Geoffrey M. Downes

Daily stem growth patterns in irrigated Eucalyptus globulus and E. nitens in relation to climate

Abstract Daily increments in stem radius were determined from hourly dendrometer measurements in each of three irrigated Eucalyptus nitens and E. globulus trees. Multiple regressions determined from daily weather variables accounted for 40–50% of the variance in increment. The use of weather variables lagged by 1–2 days increased the variance explained. The diurnal variation in stem radius was resolved into three mathematically defined phases: shrinkage, recovery and increment. The positive daily net increment in stem radius, by definition, occurred in the increment phase. Average weather conditions during this phase (predominantly night-time) did not explain any more variance in increment than the average daily conditions, determined over a 24 h period. Daily increment was resolved into a rate of stem radius increase during the increment phase and the duration (hours) of that phase. Significant species by month interactions were evident with growth in summer characterised by faster rates of stem expansion over shorter time periods within each diurnal cycle. E. nitens tended to have longer increment phases in spring and autumn, and faster phase rates in autumn than E. globulus. Interactions between weather variables and cambial growth were complicated and varied over the year. The correlation between temperature and stem growth varied from positive in spring to zero or negative during summer. The data indicate a need to understand weather-by- climate interactions at the level of whole tree physiology in order to fully understand the effect of weather on cambial activity and therefore stem increment and wood properties.

RELATIONSHIP BETWEEN WOOD DENSITY, MICROFIBRIL ANGLE AND STIFFNESS IN THINNED AND FERTILIZED PINUS RADIATA

The relationships between wood anatomy in standing trees and the strength of boards were examined in Pinus radiata D. Don (thinned vs thinned and fertilized) at 2 contrasting sites. Fertilizer treatments were applied after mid-rotation thinning. Logs were taper sawn and boards, near the pre-treatment / post-treatment boundary, subjected to acoustic and strength assessment. Average wood property data from a 12-mm increment core obtained prior to harvest, was extracted from the relevant portion of the radius.In general, fertilizer resulted in lower density, higher microfibril angle (MFA) and slightly lower stiffness. However, stiffness was still relatively high as the affected wood was from the more mature portion of the radius. SilviScan density and MFA data were good predictors of stiffness. Acoustic measurements on boards were strongly correlated with board stiffness. Path analyses explained up to 45% of the variance in stiffness, as a function of estimated MOE and log sweep.

Direct Effects of Wood Characteristics on Pulp and Handsheet Properties of Eucalyptus globulus

Summary Fibre length, microfibril angle and wood density were measured in eight-year-old Eucalyptus globulus clones planted on three different sites. Samples were chipped and pulped, and the pulps beaten prior to preparation of 60g/m2 handsheets. Eleven physical handsheet properties, together with pulp freeness, were measured using standard methods. Direct relationships between wood properties and pulp/paper properties were studied using path analysis. Fibre length had a strong, direct effect on tear index, bending stiffness, freeness, pulp yield and active alkali consumption. Wood density was a strong predictor of most handsheet properties: high density woods produced bulkier, more porous sheets with higher bending stiffness, while lower density woods produced smoother, denser sheets with higher tensile strength.The effect of microfibril angle was small and more evident in handsheets made from beaten pulp.

Understanding wood formation: gains to commercial forestry through tree-ring research

Summary Tree-ring research, in its varied manifestations, has made many contributions to our understanding of how trees grow and respond to a changing world. Environmental factors can vary from periodic and/or predictable changes in temperature, precipitation and anthropogenic stress factors, to occasional ‘one-off’ events like fire, landslides or storms. The robustness of trees to change is indicated by their longevity. A major advantage of this longevity is that the pattern of response to change is recorded in their wood structure. The variation in wood properties over time is a net result of a complex web of interactions. This pattern of variation is a function of genotype x environment interactions on the whole tree as they impact on the factors controlling cambial growth. A combination of recent advances in measurement technology, cambial development and process modeling offers strong possibilities for making major advances in the understanding of wood formation. This understanding is important to both dendrochronology/dendroecology and commercial forestry. This paper examines some of the recent advances in technology and describes how they have been used to bridge the gap between these two disciplines, addressing areas of interest to both. Changes to the way research is being funded means that greater attention must be paid to the benefits obtained from it. To ensure that research opportunities are captured, there is a need to strengthen links between traditional tree-ring research and research in commercial forestry. Tree-ring research has a major contribution to make to both areas. Understanding the physiology of wood formation will lead to an improvement in the efficiency of our timber production industries and to a better interpretation of the tree-ring record.

Wood properties in a long-lived conifer reveal strong climate signals where ring-width series do not

Although tree-ring-width chronologies have been widely used for temperature reconstructions, there are many sites around the world at which there is little evidence of a clear climate signal in the ring-width chronologies. This is the case with the long-lived conifer Huon pine (Lagarostrobos franklinii (Hook. F.) Quinn), endemic to Tasmania, Australia, when the species grows at low elevation. In this study, we developed chronologies of several wood properties (e.g., tracheid radial diameter, microfibril angle) from Huon pine growing at a low-elevation site. We found that despite the absence of a climate signal in the ring-width chronologies, there were significant correlations between wood density, tracheid radial diameter and microfibril angle and temperature, stream flow and a drought index, enabling the development of robust chronologies. This novel finding suggests that chronologies based on these wood properties may have important potential for climate reconstructions from sites and species that have not yet been realized. In particular, a relatively extensive resource of ancient, low-elevation Huon pine in western Tasmania, in which climate signals have not been found using ring widths, may now be useful as part of the broader effort to reconstruct Southern Hemisphere climate.

TEMPORAL VARIATION OF THE RING WIDTH–WOOD DENSITY RELATIONSHIP IN NORWAY SPRUCE GROWN UNDER TWO LEVELS OF ANTHROPOGENIC DISTURBANCE

The ring width–wood density relationship (RW–WDR) is somewhat controversial. Most of the literature reports negative, but weak relationships, while others found no significant relationships at all. This study analyses the RW–WDR using a dataset of twenty even-aged Norway spruce trees grown at two different levels of air pollution in the Eastern Ore Mountains, Germany. Ring width, latewood proportion and wood density were measured in each tree ring. The year-to-year (temporal) variability of the RW–WDR was calculated by sequentially taking the rings grown in the same calendar year in trees within a site. In addition, RW–WDR was also calculated across tree rings (pith to bark) of given trees. During the observed period, the temporal RW–WDR fluctuated between negative and positive correlations with certain climatic patterns, as well as forest operations, playing a prominent role. It was shown that increased late-season rainfall favoured a more positive relationship. The temporal RW–WDR illustrated, for given trees of a site, that smaller rings formed in certain years might be related to higher wood density while other years may result to lower wood density. This finding is useful for an improved understanding regarding the effect of ring width on wood density.

Stability of quantitative trait loci for growth and wood properties across multiple pedigrees and environments in Eucalyptus globulus

· Eucalypts are one of the most planted tree genera worldwide, and there is increasing interest in marker-assisted selection for tree improvement. Implementation of marker-assisted selection requires a knowledge of the stability of quantitative trait loci (QTLs). This study aims to investigate the stability of QTLs for wood properties and growth across contrasting sites and multiple pedigrees of Eucalyptus globulus. · Saturated linkage maps were constructed using 663 genotypes from four separate families, grown at three widely separated sites, and were employed to construct a consensus map. This map was used for QTL analysis of growth, wood density and wood chemical traits, including pulp yield. · Ninety-eight QTLs were identified across families and sites: 87 for wood properties and 11 for growth. These QTLs mapped to 38 discrete regions, some of which co-located with candidate genes. Although 16% of QTLs were verified across different families, 24% of wood property QTLs and 38% of growth QTLs exhibited significant genotype-by-environment interaction. · This study provides the most detailed assessment of the effect of environment and pedigree on QTL detection in the genus. Despite markedly different environments and pedigrees, many QTLs were stable, providing promising targets for the application of marker-assisted selection.

Developing and evaluating a multisite and multispecies NIR calibration for the prediction of Kraft pulp yield in eucalypts

Over recent years the application of near infra-red (NIR) spectroscopy to the prediction of wood properties has been demonstrated in many proof-of-concept studies. Previous work has demonstrated that NIR measurements can be used to predict basic density from woodmeal, chainsaw dust and solid wood, as well as microfibril angle and modulus of elasticity in solid samples. For over a decade, the prediction of Kraft pulp yield (KPY) has been a constant research focus, and numerous small studies have demonstrated this potential. However, because of the cost of obtaining calibration samples with known KPY, sample numbers are typically less than 100. While the potential for NIR prediction of KPY is well recognised, the shift to routine commercial use has not occurred. There still remains considerable scepticism in the research and industry communities about the use of NIR. Concern is typically expressed in two areas: (1) the consistency, accuracy and precision of predictions and (2) the need to prepare a separate calibration for each site and/or species group. To elevate NIR from proof-of-concept to a pilot scale, a large multisite, multispecies calibration was developed over iterative cycles to: (1) determine whether KPY in eucalypts can be predicted from a single calibration independent of site and species, and (2) identify the potential limits of accuracy and precision. This paper reports the results of the first seven testing cycles. The NIR calibration was expanded from an initial sample set of 104 mixed eucalypt samples to over 720 samples covering more than 40 species from predominantly temperate sites across Australia. The performance of the final calibration using two independent and contrasting data sets showed that a multisite and multispecies calibration is feasible. The expected potential accuracy and precision that can be expected from NIR predictions is discussed.

GROWTH AND WOOD DENSITY RESPONSES TO LATER-AGE FERTILIZER APPLICATION IN PINUS RADIATA

Growth or ring width responses to nitrogen, phosphorus and the two combined fertilizers were significant over five out of seven years that followed treatment (post-treatment period) in thinned, mid-rotation radiata pine (Pinus radiata D. Don). Responses were similar between nitrogen and phosphorus treatments and largest in the nitrogen plus phosphorus (NP) treatment. Fertilizer increased the proportion of wood formed in mid-rotation relative to juvenile wood thereby increasing tree density in comparison to the control. Fertilizers, other than nitrogen, significantly lowered density compared to the control in the posttreatment period only. Density was higher in nitrogen than phosphorus and similar between phosphorus and NP. Density responses lasted for up to 5 years and were inconsistent between treatments. Ring width and density were weakly correlated. Ring width and density responded differently to climatic variables within and between sites, signalling independent physiological controls and highlighting the importance of site specific differences.

High resolution temporal variation in wood properties in irrigated and non-irrigated Eucalyptus globulus.

Abstract• Environmental determinants of wood properties variation were examined in Eucalyptus globulus, a globally important hardwood plantation species, in southern Tasmania, Australia.• Radial variation in wood properties, measured with the SilviScan system, were re-scaled from distance to time abscissa using stem radial growth data measured with dendrometers. With this re-scaled data it was possible to evaluate how water availability and temperature affected wood density, microfibril angle (MFA) and fibre and vessel transverse dimensions in irrigated and non-irrigated trees.• Wood density, fibre radial diameter and MFA were sensitive to water availability. Wood density increased and fibre radial diameter decreased in response to reduced water availability. When high water availability was maintained, wood density was negatively correlated with temperature. Together, temperature and soil matric potential explained about 60% of temporal variation in wood density variation. In contrast MFA was not related to temperature but decreased with increasing water stress. Slower growing trees also had lower MFA than faster growing trees. Slower growing trees had a larger number of vessels per unit area of wood than faster growing trees within this even aged stand. However, vessel radius to the 4th power was significantly higher in faster growing trees than in slower growing trees.• Overall, E. globulus wood properties were sensitive to temporal changes in environmental conditions (particularly water availability) and associated growth rates. The data provided support for the hypothesis that growth rates are hydraulically mediated.Résumé• Nous avons analysé les déterminants environnementaux des variations des propriétés du bois d’Eucalyptus globulus qui est une importante essence feuillue de plantation du sud de la Tasmanie en Australie.• La variation radiale des propriétés du bois — mesurées avec l’outil Silviscan — a été convertie en variation temporelle par le biais des mesures de la croissance radiale obtenues avec des dendromètres. Avec ces données recalibrées il a été possible d’évaluer comment la disponibilité en eau et la température ont affecté la densité du bois, l’angle des microfibrilles ainsi que les dimensions transversale des fibres et vaisseaux pour les arbres irrigués et non irrigués.• La densité du bois, le diamètre radial des fibres et l’angle des microfibrilles sont sensibles à la disponibilité en eau. En réponse à une réduction de la disponibilité en eau on observe que la densité du bois augmente et le diamètre radial des fibres diminue. Lorsqu’un niveau élevé de disponibilité en eau est maintenu alors la densité du bois apparaît négativement corrélée avec la température. La température et le potentiel matriciel du sol expliquent ensemble environ 60 % de la variation temporelle de la densité du bois. À l’inverse l’angle des microfibrilles n’est pas relié à la température mais il décroît lorsque le stress hydrique augmente. Les arbres à croissance lente ont également un angle des microfibrilles plus faible que les arbres à croissance rapide. Au sein des peuplements équiennes, les arbres à croissance lente on un plus grand nombre de vaisseaux par unité de surface du bois que les arbres à croissance plus rapide. Cependant la puissance quatrième du rayon des vaisseaux est significativement plus élevée pour les arbres à croissance rapide que pour les arbres à croissance lente.• Dans l’ensemble les propriétés du bois d’ E. globulus sont sensibles aux variations temporelles des conditions environnementales (en particulier la disponibilité en eau) et sont associées aux taux de croissance. Les données fournies confirment l’hypothèse que les taux de croissance sont régulés hydrauliquement.