فصلنامه پژوهشهای علوم و فناوری چوب و جنگل
سال سی‌ام شماره 4 (زمستان 1402)

Wood plastic composites are produced of mixing thermoplastic polymers with organic, inorganic and natural fillers. The incompatibility of natural fillers with the non-polar polymer matrix results in weak adhesion at the interface of wood fibers with polymer and lack of stress transfer from the polymer to the wood fibers, which leads to a decrease in the mechanical and physical properties of the resulting product. Based on previous researches, in addition to using coupling agents to improve the adhesion between fibers and polymer matrix, modification of natural fillers can also improve the properties of wood-plastic composite products. In this research, the effect of chemical modification of lignocellulosic fillers with glycidyl methacrylate and methyl methacrylate on the functional properties of polypropylene wood plastic composite were investigated. Poplar wood flour was modified with glycidyl methacrylate (GMA) and combination of glycidyl methacrylate/methyl methacrylate (GMA/MMA) under argon gas and the changes in chemical structure, thermal stability and physical properties of control and modified flours were evaluated. Samples of wood plastic composites made using control flour and polypropylene in weight ratios of 80:20, 70:30 and 60:40%, without and with MAPP, and flours modified with glycidyl methacrylate and glycidyl ethacrylate/methyl methacrylate in the same weight ratio of mixing by injection molding method. Physical properties of composites according to ASTM standard D 570 and morphology using field emission scanning electron microscope images was evaluated. Based on the findings of this research, modification with acrylate compounds including: glycidyl methacrylate and methyl methacrylate, by changing the chemical structure, created a significant improvement in thermal stability and physical properties of wood flour. Based on the FTIR results, the chemical changes of wood flour by combined modification of glycidyl methacrylate/methyl methacrylate under benzoyl peroxide were more obvious than the glycidyl methacrylate due to the polymerization of methyl methacrylate. With increase of natural filler ratio, the water absorption of the product increased. The wood flour modification with glycidyl methacrylate as a bifunctional agent improved the adhesion and compatibility of methyl methacrylate polymer with the cell wall of wood flour. The reaction of the cell wall with glycidyl methacrylate reduced the moisture absorption potential of the cell wall by changing the structure of holocellulose and reducing the hydroxyl groups, and the physical properties of the resulting product were improved by increasing the compatibility of the flour with methyl methacrylate and the matrix. In comparing modification of glycidyl methacrylate with glycidyl methacrylate/methyl methacrylate, combined modification by creating a more uniform structure and better compatibility between components, created a more noticeable improvement in physical properties of composite compared to cell wall modification with glycidyl methacrylate, and this effect became more noticeable with increasing filler ratio.

Carbon materials bearing advantages such as chemical and thermal stability, electrical conductivity, high specific surface area, and high porosity are widely used in electrode materials. Although the utilization of wood-based carbon materials in electrochemical energy storage devices has good capacitive behavior and it increases charge storage, wood does not show sufficient electrical conductivity due to the inadequate electrical conductivity as a carbon electrode. In order to boost its performance, composites of carbon materials have been synthesized with other conductive materials. In this study, the physicochemical and electrochemical properties of nanocomposite electrodes based on carbonized wood/ Mn-MOF, prepared by the in-situ synthesis method, were assessed. Furthermore, the Performance of these electrodes as the cathode in sediment microbial fuel cells was investigated. Its performance was compared with control wood-based and commercial carbon felt electrodes, too. The sapwood blocks of Platanus orientalis as lignocellulosic precursor were pyrolyzed at a temperature of 700 °C and a heating rate of 5 °C min-1 in the argon atmosphere with a constant flow of 100 mLmin-1 and a retention time of 1 h. After pyrolysis, the carbonized wood samples were washed with distilled water and dried in an oven. Then, to synthesize composite electrodes of CW/ Mn-MOF, manganese (II) acetate tetrahydrate, and 1,3,5-benzene tricarboxylic acid ligand were used. Finally, the samples were washed with ethanol and dried in the oven. Secondary pyrolysis was performed at 900 °C for 2 h in an argon atmosphere and a heating rate of 5 °C min-1. The results of this study showed that after wood pyrolysis, morphologically, the porous structure and its connected and direct channels were preserved. In addition, in-situ synthesis of Mn-MOF on carbonized wood was successfully performed. According to Raman spectra, the increase in the degree of disordering in the structure of prepared nanocomposite electrodes compared to control carbonized woods was observed. Furthermore, XRD patterns indicate the presence of amorphous and graphitic carbon in graphitic crystals of carbon. In addition, carbon electrodes doped with Mn-MOF showed the lowest impedance and the highest maximum power density compared to control and carbon felt electrodes. According to the results, high-temperature carbonization causes graphitization of wood material and yields electrical conductivity. Doping of carbon electrodes and fabrication of carbon-nanocomposite electrodes based on carbonized wood/ Mn-MOF promoted the electrochemical performance of the cathode in sediment microbial fuel cells. The synergistic effect between the pseudocapacitive behavior of Mn-MOF and the electrical double-layer capacitance behavior of carbon material improved the performance of the whole SMFC setup.

Although the main goal of seed flax (Linum usititassimum L.) cultivation is to produce seeds and extract oil from it, significant amounts of long bast fibers of this plant can be a very suitable source of long fibers used in papermaking industries. The objectives of this study were to examine the quantitative, qualitative and pulping characteristics of seed flax and to investigate the effect of planting distance on these characteristics.

This study was conducted from May to August 2015 at the UPark farm of the University of Maine, USA. The experiments were carried out using split Plot with a randomized complete block design. The main factors included 4 planting distances (9.0, 5.1, 2.2, and 4.4 cm) and the secondary factors included 3 harvest times (50, 75, and 100 days after planting). The distance between the planting rows was 4.25 cm and each plot consisted of 5 rows, each 2 meters long. At 50, 75, and 100 days after planting, the diameter and length of the stems were measured for 30 samples from each of the three middle rows of each plot. After harvesting the samples, various plant components (core, stem bast, leaves, roots, and fruit capsules) were measured and their weights and weight percentages per hectare were calculated in the laboratory. Additionally, fiber biometrics of the stem bast and core were also performed. Pulping experiments were also conducted using the bast and the whole stem with two methods SO2-ethanol-water (SEW) and soda. All statistical analyses were performed using the SPSS software, and the comparison of means was conducted using the Duncan test at the 1% and 5% levels.

The ANOVA results showed that the individual effects of different factors on the length and diameter of seed flax stem were significant at the 1% level, while their interaction was not significant. Increasing planting distance resulted in higher yields of stem, root, leaf, and fruit capsule. Despite a decrease in the percentage of seed flax stem bast from 33 to 25.4% when the planting distance increased from 0.9 cm to 4.4 cm, the overall stem yield increased significantly. The longest bast and core fibers (4700 and 608 µm, respectively) were observed at a planting distance of 0.9 cm, while the shortest (4080 and 510 µm, respectively) were at 4.4 cm. Pulping experiments from the whole stem using soda and SEW methods showed that the highest and lowest yields were 62.9% and 48.57%, respectively, at cooking times of 30 and 90 minutes in the SEW process. The ANOVA results showed that the independent effects of planting distance and stem components on the Kappa number of the resulting SEW pulps were significant at the 5% and 1% levels, respectively. The highest Kappa number (62.12) was associated with the pulp obtained from the core of seed flax planted at a distance of 4.4 cm, while the lowest (14.88) was associated with the bast of seed flax at a planting distance of 0.9 cm. According to the Duncan grouping test, no significant difference was observed between the Kappa values of the pulp obtained from the core of seed flax planted at distances of 0.9 and 4.4 cm.

By increasing the planting distance of seed flax, the yield of bast and core of stem increases. Qualitatively, the length of bast and core fibers decreases; so that the length of bast fibers is always about 8 times the length of core fibers. In terms of pulping, the Kappa and the yield of SEW pulp obtained from the bast and the core of the stem increases.

Fire is one of the climatic crises and threats to the habitats of arid and semi-arid regions, and the reduction of ecological capacity intensifies the process of desertification of these ecosystems. The reaction of species in different habitats to fire is different. Therefore, the present study investigates the effect of fire on soil properties of T. aphylla in Niatek stands, Sistan and Baluchistan province, Iran.

The statistical design was completely randomized design and sampling was done as a sample line. After surveying in the area, the stands where the fire period had passed for 10 years and control stand were selected. In each stand, area (100 × 100 m) was determined on the sides of the square and the approximate distance of 50 meters was set up from the linear sides. Then, plots with (5 × 5 m) were determined at approximately 50 m from each other (three plots on each side as a transect and 9 plots in total). After setting up the plot, 5 soil samples were collected from the four corners and the center of the plot from a depth of 0-30 cm in the month of February, and 5 samples were combined and one composite sample was obtained and were transferred to the laboratory for laboratory analysis to determine the physical properties (moisture, specific gravity,) and chemical properties (sodium, Exchangeable potassium, phosphorus, nitrogen, organic matterو electrical conductivity and acidity) were determined. The experiment and statistical analysis in the physicochemical part of the soil was done using the t-test and the non-parametric Mann-Whitney U test.

According to the results, the number of 93 and 56 trees per hectare, 11 and 25 saplings under one meter height, 2 and 30% coppice trees were observed in the control and burnt stands, respectively. Examining the physical characteristics of the soil indicated a decrease in soil moisture due to fire compared to the control, and on the other hand, an increase in bulk density in the burned stand. Also, the examination of soil-chemical properties showed that the percentage of soil nitrogen, absorbable phosphorus, exchangeable potassium and soil organic carbon in the control stand was higher than the burned stand (P≤0.05). In this study, there was no significant difference in the acidity variable between the two plots of burned and control (P≥0.05). But the electrical conductivity in the burned stand was higher than that of the control stand (P≤0.05).

According to the results, fire leads to density and regeneration changes in vegetation as well as soil physicochemical properties. Although, 10 years have passed since the fire in Thamarix aphylla Ecosystems, it could not do the necessary reconstruction and reach the edaphic and vegetation balance.

Citizen engagement in the management of urban forests has emerged as a means to enhance forest conditions and improve the overall experience of forest users. However, several factors can influence people's willingness to participate in such initiatives. Understanding the barriers and grounds for participation from the perspective of citizens is crucial for effective planning and implementation of participatory forest management. This article aims to investigate the factors influencing people's willingness to participate in urban forest management, with a particular focus on socio-economic variables, demographic groups, and the identification of barriers and opportunities for involvement. The study was conducted in the urban forests of Khorram Abad, with a sample population consisting of forest visitors. A total of 400 participants were selected using the proportional assignment method based on the Krejci-Morgan approach. Data were collected through a researcher-made questionnaire, which was validated and tested for reliability. The questionnaire explored various socio-economic variables and their relationship with willingness to participate in urban forest management. Descriptive and inferential statistical analyses were employed to examine the data. The findings indicate that, according to forest visitors, the lack of perceived impact on management programs and the absence of active community organizations are the primary barriers to citizen participation. Key areas for involvement include citizen education, waste management, and tree species protection. The recreational and aesthetic values of urban forests, as well as their positive impact on physical and mental health and air pollution reduction, were identified as crucial functions by the participants. Moreover, the study reveals variations in willingness to participate across different demographic groups. Women showed a higher inclination for participation compared to men, and unmarried individuals exhibited a greater willingness than married individuals. Furthermore, individuals who were members of environmental associations or groups and engaged with virtual environmental platforms demonstrated a stronger desire to participate in urban forest management. The duration of city residency and education level positively correlated with willingness to participate, as did the frequency of visits to urban forests. The research findings highlight the importance of considering socio-economic characteristics when designing participatory programs for urban forest management. While individuals may have different propensities for participation based on their socio-economic backgrounds, the desire to engage in forest management activities remains prevalent. City managers should therefore prioritize planning and educational-promotional initiatives to facilitate and encourage public involvement. By addressing barriers, promoting citizen education, and fostering collaboration with environmental organizations, urban forest management can be effectively enhanced through increased public participation.

Today, reforested stands are one of the most important sources of forest carbon storage and one of the factors that reduce the process of destruction of natural areas. Above-ground biomass (AGB) plays an essential role in sustainable forest management and reducing global warming and is an important source of information. Allometric equations are an important tool for quantifying above-ground biomass in forests. In recent years, remote sensing techniques using non-parametric methods such as the Random Forest algorithm have been widely used to estimate forest tree biomass. In this research, the ability of Sentinel 2 data using the random forest algorithm to estimate the above-ground biomass of Arabdagh reforested stands in Golestan province was evaluated. In this study, 180 circular sample plots with an area of 400 square meters were measured using the cluster sampling method and the diameter at breast height (DBH) and tree height (H) were measured. Also, the exact coordinates of the centers of the sample plots were recorded using DGPS. Then, using the prepared allometric equations, the above-ground biomass of trees was calculated. In this study, Sentinel 2 pre-processed radiometric and geometrical data were used, and based on that, different vegetation indices were prepared. In the implementation of the random forest algorithm, the relationship between the characteristics of biomass as a dependent variable and the spectral values of vegetation indices as independent variables were investigated. Modeling was done using 75% of sample plots (135 sample plots) with random forest algorithm and validation of estimates was done using 25% of sample plots (45 sample plots). The results showed that NDVI and GNDVI indices had the highest correlation in the estimation of above-ground biomass and the random forest algorithm with 310 trees and 5 predictors and the percentage root mean square error of 35.83% and the coefficient of determination 0.51 was able to estimate the above-ground biomass of Arabdagh reforested stands. Also, the results showed that using the data of Sentinel 2, the random forest algorithm has estimated the above-ground biomass of trees more than the actual values. There is no significant difference at the 95% probability level between the estimated and real above-ground biomass values (p-value > 0.05). Also, among the independent variables used. The results of this research showed that Sentinel 2 data has been able to estimate the above-ground biomass of Arabdagh reforested stands with acceptable accuracy. According to the results of this article, it can be said that the information of the main bands and spectral indices played an important role in the estimation of above-ground biomass.

Non-native plant species have been introduced to provide various goods and services. Some species have not shown negative effects on the ecosystem, while others cause habitat disturbances. Considering this issue, it is necessary to know these species' positive and negative effects. Paulownia is an exotic industrial tree species, and there are debates on the positive and negative effects of its plantation in forests and non-forest areas among experts and scientists. There are few studies on paulownia invasion behaviour based on the literature review in Iran. This study tries to investigate the competitive behaviour of Paulownia using scientific methods in reforested mixed stands in the educational and research forest of Shast-Kalate. Data were collected in the educational and research forest of Dr. BahramNia (Shast Kalateh) in the two areas. An area of 2.5 hectares of native species mixed with non-native species of Paulownia and another area of 2.5 hectares that only had native species (control). All trees in the study area were recorded. The measured variables for each tree include tree species, diameter at the breast height (DBH), tree height, and crown diameter. All trees with a diameter at the breast height above 5 cm are included in the surveying. The spatial coordinates of all trees were also recorded. The trees included the non-native species of Paulownia fortunei, and the native trees included Acer velutinum bioss, Acer cappadocicum Gled, and Carpinus betulus L. In order to investigate the interaction between species, bivariate O-Ring statistics and bivariate mark correlation functions were used based on distance. The independent T-statistic was used to compare the biometric variables of native species. The graphs obtained from the O-Ring statistic between Paulownia species and native species indicate that the relationships are generally of the attraction or independent type. Also, the mark correlation function results indicate negative and independent interactions based on the DBH and crown diameter and negative for tree height between Paulownia and Acer cappadocicum. Interactions between Paulownia species and Carpinus betulus in all distances were independent based on DBH and negative and independent regarding crown diameter and tree height. Also, positive, negative and independent interactions were seen regarding tree height and crown diameter between Paulownia species and Acer velutinum and attraction and independent interactions were seen in terms of DBH. The independent t-statistics indicate that the average DBH and crown diameter of the Acer cappadocicum Gled in Paulownia mixed plantation is more than the control area, there is no significant difference in tree height. The average DBH and crown diameter of Acer velutinum bioss were higher, and tree height was less in Paulownia mixed plantation compared to the control area. The tree height of the Carpinus betulus L. was higher, and the crown diameter was less in the control than the Paulownia mixed plantation. No significant differences were seen in DBH between the two study areas. Considering Paulownia's growth nature, a higher tree height, DBH, and crown diameter can be expected, and the results confirmed this. In contrast, this growth rate does not exist in native species. On the other hand, the marks used in the mark correlation function include the variables of tree height, DBH and crown diameter, so the negative marked correlation function results can be attributed to this property. In order to introduce a species as invasive, comprehensive research is needed for its effects on the regeneration of native species, composition of vegetation, and soil properties.

Fine-grained soils often have problems such as low load ability and shear resistance, difficulty in compaction and settlement. Therefore, the stabilization of fine-grained soils with additives has always been the focus of road construction engineers. On the other hand, today, the use of waste materials in soil stabilization has become common due to its economic nature. In this study, stone powder, which is the waste of stone-cutting workshops, was used to stabilize fine-grained soils.

Clay samples with low pastiness (CL) were mixed with different amounts of 0, 3, 5, 10, 15, and 20 percent of stone-cut soil compared to dry soil. 7, 28 and 90 days were taken into account for the processing time of soil and stone. In the next step, geotechnical characteristics including grain size, Atterberg limits and compressive strength or CBR were investigated. The characteristics of granulation were investigated using the sieve method, Atterberg limits using the Cassagrande and paste wick method, and compressive strength using the California loading test.

The results showed that with the addition of stone powder, the contribution of coarse soil fraction increased. So that by adding 20% of stone powder and after 28 days, more than 60% of the weight of each sample belonged to particles with a diameter greater than 0.1 mm. There was no significant difference between the processing times of 28 days and 90 days in terms of mental limit, mental index and loading capacity. However, the values of the mentioned variables were significantly different from the figures recorded in the processing time of 7 days. Adding rock powder to the soil samples decreased the flow limit and the paste index. By adding 20% of stone powder, the soil samples were transformed from pasty state (pasty index = 25) to medium pasty state (pasty index = 8). In addition, the highest amount of CBR or soil loading capacity (19%) was obtained by adding 20% of rock powder.

After 28 days, the soil samples showed the results of all the positive or negative interactions caused by the addition of stone powder, and the passage of more time has no tangible effect on the mechanical properties of the soil. Besides, in the present research, the desired changes in the mechanical properties of the soil were obtained by adding 20% of stone powder.