New Zealand is a large, isolated, oceanic, temperate, continental fragment - characteristics that have resulted in a distinct but depauperate flora also lacking virulent forest pathogens. This grand isolation has protected its native forest from any obvious natural incursions by pathogens, while affording a similar protection to the large array of exotic tree species that have been imported since the arrival of European colonists in the early nineteenth century. What is unique about the biological, social, technological, and economic factors that have historically afforded this protection? Have these factors undergone rapid change in recent years, and as a consequence is New Zealand becoming more vulnerable to border breaches and invasion by forest pathogens? Where are the most likely sources of these pathogens? And what of the enemy within? Do we harbour sleeper pathogens" that may explode as the mitigating nature of these controlling factors changes? These questions were addressed in recent research programmes that evaluated (1) the importance of suspected pathways whereby foreign biota could breach New Zealand's border, (2) the recognised north-south and east-west dispersal patterns of historical pathogen invasions, and (3) an example of a "sleeper pathogen" Phaeophleospora eucalypti (Cooke & Massee) Crous, F.A.Ferreira & B.Sutton"

Puccinia psidii. Wint. is a very unusual rust with an extremely wide host range within the Myrtaceae. The fungus currently occurs only in South and Central America, the Caribbean, and Florida, where it causes disease of both indigenous and introduced species. The hosts of most economic importance are Eucalyptus species, grown as plantations on a very large scale, especially in Brazil. The rust is a serious threat to tropical, sub-tropical, and possibly temperate plantations in Australia, and in other regions world-wide. In Australia, there is an additional threat to native vegetation as many communities are dominated by Myrtaceae. A collaborative project between Australia, Brazil, and South Africa aims to assist in the management of the disease by screening a wide range of myrtaceous genera for susceptibility to the disease, mapping areas in South America, Australia, and other areas globally in eucalypt-growing regions for potential disease hazard, and developing molecular tools for detecting the presence of P. psidii in seed, pollen, and other germplasm. A total of 26 Eucalyptus species of many provenances have so far been tested for rust resistance, along with four Melaleuca species and one species of each of Angophora, Callistemon, Kunzea, Lophostemon, and Syncarpia. Additional genera across the main groups of the family are currently being screened for susceptibility. Hazard maps, which can be used as a measure for evaluating risks associated with germplasm movements have been generated for South and Central America and Australasia. In addition, a highly sensitive detection system has been developed by which rust contamination has been detected in samples of asymptomatic vegetative eucalypt material, seed, and pollen, and on the surfaces of clothing and equipment.

During the last century, the tree populations of Europe suffered from a number of serious epidemics resulting from the introduction of pathogens from abroad. Currently the principal approach to minimising the risk of introducing further exotic pathogens is through Pest Risk Analysis (PRA) in which measures are devised to prevent potentially dangerous pathogens from using their likely pathways of arrival. A relevant example is provided by Ceratocystis fagacearum (Bretz) J.Hunt, the cause of oak wilt in eastern North America, which was subject to critical evaluation in the 1970s and 1980s. Beneficial consequences can flow from such an exercise but the longevity and large size of trees may mean that crucial information can be obtained only from a research programme that takes many years to complete. Moreover, there are other difficulties with the PRA approach when it comes to forestry. Firstly, most forest pathogens are classified using morphological criteria which are inadequate for the recognition of differences critical to the ability to cause disease. This means that the occurrence of a named organism in Europe does not mean that there is nothing to fear from further introductions of what is said to be the same species: witness the bitter experience with the fungi now identified as two species - Ophiostoma (Ceratocystis) u1mi (Buisman) Nannf. and O. novo-ulmi Brasier. Secondly, the PRA approach results in the development of highly specific quarantine measures which are likely to leave loopholes" that unrecognised pathogens can use. There must be many organisms with great potential for damage in Europe that are living in ecological balance with their host trees in other forest regions of the world and thus can never be identified as candidates for a PRA. Therefore there is a strong justification for a quarantine philosophy that recognises the value of nonspecific control measures for certain types of imported material - in particular, for unprocessed wood"

Interest in importing unmanufactured wood products into the United States increased significantly in the late 1980s. The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) has lead responsibility for import regulations and quarantines for plant and animal products; the USDA Forest Service has lead responsibility for managing forest pests and minimising their impacts on federal lands in the United States. USDA APHIS and the Forest Service collaborated to provide the technical information needed for the development of sound import regulations for potential wood imports. The Forest Service established a team of forest entomologists and plant pathologists to develop pest risk assessments at the request of APHIS. This team adds experts depending on the specific risk assessment needs and situation. Assessments have been completed for logs and/or wood chips from Russia, New Zealand, Chile, Mexico, and South America. An assessment is under way for imports from Australia. These assessments have looked at a number of tree species. The Forest Service and APHIS have developed a pest risk assessment process to identify risks associated with the importation of unmanufactured wood articles. This process is similar to International Standards for Phytosanitary Measures developed by the United Nations Food and Agriculture Organisation, but with modifications to meet areas of concern peculiar to wood imports. APHIS issued regulations in 1995 specifying universal requirements for importation of unmanufactured wood products. They use the pest risk assessments to determine if modifications to these regulations are required

In Australia large areas of forest have been closed to industrial forestry and it is necessary to compensate for lost production. Future wood products will come from intensively managed silvicultural regimes -eucalypt regrowth forest and plantations. Solid-wood regimes involving high-cost operations such as pruning and thinning will be economically sensitive to downgrade due to various types of stem defect-fungal and insect damage, staining, kino veins. In Tasmania, research over the last decade has focused on developing management strategies to minimise stem defect caused by decay fungi in both regrowth and plantation eucalypts. Under plantation conditions neither Eucalyptus nitens (Deane & Maiden) Maiden nor E. globulus Labill. shed branches efficiently. Retention of dead branches leads to defects in wood such as large knotty core or loose knots, making the stem unsuitable for either veneer or sawlog. Pruning of green branches at canopy closure and in subsequent lifts shortly afterwards solves this problem. However, on the more productive warm and wet sites there is a high level of decay infections in E. nitens and E. globulus via pruning wounds. We are investigating the complex pathological, physiological, genetic, and silvicultural components dictating eucalypt susceptibility to decay infection and its long-term spread into clearwood including: crown characteristics prior to pruning; growth responses to pruning; growth responses to fertiliser; host resistance and antimicrobial defences; and the identity and pathogenicity of decay fungi. An interdisciplinary approach is fundamental to understanding such questions and also to the succesful development of site productivity models that include predictions of risk and impact of biotic and abiotic damage

Dwarf mistletoes (Arceuthobium spp.) are destructive forest pathogens that parasitise commercially important conifer species. Timber losses result from growth reduction, from wood degradation, from increased predisposition to attack by bark beetles, decay, and sapstain fungi, and ultimately from plantation failure. Research and experience in North America have demonstrated the potential use of hyperparasitic fungi as biological control agents for management of dwarf mistletoes. Although much information is available on the mycobiota associated with dwarf mistletoes, significant research and development are required for these to become operational tools. The most promising biological control agents are Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. in Penz. and Neonectria neomacrospora (C.Booth & Samuels) Mantiri & Samuels which attack shoots and berries, and the endophytic systems of dwarf mistletoe. The use of these two hyperparasitic fungi as potential biological control agents for management of dwarf mistletoes is under investigation. The development of an effective and efficient biological control strategy will reduce the impact of dwarf mistletoes on timber production in areas where traditional silvicultural control, such as retention silviculture or partial harvesting systems, is not practical

Research with Mycosphaerella spp. on eucalypts has been historically and strongly focused towards taxonomical species descriptions, extension of host, and geographical range. To date there is insufficient information to develop management prescriptions that can be applied operationally. The research concept we have adopted is an integration of empirical studies (detection, impact, epidemiology, and physiology) and designed experiments that provide a knowledge base from which models can be developed and validated. Our empirical studies and designed experiments from a core response to current industry priorities in Australia

Native Hawaiian forests are characterised by a high degree of endemism, including pathogens as well as their hosts. With the exceptions of koa (Acacia koa Gray), possibly maile (Alyxia oliviformis Gaud.), and, in the past, sandalwood (Santalum spp.), forest species are of little commercial value. On the other hand, these forests are immensely important from a cultural, ecological, and evolutionary standpoint. Forest disease research was lacking during the mid-twentieth century, but increased markedly with the recognition of ohia (Metrosideros polymorpha Gaud.) decline in the 1970s. Because many pathogens are themselves endemic, or are assumed to be, having evolved with their hosts, research emphasis in natural areas is on understanding host-parasite interactions and evolutionary influences, rather than disease control. Aside from management of native forests, attempts at establishing a commercial forest industry have included importation of several species of pine, Araucaria, and Eucalyptus as timber crops, and of numerous ornamentals. Diseases of these species have been introduced with their hosts. The attacking of native species by introduced pathogens is problematic - for example, Armillaria mellea (Vahl ex Fr.) Que?l. on koa and mamane (Sophora chrysophylla (Salisb.) Seem.). Much work remains to be done in both native and commercial aspects of Hawaiian forest pathology

Pinus kesiya Royle ex Gordon plantations are of major economic, social, and environmental importance to the Lam Dong province of Vietnam. Pine wilt symptoms and dead trees are found in pine plantations at various locations. A systematic survey was needed in order to identify the nematode and its vector, the Japanese sawyer beetle Monochamus altematus Hope, and to evaluate the incidence and severity of the disease. The health status of the trees (disease incidence) was evaluated by measuring the amount of oleoresin exudation after holes were punched in pine stems. Experimental plots within pine stands were typically 400 m2. Disease incidence was assessed as 36.5%, 46.4%, 47.9%, and 48.0% in Lang Bian, Phi Lieng, Cam Ly, and K'Long K'Lanh respectively. The death rate of pine trees increased annually and was dependent on the density of plantations. Yearly losses in the high density plantations were higher than in the lower density plantations. Nematodes extracted from wood samples were identified as a species of Bursaphelenchus. The recovery of nematodes from affected trees varied between specimens collected from different locations. The highest densities of nematodes were found in samples collected at K'Long K'Lanh and Cam Ly. Based on the morphological characteristics of adult sawyer beetles, all were identified as the Japanese sawyer beetle. Sawyer beetles have two emergence periods each year, the first lasting from the end of March to early July and the second from September to the end of October. The largest numbers of adults emerged at the end of April and at the end of September. Stems of 3-year-old Pinus kesiya were inoculated with cultured nematodes and the pathogenicity of the Bursaphelenchus sp. was demonstrated.

Acacia mangium Willd., Eucalyptus spp., Tectona grandis L.f. (teak), Hevea brasiliensis (Willd. ex Adr. Juss.) Mu?ll. Arg. (rubber), Paraserianthes falcataria (L.) I.C.Nielsen, and Gmelina arborea Roxb. (yemane) are the main tropical hardwood plantation species in South-east Asia. The occurrence of heart rot in acacias has received widespread attention but root rot is the most damaging disease of acacia plantations. Eucalypts face a different disease threat where outbreaks of leaf and shoot blights are most destructive. Teak, on the other hand, faces few disease threats although it has many insect pests. Since the 1980s, rubber has gained popularity as a source of timber (rubberwood or heveawood) and timber clones have recently been developed. The pathology of rubber is well understood and documented but the disease susceptibility of the new timber clones is currently unknown. In P. falcataria plantations gall rust appears to be an emerging threat. Yemane plantations in some parts of the world have failed due to disease problems, but no serious diseases threaten the South-east Asian plantations at present. Small plantations of other exotic and indigenous hardwood species have also been established throughout South-east Asia. Overall, comprehensive information on the pathology of many of the hardwood plantation species that have been planted in South-east Asia is lacking. Further co-operation, in particular from international agencies, needs to be continued and strengthened to ensure the success and continued productivity of hardwood plantations in South-east Asia for the betterment of local communities and economies

This feature section contains 10 papers which provide information on a wide range of forest diseases on many different forest trees. Topics covered include: pathology of tropical hardwood plantations in Southeast Asia; status of pine wilt nematode in Vietnam; forest pathology in Hawaii; Mycosphaerella leaf diseases of temperate eucalypts around the southern Pacific Rim; biological control approach for management of dwarf mistletoes; interdisciplinary approach to the study and management of stem defect in eucalypts; pest risk assessment of wood imports into the USA; protecting Europe's forests from known and unknown pathogens; guava rust in Brazil; and the biosecurity of New Zealand forests

In New Zealand there are currently 1.59 million hectares of plantation Pinus radiata D.Don. Further expansion of the plantation resource in this country may have to occur outside the most suitable growing regions, while some existing plantation areas may undergo significant climatic changes. Therefore, species alternatives that have additional climatic and site tolerances need to be found. In addition, although P. radiata is fairly versatile, its intrinsic wood quality clearly limits product quality. Inter-specific hybrid combinations might provide a wider range of opportunities for wood quality improvement and disease resistance. This could be particularly important for biotic threats such as pitch canker (Fusarium circinatum Nirenberg & O'Donnell). Some hybrids have already been produced and, even though these inter-specific crosses have shown lower viability and in some cases lower post-germination viability than intra-specific crosses, the benefits from introducing new attributes or increasing the range of attributes could still be worth pursuing. However, hybrids also have higher developmental costs in crossing and propagation such that greater complexity in breeding strategy may be required than with their pure-species counterparts. Therefore, pine hybrids in New Zealand need to be targeted to specific outcomes of high value. These priorities are most likely climatic (site- and climate-change related), biotic (extending the current plantation area into drought-, frost-, and snow-prone environments), and risk mitigation against the accidental introduction of biotic threats

The effect of market complexity in North America and New Zealand was evaluated for five species/market combinations. The number of log-sorts was used as the surrogate for market complexity as the trend in the industry is to increase the number of log-sorts to obtain maximum value by producing products that meet the very explicit specifications set by log buyers. The results of our study suggest that theoretical value-recovery increases sharply as a few log-sorts are added but then flattens out as the total number of log-sorts increases above five. The effect of the number of log-sorts on piece size and number of pieces handled, variables known to affect production and costs, was inconsistent between species/market combinations

The effect of boron (B) nutrition on some wood properties of Pinus radiata D.Don was assessed on 8-year-old trees from a boron fertiliser study at Ashley Forest. Wood samples were taken at breast height (1.4 m). There were significant differences between samples from control trees and those treated with boron fertiliser, with regard to lumen diameter and cell wall thickness. However, differences in tracheid length were only marginal. Cell wall thickness in the samples from boron-treated trees was greater by 35% in carlywood and 25% in latewood. Cell lumen diameter was greater by 29% in earlywood and 46% in latewood. From these results it was evident that application of boron fertiliser produced an increase in both tracheid cross-sectional area and wall thickness. Furthermore, during microtomy the sections from the control samples tended to check radially, indicating possible differences between control and boron-treated trees in the microstructure and composition of wood cell walls. The staining of control sections with toluidine blue and phloroglucinol was consistently less intense than in the sections from boron-treated trees, and the differences in the staining intensity observed were pronounced enough to suggest that boron may have an effect on the lignification of wood cell walls

The five fungi recorded in this paper have not been previously described from New Zealand. The fungi are: Corticolous Ascomycota: Nectria fuckeliana C.Booth on Pinus radiata D.Don. Caulicolous Ascomycota: Ophiovalsa betulae (L.Tulasne and C.Tulasne) Petrak on Betula pendula Roth. Caulicolous anamorphic fungi: Coryneum betulinum Schulzer on Betula pendula; Fusarium merismoides Corda on Acmena smithii (Poiret) Merrill and Perry, Corokia cotoneaster Raoul, Cotoneaster sp., Hoheria sp., Paulownia tomentosa (Thunberg) Steudel, Podocarpus totara Bennett ex D.Don, Prumnopitys ferruginea (Bennett ex D.Don) de Laubenfels, Sorbus aucuparia Linnaeus. Foliicolous anamorphic fungi: Leptomelanconium australiense B.Sutton on Eucalyptus ficifolia F.J.Mueller

Stands of totara (Podocarpus totara D. Don) have been established in many regions for a variety of reasons including the long-term option of harvesting high-value specialty timber. Thirteen stands of planted totara ranging in age from 10 to 94 years were assessed for performance, and a crude model was developed using eight stands to give an indication of the potential yield. Most were small woodlots that had received little or no after-planting care and two had been planted as shelterbelts. Stands were assessed in the mid-1980s and again 10-12 years later for both height and diameter growth. There was a large variation in growth between individual stands. This reflected major differences in site and climate, stand density, and management history. Height/age curves were developed based on mean heights of stands, and diameter/age curves were constructed using mean stem diameters supplemented where possible with incremental diameters derived from core measurements. Basal area/age and volume/age curves were derived from the height/age and diameter/age curves. Predictions of stand growth for totara based on stands with densities around 1000 stems/ha indicated average height would be 15 m and diameter > 30 cm at age 60 years. Initially, growth in basal area and volume is slow but this begins to increase from about 20 years. Estimated stand volume was 470 m3/ha at 60 years, reaching 800 m3/ha at 80 years. Stand density not only influenced diameter growth but also had an effect on stem form of trees

Upper mid-crown yellowing (UMCY) is a disorder in Pinus radiata D.Don caused mainly by a high potassium/magnesium (K/Mg) ratio in the soil exchange complex and in the tree needles. To study the effects of a range of soil exchangeable K/Mg ratios on potassium and magnesium uptake and UMCY in P. radiata, a trial was established in September 1996 on a Pumice Soil in northern Kaingaroa Forest in the central North Island of New Zealand in a second-rotation stand of 20-year-old P. radiata. The trial tested the effects of magnesium applied as kieserite at 200 kg Mg/ha and potassium applied as potassium sulphate at 200 and 400 kg K/ha on soil-exchangeable and soil-solution magnesium and potassium, on free needle magnesium and potassium, and on severity of UMCY. The applications of magnesium and the two rates of potassium significantly (p<0.05) increased soil-exchangeable and soil-solution magnesium and potassium concentrations respectively in the top 10 cm soil depth during the first 2 years of the trial (1997 and 1998). Magnesium application significantly (p<0.05) reduced the soil-exchangeable K/Mg ratio from 0.7-1.3 (control treatment) to 0.2-0.3, whereas the low and high rates of potassium application significantly increased this ratio to 0.8-1.7 and 1.3-2.5 respectively in the 2 years. The magnesium fertiliser application significantly (p<0.1) increased tree foliage magnesium concentration in 1999, but had no effect on foliage K/Mg ratios in any of the 4 years of sampling (1997, 1998, 1999, and 2002). Potassium fertiliser at the high rate significantly (p<0.1) increased the foliar potassium concentration in 1998 and 2002. Neither magnesium nor potassium fertiliser application had any effect on the change in foliar magnesium, potassium, or K/Mg ratio between 1997 and any of the other years sampled. Individual tree UMCY values ranged from 1 to 6 in a system of increasing severity from 1 to 8. Magnesium fertiliser significantly (p=0.074) reduced UMCY values (assessed in 1997 and 2001) in the 2001 scoring. Similarly, the UMCY value significantly (p=0.055) decreased from 1997 to 2001 for the magnesium fertiliser treatment compared to the control treatment and high potassium rate treatment. Potassium fertiliser application had a significant effect neither on UMCY values nor on changes in UMCY values between 1997 and 2001. The severity of UMCY was not related to the soil-exchangeable K/Mg ratio in spite of the widely different soil-exchangeable K/Mg ratios (0.3 to 2.0 in the 0-10 cm soil depth) produced by the fertilisers. Nor was it related to the foliar K/Mg ratio. The reasons for this could be that the site was not high risk for UMCY during the trial period, the trees were possibly taking significant amounts of potassium and/or magnesium from deeper layers of soil which were probably not strongly influenced by the fertiliser, the amounts of potassium applied were not excessive, and/or the impact of the fertilisers was relatively short-term

The early performance of a selection of establishment trials and general plantings of totara (Podocarpus totara D. Don) and the other major indigenous conifer tree species of New Zealand has been assessed. Only the first 50 years of performance data were considered and these included single and mixed conifer plantings established throughout New Zealand by a range of agencies and individuals on a variety of sites. Examination of a wide range of planted stands of indigenous conifers indicates that totara is the most tolerant of dry exposed sites. It is also the most light- demanding. Despite the large variation in sites and management histories, planted totara consistently grows best on open fertile sites. Average survival of totara is 60%, with a mean annual diameter increment of 6 mm and mean annual height increment of 26 cm, similar to that of rimu (Dacrydium cupressinum Lamb.) and kahikatea (Dacrycarpus dacrydioides (A.Rich.) de Laub.) over the first 50 years of growth. More successful plantations indicate that growth can be significantly greater with a mean annual diameter increment of 10 mm for totara, similar to that of kahikatea and kauri (Agathis australis (D.Don) Lindl.), and a mean annual height increment of up to 55 cm.

Risks, other than those associated with genetic uniformity and reduced genetic diversity, in implementing clonal forestry with Pinus radiata D.Don are often relatively predictable. They include technical and logistical difficulties in large-scale clonal propagation and clonal storage, and difficulties in accurate evaluation of clones. These problems not only impede capture of genetic gain, but they can also compromise the genetic diversity of deployed clonal material. Clones can be lost through failure in propagation and clonal storage systems. Such failure can occur early on, or it can occur through maturation in clonal storage during the clonal testing phase. As well as outright failure of clonal genotypes in clonal propagation and storage systems, general decline in clonal performance and unwanted intra-clonal variability can cause problems. The latter problem, which includes epigenetic effects and possible somaclonal variation, is sparsely reported but very insidious. Careful management of clonal material in large-scale propagation is therefore crucial, control of maturation being a key factor. Clonal testing, though costly, is important not only for testing the performance of individual genotypes, but also for testing clonal uniformity and the quality of clonal planting stock. Clonal testing can be complicated by genotype-environment interaction, and lack of clonal uniformity due to epigenetic effects, with imprecise evaluations compromising genetic gains. These risks can be minimised by fully researched and carefully managed propagation and clonal maintenance systems, together with stringent field testing.

Clonal forestry has great potential advantages for increased genetic gains and crop uniformity. However, it has inherent risks, which must be managed appropriately. Those considered important to Pinus radiata D.Don clonal forestry include risks stemming from reduced genetic diversity through large-scale clonal propagation, and risks stemming from technical and logistical difficulties of clonal propagation and storage, and the evaluation of clonal material. The first category of risks is addressed in this paper; the second category, plus climatic risks, is addressed in the accompanying paper. The widely publicised risks of clonal forestry arise from the genetic uniformity of monoclonal crops and, on a broader scale, from potential restriction in total genetic diversity over clonal plantings. Both these factors are conducive to crop vulnerability to new and serious diseases, a prime hazard for P. radiata in New Zealand. The disease hazard, along with market risks, can be addressed by risk spread in numbers and genetic diversity of clones. This diversity can be achieved by either clonal mixtures or monoclonal mosaics, and must be addressed across landscapes and across age-classes. There are various approaches to quantitative modelling of the risks, to help devise risk-management strategies. Crop failure can be addressed in terms of probabilities. A generalised approach addresses probability distributions for adverse outcomes of varying severity. Less elaborate approaches involve standard errors (which can be applied to clonal under-performance), or the probability of any one clone failing disastrously. Ulterior risks of clonal forestry involve management of the genetic diversity that is needed for long-term breeding, as distinct from safe deployment of current crops. No restrictive regulations exist in New Zealand concerning use of clones, unlike the situation in various European countries, nor is there a local code of practice. Such a code may not only be prudent business, but may also maintain public confidence and forestall restrictive regulations

Clonal forestry with Pinus radiata D.Don hasbeen hampered by maturation (also termed physiological ageing) of clones during the clonal testing phase. In 1988, a long-term nursery trial was initiated to find the best treatment for delaying maturation in rooted cuttings. Clonal hedges were established, hedged annually, and subjected to five different cycles of serial propagation. Physiological age was estimated in the nursery using morphological markers. After 10 years, significant differences were observed between treatments, with the hedged treatment (no repropagation) recording the lowest physiological age of 2.24 years compared with 2.61 years for the treatment with the most frequent serial propagation. In contrast, results from a later assessment of the nursery hedges, and from a field planting of rooted cuttings harvestcd from the same hedges, yielded no statistically significant treatment effects, though significant differences were observed between families and between clones for physiological age, diameter at breast height (dbh), and height. There are some positive aspects of maturation, and this research demonstrated that nursery stool-beds can be managed using hedging to control maturation, keeping physiological age at optimal levels. Despite later non-significant results in physiological age for the different nursery treatments, a trend was still apparent and, therefore, hedging with minimal serial propagation of hedges is advised. There is a conflict between Australasian and North American researchers in terminology regarding physiological age""

The ability to detect statistically significant treatment differences is dependent on the number of experimental units, the alpha level, and the coefficient of variation for the response variable. Some response variables are inherently more variable than others. As variability increases, a greater number of trees per experimental unit or a greater number of experimental units is required if researchers want to avoid making a Type II error (i.e., accepting a false null hypothesis). In this study (containing 20 experimental units), a significant (? = 0.05) treatment effect was obtained for an 8-cm difference in height growth using only 10 Pinus radiata D. Don seedlings per experimental unit. However, when Transplant Stress Index (TSI) means were being analysed, 120 seedlings per experimental unit were required before a difference (of 0.25) was declared significant. Because TSI values are inherently more variable than height growth data, the Type II error rate for TSI in some studies may be higher than the error rate for height growth when plots contain less than 100 pine seedlings per experimental unit (when studies contain 20 experimental units or less)

Veneer peeled from Eucalyptus nitens (Deane et Maiden) Maiden unpruned second logs was segregated into three stiffness classes using an acoustic test. Laminated veneer lumber (LVL) was manufactured using sheets from each stiffness class tested. Strength tests showed that the sheets were successfully segregated by the acoustic stiffness test. The E. nitens LVL had strength and stiffness properties which were higher than those of LVL made from New Zealand-grown Pinus radiata D.Don veneer

Butt logs of 15 trees of Eucalyptus nitens (Dean et Maiden) Maiden, aged 15 years, diameter at breast height 55 cm, were cut into appearance-grade lumber and rotary-peeled and sliced veneer, and the second logs into rotary-peeled veneer. A 1-m billet was removed from between butt and second logs of each tree, as well as discs at successive heights. In addition, breast-height increment cores and breast-height measurements of longitudinal growth strain served to characterise the wood properties and processing, product, and clearwood mechanical properties of each tree. Fibre dimensions, density, and microfibril angle were measured by SilviScan on a sample from height 6 m. Boards were quarter-sawn from the 1-m billet and air- and dehumidifier-dried, and internal checking and shrinkage were measured on these boards and on discs from height 6 m. Sawability" variables of the butt log (viz log-end splits, flitch movement off the saw, timber crook, and timber conversion percentage) showed strong intercorrelations with one another and with longitudinal growth strain, measured at breast height on the standing tree. Amounts of internal checking and collapse in the air-and then kiln-dried butt-log boards were strongly correlated with checking measured on discs and on the billet boards. Shrinkage of the 1-m boards and of blocks from the 6-m-height disc was correlated moderately with collapse and checking in the butt-log boards. Clearwood modulus of elasticity, measured on eight test sticks cut from the billet from height 6-7 m, showed a strong increasing gradient from pith to bark as well as wide variation among trees. Density showed only a small pith to bark increase, while microfibril angle showed a rapid decrease from the pith over the first seven rings. Clearwood modulus of elasticity was moderately correlated with modulus of elasticity of veneer sheets, measured sonically. Tree-mean clearwood modulus of elasticity was strongly correlated with the density/microfibril angle ratio, as was modulus of elasticity of individual test sticks. Trees varied strongly in product characteristics and wood properties, and there were strong correlations (a) between breast-height growth strain and sawability characteristics, and (b) between checking and collapse in butt-log boards and tangential shrinkage and checking measured on discs. This indicated possibilities for genetic selection against growth-stress-related sawing problems and internal checking on drying, the two main deficiencies of E. nitens for appearance lumber. Good correlations of appearance-lumber and veneer properties with similar traits measured on the standing tree or from cores, discs, and a 1-m billet, indicated that effective evaluation of species, provenances, and individual trees is possible without recourse to full-scale sawing studies"

A New Zealand stand of Eucalyptus nitens (Deane and Maiden) Maiden was pruned up to height 8 m and grown for 15 years at low stocking to 57 cm diameter at breast height. This stand provided 15 trees, preselected for a range of wood density. Lumber and veneer were cut from the 5-m butt logs, veneer was peeled from the second logs from height 7 to 13 m, and each tree was evaluated for production of appearance-grade lumber and rotary-peeled veneer. Butt-log quality was good as pruning had effectively restricted the knotty core, and there was little decay from branches in either butt logs or veneer billets. Longitudinal growth stresses varied widely among trees, resulting in log endsplitting and sawlog flitch movement during sawing (spring), which led to crook in sawn timber, substantially reducing timber conversion in some trees. Collapse and internal checking were prevalent in air-dried lumber, and numbers of checks varied widely among trees. Face-checking was found in boards from all trees after kiln-drying and reconditioning, and even those with very few face checks had internal checks. Veneer thickness varied unacceptably, caused probably by incorrect knife-and pressure-bar settings. Veneer splitting also varied among trees, and was worse in butt-log than in second-log veneers. Unsatisfactory pre-heating of billets before peeling may have exacerbated splitting. Knots severely downgraded structural plywood veneer grades, <8% of sheets from the second logs being acceptable compared with 87% of sheets from the pruned butt logs. Stiffness of veneer sheets was successfully measured using a sonic device (Pundit?) to sort veneers for manufacture of laminated veneer lumber

Shrinkage properties, density, and moisture content of 59 trees from three provenances of 10-year-old plantation Eucalyptus globulus Labill. grown at two separate sites in the Mt Gambier region, South Australia, were determined from wood specimens of 20? 20? 90 mm. Microfibril angle (MFA) and cellulose crystallite width (Wcryst), typical routine measurements from SilviScan, were determined from strip specimens that were end-matched with the wood block specimens. Simple and multiple relationships between these properties were examined. The potential of using the SilviScan measurements to predict various shrinkage properties, in particular tangential collapse, was investigated. It was found that several shrinkage properties were significantly correlated with microfibril angle and Wcryst. However, microfibril angle had a direct effect (negative) only on tangential shrinkage and cross-sectional shrinkage, and Wcryst had a direct effect (positive) only on radial collapse. Density, microfibril angle, and Wcryst, either singly or collectively, accounted for a small to modest amount of variation in shrinkage and collapse in both the radial and tangential directions. Total tangential shrinkage was found to be the best single predictor for tangential collapse (r2 = 0.896) and for total cross-sectional shrinkage (r2 = 0.924). These strong relationships held for individual measurements as well as for tree means, and were not affected by positions along the radius

Thirty-six 7-year-old trees representing three families of Pinus radiata D.Don were selected within a replicated block family trial. Stem bolts were taken from three stem positions up each tree - at approximately 1.4 m, and at 50% and 80% of total tree height. The three largest branches in the whorl immediately above each sampled stem bolt were sampled and analysed using the first three branch internode segments, both individually and collectively. A resonance-based system was used to measure dynamic modulus of elasticity (MoE) of branchwood and stemwood green and at 12% moisture content (m.c.). The volume-weighted stem modulus of elasticity and the stem bolt modulus of elasticity at 1.4 m were highly correlated (r = 0.95). Individual branch segments cut from the largest-diameter branch in the whorl immediately above the lowest stem bolt position showed highest correlation with stem modulus of elasticity. Utilising a set of branch segment criteria, the best linear model of stem bolt modulus of elasticity at 12% m.c. ranged between R2 Adj = 0.51 and 0.62, with a residual mean square error (RMSE) varying between 0.36 and 0.42 GPa

Pruning increases value by encouraging clearwood growth. If pruning is delayed the defect core (DC) expands and clearwood conversion reduces. The objective of this study was to examine defect cores within Pinus radiata D. Don stems to determine how well they had been maintained through multiple pruning lifts. Analysis of 4526 currently standing trees suggests that one-fifth of future crop may have defect cores extending 4 cm or more beyond that initially targeted. Furthermore, results indicate that each 1 cm increase in defect core causes an estimated conversion loss of 2.5%, equivalent to a loss in value of $ 10/m3 sawn (ex-mill). For a direct regime on fertile sites, the cost of the expanded defect core is estimated at $880/ha. Bucking may offer the possibility of recovering some lost value. The importance and magnitude of defect cores are further emphasised Through identification of threshold levels of small-end diameter required to obtain clearwood conversions at a given level. This provides a foundation upon which new log grades can be developed

Three species of Lophodermium are reported from pine in New Zealand-the previously recorded L. conigenum (Brunaud) Hilitzer and L. pinastri (Schrad.) Chevall., and the newly reported L. molitoris Minter. All are saprobes with an initial endophytic phase. The North American species L. seditiosum Minter, Staley & Millar is considered a potential threat to New Zealand's plantation forests. Because these fungi are difficult to distinguish morphologically, a simple molecular method was developed to distinguish the four species. After PCR amplification, the ITS* region is digested using HaeIII and HpaII in a single reaction, resulting in unique RFLP banding patterns for each of the species treated. A phylogenetic analysis based on ITS sequences revealed two genetically distinct groups within L. pinastri, one North American and one European. All the New Zealand isolates of L. pinastri tested were identical to the North American group. Further development of the method described here, so that fungal DNA is targeted directly from infected plant tissue, will provide an effective quarantine tool for New Zealand's forestry industry

Agathis australis (D. Don) Lindl. (kauri) seedlings considered to originate from planted trees have been found in New Plymouth (latitude 39^o05'S) and in Wellington (latitude 41^o16'S). These sites are 120 and 365 km south of the area reported to be the natural range of the species in New Zealand. This is the first record of persistent reproduction of kauri from trees planted outside the currently accepted natural range