Review of "Tree diseases in Victoria" by G. C. Marks, B. A. Fuhrer and N. E. M. Walters.

Of the leafspot diseases of eucalypts recorded in New Zealand, only those caused by Mycospbaerella cryptica (Cooke) Hansford, M. nubilosa (Cooke) Hansford, and Septoria pulcherrima Gadgil & Dick are considered to be of any significance. Other fungi reported are Aulographina eucalypti (Cooke & Massee) von Arx & Muller, Cercospora eucalypti Cooke & Massee, Hendersonia spp., Microthyrium eucalypti P. Hennings, Phaeoseptoria eucalypti Hansford, Trimmatostroma bifarium Gadgil & Dick, and T. excentricum Sutton & Ganapathi.

One hundred and twenty-six seedlots (115 open-pollinated families and 11 composites) of Eucalyptus fastigata Deane & Maid, representing eight native provenances from New South Wales and Victoria, one exotic population from South Africa, and 15 exotic populations from New Zealand were planted in tests in 1979 at Kinleith and Kaingaroa, New Zealand. The trees were assessed at Kinleith in 1980 for height growth and tolerance to winter frosts, and at Kinleith and Kaingaroa in 1981 for incidence of forking.

The seedlots varied greatly in frost tolerance, height growth, and incidence of forking. Components of variance for ''provenances" were 3 to 4 times larger than components for "families-in-provenance". The hardiest provenances generally grew the slowest and showed the lowest incidence of forking. By far the hardiest native provenances were from Oberon and Barrington Tops, New South Wales, confirming the outstanding frost-tolerance of these provenances recorded in artificial frosting tests. Families from New Zealand and from Robertson, New South Wales, were notably more frost-tender and more forked than those from other Australian localities, and from South Africa. New Zealand families from Oakura and Hunterville showed excellent vigour but generally poor frosttolerance and a high frequency of forking. The provenance in which the families possessed the best combination of good frost-tolerance, fast growth, and freedom from forking was from Bondi State Forest (south of Bombala, New South Wales) towards the southern end of the species' natural range.

The phenotypic correlations among family means within provenances were -0.41 between frost score and 1-year height (i.e., the tallest families generally showed the least frost damage), and 0.49 between 3-month and 1-year heights. Frost score at Kinleith was not well correlated at the family level (though highly correlated at the provenance level) with incidence of forking at either Kinleith itself or Kaingaroa.

Hypocotyl segments of Eucalyptus globulus Labill., when cultured on a defined Schenk & Hildebrandt medium with auxin and cytokinin, produced shoots and roots, with or without callus formation. Shoot development was'best on transfer to medium lacking phytohormones. Histological examination of shoot formation revealed that initiation of the process began early in culture by division of epidermal and subepidermal cells. This led to the formation of nodular tissue (meristemoids), some of which developed subsequently into leafy vegetative shoots.

Wood of 66 Eucalyptus regnans F. Muell. trees aged 4 to 17 years, from the North and the South Islands of New Zealand, was sampled for basic density and moisture content. Four bole positions (base, 1.4 m, half height, and threequarters height) were sampled. Average basic density and moisture content values were 395 kg/m³ and 174% (North Island) and 398 kg/m³ and 164% (South Island) respectively. Basic density increased up the tree from 1.4 m to three-quarters height, but moisture content showed the opposite trend. Using regression analysis, the plot mean weighted basic density and moisture content could be estimated within 2% using the 1.4-m disc alone. Basic density generally increased from the pith outward at all sample positions. Trees more than 13 years old had greater basic density and lower moisture content values than younger trees.

In 1977 tests were established of 141 open-pollinated families of selected plus-trees, and also of some unselected trees, of Eucalyptus regnans F. Muell. Several Australian provenances and New Zealand exotic populations were represented. The tests were assessed in June 1980 (3 years from seed sowing) for height growth, resistance to Mycosphaerella leaf blotch disease, branching quality, and stem straightness. Frost tolerance was assessed in 1978.

Family differences (including provenance effects) were most pronounced in height growth, disease resistance, and frost tolerance. Phenotypic correlations between traits were mostly favourable, facilitating simultaneous selection of families for fast growth, good frost-tolerance, and disease resistance, as well as improved branching quality and stem straightness.

Based on these early results, a clonal seed orchard has been established from grafts of 8 of the 55 original New Zealand plus-trees and of 34 new secondgeneration plus-trees selected from within the family tests. In addition, a seedling seed orchard has been established using bulked seedling progeny of 30 selected families (23 New Zealand, 7 Australian).

Provenance tests of 36 seedlots of Eucalyptus regnans F. Muell. were established on two central North Island sites in 1977. Frost resistance recorded in the first winter after planting showed highly significant variation among provenances. At age 3 years there were significant differences in height growth, resistance to Mycosphaerella leaf blotch disease, stem straightness, and branching quality.

The most promising native Australian provenances were from southern Gippsland, Victoria (fast growth, good resistance to Mycosphaerella, but comparatively poor frost tolerance), and from interior southern Tasmania (satisfactory growth, reasonable resistance to Mycosphaerella, and excellent frost tolerance).

A New Zealand exotic provenance from Tokoroa performed well. The seedlot was collected from selected trees in a 9-year-old plantation of southern Tasmanian origin.

Thirty-two chemicals were tested for effectiveness against stain, decay, and mould fungi on freshly sawn sapwood of Pinus radiata D. Don. Eighteen of these were quaternary ammonium compounds. The performance of some quaternary ammonium compounds was improved when used in combination with other fungicides or under highly alkaline conditions. None of the chemicals or mixtures which controlled sapstain are currently cost-effective for the New Zealand market when compared with the standard treatments of 0.2% a.i. captafol or 0.5% sodium pentachlorophenoxide plus 1.5% borax pentahydrate.

A weighing lysimeter has been designed which directly measures water loss or gain by an individual tree up to 20 m tall. For a gross load of 2.5 tonnes, weight changes as small as 0.15 kg can be recorded - a resolution of more than 1 in 16 000. On the basis of the ground area occupied by the tree crown, the resolution in evaporation terms is 0.01 mm.

The data accumulated will be incorporated in long-term studies of water use by Pinus radiata D. Don forest.

A Corrigendum to this paper is available here: Design of a new weighing lysimeter for measuring water use by individual trees

Vegetative regrowth was assessed on stumps of Beilschmiedia tawa (A. Cunn.) Kirk (tawa) which had been felled in two early selective logging trials in the central North Island. Live coppice occurred on 53% of stumps 21 years after logging at Pureora (an average of nearly six shoots per stump) but on only 10% of stumps at Kotoehu 23 years after logging (an average of four shoots per stump). Deer browsing has-been observed on new tawa coppice; thus formerly high animal populations in Rotoehu may have contributed to its scarcity there. Assumed mean height-growth rates of 8-12 cm/year are similar to those of seedlings growing under good light conditions. Vegetative vigour is maintained, even enhanced, in larger (and on average, older) trees, and coppice is more likely to develop when subsidiary stems are left on stumps at logging. The value of post-logging coppice shoots as a potential source of future canopy trees, however, may be limited by the presence of well-developed natural regeneration in most tawa-dominant forests.

Pinus radiata D. Don seedlings in a high state of susceptibility to infection by Diplodia pinea (Desm.) Kickx during summer were altered to a state of high resistance through ''winter" preconditioning in growth cabinets. Conversely, seedlings in a high state of resistance during winter became much less so after ''summer'' preconditioning. Preconditioning effects were related to temperature and photoperiod differences. The data support observations that susceptibility of P. radiata seedlings to inoculation with D. pinea fluctuates with season, being high in spring-summer but low in autumn-winter.

Artificial inoculation studies with Diplodia pinea (Desm.) Kickx in the glasshouse and growth cabinet established that initiation of infection (as indicated by the first appearance of stem symptoms) of Pinus radiata D. Don requires a minimum shoot wetness duration of 3 h but no more than 48 h within the temperature range 10°-30°C. Duration of wetness seems important to infection as interruption of the wetness period by a dry period of 12 h or longer reduced the disease level.

Temperature requirements for the initiation of infection and the subsequent development of the disease are not the same. Infection cannot be initiated at 5°C, but at 10°C the level of infection can be high if wetness is not a limiting factor. However, at this temperature lesion extension is limited and dead tops do not develop, even if the temperature is subsequently raised to the optimum. On the other hand, when infection is initiated at a high temperature, e.g., 25°-30°C, lesion extension continues until a large part of the shoot is killed even at a subsequent temperature as low as 10 °C. Thus, temperature and duration of wetness during the early stages of infection largely determine the ultimate level of disease. Briefly, temperatures of 10°-12°C, 15°C, and 20°-25°C or higher during 1-2 wet or humid days would represent respectively, light, moderate, and serious dead top development.

Infection by Phaeocryptopus gaeumannii (Rohde) Petrak was evaluated in second-growth Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) in southern British Columbia, using the percentage of ascocarp-bearing needles as a measure of infection intensity. Infection was appreciable at many locations west of the Coast Range and in the interior mountain ranges in the east (71% of location means 5-100%), but was negligible on the interior intermountain plateau (93% of means 0-4%). Infection was particularly high (74% of means 80-100%) along the west coast of Vancouver Island. Significant positive correlation was found between mean infection and May-July mean rainfall in southern British Columbia. At Cowichan Lake on Vancouver Island provenances and clones from origins west of the Coast-Cascade divide in British Columbia, Washington, and Oregon were significantly less infected (means 0-13%) than those from between the Coast Range and the eastern mountains in British Columbia (29-90%). The relatively high mean rainfall (250-350 mm) during November-January may be a contributing factor towards the heavy infection (80-100%) observed in younger stands in the central North Island of New Zealand.

Three yield trials now 10 to 12 years old have shown that Australia's first radiata pine (Pinus radiata D. Don) seed orchard has produced genetically improved stands. Orchard seedlots produced about 20% more total wood volume, with about twice as many trees of excellent stem and branch quality, than a control seedlot representing not only the population from which the trees in the orchard were selected but also typical commercial seed of the 1980s.

Intensive harvesting operations involving conversion of native forest to plantations, and use of short rotations and/or more complete utilisation of biomass will markedly increase both the rate of nutrient export from sites and the nutrient cost (weight of nutrient per unit of biomass) of biomass production. The nutrient cost is particularly high for young thinnings or when crown components of trees are removed, and is considerably greater for Pinus radiata D. Don than for Eucalyptus, especially for phosphorus and when tree rotations are longer than about 20 years. In addition to the direct removal of nutrients in biomass, significant losses of nutrients may occur as a result of harvesting and site preparation. Such losses are less predictable than removal in biomass, but can be quantitatively more important. Much more research is needed to assist in interpreting the significance of varying rates of nutrient removal to the long-term productivity of forest sites.

On most soils, emphasis should be placed on silvicultural systems which minimise both nutrient losses and any detrimental redistribution of nutrients on the site. In general, introduction of intensive harvesting involving removal of tree crowns and root systems would seem unsuited to the maintenance of productivity on most sites. It may be possible to maintain nutrient supplies by applying heavy rates of fertiliser, but maintenance of acceptable levels of soil organic matter may prove more difficult.

Changes are caused in material on the forest floor and in the underlying soil by various types of machine traffic during ground-based logging operations. The extent, duration, and effect on tree growth of these disturbances vary, but wheeled and tracked machines and operating procedures can be modified to minimise the detrimental effects.

This paper provides a framework within which different thinning systems can be evaluated, taking into consideration both short-term costs (thinning costs) and long-term costs arising from damage and loss of site potential under Swedish conditions.

The paper was previously presented at a seminar on "Mechanisation and Techniques of Thinning Operations" at Nancy in 1979.

Harvesting, the largest consumer of energy in Pinus radiata D. Don plantation operations, is dependent on liquid fuel. While petroleum supplies are expected to be adequate until well into the twenty-first century, real prices for petroleum products are expected to show a steady rise. Assuming a merchantable stem mass of 0.15 tonne/tree and a haul distance of 50 km, mechanised harvesting appears to require considerably more fuel than traditional chainsawbased systems. However, increases in mean tree size, haulage, or worker travel distance, favour the mechanised system. As petroleum fuel accounts for only 11% of total harvesting cost, a number of other operating factors are at least as important as the price of oil, or even more important.

Harvesting systems incorporating (conceptual) continuously moving machines could substantially reduce thinning costs, or facilitate thinning at an earlier age. Such systems could also cause less soil damage and compaction.

Operations research techniques such as mathematical programming, simulation, and the development of planning systems can contribute to decision-making in forestry management. Computers have dramatically changed the possibilities and practice of data collection, storage, analysis, and presentation but the difficulty of obtaining access to them has until recently limited their use. Development of the microprocessor is extending the availability of electronic tools but costs for specialist applications are still high.

Softwood Holdings Limited have developed silvicultural schedules which are varied according to both site quality of the plantation and manufacturing requirements of the Company's processing plants. The median regime involves four thinnings before clearfelling at age 35 years, with a total volume production of 685 m³/ha. It is considered that cost to mill door cannot be isolated from product manufacturing costs and the opportunity to manufacture a broad rangeof products.

Changes in silvicultural practices (for instance, initial spacing, pre-commercial thinning, and row thinning) alter a number of stand characteristics, including average stem size, branching habit, and yield. These in turn exert a direct influence on harvesting productivity and consequently on costs.

A model of various aspects of fertiliser application throughout a 40-year rotation of Pinus radiata D. Don provides a framework with which options on whether to apply fertiliser can be examined at five stages: at establishment, at first thinning (age 16 years), second thinning (age 22 years), third thinning (age 28 years), and at fourth thinning (age 34 years). A yield table developed for Uriarra Forest near Canberra was applied to the framework and an assumption was made that a 40% increase in the relative rate of growth of stands with periodic annual increments of 16-19 m³/ha/year could result from application of nitrogen and phosphorus in the 16 years following establishment, or in any of the subsequent 6 years between harvests. The model was then used to evaluate the extra wood and increase in size of the harvested logs likely to result from fertiliser, and some of the economic aspects.

For a single application, fertiliser at the time of establishment resulted in the most extra wood, and at the last or next-to-last thinning it resulted in the highest internal rate of return on monetary capital invested.

The nature of the N x P interaction for specific soils and stands is likely to be a key factor on the generally phosphorus-deficient soils of Australia.

Soil damage caused by five types of ground extraction machines used in thinning of young stands of Douglas fir Pseudotsuga menziesii (Mirb.) Franco) America during winter and spring was visually assessed. Total area impacted ranged from 11 to 30%, the amount being affected by machine type, thinning intensity, planning and location of skid tracks, and bunching system employed. The severity of damage was related to machine type, soil conditions, and number loaded passes. Previous studies indicate that loss in the potential growth of final-crop trees (with resulting increased costs and decreased returns) may result from damage levels similar to those observed. Research to determine growth losses of radiata pine (Pinus radiata D. Don) due to soil damage is recommended.

Storm damage is becoming recognised as a significant problem in the Ovens Zone as the plantation area expands, because stands with about 1600 stems/ha on high-quality sites (>SI 27) become increasingly prone to "collapse" once the stand height exceeds 20 m. Commercial thinning before the stands become unstable is not feasible because yields are quite low (60-75 m³/ha) and piece size is small (0.05-0.08 m³). Harvesting systems for such areas need to be specially designed to operate economically at these levels. Systems are also needed to handle smashed and tangled material until new silviculture aimed at providing more stable stands becomes effective.

In the long run an approach to control appears to lie in the promotion of low "slenderness ratios", i.e., the ratio of stand height to mean diameter (in damaged stands typically in excess of 100). Lower slenderness ratios and hence more stable stands are achievable by wide initial espacements and by early non-commercial thinning. There appears, however, to be no silvicultural means to regain stability in the dense unthinned stands which are already in excess of 20 m stand height.

Examination of relations between stocking or thinning and the incidence of wind damage by uprooting or the bending and breakage of stems showed that stocking and thinning strategies can reduce the risk of damage in plantations of Pinus radiata D. Don. Except on sites where root growth was very restricted, plantations raised at lower stocking generally experienced markedly less wind damage. The risk was increased, however, immediately after a thinning, especially if the retained trees were tall and slender, and the thinning had been heavy and had removed dominants. These influences were explained by the long-term effect of stocking on tree development and by the immediate effect of thinning in opening the canopy to the wind.

Reduced stocking greatly increased stem diameter and crown and root growth, but had little or no influence on the height of the dominant trees, except at extremely high or extremely low stockings. The height/diameter (H/D) ratio was thus greatly reduced at lower stocking. The H/D ratio, calculated from the mean height and diameter at breast height (1.3 m) over bark (d.b.h.o.b.) of the 200 largest diameter trees/ha, was identified as a valuable index of the risk of wind damage, at least with respect to stem failures. It was found that H/D values are influenced by growth at various stockings and after various thinning regimes. The most important conclusion reached is that trees should be allowed as much growing space from as early in their life as can be reconciled with other silvicultural and economic constraints.

A Corrigendum to this paper is available here: Effects of stocking and thinning on wind damage in plantations

There are four types of cable yarders in current use in south-east Queensland plantations of hoop pine (Araucana cunninghamii Ait. ex D. Don) on terrain classified as "unconventional" because standard equipment and methods are not suitable. This classification is important both economically and from a forest management point of view. Cable yarding also has environmental advantages over crawler skidding.

Current skyline productivity is 5-6 m³/productive hour and is affected by such things as topography, whether the sky lining is uphill or downhill, organisation of racks and landings, and crew training.

Nine thinning trials involving four types of hauler have been carried out on steep country to date. The data from these trials indicate likely production levels for a range of piece volumes, extraction distances, and methods. Changing the crop layout, and introducing more suitable haulers along with appropriate working techniques, are seen as two avenues for significantly increasing production and reducing unit volume costs.

Machine productivity, damage to the retained trees, and degree of site disturbance in a delayed first-thinning operation were measured in a preliminary study during 5 working days in August 1980, in a stand of 18-year-old radiata pine (Pinus radiata D. Don) in the Merriang Plantation on slopes in excess of 50% (26.5°). The average daily productivity measured during this short study was compared with records from operations on a range of slopes in the locality. Skid tracks constructed prior to the study were not included in productivity calculations, though the cost of these tracks was only 4% of the total cost of the operation. There was no evidence that slope had a substantial effect on productivity but further detailed studies, over a comprehensive range of slope classes and sites, are necessary. During the steep terrain thinning study 17% of retained trees were damaged, though for radiata pine this is likely to cause only a minor loss in value of the final crop. In the study area 25% of the soil surface was disturbed; however, the combination of stable soils and frequent cross-drainage of skid tracks should minimise the likelihood of significant soil erosion.

A highly mechanised harvesting system was studied in 1976 to establish likely production rates. It was estimated that the system had the potential to produce 300 m³/day at a direct cost on truck of NZ$4.33/m³ (compared with NZ$6.15/m³ from a motor-manual operation) but monitoring of the system disclosed a much lower production level than anticipated, probably because of lower utilisation than expected. In a second study utilisation of the feller-buncher was only 42%, and the system production level 160m3/day (estimated cost NZ$12.50/m³ on truck). When the system was studied again for 5 weeks in January-February 1979, feller-buncher utilisation had improved to 67%. As this machine was the lead machine in the system, production improved significantly and the cost per cubic metre was competitive with costs from a motor-manual operation.

Because of the need to carry out major overhauls of the machines and the availability of a more abundant supply of labour for motor-manual operations, the system was closed down in 1979.

The Kockums system, incorporating a feller-buncher, two limber buckers, and two forwarders, was used in a fifth thinning of Pinus radiata D. Don. This system is a satisfactory form of mechanisation in P. radiata thinning when the merchantable volume of the trees being removed is greater than 0.25 m³.

In reviewing and updating cutter productivity figures applicable to New South Wales, a new system involving two complementary levels of study has been developed, encompassing both detailed time-study and gross data approaches.

A detailed time-study was done on a sample of 12-13 cutters with varying experience and ability, and productivity levels were related to tree size. The gross data collected showed a wide range in daily and long-term production levels. The 72 tonnes/week predicted as feasible from the detailed time study was actually achieved by only one cutter.

A gross data system could be used for monitoring productivity under a range of forest conditions, without necessarily establishing what those conditions are.

Increases in productivity in the felling component of wood harvesting in Pinus radiata D. Don plantations in the south-east region of South Australia during the period 1975-81 provide evidence that the introduction of fully mechanised felling systems can be delayed during the next decade. Reasons for the gains achieved include productivity aids such as the felling bench used in first thinnings. Continuing increases in productivity will be essential to maintain existing motor-manual systems in harvesting operations in South Australia.

In a study of physical workload in a delayed second-thinning operation, average energy output was 1.8 MJ nett/hr. Heart-rate analysis indicated a high load, with no significant difference in physiological cost between various job elements. In a second study two techniques for motor-manual thinning were evaluated - the bench and the traditional technique for trimming and handling felled stems. Simulation of job elements identified stacking as the most strenuous with an energy output of 49 kJ nett/min for the traditional technique and 39 kJ nett/min with the bench technique. The bench technique results still came within the very heavy physical effort range of the British Medical Association's standards.

Both studies provide evidence that productive motor-manual felling in Australian plantations still entails very heavy to extremely heavy physical effort. A high to very high physical working capacity is therefore considered essential for this type of forest work.

Changes in harvesting technology in Australia have been characterised by both the training of a more skilled work-force and the introduction, on an operational basis, of fully mechanised means of harvesting small thinnings. The range of opportunities to sell smallwood has led to considerable divergence in silvicultural practice. Rising costs of handling small thinnings and poor market conditions for these products in some areas have encouraged the development of silvicultural schedules which minimise smallwood in commercial operations. Tasmania and Western Australia have tended towards policies that embrace the more radical approaches stemming from New Zealand, while other States have maintained more conventional schedules.

The limited extent of the remaining "old crop" resource planted in the 1920s and 1930s, and the low level of planting between 1935 and 1955, will lead to a period of wood supply constraint in the 1980s. This will be followed by a substantial increase in production from the mid-1990s. The resulting constraints on industrial expansion, and the large age-class which might supply commercial thinnings have led to a review of silvicultural practice. There is a wide range of thinning and pruning regimes currently being practised in New Zealand, as exemplified by those of the four major growers in the Rotorua region.

Other significant developments have been the application of fertilisers after commercial thinning, and the establishment of the Radiata Pine Task Force to study the effect of management regimes on value outturn in relation to a range of processing options.

Review of "Eucalypt dieback in forests and woodlands", edited by K.M. Old, G.A. Kile, & C.P. Ohmart.

Oxygen-delignified kraft, kraft-anthraquinone (kraft-AQ), and soda-AQ pulps from Pinus radiata D. Don were bleached with oxygen-based and chlorine-based treatments. Oxygen-based bleaching employed ozone (Z), alkali extraction (E), and peroxide (P) treatments in previously optimised ZEP and ZPZP sequences. Chlorine-based bleaching was with a conventional sequence. Comparative information was gathered on the effects of bleaching on pulp yield, viscosity, beating requirements, handsheet strengths, and brightness stability.

In general, the responses of the three alkaline pulps were similar for each bleach sequence though bleached soda-AQ pulps had slightly lower brightnesses. The yield advantages of AQ-additive pulping were preserved after full bleaching. Except for lower chemical demands with ZPZP bleaching, no noticeable differences were found between the effects of ZEP and ZPZP bleaching. Both sequences reduced pulp viscosity, pulp beating requirements, and handsheet tear and burst properties. In comparison, chlorine bleaching resulted in higher pulp viscosity and increasing pulp strength levels mainly because of enhanced handsheet tear properties, but had no effect on beating requirements and resulted in less stable brightnesses.

The fungicidal efficacy of a number of alkylammonium compounds has been compared in a simulated above-ground decay test against brown- and white-rot fungi. All the compounds tested were at least as active as copper-chromearsenate (CCA) against brown-rot fungi in softwood but only compounds of the dialkyldimethylammonium halide type proved to be highly active against white rot in hardwood. Over-all thresholds for the didecyldimethylammonium salts were less than 0.8 kg/m³ compared with approximately 1.6 kg/m³ (salt basis) for CCA.

Wood species had a marked effect on the efficacy of tertiary amine salts against Gloeophyllum trabeum (Pers, ex Fr.) Murr. With Pinus radiata D. Don (radiata pine) as substrate the threshold was approximately 1.6 kg/m³, whereas with southern yellow pinef the threshold was greater than 3.2 kg/m³. However, wood species had little effect on the threshold with didecyldimethylammonium chloride.

Ten posts of New Zealand-grown Pinus sylvestris L. (Scots pine) were treated with a copper-chrome-arsenate (CCA) preservative by the Bethell process, to the Timber Preservation Authority (TPA) Commodity Specification C3 at a commercial plant.

Analysis of discs taken from the treated posts showed that all samples exceeded the minimum TPA requirements for copper penetration and retention in the sapwood zone. There was no significant difference between actual copper retentions (by analysis) and theoretical retentions calculated from solution uptakes and solution strength, which indicates that Scots pine is a very satisfactory species for treatment with CCA preservatives.

The Shigometer technique purports to detect decay and other timber defects in living trees. The presence or absence of a defect is predicted from measurements of electrical resistance recorded at intervals along a small-diameter, radially drilled hole.

The technique lacked any predictive ability when applied to Nothofagus fusca (Hook, f.) Gerst, (red beech) and the evidence that the technique reliably detects decay in other species is shown to be inconclusive.

Increment core and wood disc samples were collected from 10 Pinus radiata D. Don (radiata pine) trees in each of four age-classes in Kaingaroa State Forest in the central North Island. The samples represented (a) young thinnings (12 yr), (b) two stands which had received silvicultural treatments (24 and 34 yr), and (c) an unthinned old-crop stand (52 yr). Intensive measurements were made of green density, basic density, moisture content, tracheid length, and resin content.

Over the 40-year age span covered, the average wood properties changed considerably, e.g., green density 1025-815 kg/m³, basic density 325-420 kg/m³, moisture content 215-95%, tracheid length 2.5-3.5 mm, resin content 3.3-2.9%. Average values were calculated for sawlogs, top logs, sawn timber, and slabwood. It is concluded that the change in raw material supply from untended old-crop to thinnings and produce from intensively managed stands will be accompanied by age-related changes in intrinsic wood properties, to which industry will have to adjust. For instance, logs will be heavier because of a higher average moisture content, but will nevertheless have a lower basic density.

This individual-tree distance-dependent growth model predicts the diameter, height, and crown height development of a simulated plot of Pinus radiata D. Don trees. The model provides estimates of stand development within approximately ± 5% but fails to predict mortality of small suppressed trees adequately. Further refinement of the mortality and diameter increment function of the model will provide more accurate diameter and height distribution data.

Superphosphate fertiliser was applied at various rates to plots of phosphorus deficient Pinus radiata D. Don (radiata pine) in four forests in the Auckland area. Soil analyses showed that most of the plots had a low level of extractable phosphorus (Bray & Olsen) prior to fertiliser application. Foliar phosphorus concentrations remained deficient in the controls but were raised to adequacy by fertiliser in the treated plots. Analysis of the growth response was made difficult by the lack of replication within all sites, but a series of partial statistical analyses strongly indicated that height growth was positively affected by fertiliser. On more fertile sites the fertiliser acted to maintain a high site index while on less fertile sites site index was improved. Large growth improvement was obtained at the lowest rate tested (625 kg superphosphate/ha). Higher rates gave little further increase in growth. Basal area growth was also increased by fertiliser. The higher rates (1250 and 2500 kg/ha) generally gave greater growth than the lower rate (625 kg/ha) but each increase in amount brought a smaller increase in basal area growth.

Forest floor organic matter and nutrient contents were quantified in 41 first-rotation and seven second-rotation stands of Pinus radiata D. Don (radiata pine) growing in the North Island. Most of the stands were between 18 and 21 years of age.

The forest floors contained an average 20.7 tonnes of organic matter/ha and 258, 18, 32, and 33 kg/ha of nitrogen, phosphorus, potassium, and magnesium, respectively, but there was considerable variation both between and within forests. Ridge and stepwise multiple regression techniques were used to construct models which explained 70, 58, 62, 79, and 82% of this variation. Stocking levels, rainfall, minimum temperature, and foliage calcium levels were the most important variables. The second-rotation sites contained on average twice as much organic matter and nutrients as the first-rotation sites. This was attributed to the fact that no slash burning or clearance had been carried out at the end of the previous rotation.

The forest manager can thus make significant changes to forest floor dynamics through policies on thinning and slash treatment.

Three separate studies showed that New Zealand populations of Pinus radiata D. Don possess useful quantitative genetic variation in resistance to infection by the fungus Dothistroma pini Hulbary. Heritability of resistance was high enough under suitable conditions to allow effective selection and breeding resistance.

In the first study, 66 "resistant" trees were phenotypically selected in heavily diseased New Zealand plantations in 1966; 21 of these subsequently retained strong measure of resistance when clonally propagated by cuttings. However, only five clones were judged acceptable in growth, branching, and stem straightness.

In the second study, clonal variation in resistance to natural infection by fungus was sharply exhibited in hedged clonal archives from 2- and 3-year-old second-generation ortets (originally selected for growth and stem quality, not for resistance). Although closely related hedged clones sometimes differed considerably in their susceptibility to infection, there were still significant mean differences in the susceptibility of families, attributable almost entirely to general combining ability effects of the parents. Variation in susceptibility was also strong among hedges of clones aged 18-23 years. The third study showed dramatically that there were marked genetic differences among 5-year-old trees in resistance to infection under natural inoculation in the field. The study involved a diallel cross among 25 seed orchard clones. General combining ability effects were very strong, while specific combining ability effects were negligible. Individual full-sib families ranged from 3% to 69% in proportion of progeny badly infected.

The strong additive genetic variation and potentially high heritability in resistance within current breeding populations of P. radiata, already improved growth and stem quality by intensive selection and breeding, augurs well for successful incorporation of needle blight resistance into future breeds via traditional general-combining-ability seed orchards.

Trees in a trial plantation containing eight cypress varieties were examined for cypress canker disease. Three fungi were associated with the disease - Seiridium cardinale (Wagener) Sutton & Gibson, S. unicorne (Cke & Ell.) Sutton, and Pestalotiopsis funerea (Desm.) Steyaert which occurred mainly in combination with one of the other two fungi. The percentage of trees from which cypress canker fungi were isolated differed with the variety: x Cupressocyparis leylandii (Jacks. & Dall.) Dall, clone Haggerston Grey 18%; clone Naylors Blue 0%; clone Leighton Green 17%; clone Green Spire 8%; Cupressus macrocarpa Hartw. 22%; Cupressus torulosa D Don 0%; Cupressus arizonica Greene 9%; NZ FRI clone 850-329 (probably C. arizonica x C. torulosa) 8%.

An inoculation trial showed that S. cardinale consistently caused more damage on all varieties than S. unicorne, while P. funerea was a weak pathogen of secondary importance. Differences in susceptibility to S. cardinale were detected: the four x Cupressocyparis leylandii clones and Cupressus macrocarpa were the most susceptible; C. arizonica, C. torulosa, and FRI 850-329 showed some resistance. No differences in susceptibility were detected to S. unicorne or P. funerea.

A 130-year-old pole stand in which over 90% of the trees and the basal area were Agathis australis Hort, ex Lindi, (kauri) was estimated to include 10 t foliage/ha, 17 t branches/ha, and 105 t stems/ha in the tree layer. The foliar nutrient concentrations suggested deficiencies of both nitrogen and phosphorus. The trees contained 187 kg N/ha, 27 kg P/ha, 391 kg K/ha, 511 kg Ca/ha, 56 kg Mg/ha, 32 kg Mn/ha, 0.1 kg Cu/ha, and 2.2 kg Zn/ha. Energy values ranged from 19 kJ/g for dead branches to 22 kJ/g for older foliage.