فصلنامه جنگل و فرآورده های چوب
سال شصت و ششم شماره 2 (تابستان 1392)

In this study seed germination problem of this genus regarding different various methods were tested. Pretreatments were conducted using giberlic acid، KNO3 & Sulfuric acid. Three endemic species including Crataegus babakhanloui، C. aminii، and C. persica were studied. To evaluate the germination responses، experiment were carried out as a completely randomized design with three replications that each replication contains 30 seeds. Results indicated that the most effective treatment for C. aminii is KNO3 1% with 38. 66% seed germination. Sulfuric acid treatments (98%، ‹15) and Sulfuric acid 50% for ‹15 and ‹30 minutes had no germination. In C. babakhanloui، kno3 1% treatment with 44% germination and Sulfuric acid treatments (98%، ‹15) with 9. 33% germination has the highest and the lowest success respectively in compare the other treatments. In C. persica KNO3 0. 5 % treatment with 49. 33% seed germination has the highest germination rate، in contrary there was no germination in Sulfuric acid treatments (98%، ‹30). Despite of better performance of potassium nitrate treatment، it does not seem a practical method for germination. In this case for mass germination stimulus، sulfuric acid treatments look more practical.

Forest roads are known as the most important factor of sediment production in forest ecosystems. Because of the importance of this issue، several models developed based on empirical relationships to estimate sediment yield. In this study، the amount of annual sediment yield derived from a forest road network was estimated as tons per year using CULSED model in ArcGIS. Base spatial layers such as: topography، stream، roads، and culverts were used in this model. Additional data such as the bed rock، vegetation، average precipitation، road age، the amount of traffic، road surface and road gradient were used in the model. First، digital databases were developed and the model was run. Then places with high rates of sediment yield were specified and some culverts were designed in appropriate places to decrease the amount of sediment production. The results showed that the amount of sediment with regards to existing 38 culverts was 13. 2 tons per year. Adding 16 proposed culverts in the areas with high sediment production resulted in 36% decrease in sediment yield. So، given the importance of reducing sedimentation from roads in the forest، this tool can be used before road construction to find optimal number and location of culverts by engineers. However، due to lack of available data and a native model، some uncertainty will be encountered that should be considered.

To study the frequency distribution of the data for the height of trees in uneven-aged stands in Gorazbon forest and its modeling، some statistical distribution were used. The utilized data belong to 196 trees (Fagus orientalis، Betulus carpinus، Quercus castaneifolia، Alnus subcordata، Acer velutinum etc.) that were extracted from the data related to the forest management plan of Gorazbon district located at Khyroud forest. The range of the trees’ height measured was between 5 and 51 meters which is an indication of height variable in the northern forests. After initial calculations، four distributions Weibull، Gamma، Normal and Lognormal for frequency distribution modeling of height variable were selected and related pertinent calculation were done. The results of Anderson-Darling test and P-P plot showed that lognormal distribution is not an appropriate model for frequency distribution modeling of trees’ height. Among the other three distributions، Weibull، Gamma and Normal are respectively more suitable.

Drumstick (Moringa peregrina (Forssk). Fiori) is one of the valuable tropical forest tree species. It is endangered since long time ago، due to its particular characteristics، extensive seed harvesting and weak regeneration. This research was conducted in order to investigate the effects of several culturing media on micropropagation of three plant populations of the species and their interaction effects. Immature seeds collected from Chanf، Benet and Kenshki located in Sistan and Baluchestan province، Iran، were used to perform the study. Buds of germinated seeds were aseptically grown on eight combinations of two basic culture media، MS and half- MS and various concentrations of BA and 2iP hormones. Several characteristics were recorded on the produced plantlets. The plantlets rooted on two successive rooting media and planted on a mixture of pit and vermiculite. A few samples of the studied plant populations showed strong regenerative callus induction. Analysis of variance revealed significant differences between the studied populations on number of branches، active bud numbers، callus volume، and length of the longest branches on the plantlets. Moreover، a significant difference at one percent of probability was observed between the studied growing media based on the majority of the studied characteristics. It seems the reduction of the concentration of macronutrients of growing medium would lead to significant increment of shoot production on the species. Regarding the different origins of the studied plant samples، the effect of different genotypes on callus induction was clearly observed.

Nowadays، regression analysis is a common method to estimate trees stem volume. Althought trees trunk volume can be estimated with a certain accuracy، however there are many constraints such as normality of variables and homogeneity of errors variance، when foresters use this method. In this study، Artificial Neural Networks (ANN) as a subset of the technology of Artificial Intelligence (AI)، was used as a new method to estimate the volume trunk. For this purpose، 101 trees were selected. Marked trees were located in Research and Educational Forest of Tarbiat Modarres University (REFTMU). DBH، diameter at stump height، end diameter trunk، trunk height and total tree height were mesuared with high accuracy during tree marking. Two neural network models، multi-layer perceptron (MLP) and radial basis function (RBF)، were developed to estimate trunk volume. The results showed that with increasing the number of variables، that have more correlation with trunk volume،correlation coefficient of neural networks increased from 0. 80 to. 95. Also the RBF neural network was more accuracte in trunk volume estimation than to MLP neural network. Comparing evaluation criteria for ANN with stepwise regression showed that MLP and RBF neural networks had RMSE value 1. 18 and 1. 05، respectively while the RMSE value of regression was 2. 57. Also the regression correlation coefficient is less in compared with two models neural network.

In this study، the effect of nano-SiO2 in four levels of 0، 1، 2، and 3 percent (weight of cement) and the type of lignocellulosic materials on physical and mechanical properties of woodcement boards manufactured by old corrugated container (OCC) and rice husk have been investigated. Totally 8 treatments were taken that each one had three repetitions. Samples were provided according to DIN EN 634 and physical and mechanical properties، including modulus of rupture، modulus of elasticity، shear strength parallel to surface، hardness، water absorption and thickness swelling after 2 & 24 hours immersion in water، have been measured. The Results indicated that in case of using nano-SiO2، OCC-cement boards incorporating 1 percent and rice husk-cement boards incorporating 2 percent nano-SiO2 had the highest bending strength and modulus of elasticity. Shear strength parallel to surface and hardness were further in boards incorporating 2 percent nano-SiO2. Also، using rice husk in board manufacturing has decreased the water absorption compared to OCC.

This study was conducted to evaluate stress carrying capacity of miter corner joints fabricated with dovetail fitting in frames made with particleboard and medium density fiber board (MDF) under diagonal tension loading. In this study، tests were carried out to determine the effects of dovetail fitting height (9 and 14 mm)، and adhesive types (polyvinyl acetate (PVAs)، cyanoacrylate (CA) on stress carrying capacity of dovetail joints under diagonal tension loading، and the joints without adhesive were compared. The results indicate that stress carrying capacity has increased، with the increase of high dovetail. The stress carrying capacity of joints constructed with CA adhesive was higher than that of those constructed with PVAs and without adhesive. Furthermore، the stress carrying capacity joints constructed with MDF was higher than that of those of particleboard. The lowest ultimate stress carrying capacities (2. 61Mpa) were obtained at 9 mm high dovetail of dovetail joints made of particleboard and without adhesive. Highest bending moment resistance (8. 61Mpa) was observed at 14 mm high dovetail with CA adhesive in medium density fiberboard.

The main objective of this work was to study the effects of nanoclay (NC)، microcrystalline cellulose (MCC)، and coupling agent (MAPP) on the mechanical and thermal properties. The results showed that mechanical properties of the composites made with MCC were significantly superior to those of unfilled. Addition of MAPP could enhance the mechanical and thermal properties of the blends، due to the improvement of interface bond between the filler and matrix. The significant improvements in tensile properties of the blends composites made with MAPP and NC were further supported by SEM micrographs. The thermo gravimetric analysis indicated that the addition of 5 wt. % MAPP and 3 wt. % NC remarkably increased the thermal stability of the blends compared to the pure PP. It is to be noted that MCC could not improve the thermal stability.

Biomass pretreatment plays a crucial role in a lignocelluloses feedstock-based biorefinery for processing of three major output streams (cellulose، hemicelluloses and lignin) into chemicals and biofuels. Biomass pretreatment includes processing of lignocellulosic material under aqueous، dilute acid or alkaline media to obtain a cellulosic fraction، which in then produce added-value products. In this study، the effect of pre-extraction on alkaline pulping (soda) and papermaking properties of Bagasse was investigated. Samples of sugar cane bagasse were hydrolysed by auto hydrolysis with hot-water. Results showed that pre-extraction optimum conditions were 30 min، 135OC and 10 min 170OC، resulted in extraction yield and holocellulose removal of 86% and 11%، respectively. Also، the pulping optimum conditions were alkali charge 17%، 165 OC for 1h. The results indicated that for unbleachable pulp production the pulping yield from the extracted bagasse is higher than the unextracted bagasse but the bleached pulp from unextracted bagasse have higher yield compared to the extracted bagasse. Pulp strength properties such as the tensile index and the burst index were found to be lower when pre-extraction was applied.

Development of wheat straw chemi-mechanical pulping to produce pulp which can partially substitute OCC pulp and suitable for small scale implementation was investigated. Four levels (10، 12، 14 and 16% based on oven dry weight of straw) of NaOH at pulping time of 40 minutes and 95°C pulping temperature were used. After digester yield varied between 64. 6 and 72. 7% and the total yield after defibration was measured as 55. 45% and 58. 3%. Unrefined pulp freeness varied between 708 and 765 ml CSF. Pulps were refined to about 350 ml CSF in a PFI mill and then hand sheets were made for strength evaluation. The apparent density of the hand sheets varied between 437and 488 kg/m3، tear index between 6. 51 and 7. 11 mN. m2/g، and tensile index between 29. 2 and 30. 8 N. m/g. Statistically significant difference at 99% level was not observed between the strength values of the pulps. Wheat straw pulp produced applying 10% NaOH، 40 minutes pulping time at 95°C was used as the substitute pulp for Old Corrugated Container pulp. The characteristics of the pulp refined to 365 ml CSF was superior to OCC pulp which indicates that it can be used as reinforcing pulp for OCC.