The relationship between form and function in trees is the subject of a longstanding debate in fo... more The relationship between form and function in trees is the subject of a longstanding debate in forest ecology and provides the basis for theories concerning forest ecosystem structure and metabolism. Trees interact with the wind in a dynamic manner and exhibit natural sway frequencies and damping processes that are important in understanding wind damage. Tree-wind dynamics are related to tree architecture, but this relationship is not well understood. We present a comprehensive view of natural sway frequencies in trees by compiling a dataset of field measurement spanning conifers and broadleaves, tropical and temperate forests. The field data show that a cantilever beam approximation adequately predicts the fundamental frequency of conifers, but not that of broadleaf trees. We also use structurally detailed tree dynamics simulations to test fundamental assumptions underpinning models of natural frequencies in trees. We model the dynamic properties of greater than 1000 trees using a ...
Frontiers in forests and global change, Aug 10, 2023
Modeling spatial variation in radiata pine slenderness (height/diameter ratio) and vulnerability ... more Modeling spatial variation in radiata pine slenderness (height/diameter ratio) and vulnerability to wind damage under current and future climate in New Zealand.
In order for wood to be used to make composite products, feedstock originating from trees and log... more In order for wood to be used to make composite products, feedstock originating from trees and logs must first be obtained, sometimes as a by-product of other primary wood processing operations. This chapter provides a summary of primary wood processing as it relates to the production of the raw materials used in wood composites. It begins with an overview of peeling and sawmilling, which are used to provide the materials for solid wood composites. It then describes the production of chips, flakes and fibres that are used to manufacture composite panels. Finally, a brief overview is presented on the production of nanocellulose from wood.
This paper is concerned with the extent to which portable stress-wave-based instruments can be us... more This paper is concerned with the extent to which portable stress-wave-based instruments can be used to segregate Sitka spruce trees and logs; in particular the relationship between acoustic velocity and the properties of sawn timber. Measurements were made at 64 sites which were selected to span a range of conditions. At each site a portable stress wave timer (IML Hammer) was used to estimate the dynamic modulus of elasticity (Ed) on a sample of ten standing trees. Differences between sites accounted for 36 percent of the total variation in Ed, while differences between trees within a site and sides of the tree account for 55 and 9 percent of the variation respectively. Trees were felled from a representative sub-sample of 12 sites and the Ed of logs estimated using the HM-200 resonance instrument. At an individual tree level, a strong relationship was observed between measurements made on standing trees and those made on the butt log. The mean bending stiffness (Es) of timber cut from an individual site was strongly related to the mean stress wave velocity of both trees and logs from that site showing that it is possible to directly manipulate the characteristic stiffness of a population of sawn timber by segregating logs based on stress-wave velocity values. Taken together, these results demonstrate how non-destructive measurements made on standing trees and logs can assist the forest products industry to improve timber properties and that such approaches work for Sitka spruce grown under UK conditions. The average Ed of logs at a site was also found to be negatively associated with the average live crown ratio of trees at the site offering the possibility of partial sorting, even without acoustic tools.
Plantation forestry is now an imperative to meet wood requirements efficiently on the finite land... more Plantation forestry is now an imperative to meet wood requirements efficiently on the finite land available for wood production. Three main determinants of profitability are productivity, price per unit of wood harvested, and harvest age (the sooner the better). The first two are largely self-evident, while reducing harvest age lowers the effective cost of growing wood. Among these determinants, however, are strong interplays which include trade-offs. Key trade-offs involve adverse genetic correlations between various wood properties and growth-rate variables, and adverse effects on the wood quality of silvicultural interventions that raise site productivity and/or reduce harvest age. Moreover, the adverse effects of silviculture on wood properties tend to be accompanied by heightened expressions of genetic variation in wood properties. The trade-offs involve both increasing the percentage of corewood ('juvenile wood') and some more direct effects on wood quality. The pervasiveness of the trade-offs, and the heightened genetic expression, accentuate the call for genetic selection to defend wood quality. Such selection, however, will entail some costs in the appropriate emphasis on breeding for productivity. In this paper we review these issues, identify gaps in research information and offer guidance for tree breeders and silviculturists. While radiata pine is the special case, the applicability to some other species is briefly discussed.
To maximize utilization of our forest resources, detailed knowledge of wood property variation an... more To maximize utilization of our forest resources, detailed knowledge of wood property variation and the impacts this has on end-product performance is required at multiple scales (within and among trees, regionally). As many wood properties are difficult and time-consuming to measure our knowledge regarding their variation is often inadequate as is our understanding of their responses to genetic and silvicultural manipulation. The emergence of many non-destructive evaluation (NDE) methodologies offers the potential to greatly enhance our understanding of the forest resource; however, it is critical to recognize that any technique has its limitations and it is important to select the appropriate technique for a given application. In this review, we will discuss the following technologies for assessing wood properties both in the field: acoustics, Pilodyn, Resistograph and Rigidimeter and the lab: computer tomography (CT) scanning, DiscBot, near infrared (NIR) spectroscopy, radial samp...
An inventory of fresh logging wounds from treatment implementation was performed in a regional gr... more An inventory of fresh logging wounds from treatment implementation was performed in a regional green-tree retention experiment in Oregon and Washington. The DEMO (Demonstration of Ecosystem Management Options) study contains six treatments replicated in six blocks: (1) 100% retention (control), (2) 75% aggregated retention, (3) 40% dispersed retention, (4) 40% aggregated retention, (5) 15% dispersed retention, and (6) 15% aggregated retention. Over all blocks and treatments, Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) comprised 74.9% of all measured trees, and the proportion of trees damaged was similar for both species. Suppressed trees tended to be more susceptible to damage than were trees in other crown classes. A greater proportion of trees in the dispersed retention treatments were damaged than in the aggregated treatments. Only in the two dispersed retention treatments were levels of damage significantly different from the control (P < 0.05...
Forestry: An International Journal of Forest Research, 2019
Understanding tree stability under self-weight and applied loads from wind and snow is important ... more Understanding tree stability under self-weight and applied loads from wind and snow is important when developing management strategies to reduce the risk of damage from these abiotic agents. In this paper, linear buckling analysis was conducted using the finite element method to identify the instability modes of a tree structure under a specified set of loads. A non-prismatic elastic circular column of height H was analysed, taking self-weight into account. Various scenarios were considered: column taper, base rigidity, radial and longitudinal stiffness, ellipticity and crown weight. The effect on the critical buckling height was assessed in each case. Validation against closed form solutions of benchmark problems was conducted satisfactorily. The results indicate that column taper, base rigidity and the stiffness/density ratio are particularly important for this problem. Further comparison was made using data from a 15-year old Pinus radiata stand in New Zealand, which contained bo...
Forestry: An International Journal of Forest Research, 2018
Determining the magnitude of climate change effects is crucial for informing national economic st... more Determining the magnitude of climate change effects is crucial for informing national economic strategies, forest management and offsetting increasing carbon emissions. This study synthesizes predicted climate change impacts and future biosecurity threats to New Zealand's plantation forests. Projected productivity increases for radiata pine (Pinus radiata D. Don), the main commercial forest species in New Zealand, are slight due to changing climatic conditions. However including photosynthetic effects from increasing CO 2 , productivity gains across New Zealand averaged 19 per cent by 2040 and 37 per cent by 2090. This increased productivity results in marked increases in wind risk due to trees becoming taller and more slender. The average season length with 'very high and extreme' climatic fire risk increases by 71 per cent up to 2040 and by 83 per cent up to 2090. Currently, the most significant biotic disturbances in New Zealand plantations come from two needle cast diseases, for which climate projections show slight increases or decreases depending on the disease and region. Although insect pests currently cause little damage to New Zealand plantations, damage may increase in the future with projected increases in population and host susceptibility. It has not been possible to fully account for the effects of any new introductions of pests and pathogens and evidence from other countries with a significant resource of planted forests suggest this should not be underestimated. Potentially invasive weedy and damaging tree species are likely to expand their range under climate change and compete more strongly with plantations.
Co-innovation can be effective for complex challenges – involving interactions amongst multiple s... more Co-innovation can be effective for complex challenges – involving interactions amongst multiple stakeholders, viewpoints, perceptions, practices and interests across programmes, sectors and national systems. Approaches to challenges in the primary sector have tended to be linear, where tools and outputs are developed by a few, mostly scientists/researchers, and then extended to stakeholders. A co-innovation approach first deciphers and delineates the biophysical, societal, regulatory, policy, economic and environmental drivers, constraints and controls influencing these challenges at multiple levels. Second, stakeholder interactions and perspectives can inform and change the focus as well as help in co-developing solutions to deliver agreed outcomes. However, there is limited systematic and comparative research on how co-innovation works out in different projects. Here we analyse the results of applying a co-innovation approach to five research projects in the New Zealand primary se...
Virot et al. [E. Virot et al., Phys. Rev. E 93, 023001 (2016)10.1103/PhysRevE.93.023001] assert t... more Virot et al. [E. Virot et al., Phys. Rev. E 93, 023001 (2016)10.1103/PhysRevE.93.023001] assert that the critical wind speed at which ⩾50% of all trees in a population break is ≈42 m/s, regardless of tree characteristics. We show that empirical data do not support this assertion, and that the assumptions underlying the theory used by Virot et al. are inconsistent with the biomechanics of trees.
In order to drive forest sector productivity, an emphasis has been placed on effectively transfer... more In order to drive forest sector productivity, an emphasis has been placed on effectively transferring science knowledge to technical foresters. Having a communications plan and engaging the right stakeholders early can induce a rich learning environment that strengthens context, knowhow and ensures mechanisms are in place for knowledge to be transferred. Formalized structures such as reports and seminars have evolved to improve the science transfer process, but it appears that the key success factor in enhancing uptake and learning may require an environment that encourages relationship building, particularly trust building between parties in developing informal and formal relationships. Informal interactions, though not often acknowledged in business, foster the conditions conducive to good knowledge exchange – co-ordination, co-operation and communication. Enhancing conditions in which these three aspects grow can lead to increased social capital, changed paradigms and reduced bus...
Timber production from Scots pine forests in Great Britain is forecast to increase over the next ... more Timber production from Scots pine forests in Great Britain is forecast to increase over the next 15 years. This Research Note presents the results of a project to develop and test methods for assessing the quality of Scots pine timber from measurements on trees ...
ABSTRACT Mechanical stress resulting from wind forces acting on trees can cause a number of direc... more ABSTRACT Mechanical stress resulting from wind forces acting on trees can cause a number of direct and indirect effects ranging from microscopic changes in cambial activity through to stem breakage and uprooting. To better understand these effects on radial stem growth and wood properties, an experiment was established in a 13-year-old radiata pine (Pinus radiata D Don) stand in which 20 trees were guyed to prevent them from swaying. Radial growth was monitored in these trees and 20 matched controls at monthly intervals for 5 years. The trees were then felled and radial growth, resin features and compression wood were assessed on cross-sectional discs taken at fixed locations up the stem. There was a significant reduction in radial growth at breast height (1.4 m above the ground) in the guyed trees, but an increase in growth immediately above the guying point. A total of 277 resin features were observed in the growth rings formed following guying. The overall frequency of such features was related to height within the stem and annual ring number. No effect of stem guying was found on the incidence of compression wood. Interestingly, the distribution of resin features also did not differ between guyed and un-guyed trees. There was no evidence of a link between stem restraint as a result of guying and the incidence of resin features, suggesting that other factors, such as soil moisture may be more influential.
Determining the Shear Modulus of Sitka Spruce from Torsion Tests Aamir KHOKHAR PhD Student Centre... more Determining the Shear Modulus of Sitka Spruce from Torsion Tests Aamir KHOKHAR PhD Student Centre for Timber Engineering, Napier University Edinburgh, UK Dr. Hexin ZHANG Lecturer School of Engineering and the Built Environment, Napier University Edinburgh, UK ...
The paper examines the variation in modulus of elasticity (MoE) and shear modulus (G) within sawn... more The paper examines the variation in modulus of elasticity (MoE) and shear modulus (G) within sawn timber and the implications for testing timber in accordance with EN408:2003. A combination of mechanical testing and simple analytical modelling is used to examine the differences between global and local MoE, and the extent to which these differences can be explained by the inhomogeneity of stiffness within a batten. In the light of these findings, the methods prescribed for determining G from flexural tests are called into question.
To explore the effects of wind on tree form and wood quality, 30 transects were placed across eac... more To explore the effects of wind on tree form and wood quality, 30 transects were placed across each of three relatively narrow stands of Pinus radiata, aged 11, 17 and 25 years old, on the Canterbury Plains, New Zealand. The experimental design assumed that the major influence on stand edges to be the prevailing strong north-westerly winds that blow across this region. Outerwood dynamic modulus of elasticity (E d) and tree height increased with distance from the stand edge, while taper reduced. The negative effect of wind extended into the stand the equivalent of one tree height, regardless of the age of the stand, with the least stiff trees (i.e., those with the lowest E d) located at the stand edge. Surprisingly, larger effects were observed at the downwind edge of these stands, although the reasons for this are not clear. Results from this study indicate that for those stands investigated trees located at the stand edge, or within a distance equivalent to one tree height from the edge, may be of marginal value for structural timber.
Measurements taken from trees growing in exposed and sheltered areas within two structurally simi... more Measurements taken from trees growing in exposed and sheltered areas within two structurally similar forests were used to investigate the influence of wind on branch characteristics of mature New Zealand-grown Pinus radiata. A widely used branch model was used to remove the influence of treatment and site differences in tree stem diameter and height, so that the influence of wind on branch diameter could be examined. At site 1 average windspeed in the exposed treatment exceeded average windspeed in the sheltered treatment by 62%. When averaged across sites, mean branch diameter, branch index (mean diameter of the largest branch, in each of the four azimuthal quadrants) and largest branch diameter in exposed areas significantly exceeded values for trees in sheltered areas by 9 mm (25%), 42 mm (54%), and 72 mm (72%), respectively. Treatment and site differences in tree stem diameter and height partially accounted for the observed increases in branch diameter. However, after these effects were removed by the model, branch diameter in exposed areas still significantly exceeded that in sheltered areas by 21 mm for branch index and 44 mm for the largest branch. Treatment and site variation in this residual branch diameter was almost entirely attributable to topographical exposure to 1 km, a variable which has been found to be strongly correlated to windspeed. Possible reasons for these observed wind-induced increases in branch diameter are discussed.
There is little information about the impacts of past Sitka spruce (Picea sitchensis [Bong.] Carr... more There is little information about the impacts of past Sitka spruce (Picea sitchensis [Bong.] Carr.) tree breeding on wood properties because the emphasis has traditionally been on improving stem form and growth rates. This study used both SilviScan and mechanical testing to investigate the radial variations in wood stiffness, bending strength, density and microfibril angle in defect-free samples taken from the first United Kingdom progeny trial to reach merchantable size. We tested for differences in these radial patterns of variation in half-sibling progeny of three plus trees originally selected for superior growth rate and stem form against a non-selected control. Large differences in all of the properties were observed with radial position, with properties generally being less desirable in the corewood. Significant undesirable differences between the improved families and the control were found for stiffness, strength and microfibril angle. There was no significant relationship between wood density and stiffness in samples taken from the inner part of the tree, where stiffness was more closely associated with microfibril angle. Overall, previous selections for growth rate and/or stem form have compromised timber properties. It is recommended that current breeding programmes focus on corewood stiffness to prevent further degradation in the wood properties of the future timber supply.
The relationship between form and function in trees is the subject of a longstanding debate in fo... more The relationship between form and function in trees is the subject of a longstanding debate in forest ecology and provides the basis for theories concerning forest ecosystem structure and metabolism. Trees interact with the wind in a dynamic manner and exhibit natural sway frequencies and damping processes that are important in understanding wind damage. Tree-wind dynamics are related to tree architecture, but this relationship is not well understood. We present a comprehensive view of natural sway frequencies in trees by compiling a dataset of field measurement spanning conifers and broadleaves, tropical and temperate forests. The field data show that a cantilever beam approximation adequately predicts the fundamental frequency of conifers, but not that of broadleaf trees. We also use structurally detailed tree dynamics simulations to test fundamental assumptions underpinning models of natural frequencies in trees. We model the dynamic properties of greater than 1000 trees using a ...
Frontiers in forests and global change, Aug 10, 2023
Modeling spatial variation in radiata pine slenderness (height/diameter ratio) and vulnerability ... more Modeling spatial variation in radiata pine slenderness (height/diameter ratio) and vulnerability to wind damage under current and future climate in New Zealand.
In order for wood to be used to make composite products, feedstock originating from trees and log... more In order for wood to be used to make composite products, feedstock originating from trees and logs must first be obtained, sometimes as a by-product of other primary wood processing operations. This chapter provides a summary of primary wood processing as it relates to the production of the raw materials used in wood composites. It begins with an overview of peeling and sawmilling, which are used to provide the materials for solid wood composites. It then describes the production of chips, flakes and fibres that are used to manufacture composite panels. Finally, a brief overview is presented on the production of nanocellulose from wood.
This paper is concerned with the extent to which portable stress-wave-based instruments can be us... more This paper is concerned with the extent to which portable stress-wave-based instruments can be used to segregate Sitka spruce trees and logs; in particular the relationship between acoustic velocity and the properties of sawn timber. Measurements were made at 64 sites which were selected to span a range of conditions. At each site a portable stress wave timer (IML Hammer) was used to estimate the dynamic modulus of elasticity (Ed) on a sample of ten standing trees. Differences between sites accounted for 36 percent of the total variation in Ed, while differences between trees within a site and sides of the tree account for 55 and 9 percent of the variation respectively. Trees were felled from a representative sub-sample of 12 sites and the Ed of logs estimated using the HM-200 resonance instrument. At an individual tree level, a strong relationship was observed between measurements made on standing trees and those made on the butt log. The mean bending stiffness (Es) of timber cut from an individual site was strongly related to the mean stress wave velocity of both trees and logs from that site showing that it is possible to directly manipulate the characteristic stiffness of a population of sawn timber by segregating logs based on stress-wave velocity values. Taken together, these results demonstrate how non-destructive measurements made on standing trees and logs can assist the forest products industry to improve timber properties and that such approaches work for Sitka spruce grown under UK conditions. The average Ed of logs at a site was also found to be negatively associated with the average live crown ratio of trees at the site offering the possibility of partial sorting, even without acoustic tools.
Plantation forestry is now an imperative to meet wood requirements efficiently on the finite land... more Plantation forestry is now an imperative to meet wood requirements efficiently on the finite land available for wood production. Three main determinants of profitability are productivity, price per unit of wood harvested, and harvest age (the sooner the better). The first two are largely self-evident, while reducing harvest age lowers the effective cost of growing wood. Among these determinants, however, are strong interplays which include trade-offs. Key trade-offs involve adverse genetic correlations between various wood properties and growth-rate variables, and adverse effects on the wood quality of silvicultural interventions that raise site productivity and/or reduce harvest age. Moreover, the adverse effects of silviculture on wood properties tend to be accompanied by heightened expressions of genetic variation in wood properties. The trade-offs involve both increasing the percentage of corewood ('juvenile wood') and some more direct effects on wood quality. The pervasiveness of the trade-offs, and the heightened genetic expression, accentuate the call for genetic selection to defend wood quality. Such selection, however, will entail some costs in the appropriate emphasis on breeding for productivity. In this paper we review these issues, identify gaps in research information and offer guidance for tree breeders and silviculturists. While radiata pine is the special case, the applicability to some other species is briefly discussed.
To maximize utilization of our forest resources, detailed knowledge of wood property variation an... more To maximize utilization of our forest resources, detailed knowledge of wood property variation and the impacts this has on end-product performance is required at multiple scales (within and among trees, regionally). As many wood properties are difficult and time-consuming to measure our knowledge regarding their variation is often inadequate as is our understanding of their responses to genetic and silvicultural manipulation. The emergence of many non-destructive evaluation (NDE) methodologies offers the potential to greatly enhance our understanding of the forest resource; however, it is critical to recognize that any technique has its limitations and it is important to select the appropriate technique for a given application. In this review, we will discuss the following technologies for assessing wood properties both in the field: acoustics, Pilodyn, Resistograph and Rigidimeter and the lab: computer tomography (CT) scanning, DiscBot, near infrared (NIR) spectroscopy, radial samp...
An inventory of fresh logging wounds from treatment implementation was performed in a regional gr... more An inventory of fresh logging wounds from treatment implementation was performed in a regional green-tree retention experiment in Oregon and Washington. The DEMO (Demonstration of Ecosystem Management Options) study contains six treatments replicated in six blocks: (1) 100% retention (control), (2) 75% aggregated retention, (3) 40% dispersed retention, (4) 40% aggregated retention, (5) 15% dispersed retention, and (6) 15% aggregated retention. Over all blocks and treatments, Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla) comprised 74.9% of all measured trees, and the proportion of trees damaged was similar for both species. Suppressed trees tended to be more susceptible to damage than were trees in other crown classes. A greater proportion of trees in the dispersed retention treatments were damaged than in the aggregated treatments. Only in the two dispersed retention treatments were levels of damage significantly different from the control (P < 0.05...
Forestry: An International Journal of Forest Research, 2019
Understanding tree stability under self-weight and applied loads from wind and snow is important ... more Understanding tree stability under self-weight and applied loads from wind and snow is important when developing management strategies to reduce the risk of damage from these abiotic agents. In this paper, linear buckling analysis was conducted using the finite element method to identify the instability modes of a tree structure under a specified set of loads. A non-prismatic elastic circular column of height H was analysed, taking self-weight into account. Various scenarios were considered: column taper, base rigidity, radial and longitudinal stiffness, ellipticity and crown weight. The effect on the critical buckling height was assessed in each case. Validation against closed form solutions of benchmark problems was conducted satisfactorily. The results indicate that column taper, base rigidity and the stiffness/density ratio are particularly important for this problem. Further comparison was made using data from a 15-year old Pinus radiata stand in New Zealand, which contained bo...
Forestry: An International Journal of Forest Research, 2018
Determining the magnitude of climate change effects is crucial for informing national economic st... more Determining the magnitude of climate change effects is crucial for informing national economic strategies, forest management and offsetting increasing carbon emissions. This study synthesizes predicted climate change impacts and future biosecurity threats to New Zealand's plantation forests. Projected productivity increases for radiata pine (Pinus radiata D. Don), the main commercial forest species in New Zealand, are slight due to changing climatic conditions. However including photosynthetic effects from increasing CO 2 , productivity gains across New Zealand averaged 19 per cent by 2040 and 37 per cent by 2090. This increased productivity results in marked increases in wind risk due to trees becoming taller and more slender. The average season length with 'very high and extreme' climatic fire risk increases by 71 per cent up to 2040 and by 83 per cent up to 2090. Currently, the most significant biotic disturbances in New Zealand plantations come from two needle cast diseases, for which climate projections show slight increases or decreases depending on the disease and region. Although insect pests currently cause little damage to New Zealand plantations, damage may increase in the future with projected increases in population and host susceptibility. It has not been possible to fully account for the effects of any new introductions of pests and pathogens and evidence from other countries with a significant resource of planted forests suggest this should not be underestimated. Potentially invasive weedy and damaging tree species are likely to expand their range under climate change and compete more strongly with plantations.
Co-innovation can be effective for complex challenges – involving interactions amongst multiple s... more Co-innovation can be effective for complex challenges – involving interactions amongst multiple stakeholders, viewpoints, perceptions, practices and interests across programmes, sectors and national systems. Approaches to challenges in the primary sector have tended to be linear, where tools and outputs are developed by a few, mostly scientists/researchers, and then extended to stakeholders. A co-innovation approach first deciphers and delineates the biophysical, societal, regulatory, policy, economic and environmental drivers, constraints and controls influencing these challenges at multiple levels. Second, stakeholder interactions and perspectives can inform and change the focus as well as help in co-developing solutions to deliver agreed outcomes. However, there is limited systematic and comparative research on how co-innovation works out in different projects. Here we analyse the results of applying a co-innovation approach to five research projects in the New Zealand primary se...
Virot et al. [E. Virot et al., Phys. Rev. E 93, 023001 (2016)10.1103/PhysRevE.93.023001] assert t... more Virot et al. [E. Virot et al., Phys. Rev. E 93, 023001 (2016)10.1103/PhysRevE.93.023001] assert that the critical wind speed at which ⩾50% of all trees in a population break is ≈42 m/s, regardless of tree characteristics. We show that empirical data do not support this assertion, and that the assumptions underlying the theory used by Virot et al. are inconsistent with the biomechanics of trees.
In order to drive forest sector productivity, an emphasis has been placed on effectively transfer... more In order to drive forest sector productivity, an emphasis has been placed on effectively transferring science knowledge to technical foresters. Having a communications plan and engaging the right stakeholders early can induce a rich learning environment that strengthens context, knowhow and ensures mechanisms are in place for knowledge to be transferred. Formalized structures such as reports and seminars have evolved to improve the science transfer process, but it appears that the key success factor in enhancing uptake and learning may require an environment that encourages relationship building, particularly trust building between parties in developing informal and formal relationships. Informal interactions, though not often acknowledged in business, foster the conditions conducive to good knowledge exchange – co-ordination, co-operation and communication. Enhancing conditions in which these three aspects grow can lead to increased social capital, changed paradigms and reduced bus...
Timber production from Scots pine forests in Great Britain is forecast to increase over the next ... more Timber production from Scots pine forests in Great Britain is forecast to increase over the next 15 years. This Research Note presents the results of a project to develop and test methods for assessing the quality of Scots pine timber from measurements on trees ...
ABSTRACT Mechanical stress resulting from wind forces acting on trees can cause a number of direc... more ABSTRACT Mechanical stress resulting from wind forces acting on trees can cause a number of direct and indirect effects ranging from microscopic changes in cambial activity through to stem breakage and uprooting. To better understand these effects on radial stem growth and wood properties, an experiment was established in a 13-year-old radiata pine (Pinus radiata D Don) stand in which 20 trees were guyed to prevent them from swaying. Radial growth was monitored in these trees and 20 matched controls at monthly intervals for 5 years. The trees were then felled and radial growth, resin features and compression wood were assessed on cross-sectional discs taken at fixed locations up the stem. There was a significant reduction in radial growth at breast height (1.4 m above the ground) in the guyed trees, but an increase in growth immediately above the guying point. A total of 277 resin features were observed in the growth rings formed following guying. The overall frequency of such features was related to height within the stem and annual ring number. No effect of stem guying was found on the incidence of compression wood. Interestingly, the distribution of resin features also did not differ between guyed and un-guyed trees. There was no evidence of a link between stem restraint as a result of guying and the incidence of resin features, suggesting that other factors, such as soil moisture may be more influential.
Determining the Shear Modulus of Sitka Spruce from Torsion Tests Aamir KHOKHAR PhD Student Centre... more Determining the Shear Modulus of Sitka Spruce from Torsion Tests Aamir KHOKHAR PhD Student Centre for Timber Engineering, Napier University Edinburgh, UK Dr. Hexin ZHANG Lecturer School of Engineering and the Built Environment, Napier University Edinburgh, UK ...
The paper examines the variation in modulus of elasticity (MoE) and shear modulus (G) within sawn... more The paper examines the variation in modulus of elasticity (MoE) and shear modulus (G) within sawn timber and the implications for testing timber in accordance with EN408:2003. A combination of mechanical testing and simple analytical modelling is used to examine the differences between global and local MoE, and the extent to which these differences can be explained by the inhomogeneity of stiffness within a batten. In the light of these findings, the methods prescribed for determining G from flexural tests are called into question.
To explore the effects of wind on tree form and wood quality, 30 transects were placed across eac... more To explore the effects of wind on tree form and wood quality, 30 transects were placed across each of three relatively narrow stands of Pinus radiata, aged 11, 17 and 25 years old, on the Canterbury Plains, New Zealand. The experimental design assumed that the major influence on stand edges to be the prevailing strong north-westerly winds that blow across this region. Outerwood dynamic modulus of elasticity (E d) and tree height increased with distance from the stand edge, while taper reduced. The negative effect of wind extended into the stand the equivalent of one tree height, regardless of the age of the stand, with the least stiff trees (i.e., those with the lowest E d) located at the stand edge. Surprisingly, larger effects were observed at the downwind edge of these stands, although the reasons for this are not clear. Results from this study indicate that for those stands investigated trees located at the stand edge, or within a distance equivalent to one tree height from the edge, may be of marginal value for structural timber.
Measurements taken from trees growing in exposed and sheltered areas within two structurally simi... more Measurements taken from trees growing in exposed and sheltered areas within two structurally similar forests were used to investigate the influence of wind on branch characteristics of mature New Zealand-grown Pinus radiata. A widely used branch model was used to remove the influence of treatment and site differences in tree stem diameter and height, so that the influence of wind on branch diameter could be examined. At site 1 average windspeed in the exposed treatment exceeded average windspeed in the sheltered treatment by 62%. When averaged across sites, mean branch diameter, branch index (mean diameter of the largest branch, in each of the four azimuthal quadrants) and largest branch diameter in exposed areas significantly exceeded values for trees in sheltered areas by 9 mm (25%), 42 mm (54%), and 72 mm (72%), respectively. Treatment and site differences in tree stem diameter and height partially accounted for the observed increases in branch diameter. However, after these effects were removed by the model, branch diameter in exposed areas still significantly exceeded that in sheltered areas by 21 mm for branch index and 44 mm for the largest branch. Treatment and site variation in this residual branch diameter was almost entirely attributable to topographical exposure to 1 km, a variable which has been found to be strongly correlated to windspeed. Possible reasons for these observed wind-induced increases in branch diameter are discussed.
There is little information about the impacts of past Sitka spruce (Picea sitchensis [Bong.] Carr... more There is little information about the impacts of past Sitka spruce (Picea sitchensis [Bong.] Carr.) tree breeding on wood properties because the emphasis has traditionally been on improving stem form and growth rates. This study used both SilviScan and mechanical testing to investigate the radial variations in wood stiffness, bending strength, density and microfibril angle in defect-free samples taken from the first United Kingdom progeny trial to reach merchantable size. We tested for differences in these radial patterns of variation in half-sibling progeny of three plus trees originally selected for superior growth rate and stem form against a non-selected control. Large differences in all of the properties were observed with radial position, with properties generally being less desirable in the corewood. Significant undesirable differences between the improved families and the control were found for stiffness, strength and microfibril angle. There was no significant relationship between wood density and stiffness in samples taken from the inner part of the tree, where stiffness was more closely associated with microfibril angle. Overall, previous selections for growth rate and/or stem form have compromised timber properties. It is recommended that current breeding programmes focus on corewood stiffness to prevent further degradation in the wood properties of the future timber supply.
Moore, J. (2011). Wood properties and uses of Sitka spruce in Britain. Forestry Commission Resear... more Moore, J. (2011). Wood properties and uses of Sitka spruce in Britain. Forestry Commission Research Report. Forestry Commission, Edinburgh. i-vi + 1-48 pp.
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