رامین رحمانی

The leaf area index (LAI) is one of the structural indices of forests and a key variable in the state of forest ecosystems. This index is one of the major structural indices of forests that plays an important role in the processes of evaporation and transpiration and in monitoring the growth of trees. The role of LAI is very important in the changes in the structural quantitative characteristics of forest stands. There is a general relationship between the LAI and the quantitative characteristics of the mass. The leaf area of each tree can be estimated using allometric equations of quantitative characteristics. This research focuses on the effects of changes in the quantitative characteristics, such as tree density (n.ha-1), basal area (m2.ha-1), volume (m3.ha-1), mean height (m), mean diameter at breast height (DBH, cm), crown area (m2.ha-1), and crown volume (m3.ha-1) on the LAI and preparation of their allometric equations in the broadleaf forests of Golestan province.

To collect ground information on LAI, 227 circular sample plots with an area of 1000 m2 with a systematic sampling method and a 100 × 100 m grid were dismounted in five habitats from west to east (Kordkoy, Shasat Kalathe, Zarrin, Gol, Sorkhdari, and Loveh). In the center of each sample plot, the LAI was measured using a leaf harvesting trap with dimensions of 60 × 60 cm. The geographic center of each sample was recorded using a Differential Global Positioning System device. The species type, breast diameter greater than 12.5 cm, the height of trees, large diameter, and small crown diameter are measured, then as tree density (n.ha-1), basal area (m2.ha-1), volume (m3.ha-1), mean height (m), mean DBH (cm), crown area (m2.ha-1), and crown volume (m3.ha-1) located in each sample plot were calculated in each plot. To calculate the LAI, it is first necessary to measure the specific leaf area of all species in the study area. To calculate the LAI, 20 trees were separated from each tree in each habitat and five leaf samples were separated from each tree in four geographical directions. In total, more than 15,000 leaf samples were analyzed and scanned in five habitats. The area of each leaf was measured using ImageJ software. The wet and dry weight and surface area were measured simultaneously using a digital scale with an accuracy of 0.01 and then scanned with a high-resolution scanner. After scanning, the leaves were dried in an oven at 72 °C for 48 hours to obtain their dry weights. Non-linear rational function, Gaussian, hyperbolic, heat capacity, and exponential models were used to investigate the relationship between LAI and the structural characteristics of the stand.

The results of the analysis of descriptive statistics showed that the minimum, maximum, average, and standard deviation of the LAI were calculated for 227 samples (1.86, 13.45, 6.33, and 2.33), respectively. The results of the analysis of descriptive statistics also showed that the mean and standard deviation for the characteristics of volume (m3.ha-1), tree density (n.ha-1), basal area (m2.ha-1), crown area (m2.ha-1), crown volume (m3.ha-1), mean height (m), and mean DBH (cm) were respectively (96.96) 298 and 18.205), (24.05 and 12.82), (24.05 and 12.82), (51.148 and 54.155), (2.781 and 05.95), (41.36 and 9.97), and (25.81 and 4.93). The results of the relationships between the LAI and the quantitative characteristics of the volume (m3.ha-1), tree density (n.ha-1), basal area (m2.ha-1), crown area (m2.ha-1), crown volume (m3.ha-1), mean height (m), and mean DBH (cm) of the coefficients of determination showed (36-0.96) R2 = 0.00 with a mean square error of MSE = 0.48-2.06. Among the investigated quantitative traits, the average height, crown volume per hectare, and volume per hectare gained the highest R2 values (0.36-0.96) and the MSE (0.48-2.06) with Gaussian, Richard, and heat capacity allometric models, and the tree density trait (n.ha-1). The lowest R2 (0.36) and MSE (2.06) in the study of LAI were obtained with the Gaussian model. The results also showed large changes in the LAI for the crown volume trait up to 400 (m3.ha-1), followed by a uniform trend. For the average height of up to 40 (m), many changes were found in the LAI. For the volume trait (m3.ha-1), the LAI increased up to 800 (m3.ha-1) and then showed a uniform and even downward trend until 1200 (m3.ha-1).

The results of this research demonstrate that the three quantitative traits, viz. crown volume (m3.ha-1), mean height, and volume (m3.ha-1), have the greatest effect on the changes in the LAI. Thus, these three traits can better explain the LAI. The LAI can estimated using the three crown volume (m3.ha-1), mean height, and volume (m3.ha-1) traits. Based on these three traits, the LAI can explained on a large scale, and the estimated results can be used in climate models and the development of appropriate climate change policies.

Structure of forest ecosystems undergoes changes in the temporal and spatial scale that this changes cause development. Development process is very slow and takes place in long term in this unites. For evaluation of this changes are used density, canopy and mixing amount. Structural attributes, show the ecological diversity and sustainability of forest ecosystems well. We conducted this study to compare changes in the structural attributes of density and canopy with diversity of tree species between different stories, as well the relationship these variables with diversity indices, between two periods of inventory in fixed location and natural environment where external factors have the least proportion in stand development.

Permanent sample plot with an area of 16 ha is located at 770-920 elevation and Northwest and west directions in 32 compartment, district one Shast Kalateh forest. Inventory was carried out using 100 % sampling method with 1 ha sample plot. Differences from 2003 to 2023 quantitative attributes of density, canopy and biodiversity indices were measured with standard method and compared through ANOVA in different stories.

The density of trees in the investigated plot reduced from 306.31 to 275.44 trees per hectare in 2003 and 2023. Only, Beech (Fagus orientalis Lipsky) species increased in density during this period. The highest frequency of tree individual belonged to under story in 2003, but in 2023, it was transferred to middle story. The average crown coverage percentage reduced from 86% to 70%. The highest amount of canopy percentage assigned to middle and upper stories. The average of Shannon's heterogeneity in 2003 in three story was (1.32, 1.29, 0.72) and in 2023 (0.49, 0.53, 0.58) respectively. The Shannon Wiener diversity index provided a better judgment of the species diversity in the investigated plot than other indices.

The investigated plot is a Mixed beech stand in which Beech shade tolerance species is dominant. Mixing more tree species while increasing diversity at different levels will bring stability of forest ecosystems. The results of this research showed that the indices of species diversity are only one of the methods of interpretation and evaluation of forest ecosystems and other characteristics should also be paid attention to. The periodic monitoring of this indices correctly shows changes trend of forest ecosystem. The results of used indices can be basis of evaluation and comparison with similar forest. Keywords: Structure dynamics, Diversity, Tree strata, Mixed beech stand

Pain and disabilities in the musculoskeletal system can lead to reduced productivity and job turnover. This research aims to study the role of posture, as well as individual and organizational factors, in causing musculoskeletal pain and disabilities among urban bus drivers.

In this cross-sectional study, 130 bus drivers from Hamadan city were investigated using a census method. Standardized questionnaires were employed to assess musculoskeletal disorders and job satisfaction. Additionally, posture evaluation was conducted using the RULA. Finally, common statistical methods were applied in SPSS version 24 for data analysis.

The highest and lowest frequencies of pain in the past year were related to the back (94 people, equal to 72.3%) and ankle (5 people, equal to 3.8%), respectively. The average body posture score for the left and right sides of the drivers’ bodies was 5.85±1.14 and 6.06±1.05, respectively. The intensity of pain and disability in the musculoskeletal system had a direct relationship with age, work history, body mass index, and posture score, and an inverse relationship with the average number of hours of sleep. Additionally, the type of work shift and job satisfaction were directly related to pain and disability.

severity of pain and disability in the musculoskeletal system was associated with the drivers’ posture score, age, work experience, body mass index, exercise habits, shift work, hours of sleep, and level of job satisfaction. The findings from this study can inform interventions aimed at enhancing the musculoskeletal health of bus drivers.

Musculoskeletal disorders are among the common problems in most work environments and work ability is considered a factor affecting the performance and productivity of employees. In the present study, the status of these two components and their relationship with each other in the staff working in the operating room were investigated.

The current cross-sectional study was conducted in the winter of 2023. In this research, 96 employees working in the operating rooms of government hospitals in Hamadan, Iran were enrolled by census sampling method based on the inclusion criteria. The data were collected through the Nordic standard questionnaire and the work ability index questionnaire. The collected data were analyzed in SPSS software (version 24) at two levels of descriptive (frequency, mean, and standard deviation) and inferential (t-test) statistics.

In this study, 4 (4.2%) of the participants had one musculoskeletal disorder and the remaining 91 personnel (95.8%) had more than one disorder in their musculoskeletal systems. Average work ability index was 42.3±04.91. The results of the independent t-test showed that the work ability index among people with pain in the neck (P=0.003), shoulders (P=0.001), elbows (P=0.038), back (P=0.011), knees (P=0.001), and legs (P=0.002) were less than those without pain in these organs.

Results indicated the need to pay more attention to the implementation of ergonomic work environment and management interventions to reduce the prevalence of musculoskeletal disorders and thereby increase the efficiency and effectiveness of personnel.

The relationship between soil invertebrates and silvicultural practices in the oriental beech forests (Fagus orientalis Lipsky), a widespread forest tree in the Hyrcanian region, is not fully understood. The diversity of soil invertebrates is a crucial variable in the ecological evaluation of managed forests. Therefore, this study aims to assess the impacts of silvicultural practices on soil invertebrates, which is essential for sustainable forest management. The soil invertebrates studied included Earthworms, Winged insects, Aranea, Pseudoscorpions, Collembola, Protura, Diplura, Diplopoda, Chilopoda, Symphyla, Pauropoda, and Isopoda. The objective was to compare the abundance and diversity of soil invertebrates between two managed (No. 8) and unmanaged (No. 36) compartments in the Haftkhal forests of Neka city, Mazandaran province.

Soil sampling was conducted in 131 ha of the studied forests using a regular random method with grid dimensions of 150 × 200 m. A cylindrical device with a cross-sectional area of 81 cm² and a depth of 10 cm was used. Twenty and thirty sampling plots were obtained in managed (No. 8) and unmanaged (No. 36) compartments, respectively. The average abundance and the average number of soil invertebrate groups per square meter were determined. Additionally, Shannon-Wiener and Simpson Indices were used to calculate soil invertebrates’ diversity, while Margalef and Sheldon indices were used to determine species richness and evenness, respectively.

The results showed that the averages of total abundance and the number of soil invertebrate groups per square meter in the managed forest (117278.70 and 7.31) had a slight decrease compared to the unmanaged forest (120167.77 and 7.62). Also, the diversity averages based on Shannon-Wiener and Simpson indices, along with the Margalef richness of soil invertebrates in the managed forest (1.890, 0.834, and 1.770), had a slight decrease compared to the unmanaged forest (1.928, 0.840, and 1.862). On the other hand, the average Sheldon evenness of soil invertebrates in the managed forest (0.935) had a slight increase compared to the unmanaged forest (0.924). Overall, road construction and exploitation operations during the two periods of the forestry plan implementation created scattered changes in the managed compartment, leading to a slight decrease in the abundance, richness, and diversity of soil invertebrates. However, the values of all the investigated variables between managed and unmanaged forests were not statistically significant (p=0.05).

This research demonstrated that forest management, utilizing the forestry method of uneven-aged mixed forest and the silviculture system of single-selection, has not significantly reduced the abundance and diversity indices of soil invertebrates in the managed forest compared to the unmanaged forest.

Leaf area index (LAI) is one of the most important structural characteristics of forest ecosystems, which has a great impact on changes in energy, weather, atmospheric and gas functional models. This index provides managers and planners with a lot of information related to the amount of photosynthesis, evaporation and transpiration and fertility of different habitats. Physiographic factors also (elevation above sea level, aspect and slope) play an important role in the global LAI. In this research, the changes of the LAI in different classes of elevation, aspect and slope are compared and evaluated.

n this study, 230 square-shaped sample plots with an area of 1000 square meters were used to collect the ground information of the leaf surface index using a systematic sampling method with a sampling grid of 100 x 100 meters in five sites (Kordkoy, Shast Kalateh, Zarrin Gol, Sokhdari and Loveh). In the center of each plot, a leaf harvesting trap with dimensions of 60 x 60 cm was used to measure the LAI. First, height maps from elevation, aspect and slope were also prepared and their values were extracted. Then the LAI was compared and analyzed in different classes of elevation, aspect and slope using Duncan's and independent t tests.

The results of LAI showed that the elevation of LAI in Kordkoy vegetation was measured with 8.91 and the lowest level of LAI was measured with 5.10 in Zarrin Gol vegetation. The results of analysis of variance showed that there is a significant difference between the LAI in different classes of elevation above sea level in the entire study area. And with the increase in elevation above sea level to about 1300 meters, the LAI increases and after that, the LAI has little changes. The significant results of Duncan's test and independent t-test showed that there is no significant difference between the LAI of each site in different classes of elevation above sea level, aspect and slope, except for Kurdkoy site.

In general, in this study, the elevation compared to the slope and aspect was raised as a very important factor for investigating LAI. Investigating the effect of physiographic factors such as elevation above sea level, slope and aspect on the LAI and monitoring its changes in order to know the formulation of appropriate policies to reduce the effects of climate change and global warming and in sustainable management is of great importance.

In work environments, job stress is the main factor that can break the control of employees and provide the context for the occurrence of aggression in employees. For this reason, this study investigated the role of the effort-reward imbalance model in the occurrence of bullying in the workplace.

This study was descriptive-analytical in nature. In this research, to measure the variables, two self-report questionnaires, the effort-reward imbalance scale and the negative actions questionnaire, were used.  The research population was employees of one of the process industries, and 202 people were included in the study using the census method. Analyses were performed using SPSS 18 software, Pearson’s correlation coefficient, and linear regression.

 The total number of participants in the study was 202. The average age and work experience of the participants in this study were 40.13±9.32 and 15.9±9.50 years, respectively. Among the participants, 72.8% were male and 86.1% were married. In terms of educational status, 10.9% had an associate's degree, 81.2% had a bachelor's degree, and the rest had a master's degree or higher. About three-fourths of the people were officially employed, and the rest were working on a contract basis. Based on the results of the multivariate regression model, among the variables investigated in this study, effort-reward imbalance and extreme commitment were able to significantly predict the changes in the bullying score (P<0.001).

Employees who feel imbalanced between inputs and outputs in the job, as well as employees who have the characteristic of extreme commitment, are more likely to engage in negative behaviors in the form of bullying in the workplace.

Bus drivers are exposed to harmful agents such as noise and vibration which may led to increasing the level of job stress among them. The aim of this study was to evaluation of job stress among urban bus drivers with respect to daily noise and vibration exposures.

This cross-sectional study carried out with participation of 103 urban bus drivers in Hamadan, 2020. The drivers' exposure to noise and vibration were measured using Svan 104 and Svan 106, respectively. The job stress was measured through Phillippe L. Rice questionnaire. Data analysis preformed using SPSS 24 and the significant levels of 0.05.

The mean exposure of drivers with noise was 79.50±3.51 dB. Their exposure with whole body vibrations (WBV) and hand-arm vibrations (HAV) were 0.62±0.16 and 0.44±0.06 m/s2, respectively. Most drivers (87.4 percent) had sever job stress. A significant positive correlation was observed between noise and job stress; whereas, there was no significant correlation between WBV and HAV with job stress. 

Regarding high prevalence of severe job stress among bus drivers and the positive correlation between noise and job stress, it is highly recommended that the noise exposure were subside through periodic services and maintenance as well as applying new buses instead of the old ones.

The Quality of Working Life (QWL) is one of the most influence organizational factor and taxi is the most common public transport system in small cities. The present study aimed to evaluating the QWL and its associated factors among urban taxi drivers.

This descriptive analytical study done with participating 176 urban taxi drivers working in one of the southern cities of West Azerbaijan province. Using census method individuals including in the study considering the inclusion criteria and answered a two-part questionnaire consisting of demographic characteristics and Walton’s QWL questions. Finally, data were analyzed using SPSS 24 software at a significant level of 0.05. 

QWL evaluating showed that 18 drivers were at low level, 151 drivers were at moderate level and 7 drivers were at high level. Week and positive correlations were observed between QWL and both age and work experience. Some individual characteristics were found to be significantly associated with some aspects of QWL; while, the mean score of QWL was not significantly associated with individual characteristics such as education level, marital status, and body mass index.

The status of QWL was low and moderate in most drivers. In general, the mean score of QWL was not associated with individual characteristics such as educational level, marital status, and body mass index. More comprehensive studies are needed in this regard.

The aim of this study was to develop a mixed-effects model and compare it with nonlinear models for estimating the heights of velvet maple and ironwood trees in the uneven-aged, mixed Shast-kalateh forests of Gorgan. We applied a systematic sampling method to collect field data within a 150×200 m network, comprising of 308 circular sample plots, and measured the height, diameter at breast height (DBH), and tree species in each plot. Model fitting was done in two stages: In the first stage, we used a fixed-effect approach to select candidate models, where height was the dependent variable and DBH was the independent variable. In the second stage, the dominant height, mean DBH, basal area, basal area of trees larger than the desired tree, tree density, and volume of trees were refitted using a mixed-effect approach. We used adjusted coefficient of determination and root mean square error to assess the models. The results of fitting nonlinear models for velvet maple species showed that the Curtis and Michailief models with R2 values of 0.74 and the lowest RMSE values of 3.43 and 3.24, respectively, were the best models. For ironwood trees, the Nassland and Michailoff models with R2 values of 0.42 and the RMSE values of 2.92 and 2.91 m were selected as the best models. The results of fitting the nonlinear mixed-effect model showed that compared to the nonlinear models, the R2 values for velvet maple and ironwood species increased by 20% and 23%, respectively, and the RMSE improved to 1.75 m for velvet maple and 0.45 m for ironwood.

Traffic accidents are one of the most important challenges metropolises face, which impose significant costs on them every year. This study was conducted to determine the prevalence of accidents and the factors affecting them among city taxi drivers in Kermanshah, Iran.

In this descriptive-analytical cross-sectional study, 320 male urban taxi drivers in Kermanshah were investigated in 2018. The required data were collected using a multi-part questionnaire including demographic and occupational characteristics, a visual analog scale for fatigue, and the Pittsburgh Sleep Quality Index. To analyze the data, non-parametric statistical tests and logistic regression models were employed by using SPSS software (version 25).

The frequency of accidents among urban taxi drivers of Kermanshah was 38.3% (n=123). Significant differences were observed in the variables of work experience, fatigue level, and smoking among drivers with and without accidents (P<0.05). Based on logistic regression, smoking (odds ratio: 2.68 and 95% confidence interval: 1.66-4.33) and one unit increase in the fatigue level (odds ratio: 1.01 and 95% confidence interval: 1.00-0.1-02) were significantly associated with an increased chance of the accident in the drivers.

Due to the relatively high prevalence of accidents among urban taxi drivers, it is necessary to design and prioritize comprehensive programs to identify and control the factors affecting accidents in this group of drivers.

Canopy gap delineation is essential for achieving a better comprehension of forest structure. This study aims to (a) extract canopy gaps using UAV data and (b) compare the performance of different canopy gap extraction methods in a managed stand in the northeast of Iran. A canopy height model (CHM) was produced by subtracting LIDAR digital terrain model from the UAV digital surface model. CHM classification performs to extract gaps by thresholding CHM (fixed height and CHM slope and relative height thresholds) and object-based classification on the UAV CHM and orthophoto. Ground truth is produced in the point and polygon forms through field measurements and visual interpretation of the UAV orthophoto. The geometry of the canopy gaps (Area, perimeter, and shape complexity) was calculated. Finally, the point and polygon base accuracy of delineated gaps assess for each of the methods. Point accuracy assessment suggests that 60% CHM slope produces the highest overall accuracy and Kappa coefficient of 91.7% and 0.874, respectively. About area accuracy assessment, the best match between delineated gaps and ground truth polygons was achieved by using relative height and 60% CHM slope thresholds. The lowest mean errors of GSCI produced by 70% CHM slope (0.15). Moreover, object-based classification showed the lowest mean error of area (33.76 m2) and perimeter (16.80 m). In conclusion, while area accuracy is considered the best fit of the delineated gap's geometry is gained by the object-based classification.

The rate of litter decomposition is influenced by various factors such as climatic conditions, litter quality and population of decomposers. Changes in precipitation patterns and increasing temperatures are the most important consequences of the climate change may change the decomposition rate of leaf litter. Hence, the present study aimed to simulate the effect of throughfall exclusion and increasing temperature on the process of hornbeam and oak leaf litter decomposition in the oak-hornbeam stand. For this purpose, four treatments were considered including two combined treatments consist of 25 and 50% throughfall exclusion and increasing temperature, warming and the control treatment (natural conditions). The hornbeam and oak leaf litter decomposition rate were studied using litter bags for 200 days. The average soil temperature of the treatments during the study period was 0.2-0.3 °C more than the control treatment, which resulted in a decrease in soil moisture content 13%. The combine effect of increasing temperature and decreasing soil water content cause a significant increase in the leaf litter decomposition rate of hornbeam, especially in the treatments of 25 and 50% compared to the control. The decomposition rate of the control treatment was decreased over time; while the decomposition rate of oak increased in the treatment of 25%. The results showed that changing in the climate conditions (i.e., increasing the temperature and decreasing the precipitation) will significantly change the rate of litter decomposition of thermophilic species (oak). It will lead to increase the rate of nutrient exchange in the forest soil ecosystem. Therefore, in forests with fertile soil, it is possible to shorten the exploitation period‎.

The impact of logging and tree harvesting on the ecological function and the future of Hyrcanian forests structure is a continuing debate topic. The information is currently available does not support firm conclusions about the impact of forest harvest intensity on forest structure and biomass. The present study aims to evaluate the effect of single-tree selection harvest intensity on biomass of hornbeam-Persian ironwood stand. For this purpose, information on all trees and dead trees were collected in 70 half-hectare plots. The 35 sample plots were in single-tree selection stands with three harvest intensities and the same sample plots were in control stand. Trees litter fall were measures from September to February and the storage of soil organic carbon was determined through organic carbon and bulk density. Then, tree biomass, litter biomass, dead tree biomass and total biomass were finally calculated. The results showed with increasing the rate of harvest intensity up to 13.5% the total biomass had rising trends, although harvest intensity had no significant effect on aboveground and belowground biomass and soil organic carbon. The aboveground biomass was higher in single-tree selection stand than control stand. The average of total biomass was 147 and 144 ton/ha in harvest and control hornbeam-Persian ironwood stands respectively and harvesting increased two percent of mean total biomass. The medium harvest intensity (3.6-9.5% of stand volume) was finally determined as appropriate selective logging intensity. The correspondence of litter biomass and dead tree biomass as bio indicator indicated that tree marking in the single-tree selection system was advisable.

Exposure to vibration is one of the occupational agents that causes a variety of health effects. The aim of this study was to determine the association between exposure to human vibration and the physical performance of mining drivers.

In the present study, 65 drivers working in one of the Iron Ore mines, were asked to complete the standard questionnaire for assessing the level of disability of the arm, shoulder and hand (DASH). Exposure to human vibration was measured using Svantek 106 vibrometer. Drivers' physical performance was assessed based on grip strength, Pegboard dexterity, and monofilament finger sensory tests. Data were analyzed using SPSS 21 software.

The average vibration acceleration whole body (WBV) and hand-arm (HAV) were 1.00±0.23 and 2.46±0.68 m/s2 respectively. There was a significant relationship between exposure to HAV and grip strength and hand dexterity (p <0.05). According to the DASH score, 56.9% of drivers had mild and 43.1% had moderate upper limb disability. The results of the multiple regression model with a coefficient of determination of 0.207 showed that the WBV in the presence of other predictor variables had a significant effect on DASH score (p<0.05).

In mining truck drivers, WBV exposure was higher and HAV exposure was lower than the national exposure limits. The results confirmed that WBV caused by mining trucks is the most important risk factor affecting the level of drivers' disability.

Canopy gaps are the most important environments for many species regenerations. Studying regeneration in natural and Man-made canopy gaps provides practical information to enhance the quantity and quality of tree species regeneration. This study aimed to investigate the relation between geometrical characteristics of canopy gaps with diversity and density of tree species regeneration in natural and Man-made canopy gaps.

Two 16 ha plots were selected with relatively similar site conditions in part of series one and two of Dr. Bahram-nia 's forestry plan, Shastkalateh, Gorgan. The position of 56 canopy gaps was recorded using a differential positioning system (DGPS). The main indices of the gap’s geometry including area (A), perimeter (P), and perimeter to area ratio (P/A) were measured and then the circular index (C) and the Gap shape complexity Index (GSCI) were calculated. Also, the frequency and diversity of tree species regeneration were recorded within 25 m2 plots centered on each gap. Gaps were classified into three small (20-150 m2), medium (150-300 m2), and large (more than 300 m2) area classes, and indices of species diversity were calculated for each gap using PAST software environment. Statistical analysis was performed to determine the significance of differences and relationships between geometric indices and diversity of regenerative species.

The average area of natural and Man-made canopy gaps were 206 and 176 m2, respectively. The mean circular index of Man-made canopy gaps (C = 0.72) was higher than natural ones (C = 0.66); although, their difference was not significant. Increasing the area, the shape of the natural gaps shifted away from the circular, elongated, and the complexity of their shape increased. The shape complexity index of Man-made gaps did not show a significant difference with increasing the area. Perimeter to area ratio of large gaps was smaller than other classes in both types of gaps. Regeneration density of Velvet maple and Ironwood species were significantly higher in medium Man-made gaps than other species, other classes, and natural mediums gaps. As a result, richness, total individual regeneration, diversity, dominance, and evenness in the medium gaps (300-150 m2) showed the maximum value and significantly different from the large gaps (greater than 300 m2). In natural gaps, with increasing area regeneration density of Velvet maple and Date-plum species, species richness, total individual regeneration, and species diversity of regeneration decreased significantly. A positive correlation was observed between the gap’s P/A with the regeneration density of maple and hornbeam species in natural gaps (r = 0.480 and r = 0.356, respectively). The richness index had a negative correlation with the perimeter (r = -0.337) and with area of natural gaps (r = -0.103). In Man-made gaps, the evenness index showed an inverse correlation and the species richness showed a direct correlation with P / A (r = -0.553 and r = 0.578, respectively).

Man-made gaps were more regular and rounder than natural gaps. As the shape of the Man-made gaps shifts away from the circle form, it was elongated and increased in fractures and complexities, and also the density of maple’s regeneration increased. Medium-sized Man-made gaps (150-300 m2) showed the highest value of richness, diversity, and regeneration density compared to other categories of gap area. Therefore, this range of gap size could be considered as the optimum range.

Soil respiration is the first way to return the carbon dioxide fixed in the vegetation into the atmosphere and plays an important role in the respiration of terrestrial ecosystems. This study aims to investigate the monthly and seasonal variability of soil respiration and its components (microbial and root respiration) rates in a mixed oriental beech stand located at Hyrcanian forests using a dynamic closed chamber system and root exclusion method. A total number of six locations with an area of 400 square meters were selected randomly at the canopy gaps and its adjacent closed canopy at Shast-kalateh forest, Gorgan. One sample plot with an area of 9 square meters (3×3) was installed at each location. Soil, microbial, and root respiration rates and some environmental factors were monthly measured during one year (from October 2016 to September 2017). The amount of soil, microbial, and root CO2 efflux ranges were 0.66-4.81, 0.3-3.41, and 0.36-1.43 μmol m-2 s-1, respectively. The highest increase in the soil, microbial, and root respiration rates were in summer (4.29, 2.86 and 1.34 μmol m-2 s-1, respectively), while the lowest rates were observed in winter (0.94, 0.54 and 0.41 μmol m-2 s-1, respectively). We found that the microbial respiration rate in the canopy gaps was greater than that of the closed canopy, but the rate of root respiration under the closed canopy was higher. Soil respiration rate had a positive significant correlation with soil temperature but had a negative significant correlation with soil moisture content. Variation in soil moisture content and soil temperature could change the soil biological characteristics, consequently soil fertility, and chemical properties. Therefore, we suggest the measurement of soil biological properties in the artificial gap with different areas for modeling the process of soil characteristics changes in the gap.

The sudden emergence of coronavirus disease 2019 (COVID-19) may lead to anxiety due to this disease among hospital staff. Therefore, the present study aimed to investigate the anxiety caused by COVID-19 and its relationship with burnout among hospital staff.

This descriptive cross-sectional study was carried out on the staff of a hospital located in Zahedan, Iran, in May 2020. The subjects (n=353) were entered into the study using the census sampling method and inclusion criteria and completed a three-part questionnaire containing demographic and occupational information, Corona Disease Anxiety Scale, and Maslach Burnout Inventory. The collected data were analyzed in Stata software (version 14).

Based on the results, more than half of the samples were females. Most cases were married and within the age range of 20-30 years. The prevalence of severe anxiety was reported to be 11.9% and 23.2%, 7.4%, and 57.5% of the subjects showed job burnout respectively in the components of emotional exhaustion, depersonalization, and personal inadequacy. It was also revealed that there was a significant relationship between anxiety caused by COVID-19 and burnout.

It was found that there was a significant relationship between corona-caused anxiety and job burnout. According to the high prevalence of such disorders, it is suggested that more attention be paid to hospital staff due to their special role in the treatment of Covid-19.

Assessing the workability of employees is very important, and firefighting is one of the critical jobs. Therefore, the aim of this study was to evaluate the work ability index (WAI), and identify some effective factors among firefighters.

This cross-sectional study was carried out with participation of 101 firefighters in Zahedan, Iran in 2018. Subjects were included in the study by census method. Data were collected using a two-part questionnaire (demographic information and WAI items), and data analysis was performed using SPSS 24.

The mean of age and work experience of the subjects were 34.18±6.70 and 8.47±6.79 years, respectively. Only 18 individuals (17.8%) were single, and most of them exercised at least once a week. The mean score of WAI was 44.33±3.56 and most of the subjects were in the excellent range. With increasing age and work experience, WAI decreased, and there was also a significant relationship between marital status and weekly exercise with WAI.

In general, the condition of the firefighters was favorable in terms of workability. However, due to the relationship between personal characteristics and WAI, it is necessary to adjust the duties of older people with more work experience.

Abstract

Paying attention to human resources is one of the basic principles for increasing productivity and quality of services in hospitals. Therefore, the present study was designed to compare the level of job satisfaction and job stress, and the association between these two components in nurses, operating room, and anesthesia staff

This is a descriptive causal-comparative study, performed in December 2019 in Zabol hospitals with the participation of 175 nurses, operating room, and anesthesia staff. A three-part questionnaire consists of demographic information, job satisfaction, and job stress was used to collect Data. Then analysis of data was performed using SPSS 20 and the Pearson correlation coefficient, independent t-test, and ANOVA.

In this study, it was found that nursing group had the highest job satisfaction and anesthesia and operating room staff had the lower job satisfaction. Also, the highest and lowest levels of job stress were related to anesthesiologists and nurses, respectively, and the differences in both variables were significant between the three groups. Moreover, the results showed that there was a significant negative correlation between job satisfaction and job stress, totally.

Due to that anesthesia staff was in a more unfavorable situation than the others, we recommended that management planning and policies in hospitals be done by occupational groups and design and carry out the studies to assess the needs for each group.

Climate change and human interventions as a whole have had negative and remarkable effects on the quantity and quality of forests. Beside the change in the forests extent, which has always been considered and monitored, its phenological changes have also been investigated in the last decade. The NDVI Vegetation Index derived from satellite data is an appropriate proxy for quantifying and expressing forest status including phenological changes. This study aimed to characterize the trend of start, end, and length of growing season using NDVI satellite time series dataset over 18-year time periods and then assess their relationship with precipitation and temperature parameters. This study was carried out over the southern Zagros forests using MODIS-NDVI time series with temporal and spatial resolution of 16-day and 250 meters, respectively. The precipitation and temperature datasets were also collected from regional synoptic meteorological stations. After preprocessing steps, 414 NDVI images during 2000-2017 were analyzed pixel by pixel to extract the start, end, and length of the growing season using Midpoint method, considering 50% and 35% thresholds of NDVI annual amplitude for start and end of the growing season, respectively. Then, the statistical significance of phenological metrics was assessed. Based on the results, the mean dates for the start and the end of growing season were 16th March and 15th August, respectively, with the mean length of growing season of 151 days in the study period from 2000 to 2017. Considering 35% of NDVI annual amplitude for the end of growing season, the mean date for the end of growing season was 8th September and the mean length of growing season was 190 days. The seasonal trend showed that the start and the end of growing season has occurred respectively 0.02 and 1.04 days earlier per year in the southern Zagros forests during 2000-2017. The length of growing season has been shortened 1.02 day per year. However, variation in the start and the end dates and the length of growing season have not been significant in 93%, 81% and 81% of the region, respectively, at 90 % confident level. Generally, the change in the occurrence of the end of growing season was greater than the start of growing season. A weak correlation was observed between phenological changes and climate parameters like temperature and precipitation in the study area.

Trees are the most important biological elements of forest ecosystems. The variability of the tree species composition inhabiting in the Oriental beech forest, not only forms different forest types but also has a remarkable impact on the species diversity of forest floor plants, due to the existence of trees in the overstory layer. In this research, forest types of an an Oriental beech were identified and their impacts on the species diversity of forest floor plants was compared and evaluated. Tree inventory was done at 16 hectares (100%) for two layers of trees and forest floor plants. The forest types were determined using the basal surface area of tree species and by the table synthesis method. The species diversity were calculated using richness index, Shannon-Wiener indices, Hill numbers (N1 and N2) and modified Hill (E5), Simpson. Evenness were calculated using Simpson, Camargo, Smith and Wilson indices and modified Nee. Analysis of variance showed that the impacts of forest types on plant diversity indices were significant. Differences between forest types were not significant in terms of evenness indices. Comparing the mean of tree species diversity indices in different forest types showed that Beech-alder and Beech-maple types had similar values. Whereas in the forest floor vegetation layer, diversity indices were highest in Beech-maple type and lowest in Beech-alder type. Maple and Alder have different ecological characteristics, thus changed the forest environment in different ways, resulting variability in species diversity of forest floor plants. These findings can be applied for comparing the forest developmental stages and also determining and conserving the diversity hotspots.

The objective of this study was ecological assessment of the Danish and Swiss thining methods in 20-years old reforestations of Brutia Pine (Pinus brutia Ten.). This research conducted under completely randomized block design (CRBD) with three replication and three treatments (Swiss and Danish thinning methods and control); a total of 9 plots each 2000 m2 (40 x 50 m). The quantitative and qualitative parameters of trees were measured by full callipering in each plot. In order to investigate the species diversity of plants and the natural regeneration in each plot, three micro samle plots of 49 m2 were randomly selected. Sampling of soil invertebrates was performed from a depth of 0 to 10 cm in the center of each micro sample plots. The parameters were measured in the years of 2013 (before thinning) and 2018 (five years after thinning). This study showed the mean diameter at breast height (dbh) and mean height of Brutia trees and the whole stands, as well as, simpson plant diversity and soil invertebrates' diversity between treatments were not statistically significant in 2018. Mean dbh of the whole stand and Pine trees were accounted to 17.02 cm and 22.74 cm in Danish method, 16.94 cm and 21.71 cm in Swiss method and 15.59 cm and 19.53 cm in the control plot. Mean height of the whole stand and Pine trees from Danish and swiss methods to the control plot were accounted to 11.13 m and 13.19 m, 10.88 m and 12.68 m and 11.44 m and 13.58 m, respectively. The average species diversity of Shannon plants in the field of Danish thinning was significantly higher than the Swiss method and the control area. Also the Simpson plant diversity was higher in the Danish method, followed by the control and the Swiss method, while the soil invertebrates’ diversity was higher in the Swiss method followed by the control and Danish method. Also the results of this research showed that the quality of the Brutain Pine and the whole stand in the thinned treatments were better than that of the control plot in 2018 (ρ=0.05). This research emphasizes the need for thinning operations in the forest plantations.  Over all this research suggests application of the Danish method in Brutia Pine plantations in terms of increasing the quantitative and qualitative characteristics of trees, along with the increasing of plant diversity