|
(n-11/2) to n |
milliacre sampling of seedling regeneration and enumeration of exploitable sized timber trees |
|
n to (n + 1) |
complete exploitation over whole compartment in two years or less and poison girdling of non-utilisable stems and species down to 2 inches(5 cm.) diameter |
|
(n + 3) to (n + 5) |
30 ¼ sq. yds (25 m2) linear regeneration sampling followed by no treatment, one or more of operations such as climber cutting, selective thinning, etc. as described above or supplementary planting |
|
(n + 10) |
121 sq. yds (101 m2) linear regeneration sampling followed by no treatment, any of the treatments described above, supplementary planting or passed as regenerated |
|
(n + 20) to (n + 40) |
sampling or enumeration followed, if necessary, by a commercial thinning of poles and timber sized trees |
Because of the ease with which natural regeneration of most of the commercially valuable timber trees can be achieved, and the large areas of virgin forest still awaiting conversion, artificial regeneration is unlikely to play more than a subsidiary role in the silviculture of Malaya. Nevertheless, the claims of artificial regeneration cannot be overlooked as a means of improving the stocking of forests deficient in economic species, reclaiming abandoned, degraded and mined land, providing fuelwood and poles in areas where lack of proper land planning has resulted in the elimination of forest over a large area and producing more valuable or larger yields by the introduction of exotics.
In the early days of forestry in Malaya, before the possibilities of natural regeneration were understood, planting the primary hardwoods, mainly chengal (Balanocarpus heimii), in lines in the forest was carried out over a considerable area, but failure to realise the need for opening the canopy resulted in their suppression or failure and artificial regeneration fell into disrepute. There are also difficulties in the formation of plantations particular to Malaya which are encountered to much less an extent in temperate or seasonal climates.
The difficulties of planting and especially in planning a planting program in Malaya are numerous. Seed years of all but a few species are infrequent and unpredictable, seedfall may occur in any month in the year and, except for certain Leguminosae, the seed of few species retains its viability if stored for more than a week. Thus any long-term planning is of necessity restricted to a few species which fruit annually or produce seed which can be stored for several v ears and to species of which wildings can usually be found in quantity. For other species, two to three months between flowering and fruitfall, followed by four to eight months in the nursey before planting out is the only time in which plans can be made and labour organised, and a general flowering is by no means necessarily followed by a plentiful supply of viable fruit. Furthermore, there is no seasonal growth or resting season; seedling development in nurseries is rapid and they may reach the most suitable size for planting out (for survival and handling) at any time of the year.
Problems of development control
Some control of development by transplanting and wrenching can be effected but it increases the cost per plant. Again, should the plants by good planning or good fortune reach the most suitable size at the time of year when wet weather may, on average, be expected, it is always possible that the rains may not oblige or a drought occur after a short period of rain, with fatal results to seedlings already planted out. There is also no method yet discovered of forecasting the trend of the weather or even what may be expected in the next 24 hours. On the east coast and in the extreme north of the Federation of Malaya, the wet seasons are less unreliable.
Direct sowing has been tried on many occasions but only rarely has even moderate success been obtained. Wilding stock shows considerable promise and avoids expensive nursey work. Little progress has been made on vegetative reproduction, but few timber species seem easily propagated by cuttings.
In the formation of plantations, weather is the principal factor determining success or failure, and in the variable climate of Malaya the amount of rainfall during the critical period must be a matter of luck; planting only when the soil is thoroughly moist, in the first half of the wettest average period for the locality, is the only precaution which the forester can take to reduce chances of failure owing to drought.
Other points in planting technique which have been observed to assist survival are thorough watering of the seed bed before lifting seedlings and special care in the prevention of dessication of the seedling roots. indications are that seedlings are far less tolerant of exposure of their roots than is customary with temperate species, so seedlings are bundled and their roots wrapped in damp sacking (or packed in damp moss for long journeys) immediately on lifting, and only removed one by one as planted. Planting of seedlings ex-bamboo tubes has been frequently done in the past and survival in trials has been up to 50 percent better than bare-rooted nursery seedlings. Trials are being made of small clay pots (returnable for further use), veneer tubes and soil blocks. Such seedlings are mole expensive to raise and transport to planting site. but may cost no more for each plant established or for a minimum established stocking per acre. Vet to be investigated are economies of close planting of wildings and seedlings or wider planting of tubed or potted seedlings, to obtain the same final stocking of established plants.
Variation in planting distances
Planting distances vary with the site type and purpose of the plantation. If there is a good local demand for poles, close planting at 6 x 6 feet (1.8 x 1.8 nit) or 8 x 8 feet (2.4 x 2.4 m.) should enable planting costs to be recovered by sale of poles in the first 15 to 20 years. but this requires large numbers of seedlings which cannot always be raised owing to uncertainty of seed supplies. If planting in secondary growth for timber production. wide spacing (40 to 80 per acre, 100 to 200 per ha.) should theoretically suffice for there is no lack of natural "fillers". The latter species, however, at first rapidly outgrow those planted and are apt to smother rather than nurse their charges which, if spaced far apart, become difficult to locate and much time is wasted during tending.
A layout of 8 to 12 feet (2.4 x 3.7 m.) spacing in lines 33 to 66 feet (10 to 20 m.) apart has proved cheaper and easier to plant and to tend subsequently, hut poisoning of fast growing secondary growth stems some distance from the planting lines must be regularly clone or an overthead canopy is formed and the line becomes a tunnel Another method that has been tried is group planting at wide spacing; 5 to 9 seedlings are planted at 4 to 6 feet (1.2 to 1.8 m.) spacing in groups at 11 or 22 yards (10 or 20 m.) intervals giving 40 or 10 groups per acre (100 or 25 per ha.) respectively. The groups provide a reserve against casualties and the several plants afford each other mutual protection and compatible composition.
In the establishment of any plantation, frequent tending during the first five years or so is essential or the plants become overgrown by grass, climbers or woody species and in comparison with natural regeneration, the cost is very high.
The following brief descriptions indicate some of the site types on which artificial regeneration will be required or has been practised.
Land which has been mined by opencast methods is left very broken and pitted with large expanses of sand or gravel tailings which vegetation is extremely slow to colonise. Few attempts have so far been made to plant on such sites, but it is probable that the first step will he the establishment of a creeping or grass cover to provide some organic matter, stop erosion and improve the micro-climate before pioneer tree species can be successfully introduced: Casuarina equisetifolia however shows promise in the early stages. Dredged land is fairly level, can he "slimed" to provide some nutrients and improve moisture-holding capacity and can he drained or irrigated without great difficulty. It is usually colonized by grass within a reasonable time and grazing follows. It is probable that some of the less exacting secondary growth species could be established successfully.
Land which has been cropped for three or more successive years almost invariably becomes sheet lalang (Imperata cylindrica) which is regularly burnt (intentionally, accidentally or spontaneously during droughts) and colonising woody species are destroyed, while the lalang recovers vigorously and spreads into surrounding forest or scrub which is scorched and weakened by the fire. The reforestation of any such areas is dependent upon fire protection which is both difficult and expensive, as several diggings or ploughings are necessary to kill the under-ground rhizomes. Spraying with sodium arsenite will control lalang, but must be repeated at regular intervals indefinitely. In a year or two lalang can be converted to grazing grasses, which do not burn, by means of mechanical cutting, light harrowing and intensive grazing: The cattle eat new young shoots of lalang and other grasses collie in rapidly from their droppings. Economic mechanical cutting, however. is only possible on comparatively level land which has been under lalang so long that tree stumps have rotted away. Provided fire protection can be effected, woody species will develop in lalang and several hardy pioneer species such as leban (Vitex pubescens) and tembesu padang (Fragraea fragrans) can be easily raised and successfully planted; they will kill out the grass by shade in about seven years, after which more valuable species can be underplanted.
Forest which has been cleared for one or at most two crops and then abandoned will revert to secondary growth which, like the re-growth following clear felling but containing few economic species, becomes comparatively clear of undergrowth after 3 to 5 years and can be underplanted, line or group planted, and the canopy opened as desirable by poisoning. Areas of forest in which economic species are scarce, or of re-growth where natural regeneration has failed, can be enriched by planting in this manner.
The establishment of plantations in conjunction with agriculture, such as the Burmese taungya system, has met with little success largely due to lack of suitable agricultural methods. The aborigines take one crop only of hill rice, tapioca, etc., and do no cultivation or weedling; other races growing hill rice may twice weed their one crop, and the Chinese vegetable gardener or tapioca grower builds a semi-permanent house and either continues for ever on good land with intensive pig manuring or continues until the land is so degraded or infested with lalang that further cropping is unprofitable.
Between these two extremes there are no agriculturists who follow a system of progressive clearing and cropping for the introduction of tree species in the second or third year crops which would be tended for a year or two before the land is abandoned. Clearings made for one crop are better if underplanted some years later as explained above. Some planting has been done on Chinese vegetable gardens just before abandonment, with uncertain success. If done too late, no further cultivation is done by the gardener and invasion of weeds and lalang is rapid and, if too soon, most of the seedlings die-owing, it has been suggested, to the baleful looks cast upon them by the market gardener! Except where there has been very close supervision. offers of rewards or payments based upon the number of surviving tree seedlings have not resulted in successful co-operation.
Promising exotics
Of the exotics so far tried the following three show grat promise. Albizzia falcata will grow on almost any site excepting pure sand, gives good survival planted as stumped saplings ½ to 1½ inches (1.2 to 3.8 cm.) diameter, is a soil improver and one of the fastest growing trees in the world, reaching a height of 80 feet (24 m.) and a girth of 4½ feet (1.4 m.) in five years. The wood is soft and weak by local standards but is used for matches and has possibilities for paper pulp. The Honduras mahogany (Swietenia macrophylla) was planted as long ago as 1876 and has grown well on good and poor sites. Seedlings are easy to raise and planting survival usually good. Eucalyptus deglupta is another very fast growing exotic, producing a fair quality timber which has reached 76 inches (23 m.) girth and 105 feet (32 m.) in height in 10 years. Seed is extremely small and seedlings very liable to damping-off unless transplanted from seed pans to seed boxes when at 2 leaf stage. Seed of all these species is regularly available.
After five years of distinguished service with FAO, D. Roy Cameron has relinquished the appointment of Chief Technical Assistance Officer, Forestry. He has been concerned with FAO and its Forestry Division since the Organization was first founded. Joining the staff in 1947 after being Dominion Forester, Canada, Mr. Cameron headed the European Office of the Forestry Division at Geneva for three years, serving also with great success as Director of the Timber Division of the United Nations Economic Commission for Europe. After FAO Headquarters moved from Washington to Rome, Mr. Cameron assumed charge of forestry activities under the Expanded Technical Assistance Program.
P. Terver, who for the past three years has been Chief of the FAO Regional Office in Rio de Janeiro, has taken over the post vacated by Mr. Cameron.
W. R. Chapline, Chief, Division of Range Research, Forest Service, U. S. Department of Agriculture, has been appointed as a Chief of Section within the Forest Policy Branch.
S. von der Recke, Deputy Chief of the Forest Service of the German Federal Republic, has been assigned to head the Latin American forestry working group.
S.A. Vahid, lately Inspector-General of Forestry, Pakistan, has taken up the appointment of regional forestry officer for the Near East.
