The behaviour of radiata pine (Pinus radiata D. Don) latewood fibres and latewood fibre networks in unstrained, strained, and ruptured wet webs at 22 to 32% solids were examined using light microscopy and scanning and transmission electron microscopy. Visible changes with pulp beating and web straining were examined with reference to fibre morphology, fibre collapse, fibre fibrillation, fibre orientation, and web consolidation.

Extensively kinked and twisted unbeaten latewood fibres were irreversibly straightened in a strained wet web. Beating treatments fibrillated fibre surfaces and produced fines which formed interfibre fibrillar networks in wet webs. These fibrillar networks were progressively disrupted as wet webs were strained to rupture. Disrupted fibrillar material aggregated about individual fibre surfaces.

Stems from 25-year-old radiata pine trees, grown on the same site, were examined to determine the effects of moderate and heavy thinning on growth rate and several wood properties.

Thinning caused a greater proportion of the volume increment to be accumulated near the base of the stem and effected a temporary decrease in log form. At the time of clear felling, 15 years after the first differential thinning, the heavily thinned stems had a mean tree volume 28% greater than the moderately thinned controls but there was no significant difference in log form. The mean percentage of heartwood was similar in both crops.

Wood density and tracheid length levels were reduced by thinning but there were no significant differences between treatments in tree mean densities at age 25 years. Compared to older unthinned stands of the same mean diameter, the regimes examined here resulted in wood of 8% to 10% lower density and estimated tracheid lengths shorter by 10% or more.

Compression wood formation was found to be related to the rate of growth after thinning and occupied up to 20% of the volume increment of the bottom log for the first 5 years following treatment. This was not associated with increased eccentricity in the stems, but appeared to be a response to the changed environment, possibly through increased auxin production or as a direct result of increased wind sway.

The effects of non-commercial and production thinning during the rotation of a commercial forest plantation are discussed. Such factors as log size, tree size and stand volume are considered briefly to emphasise the relative profitability of a management regime is a function of all costs and all benefits. The enhanced future value of the residual stand is a major benefit from all thinning.

Economic analysis, using simulation to compare alternative management regimes, confirms non-commercial thinning to be profitable relative to delayed thinning. Production thinning might be even more profitable if done before intense stand competition develops.

If, late in the rotation, there is no thinning then dense stands result, with intense competition on the dominant trees. Production thinning then could be beneficial, sustaining crop tree growth and resulting in both profitable and silviculturally desirable management.

Regression analysis of two sets of sample branches indicated that branch sample position within the crown affects the relationships between branch size and the weights of needles and wood material. Clonal variation was statistically significant in equations for predicting needle weight. Traditional methods of estimating crown weights from branch size underestimated actual weights in an independent set of sample trees. The degree of underestimation was small for wood plus bark, but as large as 19% for foliage weights. Correcting estimates for bias in the regression technique only partially compensated for the discrepancy in foliage estimates. The remaining bias was apparently due to the effect of branch position in crown on estimating equations. However, incorporating the relative height of the branch within crown in regressions led to overcompensation with weight estimates up to 21% above actual weights.

Stem tissue samples from young radiata pine (Pinus radiata D. Don) trees growing in the forest were collected at intervals throughout one annual growth cycle, and the amounts of indole-3-acetic acid (IAA) and abscisic acid (ABA) measured. The amount of IAA increased in late winter but was otherwise not well correlated with cambial growth patterns. ABA content fluctuated during the summer in apparent response to seasonal moisture stress and showed some correlation with cambial growth.

Within plantations of radiata pine in the south-east of South Australia, variation in the soil type appears to have a greater effect on litter accumulation than variation in site productivity. Differences in litter accumulation are probably related to differences in rates of litter decomposition rather than litterfall. Relatively large accumulations of litter are found on most sand dune soils in the region, and this could contribute to problems of continuing site productivity on them.

Infection of radiata pine (Pinus radiata D. Don) by Dothistrorna pini Hulbary was studied at all combinations of four different temperature regimes (day/night temperatures: 24/16°C, 20/12°C, 16/8°C, and 12/4°C) and four leaf wetness periods (8, 24, 48hr, and continuous moisture). Germination of conidia, although favoured by higher temperatures, did not vary greatly between treatments. Successful infection occurred under all treatments and was greater on foliage more than one year old than on foliage less than a year old. Strornata appeared sooner with higher temperatures and longer leaf wetness periods. The incidence of infection, however, increased greatly under continuous moisture at 20/12°C and, to a lesser extent, at 24/16°C. No other significant differences between treatments in incidence of infection were detected.

Rhyssa lineolata (Kirby), a native of North America, was found in New Zealand in 1955. It parasitises Sirex noctilio F. and was initially the most plentiful rhyssine emerging from logs taken from forests in which it had been found. Although the total level of parasitism appears unchanged, R. lineolata has since been almost completely superseded by the closely related Rhyssa persuasoria (L.). Adult R. persuasoria begin emerging a few weeks earlier than R. lineolata, and this seems to give them a competitive advantage.

Between 1959 and 1964 R. lineolata was liberated in nine forests but has not yet been recovered from any of them. It has, however, spread naturally to five forests in the southern half of the North Island. The furthest of these are 240 km apart.

R. lineolata was exported to Tasmania in 1962 for insectary breeding and field release.

The forests of the Grey River headwaters are ecotonal between the mixed podocarp and large-leaved hardwood forests which prevail further south in mid- Westland, and the Nothofagus forests which prevail further north. At low altitudes, in the south and west of the survey area, the dominant species are kamahi and Quintinia acutifolius, with some rimu, miro, kahikatea, Hall's totara, southern rata and mountain cedar. At high altitudes mountain cedar, pink pine, Dracophyllum traversii, Olearia ilicifolia and O. lacunosa dominate. In the north and east the dominant species are red beech, silver beech, and mountain beech. The sub-alpine shrublands are of more uniform composition and are dominated by Dracophyllum longifolium, D. uniflorum, Phormium colensoi, Podocarpus nivalis, and leatherwood in places.

The forests and shrublands were divided into 17 associations by using a numerical procedure. The composition, structure and habitat of each is described. The influence of ungulates (particularly red deer) and of opossums on each association and on sub-units of the survey area was determined by considering the susceptibility of the vegetation to browsing, the extent of modification in the vegetation resulting from past use, and the pattern of use at the time of the survey. It was found that in most cases the seral lacebark-broadleaf and kamahi-broadleaf associations were the most susceptible to the ungulates, were the most modified from the original condition and were also receiving the greatest ungulate use at the time of the survey. The sub-alpine shrub associations were generally the least susceptible, the least modified and were receiving the least ungulate use. The kamahi-dominated associations were the most susceptible to opossum damage and were receiving the greatest opossum use at the time of the survey, while the Nothofagus forests were the least susceptible and were receiving the least use.

The areas most susceptible to ungulate damage were in the south where the forest was predominantly mixed podocarp and large-leaved hardwood and the least susceptible were in the north where Nothofagus species dominate. The areas where the vegetation was most modified by ungulates were the Crooked and Haupiri Catchments and the Elliot Range while the least modified were in the vicinity of Mt Te Kinga, around Bald Hill and in the Upper Grey. Ungulate use at the time of the survey was greatest in the Crooked, Haupiri and Upper Grey Catchments and least around Mt Te Kinga and Bald Hill. The most susceptible areas to damage by opossums were in the south and at the time of the survey opossum sign was most evident in the Crooked and Haupiri Catchments and in the vicinity of Mt Te Kinga.

Reciprocal grafting of Sitka spruce (Picea sitchensis (Bong.) Carr.), white spruce (P. glauca (Moench) Voss), and Norway spruce (Picea abies (L.) Karst.) was carried out so that young and old scion material of each species occurred on rootstocks of all three species. Most mortality took place in the first 18 months; half or more of the ramets bearing young material survived for 5 years regardless of combination. Survival of ramets involving old material was generally poor, although 60% of old Norway spruce scions survived on white spruce stocks, and 40% of old Sitka spruce scions survived on Norway spruce stocks.

Coning began in the fourth year on three old Sitka scions. Norway spruce rootstock reduced the number of branches per ramet, but no significant effect of rootstock on height or diameter was detected. Foliar nitrogen and potassium concentration of young material was related to scion species, but foliar calcium concentration was related to stock species.

Inter-specific grafting within the genus Picea is possible although definite rootstock effects have so far been small.

Vegetative propagation, in theory and in practice, offers advantages for research in several areas of forest biology. It also has a direct practical application in the use of rooted cuttings or other forms of vegetative propagules in afforestation. The most severe difficulties which presently prevent these theoretical advantages from being realised are associated with phase change and maturation of apical meristems. Many of these difficulties can be avoided by propagating from very young trees, or by manipulating clones to keep some members in the juvenile phase of growth. These latter can continue to serve as donors of vegetative propagules which will have a consistent stage of maturation at the time of planting.

This paper reviews the natural distribution and the genetic variability of Norway spruce. The variation is sufficient to allow the selection of physiologically distinctive clones which, after vegetative propagation, can be established on a number of divergent sites and used for phenological observations.

The climate of the European Alps is extremely variable and an understanding of it in connection with the physiological behaviour of provenances will prevent many reforestation problems.

The possibility of an inverse correlation of sexual and asexual reproduction of Cryptomeria japonica, suggested by the poor flowering of good-rooting clones, was investigated on three sets of suitable data. Clones with most reliable'data showed such a relationship to be moderately strong. When forestwide data were analysed, no relationship was found, but tests of skewness and expected crown-cone bearing relationship raised questions of whether flowering and rooting records were adequate for the individual trees used. The data suggest that use of good-rooting clones should be discouraged in seed orchards if they show poor flowering ability.

Two or more vegetative propagules per clone can provide estimates of genotypic and phenotypic variances and covariances in populations, and of the genotypic values of parent trees. When planted on several sites they can provide information about genotype-site interactions. In theory, at least, vegetative propagules from a set of clones can provide information far more efficiently and/or precisely than a set of seedling progenies. But this information, unless applied to a situation where vegetative propagation is used to produce planting stock, can be seriously biased by such factors as topophysis and non-additive gene effects. Topophysis, which is often irreversible, may be circumvented by the clonal replication of young seedlings. Cuttings are normally much more suitable than grafts for providing genetic information.

In some regions of Japan, Cryptomeria and some other conifers have long been propagated by cuttings. This has resulted in the differentiation of cultivars in these localities, since vegetative propagation reduced genetic diversity and increased the number of ramets of certain genotypes when foresters recognised that some morphological traits indicated the superiority of the genotypes. The problem of "varieties" was the principal concern of Japanese silviculturists during the earlier half of this century.

The planning of tree improvement programmes was also influenced by the practice of vegetative propagation and the existence of cultivars. Selected plustrees of Cryptomeria japonica were prescribed to be propagated by cuttings, and it was expected that the best clones of them would be designated as new cultivars after clonal tests. This objective has, however, been abandoned because uniformity of planting stocks, involving lack of genetic diversity, is not necessary or desirable in silviculture. Even when mixed clones are planted foresters will easily select their favourite clones out of the mixture.

Vegetative propagation by cuttings is a useful tool in the study of forest genetics, but it is not prudent for a tree improvement project to employ ramets of a limited number of plus-trees directly in commercial forestry.

This paper reports the results, during the first 5 years after planting, of a field trial designed to compare the growth of seedlings with that of grafts and cuttings taken from ortets of different ages.

The difference in size at age 5 could be attributed mainly to differences in the size of the trees at planting. However, the calculation of relative growth rate (RGR) values, and the correction of these values for covariance on tree size, enabled growth rates to be looked at independently of planting size. The corrected data for the fourth and fifth years then showed that (i) grafts had lower RGRs than cuttings, apparently because of graft incompatibility; (ii) during the first three years the seedlings had higher RGRs than cuttings.

The use of cuttings, rather than seedlings, in a plantation establishment programme will lengthen the time from planting to canopy closure. Information is not yet available on growth effects subsequent to that time.

Selections were made of 216 trees of radiata pine (Pinus radiata D. Don) in 6-year-old stands, from which rooted cuttings were propagated and planted in a clonal test. Assessment of growth rates and morphological characters at age 6 years from setting has provided estimates of clonal differences, clonal and phenotypic correlations between characters, and predicted gains from selection on clone means.

Differences between clone means and clonal repeatabilities were substantial and therefore predicted gains from reselection on clone means were high for most characters, especially growth rate. Comparisons of rate of height growth between seedlings and cuttings gave some indication that cuttings have a lower growth potential than seedlings. The clonal correlation between growth rate and branch diameter was high, indicating the difficulty of selecting small-branched yet fast-growing clones.

Fifty of the clones were repropagated from ramets in the first test and a second clonal test was planted. Assessment of the second test at age 2 years from setting gave preliminary indications of poor repeatability of results between the two tests.

A possible way of maintaining high repeatability of growth rate in successive repropagations would be to maintain hedges of all clones. Before a clonal programme is applied to afforestation it is essential to verify that select clones retain their superiority through repeated repropagations.

This paper is concerned with the nature of the improvement that can be obtained from using cuttings in forestry. Potentially, this improvement represents both gain in the characters under selection and greater uniformity in the tree crop.

One experiment involved both Sitka spruce and Norway spruce. In each species cuttings of eight clones and a population of seedlings were planted and studied during a three-year period. Each clone was highly uniform in date of flushing. With respect to height growth and stem form, however, the clones did not show consistently greater uniformity than the seedlings.

In the other experiment a 29-year-old clonal planting of Norway spruce was compared with seven 16-year-old seedling families for height, diameter, and branching habit. In this material the effects of competition, and of the duration of the competition, appear to have had an over-riding effect on variability between trees.

A programme, originated in 1972, for selecting, vegetatively reproducing and testing nursery stock of black and white spruce in Ontario is described. Height, diameter and branching habit are the criteria used for selection. Results of experiments in terms of rooting and field performance will provide information on effectiveness of selection, the clonal repeatability and total genetic variation of certain characteristics, prior to selection of the best clones for large scale propagation.

Scions from seven sources were grafted onto seedlings of one full-sib family of radiata pine (Pinus radiata D. Don). The object of the trial is to obtain data on juvenility/maturation and incompatibility effects, particularly the differential diameter growth of stock and scion. Ten months after establishment, grafts with scions of one-year seedlings showed the best survival and height growth.

Propagation of Norway spruce (Picea abies (L.) Karst) by cuttings, begun experimentally on a small scale in 1962 at the Foundation for Forest Tree Breeding in Finland, was greatly expanded in 1969. The object is to evolve a method capable of producing planting stock in amounts large enough for forest establishment. At present rooting takes place in two plastic greenhouses which are automatically ventilated and irrigated. One of the greenhouses is also provided with a heating system. The material used in the experiments consists of the best individuals selected from young progeny tests with spruce. Rooting has been successful during the past years, increasing to 95% of a total of some 150,000 cuttings in 1972.

The successful development of cutting propagation of Norway spruce (Picea abies L. (Karst.)) now makes breeding programmes involving large scale vegetative propagation of younger stock plants economically feasible.

In Lower Saxony, propagation is carried out in plastic green-houses, and the costs per cutting are roughly 30% above the costs of seedling plants. Selection of elite clones is undertaken from a very large number of seedlings, and about 21,000 clones with 400,000 plants are being tested at the present time. Clones which have already been through two selection stages are immediately handed over for use in practical forestry.

Experiments show an estimated genetic gain in growth rate of 40%, from synthetic multiclonal varieties, compared with the population mixtures normally used for afforestation. In comparison with selected provenances, the gain would be approximately 20%.

Especial value is attached to the maintenance of genetic variation in the synthetic varieties in order to withstand dangers which may arise, partly from the early age of selection (up to 20 years).

Segments (2.5-cm-long) of Populus nigra L. obtained from etiolated axillary branches did not root in water or auxin alone, but rooted in 0.5% ribose, glucose and sucrose and more profusely with 0.1 mg/L in dole-acetic acid (IAA) or in dolebutyric acid (IBA) added to the medium. 5-fluorodeoxyuridine (FUDR), 5-fluorouracil (FU), actinomycin-D and cycloheximide inhibited rooting. The deoxyribonucleic acid (DNA), ribonucleic acid (RNA) and protein contents of segments cultured in glucose plus IAA were higher than in water or in glucose/ IAA solutions containing cycloheximide or actinomycin-D. New isoenzymes of peroxidase and IAA-oxidase developed in solutions containing IAA and glucose, as did two new low-molecular-weight RNAs. New isoenzymes also developed in solutions containing actinomycin-D and cycloheximide. The physiological significance of these facts is discussed, and a biochemical explanation for the root initiation process is proposed.

Stem cuttings of Populus robusta Schneid, were treated with 0, 10 and 100 mg/L each of indole-3-acetic acid (IAA), indole-butyric acid (IBA), triiodo- benzoic acid (TIBA) and carbolic acid (CA) at the apical and basal ends after 0, 7 or 14 days. Observations on rooting, callus formation and callus differentiation were recorded. Auxins increased rooting, the effect being more marked with IBA than IAA, and when applied on day 0 rather than after 7 or 14 days. Callus was formed at the apical end of the cuttings by treatment of that end on day 0 with water or any other regulatory substance. This also occurred when the basal end was treated with TIBA or CA. The amount of callus decreased with a delay in time of treatment. Callus developed on almost the whole length above the soil when cuttings were treated with 100 mg/L IBA at the apical end, and below soil level when cuttings were treated at the basal ends. In contrast to this, callus formed by IAA remained confined to a small part of the end to which it was applied. While callus formed at the apical end by IBA differentiated into roots, that produced by TIBA or CA differentiated into shoots. The number of differentiating cells increased when the treatment was repeated. It is considered that callus is produced at a time when differentiation of cambial derivatives is not able to keep pace with cell-divisional activity and that a proper balance between the supply of auxin and assimilates is needed for organogenesis. A high sucrose to auxin ratio leads to the production of phloem, and a low sucrose to auxin ratio to xylem, which is necessary for vascularization of root primordia. A schematic representation is proposed of the possible, self-catalysing and self-perpetuating mechanism that may be involved in callus formation and its differentiation into xylem and phloem, and thus to the production of roots or shoots.

The review compiles and discusses literature concerning the metabolism of carbohydrates, nitrogen, nucleic acids, and proteins during adventitious root initiation and development. In addition, the review includes discussion of approaches to the study of metabolism during adventitious root initiation, and proposes potentially productive areas for future research.

Interpretation of the actions of auxins and auxin synergists on adventitious root primordium initiation and development suggests that cellular dedifferentiation that leads to primordium initiation requires one or more enzymatically synthesized auxin-phenolic conjugates. The "predisposition" of cells in easy-to root tissues to initiate root primordia apparently resides partly in the availability of active enzymes and substrates necessary for synthesis of the conjugates. On the other hand, difficult-to-root tissues lack necessary active enzymes or substrates, or both.

The paper reviews and interprets selected literature concerning the locale of formation, time of development, histological origins, and histological and cytological changes that occur during adventitious root initiation and development in twigs and branches of gymnosperms and dicotyledons.

Seasonal changes in rooting promoters and inhibitors of stem cuttings of radiata pine (Pinus radiata D. Don) were followed and the influence of various environmental parameters on rooting examined. Hormonal changes occurred with season, but these are complex and are not yet well understood. Depletion of metabolic food reserves is considered to be important in determining health and survival, as rates of net photosynthesis of cuttings rapidly approached zero immediately after detachment and remained so until the cuttings had rooted. Alleviation of moisture stress is critical to rooting of cuttings and high humidities are required for at least the first week after setting. Cuttings take up water through the cut base of the shoot, through the basal foliage left in contact with the soil and probably through foliage wetted by dew or rain. Air temperatures of 20 to 25 °C during the day provide rapid rooting, and it is thought that cold night temperatures of 5 to 10 °C are advantageous. Photoperiod does not appear to influence rooting.

Further work is required to determine how pre-severance conditions influence the quality of shoots used as cuttings and to examine the effect of soil temperatures and night air temperatures on rooting performance. In the application of the results of this study the discussion concentrates on low-cost installations for use in forest nurseries to speed up and improve propagation.

A review of the world's literature indicates that almost all parts of a plant can be induced to form callus if given the proper stimulus. For some plants the callus can be redifferentiated to form shoots and roots. For others, it is possible to initiate embryoids. There appears to be no reason why forest trees can not be propagated by means of tissue culture.

Tissue culture of Eucalyptus stems and lignotubers is described, and the responses of calluses to various auxin-cytokinin modifications of the culture medium are summarised. Regeneration of plants from such calluses was not achieved. A cultural mixture of Eucalyptus callus and regenerating tobacco callus did not induce regeneration of Eucalyptus.

Organ culture of E. grandis is described. Axillary bud development and root development was most frequent in nodal explants at the basal end of seedlings, particularly with foliated explants. Successful root initiation and development of plants from nodal cultures has also been achieved with older (up to 7 month) E. grandis trees, using a culture medium with 5 x 10^-6M indole-butyric acid. These plants had more than 50 nodes, and these organ cultures were initiated from nodes considerably higher than the 15th node "barrier" experienced with classical methods of propagation.

Cell and tissue cultures offer the prospect of adding traits and producing genetic combinations which could not be obtained by sexual crossing. This would involve mutation, transcession, transduction, transformation, and somatic cell hybridisation. In vitro methods can also be used in forestry for preservation of gene resources, production of homozygous specimens, prediction of phenotypic expression, production of disease-free specimens, study of host-parasite relations and study of mycorrhizae. It is concluded that the techniques of cell and tissue culture have considerable scope for altering the genetic quality of trees.

Rooting cuttings is often difficult, and alternative methods of vegetative propagation should be considered. A number of herbaceous plants have been propagated effectively using various techniques of tissue and organ culture. For tree species the potential of tissue and organ culture is evident, but success so far has been limited. Cell-suspension culture may potentially be the best method for large-scale propagation of tree species. There are a number of problems associated with this technique, however, that may take several years to solve. In vitro culture of buds, although missing some of the advantages of cell-suspension cultures, may become a practical method of vegetative propagation for most tree species, much sooner and with less research effort than cell-suspension culture. It therefore deserves immediate consideration.

Tissue and organ cultures are good techniques for studying the physiology of root initiation and growth. Much of the knowledge gathered in this manner will help to improve methods of tree propagation, not only by tissue and organ culture but also by conventional rooting of cuttings.

A review is made of the principal methods used for the vegetative propagation of chestnut (Castanea spp.). Results obtained by classical grafting, nursery grafting, topworking and budding are reported, as well as those from special techniques such as nurse seed grafting, juvenile tissue grafting, inverted radicle grafting, and layering. For stooling, the stage of growth of shoots is discussed as well as the effect of maleic hydrazide and the effects of etiolation caused by wrapping shoots with aluminium foil. For cuttings, the effect of juvenility, ageing, auxins and growth inhibitors are examined. The physiology of rooting is discussed, and the content of growth promoters and growth inhibitors in different types of cuttings is reported. A possible relationship is also suggested between the rootability of cuttings, their anatomical features and their content of growth promoters and growth inhibitors.

All methods of vegetative propagation can be applied to birches. Both summer and winter cuttings will root but the winter cuttings take longer. Hormones are useful in stimulating rooting. In addition, birch can be rooted by layering. Virtually all methods of grafting can be applied to the birches. Following grafting suitable scions will flower quickly and produce large quantities of fruit.

Scions from selected trees of Eucalyptus saligna differed in survival following grafting. The best grafting method was the side graft and the worst was budding. Both the cleft and splice methods of grafting provided some degree of success.

Physiologically juvenile softwood cuttings have been successfully used to vegetatively propagate individual trees from ten genera of commercially important hardwoods from the southeastern United States. They arise from epicormic buds, and the lower on the bole that the suppressed buds are released, the greater is the chance of favorable rooting response. Stump or root collar sprouts are preferable but forced epicormic branches from the lower 4 to 6 m of the bole also give good results. The diurnal temperature fluctuation and the difficulty of maintaining rooting media temperatures between 20 °C and 28 °C are two problems encountered in propagation of rejuvenated material from mature forest trees. With our present biological information and rooting technology the vegetative propagation of softwood cuttings from the crown of mature forest trees remains extremely difficult for most species.

Sycamore (Platanus occidentalis L.) cuttings, 1.2 m in length, were planted horizontally at depths of 7 and 15 cm to test this type of placement in the establishment of closely spaced plantings. Sprout origin and survival were observed during the first growing season, and sprout growth and root characteristics were observed in late autumn of the first, second and third year. Sprouting was influenced primarily by bud position. Buds facing downward seldom produced sprouts and most sprouts arose from buds nearest the apex. Neither planting depth nor cultivation affected the amount of sprouting, but both influenced time of sprouting. Cultivation to control competing vegetation was necessary for satisfactory survival and growth of young sprouts. The pattern of root development was influenced by number and position of sprouts, by depth of planting, and by cultivation.

Progress and problems in vegetative propagation of important North American hardwoods are reviewed with emphasis on rooting cuttings and the application of propagation techniques in breeding research. Some problems in rooting physiology are discussed.

Approach grafting, top-cleft grafting, bottle grafting and patch grafting as applied to Eucalyptus deglupta Blume in Papua New Guinea are discussed. Repeated failure of the stock occurred in methods other than patch grafting. It is postulated that an inhibitor of the stock is caused by adult scion material. Lines of further research on incompatibility are suggested.

Patch grafting, when applied to seed orchard work, is sufficiently well developed and cheap enough to be used effectively.

The effects on rooting ability of cuttings of Eucalyptus deglupta Blume of position in the seedling stem and ontogenetic age are described. In cuttings taken from 3-months-old seedlings position of the cutting on the shoot system had no effect on rooting or subsequent growth. Cuttings rooted very freely when taken from upper parts of trees up to 12 months old and they appeared to grow exactly like seedlings. Corresponding material from trees aged 5 years and more completely failed to root. Stem cuttings of E. deglupta were used as bioassay materials to test extracts from tissues of various ontogenetic ages. Responses were clear-cut, and indicate that the failure of cuttings from older trees was due to a rooting inhibitor.

A technique for rooting large numbers of cuttings is described. Almost 100% success in rooting is achieved after 8 weeks in a misting cabinet.

The rooting capacity of a total of 107 Salix taxa was tested. Most taxa rooted readily in two types-over the entire cutting surface, or concentrated at the lower end. Rooting was normally rapid, taking place in 15 to 18 days. Easy to-root species rooted when cuttings were one or more years old, but poorly rooting species survived only when older and thicker cuttings were used. Cuttings of almost any size can be used. No difference in type of rooting was related to the sex of the parent.

Grafting of Eucalyptus grandis has not been successful in northern New South Wales because of delayed incompatibility. Attempts to root cuttings from seedlings and coppice shoots from the bases of older trees have been moderately successful.

Past experience and current research on the rooting of sweetgum cuttings (Liquidambar styraciflua L.) is scanty. Sweetgum is a difficult-to-root species. Better results have been obtained with root cuttings than with shoot cuttings. Rooting success seems to vary with growing season and age of the tissue. A current study shows promise in certain combinations of root stimulants, shoot growth inhibitors, fungicide and sugar.

Plantations of most of the economically important forest species in India are usually established with seedlings, either by entire transplanting of nursery stock or by stump planting. Willows (Salix spp.) and poplars (Populus spp.) are the only forest trees which are widely planted as shoot cuttings. However, rooting of cuttings is also practised to propagate, on a small scale, Bursera penicillata (Sesse et Moc. ex D.C.) Engl., Morus alba L. and a few other forest tree species. Bamboos, which are an important forest component, are widely propagated by vegetative means. With forestry becoming more intensive the interest in vegetative propagation has increased. This has prompted laboratory and field studies, to improve existing techniques, and to extend vegetative propagation to other species, e.g., teak (Tectona grandis L.f.). This paper outlines methods already in use, and reviews the research on vegetative propagation which has been done at Dehra Dun and elsewhere in India.

A method of rooting Platanus x acerifolia Willd. cuttings with a heel gave 60-80% success, as compared with 20-50% success with simple stem cuttings; the latter method was more economical of material. Mean annual height increments were about the same with both methods, i.e., 75-80 cm.

Seven provenances of Japanese larch which had been studied for their adaptability to local conditions in previous experiments were tested for their rooting ability as cuttings. The influence on the rooting process of the morphology and physiology of the cuttings is demonstrated as well as the role of the substrate and the physical and ecological conditions of the chamber in which the cuttings were raised. With a cuvette specifically designed for the experiment CO₂-measurements of root respiration were carried out to follow the progress of the rooting. A method is given for low cost mass production of Japanese larch by vegetative propagation.

Rootability studies of eastern white pine (Pinus strobus L.) cuttings taken from 17-year-old ortets showed, contrary to previous work, that cuttings taken in June consistently rooted best. Optimum concentration of indole-butyric acid (IBA) varied with the date cuttings were taken. With 0.1% IBA treatment, about 60% of cuttings taken in June rooted; with 0.4% IBA, about 50% of cuttings taken in May rooted; with 0.8% IBA, 42% of cuttings taken in April rooted. Cuttings taken in June produced significantly more roots than cuttings taken in other months. Approximately 60% of cuttings were rooted within 16 weeks when collected in May and June and treated with a suitable concentration of IBA + Benlate. On cuttings taken in June there was a positive correlation between the number of roots per rooted cutting and the number of young shoots. High mortality was observed in those cuttings with many young shoots. The results suggest that June cuttings with a medium number of young shoots are best for propagation. These findings make propagation by rooted cuttings practical for this species.

Rooting of brachyblast cuttings (i.e., cuttings originating from needle fascicles) is a promising technique of vegetative propagation which can be applied to pines. The technique has some advantages in obtaining larger amounts of cutting material from a selected individual and easier rooting than the normal shoot cuttings. The latter advantage is considered to be due to the higher level of growth-promoting substances contained in brachyblast cuttings.

Because numerous factors influence rooting and early growth of spruce (Picea spp.) cuttings, only the most important ones are mentioned in this paper. The factors considered are: species, population, individual, age of ortet, position of cutting on the tree and branch, type and length of cutting, time of year, chemical treatment, rooting medium, and temperature of the air and of the rooting medium.

Cuttings from most mature Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) can be rooted with fair success (average 15%) if they are collected in the autumn, treated with in dole-butyric acid and Benlate fungicide, placed in a heated rooting medium (20°C) with no air heating and kept well watered in a humid atmosphere. Clonal variation in rootability is considerable and year-to-year variation has also been found. Cuttings from trees that will not root under these conditions may be induced to root if grafted to cuttings from seedlings. A simple outdoor propagation structure for rooting of cuttings is described.

Rooting of current-year shoots (length 12-20 cm) from lateral branches of 5 to 10-year-old Scots pine (Pinus sylvestris L.) in a greenhouse under intermittent mist, at the end of May or early June, gives very variable results. The best clones in a favourable year root with a percentage of ca. 70% in about 15 weeks. Generally many cuttings die from attack by the fungus Botrytis cinerea and by rotting of the basal and apical parts of the cutting. Botrytis can be controlled very well with a weekly treatment of 83% captan (1.5 g/L water) or with 50% euparene (2.5 g/L water).

To prevent rot relatively dry conditions are necessary during the propagation period. Cuttings from normal shoots however need much water during times of high temperatures. Cuttings from shoots developed from needle fascicles (length 8-10 cm, inserted at the end of July or early August) are preferable in this respect. Other advantages of these fascicle cuttings are that they generally produce more roots per cutting, can be hardened off more easily and give a better shaped plant.

A technique of air-layering and subsequently deep-planting 20-month-old grafts has been developed as a practical method of propagating 20- to 35-year-old plus trees of eight pine species. The method has been used successfully to preserve incompatible clones and to produce ramets of these for seed orchards. Various modifications of technique were tried to improve the rooting rate of scions but yearly variation in environmental conditions appeared to be more important than any of the treatments. Success rates of more than 90% should be attainable with a controlled environment. It is relatively easy to induce roots to develop from rootstock tissue at the graft union and further experimental work is needed to assess the value of this.

Wood specimens were taken at breast height from trees of radiata pine (Pinus radiata D. Don) which forked near ground level. From three trees on each of three sites specimens from major and minor stems were compared ring for ring. The specimens were examined for average tracheid length, spiral grain, maximum, minimum and average density, and latewood ratio. Overall no differences were demonstrated between major and minor stems for these characteristics.

Small samples of Pinus radiata D. Don were broken by applying transverse tensile forces at a variety of strain-rates in order to determine the effects of strain-rate, moisture content, and tracheid structure on the morphology of the surfaces produced during the fracture. Microscopical examination of the surfaces showed that all three variables were of importance. In saturated earlywood, the proportion of tracheids broken in transwall failure increased as strain-rate was increased, and reached 55% at the highest strain-rate of 10²sec^-1. In air dry earlywood, 20% of the tracheids were broken at all rates, and in latewood fewer than 5% of tracheids were broken at both moisture contents and at all strain rates.

The physical properties of Corsican pine (Pinus nigra, Arnold) were examined using increment cores and wood discs from 41 sites. Two main classes of stand were sampled:- (1) Grown from seed imported from overseas in the 1920s; lots HO 26/1, HO 27/27 and HO 28/112. (2) Second generation stands; i.e., from seed collected in New Zealand; lots NM 46/427 and NM 47/451. Apart from the age differences between the two groups, variation between seedlots was found to be small, probably due to the fact that crops grown in New Zealand seem to be of mixed var. calabrica and var. austriaca origins. Wood density was consistently higher than that found in other commercially grown exotic conifers, and outerwood densities were observed to decrease with increasing altitude and latitude. A strong correlation was found between outerwood density at breast height and tree mean density. Resin content was very high, particularly in the heartwood, where it was over 20% in individual stems; this will affect the economics of pulping the older crops. However, heartwood development commences late and progresses slowly. Tracheid lengths were intermediate between those previously found for radiata pine and lodgepole pine.

The condition, status and trend of populations of opossums (Trichosurus vulpecula Kerr) in the Hokitika River catchment and its tributaries were evaluated to assess the need for, and likely effect of, control campaigns.

Records of the history of infestation were examined. Fat reserves of males and females, growth rates, theoretical asymptotic weight of adult females, percentages of breeding animals, second breeding cycle, start of the breeding season and density were determined.

The opossums in the headwaters of Hokitika, Mungo and middle left of the Whitcombe catchment were in good condition; population density is high and is expected to increase further. Control operations in the Hokitika-Mungo headwaters are likely to be effective in reducing opossum numbers and protecting vegetation. In the headwaters and left bank of the Whitcombe, condition was very good and density very low, but expected to increase rapidly. In the rest of the area, animals were in fair condition, with moderate and generally declining densities.

Phytophthora heveae Thompson was isolated from discoloured sapwood and root tissue of unthrifty kauri (Agathis australis Salisb.) trees and from soil from affected and healthy stands. Laboratory tests showed that the fungus is capable of killing kauri seedlings.

The inclusion bodies of the cytoplasmic virosis of Selidosema suavis (Butler) are equilaterally triangular in profile and have mean vertical height of 1.93 μm, s.e.m. 0.05 μm. The non-occluded virions are 59 nm in diameter.

The inclusion bodies of two isolates of the nucleopolyhedrosis viruses found infecting Heliothis ( = Helicoverpa) armigera (Hübner) are square in profile. The dimensions of the polyhedra and the virions of the two New Zealand isolates are given. The epizoology of one New Zealand isolate is discussed.

Forest products exports from New Zealand to Australia increased in free on board value from NZ$22.7 million to $29.8 million in the first five years of Nafta. Sawn Douglas fir timber was the only commodity to increase markedly in trade volume, though initial failure to grade compromised these exports. Both as a proportion of total Australian forest products imports and as a proportion of New Zealand exports, New Zealand forest products exports to Australia fell. The reverse trade decreased in value. When devaluation and inflation are allowed for, the net increase in trade is negligible. Future expansion is likely to come from deals between the monopoly pulp and paper suppliers.

New Zealand would do better to develop an efficient wood growing industry rather than to rely on tariff preferences in Australia. Forest processing industries should be exposed to world competition as the best incentive for achieving greater efficiency.

Christmas Island ‘C’ phosphate ore (0, 52, and 104 kg/ha P) was compared with ordinary superphosphate (52 kg/ha P) in a fertiliser trial in 7-year-old radiata pine (Pinus radiata D. Don) regeneration growing on P-deficient soil in Maramarua Forest. Growth response and foliar P level confirmed that a soil phosphate deficiency existed, and indicated that the response was related to P availability, and that even the most effective treatment (104 kg/ha P as the ore) was insufficient for optimum growth.

It was estimated that 30% more fertiliser ore (67% more P) would be needed to produce the same volume of wood as the particular superphosphate treatment. There was no indication that the phosphate ore was a longer-lasting source of P.

Christmas Island ‘C’ phosphate ore shows promise as a fertiliser for trees on acid clay soils. However, at present its potential is limited because it is not available in a form suitable for distribution from the air.

The ability of soil tests for extractable phosphorus to predict height growth and fertiliser requirements of radiata pine (Pinus radiata D. Don) seedlings at time of planting in the field was examined.

The Bray 2 and Olsen tests proved to be the most satisfactory of the tests examined for predicting height growth of radiata pine seedlings on unfertilised soils. The correlation coefficients improved as the length of the growth period considered was increased from 1 to 3 years after planting. The Bray 2 test accounted for 60% of the variability in 3-year height growth of seedlings. A value of 12 ppm P was found to correspond to minimal 3-year height growth on fertile soils.

However, none of the soil P tests examined or other soil parameters (pH, silt, clay, P retention, bulk density, and loss on ignition) proved useful for accurately predicting the response of seedlings over a 3-year period to 85 g of superphosphate applied, at time of planting, on an individual seedling basis. Superphosphate requirements ranging from 170 g per seedling when the Bray 2 test shows less than 3 ppm of P to nil when the Bray 2 test shows more than 12 ppm were tentatively deduced.

Earlier work expressing quantitative relationships between the growth of radiata pine (Pinus radiata D. Don) and environmental influences generally is reviewed. On the basis of a survey of 132 sites, selected to represent a maximum range of New Zealand climates, this paper then analyses the influence of over 50 site variables upon the periodic volume increment of individual dominant trees. After the effects of age had been removed, the following variables accounted for over 66% of the remaining variation: mean annual precipitation, seasonal rainfall distribution, effective soil depth, total nitrogen and available (Olsen) phosphorus in the topsoil, and the seasonal departures of ambient temperature from postulated optima of 5°C at night and 20° during the day.