Plantation-grown Eucalyptus Research Articles

Evaluation and prediction of bending properties of glulam beams made from young plantation-grown Eucalyptus nitens

ABSTRACT Interest in making glulam from plantation-grown Eucalyptus nitens has increased, but current structural timber standards were not designed for species grown in plantations. Additionally, the applicability of classical composite beam theory remains uncertain due to the unique features of this species. This study was designed to assess the hypothesis that the bending performance of glulam made from young plantation-grown E. nitens is reliable and predictable. We tested the hypothesis through experimental procedures and theoretical and statistical analyses. First, we assessed the bending performance of 20 glulam beams, which were manufactured in five configurations. Second, we compared our experimental results with predictive values to evaluate the accuracy of methods in current standards. Third, in our pursuit of improved predictive tools, we developed theoretical and parametric models using mechanical properties of the board elements. Our improved models showed a decreased deviation in both stiffness and strength values. A Monte Carlo simulation was used to determine the distribution for both stiffness and strength. The results validated that this product can be allocated a GL grade using current standards and the bending performance is predictable. The study enhances confidence in incorporating E. nitens into glulam products and offers valuable data for future specification modifications.

Long-term growth data of plantation-grown Eucalyptus established in south-eastern Uruguay

Behind beef production, Eucalyptus logs oriented to kraft pulp production represent Uruguay's second-largest export product. In this context, the analysis of long-term growth data of plantation-grown Eucalyptus forests acquires a material relevance. A total of 2208 permanent plots representing longitudinal growth data of Eucalyptus globulus, Eucalyptus maidenii, Eucalyptus dunnii, and Eucalyptus smithii trees were analyzed and modeled. The plots are part of a more extensive set established since 2012 on a forest state of over 22,000 ha planted. The selected plots were of variable shape, varying in size between 200 and 1000 m2. Both planted and coppiced areas were included. Tree-level data (diameter at the beast height and height) was measured on each plot over a different number of years. Plantation ages, at the time of measurement, ranged from 1 to 18 years. The forests were all planted for the first time under the context of degraded grasslands, where there was no other better alternative use for the land. Soils are not very deep, of medium-to-coarse texture, and have low natural fertility. The dominant land cover was grasslands. The results highlight the variability in site quality. Stand density varied between 100 and 2500 trees per ha (TPH), with a site index (SI) at base age 11 ranging between 12 and 38 m. A strong relationship between dominant height (DH) and standing volume (TV) is evident, reinforcing that SI is still a valuable quantity to represent site quality. A set of anamorphic SI curves fitted to the DH data showed that E. dunnii and E. smithii height far exceeds that of E. globulus and E. maidenii at the same age, with an average SI of 28 and 31 m, respectively. Similarly, a family of TV curves fitted to each species as a function of DH, TPH, basal area, and age showed that the implicit current annual growth (CAI), given the model form used, peaked between 7 and 9 years. Depending on the stocking and site index considered, the CAI varied; but, in all cases, the CAI of E. dunnii was the highest, followed by E. smithii, and then E. maidenii and E. globulus in descending order. As an example, for a fixed density of 1100 TPH, the peak CAI was almost 48.6 m3|ha|yr for E. dunnii (SI28), approximately 42.1 m3|ha|y for E. smithii (SI31), and 17.8-21.3 m3|ha|yr for E. maidenii and E. globulus (SI23).

Janka Hardness Evaluation of Plantation-Grown Eucalyptus nitens for Engineered Flooring Applications

Hardness is commonly used to determine the suitability of a timber species for flooring applications. In this study, Janka hardness test is conducted on sawlog managed Eucalyptus nitens and regrowth forest Eucalyptus obliqua sourced from Tasmania, Australia. Plantation E. nitens timber is currently entering the Australian market and the feasibility of using this fast grown species in value added applications such as timber flooring is advantageous. Further to testing Janka hardness on solid timber samples, a regime of engineered timber flooring prototypes consisting of plantation E. nitens top layers, veneers and solid densified E. nitens boards were developed and subjected to Janka hardness test. The results were compared against solid E. obliqua flooring and a commercially available engineered flooring product with Tasmanian Oak top layer. The results showed that Janka hardness of plantation grown E. nitens, and E. obliqua currently available in the market are lower than the values published in the literature. This indicates that the material properties of fast grown plantation timber and regrowth forest material are different to the native forest timber properties published decades earlier. Furthermore, some of the tested engineered flooring prototypes showed similar behaviour to timber flooring products currently in market, suggesting that E. nitens engineered flooring would be suitable for domestic/light commercial flooring applications despite the general conception of unsuitability due to lower densities.

Early Monitoring of Health Status of Plantation-Grown Eucalyptus pellita at Large Spatial Scale via Visible Spectrum Imaging of Canopy Foliage Using Unmanned Aerial Vehicles

Eucalyptus is a diverse genus from which several species are often deployed for commercial industrial tree plantation due to their desirable wood properties for utilization in both solid wood and fiber products, as well as their growth and productivity in many environments. In this study, a method for monitoring the health status of a 22.78 ha Eucalyptus pellita plantation stand was developed using the red-green-blue channels captured using an unmanned aerial vehicle. The ortho-image was generated, and visual atmospheric resistance index (VARI) indices were developed. Herein, four classification levels of pest and disease were generated using the VARI-green algorithm. The range of normalized VARI-green indices was between −2.0 and 2.0. The results identified seven dead trees (VARI-green index −2 to 0), five trees that were severely infected (VARI-green index 0 to 0.05), 967 trees that were mildly infected (VARI-green index 0.06 to 0.16), and 10,090 trees that were considered healthy (VARI-green index 0.17 to 2.00). The VARI-green indices were verified by manual ground-truthing and by comparison with normalized difference vegetation index which showed a mean correlation of 0.73. This study has shown practical application of aerial survey of a large-scale operational area of industrial tree plantation via low-cost UAV and RGB camera, to analyze VARI-green images in the detection of pest and disease.

Characterization of Diameter Distribution and Prediction of Weibull Parameters Equation for Plantation-grown Eucalyptus Species

Aim: To characterization of the diameter distribution and prediction of Weibull parameters of a plantation-grown Eucalyptus species.
 Study design: Stratified sampling method was adopted, in which the plantation was stratified into four age series.
 Place and duration of study: Afaka Forest Reserve, one month.
 Methodology: Fifty (50) sample plots of 20 x 20 m were laid across the age series. In each of the plot, all the trees were counted and data of variable of interest was collected and processed. A separate Weibull distribution is fitted to the diameter at breast height (dbh) frequency data from each of the plot for the estimation of Weibull parameters (location, scale and shape). The data set obtained from the Weibull parameter estimate was then used to develop regression equations with the stand variables. Coefficient of Determination (R2) and Root Mean Square Error (RMSE) was used as goodness of fit test.
 Results: The result on the stand characteristics revealed that, the mean diameter at breast height (dbh) ranges between 13.4 – 18.2 cm across the four stands. This indicates that the species are still of pole sizes. The average site productivity of the species ranges between 24.0 m to 37 m at an index of 25 years. The mean Basal area varies between 14.13 to 26.85 m2 per ha, while the average tree total height ranges between 24.6 to 28.2 m across the four species. The result on diameter class distribution shows that most of the species fell within dbh class of 11 -20 cm class except E. cloeziana in which the highest frequency fell into 16 – 20cm dbh class. Best equation were selected for each of the Weibull parameters (α, β, ) per species based on fit statistics. The formation of straight line pattern from the plotted normal probability plots indicates the adequacy of the selected models for predicting Weibull parameters. A fluctuation pattern exists between the Weibull parameters and the stand characteristics. this may be due to variation in climatic factor, most especially fluctuations in rainfall pattern in the area at that particular period.
 Conclusion: The ease of fit and high value of coefficient of determination of the models in this study has re-affirmed the use of Weibull parameter in prediction of stand characteristics as been suggested by many authors in the literature.

Incidence and Severity of End-Splitting in Plantation-Grown Eucalyptus pellita F. Muell. in North Borneo

Eucalyptus pellita F. Muell. is currently the predominant tree species deployed for tree plantation establishment in some parts of Borneo, particularly Sabah state, Malaysia. Its low disease susceptibility, good growth and form, and desirable wood properties make E. pellita particularly suitable for plantation development in the wet tropical regions of south-east Asia. In spite the many positive traits, practical field observations indicate that the species is susceptible to end-splitting. There is some anecdotal evidence to suggest a genetic relationship with the incidence of end-split, although these observations were not statistically tested. This study evaluates the occurrence of end-splitting in five-year old plantation E. pellita in Sabah as affected by family and growth attributes. An existing progeny tree breeding trial, involving seeds that originated from Papua New Guinea, China, Vietnam, Australia, Sabah, and Sarawak with 106 families, was used to carry out the split assessment. Logs from the second thinning were cut into 2.2-m-long sections. The end splits were measured three days later; the incidence and severity of splitting were assessed at both the large and small ends of each log by using a designated split scoring system. The study shows that 99% of all log cross sections (per cut surface) experienced signs of splitting, with an average of 2.7 splits per cut surface. Overall, 54% of all splits were classed as ‘Three-Quarter Radial Splits’ while the occurrence of internal splits was negligible. Split severity showed a heritable and significant difference (h2 = 0.24 at p ≤ 0.05) among the family levels. Splitting was also significantly related to growth factors such as tree height and diameter at breast height (DBH). The findings suggest that end-splitting is caused by family–environment interactions. This offers the opportunity to improve the wood resource of E. pellita via breeding strategies.

Pathogenicity of Teratosphaeria species on Eucalyptus grandis and selected hybrids in Uganda

ABSTRACT Teratosphaeria stem canker is one of the most important diseases to have emerged on non-native plantation-grown Eucalyptus trees cultivated globally. The study assessed the pathogenicity of two Teratosphaeria species associated with Teratosphaeria stem canker and the susceptibility of Eucalyptus grandis and six commonly grown Eucalyptus hybrids to these fungal species in Uganda. The inoculation trials indicated that Eucalyptus species and hybrids were susceptible to fungal pathogens used. A comparison of Eucalyptus species and hybrids for each fungal species showed that GC 540 and GC 796/2 are the most susceptible hybrids to T. zuluensis and T. gauchensis respectively while hybrid clone GU 8 had a higher tolerance to both fungal species. GC 540 was also tolerant to T. gauchensis while F2 and GC 550 were tolerant to T. zuluensis. Eucalyptus grandis sourced from Australia (F2) showed a higher tolerance than Eucalyptus grandis from South Africa (F1). The results further revealed that both Teratosphaeria zuluensis and Teratosphaeria gauchensis are pathogenic to Eucalyptus species and hybrids. The generated information indicates that there is an opportunity to sustainably manage Teratosphaeria stem canker disease if tolerant species are grown in areas with high disease impact.

Cryphonectriaceae on Myrtales in China: phylogeny, host range, and pathogenicity.

Plantation-grown Eucalyptus (Myrtaceae) and other trees residing in the Myrtales have been widely planted in southern China. These fungal pathogens include species of Cryphonectriaceae that are well-known to cause stem and branch canker disease on Myrtales trees. During recent disease surveys in southern China, sporocarps with typical characteristics of Cryphonectriaceae were observed on the surfaces of cankers on the stems and branches of Myrtales trees. In this study, a total of 164 Cryphonectriaceae isolates were identified based on comparisons of DNA sequences of the partial conserved nuclear large subunit (LSU) ribosomal DNA, internal transcribed spacer (ITS) regions including the 5.8S gene of the ribosomal DNA operon, two regions of the β-tubulin (tub2/tub1) gene, and the translation elongation factor 1-alpha (tef1) gene region, as well as their morphological characteristics. The results showed that eight species reside in four genera of Cryphonectriaceae occurring on the genera Eucalyptus, Melastoma (Melastomataceae), Psidium (Myrtaceae), Syzygium (Myrtaceae), and Terminalia (Combretaceae) in Myrtales. These fungal species include Chrysoporthe deuterocubensis, Celoporthe syzygii, Cel. eucalypti, Cel. guangdongensis, Cel. cerciana, a new genus and two new species, as well as one new species of Aurifilum. These new taxa are hereby described as Parvosmorbus gen. nov., Par. eucalypti sp. nov., Par. guangdongensis sp. nov., and Aurifilum terminali sp. nov. Pathogenicity tests showed that the eight species of Cryphonectriaceae are pathogenic to two Eucalyptus hybrid seedlings, Melastoma sanguineum branches, and Psidium guajava and Syzygium jambos seedlings. The overall data showed that Chr. deuterocubensis is the most aggressive, followed by Par. eucalypti. Significant differences in tolerance were observed between the two tested Eucalyptus hybrid genotypes, suggesting that disease-tolerant genotypes can be selected for disease management in the Eucalyptus industry.

Characterisation of Physical and Mechanical Properties of Unthinned and Unpruned Plantation-Grown Eucalyptus nitens H.Deane & Maiden Lumber

The use of fast-growing plantation eucalypt (i.e., pulpwood eucalypt) in the construction of high-value structural products has received special attention from the timber industry in Australia and worldwide. There is still, however, a significant lack of knowledge regarding the physical and mechanical properties of the lumber from such plantation resources as they are mainly being managed to produce woodchips. In this study, the physical and mechanical properties of lumber from a 16-year-old pulpwood Eucalyptus nitens H.Deane & Maiden resource from the northeast of Tasmania, Australia was evaluated. The tests were conducted on 318 small wood samples obtained from different logs harvested from the study site. The tested mechanical properties included bending modulus of elasticity (10,377.7 MPa) and modulus of rupture (53 MPa), shear strength parallel (5.5 MPa) and perpendicular to the grain (8.5 MPa), compressive strength parallel (42.8 MPa) and perpendicular to the grain (4.1 MPa), tensile strength perpendicular to the grain (3.4 MPa), impact bending (23.6 J/cm2), cleavage (1.6 kN) and Janka hardness (23.2 MPa). Simple linear regression models were developed using density and moisture content to predict the mechanical properties. The variations in the moisture content after conventional kiln drying within randomly selected samples in each test treatment were not high enough to significantly influence the mechanical properties. A relatively high variation in the density values was observed that showed significant correlations with the changes in the mechanical properties. The presence of knots increased the shear strength both parallel and perpendicular to the grain and significantly decreased the tensile strength of the lumber. The results of this study created a profile of material properties for the pulpwood E. nitens lumber that can be used for numerical modelling of any potential structural product from such a plantation resource.

Nine novel species of Huntiella from southern China with three distinct mating strategies and variable levels of pathogenicity

ABSTRACTThe ascomycete genus Huntiella (Microascales) has a cosmopolitan distribution and occurs on a wide range of woody plants. Little is known regarding the identity, diversity, origin, or impact of these fungi in China. Recently, isolates of Huntiella spp. were collected from stumps of freshly felled trees or wounds on plantation-grown Eucalyptus in Guangdong, Guangxi, Fujian, and Hainan provinces of southern China. Additional isolates were obtained from stumps of Acacia confusa near Eucalyptus plantations in Hainan Province. The aim of this study was to identify these Huntiella species and to test their pathogenicity on Eucalyptus seedlings. Morphology and multigene phylogenies of the nuclear rDNA internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) region and partial β-tubulin (BT1) and translation elongation factor 1α (TEF1α) genes revealed nine previously unknown Huntiella species, eight from Eucalyptus and one from A. confusa. The mating types of these species were determined, showing that seven are heterothallic, one is homothallic, and one is unisexual (MAT1-2-1 gene). Pathogenicity tests showed that the nine Huntiella species can produce lesions on Eucalyptus seedlings, larger than wounds caused by controls on these plants. This study provides a basic understanding of the distribution, diversity, and pathogenicity of Huntiella species in southern China.

Processing sawn wood from thinned, unpruned 17-year-old Eucalyptus dunnii in southern China

SummarySixty logs of 17-year-old thinned, unpruned plantation-grown Eucalyptus dunnii representing 10 trees from each of 2 provenances were obtained from a field-trial in central Guangxi Province, China, and processed in a nearby sawmill to produce dried appearance-grade sawn wood suitable for manufacture of short-length flooring. This study’s objectives included determining: interrelationships between log end-splitting and growth stress measured on standing trees and important wood behaviour during processing; relationships between log external features and sawn product recovery; the potential for improvement in processing and/or product quality with the application of a steam reconditioning treatment; and differences in product value and processing characteristics between two provenances of E. dunnii.Boards were air-dried and kiln-dried in two matched batches and one batch was subsequently given a steam reconditioning treatment. For prediction of processing characteristics, the measured displacement on standing tree stems associated with growth stress release was moderately useful for prediction of log end-splitting but not significant for any other characteristic tested, and log end-splitting was not a significant predictor of recovery or product value. Log diameter measures and sweep were the only significant predictors of recovery. Diameter was sufficiently large in some logs to meet D-grade requirements according to Australian (VicForests) log grading standards. The estimated mill door values of sawn product obtained per log cubic metre for D-grade and residual-grade logs (below VicForests sawlog specifications) were RMB 1045 and RMB 887, respectively (approximately AUD 190 and AUD 161, respectively). Steam reconditioning treatment significantly reduced cupping and increased width and thickness dimensions but the presence of severe non-drying-related defect limited the direct benefit of the treatment. There was no significant difference between provenances in product recovery, product value or log end-split severity.

Variation in Rotary Veneer Recovery from Australian Plantation Eucalyptus globulus and Eucalyptus nitens

The processing of Australian plantation-grown Eucalyptus globulus and E. nitens into rotary veneer was shown to produce acceptable recoveries. Three plantation sites for each species were sampled. Silvicultural treatments (thinning and pruning) and growing environments varied between sites. Graded veneer recoveries were dominated by D-grade veneer across all six sites. Variation between the E. nitens sites was evident, with recoveries differing between sites reflecting silvicultural treatments. However, only minimal variation in recovery was shown between the E. globulus sites. The presence of similar levels of defects across all E. globulus sites indicates that the intensive silvicultural management at one site studied was not effective in the production of clear wood, and may possibly have adversely affected grade recovery. Veneer value analysis demonstrated only minimal differences between E. globulus sites. More variation was observed in the E. nitens value analysis; however, intensive silvicultural management implemented did not necessarily result in higher veneer value.

Three new and important insect pests recorded for the first time in Colombian plantations

Subsequent to 1950, commercially propagated and non-native trees, including Pinus, Eucalyptus and Cupressus species in Colombian plantations, have been damaged by several native defoliating insects, residing mainly in the Lepidoptera (Geometridae), Phasmatodea (Heteronemiidae) and the Hymenoptera (Formicidae). We report on the relatively recent appearance of three important and damaging new insect pests of plantation-grown Pinus and Eucalyptus spp. in Colombia, two of which are not native to this country. These include Monalonion velezangeli (Hemiptera: Miridae), Glycaspis brimblecombei (Hemiptera: Psyllidae) and Pineus boerneri (Hemiptera: Adelgidae). This report provides information on the basic biology of these new pests, their hosts, areas of occurrence, likely origin and prospects for their management in the future.

Crown structure and vertical foliage distribution in 4-year-old plantation-grown Eucalyptus pilularis and Eucalyptus cloeziana

Tree growth and form are both influenced by crown architecture and how it effects leaf distribution and light interception. This study examined the vertical distribution of foliage in 4-year-old plantation-grown Eucalyptus pilularis Sm. and E. cloeziana F. Muell. trees. Leaf area (LA) distribution was determined at two different sites using allometric approaches to determine LA in crown sections and for whole trees. Leaf area was distributed more towards the upper crowns when canopies had been closed for longer. Leaf area was also skewed more towards the upper crowns for Eucalyptus pilularis than E. cloeziana. These species differences were consistent with differences in vertical light availability gradients as determined by point quantum sensors. Leaf area of individual branches was highly correlated with branch cross-sectional area (CSA) and whole-tree LA was closely related to stem CSA. Branch-level allometric relationships were influenced by site and crown position. However, the general allometric equations between stem size and whole-tree leaf area could be applied across sites. Results from this study suggest that pruning of live branches in these species should follow species-specific guides for the timing and height of pruning to optimise the effects on stem growth and form.

A diverse assemblage of Ophiostoma species, including two new taxa on eucalypt trees in South Africa

Fungi in the Ophiostomatales include important pathogens of trees as well as agents of wood stain, reducing the economic value of timber. They rely on insects, such as bark beetles, for dispersal and are commonly associated with wounds on trees. Although Ophiostoma spp. have been reported from eucalypt wood chips in South Africa, very little is known about the diversity of the Ophiostomatales, or their insect associates, on plantation-grown Eucalyptus spp. The aim of this study was to consider the diversity and distribution of the Ophiostomatales infecting fresh wounds on Eucalyptus trees in the country. Additionally, knowledge regarding their association with nitidulid beetles, which have previously been shown to carry Ophiostoma spp., was sought. Surveys were conducted in five provinces where Eucalyptus spp. are commonly grown, and the fungi collected were identified using morphological comparisons and multigene sequence phylogenies. Of the 139 isolates collected, five Ophiostoma spp. were identified including O. quercus, O. tsotsi and O. tasmaniense. These were from cut stumps as well as from the nitidulid beetles Brachypeplus depressus and Carpophilus spp. In addition, two new taxa in the O. stenoceras–Sporothrix schenckii complex were identified from Eucalyptus trees infested by Phoracantha semipunctata. The two new taxa are described as O. candidum sp. nov., and O. fumeum sp. nov., respectively. The results of this study clearly show that the diversity and ecology of Ophiostoma spp. on Eucalyptus trees in South Africa is poorly understood and that further studies are required to determine the possible economic relevance of these fungi.

Study on Collapse-Shrinkage Characteristics in Plantation-Grown Eucalyptus Wood under Continuous and Intermittent Drying Regimes

Collapse-type shrinkage is the greatest obstacle to prevent planted eucalypts from being used for solid wood products. In order to make the suitable drying schedules for high effective utilization of eucalypt wood, the total shrinkage and collapse on two species of difficult-to-dry E. urophylla and E.grandis wood under continuous and intermittent drying regimes were measured. The results show that total shrinkage and collapse in both eucalypts exhibited higher values for continuous drying than intermittent drying. With increasing drying temperature, total shrinkage and collapse increase in both drying regimes, while the increasing magnitude of both parameters becomes apparently larger for continuous drying than intermittent drying regime, in particular higher temperature condition. Properly elevating drying temperature to make up for the intermittent-waiting time may be allowed for intermittent drying regime. Drying duration at each intermittent drying period has a greater effect on total shrinkage and collapse of eucalypt wood. When more than a drying duration of 6 hours at an intermittent drying period is used, the differences in shrinkage and collapse between both drying regimes are very slight. Intermittent duration at an intermittent drying period has a comparatively larger effect on total shrinkage and collapse. Accordingly, we may draw a conclusion that intermittent drying regime is very likely to be a potential drying one suitable for collapse-prone lower-density plantation-grown eucalypt wood.

Corelation of Colorimetric Parameters with Collapse-Shrinkage Properties in Plantation-Grown Eucalyptus Based on Eco-Furniture Materials

In order to quantify the relationship between collapse-shrinkage properties and colorimetric parameters on plantation-grown eucalyptus as solid-wood furniture, measurements of the above-mentioned indices were carried out on five species of plantation-grown Eucalyptus (Eucalyptus urophylla, E.grandis, E.urophylla×grandis, E.grandis ×urophylla and E.cloeziana) under three kinds of heat-treat patterns(heat, steaming and combination of heat and steaming) and their correlations were investigated by means of regression analysis. Results showed that for the former four low-density prone-collapse eucalypt, collapse-shrinkage properties were strongly correlated with L* and △E*( R2 ≥0.85) under the above treated conditions, while weak linear correlation with a* and b*. For high-density E.cloeziana with extremely lower collapse, the four colorimetric indexes were lightly correlated with collapse-shrinkage properties. Thus, it can be concluded that L* and △Eab* may be regarded as the two primary and more reliable predictors of shrinkage-collapse parameters for low-density collapse-prone eucalypt wood.

Photosynthetic response to green crown pruning in young plantation-grown Eucalyptus pilularis and E. cloeziana

The loss of foliage through pruning of live branches may reduce tree growth or it may be compensated by photosynthetic up-regulation of the remaining crown. Here, the changes in light-saturated photosynthesis following pruning to remove 50% of green crown length were examined in 4-year-old Eucalyptus pilularis Sm. and Eucalyptus cloeziana F. Muell. trees. The objectives of the study were to: (1) compare leaf-level physiological (light-saturated photosynthesis ( A max), stomatal conductance ( g), transpiration ( T), dark respiration ( R d), quantum yield ( Φ), light compensation point ( Γ), water-use efficiency (WUE), nitrogen-use efficiency (NUE)) traits in species with contrasting crown dynamics and structure, (2) examine the effect of crown position on these traits, and (3) examine the effect of pruning on A max, g, T, WUE, NUE, leaf N and P concentrations and specific leaf area (SLA). Prior to pruning there were no differences in R d, Γ and Φ between E. pilularis and E. cloeziana but differences in A max, T, g, leaf N, leaf P, WUE, NUE and SLA. Whereas the rate of physiological processes ( A max, T, and g) and leaf N and P concentrations increased with crown height, R d, Γ, Φ and SLA declined along this vertical gradient, except in the upper crown of E. cloeziana where A max, T and g were not different to the lower crown. No up-regulation of photosynthesis or changes in leaf physiology occurred between 6 and 13 months after pruning in either species. The results provide an important basis for modelling pruning effects in process-based tree growth models.

Growth response following green crown pruning in plantation-grown Eucalyptus pilularis and Eucalyptus cloeziana

Pruning of live branches is performed to enhance wood quality in plantation trees. Stem, branch and wood properties may be altered following pruning from below, but the extent and duration of such effects are unknown for many plantation Eucalyptus species. The effect of 0%, 20%, 50%, and 70% green crown length removal on growth and wood quality was examined in 3.5-year-old plantation-grown Eucalyptus pilularis Sm. (blackbutt) and Eucalyptus cloeziana F. Muell. (Gympie messmate) trees on two subtropical sites in eastern Australia. Growth increment of the stem at breast height was not affected by 20% crown removal. However, stem increment at breast height was reduced for up to 8 months with 50% crown removal and up to 12 months with 70% crown removal. Pruning had no impact on height growth. However, the height of trees pruned to 70%, relative to the height of the surrounding unpruned trees, was temporarily reduced 12 months after pruning in both species. Stem form, stem taper, wood density, and residual branch growth above the pruned zone were unaffected by pruning. Owing to the fast vertical crown expansion, trees were able to rapidly compensate for leaf area removal without long-term reductions in stem growth. The implications for management operations utilizing pruning as a means of enhancing timber quality are discussed.

The effect of initial planting density on branching characteristics of Eucalyptus pilularis and E. grandis

Summary Branch-related defects can significantly decrease the quality of plantation eucalypt logs grown for solid-wood products. In this study we examined the effect of initial spacing on branching characteristics of 5-y-old plantation-grown Eucalyptus grandis and E. pilularis on the North Coast of New South Wales. For each sample tree all branches on the lower stem (the butt log, 0.3–6 m) were assessed for diameter, angle and condition. Trees were sampled in plots grown at four initial planting densities: 838 (3 m x 4 m), 1111 (3 m x 3 m), 1667 (3 x 2 m) and 3333 (3 m x 1 m) trees ha-1. The butt log of both species contained 55–70 branches, regardless of the initial density. Initial density did not affect branch formation, but it did affect the subsequent growth and persistence of branches. Lower initial density increased both the mean branch diameter and the number of large branches (> 2.5 cm diameter) per tree in both species. Branch size also increased with height up the stem, but the rate of increase was not different between densities. A major difference between species was that E. pilularis had more small dead branches that had not been shed. A single spacing prescription is possible for both species because there was no difference between species in the relationship between large branches and density.