Chris Harwood

Acacia plantations in Vietnam: research and knowledge application to secure a sustainable future

Vietnam has established 1.1 million ha of acacia plantations for wood production, managed on 5- to 10-year rotation cycles. Nearly 50% of the resource is managed by small growers holding 1–5 ha woodlots. Acacia plantations have emerged as an important resource for supporting the rural economy and national export revenue. Given the range of climate, terrain, soils, management inputs and skills, plantation productivity varies from 10 to 25 m3 ha−1 y−1. Future growth of this sector will depend on improving and sustaining production from the current land base, much of which is already in its second or third rotation. Although studies on sustainable production are limited, available information suggests good prospects for increasing production and improving soils. Breeding has produced genotypes with potential for increasing growth, but this has not generally been matched by sustainable soil and stand management practices. Several current practices warrant immediate change, based on sustainability principles. Internationally, research has established the need for conserving site resources and other judicious management practices. Vietnam should adopt these principles and develop locally appropriate practices to implement them. Greater efforts are required on surveillance of major diseases and tree breeding to improve disease resistance. Because acacia plantations deliver high economic benefits and there are opportunities for improving productivity, an R&D strategy focused on underpinning sustainable management and application would serve the nation well. Key elements include commitments to adaptive research for achieving impacts, effective partnerships between public and private organisations, fostering an integrated approach to management, and special attention to the needs of smallholder growers.

A multi-site, multi-species near infrared calibration for the prediction of cellulose content in eucalypt woodmeal.

Calibrations between spectra derived from near infrared (NIR) spectroscopy and chemical analyses can be used to predict cellulose content in samples of ground eucalypt woodmeal. Past calibrations have used small sample sets (<100 samples) often representing a single stand or region and only one species, making their application to wider populations of samples problematic. A robust, nondestructive prediction capability for eucalypt wood cellulose that works across stands, regions and species would find many applications in tree breeding and resource assessment. Here, we describe the development and test the performance of a large (> 1000 samples) multi-site and species NIR calibration for predicting cellulose content of eucalypt woodmeal obtained from increment cores, wood chips and stem cross-sections. Most of the samples came from Eucalyptus globulus and E. nitens. The calibration was tested against four independent sample sets and explained between 65% and 84% of the variance in each set. A higher proportion of variance was explained in those sample sets that had a wider range of cellulose content. Standard errors of prediction were between 0.5% and 1.5% cellulose for the four independent sample sets. The test samples were added to the large calibration and a new calibration with 1260 samples was constructed. Principal components analysis suggests additional wood samples with more diverse chemistries are required to enable the calibration to capture more fully the chemical variation present in the genus.

Solid-wood production from temperate eucalypt plantations: a Tasmanian case study

Since 1988, there has been a major focus in Tasmania on research for the management of temperate eucalypt plantations for solid wood. This coincided with the formal transfer of large areas of native forest that had previously been part of the production forest estate into reserves, a decision that triggered the establishment of eucalypt plantations for solid wood. This review summarises research on several key areas: silvicultural requirements for solid-wood production; wood properties of plantation-grown eucalypts and the influence of silviculture and genetics on these properties; factors influencing stem defect and decay; balancing silvicultural requirements with maintenance of tree vigour; and issues concerning wood processing and products. We conclude that there are still operational challenges to be confronted in the production of solid wood from plantations. If these can be overcome in the medium term, temperate plantation eucalypts have the potential to provide wood products that meet the requirements for appearance-grade material and that can compete in the same markets as wood from native forests. The bigger challenge at the national level will be to provide the log volumes of suitable material to meet the anticipated demand 25 to 30 years from now.

Cellulose content as a selection trait in breeding for kraft pulp yield in Eucalyptus urophylla

Abstract• The aim of this study was to investigate the effectiveness of using cellulose content, measured by the diglyme-HCl method, as a selection trait in breeding programs for kraft pulp yield in Eucalyptus urophylla.• A total of 275 trees from sixty-two families were sampled from a thinned progeny trial of E. urophylla in northern Vietnam to evaluate cellulose content from breast-height increment cores. Among those, twenty unrelated trees were felled to evaluate cellulose content and pulp yield from breast-height disk samples.• The regression of pulp yield of disk samples on cellulose content was strong either from disks (R2 = 0.83) or increment cores (R2 = 0.69). There was no significant difference in cellulose content between the provenances. The narrow-sense within-provenance heritability of cellulose content was 0.50 and the coefficient of additive genetic variation was 3.9%. Genetic correlations between cellulose content and growth (0.28–0.45) or wood basic density (−0.02) were not significantly different from zero.• Breast-height increment core cellulose content measured by diglyme-HCl method is under strong genetic control and can be used to rank trees for pulp yield in E. urophylla plantations. Selection for increased cellulose content would have only minor effects on growth and wood basic density.Résumé• L’objectif de cette étude était d’étudier l’efficacité de l’utilisation de la teneur en cellulose, mesuré par la méthode diglyme-HCl, comme un trait de sélection dans les programmes d’amélioration du rendement en pâte kraft chez Eucalyptus urophylla.• Un total de 275 arbres issus de soixante-deux familles ont été échantillonnés, à partir d’un essai de descendance d’ E. urophylla dans le nord du Vietnam, pour évaluer la teneur en cellulose de carottes d’accroissement prélevées à hauteur de poitrine. Parmi ces arbres, vingt ont été abattus afin d’évaluer la teneur cellulose et le rendement en pâte de disques échantillons, prélevées à hauteur de poitrine.• La régression de la production de pâte du disques échantillons a été forte sur la teneur en cellulose, soit à partir des disques (R2 = 0.83) ou des carottes d’accroissement (R2 = 0.69). Il n’y a pas de différence significative pour la teneur en cellulose entre les provenances. Le sens restreint dans l’héritabilité intra-provenance de la teneur de la cellulose était 0,50 et le coefficient de variation génétique additive a été de 3,9 %. Les corrélations génétiques entre la teneur en cellulose et la croissance (0,28–0,45) ou l’infra densité du bois (−0,02) ne sont pas significativement différentes de zéro.• La teneur en cellulose des carottes d’accroissement mesurée par la méthode diglyme-HCl est sous contrôle génétique fort et peut être utilisée pour classer les arbres pour le rendement en pâte dans les plantations d’E. urophylla. La sélection pour l’augmentation de la teneur en cellulose aurait seulement des effets mineurs sur la croissance et l’infra-densité du bois.

Measurement of cellulose content, Kraft pulp yield and basic density in eucalypt woodmeal using multisite and multispecies near infra-red spectroscopic calibrations

Previous descriptions of multisite and multispecies near infra-red (NIR) spectroscopic calibrations for predicting cellulose content (CC) and Kraft pulp yield (KPY) in eucalypt woodmeal demonstrated that large, single calibrations provide precise predictions for a wide range of sites and species. These have since been used in a range of published studies. Their value lies in low-cost, fast analytical throughput and small required sample size. In particular, they allow precise values of KPY to be obtained from small wood samples obtained non-destructively. This study reports the ongoing performance of these calibrations with respect to laboratory chemical values, as well as describing a wood density calibration. Cellulose content was measured in an additional 550 samples taken from over 14 different data sets. The standard error of prediction (SEP) of CC was 0.35% with an average bias of only 0.28%. Adding these samples to the existing calibration gave a sample set of 1 800 samples, producing a calibration with a crossvalidation r2 of 0.87 and standard error of 0.78%. The existing KPY calibration was assessed against an additional 527 samples generating a standard error of prediction of 1.9% and a bias of -1.8%. Adding the samples to the calibration gave a sample set of 1 360 samples producing a calibration with a crossvalidation r2 of 0.87 and standard error of 1.29%. The correlation between NIR-predicted CC and NIR predicted KPY was 85%. A wood density calibration was developed using data generated from wood chips. A total of 1 138 samples were separated randomly into calibration and test sets, representing between 19% and 38% of the sample set. The SEP values were between 34 and 40 kg m−3 and explained between 72% and 84% of the variance. The final calibration including all samples had a crossvalidation r2 of 0.82 and standard error of 29.5 kg m−3.

Performance of Eight Eucalypt Species and Interspecific Hybrid Combinations at Three Sites in Northern New South Wales, Australia

Summary Eight eucalypt taxa, represented by six seedlots and nine clones (two seedlots of Corymbia citriodora subsp. variegata (CCV), one seedlot each of Eucalyptus cloeziana, E. dunnii and E. pilularis, one seedlot and two clones of E. grandis, one clone of E. saligna, three clones of the interspecific hybrid E. grandis × E. camaldulensis and five clones of the hybrid E. urophylla × E. grandis) were tested in taxa trials on three sites in northern New South Wales, Australia. Significant differences between sites and between taxa in survival, growth, stem form and attack by stem-boring insect larvae were demonstrated. All taxa grew best on the Convery site that had the highest mean annual rainfall, 1400 mm, on a Red Ferrosol soil derived from volcanic parent material; E. dunnii and E. pilularis grew to a mean dominant height of 17 m in 6 y, E. cloeziana to 15 m, C. citriodora subsp. variegata and E. saligna to 14 m. Fewer than 2% of trees of all taxa at this site were attacked by insects. The other two sites had Brown Dermosol soils and were drier, the Muller site receiving 1200 mm y−1 and the Ironbolt site 1100 mm y−1. Height and diameter growth of all taxa was slower at these sites, with E. pilularis and E. cloeziana showing the greatest reduction in growth while E. grandis × E. camaldulensis showed the least reduction. Overall survival at age 6 y was acceptable at all three sites, being highest at Convery site (86%) followed by Muller (77%) and Ironbolt (74%). While C. citriodora subsp. variegata and E. cloeziana had minimal damage at Mueller and Ironbolt, the other taxa had from 9% to 100% of stems affected by borers, with E. grandis, the E. saligna clone and E. urophylla × E. grandis proving particularly susceptible on these sites.

Genetic improvement of tropical acacias: achievements and challenges §

Three acacia species, Acacia auriculiformis, A. crassicarpa and A. mangium, dominate over 2 million ha of tropical acacia plantations worldwide. Species and provenance trials carried out in the 1980s and 1990s established the fastest-growing regions of provenance for each species, and most current breeding populations comprise open-pollinated families from several, or many, local provenances sourced from these favoured regions. Provenance–progeny trials are thinned to seedling seed orchards (SSOs), which yield both selected progenies for the next generation of breeding and operational seed for plantations. Clonal forestry has been successfully developed for A. auriculiformis and the hybrid between A. mangium and A. auriculiformis. In many instances production of improved seed in seed orchards has not been adequate to meet planting demand; strategies to address this have been (1) the establishment of additional unpedigreed seed production areas of broad and superior genetic base, and (2) clonal family forestry to multiply elite seed families. Controlled pollination of acacias is technically demanding, so is not suitable for advancing main breeding populations. Substantial (50–100%) gains in wood volume production have been demonstrated in trials comparing seed from first-generation SSOs or selected clones with inferior provenances and land races, but volume gains in subsequent cycles of breeding will be smaller. The potential for genetic improvement in form traits and wood properties has also been demonstrated. Genetic improvement objectives must now give heavy weighting to improving disease resistance and tolerance. Ganoderma root rot and Ceratocystis stem wilt have destroyed large areas of acacia plantations in Indonesia and Malaysia. Since clonal deployment of resistant genotypes is the quickest and most effective way of delivering resistant planting material, ongoing research to develop clonal forestry for A. crassicarpa and A. mangium is warranted. Novel interspecific hybrid combinations might deliver useful genetic variation for breeding.

Clonal variation and genotype by environment interactions in growth and wood density in Eucalyptus camaldulensis at three contrasting sites in Vietnam.

Abstract A total of 172 clones of Eucalyptus camaldulensis were tested in three clonal tests in northern, north-central and southern Vietnam, with 32 of them planted across all three sites. At age 3-5 years, the clonal repeatabilities were 0.18-0.42 for growth traits, 0.71-0.78 for wood basic density and 0.56-0.66 for pilodyn penetration. Genotypic correlations between growth and density at the three sites were from -0.24 to 0.17, and did not differ significantly from zero. Genotypic correlations between sites were 0.32-0.56 for growth traits at age 3 years, and 0.72-0.88 for density and pilodyn penetration. Selection gains for breast height diameter at individual sites at a selection proportion of 5% were 22-32%, with minor effects on density. Selection for diameter at one site gave indirect responses in diameter at the other two sites that were only 40-60% of the gains obtainable from direct selection at those sites. This study shows that fast-growing E. camaldulensis clones can be selected in Vietnam with only minor effects on density. Selection for growth should be regionally based to maximize selection gain whereas clonal rankings for density will change little across regions.

Wood properties of Eucalyptus globulus at three sites in Western Australia: effects of fertiliser and plantation stocking

Summary 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.

Wood stiffness and strength as selection traits for sawn timber in Acacia auriculiformis

Acacia auriculiformis A. Cunn. ex Benth. is an important planting tree species, but little attention has been paid to its wood properties, such as shrinkage, stiffness, strength, and basic density, which are important for use in structural and appearance-grade timber applications. Here we report the genetic variation in static bending stiffness and strength of wood in a 5½-year-old clone trial in southern Vietnam and the genotypic correlations among these traits and tree diameter, wood shrinkage, and basic density. There was significant variation in stiffness and strength among 40 randomly selected clones. Clonal repeatability (H2) was high for stiffness and moderate for strength. There was no consistent pattern of difference between heartwood and sapwood for the estimates of H2 for stiffness and strength, whereas the estimates of H2 were lower for heartwood density than for sapwood density. Diameter showed a significant negative genotypic correlation with stiffness but a nonsignificant correlation with s...