فصلنامه جنگل و فرآورده های چوب
سال هفتادم شماره 4 (زمستان 1396)

This study was conducted to identify the arbuscular mycorrhizal fungi (AMF) in Manesht and Ghalarang protected area. For this purpose, 60 plots (400 square meters) were laid out using transect method. In each plot, four micro-plots (one square meter) were established and plant species were identified in these micro-plots. Soil samples were also taken from 0-20 cm depth. Spore extraction was done by wet sieving followed by centrifuge. Then AMF identification was carried out by morphological features of spores. Our result showed that 35 AMF species belonged to the seven families and 10 genera in the studied area. Glomus and Entrophospora with 48.73 and 0.1 percent were the most and least abundant genus, respectively in the studied area. Also, Glomus rubiforme with 88.33 percent and Funneliformis mosseae with 1.66 percent were the most and least frequent species, respectively. In the present study 44 plant species belonging to 32 genera and 17 families were identified. Gramineae, Fabaceae, and Compositae were more abundant families between the studied families.

In the current study, the capability of OLI-Landsat 8 data was investigated for estimating the tree above-ground woody biomass (AGWB) in Hyrcanian Fagus orientalis stands. The quality of images in term of geometric error and existing cloud was surveyed. Principle component analysis (PCA), tasseled cap transformation, rationing and fusion in both PCA and color transform approaches were employed on the images. 65 square sample plots (45×45 m2) were established in the study area and 45 sample plots were used for modeling with multiple linear regression (MLR) as stepwise. The model was validated with remaining 20 sample plots. Pearson correlation results showed most relationship between tree AGWB and corresponding spectral responds from PCA on spectral bands of 1 to 7. The same result was observed using MLR. So, this component was the most efficient variable in tree AGWB estimation in pure Fagus stands in the study area with adjusted-R2= 0.122, RMSE=14.3%, and bias=1.8%. The error of this model can be accepted on the large scale such as watersheds.

Estimation of forest productivity is one of the most important components in management of forest resources. One of the main tasks of forest managers is quantify and measure the differences of forest sites. In this study dominant height of trees, which is a reliable criterion for evaluating site productivity of mixed and uneven stands, was used. A random-systematic sampling method was used to locate 110 0.1 ha circular sample plots in beech dominated forests and the height and diameter of Fagus orientalis Lipsky trees with DBH ≥ 7.5 cm within each plot was recorded along with elevation, azimuth and slope of the ground. Also, at the center of each plot, soil samples from first layer (0-10 cm) were taken for analyzing several soil variables. Evaluation of site productivity using random forests model showed that Clay, altitude, potassium, carbon, silt and phosphorus are the most important variables in explaining the changes in dominant height of beech trees. On the other hand, radiation index, nitrogen, slope, pH and bulk density have the least effect on the dominant height of beech stands. Using random forests model more than 90% of variability in oriental beech dominant height could be justified using environmental variables.

Reforestation with native and exotic species has a significant effect on the diversity of plant species. This study was done to investigate the effect of Ailanthus stand (Ailanthus altissima) on herbaceous layer diversity in Talesh, Guilan province. Two sites viz. Ailanthus stand and natural forest were selected and 20 400 m2 sample plots were established in each stand as a systematic-random grid. Whittaker's nested plot sampling and minimal area method were used to determine the optimum plot size of the understory. Therefore, micro-plots of the size 16 m2 were established in the center of each plot and cover percentage of each species was estimated according to Braun-Blanquet approach. In general, 21 species of 15 families were recorded in the study area. Results indicated that the average of litter depth, the number of trees per hectare, the average of canopy cover percentage of trees and the average of herbaceous cover were higher in the natural forest. The species diversity and richness indices were higher in the natural forest than those in Ailanthus stand, while evenness index was higher in Ailanthus stand. Studying the abundance distribution models showed that both areas followed a lognormal distribution. Ailanthus species has reduced the diversity and richness indices. Therefore, in order to enhance the plant diversity in these areas, a combination of trees in plantation programs must be used instead of pure plant species.

After 28 years, the effects of Alnus subcordata (AS), Acer insigne (AI), Cupressus sempervirens (CS) plantations and also bare land on soil aggregate stability and particulate organic matter (POM) were studied in Darabkola forest located in Sari, Iran. In each stand, six soil profiles were sampled at depths of 0-10 and 10-20, resulting in 12 soil samples for each stand. The samples were transferred to laboratory for analysis. The soil properties were analyzed by using two-way analysis (ANOVA) procedure, treating forest stands and soil depths as factors with interaction. Results are indicating that the variability of soil physico-chemical and biological properties, i.e., bulk density, texture, moisture, pH, EC, lime, carbon (C), nitrogen (N), available nutrient, earthworms density/biomass, in different studied areas. According to our data, the plantation increased aggregate stability, POM-C and POM-N in both of depths. The upper and lower layers of soil had the highest amounts of soil aggregate stability (79.3 and 82.4 %), POM-C (4.24 and 3.56 g/kg) and POM-N (0.45 and 0.4 g/kg) under the AS forest stand. The least values of these characters were found under bare lands (50.54 and 52.76 %, 1.98 and 1.48 g/kg, 0.22 and 0.16 g/kg, respectively). Results showed that the planting of AS trees improved aggregate stability and POM and it is recommended for rehabilitation of degraded forest areas.

Recent global warming had brought harsh variations on climate variables all over the world. In order to investigate the past climate trend for predicting future climate trend, long term climate data is needed. Tree-ring data are good proxies of past climate which can be used to reconstruct the past climate. The purpose of this investigation is to develop the chronology of tree-ring width and its comparison with climate variables. Tree-ring width was measured by LINTAB table. Then, measured tree-ring width was cross dated by TSAP software. To remove age trend and preparation of final chronology, the ARSTAN software was used. 12 out of 22 tree time series were dropped out, because of insufficient matches with the other samples. The final chronology of the site was determined from 1657 to 2014, close to 358 years. However, EPS was more than 0.85 only for the period of 1910-2014. Correlation between annual tree-rings indices and monthly precipitation was not significant. While monthly mean temperatures of January, February and March had positive and significant correlations with tree-ring widths. It could be concluded that Juniperus growth is not limited by moisture conditions while higher temperatures were in favour of tree-ring growth. It seems that high elevation of habitat provides enough moisture for tree growth but on the other hand occurrence of very low temperature causing failure to provide suitable temperature condition for the start of cambium activities in the first months of growth season. Based on this finding, mean temperature of last century in this region could be reconstructed.

The forest is one of the most important natural ecosystems with a high potential for carbon absorption and gradual emission and also its equilibrium and the absorption of atmospheric carbon dioxide and carbon storage. Temporal variation of carbon sequestration in Hyrcanian forests is an important issue, so the aim of this study was to investigate the monthly changes of soil organic carbon (SOC) storage and determine its potential in the mixed beech-hornbeam stand. For this purpose, 20 sample points were randomly selected in one hectare of mixed beech-hornbeam stands and soil monthly sampling was done in 20 cm depth over a year from February of 2014 to February of 2015. SOC, moisture content, bulk density and volume proportion of coarse fragments were determined. Litter falls were measured using litter traps, soil and atmosphere temperature as effective factors on SOC pool were recorded in each sample points. Results showed significant monthly changes of litter production, soil moisture and temperature, atmosphere temperature and SOC storage over a year in the level of 95 percent. Also, results showed the highest and the lowest levels of SOC storage were in February (93.06 t.ha-1) and August (63.62 t.ha-1), respectively.

Even though vegetation are well recognized by their effects on hillslope hydrology and stability state, the hydrological effect of different types of forest covers are yet to be quantified. To address this gap, two adjacent hillslopes with different vegetation cover (a deciduous forest and a grass cover) were selected. The random-systematic method was used to determine nine sampling points on each hillslope. A PR2/6 profile probe was then used to monitor the soil water content at different depths of soil during the growing season of 2015. A soil water retention curve (SWRC) was made for each soil depth to facilitate the estimation of the equivalent matric suction of the monitored soil water content. Based on the results, the value of soil matric suction tends to be significantly higher in deciduous hillslope than the grassed hillslope (P

In order to better management of existing forest roads maintenance in the country in addition to economic indicators, it is essential to contribute other effective factors such as improvements in road pavement, road effects on economic conditions of forestry plans, cost of forest operation, users and natural conditions. Considering the above-mentioned factors as well as their impact on the prioritization of options requires multi-criteria decision-making, which has been investigated in this study. For this purpose, factors affecting the maintenance were first determined by expert's opinion. Then 50 km of forest road under the management of Mazandaran wood and paper company was selected. Due to the wide range of quantitative and qualitative factors and a large number of alternatives, Analytical Hierarchical Process (AHP) was developed to prioritize the repair and maintenance of forest roads. According to the results, the mentioned method is able to prioritize the forest network in term of the maintenance operation. The result of the current study also showed that the decision makers are able to prioritize the forest roads from different spatial and temporal point of view using the generated model according to expert knowledge and effectiveness of these factors.

Point pattern analysis based on the spatial distribution of a mark, e.g., diameter; could be implemented using Mark Correlation Function (MCF). The purpose of this study was to quantify the spatial interaction and competition in the intact beech stands of Hycanian forests of Iran using MCF. To this end, nine 1-ha sample plots were established at three developmental stages of initial, optimal and decay in three intact natural, unmanaged and uneven-aged beech (Fagus orientalis Lipsky) stands in the north of Iran. Diameter at breast height (DBH) of all trees greater than 7.5 cm along with their coordinates were recorded and fully mapped in the plots. Analysis of intra-specific competition of beech trees using MCF showed that DBH in the initial stage had a negative correlation indicating high spatial competition at all distances, while it was independent or positive in optimal and decay stages, except at distances up to 12 meter. Consequently, there was no intra-specific competition in each of these two stages. The results demonstrates the utility of second – order analysis of marked point processes for characterizing the competition in the beech stands and planning silvicultural interventions, e.g., thinning, based on the competition intensity of trees.

Fortune's Empress Tree (Paulownia fortunei) is one of important exotic and fast growing tree species in Iran, that salinity stress can affect its seed germination and seedling growth. In this study, for determining the response of this species under salinity stress, effects of 5 salinity treatments in different NaCl concentrations (0, 50, 100, 150 and 200 mM) on seed germination, survival and growth characteristics of Paulownia fortunei seedlings were investigated under laboratory and greenhouse conditions. In laboratory conditions, seed germination was conducted with 4 replicates and 5 salinity treatments based on a completely randomized design. In the greenhouse conditions, growth and survival of P. fortunei container seedlings were conducted with 6 replicates and 5 salinity treatments, based on a completely randomized design for one growing season. The results showed that in the absence of salinity, germination percentage (GP) and germination speed (GS) of P. fortunei seeds reached to 89% and number of 19 seeds per day, respectively. GP did not significantly decrease until 100 mM NaCl, but GS began to decrease significantly from 50 mM and reached to its lowest value at 200 mM NaCl concentration. Survival of seedlings showed a significant difference with control (non-saline) at 150 and 200 mM NaCl concentrations with 50% and 83.3% reduction, respectively. Moreover, a significant decrease began in vegetative characteristics of seedlings from 50 mM concentration, but there was no significant difference at concentrations of 50 to 150 mM NaCl.

Microbial biomass carbon (MBC) and microbial quotient has been utilized as sensitive indicators to changes in ecosystems that are considered in soil quality studies. This study aimed to investigate the effects of selection system on the seasonal and monthly variations of MBC and microbial quotient in mixed beech stand which was performed in 2013. For this purpose, two stands including control and forest managed by selection system in Dr. Bahramnia educational and research forest in Gorgan province, Iran. We selected 6 (3×3 meters) sample plots within each stand (3 sample plots under closed canopy and 3 sample plots under the canopy gap with an area about 400 square meters. Three soil samples were taken from 0-10 cm depth at three random points within sample plots. For each soil sample, MBC, organic carbon, soil temperature and moisture were measured monthly in each sample plots within one year. Results showed that there were many fluctuations in MBC and microbial quotient in different seasons and months through the year despite the inconsiderable variation of soil organic carbon (3.01-4.55 percent in control stand and 3.04-4.51 percent in the managed stand). The highest and least amount of these two parameters were in autumn and winter, respectively. MBC mean in control stands (933.56± 22.66 mg.kg-1) were statistically similar with managed stand (940.44± 22.92 mg.kg-1) through the year. The results indicate the potential of managed stand in maintaining the balance after implementing the selection system method and the success of the implementation of this method based on these biological indicators.

In this research, the cotton linter was used as raw material for high yield cellulose acetate production. The degree of substitution (DS) was almost 2-2.5 in acetylation stage. The desired dissolving pulp with purity higher than 98% and viscosity close to 712 ml/g was obtained through the soda pulping at 160 °C for 3 h. TCF bleaching was performed until 85% of ISO brightness was obtained. One of the most important factors in using high temperature and time for pulping process was the lignin existence in the dense seed bark of cotton which had most impurity in the linter. The final dissolved pulp showed the best results in yield and DS by using the acetylation process at 85 ˚C, 8% of iodine (based on OD pulp) as catalyst, and a weight ratio of acetic anhydride to the pulp (10:1) under stirring for 20 h. The results illustrated that the yield and DS of produced cellulose acetate were 64.44% and 2.3 respectively. The higher yield was achieved in acetylation stage compared to the previous studies due to higher purity of dissolving pulp and more suitable viscosity. The more concentration of iodine up to 12% in acetylation process led to increase the DS to 2.7 while the used of 8% of iodine showed the 5% decreasing in yield.

The current study was carried out to show the possibilities of wheat straw as most important and available agricultural residue for production of the cellulose nanofibers by carboxylation pretreatment. Soda-AQ and ECF bleaching sequences as DEPD were respectively selected as pulping and bleaching processes. TEMPO mediated oxidation as NaClO/NaBr/TEMPO system was applied to introduce carboxyl content on the fiber surface at varying level of 2, 6 and 10 mmol (based on O.D bleached pulp) of oxidant. Two different and applicable methods such as conductometric titration (CT) and fourier transform infrared spectroscopy (FTIR) were used to measure the functional group of carboxyl content. The results showed that the selective oxidation of hydroxyl group at C6 to carboxyl was occurred with increasing the oxidant consumption. The oxidized cellulosic fiber then passed through the high pressure homogenizer (HPH) for four times to produce individualized cellulose nanofibers (CNF). The results showed 58% decrease in viscosity, degree of polymerization (DP) and molecular weight (MW) and 10% decrease in crystallinity of fibers after oxidation and passing through the HPH. In the following, isolated CNF at minimum (two) percent of oxidant (sodium hypochlorite) was used for production of nanopaper via dispersion casting (DC) process. The field emission scanning electron microscope (FESEM) images illustrated that the nanofibers had diameter less than 30 nm. and its nanofiber diameter was measured and it was less than 30 nm by Field Emission Scanning Electron Microscope (FESEM).

In recent years, utilization of non-wood lignocellulose resources has been great concern for production of different cellulose products. Therefore, the properties of pulp from barely straw via monoethanolamine (MEA) process were investigated in this study. Pure monoethanolamine was used in different proportions with water and anthraquinone. Variables including proportion of monoethanolamine to water at five levels (100, 75, 50, 37.5, and 25 %) and anthraquinon at two levels (0 and 0.1%) were selected. Soda pulping process was used as a reference cooking sample. According to obtained results, the produced pulp by MEA/water ratio of 25/75 had the highest yield (63.2%) and the lowest kappa number (18.9) was observed in the pulp produced from MEA/water ratio of 75/25. Burst, tensile and tear indices of the pulp produced from monoethanolamone method were obtained 64.17N.m/g, 6.04 mN.m2/g and 3.17 kpa.m2/g, respectively. In general, pulping process via combined method of monoethanolamine/water makes it possible to obtain a chemical pulp with suitable kappa number (less than 20), efficient yield and proper bleaching ability, using a little amount of monoethanolamine in combination with water.

In this study, in order to improve the medium density fiberboard properties made of mixture of virgin and recycled fibers, urea formaldehyde resin was modified by adding 3 and 5% isocyanate. Experimental boards were made by adding recycled fibers to virgin fibers (0, 20%, 40%, 60%,80% and 100%) and using 10% urea formaldehyde as binder. Mechanical (modulus of rupture and internal bond) and physical properties (water absorption and thickness swelling after 2 and 24 hours submerging) were measured based on DIN68761 standard. The results showed that by increasing recycled fibers, the modulud of rupture and internal bond were reduced but inclination was slow up to 40% recycled fibers while by addition the recycled fibers more than 40%, the inclination became faster. On the other hand, the modulus of rupture and internal bond of fiberboards made of mixture of 40% recycled fibers and 60% virgin fibers reduced 7% and 21% respectively. This fault was fixed by modifying urea formaldehyde resin by adding 5% isocyanate adhesive. The results demonstrated that the modulus of rupture and internal bond of fiberboards made in this condition increased 20% and 102% respectively. Furthermore, adding recycled fibers to virgin fibers reduced water absorption and thickness swelling. This improvement can be attributed to the modifying of urea formaldehyde resin with isocyanate. In addition, the fiberboards made of 100% recycled fibers and modified urea formaldehyde resin by adding 5% isocyanate showed the lowest water absorption (29.86%) and also thickness swelling (3.38%).

Increasing the application of tissue papers and its competitive market, particularly in respect to the water absorbency and wet strength, is important and utilization of necessary chemicals especially bio-based ones, for required specification is extensive. Therefore, the aim of this is to focuses on the bio-based chemical and its efficiency. Effects of the chitosan biopolymer compared to the common synthetic polyamide epichlorohydrin (PAE)on the wet and dry strengths, whiteness, brightness and water absorbency of handsheets prepared from deinked pulp of mixed office waste paper were carried out at 0.5, 0.75 and 1% addition levels of the wet strengths agents. SEM images proved the sedimentation of additives and higher advent of chitosan fibers than PAE. Higher dry tensile, burst and wet tensile strengths, lower rate and content of water absorption of treatment with chitosan were determined mainly caused due to creation of cross links among the paper ingredients during the drying. Due to the high similarity between the cellulose and chitosan and also plenty of amine and hydroxyl functional groups of the chitosan, the bonding increased while water uptake sites decreased. Extensive bonding resulted in lower flexibility and higher bending stiffness, which was higher in PAE than chitosan treatments at 0.5%. In spite of declining trend, variations in whiteness (111%) and brightness (86%) of chitosan reinforced handsheets were insignificant. Generally, 0.5% of the chitosan compared to 1% of PAE, provided higher strengths values and minimum reduction in water absorption (~10%) and optical properties while higher flexibility donated to the paper. Also an improvement in the wet strengths of the fibrous network could be resulted in better machine runnability.

The aim of the present study was to produce hybrid low density panels using wood fiber as surface layers and a mixture of wood particles and polystyrene granules as core layer. The effects of the most important factors on panel properties were investigated. Hybrid lightweight panels were produced with a density of 520 kg/m3 using polystyrene granules as filler in the core layer. The type of polystyrene granules (expandable and pre-expanded shapes) and granules diameter (fine, medium and large) are the most important factors which can influence the panel properties were also investigated in this study. The results showed that the granule type had significant effect on the physical and mechanical properties of panels. The modulus of elasticity and face screw withdrawal resistance were increased in case of pre-expanded granules, while the internal bond values improved in the case of expandable granules. Mechanical properties of lightweight hybrid panels were significantly enhanced by increasing the diameter of both granules forms (pre-expanded and expandable). Thickness swelling was lower in the case of fine granules. But the granules diameter had no significant influence on the water absorption values. It can be concluded that the expandable filler with larger diameter can be used as filler for the production of lightweight panels.