نشریه تحقیقات منابع طبیعی تجدید شونده
سال دهم شماره 1 (پیاپی 31، بهار و تابستان 1398)

The ecological importance of deadwoods has led to an ever-increasing collection of related information to be taken into account in management plans. Considering the key role of deadwoods in forest ecosystem, the present study investigated some of the most important characteristics of deadwoods, including number, volume and spatial distribution pattern in a natural forest with beech dominance. For this purpose, two managed and unmanaged regions were selected from Gorazbon district of Kheyrudkenar forest in the vicinity of Noshahr as the study area and full calipering inventory of deadwoods was done. Moreover, species, diameter and height of standing deadwoods and in the case of fallen deadwoods, characteristics such as species, median diameter and their length were recorded and measured. In order to study the spatial pattern of the deadwood, the position of each deadwood was obtained by azimuth distance method using a laser distance finder and subsequently analyzed by univariate O-rings statistic functions. The results showed that the frequency of deadwoods were in the managed area more than of the unmanaged area, whereas the volume of deadwoods in unmanaged area was more. The highest number and volume of deadwoods were in low-diameter class of the managed area and in large and very large class of the unmanaged area respectively. The O-ring statistic showed that the spatial pattern of whole deadwoods in the managed and unmanaged area was completely random. Thus it can be stated that disturbances in studied area were in small scale. The amount of deadwood especially in managed area is not enough and its increasing is one of the requirements that with regarding to disturbance and structure pattern should be considered.

The aim of this study is to evaluate the dynamic and static of elastic properties of beech (Fagus orientalis) wood using conventional joints in woos industry including dovetail, tongue and groove beech wood with cyanoacrylate (CA) adhesives. Dimensions of experimental samples were determined 24×50×360 (mm) according to international standard (ISO No.3129). The results indicate that the effects of joint type, joint size, and retrospective joint size became meaningful in dynamic and static tests (p<0.05). Elasticity module for dovetail joint due to the shape, homogenous joint texture, and lack of extended adhesive line in the joint is closer to unjointed samples (control group). Based on the Student's t-test and Pearson correlation test, dynamic and static elasticity modulus had statistically significant positive correlation (p<0.05). Regarding to the correlation of dynamic and static tests, methods for non-destructive dynamic investigation may be used as appropriate alternatives to destructive static tests for assessing and classifying the woods.

In order to study the effect of distance and decay class of Oak (Quercus castaneifolia) fallen deadtrees on some chemical properties of soil, parcel 238 with an area of 37 hectares from district 2 of Siahkal forests, Guilan, Iran was selected. Total of 32 deadtrees from oak species were identified and surveyed. Regarding to four decay classes, three oak deadtrees in each class (12 specimens) were randomly selected. Then the length of each deadtree was divided into four equal parts and a soil sample was taken from each part in depth of 0- 20 where they mixed together as a soil sample of each deadtree. The results of data analysis indicated that soil nitrogen of deadtrees with decay class 4 was significantly different from others and its transfer rate increased with increasing of decay classes. Moreover, organic carbon, potassium, and phosphorus amounts were higher in the soil under deadtrees and decreased with increasing distance of them. The highest amount of soil phosphorus and potassium belonged to deadtrees with decay class 1, and soil organic carbon increased with increasing deadtrees decay degree. However, there was no significant difference in soil acidity of deadtrees with different decay class and distance. Therefore, the Findings of the current research illustrated that the properties of soil could be changed based on decay class and distance, and due to the increasing and decreasing trend of soil parameters over time, deadtrees with different decay classes are essential and should be considered in forest management.

In this research, the effect of rice husk flour and the amount of clay nanoparticles were investigated on the physical and mechanical properties of wood-plastic composite. For this purpose, rice husk flour in three levels of 30, 40 and 50%, and nanoclay in three levels of 0, 3 and 5% were used. Corn starch was used as the polymer in this research. The materials were mixed in the extrusion machine and standard test samples were made using injection molding method. Mechanical properties including tensile and flexural strength, tensile and flexural modulus, the elongation at the breaking point and impact resistance as well as physical properties including water absorption and thickness swirling were measured. The results showed that tensile strength and flexural strength, flexural modulus, the elongation at the breaking point, and water absorption of the composite increased with increasing the amount of flour of rice husk from 30 up to 50%, but the tensile modulus, impact resistance and thickness swirling decreased. By increasing the amount of nanoclay from 0 up to 5%, the tensile modulus was regularly increased and the elongation at the breaking point decreased regularly. However, flexural and tensile strength, flexural modulus, impact resistance of the composites increased by adding nanoclay to 3% and then decreased by adding 5% nanoclay. Water absorption and the thickness swelling of the composites decreased with addition of nanoclay.

In this study, the effects of different dietary levels of synthetic tryptophan on some growth parameters and carcass quality of rainbow trout was investigated. For this purpose, 120 fish (mean weight 6.5±0.4 g) were randomly distributed in three treatments with four replicates and fed with diets supplemented with 0 (control diet), 0.2%, and 0.4% tryptophan for 8 weeks. Results showed that addition of tryptophan at 0.2 and 0.4% levels significantly improved the weight gain, specific growth rate, daily growth rate, and survival compared to the control group (p<0.05). The lowest feed conversion ratio (1.01±0.04) and highest protein yield ratio (2.48±0.02) were observed in 0.4% tryptophan treatment (p<0.05). There was no significant difference in length gain and condition factor between treatments (p>0.05). The highest crude protein (61.62±1.21%) was observed in 0.4% tryptophan treatment, which was significantly different from those in control and 0.2% tryptophan treatments (p <0.05). There was no significant difference in moisture content between treatments (p> 0.05). Regarding the carcass amino acids profile, the highest amounts of methionine (1.59±0.02%), methionine + cysteine (2.15±0.03%), threonine (2.35±0.01%), isoleucine (2.37±0.04%), leucine (4.20±0.06%)و and valine (2.81±0.03%) were measured in 0.4% tryptophan treatment (p<0.05). In general, findings of the current research illustrated that most growth parameters of rainbow trout were improved by adding tryptophan to the control diet, although the fry carcass had higher amino acid and crud protein values by supplementing diet with 0.4% tryptophan.

Natural ecosystems have different functions and their services are in accordance the receiving society benefits. The aim of this research was to valuate rangeland ecosystems services including forage production, honey production, carbon sequestration, and oxygen supply (regulating gases) in Maleshoure and Gurgo rangelands in Boyer-Ahmad city. In order to determine the function of gases regulation, vegetation of the study area was evaluated, annual aboveground and underground growth of plants was calculated and the oxygen production and carbon dioxide absorption in annual growth were estimated based on the photosynthesis method. To evaluate the carbon sequestration function, carbon tax policy was used as a carbon shadow value and the value of oxygen supply function was also calculated using the alternative cost method. Production functions such as forage and honey were determined by market method. According to the determined price of one kg of produced forage (8446 Rials) and the total amount of useable forage in rangelands, the economic value of total forage in rangelands of the studied region was estimated 6559.8 million Rials per year. Regarding to the results in related to the economic value of carbon sequestration and oxygen release by the rangeland ecosystem, value of gas regulation function was estimated to be 732729.3 Rials per hectare and 5861.8 million Rials in the whole region. The findings showed that the rangelands of studied region in terms of honey production function have an annual average value of 131800 Rials per hectare. Forage production function has the highest percentage of total economic value.