Understanding compositional stability in mixedwood forests of eastern North America

Mixedwood forest composition, or co-dominance of hardwood and softwood species, has been interpreted as both stable and unstable. Through review of existing theory, we propose a conceptual model to understand mixedwood compositional stability in boreal and temperate forests of eastern North America. We first review the current theory that the strength of neighborhood effects (i.e. species ability to self-replace under their own canopy) is essential to understanding stability, such that when self-replacement is strong for both dominant hardwood and softwood species, composition is stable except at extreme disturbance severities. In contrast, when mixedwood forests are dominated by negligible or weak affinities to self-replace, composition is unstable and sensitive to changes in disturbance. Our new concept further posits that both change in the disturbance severity and in its vertical direction are essential to understanding stability. For example, where moderate-severity surface fires (which impact forests from below) cease and are replaced by moderate-severity blowdowns (which impact forests from above), instability can occur even when disturbance severity is unchanged. We therefore pose and discuss an extension to current theory to provide a new unifying concept of stability for mixedwood forests and, more broadly, for mixed-species forests.

Efficiency of Machine Sanding of Wood

We hypothesized that the type of wood, in combination with the grit size of sandpapers, would affect sanding efficiency. Fixed factors were used in the experiment (a belt sander with pressure p = 3828 Pa, and a belt speed of vs = 14.5 m/s) as well as variable factors (three sand belts (P60, P120, P180), six hardwood species (beech, oak, ash, hornbeam, alder, walnut) and three softwood species (pine, spruce, larch)). The masses of the test samples were measured until they were completely sanded. The sanding efficiency of hardwood species is less variable than for softwood species. Maximum sanding efficiency for the softwood ranged from 1 to 2 min, while for the hardwood species, it ranged from 2 to 4.5 min at the start of sanding and then decreased. The average time for complete sanding of the softwood samples was: 87 s (P60), 150 s (P120), and 188 s (P180). For hardwood, these times were 2.4, 1.5, and 1.8 times longer. The results indicate that the factors determining sanding efficiency are the type of wood, and, secondly, the grit size of sanding belts. In the first phase of blunting with the sanding belts, the sanding processes of hardwood and softwood are significantly different. In the second phase of blunting, sanding belts with higher grit numbers (P120 and P180) behaved similarly while sanding hardwood and softwood.

Species-specific basic stem-wood densities for twelve indigenous forest and shrubland species of known age, New Zealand

Background: Tree carbon estimates for New Zealand indigenous tree and shrub species are largely based on mean basic stem-wood densities derived from a limited number of trees, often of unspecified age and from a limited number of sites throughout New Zealand. Yet stem-wood density values feed directly into New Zealand’s international and national greenhouse gas accounting. We augment existing published basic stem-wood density data with new age-specific values for 12 indigenous forest and shrubland species, including rarely obtained values for trees <6-years old, across 21 widely-distributed sites between latitudes 35° and 46° S, and explore relationships commonly used to estimate carbon stocks. Methods: The volume of 478 whole stem-wood discs collected at breast height (BH) was determined by water displacement, oven dried, and weighed. Regression analyses were used to determine possible relationships between basic stem-wood density, and tree height, root collar diameter (RCD), and diameter at breast height (DBH). Unbalanced ANOVA was used to determine inter-species differences in basic stem-wood density in 5-yearly age groups (i.e. 0–5 years, 6–10 years etc.) (P<0.05). As specific taxa of Kunzea ericoides (Myrtaceae) has only been identified at some study sites we combine the data from each site, and use the term Kunzea spp. We compare our age- and species-specific results with existing published data where age is specified versus non-age-specific values. Results: Kunzea spp. and Leptospermum scoparium exhibited positive correlations between basic stem-wood density and tree height, RCD, and DBH. No relationships were established for Melicytus ramiflorus, Coprosma grandiflora, Weinmannia racemosa ?6-years old, or for Podocarpus totara, Agathis australis, Vitex lucens, and Alectryon excelsus <6-years old. Dacrydium cupressinum and Prumnopitys ferruginea <6-years old exhibited a significant positive relationship with DBH only, while for Dacrycarpus dacrydioides, each correlation was negative. Irrespective of age, basic stem-wood density is not different between the hardwood species L. scoparium and Kunzea spp. but is significantly greater (P=0.001) than that of the remaining, and predominantly softwood species of equivalent age. For Kunzea spp., L. scoparium, Coprosma grandiflora, Weinmannia racemosa, and Melicytus ramiflorus ?6-years old there was no evidence that basic stem-wood density increased with tree age, and values were within the range of published and unpublished data. For naturally reverting stands of Kunzea spp. located between latitudes 35° to 46° S, basic stem-wood density values tended to increase with decreased elevation and increased temperature. Conclusions: Increasing basic wood density values in Kunzea spp. with decreased elevation and increased temperature suggest that where local data are available its use would improve the accuracy of biomass estimates both locally and nationally. Furthermore, refining biomass estimates for existing communities of mixed softwood species, stands of regenerating shrubland, and new plantings of indigenous species will require additional basic stem-wood density values for scaling from stem wood volume to total stand biomass.

Flexural anisotropy of rift-sawn softwood boards induced by the end-grain orientation

Inspired by the use of rift-sawn softwood board for covering curved surfaces in Kokerabuki, a traditional Japanese roofing method, we investigated the flexural anisotropy of wood caused by its end-grain orientation. We measured the flexural displacement of softwood species, Chamaecyparis obtusa and Cryptomeria japonica, and hardwood species, Populus suaveolens and Cerasus serrulata. For the softwood species, this was approximately five times longer for the rift-sawn specimens than for the other grain patterns. Using the replica method to measure the softwood tracheid deformation with different flexural displacements, we confirmed the different deformation mechanisms of the tracheid in the flat- and quarter-sawn specimens, and rift-sawn specimens. In the flat- and quarter-sawn woods, on-axis loading was generated, in which the stress was concentrated on the radial and tangential cell walls parallel to the direction of tension or compression. By contrast, in the rift-sawn wood, off-axis loading was generated, in which the stress was evenly distributed throughout the corner cell walls without the wall directly resisting the tensile and compressive forces. We also concluded that the tapered shape of the tracheid walls contributes to the excellent flexibility of rift-sawn softwood.

Management of Maritime Pine: Energetic Potential with Alternative Silvicultural Guidelines

The interest in the use of energy of the forests has been increasing in recent decades. Biomass has the potential to provide a cost-effective and sustainable supply of renewable energy. Moreover, it could be valuable for reducing the severity of forest fires and create employment in extremely needy regions. This chapter brings to discuss the effect of forest management on the potential of energy provided by the woodlands. The authors selected as a case study the management of maritime pine (Pinus pinaster Ait.), an important softwood species in the southwest of Europe and, in particular, in Portugal where it represents around 22% of the forest area. A summary of traditional and new silvicultural guidelines for the species, used or proposed to be followed at the national level, is presented. The study follows with the evaluation of stand yield and the potential of energy associated with four alternative silvicultural guidelines. Two scenarios follow traditional standards (an initial density of 1100–1200 trees/ha), while the other two consider managing a high density stand (an initial density of 40,000 trees/ha). Simulations were performed with the ModisPinaster model. The results show that the new designs provide a considerable yield in terms of biomass and energy.

Calorific properties of the wood biomass from some softwood species

The aim of the paper is to highlight the importance of the calorific properties of softwood biomass. The paper presents the caloric power and ash content, important caloric properties in the assessment of wood biomass. Biomass, in the form of wood, was and will remain an important combustible material. The value of ash content for spruce was 3.8% and 4.2% for fir. These values are within the international standards. Wood biomass, as a material can provide the energy need for the population at a reduced price. The combustion process are possible only in the presence of oxygen, which is usually introduced into the focal spot through the combustion air.

Comparative Studies on Two Types of OSB Boards Obtained from Mixed Resinous and Fast-growing Hard Wood

The paper aims to compare the oriented strand boards (OSBs) made in the laboratory from a mixture of softwood species to those made from hardwood species, followed by their comparison to European and industry standards. In this regard, the main properties of the panels made in the laboratory were determined, including density, absorption, and swelling in thickness, modulus of elasticity, modulus of rupture, and internal bond. The analysis of the properties of swelling (24 h) and absorption (24 h) revealed that the mixture of softwood species was slightly better thanthe hardwood one. It was also shown that the panels manufactured from the mixture of hardwood species had better mechanical properties than those made of the softwood mixture (modulus of rupture (MOR) = 43.48 N/mm2, modulus of elasticity (MOE) = 7253 N/mm, and internal bond (IB) = 1.57 N/mm2). Additionally, the comparative analysis of properties indicates that the density is highly significant in determining the MOE values of the OSBs. This will allow softwood speciestobe replaced with other species of soft and fast-growing deciduous trees such as willow, birch, and poplar in the manufacture of oriented strand boards.