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L.R. Schimleck, E. Sussenbach, G. Leaf, P.D. Jones and C.L. Huang

The use of calibrated near infrared (NIR) spectroscopy for predicting the microfibril angle (MFA) of Pinus taeda L. (loblolly pine) wood samples is described. NIR spectra were collected from the tangential face of earlywood (EW) and latewood (LW) sections cut from eleven P. taeda radial strips. The MFA of these sections was measured using X-ray diffraction. Calibrations for MFA were determined using all samples combined, EW only and LW only. Relationships were good, with coefficients of determination (R2) ranging from 0.86 (EW) to 0.91 (LW). A calibration for MFA based on NIR spectra collected from sections of 8 strips was used to predict the MFA of sections from the remaining 3 strips. Prediction statistics were strong (R2 p = 0.81, SEP= 5.2 degrees, RPDp = 2.23) however errors were greater than those reported previously for studies based on NIR spectra collected from the radial-longitudinal face. The results presented in this study demonstrate that it is possible to use tangential face NIR spectra to determine MFA variation for EW and LW within individual growth rings.

Martina Lazzarin, Alan Crivellaro, Cameron B. Williams, Todd E. Dawson, Giacomo Mozzi and Tommaso Anfodillo

Across land plants there is a general pattern of xylem conduit diameters widening towards the stem base thus reducing the accumulation of hydraulic resistance as plants grow taller.

In conifers, xylem conduits consist of cells with closed end-walls and water must flow through bordered pits imbedded in the side walls. As a consequence both cell size, which determines the numbers of walls that the conductive stream of water must cross, as well as the characteristics of the pits themselves, crucially affect total hydraulic resistance. Because both conduit size and pit features influence hydraulic resistance in tandem, we hypothesized that features of both should vary predictably with one another. To test this prediction we sampled a single tall (94.8 m) Sequoiadendron giganteum tree (giant sequoia), collecting wood samples from the most recent annual ring progressively downwards from the tree top to the base. We measured tracheid diameter and length, number of pits per tracheid, and the areas of pit apertures, tori, and margos. Tracheid diameter widened from treetop to base following a power law with an exponent (tracheid diameterstem length slope) of approximately 0.20. A similar scaling exponent was found between tracheid length and distance from tree top. Additionally, pit aperture, torus, and margo areas all increased (again with a power of ~0.20) with distance from tree top, paralleling the observed variation in tracheid diameter and length. Pit density scaled isometrically with tracheid length. Within individual tracheids, total permeable area of pits, measured as the sum of the margo areas, scaled isometrically with lumen area. Given that pores of the margo membrane are believed to increase in parallel with membrane area, from a strictly anatomical perspective, our results support the interpretation that pit resistance remains a relatively constant fraction of total resistance along the hydraulic pathway.

Cyriac S. Mvolo, Ahmed Koubaa, Maurice Defo, Jean Beaulieu, Martin-Claude Yemele and Alain Cloutier

The establishment of patterns of radial and longitudinal variations and the development of models to predict the wood anatomical properties, especially from juvenile wood, are of interest for both wood industry and researchers. Linear regressions were used to predict whole-tree, breast height and mature tracheid length and diameter in white spruce (Picea glauca (Moench) Voss) and the WBE model was used to predict the variation of tracheid diameter. Tracheid length and diameter increased from pith to bark. Tracheid length decreased, while tracheid diameter increased from apex to lower heights. Cambial age was the most important predictor of tracheid length. The final tracheid length models with either a log transformation or a third-order polynomial of cambial age explained 82% of the variation in the whole-tree tracheid length. At breast height, 83% of the variation in the whole tracheid length was explained using the juvenile value at a cambial age of 3 years. Up to 87% of the variation was explained by the model, including the average value of juvenile wood. However, mature wood tracheid length at breast height could not be predicted from juvenile wood. Distance from the apex predicted the tracheid widening in outer rings but failed to predict tracheid expansion of samples collected at fixed cambial ages. The WBE explained 86% of conduit widening in the outer rings. The sampling strategy, i.e. collecting samples longitudinally at a fixed cambial age vs. at a fixed calendar year is important in predicting tracheid diameter.

D.V. Igartúa, S.E. Monteoliva, M.G. Monterubbianesi and M.S. Villegas

The aim of the present work was to analyze the associations between basic density and fibre length at breast height (BH) and of the whole tree. This study focused on the need to find a sampling point representative for the whole tree, using 35-year-old Eucalyptus globulus ssp. globulus plantations established under two different growing conditions in the province of Buenos Aires, Argentina.

The relationship between whole-tree and BH values was quantified using linear regression analysis. Relationships were obtained for each growing site and wood features.

Maomao Zhang, Guang Jie Zhao, Bo Liu, Tuo He, Juan Guo, Xiaomei Jiang and Yafang Yin

prediction accuracy was 100% ( Table 3 ), demonstrating that all the specimens were correctly classified. The variable importance in projection (VIP) was used to reflect the importance of ions in the classification model. VIP coupled with the t-test is a common method for determining the marker ions for the

Larissa C. Dória, Diego S. Podadera, Rivete S. Lima, Frederic Lens and Carmen R. Marcati

Edited by Marcelo R. Pace

prediction of a large dataset testing the relationship between basal and tip vessel diameters and stem length, showing that taller plants ( Tabebuia aurea in our study) have wider conduits at both the base and the tip ( Fig. 3A ; Suppl. Fig. S1 ) ( Olson et al. 2018 ). Since theoretical hydraulic

Laurence R. Schimleck and Robert Evans

Eight Pinus radiata D. Don (Radiata pine) increment core samples representative of a total of thirty-two increment cores were selected for the development of an EL(SS) (longitudinal modulus of elasticity calculated from SilviScan-2 data) calibration based on NIR spectra obtained from the radial–longitudinal face of each sample in 10-mm increments. The primary aim of the work was to investigate if an EL(SS) calibration developed using a subsample of cores representative of a larger set provided better predictions of EL(SS) than those reported in Schimleck et al. (2002a). The EL(SS) calibration was developed using eight factors giving an excellent relationship between SilviScan-2 determined EL(SS) and NIR fitted EL(SS) (coefficient of determination (R2) = 0.97) and a low standard error of calibration (SEC) (0.91 GPa).

To test the EL(SS) calibration, NIR spectra were obtained in 10-mm sections from the radial–longitudinal face of two intact P. radiata increment cores and EL(SS) of each section predicted. NIR estimates of EL(SS) were in excellent agreement with EL(SS) determined using SilviScan-2 data, with R2 of 0.99 (core A) and 0.98 (core B). Standard error of predictions (SEP) of 1.6 GPa (core A) and 1.2 GPa (core B) were obtained. Both sets of predictions closely followed the patterns of EL(SS) radial variation determined experimentally. EL(SS) calibration based on NIR spectra obtained from a set of representative cores can provide excellent predictions of EL(SS). The predictions were superior to those reported in Schimleck et al. (2002a).

Laurence R. Schimleck and Robert Evans

Eight Pinus radiata D. Don (Radiata pine) increment core samples representative of a total of thirty-two increment cores were selected. NIR spectra were obtained from the radial–longitudinal face of each core in 10-mm increments and used to develop a microfibril angle (MFA) calibration. The MFA calibration was developed using seven factors giving an excellent relationship between SilviScan-2 determined MFA and NIR fitted MFA (coefficient of determination (R2) = 0.95) and a standard error of calibration (SEC) of 1.8 degrees.

The MFA calibration was used to predict the MFA of NIR spectra obtained in 10-mm sections from the radial–longitudinal face of two intact P. radiata increment cores. NIR predicted MFA was found to be in excellent agreement with MFA determined by SilviScan-2, with R2 of 0.98 (core A) and 0.96 (core B). The standard error of prediction (SEP) for core A (1.0 degree) was much lower than for core B (2.5 degrees). Both sets of predictions closely followed the patterns of MFA radial variation determined by SilviScan-2. NIR spectroscopy provides a rapid method for determining MFA variation in increment cores and is suitable for the routine analysis of large numbers of samples.

E. Badel, R. Bakour and P. Perré

We coupled a digital X-ray imaging system with a humid air conditioner. This new configuration allows the shrinkage behaviour of thin samples to be measured. In order to control both the temperature and the relative humidity in the chamber, an air generator was developed which ensures very stable conditions even over several months. The X-ray beam passes through the chamber to the 2D detector. Twelve samples can be placed on a rotating sample holder. The strain field due to the moisture content variations is determined by an image correlation algorithm, which compares X-ray images collected at different moisture conditions. Moreover, inspection by X-ray simultaneously produces complementary data: the local density and the spatial organisation of the tissues within the anatomical pattern. Twelve oak samples, chosen for their wide variability of the anatomical pattern, were characterised using this device.

Some models available in the literature are used to predict the swelling. fThe comparison between measurements and prediction is rather poor. The variable anatomical structure of the annual rings permits some explanations for this decrepancy and leads to the conclusion that the complete spatial organisation of the tissues has to be quantified to understand and to predict the behaviour of oak wood.

Frank W. Ewers, John M. Ewers, Anna L. Jacobsen and Jorge López-Portillo

We examined the concept that high vessel number provides xylem safety and also show that under certain circumstances high vessel number may increase rather than decrease the probab ility of mortality. The independent variable was the number of vessels per organ (redundancy). The dependent variable was the probab ility of organ death for which we set three thresho1ds for catastrophic runaway embolism (50, 75 and 90% embolisrn). Results were calculated based upon the probability that any particu1arvesse1would become embolized (P). When the modeled p was below the runaway embolism thresho1d, the safety benefits (decreased probability of organ death) increased dramatically in going from one to ten vessels and approached maximum levels of safety in organs with lOO or more vessels.Vessel redundancy conferred the greatest advantage when p approached, but was less than, the runaway embolism threshold of the organ. However, when p exceeded the runaway embolism threshold the redund ancy relationship was reversed and safety was greatest in organs with lower vessel numbers. Having greater vessel redundancy increased the likelihood of an "average" result, i.e., mortality if p is above the threshold, and survival when p is below the threshold. Model predictions are discussed in terms of redundancy segmentation, stern splitting and various other ecological and evolutionary strategies for plants exposed to different environmental conditions.