CROWN STUDIES OF JARRAH SAPLINGS, 1928–1938

Early patterns of growth and water use of Eucalyptus globulus subsp globulus Labili, and Eucalyptus nitens (Deane and Maiden) Maiden were measured for the first four years in a plantation established on a low rainfall site in south-east Tasmania. Half the plantation was irrigated to maintain soil water deficits at levels where available water did not limit growth: the other half was subjected to a series of water stress cycles which were interrupted by rainfall or terminated by supplementary irrigation to end severe drought stress.

Height of E. globulus was greater than that of E. nitens irrespective of water status. For both height and diameter, differences due to levels of available water remained insignificant until the third year of growth. Increments in volume were significantly higher in E. globulus than E. nitens in the third and fourth year of growth and these differences were more apparent in the rainfed than the irrigated treatment. However there were no differences in water use between species for either treatment in the second, third or fourth year of growth. Maximum rates of growth were associated with total water use just above pan evaporation.

The ratio of water use (mm water) to volume increment (m³) was always lower for E. globulus than E. nitens. It was concluded that E. globulus was more suited to sites where moderate water stress is experienced as part of the normal annual growing cycle.     

Eucalypt plantation forestry in Chile

Eucalypt planting has increased rapidly in Chile in the last two decades, from 753 ha in 1974 to about 45 000 ha in 1992; there were an estimated 170 000 ha of plantations by 1992. The most widely planted species is Eucalyptus globulus, planted in the centre and south; E. nitens is planted in colder areas and E camaldulensis in the drier north-central zone. E. cladocalyx and E. sideroxylon have shown promise in arid zones, and E. regnans, E. fastigata and E. delegatensis in the south. About 60% of the plants produced in 1992 were raised in containers, and most big companies prefer containerized plants even though bare-root seedlings are cheaper to produce. Large companies invest in intensive establishment and management techniques (site preparation, fertilization and weed control) which are often mechanized. The most damaging pathogen in nurseries is Botrytis cinerea, while plantations on droughty sites are prone to attack by the stem-boring insect Phoracantha semipunctata. It is estimated that E. globulus and E. nitens can grow at 40 m³/ha/year on some sites such as the coast of the VIIIth region. Rotations of 8 to 10 years are envisaged for pulpwood production and up to 25 years for solidwood production. The main goal is the production of pulpwood, with a short-fibre mill of 235 000 tons annual capacity commissioned in 1991. Eucalypt pulp is used in another mill as a supplement to radiata pine fibre. Sawn timber, plywood, veneer, built-up board, fuelwood and essential oils are also obtained from eucalypt plantations. An equilibrium level of 300 000 ha of eucalypt plantations, a production of 600 000 tons of pulp and the export of 5 million tons of chips have been predicted for the year 2000. Some concerns have been raised about possible negative impacts of the dramatic increase in the area planted with eucalypts. Several genetic improvement programmes are under way. with the first clonal orchard of E. globulus planted in 1991 and several more being established. A major research effort on the clonal propagation of eucalypts will begin in 1993.     

Eucalypt plantations in Tasmania

The areas of eucalypt plantations in Tasmania are examined by species and ownership category (to the end of 1984).

Prior to the early 1970s annual plantings averaged less than 20 ha but since then they have been gradually increased to an average of over 1500 ha for the period 1982–1984. These changes are attributable to the ready availability of a market for eucalypt pulpwood with the advent of export woodchipping in the early 1970s, and in 1979 the introduction of schemes assisting rural land owners to establish plantations. Industrial forestry companies, rural land owners and the State own 60%, 20% and 20% of the plantings, respectively. Almost 90% of plantings are in the north-west or north-east forest regions. The main species planted are two species of the southern blue gum group, Eucalyptus globulus spp. globulus and E. nitens, which each account for approximately 32% of the 11 400 ha planted. These two species have shown significantly superior early growth compared with the 24 other species examined, including 14 mainland species. The development of eucalypt breeding strategies in Tasmania is briefly discussed.     

Testing single visit pollination procedures for Eucalyptus globulus and E. nitens

Previously, the production of controlled crossed seed in eucalypts required three visits to the female tree during the flowering season. We combined two novel methods from the literature involving pollinating cut styles at anthesis, and isolating individual styles with a tube to reduce the operation to a single visit. In E. globulus, this method has successfully produced seed at a rate and quality which was not significantly different from the established three visit method. However, the cut style treatment method was not successful when applied to E. nitens, the difference in success possibly being due to the difference in floral morphology between the two species. This single visit method of controlled crossing has the potential to greatly reduce the cost of producing pedigreed seed in the economically important species E. globulus and has the potential for use in mass pollination systems.     

Are there genetic differences in susceptibility of Eucalyptus nitens and E. regnans stems to defect and decay?

Levels of spread of wood discolouration and incipient decay associated with artificial stem wounds were studied in a provenance trial of Eucalyptus regnans and a progeny trial of E. nitens. Natural incidence of discolouration and numbers and sizes of kino veins were also examined in a provenance × fertiliser interaction trial in E. regnans.

No differences were found between provenances of E. regnans for degree of spread of discolouration despite significant differences in tree diameter. However, incidence and size of kino veins differed between provenances of E. regnans. For E. nitens the spread of discolouration was less than that in E. regnans, and there were no significant differences in discolouration amongst the 10 open-pollinated families, or associated with tree diameter. Heritability estimates for lateral and longitudinal spread in E. nitens were relatively low and had large errors attached due to the small number of families sampled.

Degree of lateral spread was correlated with tree diameter in E. regnans but not in E. nitens. Nitrogen fertiliser did not appear to influence defect levels in E. regnans. However, adding phosphorus fertiliser was associated with fewer and smaller kino veins in disc samples removed from the base of the green crown.     

General productivity model for single grip harvesters in Australian eucalypt plantations

Australia’s eucalypt plantation estate (>900 000 ha) has largely been established since 1995. The main species is Eucalyptus globulus producing wood chips for export on a short rotation (~10 years). Two main harvesting methods are used: cut-to-length (CTL) at the stump and infield chipping (IFC). CTL harvesting is typically carried out with single-grip harvesters and forwarders. The study objective was to develop a general productivity model for medium-sized single-grip harvesters performing CTL harvesting at the stump in short-rotation E. globulus plantations under typical Australian operating conditions, as few harvester productivity models have been developed for these plantations. The model was developed from 47 harvester productivity studies carried out in Australian E. globulus plantations. Studies were predominantly short-term counts of the trees cut over at least an hour multiplied by an estimate of mean merchantable tree volume derived from inventory plots measured where the harvester was about to work or an adjacent area. The model developed explained 80% of the variability in harvester productivity (79% was explained by mean tree volume and 1% by harvester engine power). Results from comparable published CTL eucalypt studies generally supported the model. The strength of the relationship suggests the model could be used to estimate harvester productivity for similar site conditions and harvester/harvester head combinations (which represent most Australian E. globulus plantations) where mean merchantable tree volume and harvester engine power were known or estimated.     

Wallaby browsing and seedling palatability

Relative palatability of seedlings commonly used in silviculture in Gippsland were compared based on the survival of seedlings when exposed to captive swamp wallabies. Pinus radiata was significantly less browsed than the least browsed eucalypt species Eucalyptus globulus. The survival of 6-month-old E. regnans seedlings was significantly lower than that of 6 or 18-month-old E. nitens or E. globulus. Survival of eucalypt seedlings was not significantly increased by growing them under different fertiliser regimes nor by growing them in the presence of Anipel tablets which contain bitrex (ai). Browsing was almost significantly reduced (0.1 <P<0.05) by treating them with an aqueous solution containing 1 mg of selenium dioxide 4 weeks before exposing them to wallabies.     

Interactions between herbivores,vegetation and eucalypt tree seedlings in a plantation forestry environment

Non-lethal management methods for reducing mammal browsing damage to Eucalyptus seedlings during plantation establishment are currently being investigated in Tasmania, Australia. One method is use of selective retention of non-seedling vegetation in plantations. To assess its potential, information is needed on how herbivores use such vegetation and whether it has positive or negative effects on browsing and growth of commercial tree seedlings. We quantified the populations of five mammalian herbivore species in and around a spot-herbicided E. nitens plantation during its establishment. We also investigated several aspects of the interactions between those mammalian herbivores, insect herbivores, tree seedlings and non-seedling vegetation. We found that overall population densities were high for red-bellied pademelons (Thylogale billardierii) and red-necked wallabies (Macropus rufogriseus rufogriseus), but very low for common brushtail possums (Trichosurus vulpecula), common wombats (Vombatus ursinus) and the introduced European rabbit (Oryctolagus cuniculus). Population densities of the five mammalian species did not change in response to planting E. nitens seedlings. Dominant vegetation in the plantation was grass, then forbs and non-grass monocots. Herbivores ate a large proportion of available plantation vegetation in unfenced plots. Mammal browsing had little effect on survival of E. nitens seedlings 15 weeks after planting, but significantly reduced their growth. In unfenced plots, insects, mainly Heteronyx spp., caused twice as much damage to seedlings as browsing mammals. The absence of mammalian browsing in fenced plots, which resulted in high grass cover, was associated with reduced insect damage to seedlings.     

THE MILITARY SURVEY OF THE FOREST RESOURCES OF THE COMMONWEALTH TERRITORIES

A test was undertaken of a system which predicts eucalypt plantation wood volume yields in Tasmania from a set of eight topographic, climatic and soil variables measured at a site. The system was tested in 32 plots located in plantations of E. globulus and E. nitens in northern Tasmania. When the system predicted that a site had high productivity (maximum mean annual increment ≤20 m³ha^?1yr^?1), there was a fairly high probability (≈80%) that the site indeed had that productivity. However, when it predicted lower productivity, it incorrectly predicted a substantial proportion of sites (≈50%) as being of lower productivity when they were in fact of high productivity. It was shown that, on average, the system underestimated productivity by 7%. In practice, the system could be used to predict average productivity over a region within a range bounded by -4% to +18% of the prediction (95% prediction interval). The system had a similar predictive ability to two other systems developed in Australia to estimate plantation productivity.     

The threat to Eucalyptus plantations from an emerging Tasmanian leaf beetle pest: Paropsisterna selmani (Coleoptera: Chrysomelidae)

A newly described eucalypt leaf beetle, Paropsisterna selmani Reid and de Little, endemic to Tasmania, Australia, required management in Tasmania for the first time in 2011 to protect Eucalyptus nitens plantations from severe defoliation. This species was discovered following its incursion and subsequent establishment in southern Ireland in 2007.

Field monitoring using sticky traps in eight E. nitens plantations around Tasmania was performed to compare the spatial and temporal population distributions of adult P. selmani with adult P. bimaculata and P. agricola over two summer seasons, 2009–2010 and 2010–2011. Populations of all three species were extremely variable between sites and between and within the two seasons. While P. bimaculata dominated at six of the eight sites throughout Tasmania, P. agricola had high populations at the three most northerly sites. Adult P. selmani were trapped at all sites but were the dominant leaf beetles at one site and were relatively common at two other northerly sites.

During the longer trapping period in the second season, all three species showed two population peaks: one in spring (November–December) following emergence of adults from overwintering, and a second in late January–February of a second generation of adults. Heavy egg-laying followed the first but not the second adult population peak. At the two sites with the largest P. selmani populations, the peak spring flight of P. selmani adults occurred at least two weeks earlier than that of P. bimaculata and P. agricola, and the second flight peak was at least two weeks later than that of these species.

A new pest with a population phenology that differs from that of existing plantation pests could have important implications for the success of an Integrated Pest Management program designed to protect plantations from defoliation. Field records of P. selmani since it was first recorded in 1979 suggest that this species is increasing in abundance in Tasmania. Management of this species has been required since 2011 to prevent economic damage to plantations. This newly emerging plantation pest feeds on a range of Eucalyptus hosts, including the adult-phase foliage of the plantation species E. nitens, and poses new problems for plantation management in Australia, as well as increasing the threat of invasion into overseas eucalypt plantations, as already demonstrated in Ireland.     

Growth of Eucalyptus pellita and E. urophylla and effects on pasture production on the coastal lowlands of tropical northern Australia

Eucalyptus pellita F. Muell. and E. urophylla S. T. Blake are important timber species which have potential for wood production in plantation and agroforestry systems in humid northern Queensland. This study was established to examine two provenances of each species on a coastal lowland site, using randomised complete block design. Survival, height, diameter at breast height (DBH), bole length and tree form were measured at ages 12, 24 and 39 months. The height and biomass of the pasture underneath each provenance plot were also measured at 39 months. Significant differences occurred in most of the tree characteristics at 39 months. Differences in pasture growth, on the other hand, were not significant. Compared with the two E. pellita provenances, the provenances of E. urophylla had superior height and DBH growth but had worse form. Overall, however, both species had high survival, fast growth, satisfactory form, and minimal effects on pasture growth. Although all four taxa appear to be suitable for silvopastoral systems, further trials involving more provenances on a wider range of sites are recommended to establish the environmental and economic limits for the use of these species.     

Eucalyptus growth in relation to combined nitrogen and phosphorus fertiliser and soil chemistry in Tasmania

Two experiments were established to determine the early nutrient requirements for plantations of Eucalyptus globulus (Nabowla site) and E. nitens (Westfield site) in Tasmania, Australia. Nitrogen (N) and phosphorus (P) were broadcast together, 2 and 26 months after planting, at cumulative rates of up to 1200 kg N ha^?1 600 kg P ha^?1. Soil chemistry was characterised at each site in three profiles, and in all plots at the Westfield site. Nabowla has a relatively infertile, poorly structured soil, low in N and P, and receives about 800 mm of rainfall per annum. Growth was very poor without fertiliser, but trees responded rapidly and strongly to added NP. Stem volume increased directly with the rate of applied fertiliser, with no evidence that the response had peaked at the highest rate. Even at the highest rate of NP fertiliser, however, productivity was relatively low (mean annual increment about 15 m ha^?1 y^?1). Establishment of plantations on such sites is unlikely to be economically viable, with or without fertiliser, but fertile ex-pasture sites that are otherwise similar should be considered. Westfield has a relatively fertile, well-structured soil, and receives 1400–1500 mm of rainfall per annum. Response to NP fertiliser was delayed at this site, with first responses measured 33 months after planting. The response in stem volume was sigmoidal in relation to fertiliser rate, with a plateau at an application rate of 400 kg N ha^?1 and 200 kg P ha^?1. This rate of fertiliser is expected to increase mean annual increment from 20 (without fertiliser) to 25 m ha^?1 y^?1. Splitting applications of fertiliser at the highest rate did not alter the growth response.

Although high rates of N and P fertiliser may be required to maximise growth of eucalypt plantations in Tasmania on ex-forest sites, rates required during the first few years might be lower than those reported here if the timing and placement of fertiliser is optimised. Soil chemical analyses were indicative of N and P requirements, and about a third of the variation in growth across the Westfield site was accounted for by natural variability in initial concentrations of total P and exchangeable K in surface soil.     

Growth and form of provenances of Eucalyptus saligna at Wondo Genet,southern Ethiopia

A trial testing 10 provenances from across the natural range of Eucalyptus saligna and a local land race was established at Wondo Genet, southern Ethiopia. Eight years after planting, survival, tree height, diameter at breast height over bark, stem form, number of forks, height to the first fork, number of branches, branch diameter and branch angle were assessed. Volume per hectare was also calculated. Survival ranged between 36% (a provenance from 87 km north of Windsor, NSW) and 79% (Consuelo Tableland, Queensland), and differences were significant (P < 0.05). Among morphological characteristics, only the number of branches showed significant variation (P < 0.05), with the greatest number (12.4) being recorded for the Bulahdelah, NSW, provenance and the least (8.5) for the Clyde River, NSW, provenance. Major growth and morphological parameters (tree height, diameter, volume and stem form) did not differ significantly. The overall volume production (mean annual increment 26.4 m³ ha^?1) was well above the minimum acceptable growth observed on good sites elsewhere. Differences between provenances were small and mostly not significant, and no pattern of geographic variation was detected. Given the acceptable mean annual increment, those provenances represented by an adequate number of parent trees could be maintained for further selection and breeding, and to maintain genetic diversity of the species in Ethiopia.     

Fertilising Eucalypts at Plantation Establishment on Farmland in south-west Western Australia

Responses of Eucalyptus species planted on farmland in the south-west of Western Australia to nitrogen (N) and phosphorus (P) fertilisation were investigated over two and three year periods. Factorial combinations of N (0, 6, 17 and 34 g per seedling) and P (0, 5, 12 and 24 g per seedling) in mostly water soluble (quick release) compounds were applied within a month of planting.

On well drained soils growth of E. globulus exceeded that of E sideroxylon and E. microcarpa by a considerable margin. After three years there were significant (p < 0.05) growth responses by E. sideroxylon to N and P and by E. globulus to P only. In contrast, the third species planted in that experiment (E. microcarpa) showed no significant growth response to N or P. The growth response of E. sideroxylon to a combination of the maximum levels of N and P represented improvements (compared to no fertiliser) of 69% in tree height and 265% in crown volume index. For E. globulus the improvements with each level of P > 0 g were consistently around 14% in tree height and 29% in crown volume index. Improvements in basal area and stem volume index increased with each level of P tested from 13% (5 g P) to 42% (24 g P) in the case of basal area and from 40% (5 g P) to 58% (24 g P) in the case of stem volume index. On poorly drained soils the only significant effect of fertilisaer treatment two years after the planting on the species tested (E camaldulensis, E cornuta and E. woollsiana) was that increasing N level increased seedling mortality. Average mortality rate for the three species increased from 20% (0 g N) to 30% (34 g N).

In other experiments, also with three species on both well drained and poorly drained soils, fertiliser rates were kept constant at 18 g P and 8 g P per seedling but the form and timing of fertiliser application was varied. However, it made no significant difference to survival or growth rates of any species whether the fertiliser was applied in granular or tablet form, at planting time or one month after planting.     

Eucalypts in China

There are over 300 000 ha of Eucalyptus plantations established in southern China. The principal species planted since 1950 are E. citriodora, E. exserta and E. globulus. They provide a wide range of products including timber, posts and poles, fuelwood and essential oils and are a potential source of paper pulp and fibreboard.

A recent policy decision to increase forest cover from 12.7 to 20 per cent of the total land area by the year 2000 will require an acceleration of the afforestation programme to over 2 million ha annually. It is anticipated that eucalypts will have a significant role in this expansion.

The article reviews the history of introduction of eucalypts, outlines current silvicultural practices with special reference to Guangdong Province and Guangxi Autonomous Region and discusses prospects for the future use of eucalypts in China.     

The effect of tree spacing on the production of flowers in Eucalyptus nitens

The effect of spacing on the production of flowers and capsules in Eucalyptus nitens was studied in two spacing trials located in northern Tasmania. Tree density in these trials ranged from 468 to 4216 stems ha^?1. Reproductive structures were collected in litter traps and these data were used to calculate reproductive output on a per tree and per hectare basis. Between 8735 (5-y-old site, 1333 stems ha”¹) to 234098 (13-y-old site, 1082 stems ha”¹) flowers were produced per hectare over a single flowering season at these two study sites at the planting densities expected of a pulpwood plantation. This represented 8 and 211 flowers per tree respectively. As tree density decreased, the production of flowers and capsules increased on both a per-tree and per-hectare basis. It is estimated that the number of flowers per hectare is likely to be anywhere between between 1.4 and 10-fold greater under the spacing expected in sawlog regimes (250 trees ha^?1). This difference in reproductive output between plantations of E. nitens that use different spacing regimes is one of the many factors that need to be considered in assessing the risk of wilding establishment or hybridisation with adjacent native eucalypts.     

Relationships between annual rainfall,damage symptoms and insect borer populations in mid-rotation Eucalyptus nitens and Eucalyptus globulus plantations in Tasmania: can static traps be used as an early warning device?

Routine forest health surveillance of Eucalyptus nitens and E. globulus plantations in Tasmania has detected more frequent borer-related mortality in mid-rotation plantations in drier areas of the state. Damaging borer populations are not usually detected using traditional health surveillance techniques until mortality has occurred. Appropriately baited static traps are known to attract a wide range of stem-boring insects and might provide a means of monitoring populations in at-risk plantations. The objectives of this study were to explore the relationships between rainfall, tree stress symptoms and stem-borer-related damage symptoms in plantation eucalypts, and the nature of the associated borer populations, to determine whether static traps might provide an effective early warning system.

Trees from a number of mid-rotation plantations covering a range of rainfall categories were visually assessed for a wide range of damage symptoms, and two intercept panel traps baited with α-pinene and ethanol lures were deployed in each of 19 compartments between November 2006 and March 2007. All beetles caught in the traps were identified to species level and the numbers tallied. The incidence of damage symptoms tended to be negatively correlated with mean annual rainfall and was higher in plantations from lower-rainfall areas. There were no clear relationships between aggregated trap catches of borers and annual rainfall or the incidence of damage symptoms. However, a greater range of borer species was trapped in drier areas and the number of species trapped showed a strong negative correlation with annual rainfall. There were also strong positive correlations between damage levels and the range of borer species trapped. The size of the populations of some species, in particular some of the scolytids, increased substantially with decreasing rainfall and was strongly associated with the incidence of damaged trees. Cerambycids were the only group significantly correlated with borer-specific symptoms, but further work is required to determine their utility for monitoring purposes.

In vulnerable plantations an increase in the range of borer species, scolytid populations or specific indicator species caught in static traps might provide useful early warning of unacceptable levels of mortality or stem damage. As such, static trapping has the potential to monitor populations and allow for timely silvicultural intervention to ameliorate stress.     

Growth and form of Eucalyptus nitens progenies in New South Wales,and selection strategies for a seedling seed orchard

Eucalyptus nitens is potentially the most important eucalypt species for plantations in the tablelands regions of New South Wales. However, genetic parameters and data for provenance and progeny performance of the species in this State have previously not been available. A test of 30 open-pollinated families was established near Tumbarumba (NSW) in 1989, and assessed for a number of growth and form traits at age 5 years. Victorian provenance material, including seedling seed orchard progenies, was generally superior to NSW seed sources for growth and form traits but more prone to forking; all provenances included some superior individual families. Estimates of individual heritability were low to moderate (0.14 to 0.44) for seven growth, stem and branch form traits, with low standard errors, and very low for occurrence of forks and ramicorn branches. Genetic correlations among commercially important growth and form traits were generally moderate to high, and favourable. Selection of trees in the test to retain in a theoretical seedling seed orchard, using a multi-trait selection index, resulted in retention of 90 trees over 11 families, with high gains in growth and form (13.2 to 20.7 percent). Alternative selection strategies, retaining 90 trees over 15 families, gave somewhat lower gains in most traits but a more even distribution of trees over the orchard area.     

Moisture content measurement on Eucalyptus seed for storage

Seed moisture content may significantly affect the storage life of both agricultural and forest species. Seed store managers therefore need an easy and reliable method for routinely checking moisture contents. A robust, portable, easy- to-use electrical seed moisture meter, the Protimeter Grainmini V, was evaluated on samples of Eucalyptus globulus, E. pulchella and E. obliqua seed. Meter readings were well correlated with gravimetric moisture contents ranging from 4.7% to 24.3% of oven dry weight. Relative humidity readings were also made on the equilibrium atmosphere within sealed bags of seed to see whether it might be feasible to derive seed moisture indirectly via relative humidity.

For E. globulus, the fertile seed had gravimetric moisture contents several percent lower than the associated chaff, which normally comprises the bulk of a stored Eucalyptus seed lot. Equations were derived to define the relationship between the overall moisture content and that of the fertile seed, and the way this relationship is affected by the fertile seed/chaff ratio. Fertile seed also gave a higher meter reading than chaff at the same gravimetric moisture content. These effects were much less marked with smaller-seeded eucalypts.

These findings have been incorporated in calibration tables for the electrical meter, which is now used by Forestry Tasmania to screen all Eucalyptus seed prior to and during storage. Results should be generally accurate to within about ± 1 % of oven dry weight.

The concept of deriving seed moisture content indirectly through the equilibrium humidity of the seed atmosphere seems sound in principle but is impractical for this purpose at its present stage of development.