Journal of Wood and Forest Science and Technology
Year:2019 | Volume:26 | Issue:3|Papers Count:8

Background and Objectives: About 60, 000 tons of printing paper are annually produced from bagasse in Ahvaz Haft-Tapeh Pars factory. In this factory, bagasse soda pulp was already bleached with the CEH sequence and is currently bleached with the EH sequence (alkaline extraction (E) and hypochlorite (H)). The chlorination stage (C) due to consistency of the pulp (about 3%) and the production of large amounts of effluents and absorbable organic X-halide (AOX) of lignin is significantly important in terms of the environment. Therefore, in the Pars factory and in conventional global systems, the chlorinated (C) stage and some of the bleaching sequences with chlorine compounds such as hypochlorite (H) and chlorine dioxide (D) are eliminated and instead of them are used oxygen (O), ozone (Z), hydrogen peroxide (P), disodium hydrosulfite (Y) or a combination of them as a totally chlorine-free (TCF) system. Therefore, this study was conducted to evaluate the effect of bleaching on optical and mechanical properties of paper from bagasse soda pulp using TCF method. Materials and Methods: In this research, the unbleached soda pulp of bagasse (before the bleaching) was randomly selected from the Ahvaz Pars factory. Then, the selected pulps were bleached with 1, 2, and 3 step sequences of P, OP, OPY, and O(Ep)P using the oxygen (O), hydrogen peroxide (P), and also alkaline extraction by hydrogen peroxide (PE) and di-sodium hydrosulfite (Y). Hand-sheets with a basic weight of 70 gr/m2 were prepared from the pulp. After that, theoptical and mechanical properties of the samples were measured according to the TAPPI standard test methods and then the paper properties were compared. Results: The results showed that some properties such as the brightness, greenness, tear strength, tensile, burst, tear length, and folding strength were increased due to bleaching by totally chlorine free (TCF) method. On the other hand, the opacity and a* factor of papers resulting from bagasse soda pulp were decreased. In the current study, hydrogen peroxide as an oxidative bleach had an effective role in improving the greenness, tear strength, tensile, tear length, and folding strength. However, no significant effect was observed on improving the made paper brightness compared to the control sample (EH sequence of Factory). Furthermore, statistical analysis results showed that there are significant differences at 1% level between the averages of the optical and mechanical properties of the modified pulps. Conclusion: In general, the role of the three-stage bleaching sequences of OPY and also the two-stage bleaching sequences of OP were more effective in bleaching of the pulp and improving the brightness and strength of the made papers compared to the two-stage sequences of EH (control) and unbleached bagasse soda pulp of the factory.

Background and Objectives: Mechanically isolated cellulose nanofibers (MCNF), bacterial cellulose nano-fibers (BCNF) and chitin nanofibers (ChNF), as nano-polysaccharides, have attracted much attention of researchers during two past decades due to biocompatibility, good barrier (barrier properties against water vapor, oxygen, and etc. ), high mechanical properties as well as low cost of their raw materials. Non-thermal plasma treatment (cold plasma) is an effective way to modify the surfaces of a wide variety of materials. In this study, the effect of cold plasma on the physical and mechanical properties of three types of nano-papers prepared with MCNF, BCNF and ChNF were studied. Materials and Methods: To study the effect of cold plasma on mentioned nano-papers, four plasma treatment times of 0, 3, 6, and 9 minutes have been selected as variables. WCNF, BCNF and ChNF in gel form were prepared from Nano Novin Polymer Co. (Iran). To produce nano-paper from different nano-fibers, vacuum filtration method was used. Morphological properties of nano-paper were determined by scanning electron microscopy (SEM). Water vapor permeability (WVP), solubility in water, surface color of papers, transparency and the mechanical properties of fabricated nano-papers were investigated. Results: Scanning electron microscope (SEM) images showed that the average diameter of MCNF, BCNF, and ChNF nano-papers were 35, 48, and 26 nm, respectively. Plasma treatment increased the whiteness of specimens. As the result of plasma treatment, WVP decreased at lower treatment time (3 min), while this property increased within treatment time over 3 min. Plasma did not have considerable effect of water solubility of specimens. The specimens treated with 3 min showed the highest transparency. All treated specimens showed less mechanical properties compared to the control one. Conclusion: In general, plasma could improve the properties of nano-papers at lower treatment time while longer treatment times had negative effect on specimens’ characteristics.

Background and Objectives: Cellulose is a high-strength natural polymer per unit weight and is the main building material of plant fibers. Many properties of the cellulose depend on the chain length or degree of polymerization, the ratio of the amorphous to the crystalline segments, as well as the crystal structure. While harsh chemicals or mechanical treatments are used in many nanocellulose extraction methods; cellulose is obtained with pristine properties but nanometer-sized by only very limited methods that bacterial nanocellulose is the most important of them. Bacterial nano-cellulose (BNC) due to special microscopic structures has a high potential in special uses (such as medical and sanitary applications). BNC differs from plant cellulose in its higher purity, crystallinity, and degree of polymerization. The goal of this study was to investigate the production of BNC using Acetobacter xylinum bacteria and its characteristics evaluation. Materials and Methods: In order to obtain BNC in this research, the bacterium was cultured in a liquid culture medium under static and dynamic conditions and the resulting cellulose was washed and purified. Microstructures with field emission scanning electron microscopy (FE-SEM), crystallinity structure by X-ray diffraction (XRD), weight percentage, size and distribution of BNC with energy-dispersive X-ray spectroscopy (EDX), determination of viscosity and molecular weight by dissolving of cellulose in copper(II)-ethylenediamine complex (CED) solution, and BNC yield by weighing wet and dry samples were studied. Results: The results showed that yield of BNC static culture medium is more than BNC dynamic culture medium. Comparison of FE-SEM images showed that the culture method has a significant effect on the morphology structure of the BNCs fibers produced. Comparison of FE-SEM images of two culture methods showed that the morphology of BNC in static cultivation is porous and in dynamic is clustered together. The size of nanoparticles is generally below 60 nm for both BNCs. The results of XRD test showed that the crystallinity of BNCs in the static and dynamic medium was 72. 49% and 14. 29%, respectively. Also, viscosity of BNCs in the static and dynamic medium was 110. 7 centipoise (cP) and 97 cP, respectively. Conclusion: In general, with respect to characteristics of BNC produced and comparison with other studies, we concluded that suitable BNC has been produced in this study that with respect to research needed in this field in the country and medical applications and engineering are important.

Background and Objectives: Wood is a natural material used in the construction of various wooden structures. Wooden structures are weathered and surfacely damaged by outdoor exposure. Regarding the use of wood as outdoor furniture, floorings, parquets and wooden wallboard in wooden houses, some properties such as hardness, scratch resistance, and abrasion are important. In this study, the effect of accelerated weathering on the abrasion resistance of Populus nigra, Fagus orientalis and Quercus castaneifolia was studied. Materials and Methods: For this purpose, wood samples were cut to standard dimensions of 2×10×15 cm (L×R×T) and the surfaces of wood samples were coated with linseed oil (100 ml\m2). The coated samples were kept in an accelerated weathering machine for 2 weeks and then, by Taber test and Confocal laser microscope, the abrasion resistance and topography of the wood surfaces before and after weathering were investigated. Results: The results of this study showed that, due to weathering, the wear resistance of all wooden species decreased and the most resistance among them was related to oak with the weight loss of 1. 7 grams. Also, the results showed that the amount of abrasion index reduced by 28, 38, and 18 percent for poplar, beech, and oak, respectively. The lowest and highest abrasion resistance after weathering were related to the poplar and oak and the results of the confocal laser scanning microscopy showed that, in the poplar, beech, and oak the abrasion depth was 201, 183, and 136 (μ ), respectively. Conclusion: The increase in oak wear resistance to other species can be due to higher specific gravity. The use of linseed oil coating reduces water absorption, on the other hand, reduces friction and makes the surface of the wood lubricate. In addition, the increase in weight loss after weathering is due to the higher absorption of uncoated samples than the coated samples, which causes faster and easier destruction of the wood structure. Based on the results of the laser microscope and wear depth study, the coating with linseed oil has been able to reduce the wear depth and increase the wear resistance. According to the results of this study, linseed oil can be used to increase the resistance of wood structures to abrasion.

Background and Objectives: Measuring tree height in forest is time and cost-consuming especially in vast areas. Therefore, using digital aerial images are proposed. The main objective of this research is evaluating capability of such images for estimating trees height. Materials and Methods: This research was done based on nine UltraCam-D aerial images with 70% end lap overlay and 60% side lap, 7 cm pixel size and scale of 1: 8000 in Taleghani Park of Tehran. The images were geometrically corrected using aerial triangulation method and then digital elevation model (DEM) and digital surface model (DSM) were produced using LPS and INPHO software respectively. Then trees height was estimated by the difference between the two models. To estimate the accuracy of DEM, the elevation of 15 points from the 1: 1000 topographic map of Tehran were extracted and compared with the DEM elevation values at the same points. After that, calculating 101 trees height, were performed by subtracting values of DSM and DEM for each tree. To check the precision of calculated height, heights of these trees were measured by Suunto in the field and were compared with the estimated height. The trees include various species of conifers and deciduous. Comparison of estimated heights (calculated) with ground values (measured heights) was performed using simple linear regression and, R2, RMSE and RMSE%. The pairwise T-test was used to compare height differences in two groups of broad-leaved and needle-leaved trees. Results: Due to the RMSE value based on the five control points (0. 22 pixels), and the exact correspondence of the corrected images with the topographic map, the reliability of the geometric correction was obtained with acceptable accuracy. The low density of forest cover in the studied area allowed the ground to be seen in the images. This point made it possible to select the right control points and the number of node points. Achieved results, high linear correlation between actual height value and calculated height (R2=82%), RMSE (1. 35 m) and insignificant average difference between calculated and actual height (1. 13 m) indicate that estimated height based, has acceptable accuracy. In addition, no significant difference was observed between precision of estimated conifers and deciduous height. Conclusion: Based on the results, this approach can be used operationally to determine height of the trees in relatively flat areas such as urban forests and flat Zagros forests but its capability should be investigated at mountainous areas, high density and high-slope forests.

Background and Objectives: In recent years, Zagros, as the largest forest ecosystem in Iran, have been affected by the oak decline phenomenon. Oak decline can occur simultaneously in different geographic regions by completely different or identical stressors and lead to the death of oak trees. Tree mortality decreases both forest quality and quantity and has a negative effect on the ecosystem performance by decreasing the density of the stand, changing the abundance of tree species, reducing the canopy cover and changing the structure of the forests. Therefore the present study was carried out with the aim of determining the relationship between some tree characteristics, forest stand and physiographic factors with the rate of dieback. Materials and Methods: In 50 hectare of this forest by a random systematic grid (100*100) 42 circular sample plots with 1500 m2 area were selected. The layers of slope in two categories, aspect, and altitude in two categories were prepared. In each sample plot the structural characteristics of stand such as; diameter at breast height, Crown area, Crown density (open, medium, closed), tree height, number of sprouts, tree origin, tree position, and dieback rate (in four classes including healthy: less than 5%, poor crown dieback: 33-5%, average crown dieback: 66-34%, severe crown dieback: more than 66%) were measured and recorded. Results: The results showed that the relationship between dieback rate with trees origin, tree height, and stand density was significant. However, there was no significant relationship between dieback rate and the diameter at breast height (DBH), the number of sprouts and crown area (canopy). The trees located on aggregated group had the higher rate of dieback than individual trees. The relationship between physiographic factors with dieback rate showed that there was no significant relationship between slope and dieback. The rate of dieback in southern aspect and in higher elevations was higher. Conclusion: Most of the diebacks belong to the 4th and 1st classes. If the current trend along with frequent droughts continues, the trees are transferred from lower classes to higher classes. In such a situation it is impossible to restore the forest to the natural state, but if escalating factors are managed and human intervention is controlled in the nature, the current situation can be kept constant, or even given the evidence of the presence of sprout shoots, it is hoped to restore the forest.

Background and Objectives: The spatial distribution of Iranian oak trees plays an important role in the dynamics of the western forests ecosystems of the country and their optimal management. In general, the spatial distribution of phenomena is divided into three random, regular and clumped modes. The forest has two horizontal and vertical structures. The horizontal structure of the forest is surface distribution of trees in the forest area and the vertical structure is the height distribution of trees in the forest stand. One of the important characteristics of forest stands is the horizontal distribution of trees. Iranian oak is one of the main species of Zagros forests. Therefore, understanding the distribution pattern of this species can be one of the important factors in preserving, rehabilitating and developing forests of the region. Materials and Methods: In line with this research, the area of 30 hectares was selected from Olad-Ghobad forests in the west of Lorestan province, in Kohdasht city. To conduct field operations each hectare of the study area was selected as a 1 ha sample plot in which, based on the complete sampling, the diameter of each tree was measured. Then, by determining the initial station at the surface of each sample plot and measuring its geographical coordinate using the GPS, the coordinates of all oak trees were determined by measuring the azimuth and distance of the trees from the initial stations based on Cartesian trigonometric calculations. Then the measured trees were divided into three diameter classes of low, medium and high diameter. Investigation of spatial pattern of Iranian oak trees was done using one-variable function of O-ring statistic. Results: The results showed that the spatial pattern of the trees due to the creation of the coppice shoots and sprouts and also the higher density of coppice forests in comparison to high forests at short distances from the base tree (usually 20-25 m) is clumped, and then with the scale enlargement in some geographic directions (north and northwest directions) is regular due to the human interventions and the removal of regeneration by livestock grazing. Conclusion: Considering that in most of the studied area, the distribution pattern is cluster therefore management plans and forestry interventions should be oriented so that the pattern of distribution is driven towards the cluster pattern. The results can be useful in designing planting patterns.

Background and Objectives: Nutrient cycles in forests are tightly linked to the hydrological cycle because water acts as the main solvent and transporting agent for nutrient from the aboveground tree canopy to the underlying soil. The aim of this research was to evaluate the monthly and annual changes in chemical properties (calcium, sodium and potassium) of the canopy and litter leaching of hornbeam (Carpinus betulus L. ) trees during a year compared to nutrients in rainfall (RF). Materials and Methods: This study occurred from January 2012 to February 2013 in a mixed natural stand at Shastkalate Forest Research Station of Gorgan University of Agricultural Sciences and Natural Resources. In a 5000 m2 area in the study site 3 healthy trees with free and symmetrical crown and stem were selected for sampling of RF, throughfall (TF) and litterfall (LF) chemistry. RF, TF and LF were sampled after each rainfall within a year. The collectors were emptied after each rainfall (as soon as rain ceased) and were thoroughly rinsed with deionized water and dried before being replaced. To analyze the chemical content of RF, TF and LF, samples were transported to the laboratory of Gorgan University of Agricultural Sciences and Natural Resources and stored at 4 º C. The concentrations of sodium (Na+), potassium (K+) and calcium (Ca2+) were determined using flame photometer. In order to compare amount of nutrients in TF and LF with RF and to investigate monthly nutrient dynamics of TF and LF, t-test analysis and the one way variance analysis were used. Results: Results showed that Na+ amount in TF (116. 37 kg ha-1year-1), and K+ and Na+ amounts in LF (158. 45 and 78. 79 kg ha-1year-1 respectively), were significantly lower than K+ and Na+ (217. 72 and 172. 82 kg ha-1year-1) in RF (P<0. 05). Also amounts of nutrient leaching of TF and LF in various months were different significantly. The highest leaching amounts of Na+, K+ and Ca2+ were observed for TF, 24. 51, 58. 30 and 3. 14 kg. ha-1, respectively. However highest amounts of Na+ and Ca2+ were measured in October for LF; 19. 93 and 4. 17 kg. ha-1, respectively. Also the lowest leaching of Na+, K+ and Ca2+ of TF (0. 84, 3. 22 and 0. 15 kg ha-1 respectively) and LF (0. 45, 0. 52 and 0. 03 kg ha-1 respectively) were measured in September. Conclusion: In this complex process, in crown cation exchange, the absorption tendency of hornbeam crown was higher than its cation diffusion from leaf and branch tissues, so hornbeam crown tends to absorb nutrition from RF to meet its nutrient need.