Climate influences the leaf area/sapwood area ratio in Scots pine

We tested the hypothesis that the leaf area/sapwood area ratio in Scots pine (Pinus sylvestris L.) is influenced by site differences in water vapor pressure deficit of the air (D). Two stands of the same provenance were selected, one in western Scotland and one in eastern England, so that effects resulting from age, genetic variability, density and fertility were minimized. Compared with the Scots pine trees at the cooler and wetter site in Scotland, the trees at the warmer and drier site in England produced less leaf area per unit of conducting sapwood area both at a stem height of 1.3 m and at the base of the live crown, whereas stem permeability was similar at both sites. Also, trees at the drier site had less leaf area per unit branch cross-sectional area at the branch base than trees at the wetter site. For each site, the average values for leaf area, sapwood area and permeability were used, together with values of transpiration rates at different D, to calculate average stem water potential gradients. Changes in the leaf area/sapwood area ratio acted to maintain a similar water potential gradient in the stems of trees at both sites despite climatic differences between the sites.     

Dimensional changes in Corsican and Scots pine sapwood due to reaction with crotonic anhydride

 The effects of the reaction temperature and varying level of weight gain on the dimensional stabilisation of crotonic anhydride modified Corsican and Scots pine sapwood were investigated. With Corsican pine at low levels of substitution, the reagent occupied larger molar volumes in the cell wall than at higher weight gains. With Scots pine the molar volume occupied by reagent was found to be temperature dependent at low levels of substitution. Dimensional stabilisation was determined by the water-soak/oven-dry method through a total of ten cycles in order to determine the stability of the ester bond to hydrolysis at neutral pH. It was found that the reaction temperature has no significant effect on dimensional stability provided the same weight gain level is obtained. At weight gain levels in excess of 30%, values of anti-shrink efficiency of 90% were obtained. Received 2 April 1999     

Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood

Studying the impregnation and distribution of oil-based preservative in dried wood is complicated as wood is a nonhomogeneous, hygroscopic and porous material, and especially of anisotropic nature. However, this study is important since it has influence on the durability of wood. To enhance the durability of thermally modified wood, a new method for preservative impregnation is introduced, avoiding the need for external pressure or vacuum. This article presents a study on preservative distribution in thermally treated Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) sapwood using computed tomography scanning, light microscopy, and scanning electron microscopy. Secondary treatment of thermally modified wood was performed on a laboratory scale by impregnation with two types of preservatives, viz. Elit Träskydd (Beckers) and pine tar (tar), to evaluate their distribution in the wood cells. Preservative solutions were impregnated in the wood using a simple and effective method. Samples were preheated to 170 °C in a drying oven and immediately submerged in preservative solutions for simultaneous impregnation and cooling. Tar penetration was found higher than Beckers, and their distribution decreased with increasing sample length. Owing to some anatomical properties, uptake of preservatives was low in spruce. Besides, dry-induced interstitial spaces, which are proven important flow paths for seasoned wood, were not observed in this species.     

Anatomical differences in the structural elements of fluid passage of Scots pine sapwood with contrasting treatability

Treatability of wood is a function of anatomical properties developed under certain growing conditions. While Scots pine sapwood material normally is considered as easy to impregnate, great variations in treatability can be observed. In order to study anatomical differences in the structural elements of transverse fluid passage, wood material with contrasting treatability has been compared. Ray composition and resin canal network, membrane areas of fenestriform pits in the cross-field as well as dimension and properties of bordered pits were investigated. The results showed large anatomical differences between the two contrasting treatability groups. Refractory Scots pine sapwood samples developed more rays per mm² tangential section, while they were on average lower in cell numbers than rays found in easily treatable material. Easily treatable material had more parenchyma cells in rays than refractory material. At the same time, a larger membrane area in fenestriform pits in the cross-field was observed in the easily treatable sample fraction. Differences in the composition of resin canal network were not observed. Refractory samples developed on average smaller bordered pit features, with relatively small formed pit apertures compared to the easily treatable samples. In refractory Scots pine sapwood material, the structural elements of fluid passage such as bordered pit dimensions, fenestriform pits in the cross-field and parenchyma cells were altogether developed in smaller dimensions or number. Wood samples from better growing conditions and sufficient water supply showed a better treatability in this study.     

Neutral lipids and phospholipids in Scots pine (Pinus sylvestris) sapwood and heartwood

Variations in the concentration and composition of triacylglycerols, free fatty acids and phospholipids were analyzed in Scots pine (Pinus sylvestris L.) trees at five sites. Disks were taken at breast height or at a height of 4 m from the stems of 81 trees differing in diameter and growth rate. The mean concentration of triacylglycerols in sapwood was 26 mg g(-1) dry mass; however, variation among trees was large (16-51 mg g(dm)(-1)). The concentration of triacylglycerols was slightly larger at 4 m height in the stem than at breast height. Concentrations of triacylglycerols did not differ between the sapwood of young and small-diameter stems (DBH < 12 cm) and the sapwood of old stems (DBH > 36 cm). Concentrations of free fatty acids were negligible in the outer sapwood, but ranged between 5 and 18 mg g(dm)(-1) in the heartwood. The most abundant fatty acids of triacylglycerols were oleic (18:1), linoleic (18:2omega6, 18:2Delta5,9), linolenic (pinolenic, 18:3Delta5,9,12 and 18:3omega3) and eicosatrienoic acid (20:3Delta5,11,14 and 20:3omega6). The concentration of linoleic acid comprised 39-46% of the triacylglycerol fatty acids and the concentration was higher in the slow-growing stem from northern Finland than in the stems from southern Finland. Major phospholipids were detected only in sapwood, and only traces of lipid phosphorus were detected in heartwood.     

Variation in treatability of Scots pine sapwood: a survey of 25 different northern European locations

The treatability of Scots pine sapwood sampled from 25 locations in northern Europe, which was impregnated with an experimental furfuryl alcohol mix, was studied. A large variation in treatability was found between stands. The treatability was affected by anatomical properties of the trees and therefore also by the immediate climate, the sociological position of the tree in the stand, growth increments and on-stand competition. With the models applied, most parts of the differences in treatability between stands could be explained, while the treatability variation between trees within a stand remained mostly unexplained. Wider annual rings and higher latewood contents were found to increase the treatability. Models that included data on growth conditions and climate explain more of the variation in treatability, indicating that also other anatomical properties are influencing the treatability. Tree attributes and growth conditions that reduce annual ring width and latewood content decreased the treatability. Trees growing under warmer conditions and developing larger growth increments were easier to impregnate. Wood from trees growing near the timberline and under environmental conditions impairing wood growth was more difficult to treat.     

Chemical modification employed as a means of probing the cell-wall micropore of pine sapwood

The cell-wall micropore network of oven-dried Corsican and Scots pine sapwood has been investigated by reaction with acetic and propionic anhydride in a non-swelling solvent (xylene). No significant reaction occurred, except in the case of reaction between Corsican pine and acetic anhydride. However, when the wood samples were in a swollen state, reaction occurred between the wood and both anhydrides. It is concluded that the cell-wall micropores of Corsican pine are sufficiently large to allow access of acetic anhydride, but not propionic into the unswollen cell wall; however, with Scots pine, both reagents are too large to gain access. A further series of experiments was performed whereby the volumetric changes of pine sapwood samples due to modification with a range of linear chain anhydrides were determined. With Corsican pine, larger volume changes than theoretically predicted were observed, whereas, with the Scots pine samples, the volume changes were close to those predicted. When account is taken of the volume that the reagent occupies within the cell wall, it was found that larger void volumes occurred in the Corsican pine samples. This result indicates that the cell-wall polymeric environment surrounding a reagent molecule is more compliant in the case of Corsican pine.     

The influence of different soil substrates on the service life of Scots pine sapwood and oak heartwood in ground contact

Abstract

The durability of wood in ground contact is affected by numerous influences, such as substrate quality, climate and microflora of the soil, which need to be considered for the prediction of service life of wooden components to be used in the ground. In this study the influence of different soil substrates on the service life of Scots pine sapwood (Pinus sylvestris L.) and oak heartwood (Quercus petraea Liebl.) was investigated. Mini-stakes were exposed in six different soils at the test site of the Federal Research Centre for Forestry and Forest Products (BFH) in Hamburg, Germany. The effect of partly embedding the test samples in concrete or polyethylene films was also examined. After 3 years of exposure the decay rates for both wood species differed significantly between the soil substrates. Compost soil and fertilized test field soil induced the highest decay activity, whereas in pure sand the lowest decay rates were observed. Surprisingly, exposure in gravel also led to higher decay ratings than sand. Protective measures by means of concrete embedding and polyethylene films performed well during the first 2 years of exposure, but showed increasing decay rates in the third year. The overall decay rating for all soil types was higher for oak heartwood than for pine sapwood. The meaning of different soils, independent of other site influences, for service life prediction of wood is discussed, and the need for further studies on this topic is highlighted.     

Effects of timing of soil frost thawing on Scots pine

Effects of the timing of soil thawing in the spring on Scots pine (Pinus sylvestris L.) were studied under controlled laboratory conditions. Sixteen 6-year-old saplings were lifted from the field, replanted in containers and placed in four treatments in controlled environment (CE) chambers with four replicate saplings per chamber. The saplings were held in the CE chambers during one simulated winter and one simulated growing season. The soil was frozen to -2 degrees C during a second simulated winter in the CE chambers, and the soil thawing treatments began at the end of the second simulated winter. Soil thawing began at various times before (no delay in thawing) and after (delay in thawing) chamber air conditions were changed from simulated winter to simulated summer. Delayed soil thawing subjected saplings to stress, with the severity of stress depending on the length of the delay in thawing. If there was no delay or only a short delay in soil thawing, stress was minor and reversible. A 2-week delay in soil thawing led to death of the saplings. Stress was apparent as decreases in the variable to maximal chlorophyll fluorescence ratio (Fv/Fm), chlorophyll a/b ratio and needle water potential. In needles of stressed saplings, apoplastic electrical resistance first decreased and then increased and there were anomalies in the electrical impedance spectra of the stems. Stress from the soil thawing treatments affected both root and shoot growth.     

The influence of different soil substrates on the service life of Scots pine sapwood and oak heartwood in ground contact

The durability of wood in ground contact is affected by numerous influences, such as substrate quality, climate and microflora of the soil, which need to be considered for the prediction of service life of wooden components to be used in the ground. In this study the influence of different soil substrates on the service life of Scots pine sapwood (Pinus sylvestris L.) and oak heartwood (Quercus petraea Liebl.) was investigated. Mini-stakes were exposed in six different soils at the test site of the Federal Research Centre for Forestry and Forest Products (BFH) in Hamburg, Germany. The effect of partly embedding the test samples in concrete or polyethylene films was also examined. After 3 years of exposure the decay rates for both wood species differed significantly between the soil substrates. Compost soil and fertilized test field soil induced the highest decay activity, whereas in pure sand the lowest decay rates were observed. Surprisingly, exposure in gravel also led to higher decay ratings than sand. Protective measures by means of concrete embedding and polyethylene films performed well during the first 2 years of exposure, but showed increasing decay rates in the third year. The overall decay rating for all soil types was higher for oak heartwood than for pine sapwood. The meaning of different soils, independent of other site influences, for service life prediction of wood is discussed, and the need for further studies on this topic is highlighted.     

Effects of liming on chemical properties of soil, needle nutrients and growth of Scots pine transplants

The effects of limestone (2.0 and 4.0 Mg ha⁻¹) on chemical properties of soil, nutrient concentrations of needles and growth of Scots pine (Pinus sylvestris L.) transplants were investigated on three reforestation areas on infertile acidic sites in southern Finland. The limestone was applied either on the soil surface (unploughed plots) or was mixed into the topsoil (ploughed plots). All the treatments were replicated four times. Surface broadcast of lime elevated the pH in the organic layer and in the 0-10 cm layer of mineral soil. The increase in the pH of the organic layer after 21 years was, on average, 0.7 and 1.1 pH units, with a dose of lime 2 and 4 Mg ha⁻¹, respectively. On the ploughed plots, the pH in the uppermost 0-10 cm soil layer was 0.4-0.5 units higher than on the corresponding unlimed plots. Both doses of lime significantly increased the amount of exchangeable Ca and the base saturation (BS) in the topsoil on the ploughed plots, and the amount of exchangeable Ca and Mg, as well as the base saturation (BS) in the organic layer + the 0-10 cm layer of mineral soil on the unploughed plots. Regardless of the techniques used for application of lime, after 21 growing seasons the Ca and Mg concentrations in needles were significantly higher on the limed plots than on the controls. In needles, the Ca/Mn ratio was the best indicator for measuring the response to liming. Only on the unploughed plots did liming increase stand volume and dominant diameter of pines. Intensive disc ploughing produced significantly more stems and increased both stand volume and the dominant height of pines compared to unploughed plots.     

Variation in treatability of Scots pine (Pinus sylvestris) by the chemical modification agent furfuryl alcohol dissolved in water

Scots pine (Pinus sylvestris) sapwood was investigated for variation in treatability using the wood modifying agent, furfuryl alcohol (FA) in water. The variation in treatability within trees, between trees and between different stands of Scots pine was studied. Investigated variables that reduced the residual variance significantly were: site location, latitude of site, height of trees, annual ring width, vertical and horizontal position in the tree and method of drying. Linear mixed model statistics were used and tree number was handled as a random variable. The best model reduced the treatability residual variance by 67%. Location was the single factor affecting treatability most. Differences in latitude between locations may be the reason for that. Latitude correlated negatively with the treatability. Within the trees, the treatability of sapwood increased with distance from ground and with distance from heartwood border. A small, but significantly better treatability was found for kiln dried wood (60°C) compared to air dried wood (20°C).     

Effects of climate and site characteristics on Scots pine growth

Scots pine is a highly diverse species, extended across Europe from Scandinavia to Spain, Italy, Greece and Turkey. It is also a valuable species, used in many commercial monoculture plantations in Great Britain and particularly in Scotland. Because of the diversity of growing environments and its commercial importance, it is necessary to identify the combination of significant factors affecting the observed variability of growth. Temperature, mainly during the growing season, is quite commonly considered as the most important factor in knowledge-based or empirical models. However, in highly oceanic climates like that of Scotland, the impact of temperature may have a less significant impact on growth. Here we argue that other factors, such as incoming winter solar radiation, frost, drought and management also have a significant effect on the growth of Scots pine. In addition, we argue that the already developed Ecological Site Classification knowledge-based model, used as a forest management tool in Great Britain, should be updated to incorporate our findings. Furthermore, we discuss the need to include management impact and possibly more physiological based components in its growth modelling routines, as these would allow the introduction of the effect of winter solar radiation.     

Electrical transport of endogenous mineral ions in green sapwood ofPinus sylvestris L. (Scots pine)

Summary The relative migration of the major endogenous ions (K⁺, Ca²⁺ Mg²⁺, Na⁺, Cl^– in green sapwood ofPinus sylvestris L. was measured in a modified Hittorf transference cell. The transference numbers obtained gave the fractions of the current carried by these ions when an electric field was applied across the wood samples under the conditions used.Potassium and calcium ions were always found to be the main endogenous current carriers, followed by magnesium, sodium and chloride ions. No significant differences in transference number were found between wood stored under refrigeration or in a deep freeze, nor was there any effect on prior -irradiation. Fungal contamination in a few non-irradiated specimens led to lower transference numbers. Changes in moisture content from 86 to 141% produced no significant change but the results did depend on the tree from which the samples had been taken. A decrease in the length of the wood sample from 100 to 50 mm had little effect on the transference numbers of calcium ions but caused a decrease in those of potassium when larger quantities of electricity were passed. Transversely- and longitudinally-oriented wood samples, however, gave very similar results. Visual observation of the anode compartment indicated that the ions followed the path of least resistance between cathode and anode and that the current passed along the grain of the wood.Symbols c_i molar concentration of ion i - F Faraday's constant (96 494 C/mol) - I current - t time - t_i transference number of ion i (also shown as t(i) in tables) - V volume of electrode compartment - Z_i charge number of ion i The authors thank SERC and Rentokil PLC for the award of a CASE Research Studentship to P.J.S. and the Leverhulme Trust for the award of an Emeritus Fellowship to M.S.     

Electrical migration of exogenous mineral ions through green sapwood ofPinus sylvestris L. (Scots pine)

Summary The electrical migration was studied of several cations passing longitudinally through cylindrical samples of green sapwood ofPinus sylvestris L. under the influence of an applied electric field. This led to values for the hindered ionic conductances within the wood of the cations Li⁺, K⁺ and CU²⁺ which were compared with data obtained previously (Simons et al., 1998) for several endogenous cations. There was satisfactory agreement for the conductance of the potassium ion, the only one to be determined by both methods. Copper ions were found to possess a higher conductance within the wood than calcium or magnesium, a factor relevant to its use as a wood preservative. Visual observation of the location of the blue-green colouration produced in the wood by copper ions indicated that they migrated via longitudinal resin ducts and tracheids. Elution and transport experiments were also carried out with sapwood which had been flushed with water, Li₂SO₄ or CuSO₄ solution.Symbols E potential gradient - F Faraday's constant (96, 494 C/mol) - I current - L length of wood sample - M molarity (mol/dm³) - Q quantity of electricity - R electrical resistance - S Siemens (reciprocal ohm) - t time - u ionic mobility (velocity under unit potential gradient) - v ionic velocity - z charge number of ion - ionic conductance The authors thank SERC and Rentokil PLC for the award of a CASE Research Studentship to P.J.S. and the Leverhulme Trust for the award of an Emeritus Fellowship to M.S.     

Durability of thermally modified sapwood and heartwood of Scots pine and Norway spruce in the modified double layer test

In the present study, durability of untreated and thermally modified sapwood and heartwood of Scots pine and Norway spruce was examined using a modified double layer test. Base layer samples were partly on contact with ground where exposure conditions were harder than that in a double layer test above the ground. The base layer on ground contact gave results already after one year of exposure in Finnish climate, but the top layer of a double layer test element simulated more the situation of decking exposure.

Significant differences in durability and moisture content (MC) between the wood materials were detected after six years of exposure in the field. Thermally modified pine heartwood performed very well in all layers of the test element and only minor signs of decay were found in some of the base samples. Both sapwood and heartwood of thermally modified spruce were suffering only slight amounts of decay while thermally modified pine sapwood was slightly or moderately decayed. Untreated sapwood samples of pine and spruce were severely decayed or reached failure rating after six years in the field. Untreated heartwood samples performed clearly better. The highest MCs were measured from untreated and thermally modified pine samples. Thermal modification increased significantly the durability and decreased the MC values of all wood materials.     

Natural weathering of Scots pine (Pinus sylvestris L.) wood treated with epoxidized linseed oil and methyltriethoxysilane

In this study, the effect of natural weathering on the performance of Scots pine sapwood treated with epoxidized linseed oil (ELO) and methyltriethoxysilane (MTES) was investigated by measuring water uptake, colour, check propagation and chemical changes. Boards were impregnated in a pilot-scale autoclave under various conditions. After the treatments, pairs of samples were cut from the treated boards and exposed at 45° angle facing south for a long-term test of natural weathering above ground in Uppsala (Sweden). The effect of solar radiation and humidity on the colour changes, water uptake, check propagation and chemical alterations was assessed during 20 months of exposure. The obtained results can serve as indication for the viability of the treatments. Samples impregnated with low retentions of ELO showed similar performance regarding check propagation and moisture uptake as samples with higher retentions. No significant difference between these samples was found regarding colour change which is mainly caused by blue stain fungi on the surface. In opposite, samples treated with MTES exhibited no consistent water uptake and check propagation unproportioned to the applied retentions. The spectra of ELO- and MTES-treated wood after weathering showed a significant decrease of the peak at 1510 cm^?1 indicating delignification of wood surface caused by weathering.     

Quantifying the effect of pine mistletoe on the growth of Scots pine

Mistletoe infection results in substantial growth losses in mistletoe‐infected forests. This study reports and evaluates the results of retrospective analyses of radial growth of Scots pine (Pinus sylvestris) in relation to the level of infection of pine mistletoe (Viscum album ssp. austriacum). A total of 43 Scots pine trees were destructively sampled from different sites. Of these trees, 14 were uninfected and 29 were infected. Infection classes were determined using six‐class dwarf mistletoe rating system (DMRS). All needle and mistletoe biomass were removed completely and weighed for each sampled tree. Subsamples from needles and all mistletoe biomass were taken to the laboratory for oven‐dried weight determinations. Five‐cm‐thick wood discs were cut from the stem at the breast height (1.3 m) to determine annual basal area increment for the last 25 years. In addition to DMRS, new infection classes were created using mistletoe‐to‐needle biomass (MB/NB) ratio. The results showed that the radial growth losses could be as much as 41% to 64% at different infection levels. The rate of growth loss in relation to DMRS and MB/NB ratio was similar, but with a larger variability in DMRS values. The results showed that both DMRS rating and MB/NB ratio seem to be important for quantifying growth loss on Scots pine trees infected with mistletoe. The results of this study can also be invaluable in modelling the effects of mistletoe on the growth of Scots pine trees.