Iranian journal of Forest
Year:2011 | Volume:3 | Issue:2|Papers Count:10

Rehabilitation of vegetation in degraded areas is one of the suitable strategies for conservation of valuable forest species. This should be done by technical and scientific methods, considering the land ecological capabilities. In some cases the density of pistachio saplings have been decreased and finally died after sowing, because they face sunny and warm months of the year while germinating. Hence this study was conducted in order to determine the best method for taking care of saplings after plantation. The research work was done based on Completely Randomized Design (CRD) with four treatments (sunny, 50% shadow, 75% shadow, 100% shadow) and eight replicates. A board coverage (1x1 m) was used for creating shadows.Sampling was conducted during 5 years, then data were analyzed by SPSS package. The results showed that in the first year, there was not any significant difference among treatments (p<0.01) in surviving, but differences gradually increased and at the end of fifth year there was highly significant differences among treatments, where Duncan test showed 100% and 75% shadow treatments had the most surviving percentages compared to the other treatments.

Hyrcanian forests are the only forests designated for commercial timber production in Iran. Ground-based skidding is the most common timber harvesting system used in these forests, but due to low road density (1-2m/ha), large parts of the forests are still inaccessible. To facilitate timber harvesting in the forest, it has been proposed to increase the road density up to 20 m/ha. The aim of this study was to incorporate the estimated skidding costs through a time study into existing transportation planning tool, NETWORK 2000 software package to help decision making on forest road building. This method was applied to Gorazbon district in Hyrcanian forests, where 244 links were built for analysis. The study used continuous time studies based on empirical data for this logging method. The resulted regression model is a function of skidding distance. The best solution found by NETWORK 2000 indicated that all proposed roads should be built to minimize the total skidding and road building costs.

In this research, Forest management Unit (FMU) of Forest and Rangeland Organization (FRO) is compared with FMU of local residents. For this purpose, stakeholder analysis and Analytic Hierarchy Process (AHP) were applied. For evaluating the probable effect of uncertainty in decision making, dynamic sensitive analysis was used. The result of AHP showed that the small FMU is preferable. By increasing the element importance’s which increase the weight differences of alternatives, the result of decision making is the same as the first alternative. So the result of this research is meaningful.

Forest tree breeding programs with the selection of plus trees in natural stands are very important to reach the highest utilization and production rate of the forests and products. Identification of Beech plus trees as one of the most important productive species in the northern forests of Iran has high value for gen preservation and extension of its stands. Thus, pure and mixed beech compartments in the first district of Shast Kalateh forests in Gorgan, were selected as the main distribution area of this species. Forty six candidate trees were identified by comparision method and were evaluated for twenty quantitative and qualitative traits with control trees. Then, final plus trees were determined using characters weighing and using scoring method based on calculation of the normalization equations. The results indicated that thirty seven individuals of total candidate trees and nine individuals of control trees were determined as final plus trees based on normalization equations of their grades. The results showed that this method has high precision in segregation of differences between plus and non-plus trees. Total height, stem direction, undulating and diameter growth, stem length without branch, branch angle and canopy polarity were known as important traits in identification of beech final plus trees.

Air pollution is a factor threating the green areas and vegetation in urban zones. Pollutant gases spreading with different density in urban spaces have destructive effects on vegetation along with climatic and antropogenic factors. On the other side, green spaces decrease noticeably the effects of pollutant gases on human society due to their ecological function. This study was carried out to find the effects of urban pollutant gases (SO2, NO2 and O3) and climatic factors (temperature and precipitation) on Fraxinus rotundifoliaMill. In Tehran. For this purposes, anatomical characteristics including leaf blade and cuticle thicknesses, epidermis thickness, blade mesophyll thickness, thickness and number of layers of spongy and palisade parenchyma mesophyll, blade vascular bundle thickness, number and thickness of collenchyma and parenchyma of main vein of Fraxinus rotundifolia Mill. leaves were studied by using correlation analysis.The results demonstrated an increase in leaf blade thickness, blade mesophyll thickness and palisade parenchyma thickness in response to increase in urban air pollution. Furthermore, the ratio of palisade parenchyma to spongy parenchyma (RP/RS) increased as the temperature rose.

Forests have had a vital role in survival, growth and development of human communities in various epochs of history. Overexploitation of the forest resources induced environmental disturbance leading to desertification and disappearance of civilizations. Deforestation has detrimental effects on the watershed environment which resulted in increasing flooding and sediment yield. Since long time ago, many studies have been conducted to evaluate the effects of managerial and engineering treatments on forest ecosystems characteristics. Since the hydrologic response of forest disturbance has been rarely considered, the present study has been conducted to investigate the effect of forest disturbance on hydrological components in sample plot scale with three replicates in the northern forests of Iran during seventeen storm events occurred from October 2009 to April 2010. The rain depth was measured by using a rain gauge installed in the study area. The runoff volume and sediment yield were also measured through field data collection and lab analyses by weighting and decantation methods. The results of the study showed significant effects of forest degradation (P<0.001) on hydrological components of runoff volume and coefficient, sediment yield and concentration. So that, the amount of runoff, runoff coefficient, sediment concentration and yield in disturbed area was found 5, 10, 18 and 6 times of those recorded for the undisturbed forest area, respectively.

Overexploitations of forests and degradation can be considered as a rational reason behind any reforestation project aiming at development and rehabilitation. For their specific characteristics, the forest plantations can affect the diversity of understory vegetation and cause ecological present or absent of herbs, forbs and bushes. The aim of the current study was to evaluate the floral diversity and understory vegetation cover in two reforestation projects (maple-ash and alder) planted in 1970s and a nearby natural stand located in the East of Guilan province, Iran. Twenty five plots (1000 m2) were random-systematically selected in each area.All measurements for forest trees as well as topographical features of the plots were considered. The diversity of the understory plants were also estimated using two micro-plots. One-way analysis of variance by means of the aspect and slope as covariances was run to evaluate the differences. Compared to forest plantations, the results showed higher diversity indices for natural forest. Alder plantation was also more diverse than maple-ash in case of micro-flora. Shannon diversity index and Simpson evenness index were characterized as favorite indicators to evaluate the plant diversity and distribution, respectively.

Control of logging damage is important for sustainable timber production in Caspian forests. Methods often recommend to control damage levels including directional felling and pre-felling design of skid trial.Directional felling needs felling crew with the ability of leading the trees to an accurate falling path. The present study is an experimental evaluation of felling crew ability for directional felling that carried out in compartment 207 of Nav district in Asalem watershed. A total of 25 trees were randomly selected from the total harvested trees by four felling groups. Falling path of selected trees was specified by paint on the trunk of trees and recorded by using a compass prior to and after tree’s falls. The difference between the intended and actual direction of tree's fall was then calculated for each felling group and an average margin of felling error was calculated for each felling group. Comparison of mean directional error for felling groups indicated that none of felling crew could direct the marked trees to desired path. The result showed that current felling is not according to goals of directional felling. Results suggested that felling worker in study area need more training program for reaching to the goals of directional felling.