Iranian Journal of Forest and Poplar Research
Year:2020 | Volume:28 | Issue:3 (81)|Papers Count:8

Hyrcanian forests are rare and unique ecosystems and their sustainability is essential. Gaps, as part of a general process, help to establish and stabilize the structure of the Hyrcanian forests and the dynamism of its society. This study seeks to identify possible differences in the gap characteristics in the two managed and intact compartments. For this purpose, compartments No. 114 (intact) and No. 115 (managed) from district one of Livan-Banafshtapeh forestry plan in Golestan province of Iran were selected to compare some gap characteristics (gap fraction, distribution of gap sizes, number of gaps per hectare and status of gapmaker trees). In these compartments, all gaps>100 m 2 caused by mortality of at least one tree with remnants of the gapmaker or detectable tree stumps, were identified and recorded. The results showed that the gap fraction in the intact and managed compartments was 10. 7% and 6. 3%, respectively. The average number of gaps varied from 1. 4 ha-1 in the managed to 2. 9 ha-1 in the intact compartment. The spatial pattern of gaps was randomly spaced up to a distance of 30 (managed) and 40 (intact) meters and then reached the cluster pattern. The differences between the characteristics in the two compartments were not statistically significant and management did not have a significant effect on these variables. However, no significant differences between the two compartments were due to the low harvest intensity in the managed compartment. The biodiversity of Hyrcanian forests must always be taken into account so that it is not endangered by mismanagement; otherwise irreparable effects on the ecosystem of the managed compartment may occur.

With the aim of identifying the dynamism of the Hyrcanian forests, four reserve compartments were selected in three provinces of Gilan, Mazandaran, and Golestan. In each reserve stand, three plots of one hectare (12 plots in total) were laid out in the initial, optimal, and decay development stages. The first inventory (structural study) was performed in 2008 and in the present study, data were collected again in 2018. All trees with a diameter at breast height larger than 7. 5 cm were measured. Based on the results, the mean number of trees naturally removed in the initial, optimal, and decay stages were 78, 48, and 31 per ha (21. 1, 16, and 12. 6%), respectively. The increase in the average mean diameter of the stands in the initial, optimal, and decay stand was increased in the amount of 3. 2, 4. 5, and 3. 75 cm, respectively. Also, the maximum volume increment within the period was calculated 101 m 3-1 ha in the optimal stage. All of the studied stands were placed in the large sizetimber in the structured triangle. Which indicates that they are far from theirregular structure. Over the ten-yearperiod, all stands, except the initial stage in Haftkhal, showed a light displacement in the triangle structure. Accordingly, periodic monitoring and data collection of permanent plots are one of the basic principles of stand conservation and improvement. Recognizing changes in structure over time is the first step in understanding the dynamics of development stages in stands which facilitates close to nature forest management.

The aim of this study is to investigate the effects of the port on vegetative and reproductive characteristics of grey mangrove (Avicennia marina (Forssk. ) Vierh. ) in two regions of Khamir and Khor-e-Azini. For this purpose, two sites adjacent to the port and control were selected in each region. For the study, two three-hectare stands were selected adjacent to the port and control sites and three 300-meter transects, 50meter apart from each other were selected using a random-systematic sampling method in each stand. Further, three plots (10×10 m 2 ) were selected along the transects and measured the vegetative and reproductive characteristics of A. marina. For trees higher than one meter and the datawere compared using T-test statistical analysis. Results showed that, in the control site in Khour-e-Azini port, the vitality of trees, the number of aerial roots and seedlings were significantly higher than those adjacent to the port but no significant differences were observed in other vegetative characteristics of grey mangrove including height, crown length and crown area in the two sites. Further, in the control site in Khamir port, the vitality of trees and crown area were significantly higher than those adjacent to the port but no significant differences were observed in other vegetative characteristics of grey mangrove at the two control and adjacent to the port sites. Generally, results showed that, with distance from the port, control stands have had better vegetative and vitality. Therefore, it is recommended in order to decrease the negative effects of human structures onmangrove forests, in addition to this research, other comprehensive researches should be done to specify the location of human structures more sensitive according to basic data.

One of the most prominent issues indicating the future quality and quantity of natural forest ecosystems is spatial pattern and distribution of disturbances consequences manifested as canopy gaps (CGs). The main purpose of this study was to illustrate the CGs distribution pattern in one of the Hyrcanian mixed-beech (Fagus orientalis Lipsky) forests, so-called preserved Glandroud forests. All CGs areas were measured based on full callipering on the basis of the radius method, and the coordinate of each CG was recorded in the forest. The univariate Ripley’ s L-function, mark correlation function (MCF), and density function (DC) in turns were used for analyzing the spatial patterns, size correlation, and frequency of the CGs distribution at the observation scale. Furthermore, the statistical significance of all ordination analyses was tested by the Monte Carlo permutation method. The results showed that the frequency of small gaps (0-2 R), medium gaps (2-5 R), and in turns were almost 32%, 49% in the study forest. Only the small CGs distribution was clustered at a specified distance of 14– 20 meters, though the other CGs size classes were completely randomly distributed in the forest. Integrating whole CGs size classes on the basis of Ripley’ s L-function showed that the CGs spatial pattern in the studied forest was clustered at a distance of 40 m. According to the mark correlation function (MCF) and density correlation (DC) analyses, there in turns were found that the location and number of size classes in each aggregation were totally significantly independent and random based on the specific distance in the forest. Pertaining to these results, it is possible to introduce mosaics consisting of forest stands which may include specified tree stands with various tree species composition, different developmental stages, and structures in the forest. Therefore, each mosaic can be a base area for monitoring disturbances consequences and implementing optimum managements.

The degree of soil cohesion investigation through the presence of roots is one of the important criteria in soil reinforcement studies. In this study, the investigation and comparison of the degree of soil cohesion have been carried out using two models of WWM and FBM. For this purpose, seven hornbeam (Carpinus betulus L. ) trees were selected in each three sites of chalos sarcheshme forest, series one. Then profile trenching method was used to analyze and compare root distribution and standard instron device have been measured tensile strength, respectively. The root area ratio (RAR) has decreased with increasing depth, and the maximum value of RAR in the three sites is seen at about 40 cm from the beginning, and the maximum depth of rooting is 60 cm. The results confirmed that there was a power law relationship between root diameter and tensile strength. The minimum and maximum tensile strength was estimated at 11. 52-323. 42, 6. 89-318. 79 and 6. 91-312. 66 MPa, in diameter range of 0. 59. 45, 0. 56-9. 21, 0. 45-9. 32 in the first, second and third site, respectively. In all three sites, the amount of soil cohesion through the presence of roots using the WWM model was 4. 0461. 37, 5. 7-53. 18, 4. 6-46. 66 kpa and in FBM model the root cohesion in all depth was 1. 2227. 48, 1. 87-24. 22, 1. 85-19. 04 kpa in the first, second and third site, respectively. Comparison of these two models increases our knowledge of the biomechanical features of the hornbeam species and more accurately determines the amount of soil reinforcement to be used in the future in the management of natural phenomena such as landslides.

The present study was conducted with the aim of mass production of seedlings of Populus deltoides Marsh. and P. euramericana (Dode) and to investigate the vegetative yield of the produced seedlings. In the first phase of the study, the collected seeds from the poplar collection of Chamestan Forest and Rangeland Research Station were sown in two treatments of pure field soil and soil mixed with sand, and three seed densities in three replications. Then, the number, dimensions and some morphological characteristics of the produced seedlings were investigated. In the second phase of the study, 12 genotypes were selected from the offspring of each of the two species. Sufficient cuttings were obtained from them and planted with cuttings of mother trees in three replications. Their vegetative characteristics were also recorded and analyzed. The results of the first stage showed that the range of changes in diameter, height, number of leaves, leaf length, survival percentage and percentage of seedlings longer than one meter in P. euramericana 92/40 seedlings was significantly higher than P. deltoides 69/55 seedlings. In terms of diameter, height and percentage of seedlings higher than one meter, the pure field soil was significantly superior to the mixed soil. Survival for densities of 50, 100 and 200 seeds per square meter was 32. 8%, 19. 8% and 10. 25%, respectively. The results of the second stage showed that the height and diameter of the mother bases were less than the offspring. The selected genotypes of this study include genotypes 10, 12 and 2 from the offspring of P. deltoides 69/55 and genotype three from the offspring of P. euramericana 92/40 which can be introduced to the implementation section for spacing cultivation experiments, stress resistance study and development of wood cultivation.

Felling operations in poplar plantations in Iran usually is performed with a chainsaw and by cutting workers. In connection with such dynamic work with repetitive work components, it is necessary to pay attention to the possible pressure on the musculoskeletal system of the workers, the evaluation of the work posture, and the calculation of risk index. To achieve the goals of the study, the Nordic questionnaire was used to study musculoskeletal problems in 9 felling workers in a poplar plantation in the Shanderman region of Guilan province. In the next stage images related to the evaluation of workers' postures during a 4-hour felling operation recorded by a video camera analyzed. The postural evaluation was performed by The Ovako Working Posture Analysing System (OWAS) method. In this study, 55 postures related to tree felling operations were obtained. The most discomfort of workers was related to the waist. The postural risk associated with felling operation was relatively high (I=251). Postural assessment of different felling work tasks indicated that the highest risk was incurred during back-cut (I=313), under-cut (I=303), delimbing (I=295), and bucking (I=281) respectively. 56. 41 percent of categories need further assessment necessary soon and now. Back bent forward or backward, standing position and both knees bent, both hands below shoulder height and, force/load 10-20 kg (code: 2142) were the most important ergonomic problem in logging operations. These findings indicate the need to provide training solutions among felling workers. In this regard, appropriate training techniques and methods of tree felling and work safety are recommended.

The aim of this study is to investigate the quantitative changes in the biometric indices of Lebanon oak (Quercus libani Oliv. ) and gall oak (Q. infectoria Oliv. ) during pollarding process. In a part of the two pollarded strands in northern Zagros of Iran, in which three years had passed from its last pollarding, the name of woody species was recorded and diameter (dbh), total and crown heights, and two perpendicular crown diameters were measured before and after pollarding in a full callipering assessment of all trees (dbh ≥ 5 cm). The results showed that in the pollarding process, crown height and crown area of oak trees decreased on average 15. 73 and 30. 06%, respectively. In both studied species, the reduction of crown area is significantly more than the crown height. In terms of reduction in crown height and crown area, there was no significant difference between Q. infectoria and Q. libani trees. The most decrease in crown height (27. 99%) and crown area (44. 85%) indices on diameter classes are related to Q. infectoria trees belonging to the 35 cm diameter class and Q. libani trees belonging to the 55 cm diameter class, respectively. The results indicate a higher decrease in the crown area compares to the crown height of oak trees due to pollarding practice; therefore, it is necessary to partially compensate for this decrease in the crown area by leaving some branches during each pollarding operation, because preserving the canopy is very important for Zagros-forest ecosystems. The only way to conserve these resources is to create a participatory approach as part of the transitional forest policy.