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Ayous wood : main uses and selected physical and mechanical properties of an increasingly interesting material originating from cameroon

Gennari Emiliano, Picchio Rodolfo, Lo Monaco Angela

Drewno : prace naukowe, doniesienia, komunikaty

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2022

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Vol. 65, nr 209

art. no. 1644-3985.391.09

EN

Triplochiton scleroxylon K. Schum, commonly named ayous in Cameroon, is a tree typical of secondary forests in subtropical areas mainly below 500 msl, characterized by an uneven distribution of annual rainfall and the presence of disturbance. This species is widely used in the origin area, and the interest of European markets for ayous wood has steadily increased in the last decades. Despite the interest, only a few studies explored the characterization of this wood for its Cameroonian provenience. This study was carried out to provide a general overview of the available information and to determine some selected physical and mechanical properties of ayous wood coming from the department of Boumba et Ngoko in South-east Cameroon. Physical and mechanical properties and colourimetric parameters of ayous wood were determined following the UNI EN and ISO standards to characterize this wood and to compare with the data from literature. Density, 393 kg/m3, resulted consistent with the data reported in the literature; the basic density was lower than those reported in the literature and the difference could be related to wood porosity; volumetric shrinkage was among the lower ones detected by other authors. Colourimetric parameters describing the undifferentiated creamy-yellow colour of the wood were L* 73.08, a* 7.39, b* 27.88. Mechanical properties were in the wide range of data reported by other authors; compression strength 36.6 MPa, static bending strength 61.1 MPa and Brinell hardness 12.2 N/mm2. These results extend our knowledge on the physical, colorimetric and mechanical properties of the ayous wood. These results can be helpful to highlight differences in the physical and mechanical properties due to the influence of origin on wood physical and mechanical properties. Future studies on this topic are needed to better understand the changes in properties and the characterization of the Cameroonian provenance. The results on the properties of ayous wood give an account of the real possibilities of treatments and technologies that can improve the technological characteristics and the environmentally sustainable use of this resource for the origin and importing countries.

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Long-term impact of selection cutting management on frequency of stem deformity in mixed beech forests of northern Iran

Tavankar Farzam, Nikooy Mehrdad, Lo Monaco Angela, Picchio Rodolfo

Drewno : prace naukowe, doniesienia, komunikaty

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2021

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vol. 64, nr 207

5--26

EN

The aim of this study was to evaluate the long-term effect of selection cutting management on the stem quality of the trees remaining in the forest. For this purpose, three parcels managed for three decades by selection cutting were selected as managed stands (MP), and two protected parcels without tree felling as control stands (PP). First, the frequency of deformed stems in each parcel was determined for a circular 1000 m2 area of each plot by systematic sampling of 100 m × 100 m grid sections, and then a stem deformity index was estimated for each of the deformed stems. The results showed that the frequency of stem deformity in MP (6.5%) was significantly lower than in PP (20.7%) (p < 0.01). In addition, the frequency of all types of stem deformities in MP was significantly lower than in PP. Furthermore, selection cutting management reduced the indices of twisting, decay, conicity, forking, and ellipticity by 58.4%, 53.9%, 34.7%, 8.4% and 6.8%, respectively. The results for the correlation between frequency of stem deformity and tree diameter at breast height (dbh) showed that the curves followed a parabolic shape in both MP (r = 0.83) and PP (r = 0.80), where the frequency of deformed stems decreased with increasing dbh (up to 75 cm in MP, and up to 65 cm in PP), and then increased with larger dbh. Selection cutting management, regardless of tree species, improved the stem form. Decay accounted for a high proportion (24.1%) of the total deformity in MP, mainly due to logging damage. Overall, the results of this study show that selective management has been successful in improving the quality of tree boles in the studied mixed beech stands. Regular and long-term stand monitoring and statistical quality control (SQC) may be a good approach to aligning ecological and economic goals in forest management.

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Influence of thermal treatment on selected properties of chestnut wood and full range of its visual features

Lo Monaco Angela, Pelosi Claudia, Agresti Giorgia, Picchio Rodolfo, Rubino Gianluca

Drewno : prace naukowe, doniesienia, komunikaty

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2020

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vol. 63, nr 205

5--24

EN

The use of chestnut wood (Castanea sativa Mill.) is highly relevant in Central Italy, as it is one of the most important and abundant broad-leaf species in this geographical area. The comprehension of the modifications induced by thermal treatment is of crucial importance to define the optimal temperature that could improve the mechanical and physical properties without affecting significantly the visual appearance. In this paper a careful and complete investigation on the effect of thermal treatment on chestnut wood (Castanea sativa Mill.) is reported. The aim of this study is addressed to understand the chemical-physical modifications occurred on the surface of wood samples, as a consequence of heating, in order to choose the most suitable temperature of treatment, also in the view of applying a possible coating. No such complete and homogeneous study on chestnut wood was found in the literature, so this paper contributes to add relevant scientific and technological information on it. Samples of chestnut were thermally treated 6 hours in a conventional oven at 140°C, 170°C and 200°C. Surface properties of heated wood, in comparison with untreated, were evaluated through the measurements of: roughness, colour, Vickers and Brinell hardness, surface profile and contact angle. The behaviour of earlywood and latewood was evaluated by studying separately the effect of heating on contact angle and surface micro- -hardness. Fourier transform infrared spectroscopy was also used to evaluate the chemical modification of wood components due to thermal treatment. Heating at 140°C has little influence on wood characteristics whereas 200°C has a great impact on colour, mechanical properties and hydrophobicity behaviour. The intermediate temperature, i.e. 170°C, seems to give the best results in term of improved mechanical properties and also aesthetical appearance of wood surfaces.

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Wound healing rate in oriental beech trees following logging damage

Tavankar Farzam, Picchio Rodolfo, Lo Monaco Angela, Nikooy Mehrdad, Venanzi Rachele, Bonyad Amir Eslam

Drewno : prace naukowe, doniesienia, komunikaty

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2019

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vol. 62, nr 203

5--22

EN

Beech is the most important commercial species in the Caspian forests of Iran. Selective cutting and harvesting methods may adversely impact the quality of the residual trees, as the injuries make the trees prone to future disease, insect infestations or timber defects. Although attempts to better understand how wounds affect the residual trees have been made in many different contexts, there are still few investigations on uneven-aged forests. In this study the key objectives were to determine and model the healing rate for different wound parameters (width, length, and area of wound); to analyse the relationship between wound healing rate (WHR), tree diameter growth and tree height growth; to analyse the WHR in relation to wound position on the stem; and to analyse the relationship between WHR, width and area of wound in DBH classes and social classes, with the aim of enabling the prognosis of logging wounds. Wounded beech trees were examined immediately after selective logging and after a 5-year period. The WHR was 31.2 ±7.7 cm2 year-1. The wound width healing rate (18.4 ±3.4 mm·year-1) was significantly higher than the wound length healing rate (4.5 ±1.6 mm·year-1). Only 12% of wounds were completely closed after a 5-year period, and 15 years are necessary for the complete closure of 80% of total wounds. The ratio of wound area to stem area at wound height (RWS) showed a more pronounced effect on diameter than on height. Regression analysis showed that WHR was correlated negatively with wound area and width and positively with tree diameter growth, but no significant relationship was found between height growth and WHR parameters. The WHR was significantly higher at an upper position than at a lower one, and statistical tests showed that the tree vertical layering classes had a significant effect on WHR. Finally, it was shown that WHRs in upper-storey trees are significantly higher than in the middle and lower storeys.