نشریه علوم و فنون منابع طبیعی
سال هشتم شماره 2 (تابستان 1392)

Wych elm (Ulmus glabra Huds.) is one of the most important species in Northern Forests of Iran that due to illegal logging and Dutch elm disease its presence in the forest ecosystems is in danger of being eliminated. The correct management of forests needs to identify the ecological characteristics of trees. In this research, some of ecological characteristics of Wych elm trees were studied in 215 hectare, 800 to 1400 meters from sea level, in Asalem Nav forest area in the north of Iran. After field inspection, all Wych elm trees whose diameter at breast height (DBH) were greater than 10 cm were identified and their quality and quantity characters were measured. Inaddition, physiographical characteristics of sites were recorded. For studying trees diversity and species importance, the value of each wych elm tree was taken as center of sampling plots (round shaped and 1000 m2 area) and DBH was measured. Soil sampling followed the spatial pattern of wych elms. The results showed that density of wych elms in the study area was 0.32 stem per hectare and averages of height and DBH were 18.8 m and 48.5 cm. Respectively Frequency, quality and quantity of wych elms in the northern aspects were 800 to 950 m from sea level, 25 to 50% of slopes respectively, the foots and sandy loam soils were more and better in quality than other sites. With increasing height from sea level, frequency of wych elms decreased in northern slopes, but increased in southern slopes. Natural sites of wych elms have fertile soils. With regard to the little density of wych elms in the stands of study area, special silvicultural activity is necessary to conservation, reconstruction and development of this species.

Forest is one of the most valuable and renewable natural resources that its importance and critical role is increasingly becoming apparent. Roads and other linear structures are most important examples of human activities, and they have the most significant environmental impacts on natural habitats and ecosystems of the world. For this study part of the forest roads Series 8 Larovchal was chosen. In order to collect necessary information, with using the inventory 100%, in the first 3 tapes with length of 100 m, total to 300 m length of forest roads and three strips with a width equal to 25 m length of 100 m, at each side of the road (bottom and top of the road), the study was done. Results showed that species diversity of tree at the bottom of road is more than the top side of high road. In addition, Specie diversity on both sides of the road from border to
within of mass reduced and specie combination changed so that specie of Alnus has appeared only in the first tape. The number of trees per hectare was the highest in the border road. The quality of trees with increasing distance from the road increases in the bottom of road, while in comparison with the top of road, the case was opposite. With increasing distance from the border to within of mass the average diameter of trees increased. While average diameter of trees for the top of road decreased with increasing distance from the road.

The purpose of this study was to qualify the carbon sequestration in relation with soil physicochemical characteristic and tree species composition in Kheiroodkenar educational forest of the Tehran University. The area of the study location was about 1100 hectare. To achieve the purpose, 32 soil profiles were excavated and soils were collected from 3 layers, including 0~30, 30~60, and 60~100cm. Different soil characteristics including, texture, pH, bulk desity and organic carbon percentage were measured. The sequestrated carbon was estimated by multiplying the bulk density by the percentage of organic C for a predetermined sampling depth. The results showed that most common soil
orders in the studied area were luvisol and cabmisol fitted with alfisols, inceptisols in USDA soil taxonomy. The total soil organic carbon was around 1307 ton per hectare from 0 up to 100 cm. In addition the results indicated that carbon stores of the top soil layers (0~30cm) was 686, second layer (30~60) was 310, and in the last layer (60~100cm) was 302 ton per hectare. Using C14 for age determination, the soil age was determined 6839±440 years.

The aim of this research is reviewing the effect of management intervention on qualitative and quantitative characteristics of forest (stand) by comparing a managed parcel with an evidence parcel. In addition to help the next planning, to predict the future condition if the current management continues for the next period.
This study was carried out in the north of Iran, at watershed no 45, Seri of Jamand. For the above purpose, two parcels, 317 and 318 with more similarity on type and other ecologic conditions, 64 and 47 hectares respectively were, selected as managed Parcel and unmanaged parcel. The method of sampling was systematic random method. The distance between sample network was 100*150 m and the shape of samples were circular with area of 1000 m2. The primary inventory completed with more samples, because of heterogenity of forest and inaccessibility to accepted accuracy, finally 47 sample plot for managed parcel and 50 sample plot for unmanaged parcel were taken. In each sample all quantity characteristics of trees with dbh > 7.5 cm and quality factors for dbh > 37.5 cm were measured. The results show that although the number of trees per hectare in managed parcel is more than the unmanaged parcel, the volume and basal area is significantly less, In other words it shows the existence of thick and old trees in unmanaged parcel and younger trees in managed parcel, In addition it specified that the reason for the increase of hornbeam species is because of centralized management operation on beech logging which affected forest characteristics. Also the result of quantity reviewing shows that management operation had negative effect on stand quality, such as health of trunk and crown, crown homologous, and centralizing logging on high quality beech trees is the cause of quality decrease in managed parcel.

For the purpose of the effectiveness of the dead trees on the forest regeneration, they were divided into four degrees in terms of the rate of decay. This study has been carried out with the aim of investigating the role of the dead trees on establishing natural revival of forest communities in the district 3 of Gorazbon region in the sample plot 309 of training-research forest of KHEYROOD region in a sample plot almost intact with an area of about 47 hectars. Out of 46 trees of the dead trees, the hundred percent inventory was carried out. Around the standing trees, a circular sample plot with a radius of 5.64 m from the dead trees centrality was established (130 cm) and the numbers of saplings were counted in three height classes. For fallen dead trees around both ends of a dead tree, a square of 4 m width (2m from each side) was established, the number of saplings were counted and for the comparison of regeneration around a dead tree, a sound tree was designated at the distance of 20 up to 30m from a dead tree, and the number of saplings were counted as before. The results showed that the most of the dead trees on the basis of the decay degree belonged to the beech species and was of the degree 4, the difference at the level of 95% is meaningful in comparison with the other degrees of the dead trees. According to the results obtained, the number of regeneration around the dead trees were more than that of the sound trees, and most of the saplings established around the dead trees were observed with the degree 4 of decay. The general results indicate that the dead trees have significant effect on establishing the revival of the beech saplings in forest mixed with beech, especially in thick stocks.

In this study, the effect of type and lignocellulosic filler content on some mechanical properties of wood plastic composites (WPC) made from the flour of Aspen and Bamboo and pure HDPE was investigated. first the samples of wood plastic composites were manufactured from mixed Aspen and Bamboo flour and pure powder of HDPE with 40 to 60 fiber weight ratio.Then some mechanical properties were manufactured by ASTM standards test methods, and the data were statistically analayzed. The resuls showed that WPC made from lignocellulosic filler content had the most of bending strength , tensile strength , flexural modulus and tensile modulus and the least of unnotched impact strength.

The purpose of this study was to explore chemical compositions & biometric characteristics of fibers ( Length, diameter& thickness of fibers rim) and derived coefficients of them on Teda pine cone in Astara region in Guilan province. The cones were chosen at random and then their chemical compositions were measured via TAPPI regulation standards. Their biometric characteristics were measured by Franklin method and their biometric coefficients also were computed. The statistical analysis of the result showed that the average is 26.5%, 1%, 2.45%, 7.28% for seloloz, Aseton and water respe tively. According to the results of darken multi scope testing; thickness of fibres in scab was more than stem. This is true for the length of fibers and the diameter of cellular fossa. The ratio of flake Slenderness was more than stem while flexibility ratio in stem was more than flake and there were significant differences about 5%. But with regard to the thickness of cellular rim and Rankel ratio. Were not observed. significant differences about 5% between flake & stem .

This research was done with the aim of investigating natural durability- In this study the effect of coriolusversicolor fungus (identificated as white rot) on populusdeltoides in natural and treated situation was analysed.In conducting the mentioned evaluation, kolleschal method according to DIN 52176 and B.S. 838:1961 was used in completely randomized block design. Specimens were contaminated with cultured fungus for 14 weeks. after this period weight reduction and leaching were measured. Results have shown that the effect of treated nano silver on durability of populus deltoides was positive and the average of weight reduction of control sample and 200ppm was measured more than 400ppm,so that according to Findlay 1967 classification this type was
promoted from completely non durability to less durability. Leaching, According to Duncan’s multiple range test, the difference between samples with 200 ppm and 400 ppm is significant at the 0.05 level and the mean for the samples with400 ppm was calculated to be more than that of the samples with 200ppm.

In the present research, the decreasing process of green space expanse and woodsy cover in central part of Rasht county during a period of 13 years (1368- 1381) using Landsat satellite TM5 - ETM imagery was considered. For this purpose, with applying remote sensing technology and using softwars ENVI and Geography Information System "Arc GIS", Vegetation Index "NDVI" was Provided. After applying NDVI, the produced layers of above process were converted to vector and were transferred to Arc GIS software for calculation and production of final maps. In addition to checking the changes in vegetation cover of the region during the study period, produced NDVI imageries of processing were compared with each other in ENVI environment with using change detection. The result of calculations on satellite imageries indicate quantitative and qualitative changes, so the area of dense woodsy cover of central part of Rasht county, from 123 km2 in 1368 has decreased to 33 km2 in 1381, there fore it has had considerable effects on ecosystem in this region. Furthermore, considerable decrease in central part of Rasht County can be observed.

Climate change and global warming is one of the important challenges of sustainable development which is the result of green house gases increment. Carbon sequestration in herbal biomass and the soils under them is being considered as the easiest possible solution to reduce the atmospheric carbon and it is also the most practical way from a economical viewpoint. Regarding to the high potential of arid regions to absorb the atmospheric carbon and modify climate change in order to estimate the carbon sequestration of ¡Haloxylon sp planted in Zavareh region, the sampling of biomass, soil (in two depths of 0- 15cm and 15-30cm) and litter was done randomly-systematic. Carbon
sequestration in plant biomass through allometric equation and soil organic carbon through Walkley-black method was measured. The results showed that the species of Haloxylon aphylum and Haloxylon persicum led to carbon sequestration increment to the extents of 24.1 tons per hectare as compared with the Control zone around, while their economical values in total area of afforestation in Zavareh was calculated 12 million dollars. The results of carbon distribution showed that the soil organic carbon content was >45% of total carbon sequestration. It was concluded that Haloxylon sp. has a high potential
for carbon sequestration and soil is the most important sink for organic carbon storage in these regions. Considering the results of this study it is integral that necessary activities should be done in different fields of the country to increase the potential of carbon sequestration to make the ecosystem more sustainable and to provide basic changes to face the climate change.