A commercial softwood kraft pulp was beaten in a PFI mill for various periods and subsequently processed for 2000 revolutions in a Lampen mill. The ball mill post-treatment caused stretch but not breaking length to be decreased by up to 15 percent. The drop in handsheet stretch was explained by a re-distribution of mass, within fibres and within handsheets, which minimised fibre elongation in paper webs under strain. The decrease in stretch obtained by the Lampen mill post-treatments was examined in terms of paper properties and changes in fibre characteristics brought about by beating, i.e., fibre dimensions, fibre collapse and internal bonding, fibre wall fractures and dislocations, and fibre surface structure, fibrillation, and fines contents. Internal bonding was the fibre characteristic most strongly influenced by the Lampen mill post-treatment.

Rings of collapsed or crushed tracheids, whose thin walls have secondary thickening but lack lignin, have been found in the stems of Pinus radiata trees grown in containers and subjected to periodic drought. These rings appear to have arisen as a result of minimal waterings, sufficient to prevent mortality. Ring shake in forest-grown trees may be caused similarly.

Decay tests were used to determine levels of sodium pentachlorophenoxide required to provide desirable protection to exterior particleboard from decay fungi. The decay resistance of treated board was compared with that of timber (both naturally durable and preservative-treated) currently used in situations for which exterior particleboard is designed. Retention of 0.35% sodium pentachlorophenoxide should provide adequate protection.

Data were obtained from unthinned plots of radiata pine which had reached maximum density, as indicated by substantial and continuing mortality. A simple model of stand dynamics was estimated from these data. One of the equations in this model enables an estimate to be made of the maximum basal area a stand of given site, age and initial stocking could carry, thus providing a datum for a relative measure of stand density. Reineke's stand density index and modifications of it were shown to involve a source of bias which could lead to biased estimates of density.

A case is presented for using only direct estimates of volume and volume increment of a suitable sample of trees to measure responses to fertiliser in mature stands. Errors involved in estimating diameters, heights and stem volumes are briefly discussed, and methods of reducing these errors are given.

A fertiliser trial in a mature stand of radiata pine in Nelson, New Zealand, is used to demonstrate the relative success of several methods of measurement and analysis. Basal area was a poor indicator of response. Addition of a height estimate and the use of local regional volume functions gave inaccurate estimates of plot volumes and increments, as they did not take variation in tree form into account. Response to fertiliser over a 5-year period estimated in this way and adjusted by covariance analysis, had wide confidence limits (43.2 ± 42.00 m³/ha). Sectional measurements made at the start and end of the trial, or made by stem analysis and employing general volume/d² regressions for the stands or treatment were also inadequate as they did not take site variation into account. A similar technique, but on an individual plot basis, yielded a more precise estimate of volume response (59.5 ± 23.34 m³/ha) over the 5-year period. Two analyses of covariance on single trees and use of regression estimators to convert to a unit area basis gave responses of 60.8 ± 27.58 and 43.7 ± 28.73 m³/ha. Stem analysis and statistical evaluation of single trees were also able to provide information on the responses of different tree sizes and on chosen sections within the whole stem, and for annual as well as periodic increments prior to and following any fertiliser treatment. It is concluded that stem analysis and statistical evaluation of single trees would use the benefits of analysis of covariance to best advantage.

A fire lit in scrubland at Pouakani, near Mangakino on 18 January 1974 in the course of land clearance prior to afforestation, unexpectedly gave rise to violent whirlwind. From the synoptic situation and known meteorological factors, it is concluded that the whirlwind occurred in a situation with low stability and with light winds in a deep layer associated with a "heat low".

Inoculation trials confirmed the ability of Diplodia pinea (Desm) Kickx to invade undamaged young green shoots of Pinus radiata D. Don, resulting in dieback. The top 5 cm of young shoots of seedlings and rooted cuttings from 5-year-old trees, were brushed with droplets of a spore suspension and kept under misting at 25°C for 48 h. Of the plants thus inoculated, 50-80% developed shoot dieback, which always originated from necrotic stem lesions. Ripened host tissue was resistant to infection, even after wounding. There was no evidence of important differences in either pathogenicity or virulence in 18 isolates of D. pinea obtained from different parts of New Zealand. This suggests that the severity of dieback in certain parts of Tarawera Forest has not resulted from the emergence of a more virulent pathogenic race.

These results, together with an earlier field study, provide convincing evidence that D. pinea was the primary incitant of leader and shoot dieback in the Putauaki Block of Tarawera Forest.

Eleven Pinus radiata trees grown from seed in the Australian Capital Territory were kept as a hedge two metres high from age five years by removing all long-shoot buds in the autumn of successive years. Wood specimens from these and 11 normal trees growing nearby were examined. The hedged trees exhibited reduced radial growth rate, larger spiral grain angles, shorter tracheids and reduced density values compared to normal trees. The wood of ramets derived from the hedged trees at age eight years was not different from that of ramets propagated from normal trees grown from seed.

In the interests of obtaining a terminology of pine shoot growth which is applicable to all species in the genus, it is proposed that the terms spring shoot and summer shoot should be dropped from the literature; and that usage of the term free growth should be restricted. The term predetermined growth is preferable to that of fixed growth.

This paper describes and analyses primordial initiation and development, and the subsequent elongation, of the leading shoot of a clone of Pinus radiata D. Don at two sites in New Zealand.

At Rotorua, initiation of the components of the annual shoot began between mid-September and mid-October and finished during August. Five clusters of branches developed, the first three of which bore seed cones. These clusters were initiated in December, at the end of January, and during March.

At Waimihia, located at a higher altitude than Rotorua, only three to four clusters of branches were initiated in the annual shoot, with at most two of those containing seed cones.

In Rotorua the new shoot began elongating in December, and by the time seasonal extension growth slowed (July) nearly half of the annual shoot extension had taken place. The remainder occurred the following spring.

Physiognomic importance of each plant species was estimated at 49 stratified random locations in the proposed Taunoa Biological Reserve, an area of podocarp, hardwood and beech forests in the Longwood Range, Southland. Agglomerative grouping, direct and indirect gradient analyses revealed that an ordination using the Euclidean distance D provided the most informative treatment of the field data. Vegetation in the reserve is best described as part of a forest continuum varying in composition and structure chiefly along an altitudinal gradient.

Agglomerative groups distinguished nine forest communities, six of which were described in the National Forest Survey (N.F.S.) Type classification of the area. Forest communities derived from N.F.S. typing and agglomerative grouping were found to be closely related to the pattern of locations displayed by the two dimensional ordination. Quantitative treatment thus confirms the validity of N.F.S. Types in this area at least and supports their use in planning Biological Reserves. The more sensitive ordination techniques are considered to have value for analysis and interpretation of the detailed biological information being gathered in ecological surveys of indigenous forests.

Unthinned radiata pine plantations on long rotations incur serious risk of insect or disease attack. Economic analysis of a silvicultural regime that incorporated a production thinning revealed that a pulpwood thinning contributed a negligible net return and had the effect of substantially extending the rotation. This led to the development of an alternative regime giving similar volume yields, but economically and silviculturally superior; this regime incorporated wide initial spacing, heavy early thinning (without yield) and severe pruning.

Tending practice, being a function of management, depends as much on the economic and physical background in New Zealand as on silvicultural objectives produce maximum volume or value yields. The background facts relevant to plantation practice in New Zealand include a massive planting programme with concomitant silvicultural commitment, a large involvement by non-state agencies, an urgent need to diversify export markets, often steep terrain and high labour and machinery costs.

The area of proven tending practice for radiata pine is limited. This is why many different silvicultural regimes have been proposed but few have survived. The simple plant and clearfell regime has been applied most widely. For this reason the principles to adopt in deciding how the species should be grown and harvested are most important. Suggested principles are: define the target tree taking into consideration markets, profitability and the technical requirements of wood quality; minimise growing costs; simplify management wherever possible but without sacrificing market flexibility; and reduce as much possible biological, physical, management and market risk. The background facts and these principles suggest a sawlog final crop is logical for most New Zealand plantations and trends indicate it will normally be grown on a rotation of 20-30 years. A proportion of the resource will be pruned to 6 m and stockings will be relatively low in these stands. Steep country is unlikely to be production thinned but the practice will continue in State forests while old regimes grow through to rotation end. Some private organisations will continue to production thin because they believe it is in their interests to do so. Future developments production thinning are likely to include a geometric approach to tree removal, relaxation of unnecessarily rigid specifications, intensive method improvement, and adoption of skidding machinery which has high productivity in relation its capital cost.

Research must continue to focus on overall evaluation of the growing and harvesting system. This will highlight priorities for micro-economic research by a balanced multi-disciplinary team. Principal targets in the Forest Research Institute programme have a bias towards silviculture and clearfelling but this seen to be appropriate.

Measurements from all the Company's spacing and thinning trials have been pooled, growth models calculated and a programme called PREDICT developed which simulates stand development, estimates assortments, growing costs, net present values and mean harvesting costs for various thinning schedules and rotations. Each thinning can be nominated as to age and intensity of thinning on the basis of either thinning to a residual basal area or to a volume to be cut per acre.

Options on thinning type enable simulations of ''mechanical" thinning (all diameter classes), thinnings from "below" (small diameter classes), thinnings from "above" (large diameter classes), or a combination of mechanical with either "below" or "above" as would occur for example in a thinning involving removal of rows for access and selection thinning.

A series of runs on this model within the bounds of the data used indicate that Pinus radiata is a very flexible species.

(i) Type of thinning does affect final crop tree size but does not greatly affect growing costs or volume production;

(ii) As thinning intensity is raised volume production is lost but this does not affect growing costs greatly as the economic benefit from larger earlier returns compensates for lower productivity where thinnings are heavy;

(iii) Net present values fall as stocking per acre is increased although volume production rises;

(iv) As rotation age is increased to 20 years, volume production rises steadily while harvesting costs fall rapidly. Extrapolating the data beyond 20 years indicates a maximum net present value at 30 to 35 years.

This paper has already been published Appita 27(4): 251-61.

Economic comparisons have been made of a number of alternative silvicultural regimes in Pinus radiata plantations in New South Wales. These comparisons, done with the aid of computer simulation, have indicated that relatively severe thinning regimes are financially preferable to those incorporating light and frequent thinnings, and that optimal financial rotations over a wide range of forest conditions are in excess of 45-50 years. The critical factors influencing the profitability of silvicultural regimes are shown to be the effective discount rates used and the price size gradient of harvested wood. Other factors which influence profitability are also discussed. For large plantation owners such as the Forestry Commission of New South Wales it is not feasible to treat plantations by one optimal silvicultural regime. Meeting aggregate wood demands requires application of a number of alternative silvicultural regimes, some sub-optimal, so that maximum benefits are obtained from the total plantation in a defined geographical zone.

This paper compares the relative merits of performing a first commercial thinning operation in radiata pine plantations on the basis of either row thinning or selection thinning from below. These two approaches are compared on the basis of silvicultural considerations (growth, quality and stability of the retained stems) economic and financial considerations (to both the grower and the harvester) and wood flow considerations.

Row thinning is cheaper and easier than selection thinning, provides more scope for mechanisation of harvesting, and reduces tree marking and supervision costs. On the debit side, it reduces the options for selecting crop trees for retention and reduces the yield of sawlogs in second thinning.

It is concluded that third row outrow thinning is a practical and acceptable thinning technique for radiata pine, except for stands containing large numbers of defective trees, and possibly for stands particularly prone to wind or snow damage.

This paper describes work undertaken by the Forests Commission, Victoria, in developing a computer-based model for evaluating silvicultural regimes for Pinus radiata. Following a discussion of the value of such work, the model is described according to its four sequential modules which relate respectively to stand growth, estimation of produce, evaluation and cash-flow analysis. Various auxiliary studies are also outlined in order to indicate the breadth of the project and its current state of development. Some early results of the work are discussed briefly.

Factors which generally influence companies in making forest management decisions include company strategy, policy and objectives, anticipated wood demand-supply situation, financial considerations and Government incentives. Decisions regarding production thinnings will also be affected by the cost and value of the thinnings, the long term forest management strategy particularly with respect to stand parameters and the wood properties and quality of thinnings.

Responses to these factors largely depend on the nature of the forest growing companies. Three types are recognised, based upon the relationship between annual sales and the value of the fixed assets. Most sawmilling companies are in the first group where annual sales are greater than the value of the fixed assets. The second group, where annual sales are comparable with fixed assets value, is exemplified by pulp and paper companies. The final group, with annual sales less than the value of the fixed assets includes the purely forest growing companies with no processing interests.

The role of thinning is considered from the time of the decision to commence investing capital in plantations.

Thinnings provide the raw material for use by the firm's log conversion plants and contribute to the cash flow. They reduce the cost of growing wood in the plantation by reducing the debt on the plantation and by reducing the time taken to grow trees of a desired diameter. Capital is returned to the firm for reinvestment and a larger annual increment earned on a smaller invested capital.

Thinning gives a flexibility to the products cut from, and overall wood resource represented by, the plantation. Silvicultural roles express themselves in the well-being of the total enterprise. The effect upon the condition and size of the knots is the most important of these roles.

Thinning reduces the likelihood of attack by pathogens.

For decision-making in the future, we need a tool which relates the effect of thinnings on a plantation with the effect on the industrial wood-converting side of the enterprise.

The economic evaluation of thinning is complex and should include the interaction of tree-stand, utilisation, linked economic, and local management factors. Tree-stand data needed include the malformation percentage; mortality rates; stand volume and piece-size projections; changes in timber quality; hydrological and ground-cover effects. Utilisation data include the differential costs and returns of each piece-size class. Linked economic data include differential haul rates; returns to scale of utilisation plants; and economic multiplier effects through time. Local influences, which may become dominant, include biological, climatic and topographical considerations. The opportunity costs of thinning can include reduction in final crop increment rate; postponement of cash flows from greater volumes of clearfellings, and postponement of linked utilisation benefits.

As thinning is a more complex operation than clearfelling the postponement of the greater yields foregone should be justified when production thinning is prescribed.

Economic rationalisation of silvicultural regimes has enabled national and regional wood supply planning to be revised on a more realistic basis.

This paper briefly reviews thinning practice in each of the main woodproducing forest types of Victoria. It is seen that thinning practice varies a great deal between, and to a lesser extent within, forest types.

Possible reasons for the variations in thinning practice are deduced, and the matter is further examined by reference to three case studies (ash-type eucalypts, pine, and box-ironbark.) It is concluded that in Victoria important determinants of thinning practice have been topography/access, various aspects of marketing, and the capacity of the forest resource.

The Bay of Plenty region in central North Island is well endowed with plantations of radiata pine which, however, are grossly uneven in age class distribution.

The older stands are needed until 1990 to sustain supplies until the much younger stands can take over. Instability in the older stands and susceptibility of other pines to disease has induced a high level of cutting now and a critical supply situation about 1990 even after rotations have been shortened to the point where utilisation of thinnings is no longer viable. Relatively short rotations for radiata pine for post-1990 wood supply are proposed for State forests. These rotations are primarily to produce sawlogs, some of high quality resulting from intensive silviculture, the rest to be of lesser quality from minimal silviculture.

The end result will be sawlogs from the butts producing about 40% of the yield with the untended tops destined for chips and pulpwood.

The problems encountered in evaluating the role of thinning are displayed by considering a simple General Development Model for the creation of new forest industries and their associated plantations. Thinning is seen as having important effects on meeting objectives. The current position in developing models to aid decisions is explored by reviewing models used at the stand, plantation and national levels in Australia and New Zealand.

The development of the Windsor Tree Harvester is outlined. Production and availability statistics are given. Mechanical problems and where possible, solutions to these problems, are discussed. Non-mechanical problems associated with the introduction of any mechanised harvesting system are raised. A series theoretical costings is given.

This paper has already been published: Appita 29(6): 453-6.

Economic evaluation of alternative silvicultural regimes for radiata pine has shown that a substantial opportunity cost can be incurred if the growth of the crop trees is penalized, and their date of harvest deferred, in the interests of obtaining a sale for thinnings. The effect is greatest when a pruned final crop element, that has been defined from an early age, is allowed to be severely checked through competition from unpruned neighbours. In this instance, the case for production thinning depends largely on whether the unwanted trees can be extracted before they markedly impinge on the growth of the pruned final crop trees. Such competition is apparent from an early age in selectively pruned stands, to the extent that production thinning becomes difficult to justify. It is feasible, however, that the onset of competition may be delayed by distinguishing the crop component of the stand from the thinnings component from the outset, by separating the two elements as much as possible, by applying treatments to the crop that will give them a distinct competitive advantage, and by arranging the thinnings in ways that favour mechanization and cheap extraction of small diameter material. Trials have been established to test the concept, and more are planned.

The South Australian Government forests of the south-east of South Australia are used as an example of thinning operations control.

Three stages of control action are used to co-ordinate long term forest development requirements with needs of utilisation plants subject to short term changes in demand.

Existing established harvesting systems and the recent development of greater mechanisation are compared. Alterations in control and scheduling of operations to handle these changes are proposed and discussed.

This paper assumes the decision has been made to carry out production thinning at various ages. It traces the scope and development of the thinning operations in the Kinleith forests since they were first started on a production scale in 1958. The evolution of extraction techniques is discussed as well as the significance of the thinning volume in the overall wood supply to the Kinleith integrated mills. Crew production is discussed and the way in which the contract payment rates are determined is described. A table of the thinning prescription is included. The various limitations on such an operation are dealt with as they occur in the forest, during loading and transporting, as well as in the mill yard and plant. So long as labour can be obtained for this work and costs can be contained by overall efficiency, the higher cost thinning wood will be acceptable in the total wood supply mix for the mill.

This paper reviews the various thinning methods and equipment available to the forest manager for a range of silvicultural practices, including thinning to waste.

Considerable increases in the productivity of conventional chain saw-based techniques have been obtained by variations to wood specification, the introduction of forwarders for extraction and the training of the cutter force.

The introduction of more mechanised techniques has commenced but acceptance has been slow. It is considered that the mechanisation of early thinnings is most likely to be economic under favourable stand treatment and terrain conditions, where simpler and less costly machines can be used.

The mechanisation of these operations can be facilitated by increasing the stem size of the trees to be removed or by reducing wood specification to permit multiple stem harvesting.

The past and present problems of extraction thinning on a large exotic forest of predominantly easy topography is discussed in relation to previous silviculture and other, competing logging operations. Despite a background of successful extraction thinning of other species and old crop radiata pine, thinning of young radiata pine has only recently become a silviculturally successful and economically viable operation. The relatively small tree size and high labour and capital content per unit volume produced are seen as the cause of poor past performances in this operation.

Both the wood wasp Sirex noctilio and Dothistroma pini, the needle cast disease, have had a significant influence on management of Pinus radiata in Kaingaroa Forest. Neither have caused a serious reduction in the growth of that species. The S. noctilio epidemic of 1949/50 acted as a beneficial natural thinning of the first crop stands which would otherwise have been grossly overstocked today.

Sirex noctilio provided the impetus to thin the radiata young crop together with criteria for the selection of regimes. The serious D. pini infection of P. ponderosa and P. nigra and the concurrent ill health of other old crop species has forced the introduction of severe thinning practice in the radiata young crop to bring forward their age of clearfelling so that the cut in the first crop can be accelerated.

The continuing controversy with regard to the relative merits of heavy-early non-commercial thinning, and the more conventional regimes employing one or more productive thinnings, has been based predominantly on economic argument. Little consideration has been given to their relative performance in terms of yield. This is due to the absence of extended measurement of severely thinned stands and to the restricted relevance of currently available growth models.

The paper describes the work being undertaken to derive a growth model for radiata pine from Kaingaroa growth plot data. While this study has not yet been completed an interim growth model has been derived. Preliminary checking has shown it to be reasonably accurate and unbiased when applied to a wide range of management practice and it has been used to derive criteria for the production of maximum yield.

Analysis of stand simulations has shown that in stands with low initial stockings, or in heavily thinned stands, short rotations will sacrifice volume production and that this loss is increased as site index decreases. It demonstrates that the reaction directly attributable to a thinning is relatively small, and that a wide range of management practice results in very little variation in total volume production. To obtain optimum yield, low initial stocking or very early thinning to waste is required on good sites (where Mean Top Height at age 20 exceeds 30 metres). On poorer sites and for short rotations (less than 30 years) pulpwood regimes with high stockings producing small piece size may be most productive, while a series of very light production thinnings may produce optimum total volume production on poor sites.

The consequences of thinning in coniferous forests are likely to differ according to the parasitic status, the life cycles and the mode of infection of pathogens. Each potential disease situation has to be considered individually before thinning regimes and intensities are recommended.

A replicated spacing/thinning trial in the Tarawera Valley, New Zealand, illustrates some of the silvicultural aspects of thinning radiata pine. Stands which have not received a thinning are liable to volume loss through natural mortality and reduced increment through suppression. Malformed trees will be present in the stand and this may result in volume loss or restrict the choice of harvesting method. Piece sizes will be smaller in unthinned stands than for thinned stands of the same age and the work content per unit of wood extracted is therefore likely to be greater.

Thinning offers a choice; firstly to remove malformed trees, and secondly to mould the residual crop according to the morphological features desired. Over the range of post-thinning stand densities quoted here (1000-375 stems/ha thinned at approximately 11.5 m) increment of basal area per hectare was uniform — individual tree growth being greatest in the lowest stocking. This allows the forester to determine the size of his crops at harvest. Piece sizes for the thinnings documented were small.

Increasing the minimum length or minimum small end diameter regarded as harvestable decreased the volume potentially available. This effect was greatest for the earliest thinnings.

When foresters are charged with providing a resource of raw material for industrial processes they can and should design the regimes they employ to achieve their objectives as efficiently as possible bearing in mind all the biological aspects mentioned here.

In south-western Australia, which possesses a strongly seasonal, Mediterranean type of climate, moisture availability is a very strong determinant of pine growth potential. This is in turn determined by the depth and moistureholding capacity of the soil, which limits the magnitude of moisture storage during the winter, and by the density of the stand, which controls the rate of exhaustion of the stored water during the spring and summer growing season. In stands which do not tap the regional groundwater table, the volume production is largely independent of density within a very wide range of basal area levels. By contrast, diameter growth is very strongly influenced by stand density. In dense stands, all readily available moisture is exhausted by November and diameter increment ceases. In heavily thinned open stands moisture availability and diameter growth continue until the following March or April. Application of fertilisers must be preceded by reduction in stand density to be effective. Success of density reduction by thinning is dependent on subsequent control of pine coppicing and of weeds.

Moisture limitations manifest themselves, in order of increasing intensity, firstly in depression of diameter growth, secondly in predisposition to attack by Ips grandicolis, and finally in direct drought deaths. Prevention of this can be achieved either by early non-commercial thinning, or by planting of genetically improved stock at wider spacing.

Biological factors, both inherent to the individual tree and due to tree-site interactions, impose constraints on thinning practice. The very fast early growth rate of Pinus radiata D. Don makes early thinning desirable to avoid problems of competition, disease and insect susceptibility and instability to wind. Correct silvicultural techniques have been devised to meet many of these problems and tree breeding offers solutions to others. However, there are still many natural risk factors which cannot be avoided, only minimised through careful planning.

This review attempts to cover past, present and future objectives of thinning and outline current practices with the emphasis on why and how they have evolved.

First, to point out the obvious—thinning is only one of a number of devices available in New Zealand or elsewhere to shape production forests to particular end purposes. Others include choice of sites, rates of planting, initial spacing, pruning, tree breeding, and the approach to regulating cut. In attempting to achieve whatever end use objectives are laid down none of these means of manipulating the crop operates independently of the rest.

Thus, one will not observe any uniform approach to current thinning practice in New Zealand. Sites range widely from nitrogen deficient coastal sands supporting radiata pine of fine branch and stem form to fertile pumicelands with a more malformed but swiftly growing crop. Superimposed on these physical differences there are, even State forests, widely varying management objectives from region to region and a large measure of local autonomy in how they are achieved. Moreover, except in the few areas where plantings are starting from scratch the forester inherits past planting rates, often in the form of a markedly abnormal set of age classes, the results good or bad past fashions in tending, and commitments of varying length and complexity to supply particular products to industry. He is thus commonly constrained, to a considerable degree, in his choice of management strategies. His task is usually to effect a transition from the existing forest to that which he conceives as the ideal. In so doing must meet existing commitments as efficiently as he can and create the most favourable opportunities for additional future market outlets. He seldom has sufficient mensurational data to predict with precision the quantitative and qualitative consequences of his choice of thinning and silvicultural schedules and even if the physical outcome were forecast with certainty he would still be faced with uncertainty of markets and hence of the relative return to be expected for various products, raw or processed, export or domestic, 20 years or more hence.

The inevitable consequence of uncertainty is that, when all that can be has been made explicit, there remain various choices which are essentially value judgments and for this reason alone there will be no uniformity of approach in thinning practice unless decision making is completely centralised.

Finally, despite the many constraints which he commonly faces, the forester can exert a major, lasting influence by the way he manipulates, through thinning or other practices, the younger age classes in his care.

This paper deals mainly with radiata pine (Pinus radiata D. Don) in Australia. 1974, this species covered 65% of Australia's total plantation area of 560 000 ha. Thinning in forests other than plantations was negligible. In concentrating on radiata pine, the most important plantation species which will be neglected are slash and hoop pines (Pinus ellottii Engelm. and Araucana cunninghamii Ait.); together these amounted to 20% of the plantation area in 1974. Attention is drawn to this exclusion because there are significant plantations of species other than radiata, and because a good deal of effort has been given to the thinning of these other species by staff of Queensland Forestry Department.

No special reference is made to material which is to be presented in detail by other speakers over the next three days, so that, to the remarks which follow, the various position papers must be added in order to obtain a full summary of Australian past present practice, and likely future trends.

Local employment multipliers for new pulp and paper mills ranging from 1.1 to 1.4 are derived from a study of Kawerau, a town almost totally dependent on the pulp and paper industry.

Estimates of local employment multipliers for new plants are shown to be highly sensitive to the extent of underemployment in the region prior to the plant's establishment. Any under-employment results in some of the servicing being undertaken by the existing servicing workforce, and in some of the jobs in the mills being taken, on a short-term basis, by farmers and workers in farm-associated occupations.

Wood properties of trees grown from seed are compared with those of grafts made from ortets aged 6, 15 and 40 years. With the change from seedling to mature state, diameter growth, bark thickness, wood density and shrinkage decreased in value, while tracheid length, extractives content and pith diameter increased in value. Marked clonal variation, which was independent of maturation state, occurred in many of the characters examined, making it desirable that wood properties be incorporated in clonal selection programmes.

The ash, silica, and lignin content were determined for beech (Nothofagus spp.) and other hardwood species (Quintinia acutifolia, Metrosideros robusta, Weinmannia racemosa) of the South Island beech forests. Wood samples from all species had moderately high ash content (about 0.6 percent). Bark from the four beech species had extremely high ash contents of 3-7 percent.

Wood from all 15 mountain beech and one of the hard beech trees examined contained significant but only moderately large amounts of silica. All other wood samples were essentially free of silica.

Acid-soluble lignin constituted about 20 percent of the total lignin and about 4 percent of the wood substance in all wood samples examined.

Sawn timber of radiata pine (Pinus radiata) and also tawa (Beilschmiedia tawa) was kiln dried at varying temperatures up to 115°C or was air dried. It was then assessed for rate of moisture uptake and swelling when exposed to high humidity in the laboratory or to fluctuating humidity outside under cover.

There is a progressive reduction in both moisture uptake and swelling as drying temperature is increased but, under commercial conditions, high-temperature drying at 115°C for less than 1 day will lead to only slightly greater stability than drying at 77°C for 3 days. Timber dried at either temperature is substantially less responsive to high humidity after drying than air-dried timber, with reduction in swelling of 12-35 percent.

Profitability of Douglas fir afforestation on a 55-year rotation, producing 186 m³/ha from thinnings at age 35 and 932 m³/ha from clearfelling for sawlogs, shows an internal rate of return (IRR) of 5.8% when social items are included, and 6.2% when social items are excluded. The biggest direct costs, at 6% interest, are for salaries and administration.

Timber realisations are based on analysis of sales of 120 000 m³ from the largest producers, allowing 45% as export timber, with the price of thinnings being $9.00 and of clearfellings $18.21/m³ on truck. The IRR rise to 6.4% and 6.75% if logs are exported ($25.03/m³ on truck), but are relatively insensitive to considerable changes in cost and return levels.

Results are similar to those calculated in 1967; radiata pine (Pinus radiata D. Don), because of its faster initial growth rate, is a far more profitable species.

A locally occurring dieback, similar to previously reported "red top", "shoot blight", and "tip blight", was investigated during 1971-73 in Pinus radiata in Tarawera Forest. Observations of symptoms and disease development, and isolation of fungi indicated that the dieback originated in necrotic stem lesions from which Diplodia pinea was invariably isolated. Succulent green shoots became infected in late spring and early summer while ripened shoots were apparently resistant, so dieback was restricted mainly to current season's growth. There was no evidence that infection was associated with wounds or frost damage, but there was every indication that it occurred through intact host tissue.

Pinus radiata D. Don cuttings (taken from 5-year-old plants and set 3 years previously) and seedlings of two different ages (3-year-old and 6-month-old) were inoculated with Dothistroma pini Hulbary conidia and grown for 3 months in growth rooms (temperature 20°C day/120 C night) under four different light intensities (181, 133, 94, and 58 W/m²). Light intensity did not affect either germination of D. pini conidia or early growth of the fungus on the needle surfaces. The pre-reproduction period of the fungus was less than 2 weeks for all treatments, except on cuttings grown under the lowest light intensity treatment where it was 6 weeks. The severity of infection of the cuttings decreased linearly with decreasing light intensity and seedlings were more severely infected than cuttings under all treatments. The degree of infection is related to the effect of light intensity on the host plant rather than on the fungus.

Plots in a randomised block experiment in a 15-year-old plantation of radiata pine (Pinus radiata D. Don) of nominal stocking 1700 stems/ha and basal area approximately 40 m²/ha, were thinned mainly from below to 11, 18, 23 and 28 m²/ha respectively. Each plot was again thinned 2, 5 and 8 years later to its prescribed lower basal area. Plots given a single light thinning at age 20 years maintain stand hygiene were used as control.

Total tree height, mean stem internode length and number of green branches per whorl were the only variables of the eleven sampled to be unaffected by treatment. Thinning caused a significant increase in branch diameter particularly the upper mid-crown, corresponding to 50-80% of total tree height, and altered the proportion of branches in the < 1-cm and 3- to 5-cm diameter classes. These proportions decreased and increased respectively with increase in the severity of thinning.

The relationship between cross-sectional area of the bole at the green crown base and total branch cross-sectional area within the crown is shown to be linear and independent of thinning.

Five-year-old trees of Pinus radiata D. Don were artificially defoliated by removing needles of various ages according to 19 treatments ranging from no removal to complete defoliation. Growth was followed for up to two years after defoliation. Removal of 3- to 4-year-old foliage in early spring generally did not cause significant losses in increment, but in combination with removal of 2- to 3-year-old foliage caused losses of up to 15 percent. Removal of 1- to 2-year-old foliage reduced height, basal area, and volume growth by 20, 43 and 51 percent respectively; in combination with removal of 2- to 3-year-old foliage, losses increased to 26, 63, and 70 percent. Removal of the current year's foliage as it was formed caused height, basal area, and volume growth losses of 53, 73 and 77 percent respectively over the two years. Growth was most severely reduced for trees defoliated in September, less so in December, and still less so for March or. June treatments. Trees completely defoliated appeared to recover slowly, but further defoliation killed all the trees. Partial defoliations resulted in no mortality, but all treatments caused a drop in growth, the biggest with removal of the current year's foliage and the smallest with removal of 3- to 4-year-old foliage. An equation of the form of a slowly increasing parabola is presented to quantify volume increment losses in terms of degree of defoliation.

Although results here are quantitatively different from other studies they show also that, with severe partial defoliation, basal area and volume growth are reduced more than height growth.

Above-ground dry matter and nitrogen distribution were estimated in 4-year-old stands of Pinus radiata where lupin growth in the artificial ecosystem was normal (L), and where lupin had failed to regenerate after the trees were released at age 6 months (NL). Dry matter totalled 32 tonnes/ha in each case. In L the dry weight of litter and tree tops was lower, but slightly more non-lupin understorey growth was present. Biomass plus litter contained 90 kg/ha more nitrogen, much of which was in the lupin plants themselves. Litter and tree tops contained less nitrogen (5 and 15 kg/ha, respectively) than in NL, but the nonlupin understorey contained almost twice as much nitrogen as that in NL. Consideration of nitrogen concentrations in biomass components suggested that trees in NL were under nitrogen stress.

Stocking differences between the two stands precluded investigations on tree growth after canopy closure.

High day and night temperatures (28°C) inhibited elongation of the mainstem but not branches in Eucalyptus obliqua L'Herit seedlings. Inhibition of stem growth was associated with amounts of growth inhibiting substances detected in the stem.

A wide thermoperiod with nightly chilling (28/5° C and 24°/5°C day/night temperature) increased (a) branch number, (b) root/stem and root/shoot dry weight ratio and, (c) levels of cytokinin-like growth promoting substance. Results suggest that these environmental effects on branching and seedling development are mediated through effects on the amounts of growth promoting and inhibiting substances in the stem.

Pinus radiata D. Don seedlings were raised at a variety of seedbed densities under otherwise routine nursery conditions. Planting stock characteristics were determined at the time of lifting using routine grading criteria. Increasing seedbed density reduced seedling size and quality.

Field performance of the stock types was determined on a moderately severe site prepared for routine plantation establishment. Tree size and survival were significantly decreased for plants raised at higher seedbed densities. The effect persisted up to the fifth year after planting.

Because of increasing difficulty in collecting cones from taller trees in the Tallaganda seed orchard, two blocks of trees were pollarded at about 8 m in late 1970. The 1974 seed crop from these blocks was almost twice that of other blocks in the orchard. Pollarding has not only extended the productive life of the orchard, but may also have increased its average annual production.

Seasonal trends in the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in the foliage of 7- to 9-yearold Pinus radiata were followed at four sites in New Zealand, revealing large seasonal changes which also usually differed with site. N, P, K, and Mg concentrations were low in mid-summer with a rise, except for P, later in the growing season. Ca levels rose steadily as the foliage aged.

Between-tree nutrient variation was lower for first-year foliage than for that in its second growing season. In first-year foliage, N and P tended to have a lower coefficient of variation in summer than in winter but the opposite was true for K. For between-tree variation within seven dominants on each of 127 sites throughout New Zealand the coefficient of variation averaged 8.5, 13.8, 15.6, 24.0, and 20.4% for N, P, K, Ca, and Mg, respectively. Sampling intensity required to detect differences of 10 and 20% of the mean varied widely with the element; for most studies a minimum of 10 trees should be sampled at each site.

For Pinus radiata in New Zealand collection of mature-length foliage of the current growth year from upper crown second-order branches is recommended. For N, the sample should be collected from late January to March; for P, from late January to May; for K, from March to May; for Ca, March to June; and for Mg in January. A compromise for all five elements is to collect between late January and March.