فصلنامه پژوهشهای علوم و فناوری چوب و جنگل
سال بیست و هفتم شماره 4 (زمستان 1399)

the dimension stability of wood panels is one of the most challenges in these related industries. The humidity absorption not only changes the appearance and physical properties, but also it affects the mechanical structure and reduces the strengths. There are different methods for solving this problem such as chemical modification, monomer saturation, and thermal treatment. The disadvantages of each method are mechanical properties reduction and environmental problems. Chitosan is used in this study which it is the most abundant biopolymer after cellulose as a biodegradable and less reduction in mechanical strength. Chitosan is derived by chitin. Chitin is an amino-polysaccharide which it is polymerized by N-acetyl-D-glucosamine associated with B(1-4) linkages. Chitosan coated the particles and preserved them to humidity absorption. On the other hand, the thickness swelling and water absorption are decreased because the hydroxyl groups of wood are replaced by the acetamide groups of chitosan.

in this study, the wood mixture of forest species with variable factors (the amount of chitosan 2%, 4% ; thermal treatment temperature 120oc, 140oc, 160oc; and two types of adhesives urea formaldehyde and urea-melamine formaldehyde in ratio of 50/:50) is used which followed by the fixed factors (pressure, temperature and press time , 25 bar, 165oc, and 6 min, respectively). The amount of 42 particleboard samples with 10 mm thickness and 20*30 cm3 has been made. According to EN-317 standards, the samples with 10*50*50 mm3 dimensions are examined by 2 and 24 hours for water absorption and thickness swelling tests.

the particleboards are made by urea-melamine formaldehyde indicated less water absorption and thickness swelling rather than urea-formaldehyde. The water absorption and thickness swelling are decreased by using chitosan. By increasing the amount of chitosan utilization, the water absorption and thickness swelling are decreased. Increasing of thermal treatment temperature reduces the water absorption and thickness swelling.

With regards to different treatments in this study, the results showed that the optimal treatment conditions for decreasing of water absorption and thickness swelling are urea melamine formaldehyde, chitosan 4%, and thermal temperature 160oc. Keywords: particleboard, chitosan, dimension stability, Water absorption, Thickness swelling

the particleboards are made by urea-melamine formaldehyde indicated less water absorption and thickness swelling rather than urea-formaldehyde. The water absorption and thickness swelling are decreased by using chitosan. By increasing the amount of chitosan utilization, the water absorption and thickness swelling are decreased. Increasing of thermal treatment temperature reduces the water absorption and thickness swelling.

With regards to different treatments in this study, the results showed that the optimal treatment conditions for decreasing of water absorption and thickness swelling are urea melamine formaldehyde, chitosan 4%, and thermal temperature 160oc.

Different wood polymers have different properties compared to solid wood. Research has further investigated the physical and mechanical changes of these products. Therefore, this study was conducted to investigate the thermal behavior and drop contact angle of furfurylated poplar wood polymer.

Wood polymer samples were performed by saturation under pressure and polymerization of furfuryl alcohol monomer with heat catalyst. Wood samples were prepared in two levels of low and high level of furfurylation by increasing the weight percentage gain by 25.08% and 58.83%, respectively. Dimensional stability was assessed by long-term immersion according to ASTM D-4442 standard, drop contact angle by deionized water drip method and thermal behavior of samples by TGA (Thermogravimetric Analysis) and DTG (Derivative Thermogravimetry) techniques.

The results showed that volumetric swelling and water uptake of saturated samples decreased compared to control sample. Furfuryl alcohol is a polar monomer that enters the cell wall after penetrating the wood and swells the walls after polymerization, thus reducing the water absorption capacity of the wall and leaving less room for swelling. The drop contact angle was increased compared to the control samples and the highest drop angle was obtained at high level furfurylation. By reducing the spaces of moisture absorption and less water penetration inside the pores of the wood, the drop contact angle and the wettability of the wood-polymer will be reduced. The results of thermal analysis showed that with furfurylation and increasing its level, changes in TGA and DTG diagrams occur. DTG results showed that in the first phase, the amount of energy released is lower due to the high burning temperature of cellulose and the stability of the furfurylated specimens. In the second phase, the furfurylated wood-polymer showed greater thermal stability than the control and this stability increased with increasing the level of furfurylation. In the third phase, the samples of furfurylated wood-polymer at low and high levels had less energy released than the control samples. At this stage, the compounds resulting from the thermal degradation of cellulose are reduced and the flammable material is reduced compared to the control samples, resulting in a reduced energy release. In the third phase, the necessary energy is provided to break the bonds and is spent on igniting gases and tar.

According to the findings, furfurylated poplar wood-polymer has less water absorption and volumetric swelling than the control samples and undergoes less physical changes due to less water absorption and volumetric swelling. It can be expected that in the manufacture of wood products and urban furniture, the joints will be less affected by changes in weather conditions. This product also has a higher thermal stability than solid wood, which makes its use safer in cases exposed to higher temperatures.

Wood has been used for making musical instruments for a long time around the world. Manufacturers of these instruments are always trying to improve the quality of wood to make better sound by using special treatments. Santour (Iranian traditional music instrument) is usually made from walnut wood and the quality of its sound is highly dependent on the quality of wood and fabrication methods. Besides choosing the proper wood and manufacturing technics, all performers agree that if an instrument is kept in proper situation, by playing it, the sound quality will become better over the time. As the wood in instruments is under mechanical vibrations during playing, this hypothesis has been investigated that if the wood is imposed to artificial vibrations similar to real music playing, before being used to make the instrument, what changes will occur in its sound characteristics.

To do this, 10 specimens of walnut wood Juglans regia (5 tangential and 5 radial) with dimensions of 200×40×8 mm3 has been prepared. In order to be sure about the similarities of specimens, the acoustic properties of them has been measured. Then all the woods were imposed to light vibrations for 1 month and then heavier vibration for next 2 months. Two vibrating machines were designed and built which produced light vibrations by magnetic force and heavy vibrating by eccentric mass. The acoustic and mechanical properties of wood like Young's modulus (E), sound speed, sound radiation coefficient, Tanδ, were measured before and after vibrating using nondestructive Bing method. Then the woods remained without vibration for another month to find out the durability of changes and the acoustical properties of them were measured again.

The results of this research show that these vibrations have improved the acoustic properties of wood. The light vibration had almost no effect on the specimens but the heavier vibration after one month improved the sound quality of wood up to 3% including Young's modulus, sound speed, sound radiation coefficient, and Tanδ. But in the second month of imposing heavy vibrations no significant change was observed. However statistical analysis shows that this changes are not meaningful. One month after finishing the vibrations, Tanδ returned to the previous amount but improvement in E and other acoustic properties looked permanent.

The results were not statistically significant and the 3% improvement was very low but meanwhile it can be concluded that if artificial vibrating is imposed for a long time there is a possibility to improve acoustical propertied of wood.

The tree species regeneration is a critical process in the population dynamics of forests and significantly influences the composition of forest communities. Quantitative analysis of tree regeneration may provide baseline information for conservation and management strategies. Zagros oak forests have been subjected to dramatic changes in forest regeneration, cover and structure in recent decades. Zagros forests have critical national importance. These forests capture over one third of the country’s annual precipitation, and are the headwaters for 40% of the country’s rivers and streams which provide water to the dry central plateau of Iran. Given the national and regional importance of Zagros forests, it is extremely useful for restoration management to evaluate spatial distribution of tree regeneration. Disturbing of ecosystems, changes the dynamic of species and ecosystem processes. Ecosystems are therefore moving in a self-organizing way towards a more efficient use of energy/nutrients to the total energy input. This self-organizing of the ecosystem is an inherent feature of non-linear interacting systems. Techniques used to study non-linear systems could be able to quantify the structure of complex objects and spatial dynamic of plants.

The mathematical features of spatially complex systems are often fractal. Fractal has the potential to exposure a new way to understand and analyze such natural spatial phenomena, which are not smooth, but rough and fragmented to self-similarity. We investigated the spatial patterns of tree regeneration density and diversity in 126 plots (100 m2). The study was conducted at a preserved area (12 years) in Zagros forest of western Iran. We applied autocorelation methods to examine the spatial structure in distribution of regeneration. Fractal analysis was also used to characterize the complexity of the spatial patterns.

We found that preservation favored density and diversity of tree regeneration in this area. On the whole the variables have weak autocorrelation but regeneration density of C.microcarpa, total regeneration density, regeneration height and Shannon index are the variables which have the most autocorrelation. On the other hand, fractal dimension, representing the unpredictability of spatial patterns, is high for trees and regeneration. This implies that although spatial dependence exists, it is generally fairly weak.

These results revealed the scattered and homogeneous spatial distribution of trees and their regeneration. Indeed, our results showed a recovery of regeneration but not the spatial structure of it. It seems that conservation efforts must be continue to complete the recovery of regeneration and their spatial structure.

The roots of the plants are used as a kind of materials in the slopes preservation and resistance. Because in addition to helping to preserving and resisting the environment, it has recovery ability and has no harmful and negative effects on the environment and has no additional costs too. Plant cover is caused for pastiness between soil particles for having root system and has significant impact in slope stabilization, for this reason, the biological characteristics of different species has great importance. The quantity of reinforcement depends on root biotechnical characteristics such as root density and tensile strength. In this study assessed these biotechnical properties.

In this study, two non-native afforested stands of pine (Pinus Sylvesteres) and acacia (Robinia Peseudo acasia) and two natural stands with native species of hornbeam (Carpinus Betulus) and summer alder (Alnus Subcordata) with similar habitat conditions (altitude,Slope and direction of slope, soil type, geology, etc) in the forest of Neka city (Neka-Zalmarud forestry plan) was and Six trees of each species were randomly selected for later analysis. The Root Area Ratio and tensile strength were investigated. Profile trenching method was used to analyze and compare their root distribution. The walls of the profile are divided into 10 cm horizons. Number and diameter of protruded roots in each depth were measured. Finally, the percentage of Root Area Ratio in each horizon was calculated. Standard Santam was used to determine the tensile strength of roots. Root samples were collected at the bottom (30% slope) of trees.

The results indicated that the Root Area Ratio were decreased with increasing depth According to the exponential function . The Root area ratio in non-native species is higher than native species. Which has obtained for Carpinus Betulus, Alnus Subcordata, Robinia Peseudo acasia and Pinus Sylvesteres, 0.033±0.002, 0.081±0.002, 0.026±0.018±0.177±0.015 percent respectively. The diameter range of the tested roots was 2-9 mm. The results of tensile strength tests showed that with increasing diameter, the amount of tensile strength according to the According to the exponential function decreased. There is a positive power relationship between root diameter and tensile force.

In this research tensile strength of native species is more than non-native one that has obtained for Carpinus Betulus, Alnus Subcordata, Robinia Peseudo acasia and Pinus Sylvesteres, 31.93±10.3, 17.57±6.98, 18.4±2.41, 9.77±5.46 Mpa respectively. The results of this work may help us when applying an efficient bioengineering technique

Intraspecific interaction is important because it occurs between the same species individuals that have similar ecological nests. The objective of this study was to evaluate intera-specific interaction of poplar trees (Populus euhratira Olivier.) using mark correlation functions.

The position of all trees with DBH>2.5 cm were recorded in two pure and mixed stands in Behbahan Chaharasyab area with area of 4.5 and 9.1 ha, respectively. Tree height (H), diameter at breast height (DBH), crown diameter (CD) and light crown length (LCL) were measured as mark variables. Point spatial pattern analysis was used to study the spatial pattern and intraspecific interaction. Marked correlation (MCF) function was used to reveal the spatial relationships between the poplar individuals trees in terms of various characteristics such as total tree height, diameter at breast height, crown diameter and light crown length.

The results showed that in pure stand, a significant negative correlation was observed between the DBH of trees at a distance of less than 5 and more than 20 m. Between distances of 5 to 20 m, an independent state was observed between the individuals. There was a positive and negative correlation between the crown diameter of poplar trees from a distance of 5 to 40 m and more than 45 m, respectively. There was a significant positive correlation between the total height and the light crown length of the trees from a distance of 5 to 30 m. At a distance of more than 30 m, the independence was seen between the individuals. In mixed stand, the independence status was observed between DBH of trees up to a distance of 40 meters. A positive correlation was observed at distances greater than 40 m. There was a negative correlation between trees CD at all distances. The independence was seen between H and LCL of trees at most distances.

In pure stand, depending on different distances and marks, various states of interaction including negative, positive and independence were seen between the tree individuals. While in mixed stand, except for the state of negative interaction that was seen in relation to the crown diameter, in other cases, the condition of independence between different individuals was observed in terms of the studied marks. DBH showed similar conditions in both pure and mixed stands. CD showed positive and negative correlations between individuals in pure and mixed stands, respectively. There was a positive correlation between H and LCL of individuals in pure stand while independence was observed in mixed stand. Overall, it is useful to study the interaction between poplar trees to understand the dynamics, growth process and mechanisms that endanger this valuable species.

Forest structure is a key factor in growth, yield and how changes occur in the forest stands, and evaluating the structure of plantations can play an important role in improving afforestation and timely implementation of forestry treatments in each stand. This study aimed to evaluate structural characteristics of plantation forests in the Saib Tabrizi forest park located on Tabriz, after 25 years of planting have passed, and abandon its management.

For this purpose, after initial field surveys, three one-hectare plots were selected and based on quantitative indicators, the structure of each plot-sample was investigated. In each plot, structural characteristics of all trees (species type, diameter at breast height, tree height, canopy height, and canopy diameter) were measured and the distance method (based on nearest neighbor’s) were used to quantify stand structure. In order to study of stand structural some index including nearest neighbors distance index (density of trees), uniform angle index and Clark and Evans index (variety of location), Mingling index (species mixture), diameter and height differentiation indices (dimensional differences of trees), and complex structural diversity index (tree diversity) were used.

Based on the results, the average density of trees was 448 per hectare. In the studied sample plots, the average DBH was equaled to be 12.9 cm, the average height of the trees was 5.1 m and the average basal area was calculated to be 0.013 m2 per hectare. The highest abundance among the species belonged to the species of Pinus nigra with 50.4% and Robinia pseudoacacia 32.4%, respectively. The results of the uniform angle index showed that a cluster pattern in spatial distribution of trees, however Clark and Evans index showed a regular pattern. According to the Mingling index, the studied stands have relatively moderate mixing. The height and diameter differentiation indices showed that the dimensions of the trees had a slight difference, and have a homogeneous structure. According to complex structural diversity index, tree diversity was obtained at the low level.

In conclusion, it can be said that after nearly three decades of planting trees in this park, tree communities have maintained the homogeneity of their structure, and trees have moderate mixture. Therefore, it can be stated that the development of forest structure in the research area is slow. Hence it is recommended to increase the biological sustainability, silvicultural treatments are needed to increase mixture and heterogeneity of structure. The results of this study can provide objective justifications for the importance of consciously creating forestry strategies in the country's forestry as a missing link in the forest management.

In recent years the protection of biodiversity became an important goal in forest management and caused some conservative management approaches such as creating managed areas or areas in which no management has been implemented. In the past decade habitat trees came under focus. Micro-habitats are structures on dead or alive trees in the forest including changes such as wounds and fractures caused by biological process and provide places for forest living organisms. Nowadays the necessity of habitat trees protection has been emphasized in forest management and policy. This study aimed to assess the diversity and frequency of tree micro-habitats in Persian ironwood- hornbeam forest stands at Bahramnia Forestry Plan (Gorgan).

Therefore for assessing the trees’ micro-habitats 4 square sample plots each one with the area of 2500 m2 were selected and allometric characteristics (diameter and height) of all trees with the diameter more than 7.5 cm were recorded. Then according to an instruction the type and abundance of micro-habitats were assess and recorded for all trees. A binocular was used for assessing the micro-habitats located on top of the tree crown and their upper trunk. The habitat value as well as economic value of all trees have been calculated using Integrate+ software. Correlation test was used to assess relationship between occurrence and frequency of micro-habitat with quantitative characteristics of all trees.

The result showed that the studied stand is an uneven-aged stand and Persian-ironwood tree species is the most abundant tree species within it. The hornbeam trees have the highest average diameter and height, as well as the highest diversity and frequency of micro-habitats. The most frequent micro-habitats observed on the trees were EP, GR and CV. The result of correlation test showed a significant relationship between tree diameter and micro-habitats abundance. By increasing in the tree diameter the number of micro-habitats significantly increased.

Totally the results of this study show that there are different kinds of micro-habitats in the studied forest stands. Also the tree diameter is one of the factors that affects micro-habitats’ abundance. Therefore it is of importance to maintain some of the high diameter trees in the forest stand. Understanding the effective factors on occurrence and abundance of the micro-habitats can be an important help in protecting forest biodiversity. Studies on habitat trees in Iran’s forest ecosystems (particularly Hyrcanian Forests) is rather a new issue which can be an effective help for better understanding of the other functions of these ecosystems, especially ecosystem services and increasing biodiversity.