Gorgan University Of Agricultural Sciences and Natural Resources Journal of Wood and Forest Science and Technology 2322-2077 33 1 2026 03 21 Analysis and identification of strategic management of forest roads in northern watersheds using SWOT-AHP approaches Analysis and identification of strategic management of forest roads in northern watersheds using SWOT-AHP approaches 1 18 7751 10.22069/jwfst.2026.24416.2141 FA Yaser Asadiesbokolai M.Sc. Student of Forest Development and Exploitation, Faculty of Forest Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. 0000-0002-8755-4369 Aidin Parsakhoo Associate Prof., Dept. of Forestry, Faculty of Forest Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran 0000-0002-8755-4369 Mohammad Hadi Moayeri Professor, Dept. of Forestry, Faculty of Forest Sciences, Gorgan University of Agricultural Sciences and Natural Resources, Gorgan, Iran. 0000-0001-8888-0134 Journal Article 2025 12 21 Introduction and Objective: In recent years, the cessation of forestry projects and the resulting management vacuum have caused the deterioration of forest roads, and this issue has increasingly attracted the attention of experts to adopt an optimal approach to prevent the aggravation of damages caused by the implementation of the Forest Rest Law on the forest road network as a national capital and vital forest infrastructure. This study aimed to prioritize strategies by assessing strengths, weaknesses, opportunities, and threats in terms of forest road management. Materials and Methods: In the present study, first, a suitable set of strengths, weaknesses, opportunities, and threats of forest road network management from an economic, technical, and social perspective was identified using library research, past studies, and the opinions of specialists and experts. To create a strategy in forest road management, first, factors attributed to strengths, weaknesses, opportunities, and threats and a number of strategic criteria were developed for ranking using expert opinions and questionnaire completion. These questionnaires were completed by a total of twenty people, including academics and forest engineers with experience in forest road management. Since SWOT analysis is a qualitative analysis and decision-making method for quantifying the factors used and modeling, strategic criteria were processed using the Buckley and Chang approaches, both of which are widely used in the fuzzy analytic hierarchy process (AHP). Strategic criteria, along with the sub-factors prepared for SWOT analysis, were modeled by performing pairwise comparisons and quantifying them with AHP. Findings: Based on the results obtained, the weights of strengths, weaknesses, opportunities, and threats for the strategic management of forest roads in the north of the country were 3.43, 1.28, 3.78, and 1.13, respectively. The restoration of forest road functions in the vast areas of northern forests is the most important strength, the high costs of restoring the forest road network and the lack of financial resources are the most important weakness, the continuous presence and timely protection of the forest against disasters and violations are the most important opportunity, and the risks of incorrect planning, excessive cost, and waste of capital are the most important threats created by the strategic management of northern forest roads. The best strategy for the strategic management of northern forest roads, according to experts, is to maintain part of the network, develop off-road tourist and monitoring routes, and protect and operate the road independently (drones, helicopters, and telecommunication systems). In this study, the weight of external factors (2.46) was greater than the weight of internal factors (2.36). The final scores on the four strategic situation axis of SWOT analysis are less than 2.5, so a defensive strategy should be adopted. The goal of this strategy is to reduce weaknesses and avoid threats. In fact, such organizations try to reduce their activities to maintain their survival. Conclusion: Based on the findings of the present study, creating access to the field is the most important strength and desired outcome of the strategic management of the northern forest road network of the country, which provides the opportunity for continuous presence and timely protection of the forest. Adopting a defensive strategy and addressing weaknesses by providing financial resources to restore part of the forest road network and implementing other approaches and eliminating threats such as incorrect planning, excessive costs and waste of capital can achieve the strategic management goals of the northern forest roads. In conclusion, it can be acknowledged that SWOT-AHP is a useful tool for rational decision-making by considering all the factors that affect it. Introduction and Objective: In recent years, the cessation of forestry projects and the resulting management vacuum have caused the deterioration of forest roads, and this issue has increasingly attracted the attention of experts to adopt an optimal approach to prevent the aggravation of damages caused by the implementation of the Forest Rest Law on the forest road network as a national capital and vital forest infrastructure. This study aimed to prioritize strategies by assessing strengths, weaknesses, opportunities, and threats in terms of forest road management. Materials and Methods: In the present study, first, a suitable set of strengths, weaknesses, opportunities, and threats of forest road network management from an economic, technical, and social perspective was identified using library research, past studies, and the opinions of specialists and experts. To create a strategy in forest road management, first, factors attributed to strengths, weaknesses, opportunities, and threats and a number of strategic criteria were developed for ranking using expert opinions and questionnaire completion. These questionnaires were completed by a total of twenty people, including academics and forest engineers with experience in forest road management. Since SWOT analysis is a qualitative analysis and decision-making method for quantifying the factors used and modeling, strategic criteria were processed using the Buckley and Chang approaches, both of which are widely used in the fuzzy analytic hierarchy process (AHP). Strategic criteria, along with the sub-factors prepared for SWOT analysis, were modeled by performing pairwise comparisons and quantifying them with AHP. Findings: Based on the results obtained, the weights of strengths, weaknesses, opportunities, and threats for the strategic management of forest roads in the north of the country were 3.43, 1.28, 3.78, and 1.13, respectively. The restoration of forest road functions in the vast areas of northern forests is the most important strength, the high costs of restoring the forest road network and the lack of financial resources are the most important weakness, the continuous presence and timely protection of the forest against disasters and violations are the most important opportunity, and the risks of incorrect planning, excessive cost, and waste of capital are the most important threats created by the strategic management of northern forest roads. The best strategy for the strategic management of northern forest roads, according to experts, is to maintain part of the network, develop off-road tourist and monitoring routes, and protect and operate the road independently (drones, helicopters, and telecommunication systems). In this study, the weight of external factors (2.46) was greater than the weight of internal factors (2.36). The final scores on the four strategic situation axis of SWOT analysis are less than 2.5, so a defensive strategy should be adopted. The goal of this strategy is to reduce weaknesses and avoid threats. In fact, such organizations try to reduce their activities to maintain their survival. Conclusion: Based on the findings of the present study, creating access to the field is the most important strength and desired outcome of the strategic management of the northern forest road network of the country, which provides the opportunity for continuous presence and timely protection of the forest. Adopting a defensive strategy and addressing weaknesses by providing financial resources to restore part of the forest road network and implementing other approaches and eliminating threats such as incorrect planning, excessive costs and waste of capital can achieve the strategic management goals of the northern forest roads. In conclusion, it can be acknowledged that SWOT-AHP is a useful tool for rational decision-making by considering all the factors that affect it.

https://jwfst.gau.ac.ir/article_7751_a50020f6db1b6317fc5e77677ae261bb.pdf

Gorgan University Of Agricultural Sciences and Natural Resources Journal of Wood and Forest Science and Technology 2322-2077 33 1 2026 03 21 The influence of elevation gradient and machine traffic intensity on recovery of soil biochemical and microbial indicators in 7-year-old skid trails The influence of elevation gradient and machine traffic intensity on recovery of soil biochemical and microbial indicators in 7-year-old skid trails 19 49 7752 10.22069/jwfst.2026.24734.2165 FA Tohid Ghassemi Ph.D. Student of Forest Engineering and Utilization, Faculty of Natural Resources, University of Tehran, Karaj, Iran. Meghdad Jourgholami Professor, Dept. of Forestry and Forest Economics, Faculty of Natural resources, University of Tehran, Karaj, Iranepartment of Forestry and Forest Economics, Faculty of Natural Resources, University of Tehran, Karaj, Iran Journal Article 2026 05 24 Background and Objectives: Hyrcanian beech forests, as sensitive mountain ecosystems, are vulnerable to disturbances caused by logging operations. The traffic of skidding machinery leads to soil compaction and alterations in its biochemical and microbial properties, which can persist for decades. Elevation above sea level, by influencing climatic conditions, vegetation, and pedogenic processes, plays a crucial role in modulating these effects and determining the trajectory and rate of soil recovery. Despite the importance of this issue, there is limited information on the interactive effect of elevation gradient and traffic intensity on the recovery of microbial indicators and nutrient cycling in the soil of skid trails. This study aimed to investigate the effect of elevation gradient (700 to 1500 m a.s.l.) and machinery traffic intensity (low, moderate, high) on the recovery of soil biochemical and microbial properties in 7-year-old skid trails within pure Oriental beech (Fagus orientalis) stands of the Hyrcanian forests. Materials and Methods: Soil sampling was conducted seven years after logging operations on skid trails and adjacent undisturbed areas across five elevation gradients (700, 900, 1100, 1300, and 1500 m) in the Kheyrud and Kojur forests. In each trail, three levels of traffic intensity (low, moderate, high) were distinguished based on distance from the landing. Soil samples were taken from a depth of 0-10 cm. Microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) were determined using the fumigation-extraction method. Ammonium (NH₄⁺) and nitrate (NO₃⁻) concentrations were measured colorimetrically, and the net rate of nitrogen mineralization was determined through incubation. Data were analyzed using Kolmogorov-Smirnov, Levene's, two-way ANOVA, and Tukey's HSD tests. Results: The interaction effect of elevation gradient and traffic intensity was statistically significant for all studied indicators (p<0.01). In control (undisturbed) areas, MBC showed a substantial increase of 246% with increasing elevation from 700 to 1500 m. In contrast, MBN (68%), MBP (57%), NH₄⁺ (60%), NO₃⁻ (76.3%), and N mineralization rate (65%) decreased significantly. At lower elevations (700-900 m), MBC and MBN exhibited complete recovery; however, NH₄⁺ concentrations remained significantly lower than the control under moderate and high traffic intensities (6.5-7% reduction). At 900 m elevation, NO₃⁻ levels in all traffic intensity treatments (low, moderate, high) showed persistent reductions of 7.3%, 11.1%, and 7.7%, respectively, indicating sustained disruption of the nitrification process. At mid-elevations (1100 and 1300 m), high traffic intensity led to lasting decreases in NO₃⁻ (9-19%), N mineralization (11.5-14.5%), and MBP (21-26%). At the highest elevation (1500 m), high traffic intensity resulted in a 25% reduction in MBP and a significant increase in microbial biomass C/N and C/P ratios, signifying profound disruption of the phosphorus cycle and exacerbated P limitation. Pearson correlation analysis revealed that the interaction effect of traffic and elevation exhibited a very strong negative correlation with MBC (r = -0.88) and NO₃⁻ (r = -0.93), and a very strong positive correlation with the microbial biomass C/N ratio (r = 0.95). Conclusion: Seven years after logging operations, none of the elevation zones or traffic intensity levels had fully recovered to pre-disturbance conditions. Mid-elevations (900-1300 m) are particularly vulnerable to high traffic intensity, with persistent disruptions in nitrogen and phosphorus cycles posing a threat to long-term soil fertility. Management of skidding operations must adopt an approach based on elevational sensitivity, with strict limitations on traffic intensity, especially in mid and high elevations, to prevent irreversible degradation of these valuable ecosystems. Background and Objectives: Hyrcanian beech forests, as sensitive mountain ecosystems, are vulnerable to disturbances caused by logging operations. The traffic of skidding machinery leads to soil compaction and alterations in its biochemical and microbial properties, which can persist for decades. Elevation above sea level, by influencing climatic conditions, vegetation, and pedogenic processes, plays a crucial role in modulating these effects and determining the trajectory and rate of soil recovery. Despite the importance of this issue, there is limited information on the interactive effect of elevation gradient and traffic intensity on the recovery of microbial indicators and nutrient cycling in the soil of skid trails. This study aimed to investigate the effect of elevation gradient (700 to 1500 m a.s.l.) and machinery traffic intensity (low, moderate, high) on the recovery of soil biochemical and microbial properties in 7-year-old skid trails within pure Oriental beech (Fagus orientalis) stands of the Hyrcanian forests. Materials and Methods: Soil sampling was conducted seven years after logging operations on skid trails and adjacent undisturbed areas across five elevation gradients (700, 900, 1100, 1300, and 1500 m) in the Kheyrud and Kojur forests. In each trail, three levels of traffic intensity (low, moderate, high) were distinguished based on distance from the landing. Soil samples were taken from a depth of 0-10 cm. Microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) were determined using the fumigation-extraction method. Ammonium (NH₄⁺) and nitrate (NO₃⁻) concentrations were measured colorimetrically, and the net rate of nitrogen mineralization was determined through incubation. Data were analyzed using Kolmogorov-Smirnov, Levene's, two-way ANOVA, and Tukey's HSD tests. Results: The interaction effect of elevation gradient and traffic intensity was statistically significant for all studied indicators (p<0.01). In control (undisturbed) areas, MBC showed a substantial increase of 246% with increasing elevation from 700 to 1500 m. In contrast, MBN (68%), MBP (57%), NH₄⁺ (60%), NO₃⁻ (76.3%), and N mineralization rate (65%) decreased significantly. At lower elevations (700-900 m), MBC and MBN exhibited complete recovery; however, NH₄⁺ concentrations remained significantly lower than the control under moderate and high traffic intensities (6.5-7% reduction). At 900 m elevation, NO₃⁻ levels in all traffic intensity treatments (low, moderate, high) showed persistent reductions of 7.3%, 11.1%, and 7.7%, respectively, indicating sustained disruption of the nitrification process. At mid-elevations (1100 and 1300 m), high traffic intensity led to lasting decreases in NO₃⁻ (9-19%), N mineralization (11.5-14.5%), and MBP (21-26%). At the highest elevation (1500 m), high traffic intensity resulted in a 25% reduction in MBP and a significant increase in microbial biomass C/N and C/P ratios, signifying profound disruption of the phosphorus cycle and exacerbated P limitation. Pearson correlation analysis revealed that the interaction effect of traffic and elevation exhibited a very strong negative correlation with MBC (r = -0.88) and NO₃⁻ (r = -0.93), and a very strong positive correlation with the microbial biomass C/N ratio (r = 0.95). Conclusion: Seven years after logging operations, none of the elevation zones or traffic intensity levels had fully recovered to pre-disturbance conditions. Mid-elevations (900-1300 m) are particularly vulnerable to high traffic intensity, with persistent disruptions in nitrogen and phosphorus cycles posing a threat to long-term soil fertility. Management of skidding operations must adopt an approach based on elevational sensitivity, with strict limitations on traffic intensity, especially in mid and high elevations, to prevent irreversible degradation of these valuable ecosystems.

https://jwfst.gau.ac.ir/article_7752_4fff575c6a2dd0bb41b1794ce9b710fb.pdf

Gorgan University Of Agricultural Sciences and Natural Resources Journal of Wood and Forest Science and Technology 2322-2077 33 1 2026 03 21 Radial Growth Assessment of Brant’s oak (Quercus brantii Lindl.) and Identification of Pointer Years Radial Growth Assessment of Brant’s oak (Quercus brantii Lindl.) and Identification of Pointer Years 51 69 7753 10.22069/jwfst.2026.24567.2150 FA Firoozeh Hatami Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran 0000-0003-4496-3389 Yaghoub Iranmanesh Associate Prof., Forests and Rangelands Research Department, Isfahan Agricultural and Natural Resources Research and Education Center (AREEO), Isfahan, Iran Kambiz Pourtahmasi Prof., Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran, Karaj, Iran Mehdi Pourhashemi Prof., Forest Research Division, Research Institute of Forests and Rangelands, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran Erfan Motamedi Ph.D. Student, Department of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran, Karaj, Iran Journal Article 2026 02 16 Background and Objectives: Radial growth of trees, recorded in the form of annual rings, is a key indicator for assessing forest dynamics and their responses to environmental and management conditions. Brant’s oak (Quercus brantii Lindl.), the dominant species of the Zagros forests, has experienced considerable growth changes due to human pressures and climatic stresses. However, comprehensive information on the mean radial growth across different sites and regional scales is limited. This study was conducted to estimate the mean radial growth and evaluate the growth patterns of this species in different forest stands of Chaharmahal and Bakhtiari Province, to improve understanding the growth dynamics and identification of pointer years. Materials and Methods: Sampling was carried out on trees older than middle-aged (almost 50years) in four selected habitats (Tang-e Zendan, Abzalo, Forest Park, and Ghale Madreseh) representing natural forest conditions in the region. From each tree, two perpendicular cores were extracted with increment borer. After preparation with progressively finer sandpaper to clearly distinguish annual rings, ring widths were measured using a LINTAB table. The accuracy of cross-dated time series (growth curves) was verified using TSAP software and the COFECHA program. Mean growth of any trees, sites and finally this area calculated. Given the greater concentration of growth fluctuations during the past two centuries, positive and negative pointer years were identified for each site and the entire region using the Cropper method. Results: The results showed that growth patterns were similar across all sites, with growth periods of 167 to 313 years. Trees in Tange Zendan and Forest Park exhibited the lowest and highest mean radial growth, with averages growth rate of 0.75 and 1.5 mm, respectively. In terms of age structure, Ghale Madreseh and Abzalo had the oldest and youngest trees, respectively. Analysis of the overall growth curve indicated that the minimum and maximum annual ring widths were 0.31 mm and 2.2 mm, respectively. Considering the greater number of samples after 1880, analysis of growth trends over the past two centuries revealed that maximum and minimum mean growth occurred in 1992 and 2018, reaching 1.85 mm and 0.48 mm, respectively. Pointer year analysis using the Cropper method showed a predominance of negative pointer years across all sites. Regionally synchronous years observed in more than three sites included nine positive years (1924, 1943, 1946, 1957, 1992, 2013, 2016, 2019, 2020) and seven negative years (1901, 1937, 1960, 1964, 1984, 2009, 2018). Conclusion: This study aimed to estimate the mean radial growth of Q. brantii, a key species of the Zagros forests, which was found to be approximately 1 mm for 170-year-old trees. Growth curves indicated that site dynamics generally follow a regional growth pattern, however, local differences in age structure and environmental conditions influenced ring width variability. Younger sites exhibited faster growth, whereas older stands reflected greater long-term ecosystem stability. The 313-year growth chronology of Brant’ oak in Chaharmahal and Bakhtiari showed a typical pattern of rapid growth in youth, a peak during maturity, and a gradual decline in older ages. Pointer year analysis over the past two centuries demonstrated synchronous regional growth fluctuations, and the predominance of negative years suggests high sensitivity of this species to drought and extreme warming events, potentially threatening the long-term sustainability of Zagros forests. Background and Objectives: Radial growth of trees, recorded in the form of annual rings, is a key indicator for assessing forest dynamics and their responses to environmental and management conditions. Brant’s oak (Quercus brantii Lindl.), the dominant species of the Zagros forests, has experienced considerable growth changes due to human pressures and climatic stresses. However, comprehensive information on the mean radial growth across different sites and regional scales is limited. This study was conducted to estimate the mean radial growth and evaluate the growth patterns of this species in different forest stands of Chaharmahal and Bakhtiari Province, to improve understanding the growth dynamics and identification of pointer years. Materials and Methods: Sampling was carried out on trees older than middle-aged (almost 50years) in four selected habitats (Tang-e Zendan, Abzalo, Forest Park, and Ghale Madreseh) representing natural forest conditions in the region. From each tree, two perpendicular cores were extracted with increment borer. After preparation with progressively finer sandpaper to clearly distinguish annual rings, ring widths were measured using a LINTAB table. The accuracy of cross-dated time series (growth curves) was verified using TSAP software and the COFECHA program. Mean growth of any trees, sites and finally this area calculated. Given the greater concentration of growth fluctuations during the past two centuries, positive and negative pointer years were identified for each site and the entire region using the Cropper method. Results: The results showed that growth patterns were similar across all sites, with growth periods of 167 to 313 years. Trees in Tange Zendan and Forest Park exhibited the lowest and highest mean radial growth, with averages growth rate of 0.75 and 1.5 mm, respectively. In terms of age structure, Ghale Madreseh and Abzalo had the oldest and youngest trees, respectively. Analysis of the overall growth curve indicated that the minimum and maximum annual ring widths were 0.31 mm and 2.2 mm, respectively. Considering the greater number of samples after 1880, analysis of growth trends over the past two centuries revealed that maximum and minimum mean growth occurred in 1992 and 2018, reaching 1.85 mm and 0.48 mm, respectively. Pointer year analysis using the Cropper method showed a predominance of negative pointer years across all sites. Regionally synchronous years observed in more than three sites included nine positive years (1924, 1943, 1946, 1957, 1992, 2013, 2016, 2019, 2020) and seven negative years (1901, 1937, 1960, 1964, 1984, 2009, 2018). Conclusion: This study aimed to estimate the mean radial growth of Q. brantii, a key species of the Zagros forests, which was found to be approximately 1 mm for 170-year-old trees. Growth curves indicated that site dynamics generally follow a regional growth pattern, however, local differences in age structure and environmental conditions influenced ring width variability. Younger sites exhibited faster growth, whereas older stands reflected greater long-term ecosystem stability. The 313-year growth chronology of Brant’ oak in Chaharmahal and Bakhtiari showed a typical pattern of rapid growth in youth, a peak during maturity, and a gradual decline in older ages. Pointer year analysis over the past two centuries demonstrated synchronous regional growth fluctuations, and the predominance of negative years suggests high sensitivity of this species to drought and extreme warming events, potentially threatening the long-term sustainability of Zagros forests.

https://jwfst.gau.ac.ir/article_7753_5c5c511b43ba1ce6407bdb4b9d7347f8.pdf

Gorgan University Of Agricultural Sciences and Natural Resources Journal of Wood and Forest Science and Technology 2322-2077 33 1 2026 03 21 Heavy Metal Accumulation and Distribution in Four Broadleaf and Coniferous Tree Species Cultivated at Mobarakeh Steel Company Heavy Metal Accumulation and Distribution in Four Broadleaf and Coniferous Tree Species Cultivated at Mobarakeh Steel Company 71 89 7754 10.22069/jwfst.2026.24540.2149 FA Kobra Badfar M.Sc. Graduate in Forestry, Department of Forest Science and Engineering, Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord, I. R. Iran Ali Soltani Department of forest sciences, Faculty of Natural Resources and Earth Science, Shahrekord University, Shahrekord, Iran. Siavosh Bakhtiyarvand Bakhtiari, PhD in Forest Science and Engineering, Department of Green Space, Mobarakeh Steel Company, Isfahan, I. R. Iran Hormoz Sohrabi Associate Professor, Department of Forestry, Faculty of Natural Resources and Marine Science, Tarbiat Modares University, Noor, I. R. Iran Journal Article 2026 02 10 Background and objectives Environmental contamination by heavy metals, particularly in industrial areas such as steel production facilities, poses a serious threat to ecosystem and human health. Phytoremediation is recognized as a sustainable and cost-effective approach for removing pollutants such as heavy metals from soil and water. Tree species, due to their extensive root systems, high biomass production, and perennial nature, are considered suitable candidates for long-term phytoremediation. This study investigated the capacity of four tree species Cupressus arizonica, Morus alba, Pinus eldarica, and Robinia pseudoacacia; grown in a heavy-metal-contaminated environment (the Mobarakeh Steel Complex) to accumulate and distribute heavy metals among roots, stems, branches, and leaves. The trees had grown for 17 years under similar conditions with drip irrigation in mixed stands within a single plot of approximately 0.5 ha. The main objectives were to evaluate organ-specific metal accumulation patterns, quantify the relative contribution of each organ to remediation, and determine the overall phytoremediation potential. The novelty of this study lies in providing an integrated analysis of metal concentration data together with actual biomass allocation patterns across the whole plant to achieve a more accurate assessment of species-specific remediation capacity. Materials and Methods Cadmium (Cd), copper (Cu), zinc (Zn), and iron (Fe) were selected due to their prominent occurrence in effluents and soils surrounding steel and metal smelting facilities. Five individuals of each species were randomly selected. Samples were separated into major plant organs, and after drying and grinding, metal concentrations were determined using flame atomic absorption spectrophotometry. Transfer factor (TF), biomass allocation, inter-metal correlations, and cumulative metal accumulation were calculated and analyzed using a general linear model. Results Cupressus arizonica (Zn: 223 mg·kg⁻¹; Cd: 6 mg·kg⁻¹) and Morus alba (Fe: 1336 mg·kg⁻¹; Cu: 55 mg·kg⁻¹) showed the highest metal concentrations, whereas Robinia pseudoacacia exhibited the lowest levels across organs. Leaves showed the highest TF values for all metals in all species. The highest Fe translocation was observed in Pinus eldarica leaves (TF = 27.86), followed by Morus alba (5.96) and Cupressus arizonica (3.69), while Cd and Zn generally showed TF values >1 in leaves. Copper translocation was species-dependent. Strong positive correlations among Cd, Cu, and Zn were detected in leaves of Morus (r = 0.85–0.96) and Robinia (r = 0.88–0.93), whereas no significant correlations were observed in Pinus. Pinus eldarica produced the highest total dry biomass (110 kg) with dominant allocation to stems (47%) and showed the greatest total metal accumulation, particularly for Cd, Cu, and Zn. Robinia pseudoacacia allocated the highest biomass share to roots (36%). Despite its low total biomass (30 kg), Morus alba exhibited high Fe and Cu accumulation in leaves. Metal concentrations in leaves of all species exceeded reported toxicity thresholds, indicating severe meta contamination stress. Conclusion The results demonstrate pronounced species-specific differences in heavy metal accumulation, translocation, and stabilization. Pinus eldarica is suitable for long-term metal stabilization due to high biomass production and metal storage in stems and roots, whereas Cupressus arizonica shows potential for combined stabilization and extraction through substantial foliar accumulation. Morus alba and Robinia pseudoacacia, despite lower biomass, are appropriate for restoration and management of moderately contaminated sites due to effective metal transfer to harvestable aerial organs. Accordingly, species selection in phytoremediation programs should be based on dominant metal type, contamination level, and management objectives (stabilization vs. extraction). Background and objectives Environmental contamination by heavy metals, particularly in industrial areas such as steel production facilities, poses a serious threat to ecosystem and human health. Phytoremediation is recognized as a sustainable and cost-effective approach for removing pollutants such as heavy metals from soil and water. Tree species, due to their extensive root systems, high biomass production, and perennial nature, are considered suitable candidates for long-term phytoremediation. This study investigated the capacity of four tree species Cupressus arizonica, Morus alba, Pinus eldarica, and Robinia pseudoacacia; grown in a heavy-metal-contaminated environment (the Mobarakeh Steel Complex) to accumulate and distribute heavy metals among roots, stems, branches, and leaves. The trees had grown for 17 years under similar conditions with drip irrigation in mixed stands within a single plot of approximately 0.5 ha. The main objectives were to evaluate organ-specific metal accumulation patterns, quantify the relative contribution of each organ to remediation, and determine the overall phytoremediation potential. The novelty of this study lies in providing an integrated analysis of metal concentration data together with actual biomass allocation patterns across the whole plant to achieve a more accurate assessment of species-specific remediation capacity. Materials and Methods Cadmium (Cd), copper (Cu), zinc (Zn), and iron (Fe) were selected due to their prominent occurrence in effluents and soils surrounding steel and metal smelting facilities. Five individuals of each species were randomly selected. Samples were separated into major plant organs, and after drying and grinding, metal concentrations were determined using flame atomic absorption spectrophotometry. Transfer factor (TF), biomass allocation, inter-metal correlations, and cumulative metal accumulation were calculated and analyzed using a general linear model. Results Cupressus arizonica (Zn: 223 mg·kg⁻¹; Cd: 6 mg·kg⁻¹) and Morus alba (Fe: 1336 mg·kg⁻¹; Cu: 55 mg·kg⁻¹) showed the highest metal concentrations, whereas Robinia pseudoacacia exhibited the lowest levels across organs. Leaves showed the highest TF values for all metals in all species. The highest Fe translocation was observed in Pinus eldarica leaves (TF = 27.86), followed by Morus alba (5.96) and Cupressus arizonica (3.69), while Cd and Zn generally showed TF values >1 in leaves. Copper translocation was species-dependent. Strong positive correlations among Cd, Cu, and Zn were detected in leaves of Morus (r = 0.85–0.96) and Robinia (r = 0.88–0.93), whereas no significant correlations were observed in Pinus. Pinus eldarica produced the highest total dry biomass (110 kg) with dominant allocation to stems (47%) and showed the greatest total metal accumulation, particularly for Cd, Cu, and Zn. Robinia pseudoacacia allocated the highest biomass share to roots (36%). Despite its low total biomass (30 kg), Morus alba exhibited high Fe and Cu accumulation in leaves. Metal concentrations in leaves of all species exceeded reported toxicity thresholds, indicating severe meta contamination stress. Conclusion The results demonstrate pronounced species-specific differences in heavy metal accumulation, translocation, and stabilization. Pinus eldarica is suitable for long-term metal stabilization due to high biomass production and metal storage in stems and roots, whereas Cupressus arizonica shows potential for combined stabilization and extraction through substantial foliar accumulation. Morus alba and Robinia pseudoacacia, despite lower biomass, are appropriate for restoration and management of moderately contaminated sites due to effective metal transfer to harvestable aerial organs. Accordingly, species selection in phytoremediation programs should be based on dominant metal type, contamination level, and management objectives (stabilization vs. extraction).

https://jwfst.gau.ac.ir/article_7754_7d213e026d77f003ca861e1fe074ad24.pdf

Gorgan University Of Agricultural Sciences and Natural Resources Journal of Wood and Forest Science and Technology 2322-2077 33 1 2026 03 21 Assessment and Comparison of Machine Operators’ Working Posture in Forest logging Assessment and Comparison of Machine Operators’ Working Posture in Forest logging 91 109 7755 10.22069/jwfst.2026.24581.2152 FA Elaheh Mohammadi Ph.D. Student of Forest Science and Engineering, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Iran Mehrdad Nikooy Professor, Dept. of Forest Science and Engineering, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Iran Ramin Naghdi Professor, Dept. of Forest Science and Engineering, Faculty of Natural Resources, University of Guilan, Sowmeh Sara, Iran. Mahmood Heidari Associate Prof., Dept. of Occupational Health, School of Health, Guilan University of Medical Sciences, Rasht, I. R. Iran. Petros A. Tsioras Assistant Prof., Lab of Forest Utilization, Faculty of Forestry and Natural Environment, Aristotle University of Thessaloniki, POB 227, Thessaloniki, Greece. Journal Article 2026 02 19 Background and Objectives: Although the mechanization of timber harvesting reduces costs and increases productivity, it exposes machine operators to musculoskeletal disorders (MSDs) resulting from awkward working postures, prolonged sitting, and whole-body vibration. MSDs are among the most significant occupational health problems affecting forest machine operators and may lead to decreased productivity, work delays, and increased healthcare costs. Given the lack of comprehensive research in Iran on the assessment of working postures among logging machine operators, this study aimed to evaluate and compare the working postures of operators of two logging machines—the Timberjack 450C rubber-tired skidder and the ITM 285 agricultural tractor—in plantation forests of western Guilan Province, Iran. Materials and Methods: This cross-sectional observational study was conducted during the summer of 2024. Logging operations with the rubber-tired skidder were performed in Compartment 12 of Pilambra Forest, while tractor data were collected from Compartment 5 of Haft-Daghanan District. Operators’ working postures during different operational phases—including travel unloaded, maneuvering, winching, travel loaded, unloading, and sorting and piling (for the skidder), and travel unloaded, load collection, travel loaded, and unloading (for the tractor)—were recorded using video cameras. Postures were evaluated using the snapshot sampling method and the Ovako Working Posture Analysis System (OWAS). A total of 2,652 images were analyzed for the skidder and 5,539 images for the tractor. The Postural Risk Index (PRI) was calculated based on the frequency distribution of postures across action categories. Results: For both machines, the highest proportion of working postures was classified at Action Level 2, accounting for 67.08% for the skidder and 73.06% for the tractor. Action Level 1 comprised 32.67% for the skidder and 24.68% for the tractor. Action Level 3 represented 0.15% for the skidder and 2.26% for the tractor, while no postures were classified at Action Level 4 for either machine. The PRI was 167 for the skidder and 177 for the tractor, indicating a higher postural risk for the tractor operator. The skidder operator adopted 9 distinct working postures, whereas the tractor operator adopted 12. In skidder operations, posture codes 2111 (1,360 observations) and 3111 (762 observations) were the most frequent. For the tractor, posture code 2111 was the most frequent across operational phases (3,577 observations). Conclusion: Although both machines presented moderate postural risk levels, the specialized cabin design of the skidder, stable seated posture, and ergonomic control layout contributed to more favorable working postures and a lower PRI. In contrast, the agricultural tractor—due to its non-specialized design, absence of a standard cabin, and frequent transitions between seated and standing positions—was associated with greater postural variability and higher risk. Implementing preventive measures such as scheduled rest breaks, stretching exercises, ergonomic training, improved seat design, and reduced continuous working time is recommended to mitigate musculoskeletal disorders. Background and Objectives: Although the mechanization of timber harvesting reduces costs and increases productivity, it exposes machine operators to musculoskeletal disorders (MSDs) resulting from awkward working postures, prolonged sitting, and whole-body vibration. MSDs are among the most significant occupational health problems affecting forest machine operators and may lead to decreased productivity, work delays, and increased healthcare costs. Given the lack of comprehensive research in Iran on the assessment of working postures among logging machine operators, this study aimed to evaluate and compare the working postures of operators of two logging machines—the Timberjack 450C rubber-tired skidder and the ITM 285 agricultural tractor—in plantation forests of western Guilan Province, Iran. Materials and Methods: This cross-sectional observational study was conducted during the summer of 2024. Logging operations with the rubber-tired skidder were performed in Compartment 12 of Pilambra Forest, while tractor data were collected from Compartment 5 of Haft-Daghanan District. Operators’ working postures during different operational phases—including travel unloaded, maneuvering, winching, travel loaded, unloading, and sorting and piling (for the skidder), and travel unloaded, load collection, travel loaded, and unloading (for the tractor)—were recorded using video cameras. Postures were evaluated using the snapshot sampling method and the Ovako Working Posture Analysis System (OWAS). A total of 2,652 images were analyzed for the skidder and 5,539 images for the tractor. The Postural Risk Index (PRI) was calculated based on the frequency distribution of postures across action categories. Results: For both machines, the highest proportion of working postures was classified at Action Level 2, accounting for 67.08% for the skidder and 73.06% for the tractor. Action Level 1 comprised 32.67% for the skidder and 24.68% for the tractor. Action Level 3 represented 0.15% for the skidder and 2.26% for the tractor, while no postures were classified at Action Level 4 for either machine. The PRI was 167 for the skidder and 177 for the tractor, indicating a higher postural risk for the tractor operator. The skidder operator adopted 9 distinct working postures, whereas the tractor operator adopted 12. In skidder operations, posture codes 2111 (1,360 observations) and 3111 (762 observations) were the most frequent. For the tractor, posture code 2111 was the most frequent across operational phases (3,577 observations). Conclusion: Although both machines presented moderate postural risk levels, the specialized cabin design of the skidder, stable seated posture, and ergonomic control layout contributed to more favorable working postures and a lower PRI. In contrast, the agricultural tractor—due to its non-specialized design, absence of a standard cabin, and frequent transitions between seated and standing positions—was associated with greater postural variability and higher risk. Implementing preventive measures such as scheduled rest breaks, stretching exercises, ergonomic training, improved seat design, and reduced continuous working time is recommended to mitigate musculoskeletal disorders.

https://jwfst.gau.ac.ir/article_7755_3c726e5c78a1e60b59de3cd4176752f3.pdf

Gorgan University Of Agricultural Sciences and Natural Resources Journal of Wood and Forest Science and Technology 2322-2077 33 1 2026 03 21 Evaluation of physical and fiber properties of Amygdalus elaeagnifolia wood in different habitats of Chaharmahal va Bakhtiari Province Evaluation of physical and fiber properties of Amygdalus elaeagnifolia wood in different habitats of Chaharmahal va Bakhtiari Province 91 109 7756 10.22069/jwfst.2026.24536.2147 FA Mohsen Bahmani Associate Prof., Dept. of Furniture Industry Engineering, Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord, Iran. Fatemeh Ebrahimi M.Sc. Graduate, Faculty of Natural, Resources and Earth Sciences, Shahrekord University, Shahrekord, Iran. Saleh Kahyani Assistant Professor, Depsrtment. of Forestry, Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord, Iran Yaghoub Iranmanesh Associate Prof., Forests and Rangelands Research Dept. Isfahan Agricultural and Natural Resources Research and Education Leila Fathi Assistant Professor, Department of Furniture Industry Engineering, Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord, Iran Nasrin Gharahi Associate Professor, Department of Environmental Engineering, Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord, Iran. Elham Ghehsareh Associate Professor, Department of Natural Engineering, Faculty of Natural Resources and Earth Sciences, Shahrekord University , Shahrekord, Iran Journal Article 2026 02 09 Abstract Background and Objective: Zagros forests are a vital ecosystem in Iran, with wild almond species serving as key ecological components. This study investigates the effect of habitat conditions on wood physical properties and fiber biophysical characteristics of Amygdalus elaeagnifolia in two distinct habitats (Choliche and Karebas) within Chaharmahal va Bakhtiari Province. Materials and Methods: Wood samples were selectively harvested from healthy and same-aged trees at breast height, and properties such as dry density, critical basal density, swelling, shrinkage, and fiber characteristics (length, diameter, and cell wall thickness) were measured. In order to investigate the effect of habitat on the physical and biochemical characteristics of A. elaeagnifolia tree, the data were first evaluated for normality using the Kolmogorov-Smirnov test and for homogeneity of variances using the Levene test. If the assumption of normality and homogeneity of variances was confirmed, the means were compared with independent t-test. In cases where the assumptions required for the parametric test were violated, the non-parametric Mann-Whitney U test was used to compare the means. To analyze the relationships between variables, the Pearson correlation coefficient was used and the correlation matrix was presented as the basis for identifying the dominant axes of change. This matrix allowed for the examination of collinearity between traits and the determination of the set of co-ordinated variables. Also, to analyze the relationships between variables, principal component analysis (PCA) was used to reduce the dimensions of the data and identify the principal components. Findings: The results of statistical tests showed that some physical and biochemical properties of the wood of A. elaeagnifolia tree are affected by habitat conditions. The differences observed in indices such as density and structural components of fibers between the two habitats confirm the effective role of environmental factors such as climate in determining the properties of wood. The above correlations indicate a direct dependence of mass on volume at all moisture levels and indicate that the mass changes of the samples are mainly a function of their volume changes, which is fully consistent with the physical behavior of wood. The correlation between dry density and wet density and wet mass indicates the relative stability of the wood structure in the transition from dry to wet conditions. The critical basal density showed a strong positive correlation with fiber diameter. This indicates that thicker fibers are usually accompanied by thicker cell walls, which leads to an increase in basal density (dry mass to wet volume). Shrinkage and swelling showed a positive and very strong correlation. This indicates that these two mechanical properties have a coherent behavior; that is, wood that contracts more when drying also shows more swelling when absorbing moisture. In the biometric properties, a positive and strong correlation is also observed between the variables (crown diameter and crown cross-sectional area and between collar diameter and shoot height), which indicates the simultaneous and proportional growth of different tree components. Principal component analysis (PCA) showed that the first two components explain a major part of the total variance of the data. The first component was mainly influenced by the mass, volume and density of the wood, while the second component was more associated with traits related to swelling, shrinkage and climatic factors. These results indicate that the separation of specimens and habitats is not based solely on a single characteristic, but rather on the simultaneous combination of fiber and physical traits. Conclusion: Habitat conditions critically shape the physical and biophysical properties of A. elaeagnifolia wood. These insights support ecological assessments, conservation planning, and sustainable management of Zagros forest habitats. Abstract Background and Objective: Zagros forests are a vital ecosystem in Iran, with wild almond species serving as key ecological components. This study investigates the effect of habitat conditions on wood physical properties and fiber biophysical characteristics of Amygdalus elaeagnifolia in two distinct habitats (Choliche and Karebas) within Chaharmahal va Bakhtiari Province. Materials and Methods: Wood samples were selectively harvested from healthy and same-aged trees at breast height, and properties such as dry density, critical basal density, swelling, shrinkage, and fiber characteristics (length, diameter, and cell wall thickness) were measured. In order to investigate the effect of habitat on the physical and biochemical characteristics of A. elaeagnifolia tree, the data were first evaluated for normality using the Kolmogorov-Smirnov test and for homogeneity of variances using the Levene test. If the assumption of normality and homogeneity of variances was confirmed, the means were compared with independent t-test. In cases where the assumptions required for the parametric test were violated, the non-parametric Mann-Whitney U test was used to compare the means. To analyze the relationships between variables, the Pearson correlation coefficient was used and the correlation matrix was presented as the basis for identifying the dominant axes of change. This matrix allowed for the examination of collinearity between traits and the determination of the set of co-ordinated variables. Also, to analyze the relationships between variables, principal component analysis (PCA) was used to reduce the dimensions of the data and identify the principal components. Findings: The results of statistical tests showed that some physical and biochemical properties of the wood of A. elaeagnifolia tree are affected by habitat conditions. The differences observed in indices such as density and structural components of fibers between the two habitats confirm the effective role of environmental factors such as climate in determining the properties of wood. The above correlations indicate a direct dependence of mass on volume at all moisture levels and indicate that the mass changes of the samples are mainly a function of their volume changes, which is fully consistent with the physical behavior of wood. The correlation between dry density and wet density and wet mass indicates the relative stability of the wood structure in the transition from dry to wet conditions. The critical basal density showed a strong positive correlation with fiber diameter. This indicates that thicker fibers are usually accompanied by thicker cell walls, which leads to an increase in basal density (dry mass to wet volume). Shrinkage and swelling showed a positive and very strong correlation. This indicates that these two mechanical properties have a coherent behavior; that is, wood that contracts more when drying also shows more swelling when absorbing moisture. In the biometric properties, a positive and strong correlation is also observed between the variables (crown diameter and crown cross-sectional area and between collar diameter and shoot height), which indicates the simultaneous and proportional growth of different tree components. Principal component analysis (PCA) showed that the first two components explain a major part of the total variance of the data. The first component was mainly influenced by the mass, volume and density of the wood, while the second component was more associated with traits related to swelling, shrinkage and climatic factors. These results indicate that the separation of specimens and habitats is not based solely on a single characteristic, but rather on the simultaneous combination of fiber and physical traits. Conclusion: Habitat conditions critically shape the physical and biophysical properties of A. elaeagnifolia wood. These insights support ecological assessments, conservation planning, and sustainable management of Zagros forest habitats.

https://jwfst.gau.ac.ir/article_7756_8e81104517c351d084d1119bafbdcb4d.pdf

Gorgan University Of Agricultural Sciences and Natural Resources Journal of Wood and Forest Science and Technology 2322-2077 33 1 2026 03 21 Effect of Polymer Matrix Recycling on the Mechanical, Thermal, and Flammability Properties of Recycled Polypropylene/OCC Pulp/Graphene Nanocomposites Effect of Polymer Matrix Recycling on the Mechanical, Thermal, and Flammability Properties of Recycled Polypropylene/OCC Pulp/Graphene Nanocomposites 131 148 7757 10.22069/jwfst.2026.24639.2155 FA Jafar Ebrahimpour Kasmani Associate Prof., Dept. of Wood and Paper, Sava.C., Islamic Azad University, Savadkooh, Iran Ahmad Samariha Assistant Prof., Dept. of Engineering Sciences, Technical and Vocational University (TVU), Tehran, Iran Journal Article 2026 04 11 Background and Objectives The increasing consumption of polymers and the growing accumulation of plastic waste have intensified the need for the utilization of recycled polymers and the development of sustainable composite materials. In this context, the incorporation of cellulosic fibers into polymer matrices represents an effective approach to reducing the consumption of virgin polymers. However, the deterioration of mechanical properties caused by repeated recycling limits the broader application of such materials. Graphene nanoplatelets, as two-dimensional nanofillers with exceptional mechanical and thermal characteristics, offer considerable potential for compensating for these property losses. Therefore, the present study aimed to investigate the combined effects of polypropylene condition (virgin and three-times recycled) and graphene nanoplatelet content on the mechanical performance, thermal stability, and flammability behavior of polypropylene-based nanocomposites reinforced with recycled cellulosic fibers. Materials and Methods A 2 × 3 factorial experimental design was employed to manufacture rPP/OCC nanocomposites. Polypropylene was considered at two levels (virgin and three-times recycled), while graphene nanoplatelets were incorporated at three loading levels (0, 0.5, and 1 wt%) as the main experimental variables. The contents of OCC pulp (50 wt%) and maleic anhydride-grafted polypropylene (MAPP) compatibilizer (3 wt%) were kept constant in all formulations. Compounding was performed using a co-rotating twin-screw extruder, and test specimens were subsequently produced through injection molding. Mechanical characterization included tensile, flexural, and notched impact tests conducted according to relevant ASTM standards. Flammability behavior was evaluated using the Limiting Oxygen Index (LOI) test, while thermal stability was assessed through thermogravimetric analysis (TGA). Statistical analyses were performed using analysis of variance (ANOVA) and mean comparison tests at a 95% confidence level. Results The results demonstrated that graphene nanoplatelets significantly influenced most of the mechanical properties and the flammability behavior of the nanocomposites. Increasing graphene content to 1 wt% enhanced tensile strength and tensile modulus by 9.9% and 7.3%, respectively. Similarly, flexural strength and flexural modulus increased by 9.8% and 7.7%, respectively, while notched impact strength improved by approximately 2%. Furthermore, the incorporation of 1 wt% graphene increased the Limiting Oxygen Index by approximately 5.7%, indicating improved flame resistance. Thermogravimetric analysis revealed that graphene promoted higher degradation temperatures and greater char residue, thereby enhancing the thermal stability of the composites. Conversely, recycling polypropylene three times adversely affected the mechanical performance of the materials. Tensile strength and tensile modulus decreased by 4.9% and 21.9%, respectively, while flexural strength and flexural modulus declined by 5.23% and 22.92%, respectively. In addition, notched impact strength decreased by 11.7%. The effect of polypropylene recycling on the Limiting Oxygen Index was not statistically significant, with only a marginal increase of approximately 0.3% being observed. Moreover, the use of recycled polypropylene reduced char residue formation and resulted in lower thermal stability. TGA results confirmed that graphene increased both degradation temperature and residual mass, thereby improving thermal performance, whereas recycled polypropylene exhibited comparatively poorer thermal behavior. Conclusions The findings of this study indicate that graphene nanoplatelets act as an effective reinforcing nanofiller capable of significantly enhancing the mechanical properties, flame resistance, and thermal stability of polypropylene-based composites. The incorporation of graphene up to an optimum level of 1 wt% successfully improved the overall performance of the composites and partially compensated for the property deterioration associated with recycled polypropylene. These results suggest that combining recycled polypropylene, recycled OCC cellulosic fibers, and graphene nanoplatelets provides a promising strategy for developing high-performance, environmentally sustainable composite materials. Background and Objectives The increasing consumption of polymers and the growing accumulation of plastic waste have intensified the need for the utilization of recycled polymers and the development of sustainable composite materials. In this context, the incorporation of cellulosic fibers into polymer matrices represents an effective approach to reducing the consumption of virgin polymers. However, the deterioration of mechanical properties caused by repeated recycling limits the broader application of such materials. Graphene nanoplatelets, as two-dimensional nanofillers with exceptional mechanical and thermal characteristics, offer considerable potential for compensating for these property losses. Therefore, the present study aimed to investigate the combined effects of polypropylene condition (virgin and three-times recycled) and graphene nanoplatelet content on the mechanical performance, thermal stability, and flammability behavior of polypropylene-based nanocomposites reinforced with recycled cellulosic fibers. Materials and Methods A 2 × 3 factorial experimental design was employed to manufacture rPP/OCC nanocomposites. Polypropylene was considered at two levels (virgin and three-times recycled), while graphene nanoplatelets were incorporated at three loading levels (0, 0.5, and 1 wt%) as the main experimental variables. The contents of OCC pulp (50 wt%) and maleic anhydride-grafted polypropylene (MAPP) compatibilizer (3 wt%) were kept constant in all formulations. Compounding was performed using a co-rotating twin-screw extruder, and test specimens were subsequently produced through injection molding. Mechanical characterization included tensile, flexural, and notched impact tests conducted according to relevant ASTM standards. Flammability behavior was evaluated using the Limiting Oxygen Index (LOI) test, while thermal stability was assessed through thermogravimetric analysis (TGA). Statistical analyses were performed using analysis of variance (ANOVA) and mean comparison tests at a 95% confidence level. Results The results demonstrated that graphene nanoplatelets significantly influenced most of the mechanical properties and the flammability behavior of the nanocomposites. Increasing graphene content to 1 wt% enhanced tensile strength and tensile modulus by 9.9% and 7.3%, respectively. Similarly, flexural strength and flexural modulus increased by 9.8% and 7.7%, respectively, while notched impact strength improved by approximately 2%. Furthermore, the incorporation of 1 wt% graphene increased the Limiting Oxygen Index by approximately 5.7%, indicating improved flame resistance. Thermogravimetric analysis revealed that graphene promoted higher degradation temperatures and greater char residue, thereby enhancing the thermal stability of the composites. Conversely, recycling polypropylene three times adversely affected the mechanical performance of the materials. Tensile strength and tensile modulus decreased by 4.9% and 21.9%, respectively, while flexural strength and flexural modulus declined by 5.23% and 22.92%, respectively. In addition, notched impact strength decreased by 11.7%. The effect of polypropylene recycling on the Limiting Oxygen Index was not statistically significant, with only a marginal increase of approximately 0.3% being observed. Moreover, the use of recycled polypropylene reduced char residue formation and resulted in lower thermal stability. TGA results confirmed that graphene increased both degradation temperature and residual mass, thereby improving thermal performance, whereas recycled polypropylene exhibited comparatively poorer thermal behavior. Conclusions The findings of this study indicate that graphene nanoplatelets act as an effective reinforcing nanofiller capable of significantly enhancing the mechanical properties, flame resistance, and thermal stability of polypropylene-based composites. The incorporation of graphene up to an optimum level of 1 wt% successfully improved the overall performance of the composites and partially compensated for the property deterioration associated with recycled polypropylene. These results suggest that combining recycled polypropylene, recycled OCC cellulosic fibers, and graphene nanoplatelets provides a promising strategy for developing high-performance, environmentally sustainable composite materials.

https://jwfst.gau.ac.ir/article_7757_4cbbc235028f39ce5cb5599f97863ffd.pdf