فصلنامه جنگل و فرآورده های چوب
سال شصت و پنجم شماره 4 (زمستان 1391)

In this study، derivatization followed by reductive cleavage (DFRC) method was used to investigate the structures of milled wood lignin and dioxane lignin of Spruce (Cupressus sempervirens). After performing DFRC reactions، the structures of constituents resulted from these two kinds of lignins were investigated by using Spectroscopic methods such as 13CNMR، GC-mass and gel permeation chromatography (GPC). The results obtained from chromatography and spectroscopy studies were compared. These comparative results show that the dominant structural components of these two kinds of lignin are obtained from the cleavage of? -O-4 bonds. The main components obtained from dioxane lignin and milled wood lignin are 4-hydroxy-3-methoxy-1-phenyl propene and 4-hydroxy-3-methoxy-1-phenyl- propenal (guaiacyl structures)، respectively.

Discoloration of wood due to biotic and abiotic factors or combination of both deteriorates the quality of wood، increases production costs and also decreases the quality of end-products. In this study، anatomical variations and topochemical distribution of lignin and extractives before and after drying and aging were investigated using the UMSP method. Chemical analysis was carried out using HPLC method. Results showed that increasing drying temperature up to 180 °C and increasing aging duration up to 6 months، increased extractives amount in vessel lumen and parenchyma cells and as well as lignin concentration in cell wall layers. A direct relationship between intensity of visual discoloration and the amount of UV absorption by extractives could be observed. It means that the higher the visual discoloration، the higher the absorption at 280 nm wavelength. HPLC analysis revealed that with increasing drying temperature and aging duration، higher and clearer discolorations in beach wood texture could be observed. Acetone and methanol extracts of discolored wood showed the presence of different low molecular compounds such as catechin and 2، 6 dimethoxy benzoquinon، which are transformed to high condensation compounds during kiln-drying and aging.

Impacts of skidding operations on forest soils can be divided into three major categories: soil profile disturbance، soil compaction and soil puddling and rutting. The aim of the study was to assess the effect of number of machine passes and soil moisture content on skid trail rutting، and to quantify these effects. The study was designed as a complete factorial experiment in the Kheyrud Forest following Timberjack cable skidder operations. The effect of 25، 35 and 45% soil moisture content and different levels of compaction were assessed by varying number of skidding cycles: 1، 5، 10، 15، 20، 30 passes. The results showed that the rut depths increased with increasing number of machine passes، but most of the rutting occurred after the initial few passes. Rut depth at 45% soil moisture was higher than rut depths at 35 and 25% of moisture content. The average rut depths in soil with 25، 35 and 45 moisture were 43، 101 and 172 mm، respectively. Rut depths significantly increased with soil moisture and number of machine passes. Skidding operations should be planned when soil conditions are dry to minimize rutting، but if skidding must be done under wet conditions، the operations should be stopped when machine traffic creates deep ruts.

Cerasus mahaleb (L.) Mill is one of the most important tree species in Zagros forest and has great importance but it is classified as threatened flora species. In this study the effect of different chilling treatments (regarding growth of Cerasus mahaleb (L.) Mill in high elevations) was investigated. Studied treatments included 4، 8، 12، 16، 18، 20، 22 weeks cold stratification in two cases: with and without coat. The results showed that there was significant difference (P<0. 01) among the studied treatments and 22 weeks cold stratification had the highest average germination (61. 5 percent). The lowest germination rate was occurred in 8 weeks cold stratification; in control and 4 weeks cold stratification no germination was observed. The most amount of germination vigor in 22 weeks and the lowest amount in 4 weeks cold stratification was occurred.

The dynamic of shrinkage in beech (Fagus sylvatica) and spruce (Picea abies) was non-destructively determined during drying using X-ray spectroscopy. Furthermore، electron microscopy (ESEM) studies were carried out and the pattern of moisture gradient evolution was determined in order to precisely characterize the dynamic of shrinkage. The results showed that the dynamic of shrinkage is different for beech and spruce. The shrinkage of beech wood occurred during the bulk (capillary) flow of free water when the surface moisture reduced below fiber saturation point. In contrast، the shrinkage of spruce wood only occurred at the domain of bound water diffusion. The uneven pattern of shrinkage in beech wood reveals that the shrinkage of beech is more anisotropic than that of spruce. In the case of both woods، especially in beech، in spite of moisture reduction at the domain of bound water diffusion close to the final moisture، shrinkage did not occurred. Since the beech wood cells didn’t suffer from collapse، it can be concluded that the considerable shrinkage of beech wood at the domain of free water can not be due to the cell collapse at a result of capillary tension.

The purpose of this study was to investigation the effect of storage time of cotton stalks on properties of produced particleboard. Therefore experimental boards were produced from cotton stalk in form of fresh، stored for 4 and 8 mounths in indoor and outdoor conditions. Also two combination of cotton stalk and poplar particles (100% cotton stalk and 60% cotton stalk & 40% poplar) is used. 30 boards were produced and physical & mechanical properties of their tested and analized. The results indicated that the modulus of rupture (MOR) and modulus of elasticity (MOE) of boards decreased significantly، with increasing of storage time of cotton stalk. Although، increasing of poplar particles made up reduction MOR and MOE of boards that made from cotton stalk with 4 and 8 mounth of storage time. The results indicated that with increasing of the storage time، the internal bonding of boards decreased to lower than EN standard level and use of cotton stalk and poplar particles combination were effective and improved IB of boards. Also، the thickness swelling of boards increased with increasing of storage time of cotton stalk. The results of this investigation showed that all of physical and mechanical properties of made particleboard reduced with increasing of storage time of cotton stalk. But the IB of boards decreased to lower than EN standard level.

Estimation of forest structural parameters is one of major basic information in sustainable management and planning in forest stands. In this study، relationship between ASTER satellite data and three forest structure factors including stand volume، basal area and number of trees per hectare were investigated in Darabkola forest، northern Iran. A multivariate linear regression approach was used to analyze and evaluate relationship between mentioned characteristics and ASTER satellite data. Relevant preprocessing and methods were conducted on spectral data. After gathering terrestrial information، stand volume، basal area and number per hectare were calculated for sample plots. Using some plots، performance of the best models examined by relevant evaluation criterions. The results showed that a combination of MSAVI2، NDVI and Green bands could predict stand volume characteristics better with R2adj=59. 2; and RMSE=116. 5 m3/h-1 in comparison with other indices and band combinations. For basal area، the best results were obtained using combination of MSAVI2، NDVI and simple ratio of SWIR12 with R2adj=73. 5 and RMSE=5. 14 m2/h-1. In addition، combination of MSAVI2، SWIR1 and SWIR2، was a better predictor for number per hectare rather than the other combinations by R2adj equal to 0. 85 and RMSE about 50. 95 number per hectare. Generally، this research showed that using linear regression approach by the ASTER data presents only general status of forest structure attributes in the study area and having more precise estimation of these attribute needs investigating other approaches such as nonlinear or nonparametric and learning machines approaches.

Investigation of spatial pattern in vegetative populations is an important part of forest ecology. Great areas in central deserts of Iran are covered with saxaul (Haloxylon spp.). Therefore، any research concerning this species has a great importance. Eight distance-based and five quadrate-based methods، including: nearest neighbor، Holgate، Pielou، Eberhardt، Hopkins، Johnson & Zimmer، C، Hines، Green، Morisita، Standardized Morisita، Index of Dispersion and Lioyd were used to determine spatial pattern of this species. Two districts each 30 hectares area which were representative of saxaul populations were selected. Coordinates for all shrubs were determined using distance and azimuth and finally a point map was created in ArcGIS. Then، 35 sample plots (each 0. 1 ha area) overlaid randomly on point map. Centers of these plots were used as random points for distance-based methods. In district I، Johnson and Zimmer، standardized Morisita and Index of dispersion indices showed clumped pattern for saxaul while other indices showed random pattern. In district II، all indices showed clumped pattern except for Johnson and Zimmer index. Overall spatial pattern of saxaul appraised random in flat areas and clumped in mountain-sides. Also T-square index (C) and Holgate were the best distance-based indices to identify pattern. Morisita index was the best one between quadrate-based indices.

The effect of recycling on physical properties of lignin rich chemimechanical pulp (CMP) and neutral sulfite semi-chemical (NSSC) pulp was evaluated. The pulps were exposed to recycling treatment for three times without any further refining and the fines were conserved. The results indicated that some physical properties like tensile strength، tensile energy adsorption (TEA)، burst strength، apparent density and compression strength were decreased by recycling due to hornification followed by loss in fiber flexibility and swelling which give rise to interfiber bonding loss. However the opacity and light scattering coefficient presented gain through recycling. Besides، the bending stiffness، air permeability and roughness increased due to recycling. The observations generally indicated that the CMP and NSSC pulps behavior under recycling is much similar to that of chemical pulp rather than mechanical pulps.

Diversity in flower and pollen morphological traits was assessed in eight Iranian Tilia spp. populations. Flower samples were taken from 6 to 15 individuals in each population، with at least 100 m distance from each other. The results revealed that among the populations، the width of bract and peduncle had significant differences (p<0. 005)، but differences in length of bracts and pedicel were not significant. The lower altitude populations (<1200 m a. s. l) had longer pedicel than those of higher altitude ones (>1500 m a. s. l). Two style types including pubescence and glabrous style were recognized for the genus Tilia in these forest habitats. Pollen grain was medium size and oblate. Pollen of Hyrcanian،s Tilia has three very short oval furrows (except، some trees with 4 furrows in Asalem populations). There was a meaningful difference in the pollen sculpture of mountain populations (Bandbon and Dalir) compared to other populations. Also، only pubescence style and sparse stellate trichome were found on bracts of Bandbon population. In conclusion، polar and equatorial axes showed maximum variations and based on investigated traits، Bandbon population is different from other populations.