نشریه توسعه پایدار جنگل
پیاپی 1 (بهار 1393)

Forest utilization is mostly associated with the harmful effects to forest ecosystem and changes in physical and chemical properties of soil and damages to the revival of natural and remaining trees. In this study, the rate of soil compaction on the skidding trails with steel tracked skidder LTT-100A is investigated by measuring some physical properties of soil (e.g. bulk density, moisture content and total porosity) in three classes of traffic in two skidding directions. The soil samples were taken by cylinder sampling method (cylinder 10 cm in length and internal diameter 5 cm) from a depth of 0-10 cm. The results showed that with increase of traffic on the skidding trails, rate of compaction increased significantly and the most compaction occurred at the second traffic of skidder. The amount of soil compaction on upward skidding was the more than downward. Thus skidding should be done in a downward direction and the landing will be constructed on the bottom of each compartment.

Tree increment has been under the influence of internal factors and external different factors. Throughout life, growth rates will vary depending on how the impact of these factors. Because the diameter growth, has fluctuations, at different heights in the stem. The aim of this study is to investigate the fluctuations of Pinus brutia diameter growth during the stem is done. For this purpose, the number of 31 pine trees were randomly selected and cut. Then from each tree, 5discs, from the different heights of the tree stem were taken. After preparing disks, annual rings width, using software COREL DRAW X5 and the accuracy of 0.001mm was measured. The mean diameter growth of trees in each height and stem length was analyzed using ANOVA and Duncans. The multiple range tests showed that the amount of diameter growth of this species is meaningful at different altitude sand in the mean Duncan regimentation are not in a group. The maximum diameter and basal area increment, throughout the stem, respectively was measured by 0.7 of tree high (from the ground) and stump height. Also, based on the analysis of growth curves, absolute age for the utilization of this stand, at the age of 20, was determined.

Roads have different advantages and disadvantages and also various effects on their adjacent environment. All these effects are studied by the science of road ecology. In this study the impact of roads on species diversity, organic matter and Carbon content was investigated. The current research was carried out in Patom district of Educational and Experimental forest of Kheyroud. At 10 points along the road-with distance of 100 m from each other- toward fill slope and cut slope, we established a 100-meter- transect perpendicular to the road, within which we consider ten 10×10 m plots to record the tree species, ten 2×2 m plots to record the herbal species and ten 0.5×0.5 m plots to sample soil and tree litter. According to the results, the road did not have any significant impacts on species diversity, organic matter and carbon content. The comparison between fill slope and cut slope shows some significant differences just in some distances. To conclude, the studied road is almost narrow and has limited traffic. Moreover, given that this road is constructed by forest engineers, unnecessary cut and fill operations are avoided, so the road is in balance with nature as much as possible and the habitat fragmentation is not so considerable. All these items can be numerated as important factors of moderating the negative effects of this road compared to previous studies, in which the roads are wider and less in balance with nature.

Spatial pattern is a key attribute of forest ecosystems. Recently, spatial distribution pattern of woody plants, especially trees, has gained many interest by plant ecologists which leads to introducing a large number of different methods for quantifying spatial patterns. In this topic, finding the easiest method for data collection and analysis has always been a major concern. The aim of this research is evaluating of Uniform Angle Indexability in determining spatial pattern of trees in a Hyrcanian forest. For this purpose, an area of 18 hectares in a forest reserve of Populus caspica was selected and surveyed by full callipering method, and stem-map of three major species including Fraxinus excelsiorsubsp, Populus caspica Born and Petrocarya fraxinifolia (Lam.) was prepared. At first, spatial pattern of all species was determined by Nearest Neighbor Index and the determined pattern was considered as an actual spatial pattern of the trees. For calculating Uniform Angle Index, 3, 4 and 5 neighbor trees around central randomly were chosen and the angles created between them was measured. Finally, obtained results of Uniform Angle Index were compared to the results of Nearest Neighbor Index. The results showed that in all cases, the determined spatial pattern Uniform Angle Indexwere similar to Nearest Neighbor Index. Based on the results of this study, Uniform Angle Index a quick and cost effective method which can be used for describing spatial pattern of trees in similar forests.

Different ecological factors influence on forming, development and sustaining of plant communities, among which physiographic variables are the most important ones. Physiographic factors including altitude, slope and aspect can impact on qualitative and quantitative characteristics of soils. The purpose of this study was determination of relationship between slope, altitude and canopy on soil chemical properties. The study was carried out in Tang-e-Dalab in Ilam province which is situated in southern Zagros. Three transects were sampled in oak stand (Quercus brantii). In each transect, samples had 50 meters interval. Soil samples were collected from soil surface (0-20 cm). Ten samples separately were located inside and outside of canopy in each transect. Totally, the number of 60 samples were selected. In each sample, altitude and slope percent was recorded. The results showed concentration of absorbable P, total N and organic C were decreased by increasing of altitude and slope percent in both inside and outside of canopy. Cumulation of soil nutrient has inverse relationship with altitude and slope. Phosphorus accumulation in soil showed the most correlation with altitude in both inside and outside of canopy but amount of N showed the less correlation with altitude and slope outside of canopy.

Forest soil is one of the main factors in forest ecosystem that with other ecological components determines vegetation distribution pattern. Natural areas such as forests have been severely harvest for various reasons in the past years which it has been made soil fertility reduction and production discontinuity. The aim of this investigation was to evaluate the physical and chemical properties of soils in Alder (Alnus subcordata) plantation in Tonekabon forests/North of Iran. For this purpose, at first, forested areas by pure stands of alder were identified. DBH and height of alder trees and their regeneration in each plot was measured. After gathering litter from the soil surface, soil samples were taken from 0-10 and 10-20 cm depths. The soil samples were transferred to laboratory and some important soil properties were identified. The results showed that the moisture in east aspect is more than west aspect. Also, there was a positive correlation between diameter at breast height, height and regeneration with moisture, Nitrogen, Phosphorus and organic matter and a negative correlation with clay, sand, electrical conductivity, pH and neutral material. Alder species can be used as a native species for plantation in similar soil conditions that it is economically and environmentally appropriate for northern forests.

Excessive presence of forest dweller and their cattle are most important agents that accelerate destruction of Zagros forest ecosystems. The aim of this study is to investigate of 7 years enclosure on woody species diversity and changes of soil physical and chemical properties in a part of northern Zagros forests. Two grazed and ungrazed areas were selected. Based on the transect method of sampling, 18 circular sample plots with an area of 400m2 were taken. The type and number of woody species were recorded. To analyze soil physical and chemical properties, a combined surface soil (0-20cm depth) was sampled and transported to laboratory. Results the t-test showed that status of richness and evenness indices in ungrazed area was better than grazed area and Shannon index of richness and Hill index of evenness were significantly different in both areas. Also, results of mean comparisons of soil physical and chemical properties showed significant difference in bulk density, silt, sand, Phosphorus, pH and Potassium in two areas. There were no significant difference for variables such as particle density, porosity, percentage of moisture saturation, clay, organic Carbon, Nitrogen and electrical conductivity in both areas. According to this study, enclosure leads to improvement of species diversity and soil physical and chemical properties during 7 years. However, it seems to enhance soil status and reconstruction of it in the ecosystems managed for conversation, much more time is needed.