Trees, and their derivative products, have been used by societies around the world for thousands of years. Contemporary construction of tall buildings from timber, in whole or in part, suggests a growing interest in the potential for building with wood at a scale not previously attainable. As wood is the only significant building material that is grown, we have a natural inclination that building in wood is good for the environment. But under what conditions is this really the case? The environmental benefits of using timber are not straightforward; although it is a natural product, a large amount of energy is used to dry and process it. Much of this can come from the biomass of the tree itself, but that requires investment in plant, which is not always possible in an industry that is widely distributed among many small producers. And what should we build with wood? Are skyscrapers in timber a good use of this natural resource, or are there other aspects of civil and structural engineering, or large-scale infrastructure, that would be a better use of wood? Here, we consider a holistic picture ranging in scale from the science of the cell wall to the engineering and global policies that could maximise forestry and timber construction as a boon to both people and the planet.

The wood from the trees: The use of timber in construction

http://www.sysecol2.ethz.ch/Refs/EntClim/S/Se083.pdf

Modelling natural disturbances in forest ecosystems: a review

Summary This paper reviews the current status of mechanistic models for wind damage risk assessment, describing model structure, applicability, validation and current limitations. We focus particularly on the hybrid mechanistic/empirical models GALES and HWIND, which have been designed for calculating wind damage risk at the stand level within uniform forests and which are the most widely adopted models within the research community. These models have been integrated with different methods for predicting the local wind climate in order to calculate the probability of wind damage in a number of different countries. We also discuss ongoing modelling work and proposals for future development in order to deal with complex forest structures and to predict the wind damage risk of individual trees within stands through the integration of mechanistic risk models with forest growth and yield models within a geographical information system framework. This kind of model integration will enable spatial representation of tree lists and damage propagation and allow managers to evaluate the effect of different harvesting and thinning scenarios on the risk of windthrow of both stands and individual trees within a stand.

A review of mechanistic modelling of wind damage risk to forests

A database was constructed of tree-anchorage measurements from almost 2000 trees from 12 conifer species that were mechanically overturned on 34 sites in the United Kingdom between 1960 and 2000. A...

Anchorage of coniferous trees in relation to species, soil type, and rooting depth

Destructive storms in European forests: past and forthcoming impacts.

The anchorage of 40-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) trees grown in a plantation on a steep (ca. 30°) slope was compared with that of trees grown on an adjacent horizontal are...

Does steep terrain influence tree stability? A field investigation

Effects of early re-spacing on the physical and mechanical properties of Sitka spruce structural timber

Summary Mechanical tests were conducted on structural timber from a 37-year-old Sitka spruce ( Picea sitchensis (Bong.) Carr), progeny trial located in Kershope Forest, Cumbria, UK. Values of modulus of rupture (MOR) and global modulus of elasticity (MOE G ) in bending and density were compared between timber cut from four of the eight different seed lots which made up the experiment. Three of these seed lots were open-pollinated progeny of selected plus trees, while the fourth consisted of trees grown from an unimproved collection imported from the Queen Charlotte Islands (QCI) in British Columbia, Canada. The progenies from the plus trees were selected for their contrasting growth rates, stem form and wood density relative to the QCI control. Overall, the timber had characteristic values for density, MOR and MOE G consistent with the requirements for the C16 strength class. A signifi cant difference in timber basic density was observed between two of the seed lots; however, there was no difference in MOR or MOE G between any of the seed lots. Most of the variation in strength properties in the study was attributable to differences between individual trees ( » 40 per cent) and individual pieces of timber from within a tree ( » 50 per cent), with only a small amount ( 5 per cent) due to treatment differences. Results indicate that gains in merchantable log volume that have been achieved due to tree breeding do not appear to have been offset by a reduction in the mechanical properties of timber.

/pdf/effects-of-genetics-on-the-wood-properties-of-sitka-spruce-1ohn0r7esa.pdf

Effects of genetics on the wood properties of Sitka spruce growing in the UK: bending strength and stiffness of structural timber

1. A prototype method of assessing log quality in standing Sitka spruce trees was developed in the early 1990s and is described by Methley (1998). Straightness was identified as the most important single factor affecting log quality in Sitka spruce. Although knots were acknowledged to have a significant impact on log and sawn timber quality, they were not considered the primary cause of downgrade in spruce logs. An assessment method based on a visual estimate of straight log lengths in the first 6 m of the stem was devised.

Protocol for stem straightness assessment in Sitka spruce.

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.

/pdf/variation-of-radial-wood-properties-from-genetically-mj2qtn0bch.pdf

Shaun Mochan

Papers

Does steep terrain influence tree stability? A field investigation

Effects of early re-spacing on the physical and mechanical properties of Sitka spruce structural timber

Effects of genetics on the wood properties of Sitka spruce growing in the UK: bending strength and stiffness of structural timber

Protocol for stem straightness assessment in Sitka spruce.

Variation of radial wood properties from genetically improved Sitka spruce growing in the UK