Stress wave sorting of red maple logs for structural quality

Existing log grading procedures in the United States make only visual assessments of log quality. These procedures do not incorporate estimates of the modulus of elasticity (MOE) of logs. It is questionable whether the visual grading procedures currently used for logs adequately assess the potential quality of structural products manufactured from them, especially those for which MOE is of primary concern. The purpose of this study was to investigate the use of stress wave nondestructive evaluation techniques to sort red maple logs for the potential quality of lumber obtained from them. Ninety-five red maple logs were nondestructively evaluated using longitudinal stress wave techniques and sorted into four stress wave grades. The logs were then sawn into cants and lumber. The same procedure was used to obtain stress wave times in the cants and lumber. The lumber specimens were then dried and graded using a transverse vibration technique. The results of this study showed that good relationships existed between stress wave times measured in logs, cants, and the lumber produced from the logs. It was found that log stress wave grades have positive relationships with the lumber grades. Logs with high stress wave grades produced high-grade lumber. These findings indicate that the longitudinal stress wave technique has potential in sorting logs and cants for the production of high MOE products.The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright.     

New splitting method for wood fracture characterization

Summary A testing procedure with a new and simple specimen shape is presented which is appropriate to characterize fracturing of inhomogeneous and complex materials like wood. With this, the fracture energy of spruce wood is determined in the TL and RL direction. The size effect, i.e. influences of specimen dimensions on K_IC and G_f (specific fracture energy) are investigated. Stress and deformation distribution in the newly developed specimens are analysed with FE methods. The measured load-displacement curves are approximated by bilinear softening diagrams and FE analysis. Based on these results, it is tried to interpret typical deviations from LEFM's behaviour by mechanisms like microcracking, crack branching or crack tip bridging.The authors thank Dr. A. Teischinger for supplying the testing material and Dipl. Ing M. Elser for preparation of the diagrams. Financial support of the Fonds zur Förderung der wissenschaftlichen Forschung, Wien is gratefully acknowledged.     

Estimating the onset of cambial activity in Scots pine in northern Finland by means of the heat-sum approach

We estimated the date of onset (Date(est)) of cambial activity by the pinning method in Scots pine (Pinus sylvestris L.) trees at Vanttauskoski (Site 1) and Laanila (Site 2) near the latitudinal limit of Scots pine in northern Finland. In each year and at each site, observations were made on a different set of five trees. The estimated dates of onset of cambial activity were compared with the corresponding heat sums, calculated in degree-days according to two models. Within years, Date(est) varied among trees by up to 15 days at Site 1 and up to 13 days at Site 2. Among years, mean Date(est) varied by 15.3 days at Site 1 and 12.0 days at Site 2. The overall mean Date(est) differed between sites by 6 days (June 5 at Site 1 and June 11 at Site 2). Among all trees in all years, the mean number of degree days (d.d.) calculated from mean daily temperature above a threshold of 5 degrees C before Date(est) ranged from 68.7 to 135 d.d. at Site 1 and from 37.4 to 154.7 d.d. at Site 2. Among years, the mean heat sum before Date(est )ranged from 94 to 112.5 d.d. at Site 1 and from 61.4 to 136 d.d. at Site 2. Variation among years in heat sum before Date(est) at Site 2 was highly significant, indicating that one or more factors other than, or in addition to, heat sum determines the onset of cambial activity in Scots pine. Similar results were obtained when heat sum was computed from the area between the sine wave generated by daily maximum and minimum temperature and the threshold temperature.     

Dendroclimatic signals of pedunculate oak (Quercus robur L.) in Estonia

This study investigates the climate impact on the radial increment of pedunculate oak (Quercus robur L.) in Estonia at the species’ northern distribution limit. Tree-ring width series of 162 living oaks were compiled into three regional chronologies—western (1646–2008), northeastern (1736–2011), and southeastern Estonia (1912–2011). Although these regional growth patterns are similar to each other and even to the growth patterns in adjacent regions, spatial differences in growth responses to climate were established. Thus, oaks growing on shallow soil in western Estonia are positively influenced by summer (June–August) precipitation, and oaks on the deeper soil in northeastern Estonia are favoured by June temperature, while oaks in the southeastern part of the country depend on both July precipitation and temperature. These relationships are pronounced especially in pointer years. However, due to the impact of regional weather fluctuations on tree growth, there is a lack of correspondence between the local and the pan-European pointer years. In addition, our research presents the first tree-ring-based palaeoclimatic reconstruction for the country. Although the created model has relatively low predictive skill describing less than a quarter of the variance in actual summer precipitation in western Estonia, it has passable capacity of detecting past rainfall extremes.     

Changes of soil chemistry,stand nutrition,and stand growth at two Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.) sites in Central Europe during 40 years after fertilization,liming, and lupine introduction

Long-term (40 years) effects of two soil amelioration techniques [NPKMgCa fertilization + liming; combination of PKMgCa fertilization, liming, tillage, and introduction of lupine (Lupinus polyphyllus L.)] on chemical topsoil properties, stand nutrition, and stand growth at two sites in Germany (Pfaffenwinkel, Pustert) with mature Scots pine (Pinus sylvestris L.) forest were investigated. Both sites are characterized by base-poor parent material, historic N and P depletion by intense litter-raking, and recent high atmospheric N input. Such sites contribute significantly to the forested area in Central Europe. Amelioration resulted in a long-term increase of pH, base saturation, and exchangeable Ca and Mg stocks in the topsoil. Moreover, significant losses of the forest floor in organic carbon (OC) and nitrogen stocks, and a decrease of the C/N ratio in the topsoil were noticed. The concentrations and stocks of OC and N in the mineral topsoil increased; however, the increases compensated only the N, but not the OC losses of the forest floor. During the recent 40 years, the N nutrition of the stands at the control plots improved considerably, whereas the foliar P, K, and Ca concentrations decreased. The 100-fascicle weights and foliar concentrations of N, P, Mg, and Ca were increased after both amelioration procedures throughout the entire 40-year period of investigation. For both stands, considerable growth acceleration during the recent 40 years was noticed on the control plots; the amelioration resulted in an additional significant long-term growth enhancement, with the NPKMgCa fertilization liming + being more effective than the combination of PKMgCa fertilization, liming, tillage, and introduction of lupine. The comprehensive evaluation of soil, foliage, and growth data revealed a key relevance of the N and P nutrition of the stands for their growth, and a change from initial N limitation to a limitation of other growth factors (P, Mg, Ca, and water).     

White-tailed deer herbivory and timber harvesting rates: Implications for regeneration success

Herbivory by white-tailed deer (Odocoileus virginianus) can affect forest regeneration. Typical measures to ensure forest regeneration have included physical barriers or direct manipulation of deer densities. However, altering silvicultural practices to provide abundant deer forage has not been tested thoroughly. We examined browse species preferences and changes in herbivory rates in 1–6 year old regeneration areas from 2001 to 2004 in the central Appalachians on the MeadWestvaco Wildlife and Ecosystem Research Forest in West Virginia. Woody vegetation reached the maximum plot coverage by the 4th growing season. However, the establishment of less abundant woody species, such as northern red oak (Quercus rubra), may be inhibited when browsed greater than or proportionally to occurrence. Herbivory rates declined precipitously as the amount of early successional habitat increased on our study site. We conclude that providing approximately 14% of an area in well-distributed, even-aged managed forests can have substantial impacts on reducing herbivory rates. However, management practices also should consider harvesting effects on hard mast production, habitat requirements of other species, and hardwood lumber marketability.     

Early selection for resistance to <Emphasis Type="Italic">Heterobasidion parviporum</Emphasis> in Norway spruce is not likely to adversely affect growth and wood quality traits in late-age performance

Infections with Heterobasidion parviporum devalue the Norway spruce timber as the decayed wood does not meet the necessary quality requirements for sawing. To evaluate the incorporation of disease resistance in the Norway spruce breeding strategy, an inoculation experiment with H. parviporum on 2-year-old progenies of 466 open-pollinated families was conducted under greenhouse (nursery) conditions. Lesion length in the phloem (LL), fungal growth in sapwood (FG) and growth (D) were measured on an average of 10 seedlings for each family. The genetic variation and genetic correlations between both LL, FG and growth in the nursery trial and wood quality traits measured previously from 21-year old trees in two progeny trials, including solid-wood quality traits (wood density, and modulus of elasticity) and fiber properties traits (radial fiber width, tangential fiber width, fiber wall thickness, fiber coarseness, microfibril angle and fiber length). For both LL and FG, large coefficients of phenotypic variation (>?26%) and genetic variation (>?46%) were detected. Heritabilities of LL and FG were 0.33 and 0.42, respectively. We found no significant correlations between wood quality traits and growth in the field progeny trials with neither LL nor FG in the nursery trial. Our data suggest that the genetic gains may reach 41 and 52% from mass selection by LL and FG, respectively. Early selection for resistance to H. parviporum based on assessments of fungal spread in the sapwood in nursery material, FG, will not adversely affect growth and wood quality traits in late-age performance.     

What is new about new forest owners? A typology of private forest ownership in Austria

With structural changes in agriculture, new types of forest owners have become increasingly important. This article develops an empirically-based typology of forest owners in Austria. Based on a representative survey and by means of cluster analysis, seven types of forest owners are identified. These types form a sequence, ranging from forest owners with a strong agricultural background to forest owners with no agricultural background at all. The latter exhibit markedly different behaviour in various respects, e.g. in their interest in forest-related information. The increasing number of ‘new’ forest owners raises important questions for forest policy, especially how policy instruments can reach these owners and how extension services can address them.     

Spatial changes of soil fungal and bacterial biomass from a sub-alpine coniferous forest to grassland in a humid, sub-tropical region

 Fungal and bacterial biomass were determined across a gradient from a forest to grassland in a sub-alpine region in central Taiwan. The respiration-inhibition and ergosterol methods for the evaluation of the microbial biomass were compared. Soil fungal and bacterial biomass both significantly decreased (P<0.05) with the shift of vegetation from forest to grassland. Fungal and bacterial respiration rates (evolved CO₂) were, respectively, 89.1 μl CO₂ g^–1 soil h^–1 and 55.1 μl CO₂ g^–1 soil h^–1 in the forest and 36.7 μl CO₂ g^–1 soil h^–1 and 35.7 μl CO₂ g^–1 soil h^–1 in the grassland surface soils (0–10 cm). The fungal ergosterol content in the surface soil decreased from the forest zone (108 μg g^–1) to the grassland zone (15.9 μg g^–1). A good correlation (R ²=0.90) was exhibited between the soil fungal ergosterol content and soil fungal CO₂ production (respiration) for all sampling sites. For the forest and grassland soil profiles, microbial biomass (respiration and ergosterol) declined dramatically with depth, ten- to 100-fold from the surface organic horizon to the deepest mineral horizon. With respect to fungal to bacterial ratios for the surface soil (0–10 cm), the forest zone had a significantly (P<0.05) higher ratio (1.65) than the grassland zone (1.05). However, there was no fungal to bacterial ratio trend from the surface horizon to the deeper mineral horizons of the soil profiles. Received: 30 March 2000