فصلنامه جنگل و فرآورده های چوب
سال هفتاد و سوم شماره 1 (بهار 1399)

Wood coating with clear coats such as polyacrylate have a short service life since solar radiations pass through the coat and cause subsequent discoloration of wood surface. These phenomena can be decreased by using suitable UV absorbants in the coats. Therefore, in this research, olive leaf extract in combination with nano-particles of titanium dioxide (TiO2) and zinc oxide (ZnO) were added to the polyacrylate coat as the substrate to study the possible effects of different formulated coats on surface properties of the thermally modified wood after exposure to the natural weathering for a long period. The surface properties of the coated wood such as color change, surface roughness and wettability of the coated wood were studied during the weathering period. The microscopy was carried out on the coated wood to evaluate any morphological changes of wood surface as well as any mold growth. The results showed less color changes in the coated thermally modified wood. Also, surface roughness increased due to the weathering in all coats. However, roughness increased in all samples including control and treated ones, showing the highest roughness in uncoated samples. The result of contact angle showed that the polyacrylate coated samples kept their low wettability during the weathering periods. However, the wettability was increased in the control samples. It could also be concluded that olive leaf extract caused less mold growth and less color changes due to its anti-oxidant and bioresistance properties.

Historical documents represent the national, religious, and artistic values of each nation and are its historical identity. Understanding factors that make up a paper can help to identify past cultures and maintain true techniques. One of the oldest known collection of documents of the Islamic period of Iran is the Sheikh Safiuddin Ardebili monument's documents which despite its unique historical values, has not been thoroughly studied in terms of technical knowledge of its constituents. In this study, in order to identify the type of used fibers, liner, and filler in the paper, colorimetric identification, optical microscopy, and scanning electron microscopy equipped with X-ray diffraction spectroscopy (SEM-XRD) were used. The results showed that flax and hemp fibers were used in the fabrication of the specimens and only in three specimens, the ramie fibers were observed. In addition, the results of the pulp identification indicated that the pulp used in the study samples was of an old fabric type that was made by hand. Based on the liner identification test, it was found that the liner in the samples was polysaccharide (starch) and the fillers in the samples were calcium carbonate, gypsum and kaolin.

The objective of this study was to investigate the production of bisulfite pulp from Carpinus betulus species to enhance the strength properties of the chemical mechanical pulp (CMP). CMP pulp prepared according to the industrial standards (Mazandaran wood and paper industry) and bisulfite pulp was prepared by direct injection of sulfur dioxide (SO2) gas into a sodium hydroxide solution. The results of cooking bisulfite pulp showed that by increasing of cooking time from 1 to 3 hours the kappa number decreased. The results of mixing bisulfite pulp (10, 30 and 40%) with CMP pulp showed that the mechanical properties of the paper improved with increasing the contribution of bisulfite pulp. By adding 40% bisulfite to CMP, the tensile index, burst index, tear index and folding strength improved by 24%, 16.2%, 13.7% and 84.2%, respectively. Finally, combining 40% bisulfite pulp and 60% CMP pulp showed the highest strength in terms of total paper properties. Therefore, the use of bisulfite pulp up to 40% mixed with CMP paper pulp leads to the desired production of newspaper and is recommended.

Light weight, good thermal and sound insulation, easy installation, high strength and low price are characteristics of sandwich panels that have found numerous applications in industry and construction today. In this composite two thin faces enclose a thick core layer that resists shear forces, which can be made of wood or wooden products. In this work, the improvement of the sandwich panel strength was investigated through changes on the material and cross-sectional shape of the core layer made from waste paper with square hollow shape. For the fabrication of the samples, it was necessary to design and manufacture a metal mold to form raw materials with specific ratios and hollow shaped. Different quantities of crushed paper with specified dimensions and two types of common resin in wood composites industry were used to prepare the core layers. The square honeycomb cores were sandwiched between the face layers from medium density fiber board. The first results of this study showed that compressed waste paper in the form of a core layer was an acceptable function in the structure of a lightweight sandwich panel. The density of the paper core had a significant effect on the improvement of flexural strength, which increased with increasing density. In addition, the type of adhesive had a significant effect on the flexural strength of the sandwich panel. Phenol formaldehyde adhesive further improved flexural strength, compared with the urea formaldehyde.

Topochemical engineering of fiber surfaces is an attractive strategy to fabricate a product with desired surface properties especially by using reactions with organic molecules in aqueous medium. In this study, the bagasse soda pulp was treated with carboxymethyl cellulose (CMC) in order to introduce more charged groups on the surfaces of fibers. The carboxymethylation of fiber surface was carried out under temperatures of 85, 95, and 120°C at 60, 90 and 120 minutes in the presence of calcium chloride as an electrolyte. The drainage time, water retention value (WRV), tensile index, and burst strength of CMC-modified pulps were measured and compared with corresponding values of untreated pulp and CMC-treated pulps by conventional methods. The results indicated that the treatment of fibers with CMC markedly increased the tensile index and burst strength of the modified pulp hand-sheets in comparison with unmodified pulp ones. The maximum strength properties were achieved at the reaction conditions of 120 ᵒC and 90 min between fiber and CMC. However, drainage time was not impaired by modification of the pulp. Water retention value of CMC-modified pulps decreased unexpectedly in some conditions. Further characterization using FTIR spectroscopy and XRD demonstrated hydrogen bonding development and a slight decrease in crystallinity due to fiber modification process. It is concluded that introducing acidic groups via topochemical modification of bagasse fiber surfaces may influence the most properties of the final pulp.

Nowadays, using of fiber reinforced plastic (FRP) rods in composites structures has been increased due to their light weight and high specific strength. In this research, the behavior of steel and glass-FRP rods with different surface patterns (plain, ribbed) were experimentally investigated in the points of bonding length (200, 300 mm) and adhesive type (unsaturated polyester, epoxy) view, parallel to poplar (Populus alba) wood grain. In this regards, after specimens preparation based on the above mentioned situations, tensile pull-out strength, shear stress, as well as failure modes in wood-adhesive and rod-adhesive interfaces were investigated. The maximum value for poll-out strength, i.e. 82.5 kN was achieved for ribbed glass-FRP rods, and 300 mm anchorage length. In addition, while pull-out load carrying capacity increased with increasing bonding length, nominal shear stresses were decreased from 6.8 to 3.8 MPa, and 8.9 to 4.7 MPa, respectively for wood-adhesive, and rod-adhesive interfaces. Worth noting, the most common failure mode was pull-out of rods with attached wood, due to shear failure parallel to the wood grains.

In order to investigate the factors affecting damage caused by early snow in the compartment no. 10 in Patom district of Kheyrud forest research station, the sampling was conducted on a random grid (100 × 100 m) with 46 m 1000 circular sample plots. In each plot, effective factors including slope gradient of the plot, aspect, altitude (elevation), soil depth, diameter at breast height, and height of all tree species greater than 7.5 cm were recorded. Damages to trees were classified into four types including uprooting (tree throw), trunk fracture, crown fracture, and bending. The results showed that 28.1% of the trees were damaged, with damage of 3, 4, 10 and 11% for each type including uprooting (tree throw), trunk fracture, crown fracture, and bending, respectively. The results showed that there was a significant difference between the types of tree damage and some factors including aspect, slope, elevation, and soil depth. The highest percentage of tree damage occurred in the northern aspect, slope less than 15%, altitude of 330-380 m, and shallow soils depth, and the lowest occurred in the southern aspect. The damage on the eastern and western slopes was approximately similar. The highest and the lowest percentages of damage were related to alder and maple tree species, respectively. Thinning treatments affected the horizontal and vertical structure of the stands by reducing the slenderness coefficient of trees, which has a key role in reducing the severity of snow damage on trees, and improves tree and stand stability.

Beech trees is one of the most important species of Hyrcanian forests that plays an important role in the process of forest ecosystem succession and the ectomycorrhizal fungi play an important role in forest health and sustainability and protecting trees against pathogens in forest ecosystems. This study was conducted to classify beech habitat with environmental factors and ectomycorrhizal fungi in Sangedeh forest. A total of 45 sample plots of 1000 square meters were randomly assigned to three 300 m altitude classes, namely altitude range of 1200 to 2100 m above sea level and elevation factors (m), slope, slope direction, breast diameter, tree height, Degree of canopy cover, litter type, litter depth, stand type, soil acidity, electrical conductivity, phosphorus, carbon, nitrogen, potassium were investigated. The results of correlation of variables with components were determined and ectomycorrhizal fungi with first principal component included variables such as altitude, nitrogen, potassium, phosphorus, carbon, electrical conductivity and tree height and the second principal component of altitude variables, canopy cover, depth Litter, nitrogen, carbon and stand type had a significant positive correlation (1%). Principal component analysis results showed that first floor height (1800 to 2100 m) with sea level elevation, soil acidity, litter depth, phosphorus and potassium, second floor height (1500 to 1800 m) with forest cover canopy percentage, litter depth There was a positive correlation between mass type, nitrogen and carbon and height of third class (1200 to 1500 m) with stand type, tree height and electrical conductivity.

Fire severity mapping is very important for managing the fires in forest ecosystems. The extraction of spectral indices from optical sensors is recognized as one of the most effective bands for the classification of vegetation classes. In this study, the ability and sensitivity of some spectral indices extracted from Sentinel-2 and Landsat 8-OLI images with different spatial resolutions have been investigated for fire severity mapping using the Random Forest algorithm in a burned area located in the reforested area of Arabdagh, Golestan province. After necessary preprocessing on the bands, the appropriate mono and bi-temporal spectral vegetation indices were created. The optimal index values for bands in the bi-spectral spaces pre/post-fire were calculated to evaluate the sensitivity of bands to the changes occurring within the fire classes. The best results were obtained for the NIR-SWIR2 bands with an optimal index value of 0.77 for Sentinel-2 and 0.67 for Landsat8-OLI. The best indices were selected based on values of optimality index. The values of these indices were calculated after the fire as well as the differential (pre/post-fire) ones. The ground truth of fire severity classes map was prepared by a selective sampling method through field surveying. The classification was done with different indices by random forest (RF) algorithm and the results were assessed by the ground truth points. The result showed that the best results were obtained for a combination of many differential indices from all bi-bands of Landsat 8-OLI with kappa coefficient (0.96).

Achieving the goals and implementation of sustainable forestry requires accurate data in order to do necessary planning and provide optimal solutions. The aim of this study was to select the optimal sample plots size and shape for estimating stand volume and tree density in Arabdagh forests, Golestan province. For this purpose, 60 ha forest area of Arab Dagh in Kalaleh city was surveyed with 100% inventory. Then, stand volume and tree density were calculated form 100% inventory and all sample plots with areas of 200, 400, 600, 800 and 1000 m2 and circular and square shapes were calculated in a Systematic Random Sampling. Also, the results were compared with stand volume and tree density obtained from 100% inventory using one-sample t-test. The results showed that the E% (square of sampling error) difference between circular plot (1.9%) and square plot (1.2%) with 400 m2 area plot is very low. Moreover,  index of circular plot (89604) and square plot (94979) with the area of 400 m2 are lower than the 1000 m2 area plot. Therefore, sample plots with the area of 400 m2 are appropriate for stand volume and tree density. Also,  index of circular plot with the area of 400 m2 is lower compared with the square plots with the same area and the differences between them are also lower. Therefore, circular plots are appropriate for stand volume and tree density. In general, the results showed that circular sample plots with the area of 400 m2 can be optimal sample plot size and shape in afforestation inventory.