Provenance variation,genetic parameters and potential gains from selection for biomass and cineole production in three-year-old Eucalyptus loxophleba subsp. gratiae progeny trials

ABSTRACT

Ninety families from six provenances of Eucalyptus loxophleba subsp. gratiae were established near Brookton, Western Australia, and Condobolin, New South Wales, and 89 of these same families were established at Monarto, South Australia. All three trials were assessed at age three years for biomass productivity and the trial at Brookton was assessed for leaf cineole concentration. Provenance performance across the sites was most similar between Monarto and Condobolin, while the ranking of provenances was more divergent between those sites and Brookton. Presence or absence of unstable families may change provenance ranking. Additive variance was not significant for the Condobolin trial. Heritability of green biomass at age three years was ?² = 0.19 ± 0.06 and ?² = 0.16 ± 0.05 at Monarto and Brookton, respectively. The heritability of leaf cineole concentration at Brookton was ?² = 0.50 ± 0.08 and whole-tree cineole yield, ?² = 0.11 ± 0.04. The cross-site genetic correlation between Brookton and Monarto was r_g = 0.55 ± 0.20, suggesting the presence of some genotype × environment interaction. Removing the six most unstable families resulted in a cross-site genetic correlation of r_g = 0.97 ± 0.25. Estimated mean gains from selection scenarios treating Brookton and Monarto as representing two separate environments or as a single environment differed by about 5.0%. The exclusion of six unstable families reduced that difference to 1.4%. Selection on biomass alone may result in a slight increase in total cineole yield per tree but, in this experiment, it resulted in a reduction in mean leaf cineole concentration. Leaf cineole concentration used in conjunction with biomass may be a useful selection criterion in the absence of data for total mass of cineole produced per tree.     

Estimating the volume of Australian hardwoods using centroid sampling

Centroid sampling was tested on 18 sample trees of Flindersia brayleyana and 124 sample trees of five species of Eucalyptus all of which were measured in detail. Volumes of the main bole of each tree and of logs (length approx. 6 m) derived from each bole were estimated using both Huber's formula and centroid sampling. These estimates were compared with ‘true’ volume obtained by summing the volumes derived using Smalian's formula of all the measured short sections comprising the main bole and each log respectively.

The mean error of the centroid estimate of volume of the main bole was not significant for Eucalyptus sieberi and E. diversicolor and was less than that derived from Huber's formula for all species except E. regnans. When all species were combined, the centroid estimate was clearly more accurate, its mean error (-2%) being just significant (p=0.046). Centroid sampling also gave more accurate estimates of the volume of the component logs.

Results of this study and earlier work suggest that centroid sampling is applicable to tree species of both excurrent and deliquescent growth habit.     

Genetic variation and gains for two generations of Eucalyptus dunnii in China

One hundred and forty-two Eucalyptus dunnii seedlots including 66 families and 1 bulk seedlot from natural stands, 52 families and 4 bulk seedlots from genetically-improved (first-generation) sources and 1 local plus-tree seedlot were established in trials in Yunnan, China, in 2007 and 2008. These were assessed for growth up at ages 6½ years and 5½ years, respectively. Significant differences (P < 0.05 or P < 0.01) among seed sources existed in both trials at most ages. The seedlot of local E. dunnii plus-trees proved to be markedly superior for volume over other sources, all of Australian origin, in both trials. On average, exotic improved seedlots outperformed unimproved natural stand seedlots, although in the 2008 trial, tree volume at an age of 5½ years of two natural stand seedlots exceeded that of some improved seedlots. Estimates of heritabilities for individual tree volume ranged from 0.09 ± 0.07 up to 0.29 ± 0.16 and genetic correlations between early age (1½ to 2½ years) individual tree volume and that at final assessment (5½ to 6½ years) ranged from 0.29 ± 0.12 to 0.89 ± 0.22. Heritabilities and correlations generally increased with age, but progressive within-plot thinning may have biased estimates of genetic parameters beyond the early assessments. The best seed orchard seedlot in each trial offered modest stem volume gains over natural stand seeds ranging from 11% to 13%. Markedly higher gain, an additional 25%, could be obtained by using seedlots of only the best seed orchard families. Genetic gains in tree volume estimated for future seed orchards developed from the trials ranged from around 8% up to 27%.     

Effect of different Acacia acuminata variants as hosts on performance of sandalwood (Santalum spicatum) in the northern and eastern Wheatbelt,Western Australia

The effect of seven ‘jam variants’ (Acacia acuminata typical variant, A. acuminata narrow-phyllode variant, A. acuminata small-seed variant, A. acuminata/burkittii variant I, A. acuminata/burkittii variant 2, A. burkittii and A. oldfieldii) on the survival and growth of sandalwood (Santalum spicatum) was examined in two relatively low-rainfall locations, Dowerin and Morawa, in the northern and eastern Wheatbelt of Western Australia. During the course of the trial (2000–2008) the mean annual rainfall was only 326 mm at Dowerin and 259 mm at Morawa. In July 2000, seedlings from 84 families from 18 separate populations and representing each of the seven different jam variants were planted on cleared farmland at both locations. A total of 4032 host seedlings were planted at each site. At host age 2 y (April 2002), S. spicatum seeds were sown near 1807 host plants at the first site and near 1397 hosts at the second.

The different jam variants were associated with clear differences in sandalwood performance at both sites. At age 1 y, mean survival of sandalwood was significantly greater near A. acuminata small—seed variant (64%) and A. acuminata narrow-phyllode variant (50–54%) than near A acuminata typical variant (21–34%). This pattern of sandalwood survival between the different jam variants was similar at age 6 y.

At age 6 y, the mean stem diameter (at 150 mm above ground) of sandalwood was the greatest near A. acuminata small-seed variant within each site: 62 mm at Dowerin and 47 mm at Morawa. The mean stem diameter of sandalwood near A. acuminata typical variant was 51 mm at Dowerin and only 25 mm at Morawa.

Stem borers were more common in A. acuminata typical variant than in the other jam variants at Dowerin. No borers were observed in the jam variants at Morawa. At both sites, gall rust was observed in each of the jam variants except A. oldfieldii.     

Mapping tree stress associated with urban pollution using the WorldView-2 Red Edge band

A small urban park in Yerevan, Armenia, was studied using biogechemical analysis of the tree canopy, field spectral reflectance measurements of tree leaves, simulated WorldView-2 multispectral data generated from the leaf spectra, and two summer images of real WorldView-2 data. The tree canopy of the park is dominated by two trees, Robinia pseudoacacia L. (locust) and Fraxinus excelsior L. (ash). The Highest values of lead, nickel, molybdenum, copper and zinc were found in leaves harvested from trees adjacent to the streets, whereas most of the lowest values for those metals were found in the interior of the park. A t-test of the field spectral measurements indicated that the green and red edge spectral reflectance of leaves from trees near the streets was significantly higher than that of leaves of trees in the interior (p < 0.05). However, in simulated WorldView-2 multispectral data, the street and interior leaves were only statistically separable in band 6 (Red Edge) raw data and hyperspherical direction cosine (HSDC) normalized band 6 data. HSDC-normalized band 6 digital numbers from real WorldView-2 data of 16 June and 9 August 2011 from trees adjacent to the streets were statistically higher than the interior locations for both dates. Maps of anomalously high HSDC-normalized band 6 values show a concentration on the park edges, suggesting vehicle pollution may indeed be the cause of the observed patterns.     

Delinquency and drug use among adolescents and emerging adults: The role of aggression,impulsivity, empathy,and cognitive distortions

Risk behaviors are well known to be higher in adolescents and emerging adults. Drug use and delinquency present several common predictive factors. The aim of the present study was to assess the contribution of individual factors (aggression, impulsivity, empathy, and cognitive distortions) to delinquent behaviors, alcohol use and cannabis consumption among adolescents and emerging adults. Participants were between 15 and 25 years of age (M = 18.64 years, SD = 2.61); 325 were adolescents (15–18 years of age, M = 16.56, SD = 1.11, 56.31% of women) and 283 were emerging adults (19–25 years, M = 21.03, SD = 1.62, 50.88% of women). They completed self-report validated questionnaires. Multiple regression analyses showed that all individual factors significantly predicted delinquency. Impulsivity and empathy significantly predicted alcohol use. Concerning cannabis use, impulsivity is the only significantly associated predictor. Moderation analysis showed that specific associations were stronger in adolescents, whereas others were stronger in emerging adults. All these variables explained 69% of the variance of delinquency, 31% of the variance of alcohol use, and 18% of the variance of cannabis use. This model demonstrated acceptable goodness-of-fit criteria. These results may have implications for prevention and intervention.     

Micropropagation of Eucalyptus cloeziana mature trees

Eucalyptus cloeziana is a species of great commercial interest due to the technical characteristics of its wood. However, the expansion of areas planted is limited by difficulties encountered with its clonal propagation. The objective of this study was to develop a method for cloning select adult trees of this species by a micropropagation technique. Epicormic shoots were induced in branches of adult trees and were viable as explants for in vitro establishment. Shoots were multiplied in vitro using Woody Plant Medium (WPM) culture supplemented with 6-benzylaminopurine (BA) and α-naphthaleneacetic acid (NAA) growth regulators. The optimum concentration of these for promoting proliferation of shoots was genotype-dependent. The best multiplication results were obtained with BA concentrations greater than 0.60 mg L^–1 combined with 0.10 mg L^–1 NAA for adult tree genotypes numbered 03 and 13, while for tree 05 the optimal result was found for the shoots cultured in culture medium free of the growth regulator NAA. In vitro shoot elongation it was obtained in WPM supplemented with 0.1 mg L^–1 BA; a pulse treatment with gibberellic acid (GA₃) was found to be of no value. The ex vitro rooting and acclimatisation of micro-cuttings were successful in mini-incubators—adventitious roots formed directly on explants, providing propagules to establish a clonal micro-garden of E. cloeziana select adult trees.     

Wood density at breast height as estimate of the whole tree density in Grevillea robusta

To validate the relationship between whole-tree average density and wood density at breast height, 60 Grevillea robusta trees were sampled from north-eastern Argentina plantations. Wood basic density was measured at five height levels in each tree. A weighted average density was calculated for each tree and a linear regression was calculated using whole-tree density as the independent variable and wood density at breast height as the regressor. The coefficient of determination (R²), standard error and mean percentage error were 81%, 12.7 kg m^–3 and 10.2% respectively, showing a close association between variables. Wood density at breast height is useful for estimating wood density of the whole tree in G. robusta.     

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.     

Contrasting water use patterns of two important agroforestry tree species in the Mt Elgon region of Uganda

ABSTRACT

Lack of information on water use of key agroforestry species is an obstacle to understanding their influence on crop productivity. Cordia africana and Albizia coriaria are the dominant tree species of smallholder farming systems in the Mt Elgon region of Uganda and have multiple uses in agroforestry systems. This study deployed six sap flow meters on stems of three selected trees each of C. africana and A. coriaria on-farm. The objective of the study was to assess the daily water use patterns of these agroforestry tree species at different times of the year. We measured the daily sap flow of these two species using the heat ratio method over a period of 18 months. There was a significant main effect of the interaction between tree species and season on daily water use. The two species show contrasting patterns of seasonal water use across leaf shedding stages characterised by episodes of reverse flow in A. coriaria at specific periods of the year. We propose that reverse flows in A. coriaria were triggered by leaf shading while the zero flows in C. africana, which occurred during rainfall events, could have resulted from a lag phase, an indication that the two species may have different water-use strategies. Although C. africana uses 12–15 l day^?1 and A. coriaria uses 20–32 l day^?1 based on the study trees, C. africana generally uses 12% more water than A. coriaria on a standardised daily basis. Albizia coriaria exhibited radial variation of sap velocities between the inner and outer thermocouples at different periods of measurement, a phenomenon worth investigating further. The leaf shedding patterns of the two trees provide an opportunity for maximising the temporal complementarities of agroforestry systems where these trees exist. This knowledge of C. africana and A. coriaria tree water use provides critical insight for developing successful long-term tree monitoring and management programs in agroforestry systems.     

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.     

Domestication of northern sandalwood (Santalum lanceolatum,Santalaceae) for Indigenous forestry on the Cape York Peninsula

ABSTRACT

Over recent decades there has been considerable private investment in developing a sandalwood (Santalum spp.) industry due to the high international demand for products derived from its heartwood. While Santalum album (Indian sandalwood) has been the primary species used in these investments, other species may also have potential for commercialisation. In Cape York Peninsula (CYP), where Santalum lanceolatum occurs naturally, there are limited options for industry development, but research has shown that sandalwood products may provide an opportunity. The potential to incorporate sandalwood into existing Indigenous land management plans and further extend this into commercial plantings provides the opportunity to utilise an endemic tree species for economic development. This paper summarises participatory research with two Indigenous communities in the CYP to evaluate and improve conservation and development outcomes through sandalwood domestication.

The project has been implemented through a series of community consultations with the aim of reaching a consensus on how a sandalwood industry could develop and facilitating community involvement in the technical aspects of domestication and forest development. Differences in the progress achieved in the communities are significant and depend on the cultural and municipal structures and relationships within the communities.

The participatory approach in the northern part of the CYP has resulted in the establishment of important S. lanceolatum genetic resources that will be used to underpin the development of an industry: (1) sandalwood demonstration plantings (Bamaga and Lockhart River); (2) clonal seed orchard (Bamaga); (3) conservation enrichment plantings (Bamaga) and (4) two progeny trials (Bamaga). The survival of S. lanceolatum from the northern CYP has been good in both the progeny trials and the grafted seed orchards; however, sandalwood from other sources (other sandalwood species including S. album, Santalum austrocaledonicum and Santalum leptocladum and non-local provenances of S. lanceolatum) have performed poorly in the northern CYP. This paper outlines the history of sandalwood exploitation in CYP, which has led to the need for interventions to improve its conservation, as well as efforts to domesticate sandalwood so that the Traditional Owners of the northern CYP can benefit from this species.     

Radial variation of anatomical features,physicomechanical properties and chemical constituents and their potential influence on the wood quality of 45-year-old Eucalyptus propinqua

The potential commercial use of Brazilian-grown Eucalyptus propinqua for furniture and other applications has been largely ignored in favour of native woods. In part, this results from unfamiliarity with the properties of this species, especially in mature trees. To address this gap in our knowledge, we have characterised the wood anatomy, physical and mechanical properties, and chemical constituents in the radial direction of five E. propinqua trees sampled at breast height. The anatomical features follow the typical radial pattern, which includes differences in juvenile wood when compared with mature wood. Basic density peaked in samples formed 17–30 years from the pith before decreasing at ages 38–45 years (a decline reflecting the low extractive content of the sapwood). We did not observe a pattern of radial variation in mechanical properties. Extractive content increased up to 25–30 years of age and then decreased significantly at 38–45 years with values similar to those of the wood from the sample close to the pith, while the holocellulose content presented inverse behaviour. The lignin content did not change radially. We concluded that many features of E. propinqua wood vary radially, as with many other species of the Eucalyptus genus. This variation, however, was not evident in important mechanical properties and was muted in others. The quality of the wood makes it suitable for many applications, especially after some 17 years of age when ‘mature’ wood, indicated by a declining (and non-significant) rate of increase in fibre and vessel length, is first produced.     

Bell miner associated dieback: nutrient cycling and herbivore crown damage in Eucalyptus propinqua

Various interactions appear to be involved in bell miner associated dieback (BMAD) of eucalypts. Native bell miner birds (Manorina melanophrys) defend the psyllids from predation by other birds while a dense understorey (notably Lantana camara) appears to favour the bell miners. The understory is likely to influence soil nutrient availability to the trees by changing the carbon to nitrogen ratio. We investigated the link between soil and leaf nutrient status and crown health as measured by crown index (CI) for Eucalyptus propinqua. Study sites included Bald Knob State Forest (SF), Donaldson SF, Mt Lindesay SF around Woodenbong and two locations on a Toonumbar private property in north-eastern New South Wales. Comparison of E. propinqua leaf macro- and micronutrient status using the ‘paired data sign test’ detected leaf nutrient differences between lightly and severely BMAD-affected tree crowns. Single and multivariate analysis investigated nutrient association with CI. Sign test results across all sites indicated that leaf iron content in trees with low CI (less healthy trees) was significantly higher (P = 0.01) than in healthy trees. In the three SFs the affected crowns also had significantly higher nitrogen to potassium ratios (P = 0.02). Other elements correlated with low CI were low boron (P = 0.06) across all sites and high zinc (P = 0.09) and low sodium values (P = 0.09) for Toonumbar sites. The correlation between soil and leaf nutrients was not significant and we found no significant correlations between soil nutrients and CIs. We did not detect any clear association between understorey (L. camara) and soil nutrients. During leaf sampling we found few psyllids but many concealer moth caterpillars. The scarcity of psyllids during sampling, inconclusive nutrient cycling results and nutrient correlations with CI were likely to be due to drought. Resampling under normal weather conditions with more typical organic matter decomposition rates is recommended.     

Potential of two tree shelters to aid the early establishment and growth of three Australian tree species on the Darling Downs,south-east Queensland

The ability of the commercial tree shelter Growtube® and a perforated sheet metal shelter (Mauri) to improve the growth and survival of seedlings of Casuarina cristata, Eucalyptus moluccana and Melaleuca linariifolia was tested on the Darling Downs in south-east Queensland. The 0.9 m high tree shelters were removed after 2 years and at this time tree survival was unaffected by shelter type for all 3 species. Over a 44-month period, neither shelter improved the height growth of C. cristata or E. moluccana. Growtubes significantly (P < 0.05) increased the height of M. linariifolia and, at the time of shelter removal, trees in Growtubes were 23% taller than control trees. Differences in height decreased after the Growtubes were removed and 18 months later were no longer significant (P > 0.05). The early deterioration of the growtubes would have decreased their ability to create a beneficial microclimate, leading to the absence of any height increases for C. cristata and E. moluccana and small and non-persistent height increases for M. linariifolia. Thus, Growtubes were considered unsuitable for the environment in which they were tested. The cost of establishing a tree without a tree shelter, with a Mauri tree shelter and with a Growtube tree shelter was estimated to be $1.82, $3.08 and $5.12, respectively. During the first two years, a further $1.79 per tree was spent on materials used to replace damaged Growtubes.     

Investigating optimal site conditions for flower bud production in Eucalyptus smithii orchards in South Africa

Eucalyptus smithii is an important commercial forestry species in South Africa. The species’ shy and erratic flowering tendencies hinder its genetic improvement and seed production. Breeders and seed producers are highly dependent on paclobutrazol (PBZ) applications for encouraging flower and seed production in E. smithii orchards. During the summer of 2003/04, an E. smithii flowering field trial series was established across a range of high elevation (1568–1828 m asl), cool temperate (13.8–15.5°C mean annual temperature (MAT)) commercial forestry sites in South Africa. The main objective was to investigate the interaction between PBZ and a range of climatic and landscape factors on E. smithii floral bud (umbel) production. The main aim was to define optimum environmental conditions for E. smithii umbel production and potential orchard establishment. In the fifth and sixth years after planting, 64% and 83% of the control (nil PBZ) grafted trees and 94% and 94% of PBZ-treated trees produced umbels. In the fifth year, PBZ application increased mean (across-site) umbel production per tree by 132%. Regardless of whether PBZ was applied or not, mean umbel production varied markedly across sites. In the absence of PBZ application, E. smithii test orchards located on south-west facing slopes in high elevation (>1550 m asl) areas at the lower end of the applied MAT range were generally the most productive on the basis of umbel crop. The study demonstrated that, through careful site selection, dependency on PBZ to achieve satisfactory umbel production in reproductively mature E. smithii trees may be substantially reduced. Within the elevation and MAT ranges applied in the trial series, E. smithii orchards situated in low positions in the landscape were at high risk of being severely damaged by frosts.     

Using tree hollow data to define large tree size for use in habitat assessment

Habitat assessments often require observers to estimate tree hollows in situ, which can be costly, destructive and prone to bias. An alternative is to count the number of trees above a specific size. The size at which a tree develops hollows differs substantially among tree species. To assist with setting standards for habitat assessment we defined a large tree as the size at which a species has a 50% probability of supporting a 2-cm diameter hollow. We estimated this size for 68 species using a meta-analysis based on 18 data sources. We found that large tree size ranged from 21 to 106 cm diameter at breast height (DBH). Each species was attributed to vegetation types (formations and classes) to explore variation in large tree sizes. Despite considerable variation within vegetation classes and formations, our results suggest that a large tree size of approximately 50 cm DBH may be appropriate for most vegetation types, with lower estimates in semi-arid vegetation (~30 cm) and higher estimates in wet sclerophyll forests (~80 cm). Our estimates provide empirical support for defining large trees at species vegetation class and formation levels within New South Wales, and highlights the need for more empirical data.     

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.     

Self-Reported History of Sexual Coercion and Rape Negatively Impacts Resilience to Suicide Among Women Students

A substantial literature has documented that sexual abuse relates to suicidal behaviors but relatively less is known about resilience to suicide, especially cognitive deterrents to suicide. The present study investigated the effects of a history of sexual victimization on reasons for living. Female participants (N = 138; M age = 24.4 years; SD = 7.3 years; range = 18 to 53 years; 79% Caucasian) completed the Sexual Experiences Survey (SES) and the Reasons for Living (RFL) Inventory. According to SES responses, participants were classified into 5 mutually exclusive groups: no victimization, sexual contact, sexual coercion, attempted rape, and rape. Analyses of variance showed that degree of sexual victimization had a significant effect on the RFL Total scale and 2 subscales (Survival and Coping Beliefs; Moral Objections). The general pattern was that mean RFL scores in the no victimization group were significantly higher than the mean scores in the sexual coercion and rape groups. An implication is that having a history of sexual victimization, especially sexual coercion and rape, limits one's later reasons for not committing suicide. Bolstering these modifiable deterrents to suicide should be part of suicide prevention efforts among at-risk women.     

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.