فصلنامه جنگل و فرآورده های چوب
سال هفتاد و دوم شماره 3 (پاییز 1398)

The aim of this study was to evaluate the effects of density, situation of seedlings in intertidal zone, species and their interaction effects on growth characteristics and survival of seedling in tidal zone. 6-month seedlings of Avicennia marina (Forssk.) Vierh. and Rhizophora mucronata (Lam). were transferred to Tasbar firth in Hormozgan province (split split plot in randomized complete block design). Seedlings were planted with 1×1, 2×2 and 3×3 m densities and 10, 20 and 30 m distance planting in tidal zone. Vegetative characteristics and survival rate were investigated every 2 months for a year and analyzed using general linear model at the level of 95% confidence. Result showed, in 20 m planting distance, collar diameter, height, canopy diameter and survival rate of seedlings were highest (4.97 mm, 15.51 cm, 4.78 cm and 43.93% respectively). Also, collar diameter, survival percentage, height, canopy diameter and stem height to stem diameter of grey mangrove were, respectively, 3 mm, 37.81%, 11.01, 4.53 and 24.04 cm, higher than those of red mangrove (p<0.05). According to this study, it is recommended to cultivate grey mangrove in intertidal zone to increase the chances of afforestation success in Hormozgan province.

Over time, environmental and human factors have caused positive and negative changes in the quantity and quality of vegetation, and these changes will continue. Vegetation greenness trend may be either increasing (Greening) or decreasing (Browning). Understanding the factors creating these changes and detection of trends in the past and future, would be useful for managers and decision makers. This study investigates the long-term changes in Kurdistan vegetation greenness by using the 16-day composite MODIS NDVI time series for 2000–2017, and 414 images with 250-m pixel size. The coordinate system of MODIS data was converted from the sinusoidal to the geographic map projection and a time series of data was created. After seasonality removal in the time series data, the long-term trend analyses were performed using parametric ordinary least squares (OLS) regression and non-parametric Theil-Sen and Mann-Kendall methods at pixel by pixel basis. Both OLS and Theil-Sen represented the similar result and indicated a slight increase in NDVI i.e., the poor greenness during the study period. According to the Mann-Kendall trend analysis, about 97 % of the province experienced a slight increasing and 2.46 % showed decreasing trend. However, based on the Kendall significance test, only 12 % of the province had a significant increasing or decreasing trend at 1 % confidence level and the rest of the area showed a slight and negligible increasing trend.

Cupressus sempervirens var. horizontalis, an ornamental tree, is suitable for wind break, soil conservation, wood production and forms a large part of seedling production in nurseries of Iran. Considering the expected limitations of water resources, the target of this investigation was to study the effect of rhizobacteria Pseudomonas fluorescens on the growth and survival of C. sempervirens seedlings under water deficit. The experiment was carried out with four irrigation periods and two rhizobacteria levels (inoculation and non-inoculation) in a randomized complete block design with three replications. To determine the amount of irrigation water, the field capacity was calculated and the water deficit was given to the plant to the desired moisture content after weighing of the pots. The seedlings in severe water deficit (irrigation period of 12 days) had a survival rate of 95% and higher. Shoot growth and diameter growth were, respectively, reduced by 52.6% and 49.6% in 12-day irrigation compared to 3-day irrigation, but inoculation increased by 14.7% and 14.3% in them, respectively. Regardless of water deficit, root biomass in inoculated seedlings increased by 23.2% compared to the non-inoculated seedlings. Shoot biomass, total biomass and seedling quality index in the period of 9 and 12 days and root volume during the 12-day period decreased, but by inoculation, these variables increased 13.9, 16.8, 20.1 and 25.3, respectively. Overall, although water deficit decreased growth characteristics of C. sempervirens seedlings but it can be concluded that root inoculation with P. fluorescens can be used as a biologic fertilizer to suit the growth and morphological quality of seedlings, even under severe water deficit conditions. This strategy can be useful for producing proper seedlings of C. sempervirens in nurseries facing water constraints.

Habitat trees provide diverse microhabitat for various organisms in forest ecosystems. Old-growth phase is one of the determined developmental phases of beech stand dynamics in the north of Iran. This research was carried out in Shafaroud forest in the west of Guilan province to assess the habitat and dead trees in this developmental phase, qualitatively and quantitatively. For this purpose, three one-hectare areas were selected and in each area, quantitative characteristics of habitat and dead trees including abundance, tree diameter, and height were recorded. Results revealed that from the different types of habitat trees, crack trees were the most frequent in the study area (31.7%) while other frequent types were cavities, burr and fork-spilled tress (29.3, 24.4 and 14.7%, respectively). The most frequent tree-related microhabitats were observed on the beech trees. The mean of dead volume in this phase was 37.1 m3 and Shanon and Simpson diversity indices were calculated as 1.9 and 1.7, respectively. Meanwhile, the Margalef and Pielou evenness indices were 0.8 and 0.9, respectively. The findings demonstrate that very thick beech trees (with the diameter of 70 cm and more) show the highest number of microhabitats as well as the most diversity. The presence of tree-related habitat trees in different forms should be considered in the planning and implementation of silviculture.

For several years, soil quality assessment has been focused solely on determining the soil physical and chemical properties, but recently, the measurement of soil biology has also been considered. Present study was conducted in the east of Guilan province on the poplar lands of the Safrabasteh Poplar Research Station. The plan of soil samplings were conducted in a random-systematic grid with 4 plantation stands including Populus euramericana 45.51, Populus euramericana Triplo, Populus deltoides 69.55 and Populus deltoides 77.51, which are about 25 years old as well asnatural forest, Populus caspica as control area. Soil sampling was taken at a depth of 0-20 cm, then some microbial indices and soil chemical properties were analyzed. The results revealed biological and chemical indices have significant differences among the treatments and the majority of these variables in Populus deltoides 77.51are higher compared to the other treatments. According to the results, it can be stated that due to the importance and economic value of poplar cultivation and the interactions between them and soil, in choosing the best clones, both growth and economic benefits and their impact on the environment and especially the soil must be taken into account. It is declared that the variations of soil properties and the diversity of trees indices are proportional to forest site productivity. Different poplar clones and species have different ability to return nutrients to soil and affect soil. Based on the results, Populus deltoides 77/51 compared to the other treatments showed appropriate conditions to improve microbial respiration activities.

The main pre-request of the forest management and planning program is the availability of quantitative and qualitative data from forest structure. Therefore, the forest inventory plays a vital role in the estimation of the current status and future planning. In this study, spatial pattern of trees in Gorazbon section of Kheyroud forest in northern Iran was simulated to compare the random systematic sampling and complete random systematic sampling method based on the full calipering method. By using the Arc GIS software, the spatial pattern of forest trees was simulated. Buffer function was used to calculate the random systematic sampling and complete random systematic sampling method based on the full calipering method. In order to compare random systematic sampling with full calipering single-sample, a t-test was used. The results showed that there was no significant difference between random systematic sampling and full calipering method to estimate the average diameter of Alnus, Fagus orientalis, and Tilia begonifolia. However, there was a significant difference between two methods in the estimation of average diameter of Carpinus orientalis and Quercus persica. The results of T-test revealed that there is no significant difference between Alnus and Tilia begonifolia but significant difference was observed between the trees of the Fagus orientalis, Carpinus orientalis, and Quercus persica. In addition, paired t-test was used to compare the random systematic sampling and complete random systematic sampling method. Results showed that there is no significant difference between random systematic sampling and complete random systematic sampling method.

There are several methods for improving wood properties; one of them is the impregnation of wood with a variety of monomers, and converting them into a polymer inside the wood. This leads to the production of a new product called wood polymer. One of the monomers used for wood impregnation is amino resins such as urea formaldehyde as well as melamine formaldehyde (MF). In this research, MF resin was used for the impregnation of poplar wood in order to improve the dimensional stability and mechanical properties. MF was synthesized experimentally with a molar ratio of 1.5:1 (F: M) which had lower free F and viscosity than industrial resin. The samples were impregnated using vacuum/pressure method with different concentrations (7, 15, 27 and 35%) of experimental MF as well as industrial ones with concentration of 27%. The results showed that the percentage of weight gain (WPG) of samples significantly increased by increasing the amount of resin concentration. The volumetric swelling and the water absorption of samples significantly decreased even after long-term immersion in water according to the WPG values. The mechanical resistances including modulus of rupture, modulus of elasticity, hardness and pressure parallel to the grain increased by an increase in WPG values compared to the that of controls. However, the impact bending in the treated samples were lower than the controls, this seems to be due to the high toughness of the melamine crystals formed inside the wood. The experimental MF resin produced in this study with low formaldehyde content showed high potential for improving the physico-mechanical properties of poplar wood.

The glued laminated beam is one of the useful engineered wood products for building constructions. The glulam beam can be used in design of the large-scale composite structures. The main concern about using glulam beams is their resistance, stiffness, and displacement. In this paper, glulam beams with different designs were reinforced with a rebar in bottom, top or both, and their mechanical properties were investigated using four-point bending tests. The test results showed that the ultimate loads of the reinforced beams increased compared to the unreinforced ones. The increasing of the maximum loads was 22% to 49% in the glulam beams with entire layers and 11-85% in the control glulam beams. The absorption of energy in the samples reinforced at the tensile and pressure parts is higher than the specimens only reinforced at the tensile part and the control ones. The amount of MOR depended on the type of reinforcement methods, originally. The reinforced control beams had a greater loss of MOE compared to the reinforced beams with entire layers. Also reinforcing resulted in a significant increase in the ductility of the beams reinforced in the tensile and pressure areas. Consequently, this is particularly important in the designing of the earthquake resistant beams.