مجله جنگل ایران
سال پنجم شماره 1 (بهار 1392)

Forest workers are exposed to many noise sources such as chainsaw. Chainsaw these days is the only cutting trees instrument used in Caspian forests. The purpose of this study is to measure the noise of pressure levels of chainsaw and to determine the duration of worker exposures to that noise. The study area is located in Namkhane district, Kheyrud forest. The noise intensity of chainsaw and duration of cutting time in bucking phase were measured every 15 seconds, and then the average of noise intensity and cutting time for each trunk were calculated. The results showed that the workers usually work in exposure to the noise (107.9 122.7dB) higher than the standard level (85dB) that approximately shifts to painful threshold. The duration of bucking time was between 0.12 to 12.03 minutes and the noise intensity was 116 dB. According to the Iran standard and ACGIH, the standard bucking time is 24 seconds, while in this study it was 12.02 minutes. The duration of bucking time was more than standard level most of the time (more than %95 of time study). This study also showed that by increasing the trees trunk diameter, workers will be more exposed to the noise.

Environmental impact assessment (EIA) is an effective way to protect the natural resources. Due to needs of human to nature and undesirable effects of over-exploitation on the environment including soil, environmental impact assessment process must be applied in determining the goals, studying the basic conditions, also forecasting and estimating the environmental impacts of project implementation. In this study, fuzzy modeling has been used to assess the environmental impacts in Nour forest park. Three regions containing intensive recreation, extensive recreation and control region were selected, and 30 sample plots were then established in the region as random-systematic. The number of tourists and duration of residence in each sample plot were calculated as input indicators and soil sample was considered as output index. Output and input indicators, classification and fuzzy rules were defined based on Mamdany system. Comparing Model’s results with experimental data showed mode’s error is 6% indicating that model accuracy is favorable. The results showed that with increasing the number of tourist and duration, soil bulk density is also increased, and when the number of tourist reaches to 20 people and duration to an hour, maximum soil compaction occur and further increasing of two factors have no effects on soil compaction. The results also indicated that a fuzzy modeling capability is suitable in predicting the effects of recreation activities and determining the capability of region.

The aim of this research is to determine the optimal harvesting using dynamic programming in Shafarod forests at Guilan province. First of all, a logistic growth function was used to predict the growth model. Then, wood price function and variable harvesting cost function were estimated based on an autoregressive model and time series data. Finally, the optimal cutting maximizing the expected present value was computed using growth, price and variable cost functions. LINGO software was used for cutting optimization. Minimum acceptable volume, growth model, wood price at forest road side, variable harvesting cost, planning horizon, interest rate, and moving of cutting groups and harvesting equipment werecoded in LINGO software. Results indicated that the optimal cutting varies between 6 to 12 m3 per hectare in various stocks during 100 years regarding to the volume average of the study area (490 m3/ha) and the minimum acceptable volume (100 m3/ha).The maximum expected present value was estimated 323326 thousands Rials during 100 years. Sensitivity analysis showed that the optimal harvest could fluctuate over the planning horizon based on the volume average of the study area and the minimum acceptable volume even which in some cases harvesting is not required.

The aim of this study was to investigate the effect of the productive and harvestable area instead of the total forest area on the allowable cut and financial indicators of a forestry planning in Kheyrud forest. Therefore at first, regardless of forest productive and harvestable area, allowable cut and financial indicators for a period of 10-year forestry planning were computed. Then by applying productive and harvestable area rather than the total forest area, allowable cut and financial indicators for a period of 10-year forestry planning were computed and compared with the first case. Ten-year allowable cut of district using harvest coefficient of 05, 1 and 2% was 16897, 33793 and 67586 Silve, respectively for the first case and 15859, 31718 and 63437 Silve for the second case. Present net value of forestry planning for the first case applying harvesting coefficient of 05, 1 and 2% was -5910.77, -2036.81 and 11509.75 million Rials and internal rate of plan return was calculated -31%, 7% and 29%. Present net value of planning in the second case for 05, 1 and 2% harvesting coefficient was computed -5976.01, 1990.92 and 10099.54 million rials and Internal rate of return plan was -33%, -8% and 26%. By applying forest productive and harvestable area, harvesting amount will be lower than the case in which the above-mentioned factor is not considered. This issue is more consistent with the fact and causes that more than forest productive capability is not harvested and sustainability of forest production is conserved in the long term.

Specialists believe that organizational actors use both formal and informal collaborations to achieve their goals. Although informal relations have been caused restrictions in organization efficiency, but recognition and proper management of these relations could be useful in organizational workflow. Natural Resources Organization of Hormozgan Province, in spite of usual inefficiencies such as lack of sufficient experienced human resources, totally has been successful until now. This research was done in order to delineate and analysis the formal and informal relationship networks between the staffs of this organization and also to answer to these questions: whether informal relations of this organization form a network? Whether this network has positive impacts on formal relations or negative? Is formal relationship network similar to existing organizational chart? In this regard, Network Analysis Approach, UCINET and NetDraw softwares, and input and output degree centralities and betweenness centrality were used. Results showed that informal relations of this organization form a network and its strengths caused to positive impacts on formal relations. Also formal relationship network, more and less, is similar to existing organizational chart. Finally, it is concluded that network analysis as a new approach in managerial problem solving could be so helpful for managers in recognition of effective actors in formal and informal relationship networks and also to increase the human resource efficiency.

The present study were conducted to determine the potential habitat of olive (Olea europea L.) species adapted to Mediterranean climate in order to expand the native and man-made forests of Chaharmahal va Bakhtiary province using Geographic information systems. The first step of the project was to collect the athand data and maps. Then three different data layers were extracted from topographic maps with 1:25,000 scales. For climatic sorting, the province was divided into three homogenous sub-regions and regressions models were calculated. The required climatologically layers were created through DEM for various dry months. Digitizing the available existing soil maps from various sources led to six layers in data base. The land-use layers were produced in eight layers including irrigated agriculture lands, rain fed agriculture lands, range lands, forest lands, agro forestry lands, bare rock lands, urban lands and other lands. Considering the ecological requirements of the selected species, the produced environmental data layers were combined with Boolean and Fuzzy logics to depict the potential habitat. The areas of these sites were 8708 and 7238 ha with Boolean and Fuzzy method, respectively which decreased to 693 and 2010 ha after considering soil texture limitations.

The effect of lead in hydroponic medium on leaf gas exchanges of two species of aspen and cottonwood, together with some other physiological indices including relative water content, maximum electrolyte conductivity and electrolyte leakage ratio of different organs and efficiency of photosystem II were investigated. One year old saplings of two poplar species were gradually subjected to chelated lead (PbCl2) treatments with concentrations of 15, 45 and 90 part per million in medium and were harvested two weeks after reaching to the final concentration. The results revealed that maximum electrolyte conductivity of leaves in both species increased under severe treatment, but the increment of lead concentration only in cottonwood was accompanied by increment of electrolyte leakage ratio. Relative water content of organs remained constant in both species, whereas increasing lead increment up to 90 ppm diminished stomatal conductance of aspen, and not affected cottonwood. Both species were able to maintain photosystem II efficiency under stress, but net photosynthesis ratio reduced in aspen. The photosynthetic limitations in both species was observed regarding to reduction of intrinsic water use efficiency (A/gs), that in aspen it was mostly posed by stomatal, and in cottonwood it was due to non stomatal restrictions. It can be concluded that, in cottonwood plants grown in the presence of excess Pb, plasma membrane integrity and efficiency of enzymes are related to carbon fixation which impaired due to maintenance of stomatal conductance and transpiration rate, whereas depletion of stomatal conductance in aspen prevented physiological damages.

Feeding behavior of white grubs (Melolontha kraatzi persica R.) in soil causes damages on weeds, natural regeneration and various trees. This research studies the density of white grubs in different plantations of Alder (Alnus subcordata C. A. Mey.), Oak (Quercus castaneifolia C. A. Mey.), Maple (Acer velutinum Bioss.) and Cypress (Cupressus sempervirens var. horozontalis) with the adjacent mixed broad leaved stand in Darabkola, east of Mazindaran province in the Caspian region. To determine the seasonal variation of density, twenty samples were taken for each season. First, at each treatment one-1 ha sample plot was selected and then ten-0.01 ha circular sample plots random-systematically were established. Samples were taken from the depth of 30 cm and small white grubs were extracted using Berlese funnels and were counted by binocular. Various parameters of the stands and soils were recorded in each plot. This study showed that the mean annual density of white grubs in the Cypress plantation was the least, whereas in the Maple reforestation, it was the highest. The differences of density among other treatments were not statistically significant. However the population density of Melolontha kraatzi persica in this region was not significant regarding to a serious drawback to the stands. The analysis of PCA showed that the parameters of the density of white grubs, number of trees, number of vegetation cover, relative light intensity (as an indicator for soil heat) and moisture content of soil take an important role in seasonal differences of white grubs in each treatment.

The effects of different irrigation regime on survival and growth of holm oak (Quercus ilex L.) plantationwas studied in a semi-arid Mediterranean climate condition located in Marzanabad region (Mazindaran province). This study was done as Randomized Complete Block design with three replicates and four treatments, including no-irrigation and irrigation with 10, 20 and 30 day periods during dry months in growing seasons (spring and summer). Climate data analysis showed that a severe frost and three to six dry months annually occurred in growing season during study years (2006-2010). Height growth and survival of saplings were measured every year and at the end of 5th year. Analysis of data showed that irrigation treatment with 10-day intervals with a 65% survival is preferred and differences are significant (p %1). No difference was seen among treatments from height growth point of view. In general, the most important restricting factor on holm oak establishment and growth in this area are alkaline soil and dry environment conditions.

Tree cutting can affect different aspects of forests. To investigate the changes on snow accumulation, density and temperature due to tree cutting in the forest, two forestry regions were selected, one control and the other the cutting region. For measuring snow accumulation, 10 pickets in cut area and 10 pickets in control area were installed and snow height was measured every 5 days. For determining the density, a snow profile was dug and sampling was done with 500 cm3 sampler from different depths every 5 days. Finally snow temperature was measured in different depths with thermometer. The results indicate that the average of snow density in cutting region and control region are 0.178gr/cm3 and 0.151gr/cm3, respectively and there isnt any significant difference between them. Also decreasing in canopy due to tree cutting has a significant relation with snow accumulation and its depth, which increases and they all together result more snow accumulation. So average of snow height in control region was 13.88cm and after cutting increased to 21.15cm. Snow temperature increasing is significantly related to the decreases in canopy. Therefore the average of snow temperature in control region is -3.3°C which decreases to -10.3°C by cutting the trees.