فصلنامه جنگل و فرآورده های چوب
سال شصت و پنجم شماره 3 (پاییز 1391)

Considering the global warming and climate change topics, biomass estimation of trees has great importance in theory and application. Measurement of biomass is a costly and time consuming operation And to reduce these difficulties, a large numbers of sampling methods were innovated. One of these methods is the “subsampling”. In this research, accuracy of this sampling method for estimating biomass of total and different tree components of two planted coniferous species; Eldar pine (Pinus eldarica) and Arizona cypress (Cupressus arizonica) were examined in Mobarake Steel factory. Five sample trees from each species were felled down and each component of trees were separated and weighted. Therefore, actual biomass of different tree components was obtained. To test subsampling method, tree crown was divided to three parts, upper, lower and medial part and from each part, a number of branches were selected randomly and base diameter of every branch was recorded. Using nonlinear regression analysis, models of estimating biomass were obtained. The results showed that, all models were significant at 99.9% confidence level. The minimum and maximum coefficients of determination (r2) of these models were 0.8 and 0.92 for pine and 0.91 and 0.96 for arizona cypress respectively. The least and the most relative bias for pine belongs to estimation of total biomass (0.7%) and main branches (15.1%) and for arizona cypress belongs to estimation of main branches (4.9%) and small branches (29.4%). Based on the results, subsampling method is an appropriate method for estimating trees crown biomass.

Tourism is considered in many natural regions of world as a development strategy and specifically ecotourism is a suitable option for achieving sustainable development. Therefore it is necessary to identify widespread effects of ecotourism on the natural resource. This study assessed the effect of recreation in four regions including intensive recreation, extensive recreation, grazed after intensive recreation and control region in Nour Forest Park. In each region herbaceous cover, regeneration rate, bulk density and soil porosity in surface and subsurface as well as organic matter were measured. The results showed that intensity of recreation is effective on the amount of herbaceous cover, the amount of regeneration, the amount of compaction and the porosity in 0-5 cm soil depth but had no impact on the amount of soil organic matter. In the intensive recreation region the amount of soil compaction in 0-5 cm and the porosity were increased and decreased respectively in comparison with the control region. Intensive recreation region had very low herbaceous cover and regeneration compared to the control region which is the results of damage of intensive recreation. The result showed that a extensive recreation has low impact.. Herbaceous cover was slowly rising in grazed region but regeneration is more than other regions. Soil bulk density in grazed region was not significantly different compared to the control region that can indicate the recovery of intensive recreation region to natural forest condition. The results suggest that determining some intensive recreation region and periodic fencing them is a may prevent destruction of nature.

Tree felling includes all activities undertaken to fell standing trees and prepare them for extraction. This study was conducted in Gorazbon district in the Hyrcanian forest. The objectives of the study were to discover the special characteristics in the time consumption of manual tree felling, productivity and costs, and develop regression model of tree felling in selection conditions. The continuous time study was conducted with professional operators for chain-saw felling and the cycles were broken down into time elements. Different variables were measured such as time consumption, inter-tree distance, tree species, tree volume, and tree diameter. Rest and meal time of working crew was the most time-consuming element in felling, followed by under-cut and walk-to-tree times. The operational delay was the most time-consuming delay time. The results showed that time consumption for under-cut and backcut was increased with increasing diameter. Labor costs accounted for 44 % of the hourly cost while only 2 % was related to machine cost. A significant linear relationship was found between cycle time and diameter. Productivity of chainsaw felling was increased related to tree DBH as a power function. The cost of chainsaw felling with and without delay time were USD 3.03 and 2.7 per cubic meters, respectively. The cost of felling was increased as simple exponential function when DBH of harvested tree was decreased. However, the unit felling cost for chainsaw operation decreased as size of tree increased. Total felling cycle time without delay averaged 4.1 minutes and with delay time were averaged 4.65 minutes.

In this study, the effect of storage conditions of spruce wooden pallets used in petrochemical companies in Mahshahr on the development of blue stain fungus (Ophiostoma piceae) was studied. The effects of storage temperature at three levels of 20, 30 and 40 °C, two levels of relative humidity 55 and 75% and also ventilation and stickering were examined. Ventilation was carried out twice a day for 1 hour. The average moisture content of the wooden pallets ranged from 25 to 31 percent and the samples were prepared from four areas of the pallet, including top board, bottom board, stringer board and blocks. Results indicated the significant effect of each storage condition. A reduction in relative humidity, ventilation in the storage and stickering reduced the blue stain intensity. An increase in temperature from 20 ◦C to 30 ◦C resulted in a significant reduction in blue stain but no significant difference was observed between the temperatures of 30◦C and 40◦C. Overall, it can be concluded that the blue stain fungus (Ophiostoma piceae) development can be avoided by the control of relative humidity, temperature, ventilation or stickering.

In order to study the effect of grazed and soil surface scrafication on regeneration and soil physical and chemical properties in Zagros forests, three areas including preserved woodland with soil scrafication, preserved woodland without soil scrafication and no preserved woodland in forests of Aleshtar in Lorestan province were choosen. Soil sampling and seedling counting were done using random sampling. Ten sample plots were selected in each study area and soil properties and number of seedlings were studied in plots. The most important physical and chemical soil properties were analysied in lab. The results of One-Way ANOVA showed significant differences in Bulk Density (BD), Particle Density (PD), C, P, K and N between study areas. The results of this research indicated the number of seedlings in preserved and no preserved woodlands differed significantly. The correlation between soil properties and regeneration showed considerable effects of the grazed and soil surface scraficationon on soil properties and the number of regeneration. These results indicated that these two approaches can be considered as capable management strategies in revival of Zagross forests.

Chemical structures of different isolated lignins were elucidated to determine the uncondensed structures through DFRC degradation method. Milled wood lignin and the so called enzymatic lignin were isolated and degraded via a modified chemical oxidative-reductive DFRC procedure. In the modified method, the degraded products were functionalized with methylation, acetylation and propylation modification processes to exclude the uncondensed phenolic β-O-4, uncondensed α-O-4 and uncondensed etherified β-O-4 groups. The subsequent characterization of the products by gel permeation chromatography and gas chromatography showed that mnzymatic lignin had more uncondensed structures compared with milled wood preparation which could be a consequence of less degradation during the isolation process. The data were further evaluated by quantitative 13C NMR and the calculation of degree of condensity.

In this paper, effect of Ag nanoparticles different contents on heat transfer during press cycle and physical and mechanical properties of particleboard was investigated. Mechanical strength including Internal Bonding (IB) and Bending Strength and physical properties including Water Absorption (WA) and Thickness Swelling (TS) after 2 and 24 hours soaking was determined. Heart transfer process from hot press plates to core layer of the mat during press time was recorded by thermocouples. Energy Dispersive X-Ray Spectroscopy (EDX) and Scanning Electron Microscopy (SEM) result prove presence and dispersion of nanoparticles in glue line well. Results indicate that Ag nanoparticles increase heat transfer to the core layer and cause IB improvement. But nanoparticles had negative effects on physical properties and increased WA and TS after 24 hour soaking. Heat transfer acceleration during hot press cycle is a way to reduce press time that results in efficiency increase by preserving essential strengths.

Enzymatic deinkability of the newly printed and accelerated aged newspapers is evaluated. Enzymatic deinking was carried out with cellulase prepared from Aspergillus niger in a slightly acidic medium. The results showed that in both groups of papers, enzymatic deinking led to significant changes in freeness and yield values of the pulps as well as thickness, density, brightness and opacity of the prepared handsheets as compared with those of the control sample (without deinking). In addition, comparison of the newly printed and accelerated aged newspapers showed that in the first group of papers, both enzyme value and reaction time significantly influenced pulp freeness whereas in the second group only reaction time was the influencing factor. On the other hand, no significant differences were observed between the optical and physical properties of both groups of deinked pulps, i.e., cellulase acted equivalently in deinking of both groups of papers and accelerated aging had no negative effect on its efficiency.

In this study, the effects of fiber content, type and size on board density and withdrawal strength of fasteners (nailed and screwed) in joints made in natural fibers-plastic composites produced through a dry process were investigated. Wood-plastic boards were made at a nominal density of 1 g/cm3 and dimensions of 30×20×1 cm. Polypropylene (PP) as the matrix and poplar wood fiber and rice straw fibers as the reinforcement were used together with 4% (based on weight) maleic anhydride grafted polypropylene (MAPP) as the coupling agent. Three levels of dry poplar and rice straw fibers, namely 45%, 60%, and 75% based on the composition by weight at two particle sizes of 20-40 mesh and 40-60 mesh were mixed with PP. Totally, 12 formulations with 3 replications were considered. The final composites were made by pressing the prepared mats between the hot plates of a compression press by employing combinations of temperature and pressure in three stages. After storing the composites at room temperature for 15 days, the density of the boards and withdrawal strength of fasteners were measured. The results showed that fiber content may significantly influence the density of the samples and the fiber size of 40–60 mesh may lead to a higher density. In addition, it was found that poplar fibers (the type of fiber) results in higher withdrawal strength of fastener in the composites than rice straw fibers. Furthermore, the withdrawal strength of fasteners was reduced as the fiber content was increased. However, this effect is dependent on fiber size and may be negligible at higher fiber contents.

In this survey, the possibility of somatic embryogenesis in four different pine species was studied using different compositions of plant growth regulator. The embryogenic tissue induction phase was performed using mature zygotic embryo explant, culture medium DCR and using different levels of plant growth regulator in Pinus brutia, P. nigra, P. radiata and P. sylvestris species. The experiment was done through a completely randomized design with a simple factorial arrangement. Embryogenic tissue was measured in two phase, 30 and 40 days after the initial culture. After sterilizing of seeds kept at 4°C, and removing their coats, zygotic embryo was separated from megagametophyte and put into the Petri dish containing solid tissue culture. All the Petri dishes were maintained in darkness at 25°C. After 2 weeks the first signs of embryogenic tissue induction were observed. The results showed the significant effect of composition of plant growth regulator and specie on the amount of embryogenic tissue induction and the best result was obtained from P. brutia in hormon composition of 10µM 2,4-D+5µM BA. In order to proliferation of embryogenic tissues, subculture of tissues was performed every two weeks in new culture medium for six weeks. Finally, in order to maturation of somatic embryo from embryogenic tissue, the segments of embryogenic tissue with 5×5 mm dimensions were transferred to DCR culture medium. After two months, although quasi-embryo and abnormal structures got seen but the production of complete embryo from embryogenic tissue was unsuccessful and transition from preembryony phase and conversion to embryo with developed cotyledons failed.