نشریه علوم و فنون منابع طبیعی
سال دوم شماره 4 (زمستان 1386)

In order to study the causes of reduction in the poplar plantation level in the central province, a region in the west part of this province, located in Khondab district, a part of Arak, alongside the Garachi river, beginning from the Doab bridge and the Mahdiabad village and continuing to Khandab, was investigated. The statistical samples of this study include 5114 poplar planting families from which 900 were selected based on Koukran formula, and they filled out the questionnaires. The relative simple randomization method was used to select the sample subjects. After collecting and classifying the data, the principles of descriptive statistics were used. The results of the study showed that the low level of villager's education and the use of old and traditional methods (little and late productivity), and their unfamiliarity with new and improved species and methods of poplar blending plantation were the main reasons for the reduction of poplar plantation level and the change to fruit gardens, especially the peach gardens (due to its early productivity and suitable market).

The study and determination of vegetative elemens with similar ecological needs are important steps to identify the plant communities and to study the edaphic conditions of habitat in different plant communities. Accordingly, the present study deals with the plant communities and their relationships with edaphic conditions in Manesht forests of Ilam province. To this end, the Braunblanquet method was used and the vegetation data were analyzed with Pc- Ordwin software. After recognizing the plant communities and determining indicator and preferable species with the use of TWINSPAN and DCA analysis based on the maps of land form, land type and vegetations and overlaying of the above-mentioned maps, the locations of digging profiles were determined and the soil was sampled. Soil samples were analyzed chemically and physically and soil data were also analyzed. The results showed that there are three recognizable communities for this region, namely Amygdalo- Daphnetum Mucronata, Pistacio-Acertum Cinerascentis and Quercetum Brantii. With regards to edaphic conditions of the habitat in different plant communities, it can be concluded that Pistacio-Acertum cinerascentis and Quercetum Brantii communities are on the insepthisol soils and Amygdalo- Daphnetum Mucronata community exists on the enthisol soils. Based on the PCA analysis, the soils of Pistacio-Acertum Cinerascentis and Quercetum Brantii communities are more fertile than the soil of Amygdalo- Daphnetum Mucronata community. Also, in Quercetum Brantii community in Iran, the soil is lighter, more drained, and its depth is more.

To study the effect of storage time on the germination of oak seeds, the selected seeds were stored at , -1, -8 temperatures under the cool house conditions. Then we dealt with the sampling and culturing of seeds after one week, two weeks, three weeks, one month, two months, four months and six months intervals. The seeds were cultured in two methods (with sand bed and non sand bed). Then the germination was measured. The results showed that germination had a decreasing process with the passage of storage time, but it was lower in seeds with no bed. The results also indicated that the germination of seeds takes place in a shorter period after two months of their storage. In addition, the seeds will not germinate while stored under 4°C, and if their storage period is increased for more than 2 months. By surveying the seeds stored under -8°C, we observed that they would be frozen and destroyed after three months. The general conclusion is that seeds can be stored for a short period at 4°C, whereas for a longer period, they should be stored under -1 or lower temperatures.

In this study, the influence of fungus (Coriolus Versicolor) on the durability of Cuperssus (Cuperssus Sempervirens) in a natural state by the use of Kolleschale s method and according to DIN 52176 and BS 838 standards was investiguated. For this purpose, the Neirang region with an altitude of 40 meters above the sea level in Nowshahr area was selected and three trees were randomly selected and cut down. For each tree one piece with 1.3 meters long from one meter above the ground level was cut, and these speciments were taken to the Chaloos Azad university labrotory in order for their mechanical and weight loss properties to be investigated. The speciments were contaminated with cultured fungus for fourteen weeks (in a condition of 25 c and 75% relative humidity). After this period, the weight loss, compressive strength parallel to the grain and hardness of speciments were measured compared with control speciments. The results indicated that the speciments from the altitude of 40 meters above the sea level and with the 20% weight loss were amongst less durable woods. The compressive strength (parallel to the grain) and hardness of speciments for the control samples were 3.12 kg /mm2 & 203.4 kg respectively, which decreased to 1.87 kg /mm2 & 190.3 kg due to the white rot effect. Therefore, this reduction was statistically significant at 5% level compared with control samples.

In this study, the birch beech and horn beam woods were randomly selected from the Mill wood and pulp industry of Mazandaran, from which the chips were prepared, and the pure CMP pulp by 85% yield was prepared according to TAPPI standard tests. Then the fiber biometric traits, the chemical components of wood flour and CMP pulp, the percentage of reduction of their chemical components and handsheet properties were measured and statistically analyzed. The results showed that the fiber length of imported birch is less than the horn beam but more than the beech. The fiber diameter and cell pit were greater and the cell wall thickness is smaller than the beech and horn beam. The chemical components of the imported birch wood have the smallest klason lignin and the greatest holocellulose. The handsheet properties of CMP pulp produced from the species under the study showed that the bursting strength and breaking length of the papers made from the beech and horn beam woods were lower than the birch wood.

In this study, the growth, biometric, and physical properties of populus deltoides spp wood from four clones of P.d. 77/51, P.d. 69/55, P.d. 73/51, and P.d. 72/51 located in the educational-research forest of Dr. Bahramnia (the Shastkolateh forest) in the province of Golastan were investigated. For this purpose, three twelve years old normal populus trees were randomly selected and cut down from each clone, and then their growth, biometric, and physical characteristics were measured. Then the data gathered were statistically analyzed. The results showed that clones affected significantly all the parameters, including the tree height, diameter at breast height, stem volume, annual diameter increment, fiber length, cell wall thickness, density and volumetric shrinkage. The results also indicated that the P.d. 77/51 clone of populus deltoides spp, from the growth, biometric, and physical characteristics, was the highest of all compared with the other clones.

In order to study some properties of Wood Plastic Composites made from Lignocellulosic filler and HDPE, panels with rice husk flour and sawdust of wood (as fillers) and raw and waste powder of HDPE( as plastic) with the fiber weight ratio of 60 to 40 were manufactured, using a dry blend/hot press method at constant pressure and temperature. The physical properties such as water absorption and swelling thickness and mechanical properties such as the static bending according to standards of ASTM D-7031-04 and ASTM D-1037 were measured and compared with MDF and particleboard. The results showed that the water absorption and swelling thickness of Wood Plastic Composites in question were less than the MDF and particleboard. The WPCs made from rice husk flour and HDPE waste had the lowest water absorption and swelling thickness in general. The flexural modulus and the bending strength of MDF and particleboard were less than the Wood Plastic Composites.

The logging of trees like the other processes of utilization will create lots of damages for the residual stands in forest. The identification of the types, severity (amount) of the incurred damages, and factors bringing them about are of paramount importance. The aim of this study is to survey the effect of the diameter of trees logged in the residual stands in the fifth section of Valila series of the Mills plan of saturated timbers in Shirga. At first, 50 trees (20%) were randomly selected from 250 marked trees from the various diametrical classes based on the marked protocol. Then 50 semicircle sample pieces in an area of 1500 square meters were selected, and the quantitative (diameter equall to breast and height), and qualitative (eradicated, cracking of crown and stem, and stem and bark peeling) characteristics were measured and registered before and after their logging. The results showed that the diameter equal to breast of logged trees, except in their eradication, can directly have significant impacts on the extent of stem and crown cracking, damaging of stems and peeling of trees, and the greatest damage was also due to the logging of trees in the diametric class of 80 cm and above it.