فصلنامه جنگل و فرآورده های چوب
سال هفتاد و چهارم شماره 3 (پاییز 1400)

SAR data have been widely used for estimation of forest variables. These data have a high potential in flat terrain, however, there are some problems such as the effect of topography on backscatters in mountainous regions. The goal of this study was to evaluate the effect of oriented and non-oriented aspect slopes and polarization in the estimation of stand Lorey’s mean tree height, volume, and basal area variables using dual-polarization (HH, HV) data of ALOS-2 PALSAR-2 in a part of Shastkalateh forest of Gorgan. Modeling was performed in three modes including without considering the aspect slope, in the slope-aspect orientated with the transmitted waves and non-orientated with waves, and also in the polarizations as separately using linear regression and support vector machine methods. The results of correlation between the backscattering of the PALSAR-2 and studied variables showed that in the slope-aspect orientated with the transmittance, the correlations were significant for basal area and volume, but it was not significant for Lorey's height. While in the non-orientated slopes, the correlation rate was very low for all variables and no significant. Also, the results showed that the HV polarization and the support vector machine method were very sensitive to the Lorey’s mean tree height, basal area, and volume variables with r and relative RMSE (-0.14, 12.44), (-0.48, 29.35) and (-0.44, 36.40), in the area in the direction of alignment with the waves, respectively. While the lower sensitivity is (-0.18, 14.14), (-0.05, 35.85), and (-0.04, 38.40), respectively, in the non-orientated with waves.

What the Local people of forest ecosystem design for different purposes and in order to meet their needs and wants is in the broadest sense of the traditional structures of local communities. The purpose of this study is to fully identify the production structures of local communities in the forests of Chaharmahal and Bakhtiari province. At the first, this identification will help to improve the role of local communities in the forests of the Zagros and secondly, by analyzing the production pattern in this production system, the best conditions for the continuation are introduced and the grounds for improving the conditions are determined for this continuation. In this study, snowball sampling method was used to collect information in the local community. In the section of identifying production structures, the most important knowledge and environmental components that constitute the input of this system were described. In the analysis of production pattern, while introducing appropriate criteria in evaluating the production process, the necessary requirements in order to improve the production pattern among the local communities of Zagros forests are introduced. The results of this study showed that among the three production patterns (craft, lean and agile), the traditional structures of local communities are the most suitable for the craft production pattern. While the agile production pattern is the best model of the production process in most production evaluation criteria. It is necessary to change from craft to agile model, considering environmental uncertainties and leveraging the effect of information on Zagros forest management.

The distribution of diameter classes is the most important structural characteristics of forest stands. Determining the fitting pattern of diameter classes in forests shows that, the overall status of these forests from the destruction process and ecological sequence points of view at different times. The aim of this study was to evaluate of frequency distributions of trees DBH in different development stages of natural stands in forests of Guilan. In order to study the statistical distributions of trees dbh,In order to determine the mixed stands characteristics in untouched forests for applying in silvicultural interventions, a reserve area in region in watershed number 9 (shafarod) from west of the Hyrcanian forests, northern Iran was selected. three sample plots of one hectare, were selected in three development stages. In three of development stages initial, optimal and decay were measured 419, 259 and 161 trees respectively. Beta, gamma, normal, lognormal, exponential, logistic and Johnson’s SB probability distribution patterns were fitted to diameter classes. Characteristics of distribution patterns were estimated using maximum likelihood method. Kolmogorov-Smirnov, Anderson-Darling and Chi-square tests were used for comparing of actual probability and probability which derived from functions. The results showed that the proper distribution function is different in three stages; So that in the initial stage, Johnson’s SB, in optimal stage, the Weibull, and in the decay stage, Weibol and Johnson’s SB have a good fit. Therefore, these distribution functions can be used for those who want to simulate changes of forests.

Effect of gap area on soil biological and enzymes activity in the beech forests (Case study: district 7, Shenrood, Siyahkal)AbstractCanopy gaps are one of the most important phenomena in forests and play an important role in the dynamics of forests. The present study aimed to evaluate the effect of canopy gaps area on soil biological and enzymes activities in beech forests of Siahkal. For this purpose, 18 gaps at 4 classes small (<200 m2), medium (200-300 m2), large (300-400 m2) and very large (>400 m2) were selected. Mixed samples of 0-20 cm soil depth were taken in each canopy gap. Frequency of bacterial and fungus population for measuring of soil biological activities were counted. Acid-phosphatase and dehydrogenase activity was assessed by reaction with substrate and photometrical method. ANOVA and Duncan tests were used to analyze of data. The results showed that the highest of acid-phosphatase and dehydrogenase activities observed in 300-400 m2 class, but there was a significant difference between of Acid-phosphatase activity in different canopy gaps of area. The results showed that the highest of bacterial and fungus population observed in <200 and >400 m2 classes and there was a significant difference between of bacterial and fungus population in different areas of gaps. In general, the results of study revealed that the gaps had a significant effect on soil enzyme and biological activities and indicates the important role of gaps within forest ecosystems.

In most parts of the Zagros, the structure of coppice oak stands is very fragile and unstable due to the lack of diversity in the horizontal and vertical profile. The aim of this study was to evaluate the effect of tending operations on the structural characteristics of Brant`s oak in Chegeni forests of Khorramabad, Lorestan province after 3 years. The study was conducted in a randomized complete block design with three replications with four treatments of light, medium and heavy thinning, which were thinned by 10, 20 and 30% of the basal area of the sprout-clumps, respectively, and the fourth treatment as a control. Measurements of quantitative variables were done. To investigate the effect of tending operations on dominance and dimension differentiation indices in the studied stands, the dominant and three neighboring sprouts in each sprout-clump were selected separately in different treatments and the quantitative characteristics of height and diameter of dominant and neighboring sprouts were measured. The results showed that due to tending operations, dominance and dimensional differences (collar height and diameter) indices of sprouts in heavy treatment were significantly higher than other treatments. Based on this, it can be concluded that heavy thinning treatment has been able to help improve the structure of the studied stands. Studying the effectiveness of other structural variables can help to identify the optimal thinning treatment. Also, this study emphasizes the importance of structural characteristics as a suitable tool for the management of oak coppice stands in order to help their sustainability.

In order to develop wood cultivation, it is necessary to use new high-yielding Poplar clones. For introduce the best clones, in this study, 12 new poplar clones that have entered the country in recent years and two previous successful clones (as a control) along with a native Caspian poplar were planted in a randomized complete block design with three replications at a distance of 4 by 4 m. Diameter and height traits were measured each year after the end of the growing season. Qualitative traits including the number of trunk curvature, the number of branches thicker than 5 cm, the number and percentage of two-branched trees in each clone, and the height of the branching position were recorded at the end of the fifth year. Simple analysis of variance for diameter and height values showed significant difference between the clones. However, combined analysis of variance for diameter and height growth values showed a significant difference in terms of diameter growth between clones as well as between different years. But for height growth values, there is a significant difference only between different years. P. deltoides marquette, and P. deltoids 69/55 as control clone with 13.65 and 13.28 cm in diameter and values of 10.63 and 10.50 m in height respectively, after 5 years of growth as best clones are introduced. In contrast, P. euramericana 87m. 119 and P. euramericana i-sieres were identified as the weakest clones. Qualitative traits did not impair the quantitative results.

Due to the special position of mycorrhizal fungi in improving the physiological status of host plants and increasing their resistance to environmental stresses, this study was conducted to explain the mycorrhizal symbiosis of oak trees in northern forest of Iran and their biological effects on Q. castaneifolia. In order to identify mycorrhizal fungi associated with oak trees, mycorrhizal root tips of hosts were collected and then the fungal ITS regions were amplified and sequenced. Phylogenetic analysis of sequences was performed by Bayesian method. A total of 217 root systems were collected from the studied habitats and 49 taxa from ectomycorrhizal fungi (13 genera) and 4 taxa of Arbuscular mycorrhizal fungi ( Acaulospora and Glomus) were identified among them. the symbiosis of Q. castaneifolia plantlets with Glomus mosseae and Hebeloma sinapizans were performed. Measurement of physiological characteristics, growth and water status of the inoculated plant in comparison with the control plant showed that the development of ectomycorrhizal symbiosis on oak plantlets significantly increased stem biomass, leaf biomass, leaf area and chlorophyll and also improved seedlings water content; However, there was no evidence of a significant positive effect of inoculation of arbuscular mycorrhizal fungi on Q. castaneifolia plantlets. Therefore, considering the improvement of water status, increase of growth and biomass and modification of physiological characteristics of the plant inoculated with ectomycorrhizal fungus, establishing this symbiosis can be introduced as a more appropriate approach to increase the success of planting in Q. castaneifolia forests restoration programs.

The difficulties in the measurement of rainfall interception in forests confirm the necessity of presenting models. The widely used models for estimating rainfall interception are physical-based models, among which the Sparse Gash is the most commonly used. We evaluated the Sparse Gash model for estimating the rainfall interception of five forest stands (two chestnut-leaved oak stands, two oriental beech stands, and one velvet maple stand) in the Hyrcanian region. In each stand, the gross rainfall and throughfall were measured using 5 and 20 rainfall collectors, respectively, and rainfall interception was calculated by subtracting the throughfall from gross rainfall. To evaluate the performance of the model, we used statistical metrics: Error percentage (Error), Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and the Model Efficiency coefficient (CE). Based on the Pearson correlation coefficient, the correlation between the values estimated by the model and the observed values was statistically significant at a 95% confidence interval. In all forests, the values of the CE were higher than 0.5, indicating the appropriate efficiency of the model. Based on the Error, the model showed good capability in estimating the rainfall interception of four forest stands (i.e., oriental beech in Lajim, chestnut-leaved oak in Kohmiyan and Sari, and velvet maple in Sari Error metric were found to be -10.3%, +12.7%, +10.8%, and +15.4%, respectively). Studying the performance of physically-based models in forests with different species and different allometric, climatic and rainfall characteristics completes the information gap about the efficiency of models to estimate rainfall interception.

Joints are one of the most important parts in engineering design of structure, since they are basis of structural failures. Therefore manufacturers are interested in to make sure that strength of proposed joints in structure is sufficient. Numerical analysis is an assuring method for joints strength assessment. In this study, finite element method modeling was applied to evaluate performance of screw connected joints with Laminated Veneer Lumber (LVL) members, under shear load, applied parallel and perpendicular to edge of side member. Test joints were made with screw, having diameter range of 4.2, 5 and 6 mm. ANSYS software was used to simulate joints for evaluating value of stress history resulting from applied load. Results have shown that the highest strength has occurred in pilot holes in main member and middle of screw’s shank. These values of stresses had higher rate when joint was loaded parallel to the edge of side member. Modes of failure were observed in test joints, bearing and bell shape, at points where the highest stresses were generated. Collected data have indicated that joints under perpendicular load to the had rather better performance. Stress carrying capacity of joint under parallel load to the edge of side member decreases with increase in diameter of screw, while in perpendicular loading, it increases with increasment of screw diameter. Since good agreement is seen between experimental data and numerical results, this method is recommended for analysing and predicting failure of joints in furniture structures.

In this research, the effect of adding polyethylene terephthalate (PET) on the physical and mechanical properties of oriented strand boards (OSB) made from Paulownia strands wood was investigated. Fixed factors of this research are: strands of Paulownia species (Paulownia fortunie) with the dimensions of 120×20×0/8 mm, soluble phenol formaldehyde resin (8% based on dry weight of strands and 10% based on dry weight of PET, density of 0.5 gr/cm3. The three layers OSB consisting of top layer (25% by weight) and bottom layer (25% by weight), and middle layer (50% by weight). Variable factors are: the mixing ratio of PET to paulownia strands at the four different levels of 0:100, 10:90, 20:80, 30:70 and the distribution of PET in three layers was in the surface layers, in the middle layer and in all three layers. The results showed that increasing in PET particle content decreased thickness swelling of the boards so that at the 30 percent level of PET particle, thickness swelling after 24 hours improved 50.63%. The mechanical properties decreased when PET content increased. The minimum of mechanical strengths observed at 30 percent of PET content. So that in comparison with the control samples showed a decrease of 50.45% in bending strength, 39.54% in modulus of elasticity and 73.68% in internal bond. According to the results can be concluded that the paulownia-PET OSBs meet the requirements of the EN-300 standard.