D.A.N. CROMER
ASSUMING that it is in the interests of national economy to proceed with an afforestation program, and that there are no insuperable difficulties in choosing appropriate species or silvicultural methods for establishing a man-made resource, this chapter wild consider the management aspects of such an undertaking, which is of considerable magnitude. The term "management" will be used both in its broad sense of organizational planning and managerial obligation, and in the strict sense of forest management to cover the growth, yield, and protection of forests from destructive agencies.
In preparing this chapter the Senior Rapporteur has drawn on some of the papers presented to the Sixth. World Forestry Congress in Madrid in 1966 and also on the joint FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects held in Oxford. in 1964. Selected papers from these and other sources have been used to augment the papers presented to the present symposium, as required.
The higher echelons of planning relate to those aspects of policy considered in Chapter 1 - the potential. role of manmade forests, and their relationship to the national economy.
Grayson (1967) has emphasized that national policy decisions may be explicit, but are more likely to be only partly explicit or even implicit in the policy objectives of the responsible agency. Where national policy is not explicit the forest authority has the responsibility for determining what government attitude should be and the means of mobilizing resources.
In South Africa (Anon., 1966) the establishment of manmade forests was dictated by an inadequate supply of natural timber and the unorganized exploitation and destruction of the resources which did exist. On the other hand, New Zealand (Maplesden, 1966) was originally largely covered with natural forests of varied conifers and evergreen hardwoods. Exploitation and devastation, however, followed the familiar pattern, until an expected shortage of timber for local consumption called a halt and led. to the establishment of manmade forests. It is noteworthy that none of the indigenous species was employed. It appears likely that in both of these examples the national decisions were not explicit, but flowed from lower levels.
Maplesden (1966) has drawn attention, however, to the setting up of a planning section within the Forest Service which in consultation with the New Zealand treasury has formulated a specific policy to afforest an additional million acres by the year 2000, and which has received government approval and support. This decision undoubtedly stems from the financial success of the first million acres of plantations, their demonstrated growth rates, and the availability of an export market. Developing countries considering an afforestation program would not be favorably placed to make a clear-cut decision and would be faced with a number of assumptions and "best available" estimates.
Grayson (1967) has suggested that it is undesirable to state the objective in terms of the area of forest estate desired, whereas the important statement is the rate at which planting should proceed, so that this activity can be aligned with factors upon which it is dependent, such as labor, housing, etc. The expansion of the Australian planting program was expressed in terms of a rate per year (Fairbairn, 1966) after consultation with the States on their attainable objectives in terms of available land and capacity to implement the programs proposed.
It is important that the contribution which forest industrial companies and private landowners can make is not overlooked, as this can be considerable (Stevenson, 1966). In Brazil Krug (1967) states that it was always assumed that most of the future plantations would be made by private growers, but large government plantations were necessary to demonstrate that exotic conifers could be grown successfully to replace the indigenous Araucaria angustifolia.
Once the general policy decision has been taken, a second planning function comes into play, which "has to translate these aims and means into specific internal management guides" and which Grayson (1967) has termed management planning. The two kinds of planning are to some extent interwoven because unless they are so, a policy decision may imply unfeasible practices.
The policy decision discussed above may have been based on a detailed economic analysis, but (especially in developing countries) it is more likely that it has not, consequently the next step is the consideration of the various alternatives which may be employed to attain the policy objectives.
Firstly, it will be necessary to collect available basic data: climatic, edaphic, growth, yields, prices, etc., and subject these to critical analysis. In many cases information will be either lacking, in which case assumptions will have to be made, or inadequate, when reasonable estimates will have to suffice. Cost/benefit analyses are being used more and more to assist in the making of effective decisions (Webster and Marty, 1966) in spite of the limitations of the method. Such analyses are useful when comparing alternatives solely related to financial investments, e.g., rotation lengths, but are less useful when considering the indirect benefits of a forest of an intangible nature such as recreational values, stream flow regulation and other nonmarket determined values. Webster and Marty suggest economic reasoning may be extremely useful to supplement economic analysis.
With the advent of the computer has come the development of a whole series of new approaches in management planning collectively known as operational research. Within this term mathematical models may be set up (Jeffers, 1966), of which linear programming (Wardle, 1966) is a special case. The technique of simulation may be used to characterize the real problem by a theoretical one. Makower (1966) has pointed Out with respect to mathematical programming that: "Perhaps even more important than the calculation of an optimal solution is the ability to test quite easily how sensitive the solution is to changes of various kinds."
MacConnen et al. (1966) have described a computer-oriented system for processing and analyzing information, using the technique of linear programming, as an aid to the decision maker. They point out the desirability of updating resource inventory information and periodic re-use, since planning should be a continuous process.
The difficulties for developing countries in making use of these modern methods as aids to decision making should not be overlooked, especially as rapid developments are still taking place.
Whether a developing country will be able to avail itself of the techniques of cost/benefit analysis and operational research will depend on its ability to accomplish these from within its own resources or by the engagement of outside experts, and the timing of either of these alternatives. This is not to say that an evaluation should not be attempted without the benefit of such tools. Probably the great majority of man-made forests were established without any such aids to the decision maker. Their greatest value lies, perhaps, (as indicated above) in the rapid testing of various alternative approaches once the input data have been collected or estimated.
The necessity for flexibility has been stressed by Grayson (1967) so that adjustments to changed circumstances may be readily incorporated into the program. The original concept of the working plan being a rigid document has fallen into discard, and management, plans are now brief, to the point and subject to periodic review.
Two important considerations which must figure prominently in management planning are location and size. The transport components both before and after processing vitally affect the value of forest products, because timber is a heavy and bulky commodity. Extraction costs are greatly influenced by topography, as also are most other management costs. In consequence, Forestation programs should aim at land of workable topography even if the cost of the land is higher (Maples den, 1966), located advantageously with respect to markets or industries (if the latter already exist). A. satisfactory compromise between site quality and work able topography might well be the desirable goal.
With respect to size, Maplesden suggests an area oft not less than 150,000 acres (60,000 hectares) of Pinus radiata for a major integrated industry, and ] 0,000 acres (4,000 hectares) for local-supply forests. There is a second school of thought which considers these estimates too high and that they should be flexible and relate to the state of development of the country concerned.
If they have been realistic management planning considerations, whether based on judgment or operational research, will have taken into account labor and equipment requirements and will therefore generate operational plans.
It is not possible to generalize on these questions, for the answers will depend on the social structure of a given country, its present economic situation, and the availability of skilled and unskilled labor. It can be stated, however, that in developing countries an afforestation program can be a highly labor-intensive activity, with a consequent requirement for skilled supervision (Grayson, 1967), and experienced technical staff. On the other hand it can be accomplished with a minimum amount of manual labor and a high mechanical equipment component. Only if skilled operators and adequate repair and maintenance facilities are available should the latter course be contemplated.
In cases where plantation schemes are labor-intensive and the cost of labor is high, productivity of labor assumes considerable importance; consequently work studies, though not common in plantation projects, might well be undertaken with a view to increasing efficiency.
The problem of road construction is of particular concern in plantation establishment and is bound up with the extraction of thinnings and the harvesting of the final crop, as well as the more immediate question of access for planting, tending and protection.
Experience has shown that the initial construction of only essential roads at, establishment is false economy (Anon., 1966). In South Africa a complete logging road system is planned in advance of establishment having regard to the anticipated volume of timber to be extracted, the method of logging and the type of equipment likely to be used, site quality and topography. A system so designed is found to be normally adequate for all management and protection purposes.
The social pattern for forest workers and technical staff has undergone a radical change, especially in the developed countries with relatively full employment and rising standards of living. Forest workers are no longer content to live in isolation in very small forest communities lacking the amenities available to larger centers. Planning afforestation schemes must therefore take into account the necessity for providing not only housing, but centers of reasonable size, with provision for schools, medical care, recreational and other facilities. As a corollary to such centralization, provision also has to be made for the transport of workers to and from the forest and industrial plants.
It is of course important that the matters covered in Chapter II - choice of species, seed selection, and appropriate tending practices - should be incorporated in management planning and organizational schedules at the project level.
The consideration of purely protection forests and shelterbelts has been omitted, as it was felt that these would be adequately covered in other chapters. Nevertheless they do require management of very specific kinds and are no less difficult to organize and prescribe for than production forests.
More often than not man-made forests are established with exotic species about which little or only limited information is available on growth rates under the conditions obtaining in the new habitat. It is almost certain that the desirable rotation and the yield obtainable will be unknown quantities, except that informed estimates may be made based on the behavior of a given species elsewhere under similar conditions (Bunn, 1967).
The early stages of the project will consist almost entirely of establishing annual areas, and it is usually not until the first compartments are reaching minimum merchantable size that attention is turned to mensuration, and to consideration of growth and yield. It is logical that the determination of rotation length should be left open as long as possible, meanwhile concentrating on the measurement of standing volume and increment.
Fenton (1967) discussed the various kinds of rotation which might be adopted (e.g., physical, financial) and deplores the fact that data for enabling optimum decisions to be made with respect to man-made forests are not being adequately accumulated. The lack of accurate data on costs, and of reliable price gradients for size and quality of end products at present leads to difficulty in determining optimum rotations.
Growing stock can be determined by a once-only inventory, and increment in addition by periodic reinventory, but the consensus of opinion is that the modern forms of continuous inventory are by far the best approach in a situation which is constantly changing. Although it is desirable to be precise about the objects of an inventory, this should not be at the expense of narrowing down the data collected.
Precise details of increment in various assortments can only be obtained by the establishment and remeasurement of permanent sample plots over a period of years, although approximations for previous periods may be deduced from increment borings and analysis. Useful data can also be obtained from temporary plots with greater ease and less cost.
Examples of specific growth data have been presented by Webb (1967) for E. regnans in Australia, by Gemignani (1967) and by Valenziano and Scaramuzzi (1967) for eucalypts in Italy, by Groulez (1967) for a species of Eucalyptus locally known as 12 ABL in the Congo, by Bauger (1967) for Norway and Sitka spruce in comparable plantations in Norway, and by Giordano (1967) on the growth and technological characteristics of Araucaria angustifolia of value in making an economic assessment. Eccher (1967) found that P. radiata growing in Italy under particularly favorable conditions of soil temperature and precipitation can develop uninterruptedly throughout the year with a growth rate variable from month to month according to daylight hours. This confirms Australian experience with this species in similar conditions.
Wright (1967) has described the combination of permanent and temporary plots to form the basis of a continuous inventory program in which stratified random sampling is employed to provide information with respect to site, age, species, etc. The question of whether sampling within strata should be random or systematic is still being debated. However, both systems will provide an adequate estimate, but the error calculated from random sampling can be stated with statistical confidence.
There is ample coverage in the literature on the number of plots required for a given level of precision, on the detailed techniques for the establishment and measurement of permanent sample plots, and on methods of measuring temporary plots. In the latter connection no country can afford to neglect the advantages of the Bitterlich method, also called the angle-count or variable-radius method, for rapid inventory work especially in unthinned or Lightly thinned plantations
Wright also discussed the linking of continuous inventory with electronic data processing which, even if access to a computer is not immediately available, should be recorded in such a manner that it can be so processed at a later stage. Rather than involve them selves in costly expenditure for computer installations which are improving rapidly, developing countries should consider buying time from computer service bureaus and rely on advice for programs and techniques. Various programs for this purpose have been described in detail by a number of authors. In this context mark-sense cards should be viewed with caution by developing countries as they leave room for errors which cannot be checked, and a less sophisticated approach is suggested. For developed countries newer techniques becoming available in the form of map readers are worthy of consideration.
It must be borne in mind that before the stratified data collected can be translated into volumes, the areas covered by the various strata will be required. If the planted areas have not been mapped by conventional survey methods, or if changes in stand structure have occurred subsequent to the survey, and the total area is large enough to warrant it, recourse may be had to aerial survey and photogrammetric mapping for the determination of areas in the various categories.
A further requirement is the preparation of volume tables and stand volume tables for an initial inventory, or the refinement of existing tables as more data become available. Here again there are a variety of documented methods from which to choose and appropriate formulas for linear and multiple regression analyses by ma chine calculation or computer as available.
The continuous inventory approach as briefly sketched above will provide all necessary information on growing stock and increment. When sufficient remeasurements have been carried out, and provided the permanent plots have received the same treatment as the remainder of the stand, it will be possible to predict yields, both intermediate and total.
An urgent need exists however for a suitable definition of site index, and a method of indicating this which would prove internationally acceptable. Whether height alone is adequate is under question, and even so the present differing measures of height used between and within countries prevent the making of meaningful comparisons.
Stiell (1967) indicates a high correlation in certain species between volume per acre and stocking combined with either dominant height or average diameter. This has been suggested as a suitable vehicle for the use of aerial photography, but the measurement of tree height from air photography at the usual scales employed may not be precise enough for this purpose.
However, in the general use of aerial photography recent Australian investigations (Sims and Benson, 1967), of the true-color aero-negative system suggest that this medium may prove more informative and not very much more expensive than conventional black and white film for the assessment of stand condition, etc. The techniques of filtering during the printing process suggest that the difficulties previously experienced with blue haze in true-colored photography from higher altitudes may be effectively overcome.
Bunn (1967) has stressed the versatility desirable in a prediction method which is provided by the variable density yield tables. Normal yield tables assume full stocking and adherence to a rigid thinning regime, and must be discounted for departures therefrom. In actual fact stocking is rarely "full" (as those who have tried to locate fully stocked stands in which to establish such yield plots are well aware) and outside pressures, not the prescription, frequently determine when thinnings are carried out. In view of this situation it is realistic to use a variable-density method.
This question is largely a specific problem in the general field of forest nutrition which has been discussed in Chapter II. There has always been speculation whether a given site can maintain the same yield indefinitely, especially with short rotations. It has recently become fashionable to use the agricultural approach and measure the total dry matter production in terms of wood, bark, twigs and leaves (Ovington and Madgwick, 1958, 1959; Orman and Will, 1960; Young et al., 1965; Young, 1966). A balance sheet is then drawn up to show the total amount of nutrients removed from the site (e.g., in wood and bark) and returned to the floor (twigs and leaves), compared with the nutrient levels available from the soil. A good deal of research effort is being mounted to follow the course of litter breakdown, because there is no doubt that large quantities of nutrients are removed from the site and it is difficult to understand how infertile forest soils at any rate can sustain such a withdrawal.
Maki (1966), in an excellent review paper on forest fertilization, tabulates a few typical examples of nutrient drain reported since 1890. He points out that the real gap in our knowledge is specific data on the rates of nutrient replenishment. While this situation exists our balance sheets will be incomplete and conjectural.
There is ample evidence throughout a large volume of literature that the application of fertilizers can increase production of established stands, increase growth at establishment, ameliorate harsh sites, and improve production on peat soils. Whether the response to fertilization at establishment is sufficient to carry the cost of the operation throughout the rotation is less clear, but certainly the application of fertilizers toward the end of the rotation would not suffer from this disadvantage Several authors have described commercial operations in Scandinavia where the application of urea is under way on areas as large as 100,000 acres (40,000 hectares). Swan (1966) has pointed out the need for accurate diagnosis of nutrient deficiencies as a prerequisite to such action, and has suggested that the bioassay method has considerable merit.
One would expect that short rotation crops would be the first to show evidence of any deterioration in site productivity. However, in South Africa (Anon., 1966) there has so far been no indication of soil deterioration, but it must be borne in mind that the soils planted are of adequate depth and fertility.
Australian forest soils are in general of low fertility, and it was in South Australia, where Pinus radiata has been planted on coastal sands, that a drop in site quality of the second rotation crop was first reported (Keeves, 1966). Although research has not yet provided the answers to this problem, it is probable that fertilization of some kind, and at some particular stage, will be required to sustain first rotation productivity.
Waring (1967) has reviewed the role of nitrogen in maintaining productivity, and pointed out that the nitrogen level is linked with the soil organic matter.
Any practices which reduce the organic matter will therefore have a deleterious effect on the nitrogen equilibrium, and thus the soil fertility.
It has been the practice in Australia to burn the slash after felling the first crop, and to the resultant loss of organic matter has been attributed the drop in productivity of the second rotation. Nevertheless, in New Zealand where the slash is not burnt, Stone and Will (1965) found nitrogen deficiency in second rotation plantations of P. radiata.
As Waring has emphasized, his own research both in field experiments and pot trials, in common with many other investigators, has demonstrated a positive interaction between nitrogen and phosphate. Even with small seedlings Van Den Driessche and Wareing (1966) reported "the phosphorus requirement of P. radiata for optimal growth was lower than that of P. contorta and P. nigra, although it increased with rise in nitrogen supply."
The possibility of using legumes to increase the nitrogen level in the soil should be kept in mind, and trials initiated on forest soils of low fertility of applying fertilizers toward the end of a rotation, not only to increase the production of the current; crop, but to determine the effect on the crop to be re-established
It is apparent that a co-ordinated research effort is needed to provide the answers to this problem, which is likely to vary greatly from place to place and in consequence to preclude any appropriate generalization.
It is obvious that detailed records of expenditure, yields and revenue must be maintained, for every business venture (of which a man-made forest is an example) must report to its shareholders, directors or government. Only by analyzing such records is it possible to make appropriate management decisions as to future action, and to assess the profitability of the enterprise.
Some consideration must be given to the kinds of records which should be kept, the operating system to be employed, and the units on which the records will be based, bearing in mind that the clerical work involved will be of considerable magnitude, whence essential and relevant information only should be recorded.
One school of thought considers that records in the past have been overdetailed, time consuming, and preserve antiquated rather than current data. Obviously, the simpler the records can be, the better available the information is for reference in the future when required. The tabular form also is frequently criticized on the above grounds; nevertheless the value of having list of all necessary headings to obviate the omission of pertinent data is recognized (Endsjo, 1967).
FIGURE 45. - 4 row of Populus thevestina acting as windbreak near Oriashoro, Bulgaria. (CASTELLANI)
Wendelken (1967) has distinguished between physical records and stand records, and for both of these maps are required, to be read. in conjunction with the tabular and written information. The physical records describe the land itself, its topography, soil, aspect, elevation and vegetation. It is most important that prior to the clearing of existing vegetation for plantation establishment the ecological situation be adequately described, because such information cannot subsequently be retrieved, and may hold the key to the selection of future planting sites.
Stand records cover all the operations involved in establishing the stand, its maintenance and subsequent treatment, including its growth and yield. Such records are therefore not static but must be continually updated as the stand ages, as treatments are applied, or as external factors influence growth, or when intermediate yields are extracted.
Traditionally, the basic unit for record purposes has been the compartment, although the viewpoint as to what a compartment should comprise has varied somewhat. Indeed, the very concept of a fixed compartment unit has been challenged. Modern principles for delineating compartments have been set down by Wendelken (1967), not the least important of which is that wherever possible they should be bounded by recognizable physical features.
When a compartment is of comparatively large size it is unlikely that its quality will be uniform throughout; consequently it will probably require to be split into two or more subcompartments so that average growth and yield data can be applied to these individual subdivisions. Under extreme conditions a change of species is sometimes necessary within a compartment, and this obviously must involve a breakdown of the recording unit.
From the compartment/subcompartment maps forming an integral part of the recording process, schedules of areas can be prepared, giving details of the growing stock by species, age, density, etc. Later, when the plantation becomes old enough for an assessment to be meaningful, a schedule of site qualities can be predicted and cutting plans formulated.
Simultaneously, from the area schedules and the stand records the cost structure may be examined. Unit costs have a dual role in assessing the efficiency of an operation (compared with other compartments and other years) as well as forming the basis for budgetary control of future operations.
The physical maintenance of manual forest records is best achieved by a loose-leaf system providing visible indexing and summaries for the ready retrieval of data. Modern business systems are readily available for this purpose and the matter requires no further elaboration.
The use of computers and data processing systems has made enormous strides in recent years in both the scientific and business fields. In forestry, the analysis of experimental data, the conduct of inventories, the use of mathematical models, and multiple regression analyses have formed the bulk of the computer techniques employed to date. Benefit/cost analyses are commencing to be used, log sales and salaries have been computerized, but so far little attention appears to have been given to placing plantation records on a data processing basis. Perhaps this is because it is more akin to updating stock records in a commodity business enterprise, and would involve the marriage of the commercial-type computer with the scientific approach. This is a field of research which would benefit all countries concerned with man-made forests.
The question of expenditure and revenue accounts and the units which should be adopted has been adequately covered by Wendelken (1967), and it will probably suffice to reiterate that the following items of expenditure need to be recognized:
1. direct expenditure on the crop itself
2. capital improvements (roads, buildings, etc.)
3. maintenance (including protection)
4. administrative charges, plant and overheads
5. utilization costs.
The difficulty of comparing the costs of production and various cost components for different countries is pointed out by Endsjo (1967) and exemplified in the case studies presented.
The necessity for complete, accurate and current data to enable immediate decisions to be taken in the highly competitive world of today is especially relevant in the private sector of productive forestry.
It has become apparent that a uniform costing system for forestry is needed to supply the comparative economic data required for economic analysis as a basis for the selection of viable projects.
DISEASES
The present symposium is fortunate in having as background the documentation of the joint FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects held in 1964, when the question of the establishment of test plantings of tree species with respect to disease resistance and susceptibility was raised (Murray, 1964). The proposal to do so thoughout the world has been variously supported since 1949, but it appears that the difficulties of carrying out such a scheme and the disadvantages attaching to it outweigh the advantages.
In considering the weaknesses of disease susceptibility plantations, and especially the long period of waiting before results accrue, Hepting (1964) suggested an alternative approach, in which phase 1 involves preparing INTREDIS (an international tree disease information register) and phase 2 consists of a hazard appraisal - prediction method (coded APPRE) - for a given region with respect to possible pathogens. INTREDIS would be organized on an information retrieval electronic data processing system so that APPRE appreciations could be readily carried out. The value of the proposal is that the method could be used immediately the register is prepared, and continually updated as additional information comes to hand.
From the point of view of man-made forests it is necessary to know how the effect of diseases can be minimized, what preventative measures can be taken to keep diseases out or hold them to an acceptable level, and whether it is reasonable to take calculated risks in long-term projects of this nature.
Attention is drawn to the danger of introducing disease with mycorrhizal soil. It is possible to prepare and distribute pure cultures of suitable fungi, and this has been done in some instances (a general study of mycorrhiza is currently being supported by FAO under its André Mayer Fellowships Program).
In textbooks and throughout the literature on the subject, a warning is continually being sounded about the danger of epidemic outbreaks of fungal diseases (and insect pests) in monocultures and plantations generally (Foster, 1964; Shaw, 1964; Gibson, 1964; Imazeki, 1964; Bakshi, 1967). Maplesden (1966) stated: "The inherent risk of disease and insect attack is so great that some diversification of species, even at the expense of yield, is essential to maintain forest hygiene." For this reason P. radiata will not be allowed to exceed 60 percent in New Zealand.
Many such statements are supported by examples but often they are qualified by explanations that the particular species was planted on a poor site, or out of its climate range, or subject to unusual meteorological conditions, or was unthrifty for some other reason. For example Imazeki quotes the spread of shoot blight, (Guignardia laricina) over 100,000 hectares of Japanese larch planted outside its natural habitat in Japan.
There is no doubt whatever that species (whether exotic or not) grown in plantation under adverse conditions will be mole susceptible to disease and that stand vigor is important in warding off diseases (Bakshi, 1967). It is important therefore in planning an afforestation program to resist the usual tendency to push forestry projects onto land unsuitable for anything else.
It is considered, however, that a closer look should be taken at the vulnerability of man-made forests to disease, on reasonable sites and with reasonable maintenance. Pathologists will throw up their hands in horror at the suggestion, and it is agreed that the arguments put forward are logical and convincing. That they are not borne out in practice merits further study: it cannot be that most countries have been "lucky."
To quote Luckhoff (1964): "The forest industry in South Africa is based almost entirely on pure, even-aged plantations of exotics which cover an area of more than two million acres (800,000 hectares). A feature...is the relative freedom of these plantations from serious disease outbreaks. Diseases cause an estimated annual production loss of only ED fraction of one percent. Australia, with a plantation area approaching 750,000 acres (300,000 hectares), is in a similar position, in spite of the presence of Phytophthora, Fomes, Armillaria, Diplodia, Lophodermium, etc. Likewise the exotic forests of New Zealand have not shown signs of serious diseases (Newhook, 1964) until the recent outbreak of Dothistroma pini which has not yet been fully evaluated.
Eucalypts have been planted in many countries of the world, in extremes of climate, rainfall, and soil conditions, on an area in excess of 5 million acres. In the British Commonwealth "no fungal disease has caused general damage, and the occurrence of gummosis, canker, and dieback seem to be related to unfavourable growing conditions rather than specific diseases." (Streets, 1962). The situation appears to be similar in other countries.
One can take comfort also from the close parallel of the large rubber monoculture in Malaysia where, in spite of Fomes lignosus, Ganoderma sp., and Phytophthora, the plantations continue to flourish under the watchful eye of the Rubber Research Institute.
GREATER DISEASE INCIDENCE IN MAN-MADE FORESTS
Although the writer is well aware that the natural forests of the world cover many times the area of manmade forests it is significant that most of the serious diseases, whether introduced or endemic, affect natural forests and/or isolated trees in their natural habitats, (e.g. the blister rusts, chestnut blight, Dutch elm disease, littleleaf disease, heart rots, Douglas fir root rot). The losses in natural stands are enormous (Davidson and Buchanan, 1964) and the impact on man-made forests cannot be less. It is the net effect which must be taken into account, and adequate protection measures must be taken III both cases.
Sometimes a closer look points up the true position. As Fomes annosus is considered a major threat to plantations in the United States of America, Bega et al. (1966) carried out a root disease survey in a Californian natural forest area. The fungus was spread throughout the forest and the authors concluded it is a much greater menace than past reports would indicate.
Man-made forests, like natural shade, are going to be afflicted with fungal pathogens whether we like it or not, and in spite of stringent quarantine precautions to prevent the entry of exotic diseases, such pests appear likely to spread to all countries. In consequence one must be constantly on the alert to the seriousness of the problem, firstly with respect to choice of site and species (Bakshi, 1967), secondly with regard to detection and evaluation, and later the application of adequate control measures, while at the same time mounting a continuing dynamic research program (Benedict, 1964). Quraishi (1967) describes the fungal pathogens of Dalbergia sissoo in irrigated plantations and suggests alternation of crops so that host material will not be available, and the pathogens will thus be eliminated.
A considerable effort has been directed at selecting and reproducing disease-resistant clones, especially of poplars. That many clones have had to be abandoned in the face of the onset of a new disease points to the need for further study of disease resistance.
INSECTS
The situation with respect to insects in relation to man-made forests is very similar to that of diseases, and in fact they are often coupled together in discussion.
Benedict (1966) has summed up the position as follows: "It is important to bear in mind that diseases and insects will be with us always. The fact that they are a natural component of the forest environment - as much as the trees - is not as yet well understood.... [Foresters] often fail to realize that an all-out attack upon every pathogen or insect that occurs in the forest would not only be needless and unwise, but would place a staggering demand upon facilities and funds.... Except in an eradication campaign where the objective is to find and destroy the last disease spore or insect - a situation rarely encountered in forest pest control - the only feasible approach against disease and insects is to reduce outbreaks to a level where natural controls will hold them in check."
The spread of forest insects, both be Fore and after the institution of quarantine measures, has been described by Simmonds (1964). All authors on this subject agree that international co-operation is absolutely essential to minimize the spread of insect pests, and disseminate research information. There is need also for improved techniques to quantify the impact of insects and diseases upon increment so that the expenditure which might be warranted upon control measures can be gauged.
The catastrophic damage which can be done by one insect epidemic has been described by Beal (1964). The southern pine beetle (Dendroctonus frontalis) spread over at least 5 million acres (2 million hectares) of natural pine forest in Honduras destroying more than 8,000 million board feet of high quality timber. The epidemic was too large - 100-mile (160-kilometer) front - and moved too rapidly (100,000 new trees attacked per day) for any effective control measures to be taken, even if the know-how had been available.
Control of a forest insect pest almost always depends on knowledge of its life history, behavior, conditions favorable to its development, and its parasites and predators. When adequate information is not available, expensive eradication and containment campaigns have to be mounted while research is undertaken, for example with Sirex noctilio on P. radiata plantations in Australia (Cromer, 1966).
Apart from small areas such as forest nurseries, chemical control of forest insects is usually regarded as an emergency method only. Wholesale aerial spraying of insecticides carries with it all the dangers of upsetting the balance of nature, contamination, toxic residues, and so forth. Parasites and predators are often killed at the same time as the pest, which may lead to reinfestation at an increased :level in subsequent years. Added to this, the development of insecticidal resistance is very real.
Nevertheless Torrent and Romanyk (] 967) stress emphatically that there should be no hesitation in using chemical methods as an essential weapon when circumstances dictate. Pesticides are too valuable to be dismissed lightly, and should be regarded as one available tool to be used in conjunction with biological and other methods after careful e valuation of the situation.
In many instances the physical application of chemicals is difficult or impossible, and attention has to be turned to alternative methods. Biological control using insect parasites has been a classical approach for a long period, but more recently disease-causing micro-organisms have been utilized (Franz, 1966; de Bellis and Cavalcaselle, 1967). Franz also discusses generic manipulation or autocidal control, i.e., "the destruction of a population through its own activity." Several examples of control by the release of males sterilized by gamma radiation have been reported. In quoting the advantages of the method Franz states: "The self-destruction of a population may end Up with eradication, whereas all other biological control methods at best create a new and very low level of the pest that has to continue if the regulation is to persist."
Franz has also pointed out what he calls "biotechnical" control, i.e., the use of sex or other attractants with or without chemosterilants, as another method with promise, but recommends that integrated programs be developed using complementary methods to give optimum effectiveness.
Attention is drawn to several organizations which cover the field of biological control, which countries with insect problems may consult, and which sponsor the collection of parasites and the like, as required.
Torrent and Romanyk (1967) emphasize (as with diseases) that adverse conditions predispose forests to insect attack and that adequate silvicultural treatment is essential together with appropriate forest hygiene if pests are to be kept to a minimum.
There are several cases of indigenous species which cannot be successfully grown in man-made forests at present because of wholesale insect attack, e.g., Chlorophora excelsa in Nigeria, Cedrela and Agathis in Australia.
On the other hand, an exotic species is occasionally subject to severe attack, e.g., eucalypt plantations in Tunisia by the wood borer (Phoracantha semipunctata).
Almost all authors dealing with forest insect problems stress the need for more research so that life histories and behavior of dangerous or potentially dangerous species can be studied and control methods determined. The new techniques of labeling with radioisotopes to follow rate of spread and behavior are already being used in some centers (Jahn and Weidinger, 1966). There is need also for more research into pesticides, particularly the possibility of using a smaller number.
he intensification of forest insect and disease research in developing countries could perhaps be met by the establishment of regional research institutes, of which the East African Agriculture and Forestry Research Organization (EAAFRO) is an excellent example.
It is considered a sound investment for countries with man-made forests (or contemplating their establishment) to budget, as the barest minimum, for an insect survey team, so that population build-up can be detected in the early stages.
WILDLIFE
An adequate appreciation of the position with respect to wildlife has been presented by Holloway (1967), who indicated that damage is largely restricted to browsing and barking, since soil erosion from trampling is mainly confined to indigenous forests, as also are seed losses by birds and rodents.
Certain geographic regions have special problems arising from the indigenous fauna (elephants in Africa, opossums in Australia) but in general the most damage is caused by mammals having a worldwide distribution, and falling into three groups: rodents, rabbits and hares, and. artiodactyls (deer, antelope, pig and buffalo).
Browsing is serious on young trees when the apical shoot is within reach. Barking, in addition to causing local defect and loss of increment, allows the entry of insects and fungal pests. With climbing animals this can occur in the upper crown of older trees, as well as at the base of young trees. The multiplication of animals is encouraged in young plantations by the cover afforded and the food supplies provided, thereby increasing the concentration of animals at the most vulnerable stage in the life of plantations. The situation may worsen as the percentage of man-made forests in relation to natural forests increases.
Empirical protection methods which have been used in the past comprise fencing, shooting, poisoning, trapping and fumigation. A good deal of research is still being applied to repellents, some of which are now showing promise. Permanent fencing is expensive, and temporary fences are frequently used for a short term, and re-erected round a subsequent planting at a later date. These methods are remedial and preventive, and are likely to continue while large-scale afforestation is under way.
Holloway, however, considers that the ecological approach will assume greater prominence in the future. This method involves the management of the wildlife populations and the forest habitat as interdependent parts of the whole, so as to minimize damage. The population management approach would appear to be more appropriate to the larger hunted animals than to rats or rabbits.
No consideration of animal damage in Australia would be complete without mention of the significant reduction in the rate bit population through the use of the virus myxomatosis.
Ratcliffe (1961) summed up the situation as follows: "Myxomatosis is now entrenched in the wild rabbit population as a self-perpetuating infection that flares up, locally or regionally, when conditions for its rapid transmission and spread become favourable. The disease has had an almost unbelievable effect on rabbit numbers, and over huge areas has taken the urgency and seriousness out of the rabbit problem. The virus is still killing, cutting back infestations in many places before they can build up to a high level. Present indications are that the disease, working naturally and spontaneously, will continue to be a most important rabbit-killing factor for many years to come. But a natural resistance is building up in wild rabbits, permitting an increasing percentage of recoveries. This makes it certain that the overall effects of myxomatosis will diminish with time; but no one can estimate the speed of this change." There are, of course, other effects in a vector-transmitted virus of this kind.
Australia is also faced with a difficulty in securing seed of Pinus pinaster from locally grown trees because of the destruction of tire cones by cockatoos. These and other heavy birds also break off the leading shoots of Pinus spp. during the period of elongation when they are brittle and' cannot tolerate the birds alighting on them.
FIRE
Fire protection is a most important, component of forestry operations in regions of winter rainfall and high summer temperatures, and to a lesser degree elsewhere. It is costly both in the preventive and suppression stages. In natural stands the difficulties of access, undergrowth, etc., accentuate the position, but in man-made forests fire prevention measures must be "built-in" from the beginning, to the extent warranted by the climatic conditions and factors of the locality.
McArthur (1967) has provided an appropriate appreciation of the levels of protection required, and the planning necessary to achieve them so as to remain within the limits of acceptable losses. He points out that plantation crops have certain advantages over natural stands, e.g., lower wind velocities due to denser stocking. The intensity of fire protection for man-made forests must be related to the costs and values involved and must recognize the principle of diminishing returns. Maximum use should be made of grazing and other uses which can profitably benefit fire protection by reduction of hazard and thereby reduce protection outlay.
The wide variation in the level of protection required between countries according to their fire climates is also pointed out by McArthur, who stresses that one of the major variables controlling fire behavior is the quantity of fuel which has accumulated. The reduction of this hazard is recommended either by removal, burning, or mechanical disintegration. The first two, however, remove the litter and slash from the site and, as discussed in an earlier section, may contribute to site deterioration. It is established that burning of litter may be carried out in plantations at an appropriate time without visible damage, even to fire-sensitive species. It remains for research already initiated to determine whether the practice is deleterious to the fertility of the site and/or to the soil micro fauna and flora.
The design of firebreaks has undergone considerable changes over the years as a result of experience. The wide breaks provided earlier, which were supposed to stop a fire, have now been reduced to narrow dimensions, primarily for access rather than as a fire check. The design of an adequate firebreak system depends largely on the fire climate and fire conditions of the country concerned. The planting of noninflammable (or rather, less inflammable) species along the edges of firebreaks is practiced in some countries, e.g., Sweetia brachystachya in the lower Congo. The search for suitable species for this purpose is continuing. A given species may be inflammable in one country and yet serve as a firebreak species in another, for example eucalyptus.
Loss of productivity resulting from a system of wide firebreaks can assume significant proportions, especially when suitable planting land is in short supply or is expensive. In many cases previous firebreaks have been planted up; or reduced to access tracks. Although any type of break is not generally effective in stopping a head fire, such access tracks are usually effective in preventing lateral spread, and at the same time serve as firelines from which control can be initiated. McArthur (1967) has also pointed out that any reduction in the cost of maintenance will have a significant effect upon the profitability of the enterprise.
The location of the man-made forest in relation to the center of utilization will have an important bearing on acceptable losses, as will the question of whether or not the forest is insured wholly or partly against loss by fire. Under these circumstances the acceptable annual fire loss percentage could well be as high as 0.3 to 0.5 percent without causing undue worry to the forest owner. It has been suggested by McArthur (1967) that the criterion for the level of acceptable loss might be the ability of industry to utilize (without undue disruption) fire-killed timber before degrade sets in. However the acceptable figure is arrived at, planning of preventive measures, manpower, equipment and suppression methods, etc., must evolve around it. The disposition of these resources and their readiness for employment on suppression activities need to be governed by a fire danger rating system (McArthur 1963) which integrates the various factors involved, and from which the forces and facilities needed to cope with the predicted rate of spread and difficulty of control can be determined, and marshaled for immediate action.
The fire danger rating system must be associated with fire weather forecasts, so that placement of crews to the appropriate level of preparedness can be organized. Such forecasts need not be internal only, but can be arranged through broadcasting/television channels, where they have an impact on the general public. Fire prevention campaigns must be well designed and supported by adequate publicity through press, radio and television.
The next phase in the fire protection picture is detection, and in the intensive management of plantation forestry this is more readily accomplished than with extensive indigenous forests. Fire towers and communication equipment have been adequately described in the past, and no difficulty should be experienced in providing an appropriate system. New approaches, however, are being developed with infrared detectors and image converters (Packham, 1966).
Actual suppression methods and the equipment used will depend on the fire climate, the seasonal conditions experienced, the topography and the social situation of the country in question. Hand tools may suffice in one region where fuel and danger levels are low and man-power is abundant, compared with the necessity for bulldozers, heavy duty tankers, and water pumps in more serious situations.
It cannot be too strongly emphasized that the essence of fire control is the speed of initial attack; consequently the desirability of mounting a large number of well-distributed small vehicles for this purpose (using misting techniques where applicable) should be closely examined, in addition to the provision of large tankers for attacking head fires.
In most latitudes where man-made forests have been planted to date it is clear that fire protection cannot be ignored. It must be planned to meet the expected conditions, with an annual budget for preventive maintenance, and facilities to strike rapidly at an outbreak, which will usually occur on occasions of high danger rating. Annual fire losses are likely to be very variable and it is the big loss in the occasional severe fire season which appears to be the significant factor in determining acceptable loss standards.
All countries should ensure that they have sound forest and rural fire legislation and the means of enforcement, whereby commonsense restrictions on the lighting and control of fires can be imposed during adverse fire weather conditions. Forest closure and total prohibition on the lighting of fires are necessary measures on days of extreme fire danger. The collection of accurate fire statistics is an important aid for the design of fire prevention campaigns, as a check against the year-to-year effectiveness of the fire suppression organization and as a basis for the determination of realistic fire insurance premiums. Two new thoughts have recently emerged:
1. first pruning (in coniferous plantations) might be a legitimate cost against fire control rather than against silvicultural operations;
2. the cost of establishing a firebreak (access road) system may be at least in part a charge against utilization.
OTHER FACTORS
It is important in considering the establishment of man-made forests that the possible effects of various climatic factors are :not overlooked. Indeed, it has been suggested that risks (of all types) should be accepted as a normal feature of forest management (Brunig, 1967a). One of the most serious of these factors is cyclonic winds and there ale numerous examples of very large "blow downs" of planted forests, e.g., in Scotland (Andersen, 1954) where one storm caused the wind-throw of over 45 million cubic feet (1.3 million cubic meters) mainly of coniferous species, and New Zealand (Wendelken, 1966).
Cyclones seem to follow a more or less consistent pathway, and such areas could perhaps be avoided but the occasional gale cannot. Studies have shown that windthrow and windbreak can be minimized by appropriate silvicultural techniques and the careful selection of sites.
Hail is also a factor which causes considerable damage when the hailstones are of large size. The physical effect of stripping leaves and needles, however, is less serious than mechanical damage to the branchlets allowing the entry of disease (Diplodia pinea is an example).
Frost is frequently a hazard even to indigenous species and especially when a sharp unseasonable frost occurs. With exotic species failure may occur in frost hollows and necessitate a change of species at these locations. Snowbreak may limit the altitude at which a given species or strain can be grown successfully, even though all other factors are favorable.
Drought conditions can be very serious, if prolonged, in areas of relatively low, irregular or unreliable rainfall. Drought damage is far more widespread than often recognized, and can seriously affect the health and vigor of the crop. The effect is most severe on shallow and excessively drained soils or on sites with strongly fluctuating groundwater tables. In many instances growth check in plantations has been related to chronic or occasional water deficiency and, while high temperatures increase drought hazard, growth check due to water stress has been reported from all climatic zones in which trees grow. Selection of suitable species and hardy strains adapted to withstand periodic drought, avoidance of sites with unfavorable water regimes, heavy thinnings in certain cases, and irrigation should be considered when plantations are planned in areas where rainfall is critical.
Another meteorological phenomenon which has caused concern in plantations is lightning, and here reference is made to effects other than those associated with fire protection. Although no appropriate action can be taken to prevent such occurrences, it is important to recognize the effects, because the death of trees in the center of a yellowing patch followed by a spread of symptoms up to years after lightning strike has all the appearance of a pathological infection (Minko, 1966). The hidden and secondary effects may be even more important than the observable primary effects (Brunig, 1964).
Scurfield (1960) has provided a critical review of air pollution in relation to tree growth, together with a comprehensive bibliography. He distinguishes between general air pollution (produced by urban and industrial centers) and the effects of specific pollutants (such as sulfur dioxide from smelting operations). Apart from forests adjacent to mining plants and similar industries, the main damage would appear to be to street trees, parklands and ornamental trees in urban areas. To quote Scurfield: "A signal illustration of the well-known fact that conifers cannot generally be successfully grown in and near industrial centres was the removal in 1924 of the National Pinetum of Great Britain from Kew, near London, to Bedgebury in Kent,"
Protection from landslides and erosion on steep slopes in mountainous regions is important in countries like Japan where the problem is minimized by confining operations to very small coupes and replanting immediately. Avalanche and torrent control, together with the reforestation of eroded slopes in steep country are not considered in the context of this symposium, but remain special problems in protection forestry for the countries concerned.
Perhaps one other factor, like drought, which requires consideration at the planning stage is waterlogging.
Many species will not stand "wet feet" and the planting lines may require mechanical mounding in wet situations. The problem is enhanced if waterlogging alternates with dry periods during the growing season. Periodic waterlogging is also conducive to soil-borne pathogens (e.g., Phytophthora cinnamomi) and an evaluation of the other factors which might favor the spread of root rots should be made when choosing species for such conditions (Hepting, 1964).
Attention is drawn to the table prepared by Brunig (1967b) which summarizes, according to the Oxford classification, the available information on the extent, types and effect of damage caused by inorganic agents, and indicates the protective measures available.
Damage due to creepers, climbers, weed species in general, mistletoe, etc., which can be expensive to control especially in tropical areas, has been regarded as part of the tending operation, and has not received attention in this chapter.
It is clear from the foregoing that in -the temperate regions of the world the know-how of establishing and managing man-made forests is adequate enough to allow existing programs to be expanded or new projects to be commenced. There are many species for which techniques are time-proven and growth rates well documented. There is no doubt, however, that existing techniques will be improved as a result of current and future research, through the availability of sophisticated tools, and thanks to a better understanding of biological processes through fundamental studies.
In tropical regions the situation is less favorable, as only one or two species (such as teak) have been handled for a long enough period to ensure the reliability of methods, and to demonstrate adequate growth of utilizable material. Techniques for the growing of tropical pines and other conifers in these regions are still being worked out, and commercial species suitable for dry savanna areas and monsoon climates are only now beginning to be found.
The outstanding advantages of man-made forests are their high yields and quick returns, with all the attendant economies such as concentrated. working, saving of transport costs, and more uniform output, which result from intensive afforestation.
This study has shown that there are areas where a greater research effort is needed, for example, on the maintenance of site productivity, on the life histories and behavior of forest insects and diseases, and on species and techniques suitable for tropical regions.
There is need also for internationally acceptable measures of such factors as site index, and for uniformity or standardization in measuring techniques and the presentation of data on growth and yield.
ANDERSEN, K.F. 1954 Gales and gale damage to forests, with special reference to the effects of the storm of 31 January, in the N.E. of Scotland. Forestry, 27(2).
ANONYMOUS. 1966 The management of man-made forests and industrial plantations: problems and solutions. South Africa, Department of Forestry. Sixth World Forestry Congress, Madrid.
*BAKSHI, B.K. 1967 Diseases of man-made forests. Canberra.
*BAUGER, E. 1967 Mean heights in stands of Norway spruce and Sitka spruce in west Norway. Canberra.
BEAL., J.E. 1964 Bark beetles threaten destruction of Honduras pine forests. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects, Oxford.
BEGA, R.V., DOTTA, D., MILLER, D.R. & SMITH, R.S. 1966 Root disease survey at Boggs Mountain State Forest, California. Plant Disease Reporter 50/6.
BENEDICT, W.V. 1964 Principles, procedures and problems in controlling forest pests. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects, Oxford.
BENEDICT, W.V. 1966 Criteria governing control of forest diseases and insects in the United States. Sixth World Forestry Congress, Madrid.
BRUNIG, E.F. A 1964 study of damage attributed to lightning in two areas of Shorea albida forest in Sarawak. Commonw. For. Rev., 43: 116.
*BRUNIG, E.F. 1967a Forest damage as a risk factor in production planning. Canberra.
*BRUNIG, E.F. 1967b Protection against inorganic damage: types of damage other than fire. Canberra.
*BUNN, E.H. 1967 Growth rates, yield and yield prediction, continuous inventory, and changes in productivity. Canberra.
CROMER, D.A.N. 1966 A cooperative research project on Sirex noctilio. Sixth World Forestry Congress, Madrid.
DAVIDSON, A.G. & BUCHANAN, T.S. 1964 Disease impact on forest production in North America. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects, Oxford.
*DE BELLIS, E. & CAVALCASELLE, B. 1967 Control of the pine processionary caterpillar with Bacillus thuringiensis Berliner. Canberra.
DRIESSCHE, R. VAN DEN & WAREING, P.F. 1966 Nutrient supply, dry matter production and nutrient uptake of forest tree seedlings. Ann. Bot., 30/120.
*ESCHER, A. 1967 Observations on. the juvenile growth rate of Pinus radiata D Don. Canberra.
*ENDSJO, P.C. 1967 Comparative cost of production of man-made forests up to harvesting in different regions. Canberra.
FAIRBAIRN, DAVID. 1966 Forest Resources Newsletter No. 2. Australian For. Council.
*FENTON, R.T. 1967 Rotations in man-made forests. Canberra.
FOSTER, R.E. 1964 Known and potential hazards from root rot. FAO/IUFRO Symposium on internationally Dangerous Forest Diseases and Insects, Oxford.
FRANZ, J.M. 1966 Biological control of forest pests. Sixth World Forestry Congress, Madrid.
*GEMIGNANI, G. 1967 Observations préliminaires sur l'accroissement de quelques espèces d'eucalyptus dans l'agro pontino. Canberra.
GIBSON, I.A.S. 1964 The impact of disease on forest production in Africa. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects, Oxford.
*GIORDANO, G. 1967 Note sur l'accroissement de l'Araucaria angustifolia dans le nord de l'Argentine. Canberra.
*GROULEZ, J. 1967 Croissance et rendement de Eucalyptus sp. 12 ABL au Congo-Brazzaville. Canberra.
*GRAYSON, A.J. 1967 Afforestation planning at the national and project levels. Canberra.
HEPTING, G.H. 1964 Appraisal and prediction of international forest disease hazards. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects, Oxford.
*HOLLOWAY, C.W. 1967 The protection of man-made forests from wild life. Canberra.
IMAZEKI, R. 1964 The forest disease situation in the countries of the Far East. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects, Oxford.
JAHN, E. & WEIDINGER, N. 1966 Possibility of using rare earth metals for labelling forest insect pests in spreading experiments. Sixth World Forestry Congress, Madrid.
JEFFERS, J.N.R. 1966 Mathematical models in forest management...: nursery planning and production. Forest Record No. 69. London, Forestry Commission.
KEEVES, A. 1966 Some evidence of loss of productivity with successive rotations of Pinus radiata in the S.E. of South Australia. Aus. For., 30(1).
*KRUG, H.P. 1967 Planning for afforestation and planting in Brazil. Canberra.
LUCKHOFF, H.A. 1964 Diseases of exotic plantation trees in the Republic of South Africa. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects, Oxford.
MAKI, T.E. 1966 Need for fertilizers in wood production. Unasylva, 20(3): 49.
MAKOWER, M.S. 1966 Mathematical models in forest management: introduction to mathematical programming. For. Rec. No. 59. London, Forestry Commission.
MAPLESDEN, P.W. 1966 Management of man-made forests and industrial plantations in New Zealand. Sixth World Forestry Congress, Madrid.
MCARHUR, A.G. 1963 Forest fire danger meter MK3. Canberra, Forestry and Timber Bureau.
*MCARTHUR, A.G. 1967 Fire protection of man-made forests. Canberra.
MCCONNEN, R.J., NAVON, D.I. & AMIDON, E.L. 1966 Mathematical models in forest management. Efficient development and use of forest lands: an outline of a prototype computer-oriented system for operational planning. Forest Record No. 69. London, Forestry
Commission.
MINKO, G. 1966 Lightning in radiata pine stands in north eastern Victoria. Aus. For., 30(4).
MURRAY, J.S. 1964 Establishment of disease susceptibility plantations. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects, Oxford.
NEWHOOK, F.J. 1964 Forest disease situation, Australasia. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects, Oxford.
ORMAN, H.R. & WILL, G.M. 1960 The nutrient content of Pinus radiata trees. N.Z.J. Sci., 3(3).
OVINGTON, J.D. & MADGWICK, H.A.I. 1958 The sodium potassium and phosphate contents of tree species grown in close stands. New Phytol., 67(3).
OVINGTON, J.D. & MADGWICK, H.A.I. Distribution of 1969 organic matter and plant nutrients in a plantation of Scots pine. Forest Sci., 5: 344-355.
PACKHAM, D.R. 1966 Mapping forest fires through smoke. Aus. For., 30(4).
*QURAISHI, M.A. 1967 Some pathological problems of Dalbergia sissoo Roxb. (Shisham) and their solution. Canberra
RATCLIFFE, F.N. 1961 A review of the 1958 Melbourne Symposium on Rabbit Control, and its relevance to the present-day situation. Rabbit Control Symposium, Sydney 1960. Melbourne, Commonwealth Scientific and Industrial Research Organization.
SCURFIELD, G. 1960 Air pollution and tree growth. Forestry Abstracts, 21(3) and (4).
SHAW, C.G. 1964 Internationally dangerous foliage diseases. FAO/IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects.
SIMMONDS, F.J. 1964 The spread of forest insects in the world with particular reference to biological control. FAO/ IUFRO Symposium on Internationally Dangerous Forest Diseases and Insects.
SIMS, W.G. & BENSON, M.L. 1967 Atmospheric haze penetration in colour air photography. Fifth United Nations Regional Cartographic Conference for Asia and the Far East. Canberra.
STEVENSON, D.D. 1966 Management of industrial pine plantations in the southern United States: problems and solutions. Sixth World Forestry Congress, Madrid.
*STIELL, W.M. 1967 Plantation volume estimates from two stand parameters. Canberra.
STONE, E.L. & WILL, G.M. 1966 Forest soil relationships in. North America. Corvallis, Oregon State University Press.
STREETS, R.J. 1962 Exotic forest trees in the British Commonwealth, Oxford.
SWAN, H.S.D. 1966 Studies of the mineral nutrition of Canadian pulpwood species. Sixth World Forestry Congress, Madrid.
*TORRENT, J.A. & ROMANYK, N. 1967 Protección contra plagas. Canberra.
*VALENZIANO, S. & SCARAMUZZI, G. 1967 Preliminary observations on the seasonal diameter growth of Eucalyptus camaldulensis and E. viminalis. Canberra
WARDLE, P.A. 1966 Mathematical models in forest management: linear programming studies. Forest Record No. 59. London, Forestry Commission.
*WARING, H.D. 1967 The role of nitrogen in the maintenance of productivity in conifer plantations. Canberra.
*WEBB, A.W. 1967 The growth of mountain ash under plantation conditions. Canberra.
WEBSTER, H.H. & MARTY, R.J. 1966 Comparative analysis of costs and benefits of the various systems of silvicultural management. Sixth World Forestry Congress, Madrid.
WENDELKEN, W.J. 1966 Eyrewell Forest: a search for stable management. N.Z.J. For., 11(1).
*WENDELKEN, W.J. 1967 Records of plantation history: expenditure and revenue accounts. Canberra.
*WRIGHT, H.L. 1967 Plantation inventory in developing countries. Canberra.
YOUNG, H.E., CARPENTER, P.N. & ALTENBERGER, R.A. 1965 Preliminary tables of some chemical elements in seven tree species in Maine. Technical Bulletin No. 20. Orono, Maine Agricultural Experiment Station.
YOUNG, H.E. 1966 World forestry based on the complete tree concept. Sixth World Forestry Congress, Madrid.
NOTE: *Paper submitted to World Symposium on Man-made Forests and their Industrial Importance, Canberra, April 1967.
