مجله جنگل ایران
سال هشتم شماره 2 (تابستان 1395)

Biomass and carbon sequestration potential is one of the most important benefits of trees in forest ecosystems. This research was done to estimate the amount of biomass in individuals and coppice forms of Quercus brantii Lindl. in Balootboland forests near the Dehdez, Khozestan province. Grid dimensions were selected 100 × 100 m and the nearest tree to a sampling point was chosen. Selected trees should include all diameter classes of high forest or individual trees and all crown diameter classes of coppice if possible. Totally 18 individuals were selected and their quantitative parameters were recorded. Cutting and separating operations were then performed. Different parts of trees were immediately weighted after cutting in the field and sampling was performed to measure the dry weight and the amount of carbon sequestration. According to the results, there was no statistically significant difference between the biomass in two forms of growths. The average biomass of above ground for each tree was approximately determined 277kg and 230kg in form of individual tree and coppice, respectively. These amounts in the stands for individual and coppice forms were estimated 18.2 and 9.3 tons per hectare, respectively. According to the results, large organs (trunk and branches) and small parts (twigs and stump) have more carbon sequestration potential in individual and coppice forms, respectively. The highest and lowest amount of carbon was stored in branches and leaves, respectively.

Nowadays, wood farming with fast-growing species such as poplar species is inevitable. This study was performed to investigate the effect of different spacing on the production, biomass and the type of wood using of Populus alba in 10-year-old poplar plantations in fast-growing poplar research center of Boldaji city and Korran village of Farsan city, Chahar Mahal and Bakhtiari province. For this purpose, four one-hectare plantations with these species with four different plant spacing (0.5 × 0.5, 1 × 1, 2 × 2 and 4 × 4 m) were selected. Diameter and height of trees were measured and 10 trees in each region and totally 40 trees were selected. These trees were then felled down, cut and weighed in field by separating into trunks, branches, sub-branches and leaves. Several samples from different parts of felled trees were also obtained and transferred to the lab. After drying in 80 degrees centigrade, samples were weighed with digital scale with 0.001g accuracy and dry weight of each part was calculated by using proportionality. The results showed that 0.5 × 0.5 m spacing had the most production with 735.88 tons per hectare and 475.65 tons per hectare and 2 × 2 m spacing is the suitable plant spacing for this species with 241.126 and 162.521 tons per hectare production and biomass, respectively.

Arasbaran forest is one of the most important and valuable economic and tourism region. Ecotourism development in these forests requires comprehensive and detailed plans to consider all aspects of ecotourism development and maintain the sustainability of the ecosystem to be managed. This project aimed at considering all these merits needed for an appropriate method. In order to achieve a pre-defined process, the analytic network process method was used. The results of rating the control criteria showed that economic benefits with weight 0.26 are the most important criterion in the development of ecotourism in the study area followed by the economic opportunities and environmental costs with weights 0.205 and 0.142, respectively. The benefits of socio-cultural, environmental risks, opportunities, socio-cultural, environmental opportunities, and economic risks, the risks of socio-cultural, environmental benefits, environmental benefits, economic costs and expenses socio-cultural with weight of 0.088, 0.078, 0.069, 0.064, 0.025, 0.0194, 0.0189, 0.016, and 0.0126 were the subsequent priorities. The results of a comprehensive review of the development of ecotourism showed that ecotourism development can have significant environmental costs and opportunities in Arasbaran region that should be considered in its development management.

In this study, the effect of forest conversion to pasture and agricultural lands on some soil physicochemical and biological characteristics was evaluated in Piranshahr, Pardanan region. Soil physicochemical properties including texture, pH, EC, CaCO3, available nutrients (potassium, phosphorus, sodium, calcium and magnesium) were measured. Some biological characteristics such as microbial biomass carbon (MBC), carbon availability index (CAI), basal respiration (BR), subestrat induced respiration (SIR), metabolic quotient (qCO2), and the ratio of microbial biomass carbon to total organic carbon (Cmic/Corg) were assessed in soil samples. The results showed that clay content in agricultural land was 27% higher than that of forest ecosystem, while the sand content in the cultivated soils decreased by 30% compared to forest. Calcium content in the agronomic land increased (23%) compared to forest. The changes of forest to agronomic and orchard systems reduced BR by 18% to 38%. SIR of forest lands was significantly higher than the agricultural land-uses as SIR in forest about 1.72 fold higher than orchard and agronomic land-use. Therefore, it could be concluded that land-use change and cultivation operations in long-time causes a decline in soil quality.

Forest soil conservation as a production base during the harvesting and skidding operations is necessary, until the amounts of damage and recovery time of soil characteristics after the operation are minimized. This research was carried out in two districts; Patom and Namkhaneh of Forest Kheyrud in order to assess the environmental impact of slope, traffic and rutting location on soil physical properties and recovery them over 20 years compared with the controls. Fourabandoned skid trails were selected in downward direction and different ages and in each of these skid trails, three traffic classes and in each traffic class, two slope classes were specified. For measuring the soil moisture, sample plots of 10×4 m were located in the treatments. The results showed that in 15-20 year skid trail, soil moisture in slope, traffic and rutting location were not significantly different with control area, but the values ​​were still higher than the control area. Over 20 years of skidding operations, soil moisture was 9.7% lower than control area. However, these differences were not statistically significant. The results indicated that with increasing abandoned age of skid trails, the soil moisture tend to have more recovery rate.

The oak charcoal disease is an agent oak decline in forests of Iran, but there is no accurate information about risks and its threats. Therefore, in order to evaluate the relationship between severity of disease and host characteristics (diameter at breast height, crown position and trunk length), 385 oaks (Quercus castaneifolia) were considered by using pointcentered quarter method in Qoruq Forest Park. These oak trees were grouped in five levels based on the health status (healthy, low, moderate, severe and declines). For data analysis, Poisson regression, one-way ANOVA and Kruskal-Wallis and Duncan's test were applied by using R statistical software. The results showed that severity of disease had a significant relationship with diameter at breast height and crown position but the effect of trunk length was not significant. The Poisson regression analysis results showed that by increasing exp=(0.7)= 2.013 cm in diameter, it is expected the damage grade level rises one degree. Furthermore, the highest percentage of disease incidence and severity had occurred in the trees with a diameter greater than 35 cm and with middle crown position. In general, it can be concluded that the individual characteristics of trees can be influential factors in the severity and epidemic of the charcoal disease in oak trees.The development of epidemic models needs to better understanding of how the properties of the host influence the severity and spread of charcoal disease in long-term course of the disease.

This study is presented the recreation value for the Naharkhoran’s natural forest park of Gorgan city that is one of the best forest parks for recreation in country. For estimating of recreation value in this place, Contingent Valuation Method and Dichotomous Choice questionnaire were used. The population of the park visitors was determined during all seasons of in 2013 and based on Cochran formula 294 questionnaires was completed. For measuring willingness to pay of visitors Logit model was used to gain park benefits and model parameters were estimated base on the maximum likelihood method. The results showed that the willingness to pay had a positive relation with income and education level but had a negative relation with age, residency status, crossed distance and offered price. Variables such as family size, length of stay in the park and number of visitors had no significant effect on WTP. Based on these results the average of the willingness to pay for each person is 10450 Rials to visit this park and for a year willingness to pay each family is estimated about 117144 Rials. Total value of annual recreation was 21,945 million Rials (about $ 686,424 America dollars) and annual recreation value per acre is determined 35395161 Rials (1107 America dollars) for this park.

Planning, organizing, monitoring and controlling, leadership, evaluation and decision-making will not be possible and effective without communication. Nowadays, organizational relationships have become a complex and important research issue through progress of science and technology. This research tried to analyze the inter-organizational relationships related to natural resources in 5th Development Plan by using Network Analysis Method, Visone and NetDraw Softwares in order to investigate the legal and institutional status of natural resources. The results showed that the legal and institutional status of organizations involving in natural resources issue is not the same. Also high status of executive organizations and state in inter-organizational relationship networks, despite of involving 141 formal organizations in law, has caused different interpretation of the duties and organizational relationships. So, it is necessary to investigate the legal and institutional status of natural resources in former laws and policy document plans and evaluate the qualitative and quantitative characteristics of natural resources before final codification of 6th Development Plan.

Since N-tree sampling methods produce biased estimate, bias evaluation should be applied to N-tree estimator. The purpose of this study is to assess the N tree distance sampling method bias with modified estimator Kleinn and Vilcko in estimating number per hectare and canopy cover in Zagros forests. For this purpose, 6-10 trees from real forest map were tested with full inventories. For comparing the results of characteristics in different trees in N-tree method with full inventories, ANOVA was used. Evaluation of N tree distance sampling method was done by using accuracy criterion and standard error of mean. Bias was also evaluated via one-sample t-test and relative bias. Results showed that in estimating number per hectare and canopy cover, there is no significant difference between tree numbers with full inventory. Bias test for six and seven trees per hectare was significant, but it was not significant for eight, nine and 10 trees. Canopy cover for all tree numbers showed no significant difference. So, in order to achieve a maximum accuracy (minimum bias), at least eight trees within sample plot should be measured. Finally, this study implies that in forests with lower density and cluster pattern, bias change in N tree distance method does not follow a predictable decreasing pattern.

Increasing use of fossil fuels has increased the atmospheric carbon dioxide concentrations. On the other hand, carbon dioxide is one of the most important factors for plant growth. Thus, the knowledge of plant response to these changes is very important. The aim of the present study was to evaluate the impact of increased carbon dioxide on some morphological and physiological traits of Cupressus sempervirens under greenhouse conditions. Levels of carbon dioxide concentrations included 450 (as control), 750 and 1100 ppm in a completely randomized design with three replicates was used. Three-year-old seedlings were treated for two months. The results showed that carbon dioxide concentration (750 ppm) increased the amount of proline to more than six times and in the concentration of 1100 ppm increased to more than twice compared to the control. Concentration of 750 ppm increased the amount of nitrogen and also had the greatest impact on the diameter of the collar. Similarly, the concentration of 1100 ppm increased significantly plant height and shoot fresh weight.