Managing wood production from small grower acacia hybrid plantations on eroded soils in central Vietnam

An experiment in a second rotation acacia hybrid (Acacia mangium × A. auriculiformis) clonal plantation in central Vietnam examined factors determining total wood production and its apportionment to sawlog and pulpwood. Growth and stand characteristics were compared with those in nearby plantations owned by small growers. The experimental site was on sloping land damaged and eroded by war and previous land use. The soil was shallow, with 20–30% laterised stones by volume and had lost part of the A horizon. Mean annual increment (MAI, in standing merchantable volume over bark) of the first rotation at age 8.8 years was 17 m³ ha^?1 y^?1. In the second rotation at age 7.6 years it was 20 m³ ha^?1 y^?1. Application of P fertiliser at three rates ranging from 14 to 86 kg ha^?1 increased stem diameter over the second rotation although stand volume response to P was not significant by rotation end. Potassium (14 kg ha^?1) gave no growth response. Growth rate was similar under weed control by herbicide and manual means. MAI increased progressively from 16.5 m³ ha^?1 y^?1 at the hilltop to 25.0 m³ ha^?1 y^?1 at the lowest part of the experiment; slope position influenced growth more than management practices. Key soil properties, pH, N, Bray-1 P and organic C were maintained from the first to the second rotation. With simple management practices including conservation of site organic matter and early stand management, appropriate for local small growers, the second rotation yielded 46% of harvested volume as sawlogs and the balance as pulpwood. Although small growers achieved similar growth rates, their current management regime does not yield sawlogs. They can influence the log categories produced and stand value through changes to stocking rate, stand management and rotation age.     

Relative,but not absolute,thinning responses decline with increasing thinning age in a Eucalyptus nitens plantation

Growth rates of trees and stand structure change as stands age, and therefore absolute and relative thinning responses may also vary with thinning age. The study examined whether thinning age influenced the relative and absolute thinning responses in Eucalyptus nitens plantations near Carrajung, Victoria, Australia, and whether this effect was influenced by nitrogen (N) fertiliser application. Two levels of thinning and fertiliser application were applied in a factorial design replicated three times in a randomised block layout in each of two trials established in September 2006 in adjacent plantations aged 3.2 y and 13.2 y respectively and from the same seed source. Treatments included: unthinned or thinned non-commercially from below to 300 trees ha^–1; fertiliser treatments were nil or 300 kg ha^–1 N as urea in the younger trial and nil or mixed fertiliser supplying 256 kg ha^–1 N, 80 kg ha^–1 P and 100 kg ha^–1 K in the older trial. Five years after thinning, basal areas of the largest 200 sawlog crop trees ha^–1 (SCTs) were about 4.1 m² ha^–1 greater in thinned than in unthinned stands, regardless of thinning age, and volumes of SCTs were 30.1 m³ ha^–1 greater in thinned stands. As a result of the greater standing basal area and volumes in the older trial, relative thinning responses of SCTs were greater in the younger trial, such that thinning increased the basal area of the SCT₂₀₀ by about 42% (and volume by 32%) in the younger trial, but by only 21% (and volume by 17%) in the older trial. Fertiliser application also increased absolute thinning responses. Smaller relative thinning responses in the older stand were associated with age-related changes in stand structure of unthinned stands, including increasing skewness and decreasing kurtosis of diameter distributions as stands aged. The absence of a thinning-age effect on absolute responses suggests that there is some flexibility in the thinning age in E. nitens plantations. However, it is important to note that while the absolute thinning response may be slow to decline, the size of the SCTs will be smaller after later-age thinning owing to the extended period of competition they experience prior to thinning.     

Nutrient management of contrasting Acacia mangium genotypes and weed management strategies in South Sumatra,Indonesia

ABSTRACT

Tropical plantations are an important source of forest products both to meet the growing demand for wood, and to facilitate the transition from native forests to more sustainably produced forest resources. Management of these plantations for optimal productivity and resource-use efficiency is vitally important, and nutrient management is a critical component of sustainable plantation production. In this study, we explored the response of Acacia mangium plantations in South Sumatra, Indonesia, to fertiliser and their requirement for fertiliser, focusing on phosphorus (P) at establishment. Almost all plantations across a series of 11 sites were highly responsive to P fertiliser, with nine of the 11 sites having more than double the productivity in P-fertilised treatments at age 1 year compared with control treatments. However, the quantity of P required for 90% of maximum growth was generally low by age 2 or 3 years, and 10 kg P ha^–1 at establishment was sufficient to ensure that at least 90% of maximum growth was captured across all the experimental sites. At a 12^th site, we explored the interactions between genotype and weed control, and found that both effects were additive in the response of the plantations to P, and thus there was no substitutability between management types: weed control, genotype and P needed to be managed in combination to achieve maximum productivity.     

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.     

Wood properties of Eucalyptus globulus at three sites in Western Australia: effects of fertiliser and plantation stocking

Wood properties of 10-year-old trees in Eucalyptus globulus plantations at three sites in Western Australia were examined. Silvicultural treatments applied at age two years were stocking (unthinned, 1250 stems ha^–1; thinned to 600 stems ha^–1 or 300 stems ha^–1) and nitrogen fertiliser application (0 or 250 kg ha^–1 elemental nitrogen) in factorial combination. The three sites differed markedly in their annual rainfall (620–1100 mm), open-pan evaporation and soil water-holding capacity. Wood cores were collected at breast height from a total of 263 trees (~15 trees for each site-by-treatment combination), and radial samples prepared for analysis by SilviScan to produce radial profiles of air-dry density and microfibril angle (MFA) and modulus of elasticity (MOE), and by radial near infrared (NIR) surface scanning to produce radial profiles of NIR-predicted Kraft pulp yield (KPY) and cellulose content (CC). Sampling interval was 0.025 mm for density and 5 mm for the other properties. For wood property mean values (i.e. wood property averages of each pith-to-cambium sample), sites differed significantly only in air-dry density. The Boyup Brook site, which had low annual rainfall, the lowest climate wetness index and soil water-storage capacity and the slowest diameter growth, had the highest mean wood density (648 kg m^–3), while Scott River, with the highest rainfall, had mean density that was 10% lower. The Wellstead site (low rainfall but highest soil water-storage capacity) was intermediate for density. The only other significant differences for mean wood properties were caused by fertiliser addition, which reduced NIR-predicted KPY from 54.6% (without fertiliser) to 54.1% and predicted CC from 43.7% to 43.1%. Clear radial trends were evident for all wood properties. Density, MOE, KPY and CC all increased from pith to the cambium, while MFA declined. From the innermost (pith) 10% to the outermost (cambial) 10% of the radius, density increased on average by 21%, MOE by 103%, KPY by 9% and cellulose by 11%, while MFA declined by 47%. NIR calibrations developed using the SilviScan and NIR spectral data explained 71% of variance in MOE for an independent set of radial wood samples of E. globulus from Victoria, but less than 50% of variance for density and MFA. Implications for paper pulp and veneer manufacture are briefly considered.     

Efficiency of nutrient use for biomass production of a Eucalyptus clone as a function of planting density in short-rotation cropping

ABSTRACT

The objective of this study was to assess the effects of planting density on nutrient use efficiency (NUE) in the production of biomass of a hybrid of Eucalyptus urophylla × Eucalyptus grandis. Twelve planting densities were evaluated at 36 months of age, ranging from 498 to 2564 plants ha^?1. Three trees were harvested in each treatment to determine biomass production and allocation (per plant and per area), concentration (g kg^?1), amount (kg ha^?1), and NUE of N, P, K, Ca, Mg and S in the biomass of leaves, branches, bark and wood. In summary, the increase in planting density resulted in: higher biomass production per area; a reduction in biomass production per plant; a reduction in homogeneity; an increase in the concentration of N, P and K in leaves, of N, Ca, Mg and S in bark, and of N, P and K in wood; a higher amount of nutrients exported by harvesting; and a higher NUE for wood production. The increase in NUE indicates a possible nutritional deficit in trees at higher stocking rates at the age of three years. The higher the planting density, the sooner the site will require re-fertilisation.     

Effect of Organic Sources of Nutrients on Tuber Bulking Rate,Grades and Specific Gravity of Potato Tubers

A field experiment was conducted during 2008–2009 and 2009–2010 to investigate the effect of organic sources of nutrients on tuber bulking rate, grades and specific gravity of potato tubers. The experiment consisted 24 treatment combinations with 8 treatment in popcorn [control, recommended dose of fertilizers (N₁₂₀P₂₅K₃₅ kg ha^?1), farmyard manure equivalent to 120 kg N ha^?1, leaf compost equivalent to 120 kg N ha^?1, vermicompost equivalent to 120 kg N ha^?1, farmyard manure equivalent to 90 kg N ha^?1, leaf compost equivalent to 90 kg N ha^?1 vermicompost equivalent to 90 kg N ha^?1 in succeeding crop of potato, three treatments [control, farmyard manure equivalent to 60 kg N ha^?1 and farmyard manure equivalent to 90 kg N ha^?1] were superimposed on the different treatments of pop corn. It was found that the application of farmyard manure equivalent to120 kg N ha^?1 to pop corn and farmyard manure equivalent in 90 kg N ha^?1 in potato gave the highest values of tuber bulking rate, specific gravity, number of large–sized (A–grade) and medium–sized tubers (B–grade) and total tuber yield followed by vermicompost equivalent to to 120 kg N ha^?1. Farmyard manure equivalent to 90 kg N ha^?1 to potato also recorded the higher bulking rate, tuber yield, specific gravity and a number of large sized tubers (A– grade and B–grade) as compared to the farmyard manure equivalent to 60 kg N ha^?1. The available N, P, and K in soil also improved with the application of organic manures.     

BOOK REVIEWS

After clearfeliing and removal of sawlogs and waste wood from a 33-year-old crop of radiata pine, a site on the central tablelands of New South Wales contained an estimated 222 kg ha ' of nitrogen in above-ground litter and logging slash, and 8746 kg ha^?1 in the soil. Broadcast burning of the litter and slash removed 139 kg ha^?1 of nitrogen, but had no measurable effect on the organic matter content of the soil. Hand raking removed 212 kg ha^?1 of nitrogen from the litter and slash, as well as approximately 1 cm of topsoil, containing at least 124 kg ha^?1 nitrogen.

It was concluded that on this site the commonly used technique of windrow raking of logging slash and litter before replanting was likely to have a greater effect on site nutrient capital than broadcast burning. Neither practice had an appreciable impact on total site reserves of nitrogen, since very large quantities are contained in the mineral soil. However, since little is known of the availability of these soil reserves to the replanted crop, it would be prudent to modify existing techniques so as to minimise their impact on the above-ground nutrient capital. It is suggested that a raking operation which removed only the woody debris would probably allow sufficient access for replanting, and would leave most of the nutrient-rich fine litter and topsoil intact.     

A review of nutrient,water and organic matter dynamics of tropical acacias on mineral soils for improved management in Southeast Asia

ABSTRACT

More than 3 000 000 ha of tropical acacias have been established in recent decades, mostly grown on short rotations of 4–7 years, by a range of growers, from smallholders in Vietnam with less than 5 ha to large industrial growers in Sumatra managing hundreds of thousands of hectares. While the acacia estate is declining in some areas due to disease susceptibility, it is still expanding in other areas, and acacias would probably be the preferred species in many areas if the disease issues can be overcome. To date, many of the silvicultural management practices have largely been based on operational trial and error rather than backed by scientific evidence. To ensure sustained production, a deeper understanding of the mechanism for the response of acacias to management and environment is required. The objective of this paper is to review recent advances in our knowledge of the nutrient, water and organic matter dynamics of acacia plantations on mineral soils in Southeast Asia. We show that water availability is a key factor influencing productivity in many locations, but also that there are options for new approaches to management, including regional and site selection (or choice to plant or not on any given plot of land), and an understanding of nutritional requirements will help managers to adopt best practices in their plantations. While many plantations show significant responses to nutrients, particularly phosphorus (P, e.g. up to 200% stem volume increase at age one year); initial large responses to P fertiliser are reported to diminish over time, such that the response tends to be non-significant at many sites by harvest age. Only small quantities are recommended at establishment (equivalent to around 10 kg P ha^?1) to maximise productivity. Large quantities of site nutrient pools are held in harvesting debris or slash. Slash should be considered a valuable resource for sustaining productivity into the future, and its role in relation to fertiliser application needs further study.     

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.     

Effects of fertiliser applications after thinning of Pinus radiata on a high-elevation site in south-eastern Australia

A trial to assess the effects of fertiliser applied after thinning was established in a ten-year-old Pinus radiata stand growing on a high elevation site in south-eastern Australia. The trial had two components. The first studied the effects of fertilisers applied in a factorial design with two levels of phosphorus (0 and 50 kg P ha^–1) and three of nitrogen (0, 150 and 300 kg N ha^–1) plus a mixed nutrient treatment to areas thinned to a routine intensity. In the second part, levels of thinning intensity were assessed with and without a fertiliser (N₁P₁) application. Over the seven years of the study, growth was affected by below average rainfall in four of the years. Significant responses to fertiliser were achieved with all treatments; the best was 150 kg N ha^–1 + 50 kg P ha^–1 plus trace elements. The volume increment was increased by 28%, however this was not significantly different from the N₁P₁ alone. The N₁P₁ fertiliser increased productivity at all thinning levels including the unthinned treatment. Models predicting relative growth response based on foliage nutrient levels gave reasonable predictions, that is, 29% increase in volume periodic increment and this was slightly higher than that achieved. On such low rainfall sites, rather than having multiple thinnings, one option is a relatively heavy thinning at a young age with fertiliser application and then leaving the stand until final harvest. Estate optimisation models provide forest managers with the means to evaluate fertiliser-thinning treatment options against objectives such as maximising the present value of expected future cash flow within production and budget constraints.     

Expenditure on forestry and forest products research in Australia 2007–2008

Total expenditure on forestry research and forest products research in 2007–2008 in Australia was $87.8 million. This comprised $61.0 million on forestry research and $26.8 million on forest products research and was estimated using the same methods as in the several previous assessments (Quick and Booth 1987; Lambert and Turner 1992; Turner and Lambert 1997,2005). When some peripheral expenditure such as support, administration and surveys were included, the total expenditure increased to about $105.8 million. The total expenditure represents an annual average increase of about 3% since 1982 but a slow decline (0.45% per annum) in adjusted terms (1982 dollars). About 50 organisations reported undertaking forestry and or forest products research, while other organisations provided funding for research. The expenditure was attributed to four broad sectors undertaking research—Commonwealth, state, university and private—and also to broad research areas (native forests, exotic species plantations, native species plantations and environment). Research on native forests and exotic species plantations generally declined, whereas that on surveys in native forests and native species in plantations increased from 2001–2002 to 2007–2008. Similarly, research capacity declined in traditionally strong research areas such as pests and diseases and fire behaviour, and increased in energy areas such as carbon and forest bio-energy. About 600 full-time-effective researchers and technicians were involved in research in 2007–2008, plus support and management staff. The staffing numbers of individual organisations ranged from single individuals to more than fifty.

In 2007–2008, about 52% of the research funds were provided directly or indirectly by the Commonwealth Government, 28% by state governments and 20% by private companies. Total expenditure on forestry and forest products research ($87.8 million) averaged $5.78 ha^?1 of managed forest. The forestry research expenditure according to forest type comprised $14.80 ha^?1 on exotic species plantations, $36.90 ha^?1 on native species plantations and Total expenditure on forestry research and forest products research in 2007–2008 in Australia was $87.8 million. This comprised $61.0 million on forestry research and $26.8 million on forest products research and was estimated using the same methods as in the several previous assessments (Quick and Booth 1987; Lambert and Turner 1992; Turner and Lambert 1997,2005). When some peripheral expenditure such as support, administration and surveys were included, the total expenditure increased to about $105.8 million. The total expenditure represents an annual average increase of about 3% since 1982 but a slow decline (0.45% per annum) in adjusted terms (1982 dollars). About 50 organisations reported undertaking forestry and or forest products research, while other organisations provided funding for research. The expenditure was attributed to four broad sectors undertaking research—Commonwealth, state, university and private—and also to broad research areas (native forests, exotic species plantations, native species plantations and environment). Research on native forests and exotic species plantations generally declined, whereas that on surveys in native forests and native species in plantations increased from 2001–2002 to 2007–2008. Similarly, research capacity declined in traditionally strong research areas such as pests and diseases and fire behaviour, and increased in energy areas such as carbon and forest bio-energy. About 600 full-time-effective researchers and technicians were involved in research in 2007–2008, plus support and management staff. The staffing numbers of individual organisations ranged from single individuals to more than fifty.

In 2007–2008, about 52% of the research funds were provided directly or indirectly by the Commonwealth Government, 28% by state governments and 20% by private companies. Total expenditure on forestry and forest products research ($87.8 million) averaged $5.78 ha^?1 of managed forest. The forestry research expenditure according to forest type comprised $14.80 ha^?1 on exotic species plantations, $36.90 ha^?1 on native species plantations and $0.99 ha^?1 on native forests (including ecological and environmental research, and hydrological studies and fauna-flora research). Additionally, there was expenditure of about $0.45 ha^?1 on land-based surveys (mainly biodiversity), primarily in native forests. Total expenditure on forestry and forest products research equated to an average of $3.90 m^?3 of harvested timber. This comprised $1.02 m ³ on timber removals from exotic species plantations, $7.38 m^?3 from native species plantations and $1.90 m^?3 from native forests.     

Growth performance of selected taxa as candidate species for productive tree plantations in Borneo

ABSTRACT

The establishment of commercial tree plantations in Malaysian Borneo began with a progression of various species, including Pinus caribea, Acacia mangium, Gmelina arborea, Falcataria moluccana (formerly Albizia falcataria) and Eucalyptus deglupta. Ultimately, A. mangium, intended for the production of pulplogs, dominated the plantation landscape. However, recent widespread devastation of A. mangium by the Ceratocystis pathogen in Sabah has led to a shift in plantation species, which has also necessitated a review of downstream end products. This paper analyses growth data and estimates productivity for species in a taxa trial as well as a F. moluccana progeny trial in a single trial area in Sabah. A eucalyptus hybrid (Eucalyptus urophylla x Eucalyptus grandis (UG)), Eucalyptus pellita, F. moluccana, Acacia crassicarpa and A. mangium exhibited high productivity after three years, with an average mean annual increment of approximately 35 m³ ha^?1 y^?1 or better. Mean annual increment curves show that productivity declined slightly for the eucalypts and F. moluccana after three years. Acacia species experienced a sharper decline associated with disease-caused mortality, with A. mangium the most seriously affected. The mean basic density of the UG hybrid and F. moluccana was 560 kg m^?3 and 252 kg m^?3 at six and five years of age, respectively, and E. pellita had a mean basic density of 629 kg m^?3 at six years of age. The importance of growth and wood properties in the selection of species suitable for planted forest development in the wet tropics is discussed.     

Weed control among planted and direct-seeded Eucalyptus,Acacia and Casuarina with the herbicides diphenamid,oryzalin, clopyralid and fluazifop-butyl

In a glasshouse pot trial, applications of the pre-emergence herbicide oryzalin at rates equivalent to 4 and 8 kg a.i. ha^?1 were toxic to germinating seeds of Eucalyptus maculata, Casuarina glauca and Acacia saligna. The pre-emergence herbicide diphenamid was toxic at rates of 7 and 14 kg a.i. ha^?1 to germinating C. glauca and A. saligna, but not to E. maculata.

Both oryzalin and diphenamid were selective at these rates when applied over newly-planted seedlings of Eucalyptus melliodora, Casuarina cunninghamiana and Acacia baileyana on a former pasture site. Diphenamid gave greater pre-emergence control of grass weeds, while oryzalin was more effective against the broad-leaved weeds. Overall, the most satisfactory long-term weed control and tree response was achieved with oryzalin.

The post-emergence herbicides fluazifop-butyl at 0.6 and 1.2 kg a.e. ha^?1 and clopyralid at 0.25 and 0.5 kg a.e. ha^?1, were mostly selective to the planted seedlings on the former pasture site, but they gave unsatisfactory weed control, probably because of a combination of poor timing of application and a herbicide-tolerant weed flora.     

Costs and benefits of a leaf beetle Integrated Pest Management (IPM) program. I. Modelling changes in wood volume yields from pest management

The Tasmanian leaf beetle Paropsisterna bimaculata is a species native to Tasmania that can cause severe defoliation of eucalypt plantations. High populations of P. bimaculata, capable of causing severe defoliation if unmanaged, can periodically occur through a substantial proportion of a plantation rotation. Some exotic insect pests not yet established in Australia, most notably Asian Gypsy Moth (Lymantria dispar), share the similar characteristic of imposing a threat for a substantial proportion of a plantation rotation. Managing such a threat is operationally complex and requires committing adequate resources to sustain a robust management system. However, the costs and benefits to the plantation owner of sustaining such a management system have not been quantified. The first step of such an analysis is to quantify the gains in additional wood yields from management that protects against severe defoliation of plantations.

Forestry Tasmania has conducted considerable research to develop an Integrated Pest Management (IPM) program to protect its plantations from damaging populations of P. bimaculata, and has been using this leaf beetle IPM program since the early 2000s. The program has generated many years of operational records from leaf beetle population monitoring. These historical population monitoring data coupled with knowledge of the impact of defoliation by leaf beetles on tree growth were used to estimate how much wood volume has been saved by protecting the Forestry Tasmania plantation estate from damaging large leaf beetle populations over an entire rotation. The probability of above-threshold leaf beetle populations (defined as populations that cause severe defoliation, >50%, if uncontrolled) could be predicted from (1) plantation age (the likelihood of above-threshold populations peaks at age 4–5 years and declines to a low value by age 12 years), and (2) site-level leaf beetle risk (sites of high leaf beetle risk were at higher elevation and closer to native grassland than sites of low leaf beetle risk). Based on these relationships, the occurrence of above-threshold leaf beetle populations was predicted in Forestry Tasmania’s 50 000 ha plantation estate between 2003 and 2034. The leaf beetle IPM program, through controlling these above-threshold populations, was then predicted to be able to avert losses of 2.18 million m³ (9.4% of merchantable wood volume).     

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.     

Biomass and nutrient distribution in relation Pine in relation to previous land use I. Biomass

Above-ground biomass data are compared for 21-year-old radiata pine stands on three sites which had different types of land use prior to plantation establishment. The three sites, previously under native forest, grazed pasture and a pasture site subsequently used for crop production (cultivated) formed a continuous section of plantation in the 1968 age class. Biomass equations were developed for each tree component in relation to stem diameter for each site. There were no significant differences between sites in the coefficients for stemwood and bark, but different coefficients were required to relate stem diameter to the biomass of branches in the dead crown and foliage in the lower live crown. Stands on previously cultivated pasture (pasture followed by crops) accumulated 362,745 kg ha^?1 in the above-ground biomass; 40% and 13% more than the ex-native forest (259,183 kg ha^?1) and ex-pasture (320,055 kg ha^?1) sites, respectively. Trees on the previously cultivated pasture allocated a larger proportion of the total biomass to branches (17.4%) compared with the ex-native forest and ex-pasture trees (11.1%). This is attributed to reduced stocking and enriched soil resulting from different previous land use practices. The high frequency of multi-leadered trees in the ex-cultivated pasture increased the non-merchantable components to 26.7% of the total biomass.     

HIGHER FORESTRY EDUCATION IN AUSTRALIA

The results of three field trials which were established in 1976 to determine the feasibility of increasing wood production of Pinus radiata by fertilisation of thinned stands are described after four years of growth following the fertilisation treatments. The stands of about 20 years of age were producing an average of 14 m³ ha^?1 stem-wood per year.

The extra volume of wood growth resulting from fertilisation averaged 4.2 m³ ha^?1 a¹ for all sites, and 5.9 m³ ha^?1 a^?1 for the two most responsive sites, the latter being 37% over that obtained from unfertilised stands. Fifty per cent of the extra volume was added to the largest one-third of trees in the stands. A dominant tree of diameter (bhob) 27.0 cm in 1976 became 30.7 cm in 1980 if unfertilised and 32.8 cm if fertilised, an increase of 2.1 cm.

The responses obtained were inversely proportional to both the relative growth rates of unfertilised stands following thinning, and to the nitrogen concentration in the foliage of unfertilised trees measured in the year following fertilisation. Some soil/plant relationships have been examined for nitrogen, phosphorus, potassium and sulphur.

Fertilisation at this age appeared to at least ‘break-even’ if costs were amortised at an interest rate of 6%. However, fertilisation may also be a useful means of increasing yields at relatively short notice and allow increased flexibility in harvesting and other forest operations.     

Establishing Eucalyptus nitens plantations using controlled-release fertilisers

Field trials were installed in three Tasmanian Eucalyptus nitens plantations to quantify growth responses and operational factors associated with applying controlled-release fertilisers (CRF) at planting. A range of CRF products, blends and rates of application was evaluated and compared with the industry standard (di-ammonium phosphate (DAP), 100 g seedling^–1). Trees treated with CRF were between 26 and 35% taller than unfertilised trees by age 2 years, with height equivalent to or greater than height using DAP. The use of CRF enabled the planting and fertilising operations to be combined, resulting in improved operational and financial efficiencies. Two suitable alternative primary CRF treatments were identified: Basacote® 9M applied at 20 g or 40 g seedling^–1 (B9M20 or B9M40). The B9M20 fertiliser provided equivalent height at a lower cost than DAP, while B9M40 provided greater height than DAP but at an equivalent cost. Height response was strongest and lasted longest at the low–moderate fertility site compared to the higher fertility sites. Both CRF treatments achieved rapid early growth in height, necessary for successful establishment by age 2 years, which helped reduce the period of susceptibility to browsing mammals and overtopping from weeds. Additional benefits from using CRF include significantly reduced fertiliser inputs, lower risk of leaching and lower risk of competitive uptake by weeds. These benefits are consistent with the objectives of developing more efficient operational systems, site-specific management and reducing environmental impacts.     

Biomass for aviation fuel production in the Fitzroy Basin,Queensland: a preliminary assessment of native and plantation forest potential

This scoping study assesses the contribution that woody biomass could make to feedstock supply for an aviation biofuel industry in Queensland. The inland 600–900 mm rainfall zone, including the Fitzroy Basin region, is identified as an area that is particularly worthy of closer study as it has potential for supply of woody biomass from existing native regrowth (brigalow and other species) as well as from new plantings. New analyses carried out for this study of Corymbia citriodora subsp. variegata trials suggest biomass plantings could produce harvestable yield of aboveground dry mass of about 85 t ha^?1 over a 10-year rotation at relatively low-rainfall (600–750 mm mean annual precipitation) sites and about 115 t ha^?1 at medium-rainfall (750–900 mm) sites. Estimates of productivity for native regrowth suggest potential productivity should be around 40 t ha^?1 during the initial decade after clearing when systems are managed for bioenergy rather than grazing. In this paper, potential production systems are described, and sustainability issues are briefly considered. It is concluded that more detailed studies focused particularly on biomass production would be worthwhile, and further research requirements are briefly discussed.