Evaluation of Eucalyptus red gum species and provenances for inland humid subtropical regions of southern China

There is a long history of eucalypt planting in inland regions of southern China where humid summers and frequent winter frosts and extreme cold events are features of the climate. Although early eucalypt plantings suffered widespread failures, some species managed to survive with individual trees in some plantings growing to impressive sizes with diameter at breast height (DBH) exceeding 50 cm. One of the most productive and best adapted species in the plantings was Eucalyptus camaldulensis. Two species–provenance trials were established in southern and central Hunan province in 2006 primarily to explore the potential of E. camaldulensis and the related E. tereticornis, but also to provide comparisons with two other species with potential for the climate. The trials included 65 provenances representing six taxa from four species: E. camaldulensis, E. tereticornis, E. amplifolia and E. macarthurii. Three provenances represented improved seed sources from Africa, whilst the others were natural stand provenances. Eucalyptus amplifolia var. amplifolia demonstrated the best potential for growth and survival up to age 5 years. Eucalyptus macarthurii had the best cold tolerance, but relatively poor performance for growth and survival. Both E. tereticornis and E. camaldulensis demonstrated reasonable cold tolerance, but growth and survival of E. camaldulensis var. camaldulensis provenances from temperate to subtropical climatic areas with dry summers and winter-dominant rainfall (Köppen climate classification Csa) were markedly inferior than those of E. tereticornis ig. ‘tereticamal’ and E. tereticornis ssp. tereticornis sourced from tropical and subtropical environments with summer-dominant rainfall (Köppen climate classifications Aw and Am). Seedlots of E. camaldulensis, E. tereticornis and E. macarthurii from improvement programs in Zimbabwe and South Africa mostly proved inferior to or no better than the best natural stand provenances of the same species in the Hunan environment.     

LIST OF MEMBERS AND ASSOCIATES 1966

We irrigated 36 species and provenances of mainly Australian native trees with saline drainage water (EC 2 dS/m and boron 2.4 mg/L) in a trial sited at Loxton, in semi-arid south eastern Australia. Twelve months after planting, the survival rates amongst species were similar with a site mean of 96%. Three years after planting, the tallest trees were E. gomphocephala and the provenances/clones of E. occidentalis and E. camaldulensis, with heights ranging from 5.3 to 6.7 m; these trees also had the greatest girth with basal areas (measured at 0.3 m above ground level) ranging from 16 m²/ha to 24 m²/ha. The basal area and height of E. camaldulensis was highly variable ranging from 1 m²/ha and 2.1 m for the CML42 clone, to 16 m²/ha and 6.2 m for the Alcoa clone 20. Provenance also had a significant effect on the values of these parameters in E. occidentalis. In the third year, water use rates were determined for 12 of the better growing species. Over summer, the mean daily water use rates ranged from 49 L/tree for the Alcoa clone 20 of E. camaldulensis, to 12 L/tree for E. kondininensis. The Alcoa clone 20 of E. camaldulensis had the higher daily rate of water use per unit area of sapwood, 4.7 kL/m². The hourly rates of water use per unit area of sapwood rose with increasing vapour pressure deficit up to a value of about 17 hPa and then remained constant as VPD rose to 55 hPa. Variation amongst tree species in the relationships between hourly rates of water use per unit area of sapwood and VPD was highly significant.     

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.     

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.     

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.     

Long-term estimates of live above-ground tree carbon stocks and net change in managed uneven-aged mixed species forests of sub-tropical Queensland,Australia

Estimates of carbon stocks and their annual change for extensive Australian sub-tropical forests are based on indirect estimates or on data derived from temperate forests. We estimated live above-ground tree carbon (LAC) stocks at landscape level from 355?000 measurements of 94?127 tree stems from 604 permanently monitored plots representing 2.6 million ha of managed uneven-aged mixed-species native forests in sub-tropical Queensland. These plots were established between 1936 and 1998 and re-measured every 2 to 10 years up to 2011. Landscapes were represented by 16 broad vegetation groups growing across a mean annual rainfall range of 500 to 2000 mm. Landscape-mean LAC stocks varied from 20.8 ± 4.3 t C ha^?1 in inland eucalypt woodlands to 146.4 ± 11.1 t C ha^?1 in coastal wet tall open forests. Landscape maximum LAC stock, defined as the mean of maximum LAC stocks over the entire measurement history for a specified landscape under prevailing environmental conditions and disturbance regimes, including sustainable forest management, ranged from 34.0 ± 7.2 t C ha^?1 in inland eucalypt woodlands to 154.9 ± 19.4 t C ha^?1 in coastal wet tall open forests. Annual live above-ground net carbon flux (C-flux) across all forests types ranged from 0.46 to 2.92 t C ha^?1 y^?1 with an overall mean of 0.95 t C ha^?1 y^?1 (n = 2067). Comparison of our results with Intergovernmental Panel on Climate Change (IPCC) estimates shows that in all cases, except for the sub-tropical steppe, the IPCC over-estimated stocks by between 13% and 34%. Conversely, the IPCC estimated C-fluxes were between 14% and 40% less than the Queensland estimates. These results extend statistically valid estimates of landscape LAC stocks and fluxes to the sub-tropical regions of Australia.     

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.     

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.     

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.     

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.     

Growth response following variable espacement of 28-year-old Alpine Ash regeneration in New South Wales

Analysis of stand growth-response patterns have shown that small increases in sawlog volume resulted from thinning fast grown, fire regenerated alpine ash (Eucalyptus delegatensis R.T. Bak.) from below to a range of regular tree-spacings, at age 28 years. No significant correlation was found between basal area growth response and increased spacing for four treatments that ranged from 3.7 m to 7.3 m.

Rapid natural stocking-attrition occurred in both thinned and unthinned stands during the 31 post-thinning years of measurement. Maximum density diagrams indicated that these alpine ash stands were fully-stocked at lower densities than have been recorded for many other forest species. As a consequence of the propensity to self-thin, little additional stand growth was gained from the thinning treatments. The 150 trees ha^?1 with the largest diameters from all thinned stands averaged a basal area increase of only 0.59 mha^?1 over the 31 year period of measurement (<0.2 mha^?1 yr^?1), when compared with the equivalent stratum from an unthinned stand.

However, the small average nett growth response to spacing was not distributed evenly across the largest 150 trees ha^?1 dbhob. The 50 largest diameter trees ha^?1 in spaced stands showed a significant (α = 0.05) positive response, the trees ranked 51 to 100 showed no significant response and those trees ranked 101 to 150 showed a significant (α = 0.05) negative response when compared with the corresponding strata in the unthinned stand, over the same period.

Thus the overall result of stand spacing on the largest 150 trees ha^?1 was a widening of the stand diameter distribution and a small overall gain in the merchantable volume. For sites of higher quality, the basal area response was larger and predominantly accrued to the largest 50 trees ha^?1.     

REVIEWS

Over a wide range of conditions fine fuel re-accumulation after fire in eucalypt forests is well described by equations of the form X_t = X_ss (l-e^?kt)

where X_t is the weight (t ha^?1) of litter accumulated at time t(yr), X_ss is the weight of accumulated litter under steady-state conditions, and k is a decomposition rate constant (yr^?1). Decomposition constants ranged from 0.11 to 0.31 yr^?1, and steady- state litter accumulations varied between 11.1 and 29.4 t ha^?1.

In many types of eucalypt forest, litter re-accumulates to dangerous (from a fire control point of view) weights in 3–6 years, thus severely limiting the period during which prescribed burning provides protection from wildfire. The rapid rate of litter re-accumulation is mostly due to a marked decrease in the total amount of litter decomposing (relative to rates of litter input), rather than to any fire-induced reduction in the rate of decomposition. The implications of these findings for fire management in eucalypt forests are briefly discussed.

More quantitative information on the relationships between fuel mass (and other fuel characteristics) and fire behaviour under high to very high fire danger conditions is required to enable better evaluation of the effectiveness of low intensity prescribed burning for fire control. The ecological impacts of prescribed burning regimes, which also need to be considered when devising burning programs, are briefly discussed.     

Glacier elevation changes in the western Nyainqentanglha Range of the Tibetan Plateau as observed by TerraSAR-X/TanDEM-X images

Global warming greatly affects glacier retreat, which in turn influences local water resources and sea level altitudes. We used Landsat Operational Land Imager (OLI) images to extract glacier outlines in the western Nyainqentanglha Range, then used TerraSAR-X/TanDEM-X images and SRTM-C DEM to calculate changes in glacier elevation using a differential interferometric synthetic aperture radar (DInSAR) approach. The decreasing rate of glacier elevation in the western Nyainqentanglha Range was ?0.30 ± 0.07 m per year (m yr^?1) from 2000 to 2014. The annual thinning rate of the northern slope (?0.46 ± 0.07 m yr^?1) was faster than that of the southern slope (?0.24 ± 0.07 m yr^?1). We investigated two exemplary glacier sites in details: Zhadang glacier on the northern slope and Gurenhekou glacier on the southern slope. The annual elevation change of 39 points on Zhadang glacier calculated by the DInSAR and Real Time Kinematic Global Position System (RTK-GPS) seperately have a correlation coefficient of 0.88. The mass balance change of Gurenhekou glacier is ?0.21 ± 0.06 m water equivalent per year (m w.e. yr^?1) from DInSAR, which is similar to the value of ?0.31 m w.e. yr^?1 determined via stakes and snow pits from 2005 to 2010.     

LIST OF MEMBERS AND ASSOCIATES, 1974

A 4250 hectare irrigated Eucalyptus camaldulensis plantation established in California's northern Sacramento Valley by Simpson Fiber Farms, Inc. for pulpwood is described. Intensive site preparation, fertilisation and irrigation in combination with tree improvement have enabled high yields to be obtained on 8-year rotations in an area of low natural productivity. Trees receive frequent irrigation through a massive drip irrigation system with water application scheduled on the basis of a combination of evapotranspiration estimates and plantation age. All planting stock now consists of tissue cultured clones intensively selected and tested for vigour, straightness, cold tolerance and more recently wood quality. Productivity of newer clonal stands is up to 100% more than those of the earlier seedling plantations and ranges up to 45 m³ per hectare per year. Wood samples from Simpson's plantation were analysed recently in Australia. The basic density of the Californian E. camaldulensis proved comparable to 10 year old E. globulus from Tasmanian plantations and some clones also had comparable yields of kraft pulp per tree despite slightly lower percentage pulp yields. The applicability of Simpson's operation to current interest in irrigated eucalypt plantations in inland south eastern Australia is discussed.     

ANNUAL REPORT

A brief outline is provided of the timber industry in North Queensland including a discussion of recent efforts to establish a plantation timber industry based on rainforest cabinet timbers to replace the industry lost with World Heritage listing in 1988. Results of a Delphi survey which sought expert opinion about the growth of rainforest and Eucalyptus species in mixed-species plantations in North Queensland are presented. Specifically, expert opinions about preferred species combinations and likely effects of mixed species plantations on timber yields are reported. Estimates of yield (m³ ha^?1 y^?1) and harvest age (years) are provided for 31 species commonly planted under the Community Rainforest Reforestation Program.     

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.     

Merchantability of Pinus radiata in relation to previous land use

An integrated thinning operation was carried out in 21-year-old radiata pine stands in the central tablelands of New South Wales to examine the effect of previous land use and associated problems of poor tree form on recovery of merchantable timber. The areas thinned were contiguous sections of plantation which had different types of land use prior to plantation establishment; native forest, cleared grazing land (pasture) and cleared land initially grazed and subsequently cultivated and cropped (cultivated pasture). Total volumes of harvested trees (to 8 cm small end diameter) were estimated (assuming no poor tree form) from regressions relating volume to stem diameter. This estimate was compared with the actual volume of saw logs and pulp wood recovered on site and with merchantable yields predicted using a locally derived Forestry Commission equation.

On-site yields of saw logs plus pulp wood were 143 m³ ha^?1 from the ex-native forest site, 191 m³ ha^?1 from the ex-cultivated pasture site and 210 m³ ha^?1 from the ex-pasture site. This represented a total recovery of more than 90% of the total stem volume to 8 cm small end diameter from ex-native forest and ex-pasture trees compared with 73% from the ex-cultivated pasture trees.

Of the trees harvested, 45% from the ex-native forest site had stem defects compared with 65% from the ex-pasture site and 88% from the ex-cultivated pasture site. These defects reduced the average saw log volume per tree by at least 50% in trees greater than 35 cm DBHOB. In contrast, the yield of pulpwood was similar for deformed and non-deformed trees because some logs which did not meet saw log specifications were down-graded to pulp logs.     

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.