Concentration gradients of free sterols,steryl esters and lipid phosphorus in the trunkwood of Scot's pine (Pinus sylvestris L.)

The amounts of free sterols, steryl esters and lipid phosphorus were determined in the sapwood and heartwood of mature, and in the outer and inner sapwood of young Pinus sylvestris trees. In the mature trees (up to 70 years old) the heartwood contains significantly higher amounts of free sterols than the sapwood. No radial gradient can be demonstrated in the amounts of steryl esters. Lipids extracted from the sapwood contain higher amounts of phosphorus than those from the heartwood. Stems of young Pinus sylvestris trees (up to 13 years old) show in the inner sapwood higher amounts of both free sterols and steryl esters than the peripheral younger wood zone. The inner sapwood of the young stems shows slightly higher amounts of lipid phosphorus than the outer sapwood. The results indicate that Pinus sylvestris accumulates both free sterols and steryl esters in the stems at a very early stage of the life cycle. Sterol accumulation in the innermost parts of the stems seems not to depend on heartwood formation.     

Decay resistance of Togolese teak (Tectona grandis L.f) heartwood and relationship with colour

Togolese teak (Tectona grandis L.f) is highly resistant to pathogen attack, but variability in natural durability exists between trees of different ages, plantations and geographical zones. Therefore, further information concerning this parameter of wood quality is necessary; however, traditional testing methods are difficult and time-consuming to carry out. We tested the possibility of using colorimetry to determine durability in heartwood samples taken from a wide range of trees.Twelve hundred samples from 31 trees were exposed to four fungi: Pycnoporus sanguineus, Antrodia sp., Gloephylum trabeum, and Coriolus versicolor. Wood samples were grouped into three classes (inner, intermediate and outer heartwood). The colour parameters of each sample were then determined using the CIELAB (L^*, a^*, b^*) system and results correlated with the %mass loss of wood after fungal attack. Tests showed that Antrodia sp. and C. versicolor resulted in <20% mass loss, whereas all samples were rated as durable or highly durable with regard to P. sanguineus and G. trabeum. Inner heartwood was found to be the most resistant to pathogen attack and outer heartwood the least.Measurements of colour showed that heartwood was lightest nearest the pith and darkness and redness increased towards the outer heartwood. Regressions of lightness with %mass loss in the durability tests were always highly significant, whereas a^* and b^* were not always significantly regressed with %mass loss. Therefore, the use of colorimetry as a tool to estimate short-term natural durability both rapidly and cheaply could be considered in the case of plantation grown teak wood.     

Effect of age on the distribution of oil in Eastern redcedar tree segments

Eastern redcedar is widespread in the US and produces significant amount of biomass. Open-grown trees invade abandoned fields and compete with valuable forage species in pastures and rangelands. Value-added product development from redcedar is vital for management of eastern redcedar. Cedarwood oil is a valuable component which can be used for further value-added product development. This study examined the effect of age on the distribution of oil in redcedar tree segments. Trunks of eastern redcedar (Juniperus virginiana L.) trees at different stages of growth (26-63 years old) were divided into three sections (top, center and lower). Each section was fractionated separately into bark, heartwood and sapwood segments. Heartwood and sapwood samples from each tree section were analyzed for oil content and composition. A hydrodistillation method was used for oil extraction. Volatile components of tree segments were examined by using a Gas Chromatograph-headspace analysis technique. The heartwood of eastern redcedar contained significantly higher oil than sapwood. Older trees had more oil in the heartwood than younger trees. Both redcedar bark and leaves contained significantly lower oil content than the cedarwood. There were also significant differences in the oil composition of bark, leaves and wood fractions. Cedarwood oil extraction may benefit from prior separation of tree segments prior to oil extraction. However, the economic feasibility of separation prior to an extraction process needs to be further studied. Required extra capital investment and operating costs need to be examined, as well as whether sapwood is worth processing.     

Radial and vertical variation of wood nutrients in Bornean tropical forest trees

Nitrogen, phosphorus, potassium, calcium, and magnesium concentrations in woody tissue are poorly documented, but are necessary for understanding whole-tree nutrient use and storage. Here, we report how wood macronutrient concentrations vary radially and along the length of a tree for 10 tropical tree species in Sabah, Malaysia. Bark nutrient concentrations were consistently high: 2.9–13.7 times greater than heartwood depending on the nutrient. In contrast, within the wood both the radial (sapwood vs. heartwood) and vertical (trunk bottom vs. trunk middle) variation was modest. Higher concentrations in sapwood relative to heartwood provide empirical support for wood nutrient resorption during sapwood senescence. Dipterocarp species showed resorption rates of 25.3 ± 7.1% (nitrogen), 62.7 ± 11.9% (phosphorus), and 56.2 ± 12.5% (potassium), respectively, while non-dipterocarp species showed no evidence of nutrient resorption in wood. This suggests that while dipterocarps have lower wood nutrient concentrations, this family is able to compensate for this by using wood nutrient resorption as an efficient nutrient conservation mechanism. In contrast to other nutrients, calcium and magnesium tended to accumulate in heartwood. Wood density (WD) showed little vertical variation along the trunk. Across the species (WD range of 0.33 to 0.94 mg/cm³), WD was negatively correlated with wood P and K concentration and positively correlated with wood Ca concentration. As our study showed exceptionally high nutrient concentrations in the bark, debarking and leaving the bark of the harvested trees on site during logging operations could substantially contribute to maintaining nutrients within forest ecosystems.     

Variation of stilbene glucosides in bark extracts obtained from roots and stumps of Norway spruce (Picea abies [L.] Karst.)

Acetone-soluble compounds found in different root zones and stumps of Norway spruce (Picea abies [L.] Karst), which were grown on either peatland or a mineral soil site, were studied. Samples from stumps and roots of different sizes and ages were collected a day after the trees were felled. The wood and bark of stumps and three zones of the roots were separated and extracted with acetone in an ultrasonic bath. Extracts were silylated and analysed by gas chromatography–mass spectrometry. The stilbene glucosides astringin and isorhapontin were major compounds in the spruce bark samples. The resveratrol glucoside piceid and the flavonoid catechin were also extracted from spruce bark. We also found the lignan hydroxymatairesinol in some wood extracts. Total concentrations of stilbene glucosides in bark of stumps and different root zones varied between 0.53 and 8.29 % (w/w, dry weight) with isorhapontin being the major compound. Isorhapontin concentrations were highest in the spruce samples grown on mineral soil. The bark of the roots close to the stem is a rich source of stilbenes for commercial utilisation.     

Cellular level observation of water loss and the refilling of tracheids in the xylem of Cryptomeria japonica during heartwood formation

The mechanism of heartwood formation in Cryptomeria japonica D. Don has long been studied since heartwood formation is a fundamental physiological feature of trees. In this study, the water distribution in the xylem of C. japonica was investigated at the cellular level to reveal the role of water distribution in the xylem during heartwood formation. Samples were taken from different heights of each trunk, in which the phases of heartwood formation differed. These were designated as SIH, which consisted of sapwood, intermediate wood, and heartwood; SI, which consisted of sapwood and intermediate wood but no heartwood; and S-all, which consisted entirely of sapwood. Cryo-scanning electron microscopic observations of the heartwood-formed (SIH) and non-heartwood-formed (SI and S-all) xylem revealed different patterns of water distribution changes in tracheids between the latewood and earlywood. In the latewood, almost all tracheids were filled with water in all areas from the sapwood to the heartwood (98–100% of tracheids had water in their lumina). In the earlywood, however, the water distribution differed between the sapwood (95–99%), intermediate wood (7–12%), and heartwood (4–100%). Many of the tracheids in the xylem, where the sapwood changed to intermediate wood lost water. In the heartwood, some tracheids remained empty, while others were refilled with water. These results suggest that the water distribution changes in individual tracheids are closely related to heartwood formation. Water loss from tracheids may be an important factor inducing heartwood formation in the xylem of C. japonica.     

Natural wood colouring process in Juglans sp. (J. nigra, J. regia and hybrid J. nigra 23 ×J. regia) depends on native phenolic compounds accumulated in the transition zone between sapwood and heartwood

 Radial distribution of soluble phenolics was investigated at different heights in stems of Juglans nigra, J. regia and hybrids J. nigra 23 × J. regia. Four major phenolic compounds were studied: hydrojuglone glucoside (HJG), quercitrin (QUER) and two unknown compounds characterized as two ellagic acid derivatives E1 and E2. HJG and E1 content increased gradually in the sapwood, peaked in the sapwood-heartwood transition zone, and decreased drastically in the heartwood. QUER was accumulated preferentially around the transition zone, and its content was relatively low in the outer part of the sapwood and in the inner part of the heartwood. E2 content was low in the sapwood and increased in the heartwood. The heartwood formation was marked by the accumulation of new soluble compounds. The relationship between wood extractives and wood colour were evaluated and discussed. HJG was considered to be a major precursor of heartwood colour providing chromophores through hydrolysis (deglucosylation), oxidation and polymerization processes. Received: 2 September 1997 / Accepted: 23 November 1997     

Genetic analysis of enhanced-axillary-branching-derived Eucalyptus tereticornis Smith and E. camaldulensis Dehn. plants

In a culture method for enhanced axillary branching functional plants of Eucalyptus tereticornis and E. camaldulensis are efficiently regenerated. To assess the genetic integrity among the regenerants, we employed multiple analytical tools including cytochemical and molecular assays. The 2C DNA amounts were estimated in the meristematic zones of root and shoot tips of 250 micropropagated plants, collected at various cycles of tissue culture from multiplication to field transfer, and compared to the corresponding mother plants. The culture conditions did not induce amplification or deletion of DNA sequences, nor were there drastic change(s) in chromosome number, since all the micropropagated plants of E. tereticornis (1.2 pg) and E. camaldulensis (1.4 pg) maintained the same DNA amounts as the mother plant. Total DNA of 46 micropropagated and mother plants digested with eight restriction enzymes and hybridized to 13 nuclear, mitochondrial, and synthetic oligonucleotide DNA probes yielded 82 bands. Hybridization patterns indicated that the variation observed was minor. To further confirm the genetic fidelity, 12 arbitrary 10-base primers and six synthetic oligonucleotide sequences, successfully used to amplify genomic DNA from in vivo and in vitro materials, produced 133 fragments that were monomorphic across the plants tested. The present results demonstrate that enhanced-axillary-branching culture of mature trees could be utilized commercially for mass clonal propagation of these two important Eucalyptus species that have been recalcitrant to vegetative propagation. The results also provide novel insights into the genetic differences between E. tereticornis and E. camaldulensis. Received: 8 October 1996 / Revision received: 22 July 1997 / Accepted: 30 July 1997     

Is oxygen involved in beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis>) red heartwood formation?

European beech (Fagus sylvatica) facultatively develops red heartwood, which decreases the value of its timber and is difficult to predict in standing trees. According to current theory, the absence of oxygen prevents discolouration in the wood of uninjured trees, and red heartwood forms when oxygen enters the stem through injuries. This theory requires that oxygen concentrations in uncoloured wood are generally very low, and that oxygen can diffuse several metres in the centre of a stem, bypassing the respiring sapwood. Oxygen concentrations measured at different depth in stems with and without red heartwood varied strongly and were generally depleted relative to the air, but rarely close to 0. Concentrations in red heartwood were somewhat, though not significantly higher than in the inner wood of trees without red heartwood. The colour of wood exposed to different oxygen concentrations changed strongly at higher concentrations, but concentrations in standing stems are generally high enough for discolouration. Model calculations suggested that only massive injuries that kill most sapwood at an entry point would allow high amounts of oxygen to penetrate to the core, in which case it may diffuse several metres in the axial direction without being consumed by respiring sapwood. However, given the relatively high diffusion in axial direction, oxygen should spread within a few days, not several years as the development of red heartwood appears to take. These measurements and calculations suggested that, while oxygen is required for beech red heartwood discoloration, it is not the only factor involved but could act by affecting the activity of micro-organisms.     

Variation of non-structural carbohydrates in silver birch (Betula pendula Roth) wood

Non-structural carbohydrates in silver birch (Betula pendula Roth) wood were analysed in a 7-year-old clone and in five mature stems. The analysis was conducted to obtain more detailed information on seasonal fluctuation of these components and of the tree-to-tree variation and within stem variation. The sugars were analysed by GLC-MS. The smallest total soluble sugar amounts (consisting of sucrose, fructose, glucose, raffinose and myo-inositol) in young trees were measured during mid-summer (ca. 0.3%) and the largest while in dormancy (ca. 1.6% on wood dry weight basis). Raffinose was detected in autumn as a minor component. The proportion of monosaccharides and the amount of myo-inositol were largest during growth. Compared to other studies silver birch showed more evident seasonal fluctuation in soluble sugars than evergreen tree species. The sugar amount in mature stems was approximately at the same level as in young trees that had the same felling time. Tree-to-tree variation in the non-structural carbohydrates in the mature wood was fairly large. However, the amount of total soluble sugars, sucrose and glucose showed significant variation within the stem. The amount of these sugars was largest in samples that were taken close to the cambium. Starch was also detected close to pith. According to the heartwood definition and starch measurement results in this paper, it could be stated that silver birch does not form heartwood.     

Wood identification with PCR targeting noncoding chloroplast DNA

Wood identification is extremely important in the modern forest industry. It also has significant applications in forensics, as well as in archeology and ecological research. In this study, five universal primer pairs amplifying chloroplast noncoding sequences of 300–1,200 bp were designed. Sequencing these amplicons in combination can lead to reliable identification of logs and wood products to cultivar, ecotype, or even the falling population. These primer pairs work on both gymnosperms and angiosperm trees. They also are potentially applicable to accurately identify shrubs and herbaceous species. In addition, a wood DNA purification method is proposed in which N-phenacylthiazolium bromide (PTB) is used to increase the quality and quantity of extracted DNA. This method was first validated using air-dried timber disks from three different tree species that were felled 4 years ago. The sapwood and outer heartwood provided the best locations for DNA extraction. The method was also successfully applied to extract DNA from the recalcitrant processed white oak wood, randomly selected staves of wine barrels. The single nucleotide polymorphism detected on the oak DNA sequences showed correlation to their geographical origins.     

Secondary metabolites and nutrients explain fungal community composition in aspen wood

Fungi are the main decomposers of litter and wood, driving carbon and nutrient cycles. Despite a large number of studies, fungal community composition is remarkably difficult to predict. In the present study, we explore the importance of secondary metabolites and nutrient content in wood and bark as determinants of fungal community composition. We used aspen (Populus tremula) logs of similar size, from one location, and measured concentrations of carbon, nitrogen and secondary metabolites in bark and wood sampled shortly after felling. Fungal DNA was extracted from logs directly after felling and after two seasons of decomposition, and the fungal communities were assessed using DNA-metabarcoding. Concentrations of metabolites varied considerably between individual trees, and we also observed significant differences within single trees. Plant metabolites and nitrogen concentrations significantly affected fungal community composition. For the overall fungal communities and for wood saprotrophic fungi, the explanatory power of wood and bark metabolites was highest in logs decomposed over two seasons. In recently felled trees however, concentration of metabolites had a stronger effect on plant pathogens and endophytes. We conclude that secondary metabolites represent an overlooked, but important niche dimension for fungal communities in both functional sapwood and dead wood.     

Spatial Patterns in Hyphal Growth and Substrate Exploitation within Norway Spruce Stems Colonized by the Pathogenic White-Rot Fungus Heterobasidion parviporum

In Norway spruce, a fungistatic reaction zone with a high pH and enrichment of phenolics is formed in the sapwood facing heartwood colonized by the white-rot fungus Heterobasidion parviporum. Fungal penetration of the reaction zone eventually results in expansion of this xylem defense. To obtain information about mechanisms operating upon heartwood and reaction zone colonization by the pathogen, hyphal growth and wood degradation were investigated using real-time PCR, microscopy, and comparative wood density analysis of naturally colonized trees with extensive stem decay. The hyphae associated with delignified wood at stump level were devoid of any extracellular matrix, whereas incipient decay at the top of decay columns was characterized by a carbohydrate-rich hyphal sheath attaching hyphae to tracheid walls. The amount of pathogen DNA peaked in aniline wood, a narrow darkened tissue at the colony border apparently representing a compromised region of the reaction zone. Vigorous production of pathogen conidiophores occurred in this region. Colonization of aniline wood was characterized by hyphal growth within polyphenolic lumen deposits in tracheids and rays, and the hyphae were fully encased in a carbohydrate-rich extracellular matrix. Together, these data indicate that the interaction of the fungus with the reaction zone involves a local concentration of fungal biomass that forms an efficient translocation channel for nutrients. Finally, the enhanced production of the hyphal sheath may be instrumental in lateral expansion of the decay column beyond the reaction zone boundary.To grow to great heights, trees continually replace their water- and nutrient-conducting elements. Older elements, such as the heartwood that is formed in many trees, gradually become nonconductive. In contrast to the living sapwood, heartwood lacks active defense mechanisms against microbes. However, lignin, the polymer coating cell wall polysaccharides, is highly resistant to microbial degradation. In fact, white-rot fungi, besides having evolved the ability to tolerate or detoxify the secondary metabolites accumulating in heartwood, are the only organisms capable of efficiently degrading lignin. Following establishment in the heartwood of living trees, the colonies of pathogenic white-rot fungi expand and eventually also threaten the conductive sapwood.The white-rot fungus Heterobasidion annosum sensu lato, composed of three species with overlapping geographic distributions and host ranges in Europe (23), is the most important pathogen of Norway spruce (Picea abies L. Karst) in boreal forests. Primary infection of Norway spruce stands by H. annosum sensu lato takes place through fresh thinning stumps or wounds on roots and at the base of the stem. Basidiospores landing on these entrance points give rise to mycelia which colonize the root systems, and eventually the fungus spreads into the stem heartwood. At sites infested with Heterobasidion parviporum, a species primarily restricted to Norway spruce, roots of saplings can become infected by the fungus after around 10 years of growth (25). Stem colonization usually initiates only after the heartwood has started to develop, which in Norway spruce takes place in trees 25 to 40 years old (17). Due to relatively rapid axial spread within heartwood, the decay column caused by H. annosum sensu lato often is up to 10 m high in the stems of mature Norway spruce trees.In response to sapwood challenge by an expanding heartwood-based colony of H. annosum sensu lato, Norway spruce forms a so-called reaction zone (RZ) in the border area between healthy sapwood and colonized heartwood. This xylem defense is characterized by high pH due to increased carbonate content and enrichment of phenolic compounds, particularly lignans, some of which have shown antifungal properties in bioassays (14, 30, 31). Although several wood decay fungi are able to eventually penetrate the RZ regions formed in trees, the strategies employed by fungi to breach these unique defense barriers are poorly understood (24). The purpose of this study was to obtain information about the mechanisms operating in heartwood colonization and expansion of the decay column via penetration of the RZ. To do this, we examined spatial growth of H. parviporum and the associated substrate exploitation patterns within naturally colonized mature stems of Norway spruce.     

Effects of flooding on wood and bark anatomy of four species in a mangrove forest community

Variation in the wood and bark anatomy of the dominant species of a mangrove forest community in Mexico was evaluated in relation to some environmental factors, and their physiological adaptations to salinity and flooding period are discussed. The forest is characterized by three zones according to the presence of dominant tree species and flooding periodicity. Vessel arrangement and wood and bark ray height are strongly associated with flooding zones where trees are growing. Variance analyses revealed significant differences among zones for these anatomical characteristics. Soil texture and water salinity were the most useful parameters for the prediction of values of anatomical characteristics. More abundant vessels in radial multiples in a shorter flooding period suggest a functional advantage of multiple vessel groups. Taller wood and bark rays in response to prolonged flooding period can be attributed to anoxic conditions. Among zones, significant differences in the vulnerability index of the species were detected, but not with respect to relative conductivity. Significant differences among zones exist for wood and bark characteristics involved in vertical and horizontal water transport, photosynthates and gas exchange.     

Dependence of the cellulosolytic activity in the lichen <Emphasis Type="Italic">Hypogymnia physodes</Emphasis> (L.) Nyl. on the substrate

Samples of the lichen H. physodes were collected from bark of living trees (pine, spruce, birch, alder, rowan, and willow); from the wood of these trees and of juniper; from bark of dead spruce, alder, and rowan trees; and from the moss Hypnum pallescens. Thalli of this lichen were placed onto medium with carboxylmethyl cellulose (CMC) (water being used as a control). Output of sugars was determined using the Nelson-Somogyi technique. Cellulosolytic activity of samples from the bark of pine and birch was higher than that of samples from the bark of spruce. In thalli of the lichen from wood, from moss, and from bark of living alder and rowan trees, the output of sugars on the medium with CMC was similar to that in the control. The cellulosolytic activity was revealed in samples from the lichen from bark of dead rowan and alder trees. In the lichen from spruce bark, the output of sugars on the medium with CMC was higher in samples from dead trees in comparison with living trees. The results are discussed.     

Direct amplification of minisatellite-region DNA with VNTR core sequences in the genus Oryza

 A polymerase chain reaction (PCR) application, involving the directed amplification of minisatellite-region DNA (DAMD) with several minisatellite core sequences as primers, was used to detect genetic variation in 17 species of the genus Oryza and several rice cultivars (O. sativa L.). The electrophoretic analysis of DAMD-PCR products showed high levels of variation between different species and little variation between different cultivars of O. sativa. Polymorphisms were also found between accessions within a species, and between individual plants within an accession of several wild species. The DAMD-PCR yielded genome-specific banding patterns for the species studied. Several DAMD-PCR-generated DNA fragments were cloned and characterized. One clone was capable of detecting multiple fragments and revealed individual-specific hybridization banding patterns using genomic DNA from wild species as well as rice cultivars. A second clone detected only a single polymorphic locus, while a third clone expressed a strong genome specificity by Southern analysis. The results demonstrated that DAMD-PCR is potentially useful for species and genome identification in Oryza. The DAMD-PCR technique also allows for the isolation of informative molecular probes to be utilized in DNA fingerprinting and genome identification in rice. Received: 1 October 1996 / Accepted: 25 April 1997     

Formation of heartwood substances in the stemwood of Robinia pseudoacacia L. II. Distribution of nonstructural carbohydrates and wood extractives across the trunk

Summary The distributions of reserve carbohydrates and of three dominant heartwood extractives were determined in the trunkwood of Robinia pseudoacacia L. The trees were cut at different times of the year (September, November, January, and April). With the exception of the tree felled in January, all trunks exhibited highest contents of nonstructural storage carbohydrates (glucose, fructose, sucrose, and starch) in the youngest, outermost sapwood zone. With increasing depth of the trunk, the levels of carbohydrates decreased. At the sapwood-heartwood transition zone, only trace amounts of nonstructural carbohydrates were present. The heartwood itself contained no storage material. The wood zones of different ages of the trees cut in September, November, and January exhibited glucose/fructose ratios of approximately 1. In April, however, there was a shift to glucose. In the youngest sapwood the amounts of soluble sugars were higher in the earlythan in the latewood. Older zones of the sapwood and the sap-wood-heartwood transition zone showed the opposite behaviour. Three main wood extractives of Robinia were characterized and quantified: the flavanonol dihydrorobinetin (DHR), the flavonol robinetin (ROB) and a hydroxycinnamic acid derivative (HCA). Only DHR was present — in very low amounts — in the younger sapwood of all trunks investigated. Higher amounts (>1 mol/g dry weight) of this compound and the HCA were present in the sapwood-heartwood transition zone. DHR augmented within the heartwood up to a more or less constant level. HCA increased towards the heartwood and decreased again in the inner heartwood parts. ROB appeared in the innermost parts of the sapwood-heartwood transition zone and reached maximum values in older parts of the heart-wood. The results indicate that starch is hydrolyzed at the sapwood-heartwood boundary and thus represents a primary major source of hydroxycinnamic acid and flavonoid synthesis.Dedicated to Prof. Meinhart H. Zenk on the occasion of his 60th birthday     

Mechanical Properties of Black Locust (Robinia pseudoacacia L.) Wood. Size- and Age-dependent Variations in Sap- and Heartwood

Variations in the density and stiffness (Young's elastic modulus)of fresh wood samples drawn from different parts of the threemain trunks of a 32-year-old black locust tree,Robinia pseudoacacia(measuring 19.8 m at its highest point), were studied to determinewhether tree ontogeny can achieve a constant safety factor againstmechanical failure. Based on the properties of isolated woodsamples, the fresh density of sapwood decreased along radialtransects from bark to pith, while that of progressively olderheartwood samples increased, on average, towards the centreof each of the three trunks. Along the same radial transects,the Young's elastic modulus of sap- and heartwood increased.In terms of longitudinal changes in wood properties, mean woodmoduli (averages of sap- and heartwood samples) increased, onaverage, towards the base of each of the three trunks of thetree. However, the mean fresh densities of wood samples increasedtowards the top and the bottom of each trunk and were lowestroughly near trunk mid-length. The mean density-specific stiffness(the quotient of Young's modulus and fresh density) of woodwas thus lower toward the top and the bottom of the trunks andhighest near trunk mid-length. Mean values of fresh wood density-specificstiffness were used to estimate the critical buckling heightsfor sections of the trunks differing in diameter and age. Theseestimates indicated that ontogenetic variation in the physicalproperties and relative amounts of sap- and heartwood in trunkscould maintain a constant factor of safety (approximately equalto 2) as a sapling grows in height and girth into a mature tree.This expectation was supported by data from 16 black locusttrees differing in height and diameter at breast height (DBH). Wood; elastic properties; tree height; biomechanics     

Attributes of trees used by nesting and foraging woodpeckers (Aves: Picidae) in an area with old pollarded Oaks (Quercus spp.) in the Taurus Mountains,Turkey

We used three woodpecker species as umbrella species for old deciduous forests, and analysed their preferences in an area with old pollarded oaks in the Taurus Mountains, Turkey. Using plot inventories, we physically characterised trees utilised for nesting and foraging amongst woodpeckers in general and the Middle Spotted Woodpecker (Leiopicus medius) in particular. Trees more frequently visited by foraging woodpeckers differed from randomly chosen trees by being taller, having a larger circumference, greater bark furrow depth and shorter distance to neighbouring trees. Nesting trees were taller, had a higher proportion of dead wood but a lower surface area of natural cavities. Our results suggest that the woodpeckers in the study area rely upon woodlands containing mature trees, thus have the potential to function as suitable umbrella species’ to highlight the conservation value of oak forest habitats in southern Turkey.     

Resistance of Scots pine wood to Brown-rot fungi after long-term forest fertilization

The susceptibility of Scots pine (Pinus sylvestris L.) sap- and heartwood against the wood decaying brown-rot fungus (Coniophora puteana) was investigated after long-term forest fertilization at three different sites in central Finland. Different wood properties: wood extractives, wood chemistry, and wood anatomy were used to explain sap- and heartwood decay. Scots pine sapwood was more susceptible to decay than its heartwood. In one site, sapwood seemed to be more resistant to wood decay after forest fertilization whereas the susceptibility of heartwood increased. Significant changes in the sapwood chemistry were found between treatment and sites, however, no relationship between wood chemistry and wood decay was observed in the factor analysis. The results of this study show that there was an inconsistent relationship between decay susceptibility and fertilization and the measured physical and chemical attributes of the wood were not consistently correlated with the decay rate.