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.     

Stem and branch form of 20-year-old radiata pine in relation to previous land use

The growth and form of 20-year-old radiata pine stands were assessed in relation to previous land use in Sunny Corner State Forest, near Lithgow, N.S.W. Basal area and merchantable volume were higher in ex-pasture (grazed land) and ex-improved pasture (grazed and cropped sites) than in an ex-native forest site, but the trees on former pastures were more deformed. A range of defects including multiple leaders, forks, stem sinuosity, butt sweep and heavy branching were most prevalent in the ex-improved pasture site. Up to 44% of trees in the ex-improved pasture were severely deformed and less than 50 stem ha^?1 were considered suitable as sawlog quality trees. Only 12% of trees in the ex-native forest site had severe defects.

Soil and foliar chemistry data showed that stem and branch deformities increased with increasing site fertility, and that deformity was directly correlated with soil mineral-N concentrations.

Deformity was also correlated with foliar manganese, aluminium and calcium, and some defects were similar to symptoms of boron deficiency. The role of these elements in “poor form” requires further study. Stand density also appeared to affect deformity. The results suggest that high densities may partially counteract the effect of high site fertility in the development of stem and branch defects.     

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.     

Grade and value variations in Eucalyptus urophylla × E. grandis veneer due to variations in initial plantation spacings

Processing young, small-diameter eucalypt logs into veneer is a burgeoning industry across southern China. However, plantations supplying these logs are mostly managed on silvicultural regimes which are appropriate for pulpwood and little information is available on alternative regimes for eucalypt plantations with respect to veneer yields and quality. Log size along with a range of tree and log traits were assessed on 12-year-old eucalypts in six spacing treatments, ranging from 666 to 2?222 trees ha^?1, in a field trial in southern China. Logs harvested from these were rotary peeled for veneer; recovery percentages plus a range of quality and value traits were assessed on the outturn. Log volumes, small-end diameters and individual log values varied significantly between spacing treatments, but total veneer recoveries (as a percentage of log volume) and veneer values per unit volume did not. The spacing treatment providing the highest veneer value per unit area was that with the highest stocking; 2?222 trees ha^?1. Although the second logs (up from the butt log) had significantly lower average volume than butt logs, and they had significantly higher average value per unit volume because of higher average total veneer recovery (68.7%) compared with the butt logs (59.7%). A number of external log features were significantly correlated with veneer value per unit volume and total veneer-recovery percentage. In declining order of importance these were taper, sweep, number of visible epicormic stubs, number of bumps and visible branch stubs, and longitudinal growth strain in the outer-wood. Branch-related defects were the most important grade-limiting defect, limiting veneer sheet quality to D-grade for most sheets. Considerable improvement in veneer sheet quality may have been achieved by pruning either just before or after branch death. Mill-door prices for logs were calculated after accounting for processing costs obtained from the mill and averaged RMB774 m^?3 (about A$126 m^?3). Had the trees been pruned, simulations indicated that prices/values could be lifted by RMB60–128 m^?3 (A$10–21 m^?3) and RMB393–461 m^?3 (A$63–74 m^?3) for production of higher-quality structural veneer and appearance-grade face veneer, respectively. It appears feasible that improvement in mill-door log values is possible with production of appearance-grade face veneer, but this will require some improvement in log quality through silvicultural intervention with pruning. It will also require improvement in processing methods and reduction in the impact of log end-splitting on veneer quality.     

Comparison of the productivity,cost and stem breakage of two- and three-machine harvest systems clearfelling a mature Pinus radiata stand

ABSTRACT

Damage to trees and logs during harvest and transport can result in major losses of wood volume and value. The study compared a harvester/forwarder (two-machine) harvest system, which typically is used in Australia, with a feller-buncher/processor/forwarder (three-machine) harvest system in terms of productivity, cost and felling stem breakage when clearfelling a 29-year-old Pinus radiata plantation in eastern Victoria, Australia. The study aimed to determine whether the three-machine harvest system reduced felling tree breakage while maintaining or improving on the productivity and delivered cost of the two-machine harvest system. The harvest systems were compared on adjacent sites (~1 ha each) using an elemental time study. Machine productivity was derived from cycle times using StanForD stem files to obtain merchantable tree volumes and forwarder load weights from the forwarder’s onboard scales.

The three-machine harvest system was more productive and resulted in considerably less felling stem breakage than the two-machine harvest system (two broken stems compared with 21 broken stems). However, it was approximately 41% more expensive than the two-machine harvest system in terms of cost per m³ of logs delivered to roadside. Because chiplogs were cut from broken stem sections where possible, and it was unlikely that sawlog volume was lost through stem breakage (based on the minimum sawlog specifications and the length and large-end diameter of the broken stem sections), any financial losses resulting from the additional breakage in the two-machine harvest system were insignificant compared with the extra cost per m³ of logs delivered for the three-machine harvest system.     

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.     

Domestic timber harvesting affects wood quantities in Tasmanian dry eucalypt forests

Domestic fuelwood harvesters illegally reduced coarse (≥10-cm diameter) downed woody debris stocks in Tasmanian mature dry eucalypt forests, 27–34 m tall, by 96.9 m³ ha^?1 or 22.7 t ha^?1. There was no effect of domestic harvesting on quantities of dead trees or live trees. Few dead trees were encountered in natural (unharvested) sites. Domestic harvesters preferentially removed debris <70 cm in diameter, leaving domestically harvested sites with 40% less volume and biomass of downed woody debris than natural sites. Assuming domestic harvesting, at the measured intensity, extends 25 m into forests either side of the state forest road system that passes through the studied forest type, dead wood stocks in that forest type and tenure throughout the state have been reduced by 688?000 m³ or 161?000 t. Domestic harvesting potentially damages biodiversity values, diminishes habitat available for species dependent on fallen logs and reduces forest carbon stocks. Domestic harvesters are advised to obtain licences to collect fuelwood from areas with an appropriate forest practices plan.     

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.     

Mortality of Eucalyptus marginata (jarrah) and E. calophylla (marri) trees following stem injection: effects of herbicide,dose, season,and spacing of injections

Mortalities of Eucalyptus marginata Donn ex Smith (jarrah) and E. calophylla R.Br, (marri) trees injected with Roundup^TM (360 g glyphosate l^?1 ) or Tordon Timber Control^TM (50 g picloram l^?1 and 100 g triclopyr l^?1 ) (P+T) were determined at doses of 5 to 80 grams of active ingredient (g.a.i.) m^?2 of stem basal area for glyphosate, and 2 to 40 g.a.i. m^?2 for P+T. The effect of spacing of injections around the tree bole was examined. Seasonal variation in mortality was examined in relation to atmospheric vapour pressure deficit (v.p.d.) and soil water deficits.

Glyphosate was more effective in killing E. marginata trees, whereas P+T tended to be more effective in killing E. calophylla trees. The optimum doses of glyphosate and P+T for E. marginata trees were 20 g.a.i. m^?2 and 15 g.a.i. m^?2 respectively, and for E. calophylla 80 g.a.i. m^?2 and 15 g.a.i. m^?2 respectively. Spacing of injections around the circumference of the tree did not have a significant effect on the mortality of E. marginata trees injected with glyphosate. However, mortality of E. calophylla trees injected with P+T declined from 89% at 10–15 cm spacing to 70% at 25–50 cm spacing.

There were strong seasonal effects with both herbicides and in both species, with mortality higher (70 - 90 % mortality) in seasons other than summer (30 - 50 % mortality). For E. marginata trees injected with glyphosate, mortality declined linearly with increasing v.p.d., from 95% at a v.p.d. of 0.5 kPa, to 25% at 4.5 kPa. For E. calophylla trees injected with P+T, mortality declined linearly with increasing v.p.d., from 85% mortality at a v.p.d. of 0.5 kPa, to 50% at 3.0 kPa. Stem injection of both species should only be carried out when the vapour pressure deficit on the day prior to stem injection is less than 1.5 kPa.     

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.     

Nine year results from a Eucalyptus camaldulensis Dehnh. provenance trial in the Wellington catchment of Western Australia

Data for 20 provenances of Eucalyptus camaldulensis from the southern half of Australia including 14 provenances of variety camaldulensis and 6 provenances of variety obtusa were assessed for growth and form in the south west of Western Australia. Mean annual volume increment at age nine years was greater in variety camaldulensis (3.3 m³ ha^?1 yr^?1) than for variety obtusa (1.9 m³ ha^?1 yr^?1). No significant differences in forking or branching were found between the two varieties. Lake Albacutya (variety camaldulensis) was the most productive provenance yielding 5.3 m³ ha^?1 yr^?1 but was only average for form. Laura (variety camaldulensis) was the best all round performer yielding the third highest volume production (4.2 m³ ha^?1 yr^?1) and ranking in the top quartile for forking, branching and straightness. Within variety camaldulensis a weak correlation was found between height and mean annual rainfall, provenances from lower rainfall areas being more likely to produce taller trees. A trend for smaller numbers of persistent branches with decreasing rainfall was observed for the species as a whole.     

Quantitative and qualitative assessment of timber harvesting residues: a case study of a balsa plantation in Papua New Guinea

The quantity and quality of the harvesting residues in a balsa plantation in East New Britain Province of Papua New Guinea are reported in this paper. The plantation was harvested manually with a chainsaw and manpower to extract the industrial wood at age 6 years. A modified standard harvesting residue assessment method using plots on line transects was applied. The total weight of the harvest residues remaining on the site after wood extraction was 211.7 t_GREEN ha^?1 (tonnes (green) per hectare). The major component was un-merchantable stem wood (121.3 t_GREEN ha^?1; 57.3%), followed by bark (59.3 t_GREEN ha^?1; 28.0%). This level of harvest residue was relatively greater than that reported in other studies, reflecting the combination of the log specification applied and the nature of the stem defects in balsa trees. The level of residues indicates the possibility of additional woody material recovery for bioenergy after consideration of sustainability issues.

The average moisture content of the wood components of the residues was determined over two days. The average moisture content on the first day after harvesting was 50%, falling in the following day to about 48%. The abundance of five elements in the harvest residues was estimated using data from a single sample tree; of the elements assessed potassium was the most abundant while calcium was the least.     

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.     

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.     

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.     

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.     

FIREWOOD UTILISATION IN VICTORIA

The production of volume tables for large mature eucalypts and rain forest hardwoods by a method suitable for Tasmanian conditions is described. The tables are produced from a minimum number of sample trees. They read directly the merchantable volume when girth breast high is measured and the heights to the top and bottom of the millable log are estimated. Procedures of sample tree measurement, table compilation and statistical testing are outlined.     

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.     

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.     

Effects of tree spacing on branch-size development during early growth of an experimental plantation of Eucalyptus pilularis in subtropical Australia

ABSTRACT

Branch development in trees 1.6–5.7 years after planting was studied in a plantation experiment involving Eucalyptus pilularis in subtropical eastern Australia. The experiment compared stocking densities at planting in the range of 816–1667 stems ha^?1 and rectangularities of tree spacing in the range of 1–6. Branch diameters at their bases were measured on the lowest 5 m of the stems of trees judged likely to yield sawn timber of high quality at final harvest. Neither stocking density nor rectangularity had substantial effects on branch numbers or diameters. Particular interest was paid to the presence of branches with diameters in excess of 2.5 cm that might produce knots large enough to degrade the quality of sawn timber. Such branches developed on lower stems between 2–4 years of age. An average of nearly five such branches was found on more widely spaced trees, reducing to 2–3 on more closely spaced trees. The results confirmed other work suggesting that pruning of high-quality eucalypt plantations should start near 2–3 years of age to both limit the development of large branches and restrict the size of knotty cores in logs. There was no evidence that changing the rectangularity of spacing to 3 or a little more, from the more normal practice of close to square, would affect such pruning regimes: increasing the distance between rows can reduce establishment and harvest costs and allow easier access for silvicultural operations.