Pine Heartwood Research Articles

Knotwood as a window to the indirect measurement of the decay resistance of Scots pine heartwood

Abstract There is wide variation in the extractive content and decay resistance of Scots pine (Pinus sylvestris L.) heartwood. The heartwood is not visible in standing trees and only poorly visible in timber. Therefore, it is difficult to identify extractive-rich trees, and consequently the most decay-resistant heartwood. On the other hand, knots are clearly visible in standing trees and timber. In the present paper we studied the possibility of measuring the decay resistance of Scots pine heartwood indirectly on the basis of the extractive concentration of knotwood. The material investigated consisted of 40 felled trees with a wide between-tree variation for extractive content and decay resistance of their heartwood. The extractive content of knotwood was found to be four- to five-fold higher than that of heartwood. Statistically significant correlations were found between the mass loss of heartwood and the concentrations of total phenolics and stilbenes in knotwood (r=-0.54, P<0.001 and r=-0.40, P=0.011, respectively), and for the concentration of total phenolics (r=0.42, P=0.008) and stilbenes (r=0.39, P=0.012) between heartwood and knotwood. We suggest further development of this technique in the context of rapid industrial screening of durable pine heartwood.

Measuring the decay resistance of Scots pine heartwood indirectly by the Folin-Ciocalteu assay

To exploit the variation in the natural durability of heartwood timber, screening of a large number of trees or timber is necessary. We suggest that the concentration of total phenolics, measured by the Folin–Ciocalteu (FC) assay, can be used to supplement or even replace in vitro decay tests for screening the variation in the resistance of Scots pine (Pinus sylvestris L.) heartwood timber against the brown-rot fungus Coniophora puteana (Schum. ex Fr.). We screened the juvenile heartwood of 520 Scots pine trees with the FC assay. Samples from 40 trees, with total phenolics concentrations ranging from 1.9 to 21.7 mg tannic acid equivalents (TAE)/g of heartwood, were subjected to an in vitro decay test. The correlation (r) between the total phenolics concentration and mass loss was –0.82 (p < 0.001) in the 7 week long decay test. The relationship was expressed with a linear regression equation: mass loss (mg/g) = 487 – 25 × concentration of total phenolics (mg TAE/g). This strong relationship could be exploited by replacing the decay test with the FC assay to more rapidly assess the durability of wood products.

Optimisation of a two-stage heat treatment process: durability aspects

Heat treatment of wood at relatively high temperatures (in the range of 150–280°C) is an effective method to improve biological durability of wood. This study was performed to investigate the effect of heat treatment process optimisation on the resistance against fungal attack, including basidiomycetes, molds and blue stain fungi. An industrially used two-stage heat treatment method under relatively mild conditions (<200°C) was used to treat the boards. Heat treatment of radiata pine sapwood revealed a clear improvement of the resistance against the brown rot fungi Coniophora puteana and Poria placenta. Increasing process temperature and/or effective process time during the first process stage, the hydro thermolysis, appeared to affect the resistance against C. puteana attack, but the effect on the resistance against P. placenta was rather limited. Heat treated radiata pine showed a limited resistance against the white rot fungus Coriolus versicolor and process variations during the hydro thermolysis stage appeared not to affect this resistance. A clear difference between the resistance of heat treated Scots pine sapwood and heartwood against fungal attack is observed. Scots pine heartwood showed a higher resistance against C. puteana and P. placenta but also against the white rot fungus C. versicolor. Similar results were obtained when heat treated birch was exposed to brown and white rot fungi. Heat treatment showed an improved resistance against C. puteana attack, especially at higher temperatures during the hydro thermolysis stage. A clear improvement of the durability was also observed after exposure to the white rot fungus C. versicolor and especially Stereum hirsutum. Increasing the process temperature or process time during the hydro thermolysis stage appeared to have a limited effect on the resistance against C. versicolor attack. Heat treated radiata pine and Norway spruce were still susceptible to mold growth on the wood surface, probably due to the formation of hemicelluloses degradation products (e.g. sugars) during heat treatment. Remarkable is the absence of blue stain fungi on heat treated wood specimen, also because the abandant blue stain fungi were observed on untreated specimen. Molecular reasons for the resistance of heat treated wood against fungal attack are discussed in detail contributing to a better understanding of heat treatment methods.

Qualitative and quantitative determination of extractives in heartwood of Scots pine ( Pinussylvestris L.) by gas chromatography

A method for quantitative determination of extractives from heartwood of Scots pine ( Pinus sylvestris L.) using gas chromatography (GC) with flame ionization detection (FID) was developed. The limit of detection (LOD) was 0.03 mg/g wood and the linear range ( r = 0.9994) was up to 10 mg/g with accuracy within ±10% and precision of 18% relative standard deviation. The identification of the extractives was performed using gas chromatography combined with mass spectrometry (GC–MS). The yields of extraction by Soxhlet were tested for solid wood, small particles and fine powder. Small particles were chosen for further analysis. This treatment gave good yields of the most important extractives: pinosylvin, pinosylvin monomethyl ether, resin acids and free fatty acids. The method is used to demonstrate the variation of these extractives across stems and differences in north–south direction.

Untreated Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) wood-panels exposed out of ground contact in Sweden for two years

In this study, the durability of 230 wood panels, consisting of both Scots pine (Pinus sylvestris) and Norway spruce (Picea abies), were examined in an above-ground durability field test, for two years, in southern Sweden. The samples consisted of three pieces of wood, 22×95×500 mm3. The pieces were screwed together with an overlap so as to obtain an efficient moisture trap. The results of the durability test showed large differences between Scots pine sapwood and heartwood. Sapwood displayed unacceptably high moisture contents and fungal discoloration, while heartwood had low and stable moisture contents, and lesser discoloring. Norway spruce had moisture dynamics similar to pine heartwood, although a some what higher moisture content was recorded. The differences in moisture dynamics among the spruce samples, which were divided into: juvenile wood, mature wood with horizontal annual rings, and mature wood with vertical annual rings, were small. Juvenile wood showed more discoloring caused by mould fungi. The samples with horizontal annual rings suffered massive cracks.

The water absorption of sapwood and heartwood of Scots pine and Norway spruce heat-treated at 170 °C, 190 °C, 210 °C and 230 °C

Heat-treatment changes the chemical and physical properties of wood. Wood polymers are degraded, dimensional stability is enhanced, equilibrium moisture content is lowered, colour darkens and biological durability is increased. The properties of heat-treated wood have been researched considerably, but the differences between sapwood and heartwood have not been reported separately. In this research, water absorption differences between sapwood and heartwood of Scots pine and Norway spruce heat-treated at temperatures 170 °C, 190 °C, 210 °C and 230 °C were investigated. The results were compared to industrially kiln-dried reference samples. Water absorption was determined with a floating test based on the EN 927-5 standard. The heartwood of both wood species absorbed less water than sapwood. Heat-treatment evidently decreased the water absorption of spruce and pine heartwood. The higher the heat-treating temperature, the lower the amount of absorbed moisture. However, a very interesting exception was pine sapwood, whose water absorption actually increased with heat-treatment after the three lowest heat-treatment temperatures compared to the reference material. Water absorption did not decrease until the heat-treatment temperature was 230 °C.

Termite repellent sesquiterpenoids from Callitris glaucophylla heartwood

Fractions of methanol and ethanol extracts from the heartwood of white cypress pine (Callitris glaucophylla Thompson et Johnson) were investigated for their repellent activity against subterranean termite Coptotermes formosanus Shiraki worker using a two-choice semicircular filter paper test at 0.5% (w/w) concentration. Fraction CY-E2 composed of (−)-citronellic acid, guaiol, α-, β-, and γ-eudesmol isomers as well as an unknown compound, showed the highest statistically significant repellency (97.8% ± 2.2 SEM) of all fractions tested. Bioactivity-guided fractionations using high-performance liquid chromatography led to the isolation of two, oxygenated eudesmane-type sesquiterpenes with α-methylene moieties, both termite-repellent compounds. These compounds were subsequently identified as ilicic acid methyl ester (IAME) and costic acid by means of spectroscopic analyses, electron impact mass spectrometry, and nuclear magnetic resonance spectroscopy. We report the isolation of both IAME and costic acid from C. glaucophylla heartwood for the first time.

Pulping Yield and Delignification Kinetics of Heartwood and Sapwood of Maritime Pine

In maritime pine (Pinus pinaster Ait.), heartwood represents a substantial part of the tree stem at final harvest age (80 years) corresponding to 42% at the base of the stem wood diameter and decreasing upward. The rate of heartwood formation was estimated at 0.35 rings/year, beginning at 18 years of age. Differences in the chemical composition between heartwood and sapwood were mainly in the extractives, 19.7% and 5.8%, respectively. The lignin content was 23.1% and 24.5% in the heartwood and sapwood, respectively. Pulping yield of the heartwood was lower than that of the sapwood (40.0% vs. 49.7%) and was negatively correlated with the extractives content. Extraction of heartwood prior to pulping increased the pulp yield and the delignification (lower residual lignin in pulps). Pulping kinetics showed lower yields for heartwood at all pulping stages, the difference occurring especially in the initial reaction phase. However, delignification rate constants were similar for heartwood and sapwood (3.1×10−2 min−1 and 2.7×10−2 min−1 for the main delignification phase for sapwood and heartwood, respectively), with a lower activation energy for sapwood (68.3 vs. 90.0 kJ · mol−1). The presence of heartwood decreases the raw‐material quality for pulping and this should be taken into account when harvesting trees for pulping processes.

Mycologg: a new accelerated test method for wood durability above ground

If not properly handled, selected and protected, wood will be degraded by bacteria, fungi and also insects. In order to ensure service life, durability tests are needed. Most accelerated laboratory tests on wood durability are focused either on fungi attacks or the uptake of moisture. Accelerated field tests in ground contact are of limited use since they could be difficult to reproduce and are sensitive to the characteristics of the soil in which the wood is placed. In addition, the results cannot be directly transferred to wood in use above ground because such wood is subjected to different set of conditions. The Mycologg is a new accelerated test method for estimating the durability of wood in above ground applications. The Mycologg allows the test panels to be subjected to the discolouring fungi and different RH (relative humidity) cycles simultaneously. Every 30 min, the temperature, the RH, and the moisture content in each test panel are measured and saved in special software. This allows for a constant update of the moisture patterns during a fungi attack. A trial was made with Scots pine (Pinus sylvestris) heartwood samples, where fungal growth after 6, 8 and 10 weeks in the Mycologg were compared to weather exposure of duplicate samples after 12, 16, and 26 months. The results showed that 10 weeks into the Mycologg accelerated test method corresponds well to real-time weather exposure with respect to fungal discolouration.

Non-destructive prediction of decay resistance of pinus sylvestris heartwood by near infrared spectroscopy

Restrictions on the use of wood preservatives have increased interest in the utilization of the natural durability of wood. In Scandinavia Scots pine (Pinus sylvestris L.) is an important commercial tree species. Its heartwood has traditionally been used in constructions exposed to risk of decay. In a laboratory experiment Scots pine wood specimens sampled from inner heartwood, outer heartwood and sapwood were exposed to the brown rot fungus Poria placenta. Outer heartwood was found to be more resistant than inner heartwood and sapwood. Near infrared spectroscopy (NIR) spectra obtained on solid wood before decay testing were used in multivariate calibrations to predict decay resistance of heartwood. Results from multiple test set validated partial least squares regression models showed that resistance to decay in Scots pine heartwood could be predicted with satisfying precision using NIR spectroscopy. As NIR spectra were collected on solid wood, development of the method for industrial use is potentially possible.

My Brief Encounter with the Phosphoinositides and IP3

. Before describing thisresearch, however, I should say how that choice came about. While in graduate school at theUniversity of Wisconsin, I had had the good fortune to study under Karl Paul Link, who waswidely renowned for his discovery of dicumarol and the synthesis of related blood anticoagu-lants such as warfarin, work that was recognized with two Lasker Awards (1). On the side,however, Link remained a carbohydrate chemist at heart, a hobby that had grown out of hisstudies on plant polysaccharides and uronic acids while a student and then a young facultymember. In fact, Stanford Moore had completed his doctoral dissertation with Link on amethod for characterizing aldo-monosaccharides as benzimidazole derivatives (2).I arrived at Madison in the fall of 1946, fresh from a stint in the United States Navy, andI found Link’s laboratory bursting at the seams with about 15 ex-GIs, all hard at work tryingto make up for lost time. During earlier investigations on the structure-function relationshipof coumarin anticoagulants, an attempt to synthesize the glucoside of dicumarol had beenfrustrated because the acetylated intermediate was degraded in alkali under conditions usedfor deacetylation (3). Because glycosides are acetals, which are typically acid-labile andalkali-stable, I found the anomaly intriguing and decided to study a variety of syntheticcompounds in an effort to understand the structural basis for alkali sensitivity (4). Thisresearch formed the core of my doctoral dissertation, and although I failed to recognize it at thetime, the chance exposure to carbohydrate chemistry was to have a lasting influence on thedirection my career would take.I continued my indoctrination in sugar chemistry during a postdoctoral year in Edinburgh,Scotland, with E. G. V. Percival in the new Department of Chemistry at Kings Buildingsheaded by Edwin Hirst. This was a time of economic depression in Britain, which was stillsuffering the aftermath of the war, and I discovered that I had left a well equipped laboratoryin Madison to engage an unexpectedly primitive research environment. Wisely I did not letthis change in fortunes discourage me. Instead I undertook a project dealing with the structureof maple sapwood starch and did the best that I could with the available facilities (5). Myefforts were well rewarded because, in the process, I became adept at the uses of analytical andpreparative filter paper and cellulose column chromatography, skills that were to be extremelyvaluable in my later research. The greatest challenge to my ingenuity, however, was toconstruct an electric stirring device from a small board-mounted motor, a couple of woodenpulleys, a piece of string, and a glass rod. The speed of the motor was regulated by adjustinglight bulbs that were wired in series with the power cord to draw off electricity, a crude buteffective method of control. I have always enjoyed working with my hands, so this mundaneproject even took on a certain appeal.Living in a new environment always has its fringe benefits. While in Edinburgh, I developeda special affection for the Scots and a better understanding for the lingering resentment that

The use of sensor array technology for rapid differentiation of the sapwood and heartwood of Eastern Canadian spruce, fir and pine

The quality of the pulp and paper produced in eastern Canada is affected by the proportions of black spruce (Picea mariana), balsam fir (Abies balsamea) and jack pine (Pinus banksiana) present in the wood chips used. A rapid analytical method capable of differentiating the wood of these three species of conifer is a prerequisite to developing a procedure to determine these proportions. This differentiation was achieved through the use of an electronic nose made up of an array of conductive polymer-carbon black composites-based sensors. The procedure is rapid and involves training and validation of the e-nose using reference wood samples followed by identification of unknown samples. Principal Component Analysis is performed on the smell-prints obtained during the training phase. Complete discrimination of the sapwood and heartwood of the three conifers was achieved. The reference and the unknown samples must be measured under identical conditions.

A UV resonance Raman (UVRR) spectroscopic study on the extractable compounds in Scots pine ( Pinus sylvestris) wood : Part II. Hydrophilic compounds

Hydrophilic extracts of Scots pine ( Pinus sylvestris) heartwood and sapwood and a solid Scots pine knotwood sample were studied by UV resonance Raman spectroscopy (UVRRS). In addition, UVRR spectra of two hydrophilic model compounds (pinosylvin and chrysin) were analysed. UV Raman spectra were collected using 244 and 257 nm excitation wavelengths. The chemical composition of the acetone:water (95:5 v/v) extracts were also determined by gas chromatography. The aromatic and oleophilic structures of pinosylvin and chrysin showed three intense resonance enhanced bands in the spectral region of 1649–1548 cm −1. Pinosylvin showed also a relatively intense band in the aromatic substitution region at 996 cm −1. The spectra of the heartwood acetone:water extract showed many bands typical of pinosylvin. In addition, the extract included bands distinctive for resin and fatty acids. The sapwood acetone:water extract showed bands due to oleophilic structures at 1655–1650 cm −1. The extract probably also contained oligomeric lignans because the UVRR spectra were in parts similar to that of guaiacyl lignin. The characteristic band of pinosylvin (996 cm −1) was detected in the UVRR spectrum of the resin rich knotwood. In addition, several other bands typical for wood resin were observed, which indicated that the wood resin in the knotwood was resonance enhanced even more than lignin.

Investigations into the photodegradation of wood using microtensile testing

This paper describes an investigation into the effect of moisture on the photodegradation of wood. The species investigated were Scots pine, Norway spruce and western red cedar. Photodegradation rates were determined from the changes in microtensile strength of thin wood veneer strips exposed to artificial weathering. Ultra-violet (UV) irradiation was carried out at a temperature of approximately 60 °C and a range of relative humidities starting with exposure at 30% relative humidity. Weathering regimes intended to increase the exposure to moisture were created by periodic wetting, exposure under conditions of constant high relative humidity or by exposure in the presence of liquid water. Moisture enhanced the photodegradation processes of wood. Photodegradation rates increased sharply as the moisture increased in severity. However exposure to higher moisture conditions unexpectedly caused a strength increase in the initial stage of weathering, although the subsequent rates of strength loss were very rapid indeed. The degradation of wood in the presence of liquid water was so intense and rapid that the differences between the species were difficult to distinguish. Norway spruce was the species found to be the most sensitive to photodegradation, while the heartwood of Scots pine proved more resistant to photodegradation than the sapwood.

Isolation and characterisation of water soluble polysaccharides from Norway spruce and Scots pine

Water soluble polysaccharides from Norway spruce, Scots pine, and Siberian larch were compared. For all species the total amount of polysaccharides isolated from the heartwood was higher than that from the sapwood. The heartwood polysaccharides had a high content of galactose and arabinose units, and some glucuronic acid units, suggesting the presence of acidic arabinogalactans. The total amounts of recovered water-soluble arabinogalactans were 1.9 mg/g for spruce heartwood, 5.3 mg/g for pine heartwood, and as much as 106 mg/g for larch heartwood. The other water-soluble polysaccharides were mainly glucomannans. The average ratio of Gal:Ara:GlcA in the water-soluble arabinogalactans of spruce heartwood was about 4.3:1:1, pine heartwood about 4.5:1:0.2, and larch heartwood about 6.7:1:0.1. The corresponding molar ratios then being about 3.6:1:0.8 for spruce, 3.8:1:0.2 for pine, and 5.6:1:0.08 for larch. Thus, the content of glucuronic acid units was especially high in the spruce heartwood arabinogalactans. The content of arabinose was slightly higher in spruce and pine than in larch heartwood arabinogalactans.

The concentration of phenolics in brown-rot decay resistant and susceptible Scots pine heartwood

The concentrations of three individual stilbenes, pinosylvin (PS), pinosylvin monomethyl ether (PSM), and pinosylvin dimethyl ether (PSD), and the total concentration of phenolic compounds were determined in 34-year-old Scots pines which were known to have either decay-resistant or susceptible heartwood. The sample trees were selected from two progeny tests among 783 trees; the decay resistance of which had been screened earlier in vitro against a brown-rot fungus Coniophora puteana. Ten decay-resistant and ten susceptible trees from each of the progeny tests were analysed. In the heartwood of the resistant trees, the average total concentration of the stilbenes was 7.5 and 6.4 mg/g of dry weight, while in the heartwood of the susceptible trees the respective values were 5.0 and 4.7 mg/g. The difference between the decay resistant and susceptible trees was statistically significant in both progeny tests. The difference in concentration of total phenolics, analysed by the Folin-Ciocalteu method, was also significant. A high concentration of phenolics was connected to the low hygroscopicity of wood. The results support the argued hypothesis that the stilbenes make a contribution to the differences in the decay rate of natural wood substrate. On the other hand, the results show that the stilbenes alone do not explain the variation in decay rate.

Measurement of moisture content profiles during drying of Scots pine using magnetic resonance imaging

Abstract Moisture content profiles with high spatial pixel resolution, 21 μm, were measured in Scots pine heartwood while drying from wet conditions to near equilibrium in the surface layer, (0–300 μm). The measuring technique used was Magnetic Resonance Imaging. In order to obtain magnetic resonance profiles with a high pixel resolution at both high and low moisture contents, a highg-radient permanent magnet was used. The results presented show one-dimensional moisture content profiles and mean moisture content development in the surface layer. In Scots pine heartwood, almost flat moisture content profiles were observed when the moisture content was above the fibre saturation level. When the mean moisture content in the surface layer decreases to the fibre saturation level, gradients start to build up from the surface towards the bulk of the sample although the bulk moisture content is far above the fibre saturation. Furthermore, the results presented in this study imply that a dry shell forms in the surface layer shortly after drying has begun. This dry shell controls the drying rate until the mean moisture content in the bulk decreases to the fibre saturation level.

Field exposure of Pinus heartwoods to subterranean termite damage (Isoptera: Rhinotermitidae, Mastotermitidae)

Summary Four field trials were conducted to evaluate responses of the Australian subterranean termites Coptotermes acinaciformis (Froggatt) and Mastotermes darwiniensis Froggatt to untreated softwood timbers. The aim of the research was to determine whether the termite resistance of the heartwood of maritime pine (Pinus pinaster Aiton) and of the F1, hybrid of slash pine (P. elliottii Englem. var. elliottii L. & D.) × Caribbean pine (P. caribaea Morelet var. hondurensis Barrett & Golfari) was equivalent to that of slash pine heartwood. Containers with test specimens of maritime pine heartwood and sapwood, and slash pine heartwood and sapwood, and F1, hybrid heartwood and sapwood, together with feeder specimens of radiata pine (P. radiata D.Don) sapwood, were prepared. These containers were placed on concrete brick assemblies, in above-ground, weather-protected situations in areas of high termite hazard. The work with C. acinaciformis was conducted at Beerburrum, in south-eastern Queensland, Australia, and termite responses were determined by losses of mass over a period of 17 weeks. The work with M. darwiniensis was conducted at Townsville, northern Queensland, and termite responses were determined by losses of mass over a period of 47 weeks. The ranking in susceptibility of the timbers is as follows: maritime pine sapwood > slash pine sapwood > F1 hybrid sapwood > slash pine heartwood = maritime pine heartwood = F1 hybrid heartwood. The heartwood of maritime pine and of the F1 hybrid of slash × Caribbean pines is highly resistant to damage by the subterranean termites C. acinaciformis and M. darwiniensis, when used in Hazard Class 2(H2) (that is, internally above-ground) situations. Accordingly, with respect to C. acinaciformis and M. darwiniensis, we recommend that limitations on the use of heartwood unpenetrated by preservative in H2 situations be removed from Australian Standards and State regulations for maritime pine and the hybrids of slash × Caribbean pines.

Moisture uptake patterns in pressure steaming of Radiata Pine

Following high temperature (HT) drying, final steaming in a pressurised environment will reduce twist degrade and enhance stability when compared to normal steaming. This improvement is the result of the enhanced relaxation of drying stresses in the hotter, pressurised environment. However, the precise mechanisms for this improvement are, as yet, unclear. A study was undertaken to evaluate the patterns of moisture uptake during pressure steaming of HT dried radiata pine lumber. Samples of radiata pine heartwood and sapwood, which had been previously high-temperature dried at 140/90°C, were pressure steamed for 15 minutes at target conditions of 150°C and 95% relative humidity (4.6 bar). Specimens rapidly attained moisture levels considerably higher than what would have been predicted by commonly applied equilibrium moisture content (EMC) relationships. Marked differences in the sorption patterns of heartwood and sapwood were also evident.

Heartwood in relation to age and growth rate in Pinus sylvestris L. in Scandinavia

Summary Knowledge about the transformation of sapwood into heartwood contributes to the understanding of the nature of pine trees and should be considered prior to the conversion of sawlogs to produce timber of prescribed properties and optimal revenue. In this study, heartwood formation was ascribed to the joint effect of ageing and growth rate. Observations of heart- and sapwood in 1656 trees and sawlogs of Scots pine (Pinus sylvestris L.), sampled throughout Scandinavia, were analysed using mixed models. The most important finding was expressed in the pine heartwood age rule: heartwood age equals the square root of cambial age less three, to the second power. This global formula was valid irrespective of environmental factors and location within the tree, and described 93 per cent of the variance in the sample. Transition rate increases from 0.6 rings a ‐1 at 50 years to 0.8 rings a‐1 at 200 years. The spatial amount of heartwood might be influenced by the silviculture through the annual ring width pattern. For samples missing sapwood, e.g. archaeological wood, the results might be combined with dendrochronology in specimen dating. When the diameter and the heartwood diameter of sawlogs were known, the mean annual ring width could be estimated with a standard deviation of 0.5 mm a ‐1 . The simplicity, consistency and high correlation of the pine heartwood age rule confirms the importance of age as the main factor in heartwood formation.