Ring Wood Research Articles

Growth and chemical composition of silver birch: Comparative study between Lithuania and Romania

The effects of different climatic conditions on growth and chemical composition of Betula pendula in geographically different European regions, Lithuania and Romania, were compared. Birch species in the entire area have a wide natural distribution, but B. pendula is commercially more important in Lithuania than in Romania. Here we evaluated tree ring width, wood density and foliar chemical composition of mature birch trees in two European regions. Trees at the Lithuanian sites had greater radial growth and wood density with no clear changes in foliar chemistry than those at the Romanian sites. Mean wood density was 600–700 kg m−3 at Lithuanian and 350–450 kg m−3 at Romanian sites. Mean width of wood ring, earlywood and latewood for Lithuanian birch trees were several times higher than the means for Romanian birch trees. We hypothesized that the main differences in birch radial growth and wood density were due to the different climatic conditions in the studied regions. Ca, K and Mg concentrations were significantly higher and Fe and Mn were lower in the birch foliage at the Lithuanian sites compared those at the Romanian sites. Overall assessment of growth showed that silver birch cultivation is more appropriate for colder climate regions and that birch growth may change in the context of a warming climate.

Oldest Jurassic wood with Gondwanan affinities from the Middle Jurassic of Tibetan Plateau and its paleoclimatological and paleoecological significance

Jurassic flora of the Tibetan Plateau is poorly known, with limited fossil records. The paleobiogeography of terrestrial biota is, however, one of the major evidences to reconstruct the intricate paleogeography of an area. Well-preserved fossil wood is described from the Middle Jurassic Xiali Formation (Callovian) in the South Qiangtang terrane of the Tibetan Plateau, SW China. The wood specimen is a well-preserved secondary xylem without growth rings. Bordered pits on the radial tracheid walls are mostly uniseriate distant, locally contiguous. Cross-fields have 1–2 large oopores. A systematic study indicates that the current fossil wood represents a new species, Circoporoxylon tibetense sp. nov. This is the earliest Laurasian data for the genus Circoporoxylon, which has a Gondwanan origin and subsequently became common in Laurasia during the Cretaceous. The present new finding indicates that Circoporoxylon might have reached the Laurasia via a Tibetan terrane. The presence of fungal remains and wood rotting structures resembling the extant white-rot testifies for the plant–fungal interaction in the Callovian. The absence of growth rings in Circoporoxylon wood and the absence of gypsum layers in the South Qiangtang terrane, together with the widely occurrence of gypsum layers in the North Qiangtang terrane, suggests the South Qiangtang terrane might be wetter than the latter during the Callovian age. The paleogeomorphological highlands of Central Uplift were most likely the boundary between the two. This paleoclimate zonation implies that the Permian to Mesozoic megamonsoon of the supercontinent Pangaea might have terminated in the northern of Paleo-Tethys before the Callovian.

Climate warming differently affects Larix decidua ring formation at each end of a French Alps elevational gradient

The ongoing global warming tends to reduce Larix decidua radial growth and ring wood density at the bottom of an elevational gradient in the French Alps, while it has a less marked effect at the top. The ongoing climate warming affects most tree species across their biogeographic distribution range. The bottom and the top of an elevational gradient are appropriate environments to observe the effect of climate warming in contrasted temperature conditions. To retrospectively study the effect of the ongoing climate warming on Larix decidua trees located in warm and cold conditions, i.e., at the bottom (1200 m) and the top (2300 m) of an elevational gradient, respectively. Dendroecological analysis of two groups of Larix decidua trees located at very low (1200 m) and very high (2300 m) elevations. Construction of climatic response curves for annual ring variables. Decomposition of the variance of the response models into their high and low frequency components. At Briancon, in the French Alps, the increase of the daily maximum temperature during the last 50 years is already almost 3 °C for the March–October period. The results reveal contrasted behaviors at both ends of the investigated elevational gradient. Basal area increment, ring width, and their earlywood and latewood components increase or level off at the top of the gradient, while they all strongly decrease at the bottom. At the bottom, the low frequency warming effect explains the recent ring width decrease, with no influence of the high frequency temperature variation. At the top, both the low frequency warming effect and the high frequency temperature effect explain each about half of the ring width variation encompassed by the model. Latewood density displays the same trend as ring width, while earlywood density decreases at both ends of the gradient. Such opposed trends of the radial growth time trends between the top (2300 m) and the bottom (1200 m) of the gradient reflects the respectively favorable and unfavorable effects of climate warming at such ends of this Larix decidua elevational gradient. We propose that the strong ring width decrease observed at the warmer bottom announces a coming dieback. The corresponding wood density decrease will affect wood hydraulic properties in a way that is unclear.

Mummified fossil of Keteleeria from the Late Pleistocene of Maoming Basin, South China, and its phytogeographical and paleoecological implications

AbstractKeteleeria is a small genus of Pinaceae now mainly restricted to eastern Asia. Although this genus has been documented with a wide distribution in the geologic record of Europe, North America, and Asia, its history in low‐latitude areas (including South China) has remained obscure. In this paper, a fossil wood of Keteleeria sp. is described from the Late Pleistocene (29–27 ka BP) of the Maoming Basin, South China. This wood is the most ancient megafossil evidence of Keteleeria within the modern distribution area of this genus. The fossil records of Keteleeria suggests that this thermophyllous genus migrated into South China by the Middle Pleistocene escaping from glacial cooling and became widespread over this region in the Late Pleistocene beginning from the interglacial stage preceding the Last Glacial Maximum. The analysis of growth rings in the fossil wood and its comparison with those of modern Keteleeria davidiana (Bertrand) Beissner indicates that in the Late Pleistocene of Maoming Basin (29–27 ka BP) there was a humid climate with less pronounced seasonality of precipitation than that seen in the subtropical monsoonal climate of modern northeastern Vietnam. Apparently, the Maoming Basin was influenced by interglacial regime with summer–monsoon circulation. The previously proposed method to distinguish between evergreen and deciduous conifers based on growth ring anatomy, is not reliable because of the wide variance and ambiguity in its results.

Long-term phytoremediating abilities of Dalbergia sissoo Roxb. (Fabaceae)

The boom of tanneries in north India has converted the river Ganga into a waste dumping stream. The tanneries discharge their heavy metal-rich effluents into the river. Tissues of two-year-old tree saplings of Dalbergia sissoo, soil sediments and river water samples were collected from three sites along the river Ganga at Jajmau, Kanpur. Site-1 was located 1 km upstream from the point of discharge of the effluents of the tanneries, Site-2 was close to the source point, and Site-3 was about 1 km downstream from the source point. Accumulation of Cu, Cr and Ni in leaves, bark, wood growth rings, soil sediments and water samples was estimated using an atomic absorption spectrophotometer. The tissues of the two-year-old wood growth rings of D. sissoo accumulated large amounts of Cr, Cu and Ni. The Cr concentration in leaves, bark and wood rings had a strong, positive and linear correlation (r2) with the Cr concentration in soil sediments. The bio-concentration factors (BCFs) of Cr, Cu and Ni were higher than 1 in the wood, bark and leaves at all three selected sites, indicating the strong phytoremediating ability of the tree. The uptake of Cr and Ni was consistent in the bark and wood growth rings of two successive years. Owing to the strong uptake and accumulating abilities of Cr, Cu and Ni as evident from high BCF values and high biomass, we propose D. sissoo as a suitable species for phytoremediation throughout its range of distribution in Africa, Asia and the Americas.

Intra-Ring Variations and Interrelationships for Selected Wood Anatomical and Physical Properties of Thuja Occidentalis L.

Intra-ring variation in wood density and tracheid anatomical properties and wood property interrelationships were investigated in Thuja occidentalis L. Samples were taken from three stands in Abitibi–Témiscamingue, Quebec, Canada. The structure of T. occidentalis wood is simple, homogeneous and uniform, which is desirable for wooden structures that require wood uniformity. From early- to latewood, cell and lumen diameter decreased, while cell wall thickness increased. These changes led to an increase of the cell wall proportion. Wood ring density and width interrelationships were weaker in mature wood compared to juvenile wood. Earlywood density is the more important in determining mature wood density than latewood density and proportion. Earlywood density explains 92% and 89% of the variation in juvenile and mature wood density, respectively. The negative relationship between ring density and width, although significant, was low and tends to weaken with increasing tree age, thus providing the opportunity for silvicultural practices to improve both growth and wood density. Ring width was positively and strongly correlated to early- and latewood width, but negatively correlated to tracheid length and latewood proportion. Accordingly, increases in ring width produce smaller tracheids and wider earlywood without a corresponding increase in latewood. Practical implications of the results are discussed.

A biography and obituary of William G. Chaloner FRS (1928–2016)

William G. (‘Bill’) Chaloner FRS (1928–2016) was one of the world’s leading palaeobotanists and palynologists. He developed a love of natural science at school which led to a penchant for palaeobotany at university. Bill graduated in 1950 from the University of Reading, and remained there for his PhD, supervised by Tom Harris, on the spores of Carboniferous lycopods. After completing his PhD in 1953, Bill undertook a postdoctoral fellowship in the USA. He returned to the UK and, in 1956, began a long and distinguished academic career at four colleges of the University of London. His first position was at University College London, where he continued to work on Paleozoic palaeobotany and palynology. His 1958 paper on the effects of fluctuating sea levels on Carboniferous pollen-spore assemblages proved highly influential. Bill moved to a Chair at Birkbeck College in 1972, began to use the scanning electron microscope and was elected a Fellow of The Royal Society in 1976. He is the only pre-Quaternary palynologist to have been given the latter honour. In 1979, Bill was appointed to the Chair of Botany at Bedford College where he began to apply plant fossil evidence to general scientific problems. He began to work on arthropod–plant interactions, fossil charcoal and growth rings in wood. Bill was awarded the Medal for Scientific Excellence by the American Association of Stratigraphic Palynologists in 1984. Bedford College and Royal Holloway College merged in 1985, and Bill moved to the amalgamated institution. Bill continued to investigate very diverse topics, and added the analysis of leaf stomata, global environmental change and molecular palaeontology to his portfolio. Following retirement in 1994, Bill continued his research and teaching at Royal Holloway, University of London. His final paper was published in 2016, bringing to an end a research career of 66 years.

Evaluation of the Effect of Moisture Content in the Wood Sample Structure on the Quality of Tomographic X-Ray Studies of Tree Rings of Stem Wood

For the first time, the effect of moisture content in the structure of wood samples on the quality of the results of the study of their internal structure using high-resolution X-ray computer tomography is considered. The tomographic method for determining the internal distribution of the structure and density of tree rings of stem wood can be used to solve problems in the field of dendroclimatology and biometeorology.

Deciphering Hybrid Larch Reaction Norms Using Random Regression.

The link between phenotypic plasticity and heterosis is a broad fundamental question, with stakes in breeding. We report a case-study evaluating temporal series of wood ring traits of hybrid larch (Larix decidua × L. kaempferi and reciprocal) in relation to soil water availability. Growth rings record the tree plastic responses to past environmental conditions, and we used random regressions to estimate the reaction norms of ring width and wood density with respect to water availability. We investigated the role of phenotypic plasticity on the construction of hybrid larch heterosis and on the expression of its quantitative genetic parameters. The data came from an intra-/interspecific diallel mating design between both parental species. Progenies were grown in two environmentally contrasted sites, in France. Ring width plasticity with respect to water availability was confirmed, as all three taxa produced narrower rings under the lowest water availability. Hybrid larch appeared to be the most plastic taxon as its superiority over its parental species increased with increasing water availability. Despite the low heritabilities of the investigated traits, we found that the expression of a reliable negative correlation between them was conditional to the water availability environment. Finally, by means of a complementary simulation, we demonstrated that random regression can be applied to model the reaction norms of non-repeated records of phenotypic plasticity bound by a family structure. Random regression is a powerful tool for the modeling of reaction norms in various contexts, especially perennial species.

RADIAL GROWTH DYNAMICS OF Khaya ivorensis TREES FROM EXPERIMENTAL PLANTATION

ABSTRACT The objective of this study was to characterize the formation of growth rings in Khaya ivorensis wood, as well as to analyze the variation in the morphology of the vessel elements, aiming to understand the growth of this species in experimental plantations. Disks from the bases of five trees were collected, and after polishing the cross-section, demarcation of the growth rings limits was carried out. The anatomical study of the wood was conducted with the purpose of characterizing the rings, and their width was measured by means of scanned images of the disks. A historical series of data was obtained concerning the diameter of the trees to establish a correlation with the width of the rings measured over the years. The growth rings limits of African mahogany wood are demarcated by a thin layer of marginal parenchyma, and the presence of false rings has been observed. Significant annual growth correlation of 0.62 was observed among the trees, being the radial increment of irregular wood in the first years (wide and narrow rings), and highlighting the 3rd and 11th year of growth in which the largest increases were observed due to a biological adaptation tendency to the environment and the occurrence of thinning carried out in the planting area, respectively.

Effects of Vegetation Management on Wood Properties and Plant Water Relations of Four Conifer Species in the Pacific Northwest of the USA

In plantation forests, competition from unwanted vegetation may reduce survival and negatively impact tree growth. The goal of this study was to examine the influence of vegetation management treatments on plant water relations and wood properties. Control trees (no treatment) were compared to trees subjected to post-planting competing vegetation control for five consecutive years after planting. Four conifer species (Douglas-fir, western hemlock, western redcedar, and grand fir) were studied on two different sites in western Oregon, USA. Carbon isotope (13C) analysis was used to study intrinsic water use efficiency (iWUE) and X-ray densitometry was used to measure specific gravity, ring width, and latewood percent. We found a significant interaction between vegetation management treatment and wood ring (growing season) in iWUE for Douglas-fir. There was little effect of vegetation management treatment on ring specific gravity for all species. Only western redcedar growing at a central Coast Range site showed increased ring specific gravity under sustained competing vegetation control. When growing under conditions of sustained control of competing vegetation, western redcedar at a central Coast Range site had a significant increase in earlywood specific gravity, while Douglas-fir at a Cascade Foothills site had a significant decrease in latewood specific gravity. Western redcedar and grand fir had a significant interaction-effect on its latewood percentage, with treatment trees having a higher latewood percentage than control trees after ring 8. Further, Douglas-fir and western hemlock had a significant increase in ring, earlywood, and latewood area with treatment, and grand fir had a significant interaction-effect of treatment × ring for ring, earlywood, and latewood area. This study indicates that, for conifer trees growing under sustained vegetation control, growth gains could be achieved without compromising wood properties. However, if harvested at a target diameter, these trees will have a larger proportion of low quality corewood compared to trees from conventionally managed stands.

Prediction of wood surface discoloration for applications in the field of architecture

Semitransparently coated wooden building elements such as facades and windows undergo discolouration during exposure to sunlight, depending on the environmental conditions and protective properties of the coatings. The present paper aims at the development of numerical prediction models of photo-induced discolouration as a basis for texture synthesis for CAD applications. Wood samples of European larch and Norway spruce were coated with several (semi-) transparent coatings with varying colours and dry film thicknesses and exposed to Xenon arc light with outdoor cut-off filter to simulate outdoor irradiation conditions. Colour prediction models were developed from the obtained colour measurement data in the CIE XYZ colour space, since the progression of corresponding values showed a monotonous curve characteristic of each coating system. A novel colour measurement procedure was developed to estimate the colour of early- and latewood in the annual rings of wood. This method made it possible to generate colour-consistent textures for use in rendering software, as demonstrated on two examples.

Cell geometry across the ring structure of Sitka spruce.

For wood to be used to its full potential as an engineering material, it is necessary to quantify links between its cell geometry and the properties it exhibits at bulk scale. Doing so will make it possible to predict timber properties crucial to engineering, such as mechanical strength and stiffness, and the resistance to fluid flow, and to inform strategies to improve those properties as required, as well as to measure the effects of interventions such as genetic manipulation and chemical modification. Strength, stiffness and permeability of timber all derive from the geometry of its cells, and yet current practice is to predict them based on properties, such as bulk density, that do not directly describe the cell structure. This work explores links between micro-computed tomography data for structural-size pieces of wood, which show the variation of porosity across the wood's ring structure, and high-resolution tomography showing the geometry of the cells, from which we measure cell length, lumen area, porosity, cell wall thickness and the number density of cells. High-resolution scans, while informative, are time-consuming and expensive to run on a large number of samples at the scale of building components. By scanning the same volume of timber at both low and high resolutions (high-resolution scans over a near-continuous volume of timber of approx. 20 mm3 at 15 μm3 per voxel), we are able to demonstrate correlations between the measurements at the two different resolutions, reveal the physical basis for these correlations, and demonstrate that the data from the low-resolution scan can be used to estimate the variation in (small-scale) cell geometry throughout a structural-size piece of wood.

Climate Signal in Cork-Ring Chronologies: Case Studies in Southwestern Portugal and Northwestern Algeria

In temperate regions, the analysis of climate signals encoded in the wood rings allows assessing tree sensitivity to climate and its potential effects on growth and yield. In Mediterranean regions, the cork oak (Quercus suber L.) has received limited attention for dendrochronological studies because tree rings are faint and cork rings with a clear annual banding have been rather neglected. We analyzed the climatic signal of cork-ring chronologies for AD 1996–2010 from distinct regions in western Algeria [a mountain oak forest called Hafir-Zarieffet] and in southern Portugal [a peneplain wood-pasture called Benavente]. The goal was to evaluate the strength and consistency of climate signal and to assess cork growth sensitivity to climate variables (precipitation and temperature). Our results suggest that cork growth encodes a climatic signal. Trends of cork growth, via correlation analysis, including climate variables (on a monthly and seasonal basis) and Lang's index (on an annual basis) were successfully assessed. Drought-driven cork growth reduction is a threshold function of a P-T ratio, and with expected increase in the drought occurrence under changing climate, cork growth is likely to be similarly affected in both regions.

Water resistance of natural joint of spruce produced by linear friction welding without any treatment

ABSTRACTThis research work showed that spruce wood can be butt welded in a short time end-grain to-end-grain without any treatment. Wood welding has already been shown to be well adapted to the manufacture of wood structures of larger dimensions. When pressure increased, the welded material formed is of higher density and consequently the water resistance improved. The welded spruce samples present a much improved water resistance when the welding pressure was increased from 2.75 MPa to 3.75 MPa for the same welding time of 6 s. The welded interphase in end-grain-to-end-grain butt welding of spruce appears to occur by the formation of an interphase having the appearance of finger-joints. This is due to the different behaviours of the late and early wood rings of spruce during welding. This, by increasing the surface of contact, is shown to improve the water resistance of the original butt joint.

False Ring Formation in Bald Cypress (Taxodium distichum)

False rings are intra-annual bands of high density xylem cells that form in response to an environmental condition that a causes a tree to form two bands of latewood cells during a single growing season. We examined whether precipitation and/or stream flow measurements coincided with false ring formation in adult bald cypress trees (Taxodium distichum (L.) Rich.). We collected increment cores from bald cypress growing along the Blackwater and Nottoway Rivers in Virginia, U.S.A. The frequency and timing of false rings was quantified for each core. Annual synchronicity of false ring formation occurred, indicating a common environmental trigger. At both sites, false ring formation in bald cypress appeared to be more common during years with late summer precipitation and associated high late summer stream flow. In years when moisture is available late in the growing season, dormant bald cypress trees resume earlywood formation and a false ring is formed. Therefore, false rings in bald cypress wood can serve as a proxy record of seasonal historical stream flow and precipitation.

Tree ring wood density of Scots pine and European beech lower in mixed-species stands compared with monocultures

Mixed species stands are on the advance in Central Europe and many recently published studies have reported that they can overyield monocultures in terms of volume growth. However, as forest research has in the past been focused on monocultures, knowledge of how mixed-species stands and monocultures compare in terms of wood quality remains limited. Based on five triplets of fully stocked monocultures and mixed stands of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.), we analysed whether tree species mixing modifies wood quality and, more precisely, tree ring wood density.From a total of 322 trees we sampled increment cores for the analyses of tree ring width and tree ring wood density using a LIGNOSTATION™. We found that tree ring width of Scots pine was, on average, 14% wider in mixed compared with pure stands. Tree ring width of European beech did not differ between pure and mixed stands. Tree ring wood density was lower in mixed stands compared to pure stands for both Scots pine (−12%) and European beech (−8%). Tree ring wood density and tree ring width were negatively correlated in the case of Scots pine and positively correlated for European beech.When considering tree size and Stand density index, it was found that only tree ring width and mean tree ring wood density of European beech were influenced by stand density. Tree size had a significant effect only on tree ring wood density of European beech. The overall result of larger tree rings of Scots pine in mixed stands and a lower tree ring wood density of both species in mixed stands compared to pure stands was not influenced by stand density or tree size.Based on the measured values of tree ring wood density we conducted estimates of how mixed stands performed in terms of biomass. We found stem biomass to be 8% lower in mixed stands compared to pure stands. Reasons for the revealed differences in tree ring wood density and consequences for, among others, overyielding, carbon storage, and wood quality are discussed.

Anatomical and genetic aspects of ash dieback: a look at the wood structure

Pathogen diseases are increasingly threatening forest trees under the current climate change, causing a remarkable decrease in the stability of forest ecosystems. Ash (Fraxinus excelsior L.) dieback due to Hymenoscyphus fraxineus has been noted in Poland since 1992 and has spread over many European countries. The aim of this study was to test the hypothesis that ash trees affected by dieback could exhibit a reduced vessel size and density along the trunk, as well as a lowered width of annual wood rings, leading to the weakening of water transport towards the crown. Dead and dying ash trees were sampled in a forest district severely affected by ash decline in southern Poland. Wood samples were collected at different height along the trunk and several wood anatomical characteristics of annual tree rings over the period 2002-2011 were examined. Dead trees showed a stronger reduction in radial growth than dying trees over the period considered. Moreover, the diameter of vessels increased from the crown to the base in both dead and dying trees, while the density decreased. Significant differences between dead and dying trees were detected in size and density of vessels in the period analyzed, as well as in the width of annual rings. DNA extracted from wood samples was analyzed using SSR markers and the main genetic parameters of dead and dying trees were estimated, finding similar levels of polymorphism and only slight non-significant differences between the two health groups. Our results are consistent with the hypothesis that pathogens could disrupt the hormonal control of wood formation by interfering with the polar auxin transport, progressively leading to the death of ash trees.

ТЕРМИЧЕСКИЙ АНАЛИЗ ДРЕВЕСИНЫ ЛИСТВЕННИЦЫ (LARIX GMELINII (RUPR.) RUPR.)

The thermal decomposition of tree rings (separately, latewood and earlywood) of Larix gmelinii (Rupr.) Rupr.) during the period from 1988 to 1998 was studied using thermogravimetric analysis (TG / DTG) and differential scanning calorimetry (DSC). Thermal analysis was performed in oxidizing (air) condition. The stages of thermal decomposition of wood were analyzed by heating the sample from 30 to700 °C at the heating rates of 10, 20, 40 °C/min for TG / DTG and from 30 to590 °C at the heating rates of 10, 40 °C/min for DSC. The temperature ranges, mass loss, mass loss rate, temperature DTG / DSC peaks, thermal evaporation effects of moisture and the processes of thermal decomposition for each annual layer were studied. The result of thermogravimetry measurements were carried out using the Broido and Ozawa – Flynn – Wall methods. Tree rings of larch wood on the basis of the analysis of the activation energy values of the individual stages of thermal decomposition and activation energy dependency on the degree of conversion of wood material different tree rings; and based on the comparison of the mass loss for corresponding stages of thermal destruction, thermal effects, and other parameters of TG / DSC and DTG were characterized. The material presented in the study would, in our view, to study the impact of growing conditions on wood physical properties and chemical composition of wood, which are the basis for determining the direction of ways to use it, as well as indicators of the reaction of wood plants on endogenous and exogenous conditions.

Late-rotation nitrogen fertilization of Douglas-fir: growth response and fibre properties

Late-rotation fertilization of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) 5 to 10 years before harvesting is a common management practice in British Columbia and the US Pacific Northwest. Despite widespread operational application, knowledge on the impact of late-rotation fertilization on forests, especially fibre properties, is lacking. In this study, we evaluate the growth response and fibre properties following nitrogen fertilization in a productive second-growth coastal Douglas-fir site at age 57 years. Destructive sampling of dominant and co-dominant trees in fertilized and control plots 5 years after fertilization indicated significant gain in stem volume (30%–40%) that was uniformly distributed along the stem. There were no discernible effects on wood quality at the log level in terms of resonance acoustic velocity. However, fibre properties within breast height tree rings indicated significant reductions of ring wood density (by 8%), earlywood density (17%), latewood percentage (10%), and modulus of elasticity (8%). Tracheid dimensions declined in earlywood (reduction of wall thickness by 15%), latewood (radial diameter by 8%), and fibre length (by 6%). Results indicate that late-rotation nitrogen fertilization of Douglas-fir may lead to a significant growth response with only minimal reduction of fibre properties. It is possible that the negative impact on fibre properties could become more significant for repeated applications or higher rates of nitrogen fertilization.