Tracheid Properties Research Articles

A comparative study of the tracheid and crystalline properties of Dahurian larch (Larix gmelinii) and Japanese larch (Larix kaempferi) wood

The tracheid and crystalline properties of earlywood and latewood within the stems of Korean-grown Dahurian and Japanese larches were studied to obtain valuable information for identifying these two species and determining their wood quality. The tracheid length and width were examined via optical microscopy, and the relative crystallinity and crystallite widths were examined using the X-ray diffraction method. The tracheid length and width were greater in the Dahurian larch compared to the Japanese larch. In both wood species, the tracheid length and width increased as the growth ring number increased but stabilized at a certain growth ring number. The relative crystallinity was higher in the Japanese larch wood compared to the Dahurian larch wood, while the crystallite width in both species was similar. Neither the relative crystallinity nor the crystallite width displayed a constant trend from pith to bark. The differences in the tracheid properties and the relative crystallinity of both species could be used to identify them and evaluate their wood quality for their effective utilization.

Tracheid dimensions of Norway spruce in uneven-aged stands

Tracheid length and width patterns from pith to bark at a height of 0.6 m in uneven-aged Norway spruce (Picea abies (L.) Karst.) trees were studied. Identification of the main factors and a comparison with even-aged stands were also carried out. Ninety-six trees were sampled from experimental stands in southern Finland. The material encompassed the variation in tracheid properties from early years to silvicultural maturity, i.e., from corewood to outerwood up to a cambial age of 111 years. Data from 39 Norway spruce trees from even-aged stands were utilized for comparison. Models fitted to the data indicated that annual ring widths did not influence mean tracheid dimensions but that the latewood proportion had a significant influence on tracheid dimensions. Tracheids in uneven-aged stands were slightly wider and longer at the base of the stem in trees with a similar diameter, cambial age, and annual ring number.

Mapping variation of handsheet properties within loblolly pine trees

Abstract Within-tree variation of four handsheet properties (burst index, sheet density, STFI short-span compression strength (STFI) and tensile index) was mapped for loblolly pine trees aged 13 and 22 years using NIR predicted handsheet property data (representing an average of 18 trees for each age). All within-tree maps were similar demonstrating a radial decrease in handsheet properties at all heights, with sheet density and tensile index having the greatest within-tree variation. The corewood zone had the highest values for all properties, while the lowest values were observed in a region consistent with juvenile and transitional outerwood as defined by Burdon et al. (2004). The maps are also similar to, but the inverse of, maps reported in prior studies for density and tracheid coarseness and wall thickness. Relationships amongst the examined handsheet properties and wood and tracheid properties explains the overall similarities of the different maps. The maps provide a representation of within-tree variation of important paper properties at two different ages. An understanding of how these properties vary within loblolly pine trees can aid in better utilization of forest resources.

Frozen in the dark: interplay of night-time activity of xanthophyll cycle, xylem attributes, and desiccation tolerance in fern resistance to winter.

While most ferns avoid freezing as they have a tropical distribution or shed their fronds, wintergreen species in temperate and boreoalpine ecosystems have to deal with sub-zero temperatures. Increasing evidence has revealed overlapping mechanisms of desiccation and freezing tolerance in angiosperms, but the physiological mechanisms behind freezing tolerance in ferns are far from clear. We evaluated photochemical and hydraulic parameters in five wintergreen fern species differing in their ability to tolerate desiccation. We assessed frond freezing tolerance, ice nucleation temperature and propagation pattern, and xylem anatomical traits. Dynamics of photochemical performance and xanthophyll cycle were evaluated during freeze-thaw events under controlled conditions and, in selected species, in the field. Only desiccation-tolerant species, which possessed a greater fraction of narrow tracheids (<18 μm) than sensitive species, tolerated freezing. Frond freezing occurred in the field at -3.4 ± 0.9 °C (SD) irrespective of freezing tolerance, freezable water content, or tracheid properties. Even in complete darkness, maximal photochemical efficiency of photosystem II was down-regulated concomitantly with zeaxanthin accumulation in response to freezing. This was reversible upon re-warming only in tolerant species. Our results suggest that adaptation for freezing tolerance is associated with desiccation tolerance through complementary xylem properties (which may prevent risk of irreversible cavitation) and effective photoprotection mechanisms. The latter includes de-epoxidation of xanthophylls in darkness, a process evidenced for the first time directly in the field.

Genetic control of tracheid properties in Norway spruce wood

Through the use of genome-wide association studies (GWAS) mapping it is possible to establish the genetic basis of phenotypic trait variation. Our GWAS study presents the first such effort in Norway spruce (Picea abies (L). Karst.) for the traits related to wood tracheid characteristics. The study employed an exome capture genotyping approach that generated 178 101 Single Nucleotide Polymorphisms (SNPs) from 40 018 probes within a population of 517 Norway spruce mother trees. We applied a least absolute shrinkage and selection operator (LASSO) based association mapping method using a functional multi-locus mapping approach, with a stability selection probability method as the hypothesis testing approach to determine significant Quantitative Trait Loci (QTLs). The analysis has provided 30 significant associations, the majority of which show specific expression in wood-forming tissues or high ubiquitous expression, potentially controlling tracheids dimensions, their cell wall thickness and microfibril angle. Among the most promising candidates based on our results and prior information for other species are: Picea abies BIG GRAIN 2 (PabBG2) with a predicted function in auxin transport and sensitivity, and MA_373300g0010 encoding a protein similar to wall-associated receptor kinases, which were both associated with cell wall thickness. The results demonstrate feasibility of GWAS to identify novel candidate genes controlling industrially-relevant tracheid traits in Norway spruce.

Models for predicting the within-tree and regional variation of tracheid length and width for plantation loblolly pine

AbstractLoblolly pine is a major fibre source for the pulp and paper industry. Here we developed the first nonlinear models to predict the within-tree and regional variation of tracheid length and width for planted loblolly pine. Data were obtained from macerated tracheids and near-infrared spectroscopy calibration models from trees sampled in 109 stands across the southeastern United States. The fixed effects for the final tracheid length model, which included cambial age, height of disk within tree, and physiographic region, explained 71 percent of the variation with root mean square error (RMSE) of 0.28 mm, while the fixed effects for the final tracheid width model explained 57 percent of the variation with RMSE of 1.4 μm. There was significant variation in tracheid properties across the growing regions. Tree maps showing within-tree variability in tracheid properties were produced. Five simulated scenarios were compared using the models developed, with mean tracheid dimensions calculated on a whole-tree basis at a first and second thinnings, and at final harvest. Also from the final harvest, the tops of trees, and outerwood chips produced during lumber manufacturing were also simulated. For the whole tree scenarios, both mean tracheid length and width increased with age, increasing from 2.24 mm and 40.5 μm (age 12), to 2.51 mm and 41.3 μm (age 18), and to 2.73 and 41.8 μm at age 25, respectively. The tops of the trees at age 25 had a mean tracheid length of 2.46 mm and a mean width of 41.0 μm, while the chips had a mean tracheid length of 3.13 mm and a mean width of 42.5 μm. Due to the models representing samples collected from across the southeastern United States, and their relatively high precision, they are suitable for incorporation into growth and yield systems allowing for prediction of tracheid properties.

Whole-tree tracheid property maps for loblolly pine at different ages

Maps developed using Akima’s interpolation method, and representing average data for trees aged 13 and 22 years, were used to compare patterns of within-tree variation for Pinus taeda L. (loblolly pine) tracheid properties: coarseness (C), specific surface (S), radial (R) and tangential (T) diameter and wall thickness (w). SilviScan-calibrated near-infrared (NIR) spectroscopy provided data for the analysis with C (Rc2 = 0.85, Rp2 = 0.85), S (Rc2 = 0.83, Rp2 = 0.76), and w (Rc2 = 0.89, Rp2 = 0.93) models having very good calibration / prediction statistics, while those for T and R diameter were moderate (Rc2 = 0.79, Rp2 = 0.57) and poor (Rc2 = 0.64, Rp2 = 0.19), respectively. C, S, and w maps were similar to the density maps for P. taeda and indicate the properties increase radially at all heights. The T diameter map was similar to maps reported for microfibril angle except that T diameter increased radially and with height whereas microfibril angle decreased radially and with height. The map for R diameter increased with height and was unlike the other properties examined; caution is recommended regarding any interpretations based on the R diameter map owing to the weak statistics observed for the NIR model. Changes observed between the two ages are consistent with the asymptotic progression of properties associated with maturation.

Genetic control of tracheid properties in Norway spruce wood

Genetic control of tracheid properties in Norway spruce wood

A new approach for modelling water transport in fossil plants

ABSTRACTThe origin of xylem in the Silurian was a major step in plant evolution, leading to diverse growth forms with various mechanical and hydraulic properties. In the fossil record, these properties can only be investigated using models based on extant plant physiology. Regarding hydraulics, previous studies have considered either the properties of a single tracheid or of a set of independent tubes. Here, we use the analogy between the flow of water under tension in a plant and an electrical circuit to develop an extension of Wilson’s single tracheid model to the tissue scale. Upscaling to the tissue-level allows considering wood as a heterogeneous tissue by taking into account differences in tracheid density and the presence of rays. The new model provides a more biologically accurate representation of fossil wood hydraulic properties. The single tracheid and new tissue models are applied to two conspecific specimens of Callixylon (Progymnospermopsida, Archeopteridales) from the Late Devonian of Morocco. Differences are shown at the tissue level that cannot be suspected at the single tracheid level. Callixylon represents the first trees with a conifer-like wood and is a major component of Late Devonian floras world-wide. Our results show that the anatomical disparity of its wood might have led to hydraulic plasticity, allowing growth in various environmental conditions. More generally, the new tissue-model suggests that the various combinations of tracheid and ray sizes present in Palaeozoic plants might have led to a higher variety of ecophysiologies than suspected based solely on the properties of individual tracheids.

Regional calibration models for predicting loblolly pine tracheid properties using near-infrared spectroscopy

This study developed regional calibration models for the prediction of loblolly pine (Pinus taeda) tracheid properties using near-infrared (NIR) spectroscopy. A total of 1842 pith-to-bark radial strips, aged 19–31 years, were acquired from 268 trees from 109 stands across the southeastern USA. Diffuse reflectance NIR spectra were collected at 10-mm increments from the radial face of pith-to-bark strips using a FOSS 5000 scanning spectrometer. A subset of the 10-mm samples was selected based on the NIR spectra uniqueness and placed in calibration (N = 1020) and validation (N = 998) test sets. The samples were macerated and the tracheid properties measured using an optical analyzer (Techpap MorFi Fiber and Shive Analyzer). Models were created using partial least squares (PLS) regression using the calibration samples, and their performance checked using the validation set. Prediction PLS models for tracheid length were strong when checked with the validation set [R p 2 = 0.87, standard error of prediction (SEP) = 0.23 mm, ratio of performance to deviation (RPD) = 2.8]. Prediction models for tracheid width had moderate fit statistics (R2 = 0.61, SEP = 1.6 μm, RPD = 1.6), but the SEP was similar to the measurement error of the camera (± 2 μm). The NIR wavelengths of importance were largely attributed to cellulose. The 1542 nm wavelength explained 77% of the variation in tracheid length (RMSE = 0.31 mm). These results demonstrate that NIR spectroscopy models for tracheid length and width can be developed from a diverse set of samples and still maintain prediction accuracy.

Effect of thinning on wood density and tracheid properties of Scots pine on drained peatland stands

The properties of wood and wood tracheids from trees growing in peatland stands are still insufficiently known. The long-term effects of thinning on wood and tracheid properties of Scots pine (Pinus sylvestris L.) were investigated in two thinning experiments on peatland sites in central Finland. The two sites were ditched for the first time in 1958 and 1973, and thinning experiments were established in 1987 and 1993, respectively. Thinning increased the basal area increment of the remaining trees by 20 per cent. No differences between the trees that were growing on the thinned plots and those that were growing on the unthinned control plots were found in the latewood proportion, wood density, tracheid diameter, cell wall thickness and tracheid length. Moreover, the wood and tracheid properties did not differ markedly from those of corresponding material originating from mineral soil sites. The results confirm the previous results on mineral soils, which showed that an increasing availability of resources primarily increases the rate of tracheid production but has no major effects on wood and tracheid properties.

Wood density and tracheid properties of Scots pine: responses to repeated fertilization and timing of the first commercial thinning

The aim of this study was to compare the effects of fertilization and thinning on the growth rate and wood and tracheid properties of Scots pine (Pinus sylvestris L.) in southern Finland. The study was based on two long-term experiments with two fertilization treatments (unfertilized and 150 kg N ha−1 every 5 years) and two thinning levels (delayed and intensive first commercial thinning) in a randomized block design. A total of 80 trees were sampled ∼30 years after the onset of the treatments. Intensive thinning enhanced the radial growth of the remaining trees by 52 per cent compared with the delayed first thinning. Accordingly, the fertilization increased the radial growth by 37 per cent compared with the unfertilized trees. However, only small differences were found between the treatments in the earlywood/latewood ratio (3–9 per cent), wood density (2–8 per cent), tracheid diameter (2–5 per cent), cell wall thickness (0–10 per cent) and tracheid length (4–5 per cent). The results demonstrated that the prevailing fertilization and thinning treatments of Scots pine stands considerably enhance the growth rate but do not cause major detrimental changes in the wood and tracheid properties.

Xylogenesis of Pinus pinaster under a Mediterranean climate

Context The knowledge on cambial activity in water-limited environments, such as the Mediterranean, is still fragmentary. Dendrochronological studies have determined that spring precipitation plays an important part in determining tree-ring width and the properties of tracheids. However, the complex relation between cambial phenology and climate is still far from understood.

Predicting wood and tracheid properties of Scots pine

Models were developed for predicting the proportion of latewood, wood density, tracheid length, tracheid width, and the ratio of cell wall thickness to tracheid width in individual annual rings of Scots pine (Pinus sylvestris L.). The models needed to be applicable as a part of a stand growth simulation system, which is based on growth models at the tree level. Data were collected from long-term thinning, thinning-fertilisation, and precommercial thinning experiments on mineral soil and drained peatland in southern and central Finland. The wood and tracheid properties were related to radial increment rate and distance from the pith outwards. An increased increment rate, caused by the different treatments and environmental conditions, resulted in similar types of changes in the wood and tracheid properties irrespective of the factors promoting radial increment. Although most of the average values of the properties were predicted unbiased, there were large random variations between individual trees and annual rings. The fixed parts of the models accounted for the following percentages of the variation: latewood proportion, 42%, wood density, 35%, tracheid length, 84%, tracheid width, 44%, and cell wall percentage, 29%. Incorporating the models for wood and tracheid properties into forest management planning systems enables estimates for the conversion of different silvicultural regimes into internal stem structure and wood quality.

Effects of timing and intensity of thinning on wood structure and chemistry in Norway spruce

AbstractThe effects of thinning intensity on wood structure and chemistry of Norway spruce [Picea abies(L.) Karst.] have been studied in a long-term thinning experiment established in the 1960s in south-western Sweden. The experiment comprised datasets of unthinned control trees and trees of four thinning treatments, in which thinning operations of different intensities were carried out. These thinning operations were applied either once, three, or five times over the course of the stand rotation. Thinning intensities varied from 0% to 60% based on the stand basal area (BA) before thinning: (A) 5×20% (i.e., 20% of the BA removed five times); (B) 3×40% (i.e., 40% of the BA removed three times); (C) 1×60% (i.e., 60% of the BA removed once); and (D) 5×40% (i.e., 40% of the BA removed five times). Altogether 60 trees that were 67 years old were sampled 38 years after the treatment onset. Radial growth rate, wood density, tracheid properties, and the chemical composition of wood were studied in detail. All four thinning treatments increased growth rate and decreased wood density; however, treatment D showed the greatest change. Single, heavy thinning in treatment C resulted in unfavourable intra-stem variation in ring width and wood density. No significant differences in tracheid properties and wood chemistry were found between the treatments. We conclude that only a remarkable increase in growth rate would induce detrimental changes in tracheid properties and wood chemistry in the context of thinning.

The effect of artificially induced drought on radial increment and wood properties of Norway spruce

We studied experimentally the effects of water availability on height and radial increment as well as wood density and tracheid properties of Norway spruce (Picea abies (L.) Karst.). The study was carried out in two long-term N-fertilization experiments in Southern Finland (Heinola and Sahalahti). At each site, one fertilized and one control plot was covered with an under-canopy roof preventing rainwater from reaching the soil. Two uncovered plots were monitored at each site. The drought treatment was initiated in the beginning of growing season and lasted for 60-75 days each year. The treatment was repeated for four to five consecutive years depending on the site. Altogether, 40 sample trees were harvested and discs sampled at breast height. From the discs, ring width and wood density were measured by X-ray densitometry. Tracheid properties were analysed by reflected-light microscopy and image analysis. Reduced soil water potential during the growing season decreased annual radial and height increment and had a small influence on tracheid properties and wood density. No statistically significant differences were found in the average tracheid diameter between the drought-treated and control trees. The average cell wall thickness was somewhat higher (7-10%) for the drought treatment than for the control, but the difference was statistically significant only in Sahalahti. An increased cell wall thickness was found in both early- and latewood tracheids, but the increase was much greater in latewood. In drought-treated trees, cell wall proportion within an annual ring increased, consequently increasing wood density. No interaction between the N fertilization and drought treatment was found in wood density. After the termination of the drought treatment, trees rapidly recovered from the drought stress. According to our results, severe drought due to the predicted climate change may reduce Norway spruce growth but is unlikely to result in large changes in wood properties.

Tracheid cross-sectional dimensions in Scots pine (Pinus sylvestris) – distributions and comparison with Norway spruce (Picea abies)

Cell wall thickness and tracheid radial and tangential diameter are important characteristics in papermaking. These fibre cross-sectional dimensions affect paper properties such as light scattering, and tear and tensile indexes. In the authors’ previous article, the mean values and distributions of tracheid cross-sectional dimensions were obtained for Norway spruce (Picea abies). This article characterises the cross-sectional tracheid properties of Scots pine (Pinus sylvestris) using exactly the same methodology as in the previous study on Norway spruce, which enables the comparison between the tree species. The distributions for Scots pine cell wall thickness and tracheid radial diameter were similar: a narrow peak due to earlywood tracheids, and a wide peak due to latewood tracheids. The tangential diameter distributions for Scots pine were very similar in both earlywood and latewood, having one wide peak. Also, the distributions in whole stem, top pulpwood and sawmill chip assortments were quite similar. The differences between Scots pine and Norway spruce tracheid cross-sectional dimensions were fairly marginal. This is at least the case when comparing large tracheid populations, in which differences tend to even out. The situation may be different on a more detailed level of observation, for example, when individual annual rings in the different tree species are compared.

Effects of thinning and fertilization on wood properties and economic returns for Norway spruce

The effects of silviculture on wood and tracheid properties, and economic returns of Norway spruce ( Picea abies (L.) Karst.) were investigated in two case studies, one comparing different thinning intensity in southeastern Finland and the other considering the effects of optimal nutrient addition in northern Sweden. Models for predicting the wood and tracheid properties of Norway spruce were integrated into a distance-independent process-based growth and yield model. Increasing the thinning intensity resulted in a lower mean wood density, tracheid length, and latewood proportion in harvested wood. Wood density and tracheid length of harvested pulpwood slightly decreased in later thinnings and final cuts. Thinning regimes with high early growing stock and decreasing later growing stock were most profitable. Nutrient addition accelerated volume growth and increased the value growth. The increase in volume growth due to nutrient addition more than offset the economic influence of the loss in wood density and tracheid length.

Microfibril Angle: Measurement, Variation and Relationships – A Review

Microfibril angle (MFA) is perhaps the easiest ultrastructural variable to measure for wood cell walls, and certainly the only such variable that has been measured on a large scale. Because cellulose is crystalline, the MFA of the S2 layer can be measured by X-ray diffraction. Automated X-ray scanning devices such as SilviScan have produced large datasets for a range of timber species using increment core samples. In conifers, microfibril angles are large in the juvenile wood and small in the mature wood. MFA is larger at the base of the tree for a given ring number from the pith, and decreases with height, increasing slightly at the top tree. In hardwoods, similar patterns occur, but with much less variation and much smaller microfibril angles in juvenile wood. MFA has significant heritability, but is also influenced by environmental factors as shown by its increased values in compression wood, decreased values in tension wood and, often, increased values following nutrient or water supplementation. Adjacent individual tracheids can show moderate differences in MFA that may be related to tracheid length, but not to lumen diameter or cell wall thickness. While there has been strong interest in the MFA of the S2 layer, which dominates the axial stiffness properties of tracheids and fibres, there has been little attention given to the microfibril angles of S1 and S3 layers, which may influence collapse resistance and other lateral properties. Such investigations have been limited by the much greater difficulty of measuring angles for these wall layers. MFA, in combination with basic density, shows a strong relationship to longitudinal modulus of elasticity, and to longitudinal shrinkage, which are the main reasons for interest in this cell wall property in conifers. In hardwoods, MFA is of more interest in relation to growth stress and shrinkage behaviour.

The effects of thinning and fertilisation on wood and tracheid properties of Norway spruce (Picea abies) – the results of long-term experiments

Dissertation. University of Helsinki, Faculty of Agriculture and Forestry, Department of Forest Resource Management. 2008