Knowledge of wood property variation within trees is critical for understanding age effects on wood formation and for improved utilization of forests, and maps provide an effective way to efficiently summarize and visually represent variability. Despite the importance of maps, examples for North American conifers are rare. Most studies focus on plantation grown trees, with the majority examining loblolly and radiata pine. For these species almost all maps can be categorized into two groups related to tracheid differentiation processes. One group includes properties related to secondary cell wall formation, e.g., density, and the second relates to tracheid enlargement, e.g., tracheid length. Maps for trees from natural forests are largely limited to density and are highly variable indicating site effects are large. The degree of variation within a species made it impossible to develop conclusions regarding general patterns of variation as with plantation grown trees. The identified density maps are consistent with the three radial variation patterns defined by Panshin and de Zeeuw (1980) (Type 1 (increase), 2 (decrease then increase), and 3 (decrease)). A focused research effort to better visualize wood property variation is required, particularly for species demonstrating Type 2 and 3 radial density patterns.

Hevea brasiliensis (rubber tree), a major source of natural rubber, could also be an important source of lumber as senescence occurs. However, latex collection is known to affect Hevea brasiliensis (rubber tree) wood formation and consequently, wood properties. The impact tapping (cutting made in the bark of the tree for latex harvest) has on the tree and the way the tree responds after tapping is often overlooked. Knowledge on wood properties of tapped rubber trees in Nigeria would enhance its sustainable utilization which is especially important in developing countries where lumber is limited. Variation in specific gravity and shrinkage of rubberwood wood due to tapping duration was examined. Tapping duration had significant effect in specific gravity and longitudinal shrinkage of rubberwood but had no effect on tangential and radial shrinkage. The specific gravity (SG) of rubberwood ranged from 0,55 - 0,59. Longitudinal shrinkage (average 1,42 %) was higher than typically observed for mature wood. Average tangential shrinkage for rubberwood of all the ages was 5,37 % while radial shrinkage ranged from 2,87 % to 3,84 %. decrease in SG observed in trees tapped for 20 years may indicate the initiation of senescence. Tapped rubberwood could be used in areas not exposed to high moisture as well as in other wood composites.

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.

We examined the within-tree variation of pulp yield and lignin content for loblolly pine ( Pinus taeda L.) trees aged 13 and 22 years. Radial trends in pulp yield (increase) and lignin (decrease) were consistent with what would be expected for loblolly pine as were changes in properties related to maturation. Maps, based on the average of 18 trees at each age, depicting pulp yield variation within-tree were similar to loblolly pine maps reported for microfibril angle and stiffness, while lignin maps resembled the inverse of those reported for density and related properties. Mixed-effects models for both properties were developed with the base model for pulp yield explaining 64% of the observed variation, with the inclusion of tree height improving the model slightly, whereas models for lignin content explained 44% of the variability. The models could be incorporated into growth and yield prediction systems, or procurement model systems that predict within-tree wood properties based on age and tree size.

The moisture content (MC) of felled trees has a direct impact on transportation costs and efficiency. Transpirational (or field) drying of fallen trees, to reduce MC and subsequently improve the economics of transport can be employed; however, an understanding of seasonal drying rates is required. Typically load cells have been used to track moisture changes in bundles of logs but where access is limited this approach is impractical. Time-domain reflectometry (TDR) provides an alternative approach and was used to monitor seasonal changes in transpirational drying rates for felled loblolly and slash pine at a Lower Coastal Plain site in Florida and loblolly pine at a Piedmont site in Georgia on a weekly basis for approximately one year. Different transpirational drying rates and minimum MC’s were observed by season. Drying rates observed during summer, fall and spring, at both test locations, indicate that after three weeks an equilibrium (or minimum) MC is achieved. Winter drying is slower, and up to 5 weeks in the field (or even longer) may be required. Post equilibrium felled log moisture content continued to vary during most seasons with rainfall events the most probable cause. TDR provides a viable approach for monitoring transpirational drying and subsequent MC changes in felled trees.

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 (R-c(2) = 0.85, R-p(2) = 0.85), S (R-c(2) = 0.83, R-p(2) = 0.76), and w (R-c(2) = 0.89, R-p(2) = 0.93) models having very good calibration / prediction statistics, while those for T and R diameter were moderate (R-c(2) = 0.79, R-p(2) = 0.57) and poor (R-c(2) = 0.64, R-p(2) = 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.

Near-infrared (NIR) spectra or NIR-hyperspectral images obtained from radial strips or wood discs provide a cost-effective methodology for examining wood property variation within trees. The calibration used for wood property prediction is critical and can be obtained using two fundamentally different approaches. One involves using a spatial-specific model where wood property data and corresponding spectral data are measured at the same resolution for calibration and prediction, e.g. 10-mm radial increments. The other provides a spatial-interpolated model and involves measuring a property on a broad-scale, e.g. whole-tree, calibrating this data against NIR spectra representing the equivalent scale and then using the calibration to predict the property at higher resolution. To understand the impact of these approaches on subsequent patterns of within-tree variation, whole-tree air-dry density (ADD) and coarseness maps, based on data obtained using the two different approaches, were compared. Patterns of ADD and coarseness variation were comparable indicating that both approaches can be utilized to examine within-tree variation. Spatial-interpolated models have a distinct advantage; being based on whole-tree (or disc) samples, they greatly reduce the cost of wood property analysis and allow the development of maps for properties that are costly and difficult to measure, for example, pulp yield.

Seasonal variation in the moisture content (MC) of standing trees can have a significant impact on wood (and when harvested) log weight; however, its variation is poorly understood owing to the destructive nature of sampling methodologies. To improve our understanding of temporal moisture variation, low cost systems that continuously monitor MC of standing trees are required. Time domain reflectometry (TDR) was explored as an option to estimate standing tree MC. TDR data was collected from ten loblolly and ten slash pine trees growing on the Lower Coastal Plain of Florida and ten loblolly pine from the Piedmont of Georgia on a weekly basis for approximately 1 year. Site specific calibrations were used to predict MC, but owing to a pronounced wound response it was not possible to accurately track temporal changes in whole-tree MC. If calibrations more oriented toward living trees can be obtained, it may be possible to use TDR to monitor temporal changes in standing tree MC.

Relationships between static bending modulus of elasticity (MOE) and SilviScan (SS) properties (SilviScan MOE [MOESS], specific gravity, and microfibril angle) were explored. Seventy-three clearwood specimens (25 by 25 by 406 mm) were cut from thirty-two 33-year-old loblolly pine trees. Relationships were calculated between MOE and MOESS (R-2 = 0.77); however, MOESS, calibrated using sonic resonance, averaged 25 percent higher than static MOE. Calibrating MOESS to static MOE instead of sonic resonance MOE resulted in similar prediction performance (R-2 = 0.77), but more importantly approximately equal prediction values. The results demonstrate the importance of properly utilizing SilviScan information for predicting loblolly pine properties in static bending.

With conifer plantations having an increasingly important role in meeting the fiber needs of society, an understanding of the effect of silvicultural practices on wood quality is critical. The perception of wood quality varies, making it hard to define in a single statement; however, possibly the most succinct definition is “a measure of the aptness of wood for a given use”. In general, properties that have a positive influence on a specific product assist in defining changes in wood quality. Since wood properties exhibit large variability within annual rings, within trees, and among trees in a stand, and have both genetic and environmental components (i.e., vary with different physiographical regions), it is imperative to have an understanding of wood properties at multiple levels. In this paper, we review the typical variation patterns in wood properties of conifers, with specific emphasis on loblolly pine (Pinus taeda L.), and radiata pine (Pinus radiata D.Don), two of the most common conifer plantation species globally. We also describe the impact of conventional silvicultural treatments on wood quality. Modeling efforts to predict variation in wood properties within trees, and in response to silvicultural treatments are also summarized.

Maps developed using Akima's interpolation method were used to compare patterns of within-tree variation for Pinus taeda L. (loblolly pine) wood properties in plantation-grown trees aged 13 and 22 years. Air-dry density, microfibril angle (MFA) and modulus of elasticity (MOE) maps represented the average of 18 sampled trees in each age class. Near infrared (NIR) spectroscopy models calibrated using SilviScan provided data for the analysis. Zones of high density, low MFA and high MOE wood increased markedly in size in maps of the older trees. The proportion of wood meeting the visually graded No. 1 (11 GPa) and No. 2 (9.7 GPa) MOE design values for southern pine lumber increased from 44 to 74% and from 58 to 83% respectively demonstrating the impact of age on end-product quality. Air-dry density increased from pith to bark at all heights but lacked a significant trend vertically, while radial and longitudinal trends were observed for MFA and MOE. Changes were consistent with the asymptotic progression of properties associated with full maturity in older trees.

Loblolly pine ( Pinus taeda ) logs can be evaluated using acoustic velocity whereby threshold acoustic velocity values can be set to ensure lumber meets specified mechanical property design values for modulus of elasticity.

Prior to the 1980s, the allowable stresses for lumber in North America were derived from testing of small clear specimens. However, the procedures were changed because these models were found to be inaccurate. Nevertheless, small clear testing continues to be used around the world for allowable stress determinations and in studies that examine forest management impacts on wood quality. Using small clear and nondestructive technologies is advantageous because of the ease of obtaining and testing small clear specimens compared with lumber. The objective of this study was to compare mechanical properties in bending of small clear specimens with lumber specimens of loblolly pine. For this study, 841 pieces of lumber in the No. 1 to No. 3 grades and nominal 2 x 4 to 2 x 10 (38 x 89 to 38 x 235 mm) sizes were collected from a forest-through-mill study and tested in static bending. A small clear specimen (25 x 25 x 410 mm) was prepared from each piece of lumber and tested in static bending. The effect of growth ring orientation was explored, and overall, samples tested on the radial or rift face explained the variation in lumber more accurately than did samples tested on the tangential face. However, the relationships were generally poor for modulus of elasticity (MOE) (R-2 = 0.22) and modulus of rupture (MOR) (R-2 = 0.11) pooled data. A lumber-based multiple regression model explained 44% and 37% of the variability for MOE and MOR, respectively, whereas a stand-based multiple regression model explained 41% and 29% of the variability for MOE and MOR, respectively.

Loblolly pine is increasingly grown on intensively managed plantation forests that yield excellent growth; however, lumber cut from these trees often contains a large percentage of juvenile wood which negatively impacts strength and stiffness. Because of changing forest management and mill practices the design values for visually graded southern pine were updated in 2013 to more accurately account for the material properties available in commerce. This study was undertaken to assess the bending strength and stiffness of loblolly pine lumber from intensively managed stands located on the Georgia Lower Coastal Plain. Eight hundred and forty-one pieces of lumber sawn from 93 trees age 24–33 years were tested in four-point bending according to ASTM International standards. The No. 1 grade MOE15 (11.9 GPa) was greater than the current (11.0 GPa) design value and comparable to the previous (11.7 GPa) design value. The No. 2 grade MOE15 (10.6 GPa) was greater than the current (9.7 GPa) design value but slightly less than the previous (11.0 GPa) design values. The No. 3 grade MOE15 (9.3 GPa) was between the current (9.0 GPa) design value and the previous (9.7 GPa) design value. Altogether, these results point to the MOE15 mean values being reasonably comparable to the previous design values and currently meeting or exceeding the current design values for visually graded southern pine lumber.

Wet storage of logs under sprinklers is often used to maintain log quality and to provide consistent fiber supply to wood production facilities. Concerns about water use in the southeastern United States have increased interest in refining water application strategies in woodyards. By understanding how the moisture content of stored logs varies over time in response to varying rates of water application, an optimum moisture regime for stored logs could be identified. In this study, experimental trials with nominal water application (100 mm/day) and a 30% reduction in water application were established at two hardwood woodyards in Georgia (Offerman, with sweet-gum and yellow poplar, and McBean, with red oak and sweetgum). Variations in log moisture were monitored using time domain reflectometry for 12 months at Offerman and 15 months at McBean. Significant differences between treatments were observed initially, likely resulting from pre-existing differences in the wood before the start of the experiment, but differences in log moisture soon disappeared. Pulping trials conducted using McBean woodyard logs stored for 9, 12, and 15 months found that treatment had no effect on pulp yield, indicating that a 30% reduction in the amount of water applied results in little change in log quality.

Time-domain reflectometry (TDR) can be used to predict the moisture content in porous materials, including soil, and is an exciting tool that could be used to measure the moisture content in wet-stored wood. Three-rod probes with 127 mm- or 152 mm-long rods were inserted into 62 loblolly pine and 34 sweetgum saturated bolts. The bolts were air dried over a span of five weeks. TDR waveforms and moisture content were periodically recorded. In total, 534 and 482 readings were taken for the loblolly pine and sweetgum bolts, respectively. An algorithm in R was written to automatically analyze the apparent length of the TDR rods. Calibration models were developed between moisture content and X (apparent length / actual rod length). A three-parameter logistic model was developed for loblolly pine (R2=0.64) and sweetgum (R2=0.84). The process was repeated using shorter bolts and 152 mm-long rods, resulting in improved models for loblolly pine (R2=0.99) and sweetgum (R2=0.97). Overall, TDR and the algorithm written to analyze the waveforms were accurate in predicting moisture content and could be used to monitor moisture in wet-decks.

The use of clonal varieties in forestry offers great potential to improve growth traits (quantity) and wood properties (quality) of loblolly pine (Pinus taeda L.). Loblolly pine trees established via somatic embryogenesis (clones), full-sib zygotic crosses, and half-sib zygotic open-pollinated families were sampled to identify variation in growth and wood properties among and within clonal lines and zygotic controls. Increment cores 5 mm in diameter were collected at age 4 from a total of 2615 trees. Growth properties (diameter at 1.4 m and total tree height) and wood properties (whole-core density, latewood and earlywood density, and latewood percent) were measured for each tree sampled in the study. Overall, growth properties were better for full-sib seedling than for clonal lines, whereas wood density was higher for clonal lines than full-sib and open-pollinated seedlings. However, there were clonal lines with better growth and higher wood density. Clonal repeatability of both growth and wood properties across sampled sites and genetic correlations between growth and wood traits were determined, with higher repeatability observed for wood traits compared with growth traits. Significant genetic correlations were observed for tree height and wood properties, whereas weak correlations were observed for diameter and wood properties.

A study was conducted to identify geographical variation in loblolly pine bark and wood properties at the whole-tree level and to quantify the responses in whole-tree bark and wood properties following contrasting silvicultural practices that included planting density, weed control, and fertilization. Trees were destructively sampled from both conventionally managed stands and various designed experimental trials established across the southern United States by various research cooperatives and forest product industries to quantify the bark and wood properties of loblolly pine. Bark (percentage bark, specific gravity [SG], and moisture content [MC]) and wood (SG, MC, green weight of wood/m(3), and green weight of wood and bark/m(3) of volume) properties were measured from disks collected at multiple heights from sampled trees and used to compute the whole-tree bark and wood properties. Significant regional variation was observed for whole-tree bark and wood properties. Bark and wood SG showed an increasing trend from inland to coastal regions and vice versa for bark and wood MC. The effect of different silvicultural treatments on bark and wood properties were generally absent; but a significant effect on bark percentage, MC, and green weight of wood and bark/m(3) was observed for trees that received intensive treatments such as early age competition control plus multiple fertilizations.

We estimated wood quality parameters for a specific tree trunk using samples of this tree’s branch, and auxiliary samples from other similar species, based on analysis of wood density, modulus of elasticity (MOE), and microfibril angle (MFA), measured with the near-infrared spectroscopy (NIRS) and SilviScan processes.  The measured materials included a branch sample from the subject tree, also known as the smolensk birch 1 , and stem analysis disk samples from silver birch ( Betula pendula Roth) trees collected in central Poland.  We analyzed and modeled the pith-to-bark and base-to-tip density changes in the silver birch samples, and using developed models estimated the subject tree trunk air-dry wood quality parameters and compared them with published yellow birch ( Betula alleghaniensis ) and silver birch tabular data.  Then we compared the corresponding surrogated green wood parameters of the subject tree against the standard American utility wood pole parameters, and identified environmental adjustments necessary for a realistic and accurate representation of the final subject tree wood characteristics.  The final conclusions from this study are that the subject tree dry wood parameters are not significantly different (in the statistical sense) from the well-documented yellow birch parameters, which were used as their surrogate, and even without the due reductions in parameters for excessive amount of whorls and branches, and for the height of the tree brake (5 to 7 m above ground), the structural parameters of the subject tree green wood, as applicable to live tree and as surrogated by appropriate yellow birch parameters, are generally weaker than corresponding dry wood parameters for the standard American wood poles and weaker then the southern yellow pine parameters. The adjustments for the whorls and knots and height of the brake may yield some additional 50% reduction in the estimates for the subject tree structural wood parameter values.

Trees sampled from a loblolly pine mid-rotation fertilization trial were used in this study. The study was laid out in a randomized complete block design with four levels of nitrogen fertilizer as treatments: control (000N), 112 (112N), 224 (224N), and 336 (336N) kg/ha of nitrogen, with each treatment replicated in 4 blocks. Two trees were destructively sampled from each plot giving a total of 32 trees. Bolts 0.6 m in length were collected from each tree (3 bolts per tree); with the midpoint of each bolt at heights of 2.4, 7.3 and 12.2 m from the base of the tree (each bolt represented the midpoint of standard 4.9 m saw logs). Static bending samples with dimensions 25 by 25 by 406 mm (radial, tangential and longitudinal dimensions respectively) were cut from the bolts that included the 25 mm of wood produced immediately following fertilization. Data on modulus of elasticity (MOE, stiffness) and modulus of rupture (MOR, strength) were collected from clear static bending samples. Based on the analysis of variance, no significant treatment effect was observed on MOE and MOR. However, MOE and MOR decreased in wood produced immediately after fertilization for trees which received the highest level of fertilization (336N). A decreasing trend in MOE and MOR with height was also present.