Journal of Forest and Wood Products
Year:2011 | Volume:64 | Issue:2|Papers Count:11

The main objective of this study was identifying Box trees (Buxus hyrcana Pojark.) communities and survey of their relationships to some physiographic attributes and plant biodiversity indices in Khybus Protected Area which is one of the best and most virgin Habitats of Box trees in Hyrcanian forest. The field data were obtained in 65 sample releves in a systematic- selective design (200´400 meter) by consideration Braun- Blanquet indicator stands concept. Physiographic attributes and plant biodiversity indices were also recorded in each releve. Vegetation data were analyzed using TWINSPAN. The data were classified into six plant communities. The results of ANOVA showed that these plant communities reflected underlying differences in altitude, northness, slope, richness and pielou evenness. Then Plant communities were ordinated using DCA from basis of diagnostic plant species percentage cover and the correspondence scores of the two first axes, which have explained the 25.5% of total variation changes in floristic data. The correlation between plant communities with environmental factors and plant biodiversity indices were determined by Pearson correlation coefficient. The DCA ordination showed that each plant community has its own range and are separately distributed. Also the first DCA axis was associated with the altitude, northness, richness, Shannon- wiener diversity and Pielou evenness among the communities, while the second one showed significant correlation with the slope gradient among the communities.

Buffered sulfite pulping of com stalks was investigated. Four variables including sodium hydroxide charge at 12, 14, and 16%, sodium carbonate charge at 4 and 8%, pulping temperature at 145 and 165oC and pulping time of 15 and 30 minutes were evaluated. Results showed that increasing any of the four variables reduced both total yield and kappa number where the influence of pulping temperature was more pronounced. The highest total yield and accepted yield were measured to be 59.7% and 51.4%, respectively, applying pulping condition of 12% Na2S03, 4% Na2C03, 145oC and 15 minutes. The kappa number was 55.4. The lowest total yield of 34.1 % and kappa number of 16 were achieved using 16% Na2S03, 8% Na2C03, 165oC and 30 minutes. Two pulps with the highest total yield and one with the lowest kappa number were selected for further evaluation. The tensile index of selected pulps varied between 52.5 and 66.6 Nmig, and the relevant value for low yield pulp was 62.9 N.m/g. Tear index varied between 5.2 and 6.7 mN.m2/g and the respective value for low yield pulp was 7.3 mN.m2/g. The brightness values of the high yield pulps were measured to be 26 and 27% ISO, respectively and 40% for the low yield pulp. The results of this study revealed that brown pulp can be produced using com stalks.

Measurements of gross rainfall (GR), throughfall (TF), and stemflow (SF) were conducted during the summer 2009 beneath a natural pure stand of oak (Quercus castaneifolia C.A.M) forest canopy located near the southern border of Kheyrud Forest Station of Tehran University. Measurements were made inside a plot with an area of 0.12 ha. GR was collected by means of three manual collectors placed in a neighboring open area away from the study plot. Thirty five TF manual collectors were randomly positioned underneath the tree canopies. SF was collected from nine oak trees with different diameters by the spiral-type SF collection collars installed at diameter at breast height. All the measurements were performed on a rainfall event basis using a graduated cylinder. Interception loss (1) was calculated indirectly as the differ rence between GR and the sum of TF and SF. During the study period, 10 events were recorded. The cumulative GR, TF, SF, and I depths were 257 mm, 192 mm, 0.7 mm, and 64.3 mm, respectively. At the event scale average ratios of TF:GR, SF: GR, and I:GR were 72.2%, 0.2%, and 27.6%, respectively. A weak correlation was observed between SF:GR and GR (r2 = 0.43) while a fairly strong positive correlation was observed between I:GR and GR (r2 = 0.65). Interception loss contributes a remarkable amount of incident rainfall in the studied oak forest and its measurement is an essential element in assessing water balance on a catchment scale.

In this study three sampling methods named Random-pairs method, Joint-point method and Line- intercept were used for estimating quantative characteristics of Zagros Oak (Quercus brantiii forests with regard to accuracy in research and educational forest of Razi University (Kermanshah province). Random-pairs method and Joint-point method were used for estimating trees per hectare, and for estimating percentage of canopy cover Line-intercept method with Random-pairs method and Joint-point method were examined. For each method 50 samples were selected using systematic-random design and number of trees and higher and lower diameter of crown were measured to obtain trees per hectare and percentage of canopy cover in each sample. The results showed that none of methods can provide an acceptable estimate of density and percentage of canopy cover based on ± 10% accepted accuracy; the Random-pairs method has more accuracy level for crown coverage for this kind of forests.

In this research, manufacturing of fiberboard (HDF) and treated fiberboard from creosote treated solid wood was studied. Recycled fibers were generated by pretreatment of creosote treated wood chips with sodium hydroxide and fiberized under normal environmental condition. These fibers were blended with 0, 15,30,45 and 100 percent by weight of virgin fiber; generated from untreated wood under high vapor pressure condition. Then fiber mixtures were treated with creosote (free of high molecular weight PAH components) and creosote free runoff obtained from both fiber generation processes, to form wet fiber mats. All fiber mats were completely dried and hot pressed to produce 3mm (d: 1 g/cm3) nominal thickness hardboards. Next, physical and mechanical properties of creosote treated and untreated fiberboards were evaluated. The results showed that creosote treated fiberboards had better physical properties with minor water absorption <17%) and thickness swelling <11 %) after 24 hours submersion in water while FTIR test indicated that creosote components were not absorbed chemically by wood ingredients. On the other hand, creosote free fiberboards presented better mechanical properties so that adding only 45% of virgin fibers resulted in similar properties to those of 100% virgin fiber samples.

Mycorrhizal symbiosis facilitates establishment of plant by increasing water and soil elements absorption such as N, P and K and rhizosphere distribution. It also increases soil biodiversity and microbial population as well as plant resistance against pathogens and stress. In this study thirty individuals of natural Pyrus glabra in Bazoft were selected. To find out the interactions between arbuscular mycorrhizal and soil elements, root samples were obtained during spring and autumn. Arbuscular mycorrhizal fungi spores were isolated by wet sieve and centrifugation by means of sucrose. Then roots were stained and colonization percentage was measured. Seven species of Glomus and 2 species of Acaulospora were characterized. Significant difference was found between Arbuscular mycorrhizal colonization percentage and spore frequency in spring and autumn. Significant correlation was observed between colonization percentage and total nitrogen in spring.

Influence of the acetylation and the compatibilizer MAPP on the long term swelling rate of polypropylene/ acetylated wood fiber composites (WPCs) was the main concern of the current research. Wood fibers were reacted with acetic anhydride without a catalyst to achieve weight percent gains (WPGs) of 4.5, 7.5 and 17.68%. The acetylated fibers were mixed with MAPP (0 and 2%) as well as the polypropylene as the matrix polymer and molded at 180oC in a hot press. Test specimens were cut from the samples and soaked in water for 1512 hours at room temperature to determine the thickness swelling as well as the rate of the swelling in the WPCs. Results revealed that the thickness swelling of the acetylated composites was significantly reduced in comparison with the non-acetylated one. Application of the MAPP decreased the swelling as well. However, there were no significant differences between the acetylated WPCs containing the compatibilizer with the composites without MAPP. The Shi and Gardner (2006) model was adopted to evaluate swelling in the acetylated composites.

In this research, the effect of Dolomite mineral material on physical properties and fire resistance of composites produced from beech wood flour and polyethylene manufactured through hot pressing method was examined. In order to evaluate the effect of coupling agent on bonding between cellulosic fibers and the matrix, two levels (1 %, 3%) of maleic anhydride grafted polyethylene were used. Standard experimental samples were prepared and properties such as water absorption, moisture diffusion coefficient, thickness swelling and fire resistance, were measured. The results showed that, when the mineral material dosage was increased, water absorption, thickness swelling, and moisture diffusion coefficient decreased whereas fire resistance increased,. Generally, addition of MAPE to the compound improved physical properties as well as fire resistance.