Browsing by Browse by SEO 2008 "820101 Hardwood Plantations"

Mixtures of 'Eucalyptus globulus' Labill. and 'Acacia mearnsii' de Wildeman are twice as productive as 'E. globulus' monocultures growing on the same site in East Gippsland, Victoria, Australia, possibly because of increased nitrogen (N) availability owing to N₂ fixation by 'A. mearnsii'. To investigate whether N2 fixation by 'A. mearnsii' could account for the mixed-species growth responses, we assessed N₂ fixation by the accretion method and the 15N natural abundance method. Nitrogen gained by 'E. globulus' and 'A. mearnsii' mixtures and monocultures was calculated by the accretion method with plant and soil samples collected 10 years after plantation establishment. Nitrogen in biomass and soil confirmed that 'A. mearnsii' influenced N dynamics. Assuming that the differences in soil, forest floor litter and biomass N of plots containing 'A. mearnsii' compared with 'E. globulus' monocultures were due to N₂ fixation, the 10-year annual mean rates of N₂ fixation were 38 and 86 kg ha⁻¹ year⁻¹ in 1:1 mixtures and 'A. mearnsii' monocultures, respectively. Nitrogen fixation by 'A. mearnsii' could not be quantified on the basis of the natural abundance of 15N because such factors as mycorrhization type and fractionation of N isotopes during N cycling within the plant confounded the effect of the N source on the N isotopic signature of plants. This study shows that 'A. mearnsii' fixed significant quantities of N₂ when mixed with 'E. globulus'. A decline in δ15N values of 'E. globulus' and 'A. mearnsii' with time, from 2 to 10 years, is further evidence that N2 was fixed and cycled through the stands. The increased aboveground biomass production of 'E. globulus' trees in mixtures when compared with monocultures can be attributed to increases in N availability.

The subtropical eucalypt plantation estate in Australia now comprises more than 100,000 hectares in north-east New South Wales (NSW) and south-east Queensland (QLD). If a significant proportion of this resource is to be used for sawlog production, it is necessary to design effective silvicultural systems, particularly thinning procedures. A thinning trial was carried out at two sites in QLD and two in NSW. Each was planted with two species, 'Eucalyptus dunnii' and 'Corymbia citriodora' ssp. 'variegata'. The original stocking density of the plantations at planting was 1000-1300 trees per hectare. When the trees were 6-8 years of age, three treatments were applied in randomised complete block designs: an unthinned control, 550 and 300 stems per hectare residual stocking. Basal area increment after thinning was affected by site quality but was not affected by thinning treatments for either species. Mean diameter increment was significantly greater in the thinned stands of both species for all trees in the stand and for the largest 250 trees per hectare. The similarity of basal area growth and difference in diameter growth gives good management flexibility as all treatments at all sites were fully utilising site resources. Analysis of financial factors is needed to determine optimum management under different market scenarios.

The potential impact of agroforestry systems on C sequestration is widely recognized. However limited data is available on its impact on C dynamics, as much of the previous research has been focused on agricultural productivity. This research was therefore conducted to determine biomass carbon and litter quality of commonly recommended improved fallow species, at the coastal region in Kenya. An on-farm experiment was established in 2006 at a coastal Kenya site, using a Randomized Complete Block Design with five agroforestry species replicated thrice. Biomass carbon and litter quality was assessed at 6 and 12 months after sowing (MAS). Data was analysed using R version 2.9.0. The effects of species, measurement time and their interaction on total carbon were highly significant (P < 0.001). Total carbon stocks at 6 MAS ranged from 0.04 ('S.sesban') to 1.4 Mg C /ha ('M.pruriens') compared to 1.7 ('S.sesban') to 20.3 Mg C /ha ('T.candida') at 12 MAS. Results indicate that substantial amounts of C were sequestered in the biomass. However, duration of the fallow is a key factor to be considered. Litter quality was high with average polyphenol contents of 2.6 % while lignin contents were highest in 'T.candida' (16.3 %).

Pruning of live branches is a management option to enhance wood quality in plantation trees. It may also alter whole-tree water use, but little is known about the extent and duration of changes in transpiration. In this study, sap flow sensors were used to measure transpiration for 14 days prior to, and 75 days following the removal, through pruning, of the lower 50% of the live-crown length of 10-11 m tall four-year old 'Eucalyptus pilularis' Sm. and 'E. cloeziana' F. Muell. trees. Pruning had no effect on stem growth, sapwood water content or radial pattern of sap velocity in either species. Pruning reduced mean daily water use by 39% in 'E. pilularis' and 59% in 'E. cloeziana' during the first eight days after pruning. Thirty six days after pruning there were no longer any significant differences in transpiration rates between pruned and unpruned trees in either species. Our results show that pruning of live branches had only a short-term effect on whole-tree transpiration in these sub-tropical eucalypt species.

Tree growth and form are both influenced by crown architecture and how it effects leaf distribution and light interception. This study examined the vertical distribution of foliage in 4-year-old plantation-grown 'Eucalyptus pilularis' Sm. and 'E. cloeziana' F. Muell. trees. Leaf area (LA) distribution was determined at two different sites using allometric approaches to determine LA in crown sections and for whole trees. Leaf area was distributed more towards the upper crowns when canopies had been closed for longer. Leaf area was also skewed more towards the upper crowns for 'Eucalyptus pilularis' than 'E. cloeziana'. These species differences were consistent with differences in vertical light availability gradients as determined by point quantum sensors. Leaf area of individual branches was highly correlated with branch cross-sectional area (CSA) and whole-tree LA was closely related to stem CSA. Branch-level allometric relationships were influenced by site and crown position. However, the general allometric equations between stem size and whole-tree leaf area could be applied across sites. Results from this study suggest that pruning of live branches in these species should follow species-specific guides for the timing and height of pruning to optimise the effects on stem growth and form.

Understanding depth distribution of roots may help develop an understanding of plant productivity and the limits to productivity by indicating which parts of the soil profile are being accessed for water and nutrients. The subtropical east coast of Australia provides climatic and soil conditions that produce some of the highest plant productivity rates in the country. This has been recognised by the hardwood plantation industry and over the last decade a substantial estate of plantations has been established with plans for further expansion. However, two of the major species used, 'Eucalyptus dunnii' and 'Corymbia citriodora subsp. variegata', have had little published research directly related to root depth distribution in the area. We examined root depth distribution in established plantations of 'E. dunnii' and 'C. citriodora subsp. variegata' under three contrasting soil types using the techniques of soil trench profile and coring. The results showed that the fine roots of 'C. citriodora subsp. variegata' are at lower densities in poorly structured subsoils than the roots of 'E. dunnii'. The root densities of both species in the subsoils of a Vertosol soil (with high levels of reactive, shrink-swell clays) were lower than for the other soil types. In native vegetation Vertosols are often colonised by grasses with few, scattered trees from a limited range of species. Our findings show lower levels of root growth in the Vertosols, particularly into the subsoil and this is likely to be the reason that productivity on these, otherwise fertile soils, is restricted.

This paper investigates the products from first thinning at age 6 in 'Endospermum medullosum' (whitewood) plantations in Vanuatu at three stocking densities, and the financial outcomes from several silvicultural thinning regimes based on these spacings. Whitewood plantings established at stockings rates of 417, 625 and 833 stems per hectare were thinned at age 6 to approximately 45 % retained basal area. The thinning products were measured during harvest and value was estimated based on costs of production and appropriate margins relative to radiata pine products already on the market. Financial modelling for the whole rotation was undertaken for each of the spacing and thinning scenarios in the trial. The volume and size of poles and posts at first thinning was related to spacing. Low stocking density produced smaller quantities of larger poles, whereas higher stocking densities produced larger quantities of smaller posts. However, the monetary value of larger products grown under lower stocking rates was less than the value of the greater volume of product at higher stocking rates. This greater volume at higher stockings resulted in higher NPV for regimes with higher initial stockings for modelled scenarios regardless of harvest age. An exception was a scenario where no market for thinnings is available. A direct silvicultural regime (i.e. one with low planting density and no thinnings) had the highest NPV due to the higher price per cubic metre of larger diameter logs, achieved more rapidly because thinning did not remove basal area. Where thinning products are marketable, higher initial planting densities provide higher returns. Where access to markets for thinning products is difficult or where infrastructure is expected to improve in the future, planting at low stocking and without any thinning provides a high return on investment.

The effects of stocking on wood stiffness (MoE) for three 'Eucalyptus' species are quantified using a 6-year-old trial established in New South Wales, Australia. An acoustic time-of-flight tool measured the velocity between two probes in the outerwood, from which the stiffness was estimated. Four stocking levels (714, 1,250, 1,667 and 3,333 sph) were examined. Stiffness varied significantly between all species, with 'E. cloeziana' showing the highest stiffness (14.2-15.7 GPa), followed by 'E. pilularis' (12.2-13.5 GPa) and 'E. dunnii' (10.7-12.6 GPa). There was a stiffness increase (around 11%) between 714 and 1,250 stems/ha for all species but thereafter differences between stockings were not always significant. Trees were also assessed for basic density, 'dbh', total height, crown area, green crown height and stem slenderness (height/'dbh'). Only stem slenderness had a significant association (0.41 ± 0.17) with stiffness. These findings suggest that, where stiffness is a priority, forest managers could reduce establishment costs with low stockings (around 1,250 stems/ha).

'Eucalyptus pilularis' planted at three initial stocking densities of 833, 1111 and 1,667 stems ha⁻¹ grown at either square or rectangular spacing was assessed for the effects of stocking and rectangularity on wood properties. Sample trees from each stocking and rectangularity combination were harvested at age 7 years and assessed for the commercially important wood properties of bow, as an indication of growth strain, shrinkage and basic density. Crown length ratio was used as an indicator of stand vigour and clear wood availability. Furthermore comment is made on the financial ramifications of wide inter-row spacing. Stocking and rectangularity significantly influenced bow but not shrinkage or basic density. Reducing within-row spacing to 2 m with a larger between-row-space of 6 m had minimal affect on wood properties. Reducing the number of rows, whilst still retaining a commercial stocking, reduces the establishment costs and increases the ease of mechanical harvesting without adversely affecting log value.

'Eucalyptus' plantations cover more than 20 Mha worldwide and are almost exclusively monospecific. However, in native forests 'Eucalyptus' species often grow in mixtures. Mixed species stands of trees can be more productive than monospecific stands but despite the implications of this effect, for plantations and native 'Eucalyptus' forests, the effects of mixing eucalypts has received little attention. The aim of this study was to examine whether two species that naturally coexist ('Eucalyptus grandis' W. Hill and 'Eucalyptus pilularis' Sm.) grow faster in mixtures than their respective monocultures. Monocultures and 1:1 mixtures, and stands of two initial planting densities (1250 and 2500 trees ha⁻¹), were used to compare the productivity and stand structures of mixtures and monocultures and to quantify inter- and intra-specific competition. Interactions between these 'Eucalyptus' species increased their relative yields in mixtures by 10-30%. This was associated with changes in stand structure where the diameter distributions of both species became less positively skewed (lower proportions of small trees). Mixing effects were relatively consistent as the stands developed suggesting that if this complementarity effect is used in plantations there is considerable silvicultural flexibility, such that these mixed plantations could be used on both shorter rotations for biomass or pulp-logs as well as longer rotations for solid wood products. This study also suggests that interactions between co-occurring 'Eucalyptus' species in natural forests might actually facilitate individual tree growth, in addition to simply enabling co-existence.

Pruning of live branches is performed to enhance wood quality in plantation trees. Stem, branch and wood properties may be altered following pruning from below, but the extent and duration of such effects are unknown for many plantation 'Eucalyptus' species. The effect of 0%, 20%, 50%, and 70% green crown length removal on growth and wood quality was examined in 3.5-year-old plantation-grown 'Eucalyptus pilularis' Sm. (blackbutt) and 'Eucalyptus cloeziana' F. Muell. (Gympie messmate) trees on two subtropical sites in eastern Australia. Growth increment of the stem at breast height was not affected by 20% crown removal. However, stem increment at breast height was reduced for up to 8 months with 50% crown removal and up to 12 months with 70% crown removal. Pruning had no impact on height growth. However, the height of trees pruned to 70%, relative to the height of the surrounding unpruned trees, was temporarily reduced 12 months after pruning in both species. Stem form, stem taper, wood density, and residual branch growth above the pruned zone were unaffected by pruning. Owing to the fast vertical crown expansion, trees were able to rapidly compensate for leaf area removal without long-term reductions in stem growth. The implications for management operations utilizing pruning as a means of enhancing timber quality are discussed.

TREEPLAN is an advanced analytical tool providing accurate and precise predictions of genetic values to operational tree breeders. This project aimed to exploit TREEPLAN's analytical power for the benefit of all sections of the forest growing industry; in particular, the deployment sector and programs not traditionally associated with the Southern Tree Breeding Association. The outputs include: the routine inclusion of reproductive and fitness traits into the assessment framework; better prediction of stand performance through competition models; the undertaking of pilot studies using data from large industry programs; and the better modelling of the genetic structures of hybrid populations.

Maximising the production of knot-free (clear) wood can be achieved by early removal of branches from the lower crown. Ideally, this is carried out without reducing stem growth or the competitive status of the pruned tree. The decision surrounding the time to prune in Eucalyptus species is influenced by stem- and branch-diameter development, the rate of branch senescence and ejection on the lower stem, the timing of canopy closure and the proportion of leaf area that can be removed before growth is reduced. In this study, the effect of site quality on stem, branch and crown development was examined in 1.5- to 6.5-y-old 'Eucalyptus pilularis' Sm. and 'E. cloeziana' F.Muell. trees from plantations across north-eastern New South Wales, Australia. Results from 27 plantations established on former pastures showed that site quality influenced height, diameter growth, and live-crown rise in both species, but it influenced maximum branch diameter in 'E. cloeziana' only. Using regression relationships and threshold values for stem, branch and crown variables considered critical to determine the timing of pruning, decision matrices for low (0-2.9 m), high (0-5.5 m), and multiple (0-2.9 m then 2.9-5.5 m) pruning regimes were developed to provide a practical guide to identify the age at which stands could be considered for pruning. For 'E. pilularis' the rate of branch senescence will strongly influence the timing of pruning, while in 'E. cloeziana' the timing of pruning will largely be driven by branch diameter growth on high-quality sites and branch senescence on medium- and low-quality sites.

Mixed-species plantations of 'Eucalyptus' with a nitrogen (N₂) fixing species have the potential to increase productivity while maintaining soil fertility, compared to 'Eucalyptus' monocultures. However, it is difficult to predict combinations of species and sites that will lead to these benefits. We review the processes and interactions occurring in mixed plantations, and the influence of species or site attributes, to aid the selection of successful combinations of species and sites. Successful mixtures, where productivity is increased over that of monocultures, have often developed stratified canopies, such that the less shade-tolerant species overtops the more shade-tolerant species. Successful mixtures also have significantly higher rates of N and P cycling than Eucalyptus monocultures. It is therefore important to select N₂-fixing species with readily decomposable litter and high rates of nutrient cycling, as well as high rates of N₂-fixation. While the dynamics of N₂-fixation in tree stands are not well understood, it appears as though eucalypts can benefit from fixed N as early as the first or second year following plantation establishment. A meta-analysis of 18 published studies revealed several trials in which mixtures were significantly (P < 0.001) more productive than monocultures, and no instances in which mixtures were less productive than monocultures. Regression analyses of such data were more informative than indices of relative yield, and were more informative in trials that contrasted four or more different species compositions. Thus replacement series examining compositions of 100:0, 67:33, 33:67, and 0:100 were more informative than minimalist 100:0, 50:50 and 0:100 series.

A doubling of aboveground biomass production has been observed in mixtures of 'Eucalyptus globulus' Labill. and 'Acacia mearnsii' de Wildeman when compared with monocultures after 11 years of growth. This study examined to what extent increased nitrogen (N) availability and accelerated rates of nutrient cycling may contribute to increased growth in mixtures. Monocultures of 'E. globulus' (E) and 'A. mearnsii' (A) and mixtures of these species were planted in a species replacement series: 100% E, 75% E + 25% A, 50% E + 50% A, 25% E + 75% A, and 100% A. Litterfall mass increased with aboveground biomass production and was highest in 50:50 mixtures and lowest in monocultures. Owing to higher N concentrations of 'A. mearnsii' litter, N contents of annual litterfall were at least twice as high in stands containing A. mearnsii (32-49 kg·ha¹·year–¹) as in 'E. globulus' monocultures (14 kg·ha¹·year¹). Stands with 'A. mearnsii' also cycled higher quantities of phosphorus (P) in annual litterfall than 'E. globulus' monocultures. This study demonstrated that mixing 'A. mearnsii' with 'E. globulus' increased the quantity and rates of N and P cycled through aboveground litterfall when compared with 'E. globulus' monocultures. Thus, mixed-species plantations appear to be a useful silvicultural system to improve nutrition of eucalypts without fertilization.

Mixed plantations of a 'Eucalyptus' species with a nitrogen-fixing tree species can produce significantly higher quantities of aboveground biomass than monocultures. However, if species or sites are not chosen correctly, one species may suppress the growth of the other and mixtures may be less productive than monocultures. Based on a study of 'Eucalyptus globulus' and 'Acacia mearnsii', this paper discusses the species attributes and site factors that should be considered to improve the probability of increasing biomass production using mixed-species plantations. In an 11-year-old mixed-species trial of 'E. globulus' and 'A. mearnsii' in southeastern Australia aboveground biomass production was twice as high in mixtures containing 50% 'E. globulus' and 50% 'A. mearnsii' than in 'E. globulus' monocultures. There are three main types of interactions that led to this growth outcome: competition, competitive reduction and facilitation. Facilitation occurred as 'A. mearnsii' fixed significant quantities of N, both in monoculture and when mixed with 'E. globulus'. In addition, not only rates of N but also those of P cycling through litterfall were significantly higher in mixed stands than 'E. globulus' monocultures, pointing to the importance of selecting a nitrogen-fixing species that is capable of N fixation and subsequent fast nutrient cycling through litterfall. Mixed stands developed stratified canopies, such that 'E. globulus' eventually overtopped 'A. mearnsii' after 9 years. This resulted in an increase in light capture at the stand level and a reduction in competition for light for 'E. globulus', a relatively shade intolerant species. This illustrates the importance of selecting species based on their height growth dynamics and relative shade tolerances, to ensure that neither species is suppressed by the other and that the less tolerant species is not overtopped by the more shade tolerant species. In addition to species attributes, site factors, such as soil nitrogen, phosphorus and water availability, play an important role in the interactions and processes occurring in mixtures. In a pot trial containing monocultures and mixtures of 'E. globulus' and 'A. mearnsii', mixtures produced more biomass than monocultures of either species at low levels of N fertiliser. However, at high levels of N fertiliser 'E. globulus' suppressed 'A. mearnsii' and the biomass production of mixtures was not significantly different to that of 'E. globulus' monocultures. This suggests that mixtures should only be planted on sites where the processes and interactions between species will increase the availability of, or reduce competition for, a major limiting resource for growth at that site. The accurate prediction of successful mixed-species combinations and sites is difficult due to the limited number of studies on mixtures. A mechanistic approach is required to examine the interactions and processes that occur in mixtures and to demonstrate why certain combinations are successful on some sites and not others.

The loss of foliage through pruning of live branches may reduce tree growth or it may be compensated by photosynthetic up-regulation of the remaining crown. Here, the changes in light-saturated photosynthesis following pruning to remove 50% of green crown length were examined in 4-year-old 'Eucalyptus pilularis' Sm. and 'Eucalyptus cloeziana' F. Muell. trees. The objectives of the study were to: (1) compare leaf-level physiological (light-saturated photosynthesis ('Amax'), stomatal conductance ('g'), transpiration ('T'), dark respiration ('Rd), quantum yield (Φ), light compensation point (Γ), water-use efficiency (WUE), nitrogen-use efficiency (NUE) traits in species with contrasting crown dynamics and structure, (2) examine the effect of crown position on these traits, and (3) examine the effect of pruning on 'Amax', 'g', 'T', WUE, NUE, leaf N and P concentrations and specific leaf area (SLA). Prior to pruning there were no differences in 'Rd', Γ and Φ between 'E. pilularis' and 'E. cloeziana' but differences in 'Amax', 'T', 'g', leaf N, leaf P, WUE, NUE and SLA. Whereas the rate of physiological processes ('Amax', 'T', and 'g') and leaf N and P concentrations increased with crown height, 'Rd', Γ, Φ and SLA declined along this vertical gradient, except in the upper crown of 'E. cloeziana' where 'Amax', 'T' and 'g' were not different to the lower crown. No up-regulation of photosynthesis or changes in leaf physiology occurred between 6 and 13 months after pruning in either species. The results provide an important basis for modelling pruning effects in process-based tree growth models.

This volume of some ten essays by seven scholars draws on a wide range of sources, both documentary and archaeological, to explore the physical landscape, the patterns of rural life, and the natural environment, of people in medieval England. Thus animals, both kept and hunted, and vegetation, as well as agriculture and contemporary 'technology' are carefully appraised. The result is an amazingly comprehensive guide to the landscape of the past and its exploitation, particularly in the twelfth and thirteenth centuries. Much of the documentation is presented in excellent diagrams and tables.

The development of plantations with a new species, such as is occurring with the endemic tree 'Endospermum medullosum' (whitewood) in Vanuatu, requires the resolution of appropriate establishment techniques. Site preparation, fertilisation and weed control have a very large impact on plantation productivity and represent major risks to plantation success. Establishment techniques for tropical species are reviewed and preliminary site preparation and fertilisation trials for whitewood reported. Trials were established at a site on Espiritu Santo island using available general purpose fertiliser with and without micronutrients at two rates. There was no effect of fertiliser over various rates of complete fertiliser with and without micronutrients, designed to provide adequate phosphorus in volcanic ash soils. Ripping had no significant effect on growth, however insufficient hand clearing of vegetation resulted in lower growth due to competition and complete machine clearing of vines results in high temperatures and decreased survival. A serious issue for whitewood establishment in single species plantations is weed management, especially vine control ('Merremia' spp). The time needed for weed control is influenced by initial planting density and spacing. When inter-planted with mixed gardens of food crops, weed control is not an issue due to more regular tending.

The 'Eucalyptus dunnii' Maiden plantation estate in north-eastern NSW and south-eastern Queensland is significantly expanding on ex-grazing land. Thirty-one growth plots (average age 5.2 y) covering a latitudinal range of about 3.2° (370 km) and at altitudes from 8 m to 740 m asl in NSW were used to evaluate the correlation of site, soil and climatic variables with growth of 'E. dunnii'. Using height at an age of 10 y as a standard, site indices for 'E. dunnii' across the 31 sites averaged about 16 m, ranging from around 5 m to 26 m. The factors available-water storage capacity of the soil, rainfall and altitude accounted for 62% of the variation in site index. Inclusion of measures of fertility did not improve the predictive capacity of the model, possibly because of the limited size of the data set with soil chemical analyses. The predictive model, based on simple, easily assessable site factors, has the capacity to improve the quantitative evaluation of the productivity of sites for 'E. dunnii' plantations. The need for a simple field assessment procedure for selection of suitable sites was highlighted by the wide range of productivity exhibited across the plots.

This paper investigates the early growth response, branching and stem quality of 'Endospermum medullosum' (whitewood) at different spacings. Whitewood plantings were established at stockings of 400-833 trees per hectare and early growth, tree stem quality and branching were quantified up to age 3 years. Growth, number of live branches and branch size were negatively correlated with stocking. The stocking of trees of acceptable quality had high spatial variation. Initial spacing in whitewood plantations can be used to manipulate branch size, crown rise and stem size; all of which are important for development of pruning and thinning regimes to produce high quality logs. If unimproved whitewood stock is used, to ensure that there are 300 stems per hectare of acceptable quality to produce sawlogs, more than 600 trees per hectare should be established at planting.

Stocking at and after thinning forest plantations influences the site resources available to each tree, thereby affecting the size of logs and the value of the stand at harvest. Log prices generally indicate increasing value with increasing log size. A 'Eucalyptus pilularis' Correlated Curve Trend (CCT) trial was used to examine distribution of tree size for stands established at 1495 trees ha⁻¹ and progressively thinned to final stocking densities of 700, 450, 250, 125 and 87 stems ha⁻¹. Diameter at breast height over bark and total height measurements, collected periodically over 36 years, were used to define stem taper. Smalian's sectional volume formula was used to calculate log volume at 1-m intervals. Stems were then merchandised to current log size and pricing to determine optimum dollar values. Establishment and early maintenance costs were used to calculate net present value (NPV) at a discount rate of 6% and internal rate of return (IRR). The relationship between value over time and final stocking was irregular. The control (1495 stems ha−1) had the highest volume ha⁻¹ at age 36 years. Final stocking densities of 125 stems ha⁻¹ and 700 stems ha⁻¹ achieved the highest (8.13%) and lowest (6.19%) IRR, respectively.

The subtropical eucalypt plantation estate in eastern Australia has developed over several major periods of expansion and has now reached over 115 000 ha. Before 1994 state agencies, particularly Forests NSW, had established about 20000 ha of mainly 'Eucalyptus pilularis' and 'E. grandis' on land previously under native forest in coastal areas with precipitation of more than 1000 mm y⁻¹. Much of this area is now going into second-rotation plantations, mainly of 'E. pilularis'. Since 1996, state government agencies have established large areas primarily for solid-wood products, and more recently private companies have established large areas for pulpwood as well as for solid wood. In any estate, several eucalypt species are usually required to fully use the available land due to the limitations imposed on individual species by frost, differing moisture regimes and complex soil landscapes. Species-site matching is further complicated by pest and disease problems in the major species that often are first evident where species are not ideally located. Several pest and disease problems have become evident only since the widespread planting of major species in plantations and were apparently present only at low levels in the native populations of these endemic species. Some subtropical species can produce trees having excellent wood properties, but the quality of timber from native forest trees and plantation-grown trees differs and much work remains to be done to define optimum rotation lengths and management regimes. Silvicultural and breeding strategies have been developed to improve performance in all the above respects.

Frost tolerance is a necessary characteristic for the successful establishment of 'Eucalyptus radiata' subsp. 'radiata' Sieber ex DC (1,8-cineole variant) for production of essential oil on frost-prone sites. The frost tolerance of seedlings from six commercial oil-producing provenances of this taxon was examined using the electrical conductivity method. One provenance of 'E. radiata' subsp. robertsonii and two provenances of E. dives Schauer were also included for comparison. To verify the validity of this method, frost tolerance was also assessed in two field trials near Armidale on the New England Tableland of New South Wales where plants at one year from planting were scored for physical damage attributed to the effects of frost, viz. leaf fall and stem splitting. There were consistent and significant differences in modified relative conductivity (RC) between provenances, and between open-pollinated families within provenances, across temperatures. 'Eucalyptus radiata' subsp. 'radiata' from Isabella River, followed closely by provenances from Reedy Creek and Yowrie, were the most cold-tolerant, while the two 'E. dives' provenances and 'E. radiata' subsp. 'radiata' from Alexandra were the least frost tolerant, based on RC values. Rankings of 'E. radiata' subsp. 'radiata' provenances based on scores for stem splitting and leaf fall after their first winter in the field corresponded well to the RC rankings, with Reedy Creek the best performing provenance overall. Apart from limiting frost damage through selection of hardy provenances, the significant within-provenance family variation in frost tolerance, and the substantial variation between individuals within families noted in these trials, suggest good potential for selection and breeding amongst hardy individuals of the best ranked families to improve frost tolerance.

A 2 x 2 factorial combination of thinned or unthinned, and pruned or unpruned 11-year-old 'Eucalyptus dunnii' (DWG) and 12-year-old 'Corymbia citriodora' subsp. 'variegata' (CCV) was destructively sampled to provide 60 trees in total per species. Two 1.4 m long billets were cut from each tree and were rotary veneered in a spindleless lathe down to a 45 mm diameter core to expose knots which were classified as either alive, partially occluded or fully occluded. Non-destructive evaluation of a wider range of thinning treatments available in these trials was undertaken with Pilodyn and Fakopp tools. Disc samples were also taken for basic density and modulus of elasticity. Differences between treatments for all wood property assessments were generally small and not significantly different.Thinning and pruning had little effect on the stem diameter growth required to achieve occlusion, therefore occlusion would be more rapid after thinning due to more rapid stem diameter growth. The difference between the treatments of greatest management interest, thinned and pruned (T&P) and unthinned and unpruned (UT&UP) were small. The production of higher value clear wood produced after all knots had occluded, measured as the average stem diameter growth over occlusion of the three outermost knots, was approximately 2 centimetres diameter. Two of the treatments can be ruled out as viable management alternatives: (i) the effect of thinning without pruning (T&UP) is clear, leading to a large inner core of stem wood containing knots (large knotty core diameter) and (ii) pruning without thinning (UT&P) results in a small knotty core diameter, however the tree and therefore log diameters are also small.