فصلنامه پژوهشهای علوم و فناوری چوب و جنگل
سال بیست و نهم شماره 1 (بهار 1401)

Nowadays, production of lightweight fiberboard with density lower than 500 kg/m3 gained a lot of interests for both non-structural and insulation applications in buildings. Environmental friendliness, lower price, recyclability, superior thermal and sound insulation, and desirable mechanical properties are some of the advantages of lightweight fiberboard compared to those of polymeric (polystyrene and polyurethane foams) and mineral-based (glass and mineral wool) insulation boards. Replacement of isocyanate and improving the board flexibility are in major focus for such panel’s producers. Hence, the aim of this study was to evaluate the production capability of lightweight fiberboard by replacing the isocyanate with polystyrene resin obtained from foam dissolution in methylene chloride solution. To this end, the effect of press temperature, solvent to foam weight ratio, different percentages of isocyanate replacement with polystyrene adhesive and board density on the physical and mechanical properties of lightweight fiberboard were investigated.

Lightweight fiberboard (10 mm thick) with density from 200 – 300 kg/m3 were produced using wood fiber with combination of isocyanate and polystyrene as adhesive. In this study, mechanical (bending strength, modulus of elasticity, compression strength and tensile strength perpendicular to panel surface (internal bond)) and physical properties (thickness swelling and water absorption) of the panels were evaluated.

The best modulus of elasticity, tensile and compressive strength was observed in boards made at 160°C. Increasing the weight ratio of solvent (methylene chloride) to polystyrene foam had a negative effect on these properties. Also, changing the solvent to foam ratio did not have a significant effect on the physical properties (thickness swelling and water absorption) of lightweight fiberboard. Increasing the percentages of isocyanate replaced with polystyrene adhesive (from 15 to 45% (based on the amount of isocyanate used)) improved the bending and physical properties and weakened the compressive and tensile strengths perpendicular to the panel’s surface. Mechanical properties (bending strength, modulus of elasticity, compressive and tensile strength) of the lightweight fiberboard as well as the swelling thickness of samples have increased significantly with increasing the board’s density.

In this study, lightweight fiberboard was developed using isocyanate as an expensive and toxic adhesive replaced with adhesive made from recycled polystyrene foams. The results showed good performance of boards made with 45% isocyanate replaced with polystyrene adhesive. Generally speaking, a promising alternative for recycling of polystyrene foams (used as adhesives for wood-based panels industries) was presented in this research while lightweight fiberboard was also produced as non-structural and insulating applications having less isocyanate consumption.

Wood as a renewable material, with its various benefits, has always had different applications in human society. Wood as a natural and biodegradable material has always been considered by humans throughout the history. However, the fact that wood is a natural material originating from different trees, create limitations on its properties such as moisture absorption, dimensional changes, biodegradation, degradation by ultraviolet radiation and weathering, etc. Therefore, this natural product may need to be modified in order to achieve the desired functionality and application. There are different modification methods which can be improved the physical and mechanical properties of wood. Enhancement of light wood density by compression process is one of wood modification methods that often improve the mechanical properties. But springback is the main subject in this process. There have been done numerous studies in this field but no suitable method has been presented until now that can effectively control springback. Therefore, the aim of this study was improvement of physical and mechanical properties of poplar wood (Populus deltoides) by using hydro-thermal pretreatments; at the same time, springback assessment under this process.

In current study, Poplar wood (Populous deltoids) was initially cut into timber in wood and paper laboratory of Alborz research complex and then change into the pieces with dimensions of 45×7×4.2 cm3 (longitudinal× tangential× radial). Afterwards, the wood specimens were hydrothermally treated at temperatures of 100°C for three times of 0, 60 and 120 minutes. In the next step, the second pretreatment and also densification process was carried out under a hot press in the radial direction with a compression set of 40 percent. The pretreated poplar wood specimens were immediately compressed by hot press at temperature of 160, 180 and 200°C for two times of 60 and 90 minutes. The press pressure was considered 50 kg/cm2. The specimens were then physically and mechanically tested as density gradient, springback after press and also conditioning, impact strength and compression parallel to grain. The results were analyzed based on complete randomized design (CRD) under a factorial experiment by SPSS software. The mean comparison was evaluated using Duncan's multiple range test.

Results assessment in compared with other studies showed that acceptable physical and mechanical properties can be reached by this process such as uniform structure and less density gradient. Moreover, the results revealed reduction of springback after press and conditioning and also improvement of mechanical properties such as impact strength and compression parallel to grain.

The densification process of low-density wood species with hydro thermal pretreatments improve the physical and mechanical properties and expands their functional domain.

Allelopathy is the interaction between plants that stimulates or inhibits the growth and germination of other species. Non-native species of (Prosopis juliflora (SW.) DC) is one of the species known as invasive species with allelopathic effects that can inhibit the growth and growth of species by producing allopathic compounds such as phenols, alkaloids into the environment. Two important species of Hormoozgan province are Acacia oerfota and Acacia tortilis which P.juliflora was observed with them in the natural forests, Therefore, the correct selection of tree species in forest plantation should be done with caution in order to inhibit negative effects on native species. The aim of this study was to investigate the allelopathic effects of different organs of p. juliflora on germinatin, radicle and plumule length of Ac. tortilis and A. oerfota.

For this purpose, the organs (root, bark and leaf) of P.juliflora were collected and different extract concentration (0, 2, 4, 6 and 8%) were prepared were added on A.tortilis and A. oerfota (4 replications, n=60) in growth chamber, and after recording germination, the plumule and radicle length were meausered after 30 days. Factorial experiment was performed through completely randomized design and was analyzed by two-way variance analyses.

Results showed that the lowest gemination percentage in A.tortilis was observed at 8% concentration with the amount of 16.11%. The plumule length of A. tortilis and A. oerfota in aquatic extraction of leaves (1.73 and 3.9 cm) was significantly lower than other organs. Also, the plumule length of A. tortilis (3.58 cm) and A. oerfota (5 cm) had the highest amounts in control. The interaction effects of organ × concentration showed that plumule and radicle length in A.tortilis and A. oerfota had the significant differences. The interactions of organ × concentration on radicle and plumule length in A.tortilis and A. oerfota species were also significantly different. The radicle and plumule length of A. tortilis and A. oerfota in leaf organ with values of 1.25, 1.73 cm and 1.98 and 3.9 cm were significantly less than bark and roots, respectively.

The results showed that there were inhibitory effects of aqueous extract of Prosopis juliflora root, bark and leaves on the germination percentage, root length and stem length of two important species of Acacia tortilis and Acacia oerfota in laboratory condition. Among the three studied organs, the leaf organ had the most inhibitory effects, which due to the high volume of litter under the canopy of this species in the environment and the entry of toxic compounds into the surface soil due to decomposition, prevents the growth of Acacia tortilis and Acacia oerfota that P. juliflora is seen with these species and overcome on them. Also, the root had the lowest inhibitory In according to the results, P.juliflora has allelopathic effects on native species. Therefore, it is recommended to choose non-native species for afforestation more carefully and using native species for reforestation and afforestation in the south fragile ecosystem of Iran is more suitable option.

Due to rapid population growth and increasing demand for forest resources, large areas of forest have been subjected to different degrees of degradation, and this degradation is increasing at an alarming rate. Large areas of forest have been varied by various degrees of degradation, and this degradation is increasing with an alarming rate due to rapid population growth and increasing demand for forest resources. Only 15 percent of the world's forests are undegraded, 20 percent have been destroyed and 28 percent have been deforested. Forest degradation is a global phenomenon that destroy10.6 million hectares of the world's forests each year. Therefore, studies focus on the effects of forest degradation impacts on the structure and composition of forests around the world. The goal of this study was to compare the structure of oak-hornbeam stands in different degradation intensities in Arasbaran forest.

The distance method was used to calculate the structural diversity index in Arasbaran forests, using three indicators, including uniform angle, tree diameter differentiation, and mingling indices. Within the study area with the different intensity of human interventions, three one-hectare sampling areas were selected. In order to select the study points in the regular systematic way 25 *25 m grid was laid out and the nearest tree to the intersection point of gird as reference tree was selected and measured with the four nearest neighbor trees. the diameter at the breast height (DBH), distance, and angle between trees in structural groups were measured.

The results of calculating the uniform angle index showed a change in the distribution pattern of stands due to the increase in the intensity of destruction from random to clump and uniform distribution. The diameter diffrentation index of trees showed that the value of this index was the lowest (0.12) in the moderate and was the highest (0.38) in the severe degradation intensity. The results of the study of the mingling species index showed that the highest value of this index was in the low degradation intensity (0.61) and the lowest value was in the moderate degradation intensity (0.08). Statistical analysis showed a significant difference (p≤ 0.05) between these indices in all stands. Calculation of the structural diversity index also showed that the highest structural diversity was in the stands with low degradation intensity (0.5) and the stands under medium degradation intensity had the lowest amount of structural diversity index (0.14).

Planning to reduce the human interference should be prioritized considering the effects of human degradation on the structure of the Arasbaran forest.

Forests as a renewable resource play an important role in the economic and social activities of the society. In the principled exploitation of the forests of northern Iran, the existence of a suitable road network along with skid trails the most fundamental role. Skid trails in the forest are one of the most difficult and costly operations. The purpose of this study is to design the proposed Skid Trails Planning in the forest using AHP and GIS for various operations.

For this purpose, the parcels 18 and 19 of district 4, part 2 of Neka Zalemarud with an area measuring 97 hectares have been selected. According to effective factors in skid trail planning such as slope, soil, geology, stand per hectare, streams, aspect, forest type, elite trees, and altitude, we have attempted to design a questionnaire and filled by some experts. These factors were weighted in Export Choice (EC) software via the pair-wise method. Finally, the status of the designed skid road and the existing skid road were compared. Then, on the map, the ability to pass lands in Arc view environment was designed using PEEGER software, three options. Finally, the specifications of the proposed routes were compared with the existing route. The Chi-square test was used for statistical comparison between the most appropriate option and the available path.

Analysis of different layers based on the opinion of experts, showed that the longitudinal slope with a relative weight of 0.366 has the highest score, followed by the waterway 0.115 and finally the height above sea level with a relative weight of 0.026 has the lowest score. . The results of evaluating the existing routes and proposed variants on the land passability map showed that the percentage of passing the existing route length over the area with suitable power is less than the proposed variants (22.87) and the percentage of crossing the existing route on the area with Inadequate power is higher than the designed variants (24/99).

The results of the Chi-square test showed that the proposed routes were significantly (at 95% level) better than the existing route in terms of crossing suitable areas (p = 0.0001). Therefore, according to the results, if the percentage of the desired longitudinal slope is reduced; it is suggested to consider a longer route because, in such a long route, the topography cannot be shown precision.

In arid and semi-arid ecosystems, the relationship between tree species and habitat is fragile due to environmental stresses. Native species of Prosopis cineraria and non-native Prosopis juliflora are among the species that in addition to water-soil-plant relationships, affect the life of other animal and plant species in these areas. In these areas, the role of native trees in carbon storage and change in soil properties is important. Soil plays an important role in the carbon cycle and is an important source of carbon storage and tree species can make changes in soil properties and organic carbon storage due to tolerating hard environmental conditions such as high temperatures and radiation. Soil biological properties are a good indicator for measuring soil quality and by examining them, appropriate information about respiration, nutrient cycle, microbial biomass and mineral nitrogen mineralization capacity is obtained. (Prosopis cineraria (L.) Druce) is one of the most important native species in the Sahara-Sindhi area, which has a good ability to establishment and adapt and improves soil properties. The non-native species of (Prosopis juliflora (SW) DC) is widely planted with fast growth and prevention of fine dust as a fodder tree. Trees in these areas can have a range of different effects on the soil under their canopy in various ways and have a vital effect on the richness of soil microorganisms. Due to the importance of both species in this habitat, a comparison of changes in soil biological properties and organic carbon storage under and outside the canopy of Prosopis cineraria and Prosopis juliflora bases was performed in Assaluyeh in Bushehr province.

To measure basic and induce respiration, microbial biomass carbon and nitrification potential, 24 soil samples were collected from 0-30 cm depth randomly from under and outside the canopy of both species. To calculate organic carbon storage of soil with the cylinder in a 1×1 m2 plot, sampling was done from a depth of 0-10 cm of soil to obtain the bulk density and organic carbon. Also for measuring organic carbon storage in litter and grass cover in the same sample plot, litter and grass cover were collected and their weight was recorded. Finally, 120 samples were taken in two location under and outside the canopy of both species.

The results of analysis of fragmented plots showed that the effect of species as the main factor on basic (p<0.05) and induce (p<0.01) respiration was significant and it was in Prosopis cineraria 2.73 and 22.47 mg Co2 in day and hour and in Prosopis juliflora 0.9 and 15.57 mg Co2 in day and hour, respectively was higher in Prosopis cineraria than Prosopis juliflora and had no significant effect on microbial biomass carbon and nitrification potential. The effect of sampling location was significant for all variables studied and under the canopy was greater than outside the canopy.

Due to the positive effect of Prosopis cineraria species on basic and induce soil respiration, preservation and revitalization of this valuable native species is very vital and negative effect of non-native species of Prosopis juliflora on basic and induce soil respiration can reduce microbial activity and upset the balance of the nutrient cycle, especially carbon. Therefore, it is recommended to use native species for improvement and quality of soil in natural forests, afforestation and restoration of ecosystems and the entry of non-native species avoid into the natural forest. Also Prosopis juliflora species is better to be cultivated because high resistance in de- desertification areas and for quicksand stabilization.

Paulownia fortunei is from industrial and multipurpose introduced tree species that has been considered for wood farming, agroforestry practices and seedling production in northern Iran, especially in Golestan province, due to its suitable growth properties and productive traits. Knowing the factors affecting the germination and early growth of this species can provide the possibility of improving the quality of seedlings produced in forest nurseries and thus increases the feasibility of success in planting practices of this species. Therefore, in terms of the importance of studying the reaction of P fortune against different light intensity control treatments, the present study tries to investigate the effect of artificial shading on the performance of this plant in the germination and seedling stages.

Thanks to the inherent differences in plant needs and responses in the stages of germination and early growth, in this study, two independent experiments were designed and performed to achieve the research objectives. Aimed to investigate the effects of artificial shading treatments on performance of this plant, two independent experiments were conducted at germination and seedling stages. In the first experiment, using a completely randomized design, seed germination features were studied under three shading (25%, 50% and 75%) and one control (without shade) treatments in the laboratory (Temperature of 25 °C and 70% relative humidity in a Germinator) conditions. In this experiment, seed germination was recorded for 3 weeks and at the end of the period, the growth traits of the sprouted seedlings were examined. Based on the information obtained, seed germination traits including germination speed (GS), germination energy (GE), peak value (PV), mean daily germination (MDG) and germination value (GV) as well as seed vigor index (VI) and length of shoot and root of sprouted seedlings were measured. In the second experiment, the growth and survival of 44 potted p fortunei seedlings under four treatments (including control, 25%, 50% and 75% shading) were studied in the first growing season for 5 months, from the beginning of July to the end of November. At the end of the growing season, all seedlings were taken out of the pot and length, diameter and dry weight of stem, leaf area and length, dry weight of main and secondary roots were measured after separating the shoot and root. One-way analysis of variance and Duncan's test were used for statistical comparing of treatments at 5% probability level.

The results showed that GP, GS, MDG, and VI did not affected by shading treatments, However, the negative effects of shading treatments, especially in 50% and 75% shading levels on GV and PV were significant. Artificial shading did not affect first year seedling survival, so that all of seedlings were survived under all treatments. Also, the results showed that under 50% and 75% shading treatments, stem length, stem diameter, stem dry weight, number and area of leaves were significantly higher than control and 25% treatments. Additionally, under 50% shading treatment, secondary root dry weight and total dry weight of seedlings were significantly upper than other treatments.

Seed germination and first year survival of P. fortunei did not so sensitive to light intensity, but controlling light intensity using artificial shading improve seedling quality traits of this species. Hence, use of 50% shading treatments can be proposed in nurseries of this species after initial stages of germination and seedling establishment.

 Biodiversity is one of the most important indicators of the sustainability of forest ecosystems, which is affected by stand mixture. Vegetation composition and diversity data are the most important basic information for recognizing the natural capacity and targeting for the principled management of forest habitats. On the other hand, the correct understanding of the regeneration status in the forest is the most important The components in predicting the future of the forest are in terms of structure and composition of tree elements. The aim of this study was to compare the diversity of herbaceous cover and regeneration in pure beech, pure hornbeam and mixed stands in Darbakola educational and research forest of Sari.

 For this purpose, the inventory was performed by randomized systematic method with grid dimensions of 75 × 100 meters and in each stand, 25 sample plots with an area of 400 square meters were implemented and the diameter and height characteristics of the trees were collected. To study biodiversity, names of herbaceous species and the type and number of regenerations were collected in 2×2 meter micro sample plots in four quarters and the center of the sample plots in two stages (May and September). Diversity indices of Shannon and Simpson richness indices of Margalf and Manhenick and evenness Owens and Burger Parker diversity indices were used to study the biodiversity of regenerations and grass cover. One-way analysis of variance was used to compare quantitative characteristics of biomass and biodiversity between habitats and to compare the means by SNK test in SAS software environment and to draw graphs using Excel-2010 software. Past software was used to study biodiversity.

 The results of the present study showed a higher density of beech regeneration in all three studied stands. The highest total number of regeneration was observed in mixed habitat (4040). The highest indices of diversity, richness and regeneration evenness were observed in pure hornbeam and the lowest in pure beech. Regarding herbaceous cover, no significant difference was observed between diversity indices among different stands, while the average of these indices was higher at the beginning of the growing season than at the end of the growing season. Therefore, stand mixture has more tangible effects on regeneration diversity than herbaceous cover, and herbaceous cover diversity is more affected by the during the growing season than type of stand mixture.

 Based on the results of the present study, the future composition of the studied populations will be affected by the dominant species of beech. Also, due to the species diversity in the mixed habitat, the highest total number of regeneration and forest density will be related to this stand. Regarding the grass cover, the higher average of diversity indices at the beginning of the growing season than at the end of the growth season, indicates that the environmental conditions are better in terms of temperature and soil moisture in this season. Therefore, mixing has more noticeable effects on regenerative diversity than grass cover and the difference in grass cover diversity is more affected by the time period of the growing season.