مجله جنگل ایران
سال دوازدهم شماره 3 (پاییز 1399)

Persian honey locust(Gleditsia caspica Desf.) is an endemic tree in the northern forests of Iran and southeastern Azerbaijan, which has low seed germination because of water impermeability of seed. In this research, effects of hot water at 70 °C and 100 °C (5, 10, 15 and 20 minutes), dry heat at 60 °C, 80 °C and 100°C (15, 30 and 60 minutes) and sulphuric acid treatment at two concentrations of 70% and 98% (at immersions of 5, 20, 40 and 60 minutes) were studied on the characteristics of seed germination of this species. Experiment was carried out based on completely randomized design in three replicates. No germination was observed in the seeds treated with hot water (100 °C), dry heat and control, while the seeds treated with semi-hot water (70 °C), sulphuric acids of 70% (60 minutes) and 98% (20 and 40 minutes) obtained 20, 84 and 100 percent of germination, respectively. In general, hot water, warm water and dry heat are not good treatments for seed germination of Persian honey locust seed. It suggests that for seed dormancy breaking as well as seedling production of Persian honey locust,sulfuric acid 98% (with immersion of 20 or 40 m.) to be used.

This study was carried out to investigate the spatial variability of litter carbon storage and its sequestration in the soil layers in the forested area of Jahannama Park. First, 115 soil samples were taken from 0-15, 15-30, and 30-50 cm depths using the grid-transect sampling method. After the determination of the percentage of organic carbon, the geostatistical methods (simple kriging, ordinary kriging and inverse distance weighting methods) were used to investigate the spatial variability of carbon percentage in the non-sampled locations. The cross-validation method was used to evaluate the accuracy of the results using MARE, MBE, and RMSE statistical criteria. The results showed that the carbon content in the first two depths had a Gaussian variogram model and, in the third depth, was exponential. Nugget effect and spatial structure of carbon percentage in the first, second and third depths were 0.001%, 0.999%, 0.0045%, 0.966%, 0.0058%, and 0.956%, respectively, which shows the less nugget effect and good spatial structure of carbon in both the surface and the deep layers. Low estimation error showed that ordinary kriging was able to make the correct estimation for all of the depths. Considering the objectives of this study, in an area, about 36 hectares with a dense sampling network (115 soil profiles) with different tree stands, on average, 68.5 tons carbon sequestration per hectare has been estimated to a depth of 50 cm which is a total of 2470 tons of carbon sequestration in this area. The sampling strategy in this study to estimate the soil carbon sequestration in afforestation can be a good model for other similar areas.

The present study compares the performance of three statistical models including logistic regression, frequency ratio and maximum entropy in preparing the zoning map of landslide sensitivity on the watersheds of 24 and 25 (Malak-roud and Shen-roud) regions of Guilan province. For this purpose, all the roads of the two areas were survyed and the number of 844 landslides were detected. Then effective data layers on landslide formation were prepared and then zoning maps of the landslide sensitivity were extracted to the three methods. The results showed that the logistic regression model has an accuracy of 74.6 percent of the Area under ROC Curve in prediction of sensitive areas compared to the accuracy of 68.2 and 65.2 percent by the probabilistic frequency ratio model and Entropy model, respectively. Moreover, based on the logistic regression model, the distance and slope factors have the highest effect on the landslide of forest road trenches. According to this study, a total of 4.32 square kilometers (43.25%) of the landslide areas is categorized in very high and high susceptible groups which have occurred along 51.38 percent of the area. Despite the lack of consideration to superstructure conditions in the present study, a notable percentage of existing roads are exposed to the collapse of trenches and require adequate funding for repair operations. According to the logging ban as a new approach in forest utilization and lack of revenue regeneration of alternative conservation projects great dangers threaten the forest engineering installations and road structures.

Competition between trees has an impact on their structural features and it is very important to measure the competition index and determine the correlation with some of the characteristics of the trees. To conduct the research, circular sample plots (n = 24) with an area of ​​400 m 2 were established in a 150 × 100 m grid in the forest, Savadkoh-Mazandaran. Within each sample plot, frequency, height, crown diameter and diameter at breast height (dbh) for each tree were measured in the overstorey. The richness and diversity index of trees and competition index for each plot were calculated. The results showed that there was a significant difference between the values ​​of competition index for the three tree species. Competition index with height, dbh and crown diameter had significant positive correlation for all tree species, but negative significant correlation with height and H/D for beech and alder and also positive correlation for hornbeam. There was a negative significant correlation between beech competition index and tree richness index and a positive correlation between alder competition index and tree diversity index. With increasing altitude, competition index values ​​decreased only for hornbeam species. Significant differences were observed among the three tree species in terms of crown diameter, dbh, height and H/D ratio in stand. In general, regarding the relationship between some tree variables and the index of competition in the stand, this information can be used in the selection and application of silvicultural operations such as thinning and remarking in temperate Hyrcanian broadleaf forest.

Common yew (Taxus baccata L.) is classified as an Endangered (En) species and its distribution has been decreased as a long-lived species during last decades, indicating the need for protecting its habitats. In this research, the habitat suitability of common yew in the Arasbaran biosphere reserve, was explored. Using the Maximum Entropy (MaxEnt) approach and based on the presence locations (74 points) the suitable habitats were modelled. The predictor variables included in the model were slope, aspect, elevation, landform, land use, and climate. Results showed that 1.48% (1265 ha) of the Arasbaran biosphere reserve is suitable for Common Yew. Based on the habitat suitability map, common yew prefers the elevation 900-1700, slope 25-60%, northern aspect, rainfall 360-480 mm, the average temperature 8-13°C, Mediterranean climate, and forested areas with canopy cover > 50%. The suitable habitats for Common Yew are generally distributed in the Tazekand, Kalaleh, Ainehloo, Nooghdi and Balasang forest areas. The accuracy and the ability of predictions model was assessed great for this species based on the area under the curve (AUC= 0.996). Using the findings of this study we can specify suitable areas for yew’s plantation, and restore its habitat in Arasbaran in the future.

The aim of this study was to determine the possible difference in the amount of organic carbon and total nitrogen in the soil under the crown of tree species in a semi-arid forest at the level of a single tree. Also, the pattern of possible differences between these two main soil materials was observed in different size classes of trees and in top- and subsoil. For this purpose, 60 trees from four species of juniper (Juniperus excelsa), narrow-leafed ash (Fraxinus angustifolia), Brant's oak (Quercus brantii) and hawthorn (Crataegus azarolus) were randomly selected in a mixed stand of central Zagrosian forest that had been enclosd for over 30 years. The amounts of organic carbon and total nitrogen of topsoil (0-15 cm) and subsoil (15-50 cm) were measured and compared. The results showed that, first, both the amount of soil organic carbon and the total nitrogen from the samples beneath the tree crowns were higher than their corresponding values in soils outside the crowns. Second, only the amounts of soil organic carbon were affected by the species, and these values ranged from a minimum of 1.37% in topsoil and 0.52% in subsoil for hawthorn, to maximum values of 1.64 and 0.73 percent for Juniper in top- and subsoil, respectively. Third, the amount of total nitrogen in the soil with an average of 0.21 and 0.08 percent of dry weight in top- and subsoils, respectively were the same beneath the crowns of the four species. Fourth, the size of the trees only affected the amount of organic carbon and total nitrogen in the topsoil. This study showed that there is little difference in soil organic carbon and total nitrogen under the canopy of different tree species in a standard Zagros forest and therefore the whole stand may act as a mega-organism and has more or less homogeneous soil.

Estimation of forest aboveground biomass is important in regional carbon policies and sustainable forest management. Since forests are the largest carbon store, it is important to evaluate the forest biomass to estimate carbon storage and its impacts on climate change in global scale. Optical and active microwave remote sensing data both play important roles in forest biomass monitoring. Our aims in this research are biomass modeling and estimation using multilayer perceptron neural network in Gorazbon district, Kheyroud Forest in Mazandaran province. Estimation was performed using the Landsat and ALOS PALSAR dataset and also 201 ground sample plots in two years of 2007 and 2012. The capability of the ALOS PALSAR Global Mosaic product with 25 m resolution was also evaluated in biomass estimation. The effects of environmental factors such as slope and aspect were specifically evaluated on the accuracy of biomass estimation. Finally, the best model was presented in 2012 by ALOS PALSAR Global Mosaic product with R2= 0.83 and RMSE = 108.99 which has very little difference from other optical and radar images. According to the research results, newer sensors using up-to-date technology will deliver much better results compared to the previous generations. Of course, to ensure these results, it is necessary to conduct additional studies in this field as well.

Ignoring the spatial scale in understanding of environmental processes resulted in a vagueness in environment problems statement and incorrect decision-making in environment management. Because, connection between solutions and environmental problems in policy-making processes, require attention to suitable spatial scale of technical knowledge. Therefore in this study, focusing on descriptive-analytical approach, the role of spatial scale were surveyed in environmental policymaking. The results showed that despite the effort to understand the the environmental problems in international scale,governments focus more on environment and natural resources management in national scale. So, using of national scale is necessary for attainment to special methodological framework for solving the environment problems and transfer adequate solutions and understanding of technical knowledge to policy context. Hence, it could be suggested that providing and designing an environmental policymaking supermodel in state scale (national scale) can hemogenise its environmental macro-policies scale with scale of understanding of environmental problems. In other word, this supermodel is useful for connect technical knowledge outcomes to understanding of policymakers in national spatial scale.

The objective of this study was to measure and determine the allometric equation of leaf dry mass, specific leaf area and leaf area index of Rhizophora mucronata species located in Sirik city, Hormozgan province, Iran. In this study, in addition to the actual determination of the leaves, the specific leaf area and the leaf area index of Rhizophora mucronata trees were calculated using vegetative characteristics. Then, the correlation between different components, and their allometric equations were calculated. Determining the leaf area index was performed directly by collecting 88 leaves from 22 trees and weighing them and the mean leaf area, the canopy area ​​ and leaf dry mass were calculated through collecting one-eighth of the tree canopy and determining the fresh and dry weight. Correlation and model determination were determined using stepwise regression (P≤0.01). According to the results, the mean dry mass, specific leaf area and leaf area index were 3.33 kg/tree, 39.74 cm-2/g per tree and 0.76, respectively. The leaf area index, with two factors of leaf area and tree height, (correlation coefficient=0.82) explained 65% of the variations in the dependent variable. In determining the specific leaf area, only leaf area factor was introduced as the most effective factor in the equation and explained 56% of the variations. Results showed that tree factors, canopy area, leaf area and height can have key role in tree ecological indices (leaf dry mass, LAI and SLA) estimation and also in evaluation of mangrove stand changes and health.

Natural reconstruction of forest structure is one of the most important processes in the evolution of forest stands. In order to investigate the process of natural reconstruction of the structure in beech stands in Eshkevarat Roodsar region, three one-hectare sample plots with different histories of conservation, including low-term, middle-term and reference forest area were selected, and the most important stand structural characteristic and eleven structural quantification indices in 45 structural groups were evaluated using the distance measurment methods. The analysis of the stand structural changes was performed based on three groups of stand structural characteristic including the spatial pattern of the structure, heterogeneity in the dimensions of the trees and structural complexity. The diameter mean, Clark Evans, Berger-Parker and uniformangle indexes showed a significant difference between in the three areas. The increasing trend for Gini coefficient, diameter and height differentiation indices, along with the transfer of trees to higher diameter and height layers in protected area, indicates an increase in heterogeneity and formation of vertical structure in the forest. In conclusion, forest conservation in the traditional way and exclosure method in this area has led to the reconstruction of the stand structure. It is recommended to create a long-term exclosure (more than 60 years) along with close to nature silvicultual interventions for natural reconstruction in this areas.