فصلنامه جنگل و فرآورده های چوب
سال شصت و پنجم شماره 2 (تابستان 1391)

The objective of this study was to determine the floristic composition of the persistent soil seed bank and comparison of its seed bank composition with its above- ground vegetations in Khybus protected forest that is one of the best and most virgin Habitats of Box trees in Hyrcanian forest. The study of ground vegetation was carried out with releve method and the soil seed bank was estimated using the seedling emergence method. For this purpose 64 releves with 400 m2 area were made by systematic- selective method and considering indicator stand concept. For sampling of soil seed bank within each releve, two soil samples were randomly collected by hammering a 20 cm × 20 cm square (400 cm2) hollow metal frame into the soil to a depth of 10 cm. 52 species with mean of 3880 seeds per m-2 emerged from soil seed banks. Pteris cretica L., Hypericum androsaemum, Rubus hyrcanus Woron., Carex sylvatica L., Rubus hyrcanus Woron, Athyrium flix- femina (L.) Roth, Atropa belladonna L. and Diospyrus lotus L. with the mean density of 3132, 213, 154, 125.4, 98.5, 34.4 and 17 seeds per m-2 were exhibited as the most abundant taxa respectively. Forbs, with the possession of the 64 percent seed bank flora, were the most numerous growth forms in soil seed bank. The comparison of seed bank and above vegetation revealed that the similarity between soil seed bank and vegetation is low. Finally, we are concluded that persistence soil seed bank of the study area like other areas, is not capable of restoring the ground vegetation of plant communities.

Geographic Information System (GIS) is one of the most important tools to prepare forest management plan and, in general, as a tool for management, sustainable logging and future planning based on the derived statistical data from forested regions. The purpose of this study was spatial simulation of trees in forest to have in hand an example of an uneven aged forest (simulated forest). By means of the simulated forest, it is possible to test different statistical methods and various management activities before they are carried out in real world. The study area, Gorazbon, is a district of Kheyrud research-educational forest, with 1001 hectares area located in East of Nowshahr city. The inventory was implemented using systematic random sampling. Afterwards, trees were randomly distributed within the compartments of this district, using the results of full callipering inventory with Arc GIS 9.3 software and forest was simulated. In this stage, the inventory process was implemented in simulated forest similar to the inventory of real forest. These results were compared with the results of the ground inventory, and no statistically significant difference was found in any of repetitions. Consequently, it can infer that the simulated forest is remarkably applied to the forest inventory implementations. Furthermore, it is a functional tool to provide forest management plans of Kheyrud forest. To say in other words, this makes possible to test different methods of forest inventory and also type and dimensions of plot and inventory net unquestionably.

Flotation deinking is the prominent technology for ink removal from waste paper. In this study, flotation deinking was carried out applying two levels of sodium hydroxide and five levels of hydrogen peroxide on a mixture of waste papers consisting of: 30, 30 and 40 weight percent OMG, ONP and MOW, respectively. The deinking efficiency was evaluated based on brightness, yellowness and dirt count of hand sheets. The results showed that increasing hydrogen peroxide dosage can increase hand sheets brightness, however, at higher hydrogen peroxide levels, the brightness was reduced probably due to the presence of more NaOH and the limitation of hydro peroxide efficiency for chromophore elimination. Optimal ratio of H2O2/NaOH, significantly increase the efficiency of deinking at lower alkali usage. This research showed that higher deinking efficiency may not be necessarily reached applying more chemicals, but optimal chemicals ratio plays an important role in deinking efficiency.

The aim of this research is investigation on influence of single wall carbon nanotubes (SWCNTs) on the physical and mechanical properties of wood fiber- LDPE composites. SWCNTs with 1, 2 and 3 wt% were dispersed in acetone and then in absent and present MAPE (0 and 3% wt) were mixed with wood fiber and HDPE by Haake internal mixer and then the wood plastic composites were manufactured by hot press method. The results show that SWCNTs and MAPE improve physical and mechanical properties of the composites. In absent and present MAPE, the composites with 3% SWCNTs exhibited the lowest water absorption and thickness swelling content and the highest flexural modulus and strength, respectively. SEM micrograph showed that, with adding compatibilizer dispersion of fibers and carbon nanotube are improved. The composites with 3% MAPE and 2% SWCNTs exhibited the highest impact strength. Based on SEM micrograph, with increasing carbon nanoyube up to 3%, these nanoparticles are agglomerated in the matrix and provide points of stress concentrations and crack propagation.

Nondestrutive evaluation of wood quality of fast growing standing trees such as poplar has an important role in optimal management of wood production with desired quality and properties. Tha aim of this research was the use of stress wave technique for nondestructive evaluation of poplar standing trees (Populus deltoids) and to study the effect of intercropping (with wheat) and spacing on wood quality. For this purpose, stress wave velocities were measured in radial and longitudinal directions of poplar trees in four intercropping treatments with different spacing of 3×4 m, 3×6.66 m, 3×8 m, 3×10 m and treatment of net poplar with spacing 3×4 m. The velocities of stress wave in radial and longitudinal directions of poplar trees were determined using stress wave equipment. The results showed that at same spacing (3×4m), the radial and longitudinal velocities of stress wave in net treatment are significantly higher than those of intercropping treatment. The results also showed that increasing spacing in intercropping treatments will increase the stress wave velocities in both directions significantly. A poor regression relationship was obtained between stress wave velocities in radial and longitudinal directions

The aim of this study was to introduce the most successful exotic coniferous species for forest plantation projects. The trial conducted in 1993 at low altitude of Neka region in Mazandaran Province of I. R. Iran (North Forests), under Compeletly Randomized Block Design (CRBD) with three replication and eight treatments. The treatments consisted of six Pine species (P. taeda, P.radiata, P.brutia, P.nigra var. austriaca, P. pinaster and P. longifolia), Cryptomeria japonica and Cedrus deodara. The species growth characteristics including survival, height, diameter at breast height and also qualitative characteristics were assessed and measured after 18 years, Soil physical and chemical properties were determined and climate characteristics were identified. The results of statistical analysis showed that there were statistically significant differences between qualitative and quantitative parameters of species. Analysis of characteristics showed that Loblolly pine (P.taeda L.) and Brutian pine (P.brutia Ten.) were the most promising species; in the second stage Hymalaya Cedar (Cedrus deodara D.Don.) and Japanes cedar (Cryptomeria japonica D.Don.) were promising species, respectively.

The withdrawal strength of nail and screw fasteners was studied in rice straw fiber-thermoplastic composites. Virgin high-density polyethylene (HDPE) was selected as the composite matrix. Three levels of dry rice straw fiber, 45%, 60% and 75%, based on weight and passed through a 40-mesh size screen were mixed with the polymeric matrix without or with 2% (based on weight) maleic anhydride grafted polypropylene (MAPP) as coupling agent. A dry-blending method was used for compounding the materials. The 12 formulations for the polymer composites were used to prepare samples with dimensions of 25 cm by 15 cm by 1 cm. 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 keeping the composites at room temperature for 15 days, the withdrawal strengths of nails and screws were measured according to BS Standard for dry composites. Withdrawal strengths were also measured after immersion of the composites for 24 hours in distilled water (wet condition) (cycle 1). Wetting for 24 hours followed by drying for 24 hours was then repeated for the other 3 cycles. The results showed that the withdrawal strength of screws is more than that of nails. Also, rice straw fiber content may significantly influence the withdrawal strength of fasteners, especially at higher fiber to polymer ratios. Furthermore, it was found that the coupling agent slightly affected the withdrawal strengths of the fasteners. The results also showed that withdrawal strength of fasteners are significantly reduced at more wetting cycles.

In this research, the effect of Dolomite mineral filler on mechanical properties of composites produced from beech wood flour and polyethylene using hot pressing method was examined. In order to evaluate the effect of coupling agent on bonding between cellulosic fibers phase and the matrix, two levels (1%, 3%) of polyethylene grafted with maleic anhydride were used. Standard experimental samples were prepared and properties such as static bending, tension, impact and hardness, were measured. The results showed that, when the mineral material content was increased, all mechanical properties except hardness decreased. In principle, addition of MAPE to the compound improved mechanical properties.

The effect of nano SiO2 and silane coupling agents on practical properties of plywood was investigated. After plywood production with layers of hornbeam wood (Carpinus betulus), physical and mechanical properties were analyzed. Variables were the type of silane coupling agent (vinyl tri methoxy silane and γ-amino propyl tri ethoxy silane), the amount of nano SiO2 (1% and 2%) and the amount of silane coupling agent (1% and 2%). The lowest water absorption and thickness swelling were observed in the case of boards produced with 1% treated nano SiO2 by 2% vinyl tri methoxy silane, and those with 1% treated nano SiO2 by 2% γ-amino propyl tri ethoxy silane had the highest bending strength and modulus of elasticity. The highest shear strength was found for the boards produced with 2% nano SiO2 treated by 1% vinyl tri methoxy silane. The results of this study revealed that utilization of nano SiO2 treated by silane coupling agent as filler for urea formaldehyde resin is effective in improving the physical and mechanical properties of plywood.

The aim of this study was to estimate recreational value of Nour Forest Park and measure of visitor’s willingness to pay for recreational benefits of the concerned park based on contingent valuation method and double-bounded dichotomous choice questionnaire. To do this, 353 questionnaires were completed in the park. To investigate the effect of explanatory variables like age and gender on individual’s willingness to pay, logit model was used and its parameters were estimated based on maximum likelihood method. The results showed that 80.2 percent of visitors had willingness to pay for recreational use of Nour Forest Park. The mean of willingness to pay for recreational value of the concern park was dollar 0.42 per visit and the recreational annual value was estimated $/ha 114.5. The results revealed that, forest parks had considerable recreational values that this may help the decision makers and social and economic managers, in the preservation planning and sustainable utilization of natural resources.