Wood Discs Research Articles

Evaluation of fiber characteristics and basic density of Acacia melanoxylon (R.Br.) grown in Ethiopia for pulp and paper making

The fiber characteristics and basic density of Acacia melanoxylon were investigated for its potential as a raw material for pulp and paper production. Six trees from the even-aged stand and similar diameter class were selected randomly from the Chencha district of Ethiopia. Wood disks were systematically cross-cut from a log along tree height levels, at the bottom (10%), middle (50%) and top (90%) of the merchantable height and blocks of wood (2 cm x 2 cm x 2 cm) were taken from pith to periphery at near pith (10%), middle (50%) and near bark (90%) of disk radius. Fiber maceration and basic density were determined, by 50% nitric acid solution and water displacement method respectively. All the data were analyzed using a two-way analysis of variance at α = 0.05. The fiber characteristics of the selected trees; the fiber length, fiber diameter, lumen diameter and cell wall thickness were measured while the-slenderness ratio, Runkel ratio, flexibility coefficient and wall coverage ratio of the fibers were derived from the measured fiber dimensions. The result showed that- the overall mean were, 1.04 mm, 21.60 µm, 15.36 µm, 3.75 µm, 0.48, 48.05%, 71.10%, 0.34 and 0.56 g/ml, for fiber length, fiber width, lumen diameter, cell wall thickness, Runkle ratio, slenderness ratio, flexibility ratio, wall coverage ratio and basic density, respectively. Generally, Acacia melanoxylon wood is suitable for pulp-and-paper-production, to due-to-its adequate-fiber dimension, derived fiber value and basic density. Therefore, attention should be given to tree growers, government and non-governmental organizations on the plantation expansion of Acacia melanoxylon.

Ahşap malzemede aktif anti-bakteriyel özelliklerin defne ve kekik ekstraktları ile artırılması

Ahşap ürünler gün geçtikçe hayatımıza daha çok girmekle birlikte temas edilen ahşap yüzeylerin hijyenik olarak güvenli olup olmadığı ile ilgili bazı soru işaretlerini de beraberinde getirmektedir. Ahşap malzemenin pasif ve aktif olmak üzere iki farklı anti-bakteriyel özelliğinden bahsedilebilir. Burada, pasif anti-bakteriyel özellik ahşabın doğası gereği olan porozif yapısı ve higroskopisiteden kaynaklanmaktadır. Ancak, ahşabın aktif anti-bakteriyel özelliği ise odun içeriğinde bulunan ekstraktif maddeler ile ilişkilidir. Bu çalışmanın amacı, hijyenik açıdan hassas alanlarda kullanılmak üzere defne (Laurus nobilis) ve kekik (Origanum onites) ekstraktları ile muamele edilmiş odunların anti-bakteriyel özelliklerinin direk difüzyon yöntemi ile incelenmesidir. Deneyleri gerçekleştirmek için 10 farklı bakteri suşu kullanılmıştır. Deneylerde kullanılan ahşap diskler aktif anti-bakteriyel özellikleri düşük kavak (Populus tremula) ağacından hazırlandıktan sonra otoklav ile sterilize edilmiştir. Bakteri suşları 0,5 McFarland’da hazırlanarak sürüntü sürme yöntemiyle Mueller-Hinton agar petri kaplarına aşılanmıştır. Daha sonra odun diskleri doğrudan aşılanmış agar üzerine yerleştirilmiştir. 37 °C’de 24 saat inkübasyondan sonra, disklerin etrafındaki agar üzerindeki inhibisyon bölgesi mm olarak not edilmiştir. Elde edilen sonuçlara göre, kavak odununa uygulanan kekik ekstraktlarının bakteriyel büyümeyi azalttığı tespit edilmiştir. Böylece, anti-bakteriyel özelliği düşük olan ağaç türlerinin kekik ekstraktları ile muamele edilerek hijyenik açıdan hassas alanlarda kullanımının olumlu sonuçlar vereceği tespit edilmiştir.

Antitumor Properties of Aqueous Extracts from Inonotus rheades Mycelium and Their Evaluation under Various Cultivation Conditions.

The antitumor properties of aqueous extracts of Inonotus rheades basidiomycete mushrooms were evaluated when the fungi were cultured on wood discs and wood shavings (birch) at 25 ± 1°C in the dark and under constant illumination with blue light (12.8 W/m2). The aqueous fraction containing water-soluble polysaccharides was isolated and analyzed: WS-5 fraction cultured on wood discs under blue light illumination, WS-8 fraction grown under similar conditions on wood shavings; WS-6 fraction grown in the dark on wood discs; and WS-7 fraction grown under similar conditions on wood shavings. The antitumor effects of the extracts were studied on the model of Ehrlich ascites carcinoma in mice. It was found that the extracts isolated from the basidial fungus Inonotus rheades exhibit antitumor properties and that their accumulation during growth is determined by different cultivation conditions.

Using acoustic emission technique for detecting checks on industrial-size beech wood disks during drying

Wood disks are very susceptible to checking during drying. The present study was aimed to determine a suitable transducer mounting configuration to detect the drying checks with acoustic emission (AE) technique. AE generated during drying of 30-mm-thick beech (Fagus orientalis L.) wood disk with a diameter of 300 mm were monitored using piezoelectric AE transducers operating at frequency of 50-200 kHz. The transducers were directly attached on the disks with four combinations depending on the sensor number and grain direction. Total number of AE events and event rate were associated with drying time and checking features. The successive formation of near-bark radial checks was detected due to fluctuations in the AE event rate. Results showed that if the transducers are attached to the disk lateral surfaces, the formation of pith checks cannot be detected in the early stages of the check formation. The V-shaped cracks can be only detected when the transducer is mounted very close to the crack location. Overall, our results showed that more than two transducers are required to detect all types of checks occurred during drying of wood disks of this size. They should be attached parallel to the grain, one near to the pith and the rest at a suitable distance around periphery of the disk.

Evaluation of Selected Physical Properties of Blighia sapida K. Koenig Wood

Blighia sapida, a Lesser-Used Species is being processed into sawn timber to meet the demand for wood. The knowledge of its wood quality would enhance its effective utilization. However, there is little information known on the physical properties of this species that could enhance its acceptability and optimum utilization. This, therefore, necessitate the need to investigate the physical properties of this wood species.
 Three standing trees of B. sapida were purposively felled for this study. Billets of 500 mm were obtained from the wood disc at the base, middle, and top of the tree. Each wood disc was partitioned into three; innerwood, middlewood, and outerwood following specified international standards for the physical properties test (wood colour, proportion of sapwood and heartwood, bark thickness, density, moisture content, and volumetric shrinkage).
 B. sapida wood density with a mean value of 709.78±8.88 kg/m3, ranged from (571.59±13.45 to 854.81±7.08 kg/m3. Moisture content percentage of average value 70.62±1.23%, ranged from 53.84±1.40 to 89.00±2.75%. Volumetric shrinkage of average value 15.24±0.25%, range from 13.38±0.66 to 16.89±0.83%. The range of B. sapida wood density value of the study falls within the range that could be categorized as medium density wood of medium construction strength properties. The 1:1.5% tangential–radial shrinkage observed in this study was low, an indicator of a low risk of deformation while seasoning the wood, as the ratios of tangential-radial shrinkage that is high are those over 2.2%.

Calibração do instrumento Pilodyn para determinação indireta in situ da densidade básica da madeira de pau-de-balsa

ABSTRACT: Balsa wood is used widely in the nautical, aeronautical and wind-energy industries because of its low-density and high-resistance. In the Brazilian state of Mato Grosso, speculative producers with little knowledge of the culture have established balsa plantations using non-standardized and non-selected seedlings. In this sense, research is needed to improve balsa cultivation under Brazilian conditions to better explore the resource. The present study evaluated the efficiency of the Pilodyn instrument for the indirect determination of the basic wood density (BWD) of balsa. Twenty 12-year old balsa trees cultivated in Alta Floresta, Mato Grosso, were probed with the Pilodyn instrument on both north and south faces of the trunk at the base and at 1.30 and 3.10 m from the ground. Wood discs were subsequently collected from the probed sites and BWD determined according to the water-immersion method. Data were submitted to the Shapiro-Wilk normality test followed by analysis of variance and Pearson’s correlation analysis with α=0.05. The BWD of balsa decreased in the direction from the base to the top of the tree. The penetration depth of the Pilodyn probe was inversely proportional to BWD with a correlation that was strong (R2=0.72) at heights of 1.30 and 3.10 m but considered weak (R2=0.46) at the base of the trunk. The reliability of the Pilodyn method was sufficient to allow the development of a linear equation that could be applied for the indirect determination of the BWD of balsa based on the penetration depth of the Pilodyn probe assessed at 1.30 m from the ground.

Growth differential related to wood structure and function of Eucalyptus spp. clones adapted to seasonal drought stress

Aim of the study: To evaluate the growth performance, wood density and anatomical features of four drought-tolerant Eucalyptus spp. clones, at 4 years, and to examine the relationships between these characteristics and some functional parameters. Area of study: The analyzed trees were from a clonal test installed in a region characterized by seasonal drought stress in central-western Brazil. Methods: Trees were felled, followed by obtaining dendrometric parameters and wood disk sampling to determine wood bulk density by x-ray densitometry, and morphometric parameters of fibers and vessels in order to evaluate the xylem hydraulic architecture. Lumen fraction (F), vessel composition (S) and hydraulic conductivity (Ks) were estimated. Results: Clone D (E. urophylla x E grandis) presented the highest growth rates, which was related to anatomical characteristics such as low relative frequency of wide vessels. High theoretical Ks does not necessarily imply higher growth rates and were related to lower wood densities. It is possible to infer that the better xylem adjustability of Eucalyptus trees in response to drought stress conditions is associated with increased vessel composition to the detriment of higher hydraulic conductivity. Research highlights: Vessel composition showed a greater variation among Eucalyptus genotypes and was positively associated with growth performance. Keywords: wood anatomy; dendrometry; X-ray densitometry; water stress; hydraulic conductivity. Abbreviations used: F: lumen fraction; S: vessel composition; Ks: theoretical xylem-specific hydraulic conductivity.

Effects of Strip Roads in a Pine Tree Stand (Pinus sylvestris L.) on the Diameter Growth and Pith Eccentricity of Trees Growing along Them

Although skid roads are more and more commonly used in Poland, they are still quite often criticised due to a certain loss of wood volume and the impact on edge trees. In this context, the results of the research described in this article can be used as a substantive contribution to discussions about strip roads. Research was carried out in a 42-year-old pine tree stand (Pinus sylvestris L.) in the Notecka Forest, where thinning had been performed and 2.5 and 3.5 m wide strip roads had been cut 10 years before. The analysis comprised two five-year periods recording diameter growth and pith eccentricity in trees growing at the distance zones of 0–1 m (adjacent trees), 2–4 m and 8–10 m (the control) away from the strip roads. The differences in growth and eccentricity between the different distance zones as well as the frequency of pith eccentricity in the N-W, S-W, N-E and S-E directions were assessed, related to the distance from the strip road and the measurement height. The measurements of the analysed traits were conducted on wood discs cut from the centres of two-metre-long sections on sample trees (12 trees in each distance zone). The trees growing directly beside the strip roads were statistically significantly thicker than those growing 8–10 m away, and in the case of the trees beside the narrower strip roads, in the second 5-year period, they were also thicker than the trees from the 2–4 m distance zone. The effect of the wider strip roads in the first growth period was also significant for the trees growing 3 m away from the strip road (their growth in this period was significantly greater than that of trees in the control zone). The research into tree-pith eccentricity showed no differences due to relative distance from the strip road. Furthermore, no statistically significant relationship between the distance of trees from the strip road, measurement height and frequency of tree-pith eccentricity to the N-W and S-W were found.

DAMAGE BY DEFOLIATING INSECTS AND ITS EFFECT ON THE QUALITY OF WOOD FOR CHARCOAL PRODUCTION

The objective of the present work has been to evaluate the impact of damage caused by defoliating insects on wood quality and charcoal production, and to quantify the losses per hectare according to the charcoal produced. Seven-year-old Eucalyptus grandis × Eucalyptus urophylla (clone A) and Eucalyptus saligna (clone B) trees, both in healthy condition and damaged by defoliating insects, were selected, with five trees to be used per treatment. Wood disks were removed from the trees at 0, 25, 50, 75 and 100% of the commercial height for analyzing the properties of the wood and for preparing and characterizing the charcoal. Damage by defoliating insects decreased the basic density of the trees at all axial positions by up to 23 kg m-3. Also, the extractives and lignin contents increased, while the holocellulose content decreased in the attacked plants. Changes in the wood characteristics led to increased fixed carbon content and gravimetric yield, and a decrease in density. The charcoal productivity from the plants damaged by defoliating insects was lower, mainly because of the decrease in volumetric production.

Characterization of wood popularly known as “Louros” in the Brazilian amazon by visible spectroscopy and CIELAB parameters

Aim of study: The objective of this work was to evaluate the potential of colorimetry to discriminate wood from the “louros” group, in particular to contribute to a database of Brazilian native species for future application in logging control actions.Area of study: The wooden discs were collected in a Sustainable Forest Management Area (AMFS) belonging to two extractivist communities, Paraiso and Arimum, both in the “Green Forever” Extractivist Reserve, in the municipality of Porto de Moz, Pará state, Brazil.Material and methods: Colorimetric evaluation was carried out based on data from the CIEL*a*b* system, analyzed using PCA and ANOVA in a completely randomized design in a two-factor scheme.Main results: PCA produced some evidence of color patterns and some parameters may be more useful in caracterization. Longitudinal surfaces were more indicated for this group caracterization. The data from CIEL*a*b* system produce helpful information for distinction of wood from “louros” group, and so, the colorimetric technique can be an auxiliary tool for separation of this group, complementary to other techniques as wood anatomy.Research highlights: Correct discrimination of wood from “louros” group in commerce control; Brazilian native species.Keywords: Species distinction; Lauraceae; Proteaceae; color parameters.Abbreviations used: Comission International de L’Eclairage: CIE, Sustainable Forest Management Area: AMFS, Ministry of the Environment: MMA, Chico Mendes Institute: ICMBio, Authorization and Biodiversity Information System: SISBIO, National System for Genetic Heritage Management: SisGen, Analysis of variance: ANOVA, Principal Component Analysis: PCA, Aniba sp.: PR, Euplassa sp.: LB, Roupala sp.: LV, Ocotea sp.: LR, Ocotea sp.: LPI, Mezilaurus sp.: IT, Mezilaurus sp.: ITA.

Confocal spectral microscopy, a non-destructive approach to follow contamination and biofilm formation of mCherry Staphylococcus aureus on solid surfaces

Methods to test the safety of wood material for hygienically sensitive places are indirect, destructive and limited to incomplete microbial recovery via swabbing, brushing and elution-based techniques. Therefore, we chose mCherry Staphylococcus aureus as a model bacterium for solid and porous surface contamination. Confocal spectral laser microscope (CSLM) was employed to characterize and use the autofluorescence of Sessile oak (Quercus petraea), Douglas fir (Pseudotsuga menziesii) and poplar (Populus euramericana alba L.) wood discs cut into transversal (RT) and tangential (LT) planes. The red fluorescent area occupied by bacteria was differentiated from that of wood, which represented the bacterial quantification, survival and bio-distribution on surfaces from one hour to one week after inoculation. More bacteria were present near the surface on LT face wood as compared to RT and they persisted throughout the study period. Furthermore, this innovative methodology identified that S. aureus formed a dense biofilm on melamine but not on oak wood in similar inoculation and growth conditions. Conclusively, the endogenous fluorescence of materials and the model bacterium permitted direct quantification of surface contamination by using CSLM and it is a promising tool for hygienic safety evaluation.

Inferences on the Susceptibility of Wood of Different Tree Species to Heterobasidion annosum Sensu Lato Primary Infections and on the Range of Pathogen Spores Dispersal

Stumps play a pivotal role in the epidemiology of the fungal forest pathogens Heterobasidion spp. because they are the main courts of primary airborne infections. The aims of this study were (i) to determine the susceptibility of seven tree species (i.e., Larix sibirica, Picea abies, Picea sitchensis, Pinus contorta, Pinus strobus, Pinus sylvestris and Pseudotsuga menziesii) to primary infection by H. annosum and H. parviporum through comparative inoculation experiments of conidia on wood discs in controlled conditions; (ii) to compare the susceptibility of wood discs of the same tree species to natural airborne infections in two Latvian Norway spruce forest stands infested either by H. annosum or H. parviporum; (iii) to explore the rates of infection of wood discs at increasing distances from spore sources in these two forests to make inferences on the range of spores dispersal. Results obtained by spraying wood discs with conidial suspensions in controlled conditions are in agreement with those obtained by exposing wood discs to the natural airborne inoculum in the forests, as clearly supported by the significant correlation (r = 0.79; p < 0.05) between the two sets of data. Susceptibility was highest in Pinus species, followed by P. abies and P. sitchensis. Susceptibility was lowest for L. sibirica and P. menziesii. The area colonized by Heterobasidion spp. in the sapwood of wood discs was much greater than that colonized in the heartwood. A sharp decrease in the rate of infection of wood discs with distance from spore sources (i.e., fruiting bodies) was observed, further confirming the importance of local spore sources in the epidemiology of Heterobasidion spp. Taken together, these findings could help designing tactics to manage these fungal forest pathogens.

Ecology of Oobius rudnevi, egg parasitoid of Cerambyx cerdo and Cerambyx welensii in oak forests

AbstractOobius rudnevi (Nowicki) (Hymenoptera: Encyrtidae) is a gregarious egg parasitoid of Cerambyx cerdo L. and Cerambyx welensii (Küster) (Coleoptera: Cerambycidae), two well‐known large oak‐living saproxylic beetles with different pest/legal status: whereas C. cerdo is a protected species, C. welensii is considered an emerging pest. Despite the potential interest of O. rudnevi as a native parasitoid, the knowledge of its biology remains very limited. We used sentinel eggs to assess the distribution of O. rudnevi in Extremadura (southwest Spain) and to explore its ecology, phenology, behavior, parasitism rates, and host preference. More than 13 500 sentinel eggs, housed in 1 030 wood disks, were field‐exposed during 2016–2018 in 147 oak stands over an array of oak forests. Oobius rudnevi was the only egg parasitoid detected, being widespread and relatively abundant over the studied area (90/147 stands, 61.2%) with adults flying in May–July. Parasitoids were detected in both host species, but net parasitism (PN) was significantly higher in C. cerdo (22.4%) than in C. welensii (9.5%). Net parasitism was affected by altitude (it was higher at 600–800 m) and tended to increase in colder aspects; PN was poorly related to host egg density (no. eggs per disk) and unrelated to host population size (no. adults per trap). Most parasitoids overwintered and emerged in the following spring (synchronously with their hosts) but some phenotypes/lineages did not undergo obligate diapause and were bivoltine. Bivoltine wasps were spatially widespread (27/90 stands, 30%), even if their actual prevalence was rather low (60/1641 parasitized eggs, 3.7%). We also found that O. rudnevi was slightly protogynous, the sex ratio was female‐biased, and the mean (± SEM) number of wasps emerging per parasitized egg was 9.3 ± 0.1 (range 1–29). We discuss the potential role of O. rudnevi as a biological control agent from an evolutionary perspective.

Sapwood and heartwood affect differentially bacterial and fungal community structure and successional dynamics during Quercus petraea decomposition.

In forests, bacteria and fungi are key players in wood degradation. Still, studies focusing on bacterial and fungal successions during the decomposition process depending on the wood types (i.e. sapwood and heartwood) remain scarce. This study aimed to understand the effect of wood type on the dynamics of microbial ecological guilds in wood decomposition. Using Illumina metabarcoding, bacterial and fungal communities were monitored every 3 months for 3 years from Quercus petraea wood discs placed on forest soil. Wood density and microbial enzymes involved in biopolymer degradation were measured. We observed rapid changes in the bacterial and fungal communities and microbial ecological guilds associated with wood decomposition throughout the experiment. Bacterial and fungal succession dynamics were very contrasted between sapwood and heartwood. The initial microbial communities were quickly replaced by new bacterial and fungal assemblages in the sapwood. Conversely, some initial functional guilds (i.e. endophytes and yeasts) persisted all along the experiment in heartwood and finally became dominant, possibly limiting the development of saprotrophic fungi. Our data also suggested a significant role of bacteria in nitrogen cycle during wood decomposition.

Antiviral Properties of Water Extracts of Mycelium Inonotus rheades (Pers.) P. Karst. (1882) against the Virus of Tick-Borne Encephalitis Virus in vitro

Background. Tick-borne encephalitis virus is dangerous and widespread pathogen that is transmitted to humans through the bites of hard ticks. Wild fungi, such as xylotrophic basidiomycetes, are widely used in traditional medicine to treat the infectious diseases and are promising natural sources of new antiviral agents. It was previously shown that aqueous extracts from the mycelium of the Inonotus rheades (Pers.) P. Karst. (1882) fungus exhibit significant antiviral activity against tick-borne encephalitis virus, however, the mechanisms of this activity remain unclear.Aim. To analyze the relationship between the virucidal properties of I. rheades extract and the substrate on which the cultivation was carried out.Materials and methods. The mycelium was grown either in a standard liquid medium with wort or on wooden disks from birch. Extracts of water-soluble polysaccharides were prepared from both mycelium samples. The concentration of infectious tick-borne encephalitis virus was determined using the method of titration of plaque-forming components (PFU). Approximately 30 000 PFU of tick-borne encephalitis virus was mixed with an equal volume of corresponding I. rheades extract at concentration of 8 mg/mL and incubated for 30 min at 37 °C. Afterwards, the residual infectivity of tick-borne encephalitis virus was determined using the identical virus sample incubated with sterile water as a reference.Results. It was found that treatment of tick-borne encephalitis virus with extracts from I. rheades mycelium resulted in inhibition of the infectivity of the virus in the cell culture. However, the same strain of I. rheades, grown on medium with wort, did not exhibit antiviral properties.Conclusions. Virucidal substances are likely to be not the main metabolites of the mycelium of I. rheades, but are rather metabolized wood polysaccharides. Further research is needed to more accurately identify the active ingredients and assess their antiviral activity.

A Tree Ring Measurement Method Based on Error Correction in Digital Image of Stem Analysis Disk

Stem analysis is an essential aspect in forestry investigation and forest management, as it is a primary method to study the growth law of trees. Stem analysis requires measuring the width and number of tree rings to ensure the accurate measurement, expand applicable tree species, and reduce operation cost. This study explores the use of Open Source Computer Vision Library (Open CV) to measure the ring radius of analytic wood disk digital images, and establish a regression equation of ring radius based on image geometric distortion correction. Here, a digital camera was used to photograph the stem disks’ tree rings to obtain digital images. The images were preprocessed with Open CV to measure the disk’s annual ring radius. The error correction model based on the least-square polynomial fitting method was established for digital image geometric distortion correction. Finally, a regression equation for tree ring radius based on the error correction model was established. Through the above steps, click the intersection point between the radius line and each ring to get the pixel distance from the ring to the pith, then the size of ring radius can be calculated by the regression equation of ring radius. The study’s method was used to measure the digital image of the Chinese fir stem disk and compare it with the actual value. The results showed that the maximum error of this method was 0.15 cm, the average error was 0.04 cm, and the average detection accuracy reached 99.34%, which met the requirements for measuring the tree ring radius by stem disk analysis. This method is simple, accurate, and suitable for coniferous and broad-leaved species, which allows researchers to analyze tree ring radius measurement, and is of great significance for analyzing the tree growth process.

Using the Non-Parametric Classifier CART to Model Wood Density

To identify the stand attributes that best explain the variability in wood density, Pinus radiata plantations located in the Chilean coastal sector were studied and modeled. The study area corresponded to stands located in sedimentary soil between the zones of Constituci on and Cobquecura. Within each sampling sector, individual tree variables were recorded and the most relevant stand parameters were estimated. Fifty trees were sampled in each sector, obtaining from each one six wood discs from different stem heights. Each disc was weighed in green and then dried to anhydrous weight, and its basic density was calculated. The profile identification to classify basic density according to stand characteristics was performed through regression trees, a technique based in the use of predictor variables to partition the database using recursive algorithms in regions with similar responses. The objective of the regression tree method is to obtain highly homogenous groups (branches), which are identified using pruning techniques that successively eliminate the branches that least contribute to the classification of the variable of interest. The results found that the stand attributes that contributed significantly to basic density classification were the basal area, the number of trees per hectare, and the mean height.

Using the Non-Parametric Classifier CART to Model Wood Density

To identify the stand attributes that best explain the variability in wood density, Pinus radiata plantations located in the Chilean coastal sector were studied and modeled. The study area corresponded to stands located in sedimentary soil between the zones of Constitucion and Cobquecura. Within each sampling sector, individual tree variables were recorded and the most relevant stand parameters were estimated. Fifty trees were sampled in each sector, obtaining from each one six wood discs from different stem heights. Each disc was weighed in green and then dried to anhydrous weight, and its basic density was calculated. The profile identification to classify basic density according to stand characteristics was performed through regression trees, a technique based in the use of predictor variables to partition the database using recursive algorithms in regions with similar responses. The objective of the regression tree method is to obtain highly homogenous groups (branches), which are identified using pruning techniques that successively eliminate the branches that least contribute to the classification of the variable of interest. The results found that the stand attributes that contributed significantly to basic density classification were the basal area, the number of trees per hectare, and the mean height.

Biocontrol potential of Pseudomonas protegens against Heterobasidion species attacking conifers in Europe

The biocontrol potential of a commercial product based on the bacterium Pseudomonas protegens (strain DSMZ 13134) and of its cell-free filtrate (CFF) was tested under controlled conditions in vitro and on wood discs against genotypes of the three native European Heterobasidion species and on the non-native H. irregulare, all reported as destructive forest pathogens in Europe. In vitro experiments through traditional dual culture assays and by incorporating CFF into the media showed that treatments were effective in reducing significantly and regardless of the culture medium and incubation temperature both mycelial growth and rate of conidial germination of Heterobasidion spp., and that antibiosis could be the main mechanism involved in the inhibition of Heterobasidion spp. Outcomes of dual culture assays performed on two-divided Petri plates further suggest that antibiosis operates through the production of diffusible rather than volatile compounds. Based on comparative experiments on wood discs of preferential hosts of Heterobasidion spp., CFF performed significantly better than the commercial product against most of Heterobasidion spp., further confirming that the antagonistic activity hinges on antibiosis rather than on other mechanisms. While on wood discs the tested treatments seem poorly effective against the non-native H. irregulare, CFF significantly and substantially reduced infections of the native European Heterobasidion species compared to controls mostly to the level of the state of the art chemical treatment urea and of the biological treatment based on Phlebiopsis gigantea.

Generalized cutting force model for peripheral milling of wood, based on the effect of density, uncut chip cross section, grain orientation and tool helix angle

The influence of the grain angle on the cutting force when milling wood is not yet detailed, apart from particular cases (end-grain, parallel to the grain, or in some rare cases 45°-cut). Thus, setting-up wood machining operations with complex paths still relies mainly on the experience of the operators because of the lack of scientific knowledge easily transferable to the industry. The aim of the present work is to propose an empirical model based on specific cutting coefficients for the assessment of cutting force when peripheral milling of wood based on the following input: uncut chip thickness and width, grain angle (angle between the tool velocity vector and the grain direction of the wood), density and tool helix angle. The specific cutting coefficients were determined by peripheral milling with different depths of cut wood disks issued from different wood species on a dynamometric platform to record the forces. Milling a sample into a round shape (a disk) allows to measure the cutting forces toward every grain angle into a sole basic diameter reduction operation. Force signals are then post-processed to carefully clean the natural vibrations of the system without impacting their magnitudes. The experiment is repeated on five species with a large range of densities, machining two disks per species for five depths of cut in up- and down milling conditions for three different tool helix angles. Finally, a simple cutting force model, based on the previously cited parameters, is proposed, and its robustness analysed.