فصلنامه پژوهشهای علوم و فناوری چوب و جنگل
سال بیست و نهم شماره 2 (تابستان 1401)

Tannin is a natural polymer that has recently been proposed for wood protection, but the structure of this polymer is not resistant to water and can be easily hydrolyzed or leached out from the wood. The use of various aldehydes to synthesize tannin-based resins and therefore improving the properties of these resins has already been studied. Furfural is a natural aldehyde and is the raw material for the production of furfuryl alcohol that is produced from the acidic hydrolysis of agricultural wastes, such as sugarcane. In this study, first, the effect of adding furfural on the tannin network features was investigated. Then, the ability of tannin/furfural natural resin was evaluated to impregnate and modify poplar wood to improve its physical properties and hygroscopic behavior.

Tannin-based resins were made with 20% m/m tannin and different ratios of furfural (2.5, 5, 10, 15, 20, 25, 40, and 50% of tannin dry weight) in different acidic conditions (pH 2, 4.5, 7, 9). For all formulations, the properties of resins were evaluated, including impregnation abilities, leaching resistance, viscosity, density and gel time. Optimal condition for making suitable resin to impregnate wood was selected by the complete factorial method using mini-tab software at a 95% confidence level. Then, the resin made under optimal condition was used to impregnate the poplar wood using the vacuum/pressure method. Heating was used to cure the resin and turn it into a polymer inside the wood. The physical properties of modified wood were measured according to ISO 13061 standard.

Examination of resin properties showed that with an increase in furfural ratio, the resin density increases. Moreover, the resin gel time and viscosity increased, with increasing furfural ratio and acidity respectively. The highest leaching resistance of resin was obtained with a resin made with 50% of furfural. Microscopic studies showed that resins containing furfural had a more porous structure. Thermogravimetric analysis showed that up to 580 °C, tannin / furfural modified polymer had higher thermal stability. According to the complete factorial method used, the optimal condition of resin manufacturing was adding 50% of furfural to tannin with an acidity of 4.5. Samples impregnated with the selected resins had less water absorption and swelling than the untreated ones. The volumetric swelling and water absorption of treated samples showed a considerable decrease with increasing resin concentration.

Extensive studies are underway worldwide to use natural polymers as wood preservatives or modifiers. The results of this study showed that the use of natural tannin / furfural resin has a promising prospect for improving the physical properties of wood. By accurately ‎adjusting the resin manufacturing conditions and the tannin-furfural pretreatment, a resin with suitable viscosity and leaching resistance can be achieved to be used in the wood impregnation industry. It is suggested that future studies investigate the conferred durability and mechanical properties of woods treated and modified with tannin / furfural polymer.

Since it is possible to use all kinds of lignocellulosic materials in particleboard production, so the utilization of agricultural residue can be one of the solutions to provide raw materials of this industry. At the same time, it has other advantages such as reduction of forest resources consumption, added value, reduction of environmental destruction, jobs creating, etc. Cultivation of kenaf plant has a considerable expansion in the world due to its advantages such as short growing season, low echological requirement as well as long fibers. Therefore, in recent years, it has been considerable by researchers, and there have been different studies on the use of kenaf bark and core in the production of wood composite products. This research was carried out with the aim of investigating the possibility of particleboard production from kenaf core in combination with bagasse and also evaluation of physical and mechanical properties of the produced particleboard.

In this study, kenaf (Hibiscus cannabinus) and bagasse were obtained from Ahvaz Sugarcane Research Institute and Neopan Karun Company, respectively. Debarked kenaf was first turned into chips and then into flakes that can be used for particleboard production. The other steps of particleboard production were included screening, drying, gluing, forming and pressing. Sample boards were made from lignocellulosic residue at two press time (4 and 5 minutes), two press temperature (170 and 180ᴼc) and four compositions (100:0, 75:25, 50:50 and 25:75 percent, kenaf core to bagasse). Other factors were as fixed factors such as resin consumption (10% based on dry material of the board) and press pressure (25 kg/cm2). Finally, a total of 48 laboratory boards were made based on different treatments and considering of three replications for each treatment. The specimens were then physically and mechanically tested as water absorption and thickness swelling after 2 and 24 hours soaking in water, bending strength, modulus of elasticity and internal bonding based on EN standard. 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.

The results showed that the bending strength improved with increasing of press temperature and press time. Moreover, increasing of kenaf consumption in the composition of raw material improved the bending strength, modulus of elasticity and internal bonding of the boards. On the other hand, the results revealed that the water absorption and thickness swelling after 2 and 24 hours soaking in the water decreased with increasing of pressing temperature, pressing time as well as amount of kenaf in the composition of the raw material.

In general, the particleboards from combination of kenaf and bagasse have acceptable physical and mechanical properties. Also, the small use of bagasse in the composition of the raw material can provide acceptable characteristics in the boards; but in higher amounts, it causes a drop in the physical and mechanical properties of the boards. Therefore, kenaf lignocellulosic residue in combination with bagasse can be used as suitable raw materials in the particleboard industry.

Accumulation of secondary metabolites in plants is part of the defensive responses to pathogenic attacks that inducers induce and activate. Plant tissue and cell culture is widely used as a sustainable method for the study of plant secondary metabolites. Betulinic acid is one of the most important anti-cancer and anti-AIDS metabolites, the main source of which is birch (Betula pendula Roth). Due to the extinction of these trees in Iran, it is necessary to replace modern methods of cell and tissue culture instead of skin extraction. The present study has been conducted in the same direction and with the aim of increasing the amount of effective substance produced.

Birch inner skin Explants were cultured in NT+ (2.5 mlg.l) 2-4,D +(0.5 mlg.l) BAP with 3% sucrose and 0.8% agar and callogenesis was done. Sub cultures were performed once a month and The 8-month-old cells were exposed to a magnetic field. Birch cells were treated in Suspension culture (About 1 g of soft and white callus in 30 ml of NT culture medium with the above-mentioned hormonal compounds without agar) by static magnetic field with an intensity of 30 mT and on days 8-11 after sub culture, 4 hours a day. Then cell viability, growth rate, betulinic acid and antioxidant properties in cells treated with magnetic field were measured and compared with untreated cells.

The results of this study showed that growth rate, betulinic acid and antioxidant properties in treated cells increased compared to control. But, cell viability was not affected by the magnetic field. However, the amount of magnetic input did not cause cell death or death. In treated cultures, total betulinic acid production (18/51 g/l) was 2.5 times higher than control cultures (7/28 g/l) and in treated cultures the ratio of antioxidant properties (40/09 %) was 2.8 times higher than control cultures (14/2 %) and in treated cultures the ratio of growth (0/12 %) was 1.2 times higher than control cultures (0.09).

Plant cells affected by magnetic field can have unpredictable responses due to various factors including species, magnetic field strength and duration of exposure. In this study, the magnetic field, like other inducers or elicitors, induced secondary metabolism in the cells by triggering the message chain through oxidative stress, and increased the production of secondary metabolites in birch cells compared to control samples. It can also be said the electromagnetic field as an artificial stress caused the cells to react and increase the growth and production of active substances. This elicitor can increase the medicinal properties of birch by increasing the amount of betulinic acid and antioxidant capacity.

Water and soil protection, providing living conditions for human communities and production of by-products are the most important performances and characteristics of Zagros forests. About one third of the total population of the country lives in the Zagros region and more than 70% of the total nomads of the country are in this area; in terms of livestock, 50% of the country's livestock are located in this area. Unfortunately, today the Zagros forests degradation is happening for various human and ecological reasons. Due to the importance of degradation in the Zagros forests and the unfavorable conditions of this ecosystem, the present study was conducted with the aim of geographical modeling of forest degradation factors in the Khorramabad basin.

Based on studies, five main causes of degradation were identified, including overgrazing, nomadic migration routes, distribution of residences, distribution of access roads and farming under the forest canopy. For each factor, a digital map was prepared and normalized by fuzzy method in ArcGIS. Fuzzy layers were weighted by AHP and degradation potential layer was obtained by WLC method. In order to validate this layer, five classes were considered and in each class 12 sample plots of 35 × 35 m were implemented and two factors of farming under the forest canopy and tree decline were examined and measured. Then, based on the numerical values of the forest degradation potential layer (as a response variable) and the field surveys of five degradation factors (as independent variables) at 30 random points, the modeling was performed by geographically weighted regression method.

The results of weighting the factors affecting forest degradation showed that the two factors of farming under the forest canopy and overgrazing are more important than other factors. Based on geographical modeling, the results of forest degradation prediction in the sample points showed that the residuals standard deviation without any specific spatial pattern are distributed throughout the forest. The continuous forest degradation prediction map also showed that there is potential for degradation in all parts of the forest, but with different intensities. There are three critical points on this map that should be given special attention in the management of these forests.

Various researchers have often used classical regression methods to model and investigate the factors affecting forest degradation, but this study has used geographical regression and many georeferencing errors of predictive data are automatically eliminated. Therefore, this method can be used with more confidence and used to prepare prediction maps.

Populus spp. have a wide distribution and also morphological variation in the world. One of the poplar species characteristics is being leaf heterophyllic; therefore sometimes it is difficult to distinguish different clones of a species from each other. Some certain poplar clones are commonly planted in the northern half of Iran. Knowledge of their indicator leaf morphological traits would be useful in distinguishing them from each other, finding these morphological traits was the main aim of this study. As well, the correlation between leaf morphological and the growth traits in mature trees could be led to introduce the leaf morphological traits which the evaluation of tree growth would be possible by them. Therefore, the investigation of correlations among leaf morphological and the growth traits of mature trees was considered as a sub-objective of the study.

In this study, we chose 14 clones, commonly planted in the northern half of Iran, includes four poplar species of P. nigra (42.78, 62.154, 63.135, betulifolia), P. alba (20.45, 44.13), P. deltoids (63.8, 69.55, 92.258, marquette), and P. euramericana (154, 214, costanzo, vernirubensis) from poplar clones collection of Alborz research station belongs to research institute of forests and rangelands (RIFR) located in Karaj where 9 individual with the aim of genetic preserve were planted. Studying the morphological traits, three of nine individuals from each clone randomly selected, and after leaves sampling from the height of 3-8 m of seven-year-old trees, 12 morphological traits of leaf were measured. As well as DBH, total tree height and also tree crown radius at any cardinal directions for calculating the crown horizontal projection, was measured in the late growing season in the case of the same three individuals belongs to any clone. Then, the correlations between the mature tree growth and leaf morphological traits were calculated. Finally by PCA (with two methods of correlation between main axes and the traits and also envi-fit) and nested design, the most effective traits for recognition of the clones were determined. Then for certifying the results, mean of the main traits between the groups resulted by clustering was compared by dunnet T3 test.

According to the clustering results, P. nigra, P. alba, and two of P. deltoids (63.8, 92.258) clones were placed in three groups separately. The four P. euramericana clones besides marquette and 69.55 from P. deltoids consisted another group. The five traits of leaf length, leaf area, maximum width of the leaf, leaf dry weight and petiole length were determined as the most effective morphological traits among investigated clones. Therefore the clones are recognized by using these traits. Crown area also was the only growth trait showing significant positive correlation with leaf morphological traits in a way that with its increasing, the traits of leaf length, maximum width of the leaf, petiole length, thicket of the leaves, leaf area, and dry mass were increased.

Respecting leaf heterophylly in the poplar genus and the high leaf similarity of the clones in investigated species, the key traits of leaves include length, area, maximum width, and dry weight besides petiole length were morphological indicators for distinguishing the 14 clones. Consequently, the poplar clones planted in private fields could be identified by measuring these traits to a large extent. It is inferred that crown area is more affected than DBH and total tree height on the leaves dimensions based on the present study. Hence, leaf morphological traits could not be reliable criteria for evaluating the diameter and height growth of the mature poplar trees, at least in the case of the clones investigated in this study.

Implementation of economic and non-economic functions of forests requires efficient planning and management, which requires reliable and dedicated information from forest resources, and the optimal information obtained from the details of forest stands parameters. The probability distribution models of various tree parameters provide helpful information about the complex interactions between trees and their environment and accurately describe tree growth processes. This study aims to develop suitable distribution models for the diameter, height, and canopy area of Caucasian oak trees in the Arasbaran forest and evaluate the effect of elevation on these models.

A selective sampling plot (with 100 × 100 meters dimensions) was designed in Caucasian oak stands located in Arasbaran Forest at 38 degrees and 57 minutes of north latitude to 47 degrees and 17 minutes of east longitude at three elevations including 1200-1300, 1300-1400, and 1500-1600 meter above sea level in three replications, which was the most present for the Caucasian oak tree. The diameter at breast height, the total height, and the two diameters of all trees’ canopy were measured inside each sampling plot. Quantitative statistics and comparison of means were analyzed using ANOVA and Tukey tests in SPSS 16 software and various statistical distributions were performed in Easyfit 5.5 software. The Kolmogorov-Smirnov fit goodness test was evaluated and reported at 95% and 99% confidence levels.

The results showed that the best function for the diameter distribution at the first, second, and third elevations were Beta, Normal, and Beta distributions, respectively. Fit goodness test for tree height showed that the trees had Weibull distribution at the first elevation and Beta distribution at the second and third elevations. The canopy area of the trees showed that the Weibull distributions at the first elevation and the Beta distribution at the second and third elevations were the most suitable models to show the probability distribution of this parameter. In addition, the diameter of trees in the three elevations does not have a significant difference. In comparison, the height of trees in more elevated areas was significantly higher, and the canopy of trees was strongly affected by the increase in elevation and showed a significant difference in all elevations (p≤ 0.05).

Based on the results of the present study, elevation is an influential factor in the height and canopy area of Caucasian oak trees. It is a factor in the diversity of probability distribution functions of diameter, height, and canopy area of Caucasian oak trees in the Arasbarn forest, which can be caused by the effect of various elevations on the environmental factors such as weather, soil, humidity and also the physiological characteristics of trees. This information provides reliable results for managers and decision-makers of Arasbaran forests.

In close to nature silviculture, dead trees have great importance because of their essential role in the conservation of biodiversity in forest ecosystems. In this regard, the amount (volume) of dead trees in pristine natural forests can be a guide for its maintenance in managed forests. One of the most important questions in recent years is how much dead trees can be recommended to retention in the managed natural forests. Related resources show different results for this variable. Therefore, in a meta-analysis, studies in Hyrcanian forests were collected and analyzed. This is the first meta-analysis for important structural factor in close to nature silviculture, dead tree volume, in the Hyrcanian forests.

This study includes design and search strategy, collecting articles and extracting data from them, include and exclude criteria and finally statistical analysis of extracted data. Dead tree related research was searched in national and international data base, including SID, Science Direct, Web of Science, Scopus, Google Scholar and IranDoc until May 2022. In this study, after review of several articles, data (mean, standard deviation and sample size) of 16 original studies related to the dead tree volume variable in Hyrcanian forests were collected that had 163 samples and the total area of the sample plots was 92.44 hectares. After extracting the data, Cochran's Q test and I2 index were used to evaluate the heterogeneity the studies and select the appropriate model for data analysis. To find the source of heterogeneity between studies, subgroup analysis was performed based on geographical areas (province) and tree composition. In this study, Beggs and Egger tests were used to investigate the publication bias. Data analysis was done with Comprehensive meta-analysis ver. 3.7.

The mean of dead tree volume was estimated to be 35.293 m3/h (Confidence interval 95%: 24.769 - 45.817) for Hyrcanian forests according to the significance of Cochrane Q test (p = 0.0001) and I2 index (99.735) based on the random effects model. Subgroup analysis showed that the highest dead tree volume was estimated based on a random model in the Golestan province forests as 50.520 m3/h (95% CI: 45.669 - 55.372). In this study, the publication bias test was not significant (p-value for Egger and Beggs tests was 0.28 and 0.24, respectively).

The average of dead tree volume in the Hyrcanian forests was estimated to be "average". Accordingly, the maintenance of at least 35 m3/h of dead tree in Hyrcanian-managed forests can be a guarantee for the preservation of the biological functions of these trees.

Tree marking and harvesting intensities in the single-tree selection method are a function of the stand characteristics, site description, and expert opinion in silvicultural practices. The different harvesting intensity has a significant effect on the remaining stands and the regeneration characteristics that introduce the forest’s future st. The impact of harvesting intensity on forest characteristics and forest stands specific to Hyrcanian forest structure has not been evaluated. This study investigated the silvicultural characteristics of mixed Hornbeam stands in control and compared them with different harvesting intensity stands.

A regular randomized sampling layout with a 300 × 400 m dimension was used in this research. The trees and shrubs characteristics of 70 sample plots of half a hectare were collected in harvested and control stand in 24 parcels. Forest stands were classified into three harvesting intensity groups low, medium, and high and without harvesting (control) based on the harvesting council report. The stand structure determines by using the triangle structure of the French Forestry Society. According to the total number of trees in 5 cm diameter classes and semi-logarithmic Y axis, 40 and 90 cm diameter classes were determined as the limit of small, medium, and large diameter classes.

The Hornbeam density as the main species in the harvested stands was higher than that of the control stand, but it had a smaller diameter at the breast height. The results showed that harvesting intensity had no effect on the characteristics of Lorey’s height, trees volume, and the volume of deadwood, while its effect on the diameter at the breast height and the trees crown characteristics, especially the height of the trunk and crown, the trees canopy surface area and volume was significant. The lowest harvesting intensity had the greatest additive effect on the tree crown (47%) and tree canopy volume (142%) and increasing in the harvest intensity recovered in the trade stem volume characteristic in the short time. The harvested stand structure did not significantly change with the control while the highest harvesting intensity made it younger and created a small and medium diameter class. The medium harvesting intensity was the most similar with control stand structure in terms of the placement of the samples in the seven structural classes. Most of the stands had an irregular structure, and large and intermediate-large diameter class, which is indicative of the uneven age and irregular structural condition of all mixed hornbeam stands.

The results showed that harvesting intensity less than 13.5% was improved the stands characteristics in mixed Hornbeam stands which indicating the importance of forest management and the impact of implementation of the single tree selection method in maintaining and improvement in forest stand structure. The stand structure in medium harvest intensity (between 3.5 and 9.5 percent) is closed to the control stand, so this harvesting intensity is introduced as the optimal intensity in accommodating the structure of the mixed Hornbeam stand of the eastern Hyrcanian forests located in the intermediate altitude from sea level.