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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Herbicides for use in management of certified Pinus radiata plantations in New Zealand

Post-planting vegetation control in commercial Pinus radiata D.Don forests within New Zealand almost exclusively uses a mixture of the two triazine herbicides, terbuthylazine and hexazinone. However, neither of these herbicides is endorsed for use on land certified by the Forest Stewardship Council (FSC), based on criteria relating to their persistence or toxicity in the environment. This is a problem for the forest industry as these herbicides are inexpensive, are not phytotoxic to P. radiata, and their residual action enables continued control of competing vegetation for up to a year following application. Using measurements obtained from three short-term field trials where herbicides were applied as pre- and post-emergent, post-planting treatments to a wide range of competitive vegetation species, the efficacy of alternative mixes of herbicides was compared to the triazine mix (the current industry standard). As the restrictions on the use of terbuthylazine by FSC may be lifted, this herbicide was also trialled in mixes with herbicides other than hexazinone. Tree growth was quantified one year after herbicide application using a biomass index. Results from all three trials showed that the triazine mix provided the greatest level of vegetation control, with the trees in this treatment attaining the highest biomass index. Where herbicide mixes were applied as pre-emergent treatments, the best alternative herbicide, as assessed by tree growth at one year, was indaziflam applied at 300 g active ingredient (a.i.) ha^–1. Compared to the triazine mix, the biomass index for this treatment was reduced by <1%. Where herbicides were applied as post-emergent treatments, the best alternatives to the triazine mix were very similar across trials and included treatments where terbuthylazine (at 7000 g a.i. ha^–1) had been applied in combination with one of either mesotrione (at 150 g a.i. ha^–1; 300 g a.i. ha^–1), triclopyr (at 113 g a.i. ha^–1), or clopyralid (at 1500 g a.i. ha^–1) or where a mixture of clopyralid, triclopyr and haloxyfop (1125 g a.i. ha^–1, 113 g a.i. ha^–1 and 250 g a.i. ha^–1) was used. Reductions in biomass index at one year in these five treatments, relative to the triazine mix, ranged between 5% and 35%, with smallest reductions being recorded for terbuthylazine used in combination with either clopyralid or mesotrione.     

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.     

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.     

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.     

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.     

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.     

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.     

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.