FOREST RESEARCH AND DEVELOPMENT
Year:2024 | Volume:10 | Issue:1|Papers Count:9

Background and objectives: Nowadays, chainsaws remain the primary main tool for wood harvesting in the world due to their multifunctionality and the relatively low requirements in financial investment. Another reason is that chainsaws provide high workability, enhancing efficiency and productivity, at reduced felling costs. The felling of poplar stands in the west of Guilan Province is carried out semi-mechanically using chainsaws within a clear-cutting silviculture system. Productivity and cost are two main factors that affect the selection of wood harvesting systems, whose tree felling consists an element of paramount importance, most notably its duration. The purpose of this study was to assess the productivity and cost of clear-cutting operations in a poplar plantation located in the western part of the Guilan Province, using the MASHOUF PSI 9700, a short-bladed chainsaw model with a bar length of 50 cm.Methodology: The research was conducted in the Tanyan district, which is located in the western part of Guilan province. A work team, consisting of a chainsaw operator and a helper, was used during the study. The selected work team was chosen as representative of the average skill level of the workers in the region. The chainsaw selected for this research, the MASHOUF PSI 9700 model featuring a cylinder displacement of 54 cm3 a power output of 2.2 KW, and a weight of 5.1 kg excluding equipment, had been in operation for about 2000 hours, which is the average life span of a product of this category. Over the years, the research on consumption time has focused especially on establishing the relationship between work efficiency and productivity carried out considering various equipment and wood harvesting factors. Analysis of work time consumption and productivity in chainsaw operations is an important concern of sustainable harvest management. A time study was performed to calculate the hourly productivity rate. Felling time was classified into two categories, namely effective time and delay time. Effective time consisted of (a) Moving towards the tree, (b) Felling preparation, (c) Under cut, (d) Back cut and (e) Refueling. Moreover, the delay times fell into (a) Rest time or personal time, (b) Operational delays, and (c) Technical delays. The total fixed cost was obtained considering the chainsaw purchase value, the sum of the annual investment, the depreciation, the insurance and taxes. Variable costs were also calculated considering the hourly expenditure on fuel cost, maintenance as in the cases of chain and sprocket replacement, etc. The sum total of costs included fixed, variable and labor costs. The data was initially processed using Excel 2013 software and then analyzed using the SPSS statistical software version 18 to determine the distribution and ratio of work interruption time according to the factors affecting it. Regression analysis was conducted to explore the relationship between the factors affecting the total cut-off time.Results: A total of 133 trees were felled amounting to a volume of 109.06 m3. The total work time consumed for felling operations was 500.21 minutes. Of the total working time, 41.42% was allocated to main work tasks. Supplementary work, such as moving between trees and driving wedges, accounted for 8.84% of felling time, while preparatory tasks, including moving between workplaces and preparation activities, constituted 15.29%. Repair time accounted for 9.60% of the total time, while delays and downtime occupied 15.74%. Additionally, 9.09% of the time was spent on non-workplace activities. The majority, 71% of the delays were linked to personal delays, of which 80.7% were related to lunchtime breaks and 19.93% to other personal delays. Operational and technical delays accounted for 10% and 19% of total delays, respectively. Increases in the diameter of the felled trees, resulted in increases to both the net felling time and the net production of the felling team. Furthermore, an increase in the diameter decreased the production cost. The results showed that the average time consumed per tree for felling were 2.73 min of effective time vs 3.75 min of gross time, and net hourly productivity amounted to 17.28 m3 per hour vs 13.44 m3 per hour found for the gross hourly productivity, and the unit cost of net production was 0.25 USD vs 0.32 USD for the gross production, respectively. The statistical analysis exhibited a highly significant correlation between work element times (measured in minutes) and various factors, including the diameter of the tree at breast height, tree volume (measured in m3), and the distance between trees (measured in m).Conclusion: By developing mathematical models of working time for various chainsaw models, chainsaws, the performance of the felling teams can be increased, and a more equitable remuneration of the forest workers is made possible. The results of the present study can support decision making regarding the work rates, work schedules, and cost estimation. The models and results presented in this study can generally assist forest managers to better understand the factors affecting productivity and cost during different work elements with the aim to reorganize and plan forest work to meet economic concerns.

Background and objectives: Efficient and high-quality information about the current and future state of the forest is needed for sustainable management and basic planning of forest resources. Zagros forests, as one of the most important vegetation areas of Iran, have a very important effect on water supply, soil conservation, climate adjustment and economic and social balance in the whole country, hence, the sustainable protection and management of these forest ecosystems The main concern of researchers and managers in this area has become vegetation. The dominant species of these forests is Iranian oak (Quercus brantii Lindl). According to geographical and environmental conditions, this species has various habitats in the vegetation zone of the middle Zagros. Considering the noble position of the Iranian oak species in the forests of Zagros, the importance of developing more researches regarding this species is essential. The characteristics of tree diameter and height are the most important components needed in forest statistics. These variables are one of the main variables for measuring the appearance characteristics of forest trees and are used in cases such as determining the volume and drawing the height curve. Considering that measuring the height of all forest trees is a long and expensive operation, hence the use of diameter and height models to estimate the height of trees has been developed. The purpose of this research is to investigate the linear and non-linear diameter-height models of Iranian oak species (Q. brantii Lindl) in the high forests of the Middle Zagros in order to find the answer to the question of whether it is possible to estimate the height of Iranian oak high forest trees as There is a function of the diameter of the chest in this vegetative zone or not.Methodology: This research was conducted in Sefidkoh protected area of Lorestan. The dominant tree cover of this area is made of oak, like other areas of Zagros, but other plants and trees such as Cratagus persica pojark, Amygdalus sp, Astragalus sp, etc. can be mentioned in it. To carry out this research, by conducting numerous forest tours and getting to know the forests of the region, a stand with an area of approximately five hectares, which had a high forest vegetation structure, was selected. In the selected forest stand, the characteristics of DBH and total height of all Iranian oak trees whose DBH was more than 12.5 cm were counted as 100%. In total, 642 Iranian oak trees were measured in DBH and height. Linear and non-linear models were used to fit the data of DBH and height of trees, which include various models of exponential, power, density-product, growth, sigmoid and other functions. In this research, 80% of the data were used in the modeling process and 20% were used for evaluation, as well as for fitting the data and estimating the indicators of each of the models from the Curve Expert Professional software, which is a software Comprehensive software was used to fit the curves. In the modeling process, diameter data were used as independent variables and height data were used as dependent variables. In the upcoming research, to verify the accuracy of the obtained models, the RMSE, MAEand Bias in absolute and relative terms, as well as the R2 and the AIC was calculated as validation indices.Results: Based on the descriptive statistics of Iranian oak trees, the average, minimum and maximum DBH was 42.42, 12.5 and 150 cm, respectively, and the height was 6.3, 1.2 and 17 meters, respectively. Based on R2 values, the used models explained 62 to 86% of the total changes in tree height. The results of tree height-diameter modeling showed that Gompertz, MMF and Richard models have the highest explanatory coefficient (0.86, 0.86, 0.86), respectively, and the lowest standard error (307. 1, 1/307, 1/307) and AIC information criterion were (276/04, 277/13, 277/03). The results of the criteria used to validate the used models showed that the Gompertz, MMF and Richard models have RMSE of 22.22, 22.20 and 22.20%, respectively, as well as MAE respectively. 16.69, 16.74 and 16.79 percent were better able to estimate the characteristics of the height of trees. According to the mentioned results, it was found that Gompertz, MMF, and Richard models have a higher ability to estimate the characteristic height of Iranian oak trees compared to other models.Conclusion: Overall, the results of this research showed that linear and non-linear models have the ability to estimate the height of Iranian oak high forest trees in the growing region of the middle Zagros, and among these models, three non-linear models are Gompertz, MMF and Richard based on evaluation criteria. The performance was more accurate. Therefore, these models can be used in the forest areas of the middle Zagros vegetation zone, which have the same structure and habitat conditions as the studied area. It is suggested to use the generalized models of height and diameter in future researches.

Background and objectives: Biodiversity loss, increase in invasive species, and climate change are challenging issues of this century leading to decreased plant diversity and negative impacts on the sustainability and stability of ecosystems such as forests. Arasbaran forests have significant changed in recent years due to degradation and human interventions. Therefore, it is essential to assess the biodiversity of Arasbaran forests in terms of species composition and species diversity to improve the forest stands stability. The aim of this research was to evaluate and determine the tree and shrub species diversity in the Arasbaran forests using biodiversity indices and classifying forest stands based on their species similarity.Methodology: Mountainous broad-leaved forests of Arasbaran located in the northwest of Iran belonging to the main Euro-Siberian region and the Hyrcanian sub-region is known as a biosphere reserve of Iran. However these forests are protected, but intense human activities in recent decades have severely changed the appearance, composition, and structure of Arasbaran forests.To conduct this research, 12 forest stands were randomly selected all over the area based on suitable distribution of stands in different forest types and elevation gradients using a two-stage sampling method. Then, 347 circle permanent sample plots of 300 and 1000 m2 were established using a systematic-random sampling approach and all tree parameters were measured. Afterward, species composition, basal area distribution, mean cross-sectional area, density per hectare, tree height, and proportion of sprout and seedling bases were estimated based on the collected data.To assess the species diversity of the stands, Margalef and Menhinick richness indices, Pielou and Heip evenness indices, and Shannon-Wiener and Simpson diversity indices were used. Furthermore, the Jaccard index was applied for classifying forest stands based on species similarity or dissimilarity, and a dendrogram was prepared based on Jaccard distances. Statistical differences among groups regarding biodiversity indices were examined using analysis of variance.Results: Based on the results, 25 tree species were identified in the study area, including four dominant species of Carpinus spp L. with 40%, Quercus spp L. with 29%, Juniperus spp L. with 12%, and Acer spp L. with 11%. The quantitative characteristics of the studied stands indicated that the forests of Arasbaran are young forests with small tree diameters (average diameter of 10 cm) and high tree density, with the dominance of coppice and seedling bases, that it is likely due to historical clear-cutting of forests for charcoal production, strong resprouting ability of species such as hornbeam and oak, and human interventions. The obtained six biodiversity indices showed that the species richness, evenness and biodiversity were moderate, very low, and relatively moderate respectively in the Arasbaran forests. Based on the Jaccard index, forest stands were divided into five groups, which analysis of variance results indicating significant statistical differences between groups in terms of biodiversity indices. The highest biodiversity indices related to mixed broad-leaved stands with values of 1.15, 0.66, and 0.21 for richness, evenness, and diversity indices respectively, while the lowest indices associated with pure stands of Quercus macranthera with values of 0.28, 0.06, and 0.12 for richness, evenness, and diversity indices respectively. Furthermore, the Margalef, Pielou and Shannon-Wiener indices were recognized as the best indices for the region based on the coefficient of variation.Conclusion: According to the results, biodiversity of tree species is more influenced by species richness, and species richness plays a significant role in the variation of biodiversity in the Arasbaran region. These forests are dominated by two or three tree species, that leading to a reduction in evenness. This research revealed that classifying tree species based on biodiversity using the Jaccard index, which effectively differentiated groups, is feasible and can be useful in conservation and management decisions. Therefore, it is necessary to assess the biodiversity indices and identifying factors caused to reduction in biodiversity in the region in order to improve them to achieve sustainability. Successful management plans depend on proper conservation practices for the forests, preventing livestock grazing in the forest stands, avoiding tree cutting, identifying seed-trees and creating space for seed production by removal of the coppice sprouts and investigation of the reasons for lack of establishment of regeneration in the region.

Background and objectives: Drought stress is one of the most important factors limiting plant growth in the world and one of the most common abiotic stresses. Drought stress is a multidimensional stress that stimulates a wide range of physiological, biochemical and molecular responses in plants. In arid and semi-arid areas, the establishment and growth of young seedlings is completely affected by water deficit and drought stress. In this situation, the use of symbiosis of microorganisms, especially mycorrhizal fungi, can reduce the effect of drought stress via increasing the absorption of water and nutrients. Therefore, the aim of this study was to determine the effect of mycorrhizal fungi symbiosis on the absorption of the on the absorption of some macro and micro nutrients as well as the activity of antioxidant enzymes of Paulownia fortunei (Seem.) Hemsl., known as a fast-growing species.Methodology: This pot experiment was conducted in factorial form in a completely randomized design with three replications and two factors. The first factor included four levels of drought stress (no stress or control with full irrigation at 100% of crop capacity, mild stress with irrigation at 80% of crop capacity, moderate stress with irrigation at 60% of crop capacity and severe stress with irrigation at 40% of crop capacity) and the second factor which included two surfaces of using mycorrhiza (without and with arbuscular mycorrhizal fungi). Application of drought stress treatments was done based on the weight method. The investigated features included the measurement of soluble protein, catalase, peroxidase, superoxide dismutase enzymes, as well as the absorption of nutrients such as phosphorus, nitrogen, potassium, zinc, iron and manganese. The normal distribution and the homogeneity of the variance of the obtained data were checked using the Shapiro-Wilk test and Levene's test, respectively. Two-way analysis of variance was used to test the significance of the simple and interaction effect of the factors. Duncan's multiple range post-hoc test was used to compare the means.Results: The results of analysis of variance showed that the interaction effect of drought stress and mycorrhiza was not statistically significant on any of the traits. The simple effect of mycorrhiza on the changes of superoxide dismutase enzyme was significant, but it was not significant on other measured traits. The results showed that drought stress significantly increased the amount of soluble protein, peroxidase and superoxide dismutase activity. The highest concentration of soluble protein was related to severe stress treatment with a mean value of 38.95 mg/g leaf wet weight, and the lowest is related to the control or no stress treatment with a mean value of 31.45 mg/g leaf wet weight. However, no significant difference was observed between mild, moderate and severe stress treatments. About catalase enzyme no significant difference was observed between moderate and severe stress treatments, as well as between mild and moderate stress treatments. The highest concentration of peroxidase enzyme was related to severe stress treatment with a mean value of 3.77 mg/min per mg of protein and the lowest mean value (3.21 mg/min per mg of protein) was related to non-stress treatment (control). No significant difference was observed between the treatments of moderate stress and severe stress, as well as between the treatments of mild and moderate stress in terms of the concentration of peroxidase enzyme. The highest concentration of superoxide dismutase enzyme was related to severe stress treatment with a mean value of 0.176 mg/mol/min per mg of protein and the lowest value (0.108 mg/min/mg of protein) was related to the control. The concentration of superoxide dismutase enzyme in the treatment with mycorrhiza with a mean value of 0.159 mg/mol/min per mg of protein was significantly higher than of it in the treatment without mycorrhiza with a mean value of 0.140 mg/mol/min per mg of protein. Drought stress also led to the reduction of all measured nutrients. While, inoculation with mycorrhizal fungi increased nutrients except nitrogen at all levels of drought stress.Conclusion: It was concluded that although the absorption of macro and micro nutrients by the seedlings decreased with the increase of drought stress levels, the use of mycorrhizal fungi could increase the absorption of macro and micro nutrients in drought stress conditions due to the better absorption of water by the hyphae around the roots of Paulownia seedlings. Therefore, it seems that the mycorrhizal fungi are very important in the absorption and metabolism of elements required by Paulownia seedlings, especially in stress conditions. Also, the inoculation of mycorrhizal fungi led to an increase in the activity of the antioxidant enzyme superoxide dismutase (SOD), which can increase the resistance of seedlings against drought stress.

Background and Objectives: In recent years, following the failure of government management policies in Zagros forests, the country's natural resources organization (NRO) has emphasized the participatory management approach. Although the implementation mechanism of this policy and its framework has not been cleared, utilizing the capacities of all stakeholders, especially women, is one of the most important manifestations of the realization of participatory management. Rural women make up half of the beneficiary population of natural resources and, despite the limitations, play a considerable role in managerial, social, and economic activities. However, the main focus and attempt of managers' intention on participation, has been dedicated to men. Rural women affect the quality of management and protection of natural resources due to their wide connection with these resources and the transfer of their knowledge, information, and beliefs to the next generation. This study aimed to identify the role of rural women in activities related to natural resources management in villages of Chahar-zebar region – Kermanshah.Materials and Methods: Four villages of Chahar-zebar Olia, Deh-Sefid, Goharabad, and Kashanbelek in Mahidasht district of Kermanshah province were selected to conduct this research. The considerable forest cover and employment of most of the villagers in rural jobs and animal husbandry to meet their livelihood were among the most important criteria for choosing these villages. A total of 153 women living in the villages were interviewed in a survey using a researcher-made questionnaire and through semi-structured, face-to-face interviews (mainly due to the low literacy level) and direct observation of women's activities. The individual characteristics of the respondents, the general profile of the household, the role of women and the time of their participation in various activities of managing and utilizing natural resources, the relationship of women with the natural resources administration, women's knowledge of the natural resources of their village, the repeatability of activities and the participation and companionship of other people were among the variables that were recorded and measured for investigation the role of women in the management (conservation and utilization) of natural resources. To evaluate the role of women in management and decision-making at the household level, their role in the directing and administration of expenditure and income was questioned. Spearman's correlation analysis was done to determine the relationship between different personal and social characteristics of women with different features of the activities performed by them.Results: Based on the findings, women in the villages surveyed have a low to medium knowledge about natural resources. Despite predicting 30 types of activities related to natural resources in the questionnaire, women were involved in only 27% of natural resources activities while a considerable share of the practices (96.7 percent) were done with the participation of other people (other women, husbands, and children respectively). Women were more commonly engaged in activities such as collecting mushrooms, edible plants, seeds, fruits, medicinal plants, and firewood, while tasks like using forest wood, fighting forest fires, and fencing yards with branches were less commonly performed by women. This study showed that women's knowledge of the village's natural resources was average to low. Correlation analysis indicated that factors such as age, religious activity and the desire to migrate had a negative relationship with the role of women in both management and decision making, while a positive correlation was observed for time spent in forest activities. Additionally, variables like age, length of stay in the village, and tendency to migrate were also negatively correlated with the time spent on forest-related activities.Conclusion: Based on the research findings, it is evident that women in the studied region have limited participation in the management of natural resources. They only engaged in the utilization of some forest and pasture products while not performing considerable activity in the conservation and development of the resources. Therefore, it is crucial to recognize and enhance the role of women in governing natural resources to improve preservation and restoration efforts. Raising awareness, providing counseling, and increasing involvement of women in this field are essential steps to address the current lack of participation. The fact is that contrary to the claim of NRO, local communities, and villagers, both women and men, do not have a considerable role in the management of natural resources. The very little connection with the natural resources’ office indicates the lack of promotion and educational programs suitable for women and the lack of presence of natural resources experts among local communities. Therefore, it is suggested that the Natural Resources and Agriculture Departments seriously take into account education to local communities in their plans. Paying attention to the education and empowerment of young women is of great importance in the management of natural resources, since they perform more activities in natural resources, they have relatively more knowledge of natural resources, and their role in management and decision-making is also more considerable. We concluded that the duration of women's activity in natural resource appears to be a key factor determining their understanding and involvement. It is essential to valuing women's contribution and utilizing their potential effectively in natural resources conservation and restoration to establish an efficient participatory management system.

Introduction and Objectives: The Zagros forests vegetation area with an area of more than 5 million hectares and providing more than 40% of the country's water are ecologically very important and the forest covers 256000 hectares of Kurdistan province (8.8% of the province) and in recent years, Oak decline and decay have increase in these forests. Oak decline in the Zagros forests has started in the last two decades and has caused serious damage to the forests of this vegetation area and study of the effective and aggravating factors of Oak decline provides valuable information to natural resource managers. The factors of slope aspect and physical and chemical soil parameters can has an effect on the aggravation oak decline in this forest. The aim of this study was to investigate and compare the physical and chemical soil parameters in around healthy and dieback trees under the influence of slope and dieback in Marivan forests (in Kurdistan province).Materials and Methods: Deteriorated (Garan) and control (Dolah Naw) stands were selected in the northern and southern slopes aspect. In the Garan habitat (Oak decline) on the northern slope, five healthy trees and five dieback trees were selected (10 trees in total), on the other hand, in this habitat on the southern slope, 10 more trees were selected (five healthy trees and five trees with dieback). In Dolah Naw habitat (control habitat), five healthy trees were selected in each aspect (in total, 10 trees in the control habitat). In total, 30 healthy and dieback trees were selected and numbered (20 healthy trees in the control and dieback trees and 10 trees in the dieback stands). Then, in the vicinity of the trunk of each tree (in the shaded part of the crown), a soil sample was taken at a depth of 0-20 cm (Horizon A) and the samples were transported to the laboratory in plastic bags. Physical and chemical characteristics (moisture percentage, acidity, soil electrical conductivity, absorbable phosphorus, absorbable potassium, nitrogen percentage, organic carbon percentage, lime, calcium and magnesium percentage) were measured for each soil sample. The two-way analysis of variance test was used to compare the effect of each factor and the interaction effect of the investigated factors on the physical and chemical parameters of the soil and data analysis was done in SPSS 20 software.Results: The one-way analysis of variance test showed that there was a significant difference between the parameters of pH, electrical conductivity, percentage of organic carbon, potassium, nitrogen, moisture, lime, magnesium and calcium among the soil samples of healthy and dieback trees in the northern and southern slopes. The results of the analysis of variance test confirmed the interaction effect of kind of stands × slope aspect for electrical conductivity and calcium and for slope aspect × tree health in the parameter was lime percentage. Other findings showed that the highest average parameters of electrical conductivity, available phosphorus, potassium, organic carbon, nitrogen, and moisture were respectively 2.654 (d s m-1), 1.10 (mg/kg), and 869.5 (mg/kg). ), 4.03%, 0.35% and 12.4% were observed in the soil adjacent to the control trees in the northern slope and for magnesium, calcium and CaCO3 parameters of healthy trees in the southern slope with the values ​​of 21 (meq/100), 42.2 (meq/100) and 13.60% was significantly more than other treatments. On the other hand, in the soil sample adjacent to the trees located in the stands affected by dieback, the average physical-chemical parameters were lower than the control stand (Doleh Naw) and this shows the importance of the physical-chemical parameters of the soil in reducing or increasing the resistance of trees to tree dieback. The findings of the research showed that the highest average macro elements (available phosphorus, potassium and nitrogen) in the soil adjacent to healthy trees in the northern slope and for calcium and magnesium, the highest amount of these elements were observed and confirmed in the soil adjacent to the trees in the southern slope and in the total amount Macro elements were more in the soil of the trees of control (north and south domain); Therefore, the physical and chemical characteristics of the soil (especially macro elements) have an effect on the resistance of oak trees to dieback and other environmental stresses, and the lack of macro elements causes the trees to be weak against the phenomenon of oak dieback.Conclusion: In general, in the soil adjacent to the dieback trees, the poverty of nutrients and macro elements and lower values ​​of the studied parameters were observed. In general, in the trees affected by Oak decline, the poverty of nutrients and macro elements was observed, and the lower values ​​of the parameters were observed in the soil adjacent to the trees affected by Oak decline. Based on the results, for the optimal management of dieback stands and trees, increase protection measures (control of livestock grazing through grazing and reduction of traditional exploitations), increase restoration programs and forest development in the stands affected by dieback (increase seeding and enrichment operations). In degraded stands and planting with native species in dieback stands) and implementation of health cuts (withered and dieback branches and stems) were suggested.

Background and objectives: Silviculture is considered one of the most important activities of forestry and includes all issues related to training and improvement of forest stands. The main goal and purpose of forest treatment is to strengthen and improvement of the quantitative and qualitative of forest stand and to keep it in health condition during the long life of forest. Different cuts in the forest as forestry tools play an important role in guiding the forest stand towards the desired goals. These cuttings are done to improve forest stands and to achieve the development and sustainability of forest ecosystems. Investigation the importance and impact of these cuts in the target forests of the region is vital for forest management. This research conducted with the aim to compare the quantity and quality of mature forest stands and the regeneration of improvement cutting stand (improvement cutting operation for 14 years) and the control stand (adjacent to the improvement cutting stand) in Makidi area of Kalibar city.Methodology: Makidi region located in the protected part of Arsbaran forests and in the southwest of Kalibar city. The altitude of this area is 1400-1500 meters above sea level and it is located in the western part of the middle Kliberchay river watershed. Both of the treatment areas were similar in terms of physiographic and ecological conditions and differed only in terms of the type of treatments. A total of 5% of the trees in the improvement cutting stand were harvested during the 14 years. In this operation, the trees that were weak or diseased in terms of their appearance, or the trunks of the trees that were attached to the elite trees or that had crown and root disturbances removed. The total surface area under study is 40 hectares, of which 20 hectares considered for each of the treatments. Using a 50x50 meter grid, 33 circular sample plots of 300 square meters were implemented in the control area (three sample plots located inside the uncovered area) 36 sample plots established in the improvement cutting area. Also, the regeneration of woody species in both stands investigated in circular sample plots with dimensions of 100 square meters centered on the main sample plot.Results: The results showed that the average d.b.h of the trees was 11.35 and 10.98 cm, the average crown diameter was 2.48 meters and 2.11 meters in the improvement cutting stand and control stand, respectively. The average height of the trees in the improvement cutting stand was 9.22 meters and, in the control, stand was 9.61 meters, and the difference between the two stands was not statistically significant. Regarding the number of trees per hectare in both stands, the highest number recorded in the 10 cm diameter class, and in the higher diameter classes, the number of trees decreases. The results show that the stand is immature and fewer trees are in higher diameters. Observing the state of the two stands shows the youth of these stands, and considering that they are at the age of growth, they are high in number per hectare, and the competition between the stands to obtain soil nutrients and light is high and the demand for more treatment interventions can be felt. The height-to-diameter ratio of two improvement cutting stand and control stands shows that the average height-to-diameter ratio in the control stand is higher than in the improvement cutting stand, which indicates the improvement of the ratio due to cutting operations and the better stability of the stands after improvement cutting operations. Among the most important trees and shrubs observed in the study area, species such as Quercus petraea, Quercus macranthera, Acer compestre, Carpinus betelus, Cerassus avium were recorded. The results show that in terms of species composition, Quercus petraea was 56% and cypress species 0.31% more than the control population in the improvement cutting stand. The percentage of trees with a healthy crown is 93.4% and 93.9% and the upright trunk angle is 68.7% and 43.5% in the improvement cutting stand and control stands, respectively. Examining the tendency of the trees shows that trees in the improvement cutting stand has a more favorable position than the control stand, However, the control stand also have a favorable condition. The stand origin observed in the study area is seedling. The correlation between the diameter and height of trees in both the improvement cutting stand and control stands shows a significant exponential relationship, and the coefficient of determination for the improvement cutting stand is better than the control stand. In terms of the frequency of regeneration, the control stand has a more suitable state of regeneration compared to the improvement cutting stand, and the highest number of regenerations observed in the 5 to 7.5 cm diameter classes, followed by the 2.5 to 5 cm and 0 to 2.5 cm diameter classes.Conclusion: The summary of the obtained results shows that these stands need more intervention and subsequent cuttings to increase the amount of light and nutrient to the remaining trees which causes more diameter growth increment. It is recommended that these studies be repeated every five years to understand better the impact of this operation.

Background and objectives: Plant Species Richness (PSR) plays an important role in forest ecosystem functions and services. Despite the fact that Fine Woody Debris (FWD) occupy a large volume of the temperate forest ecosystem in the north of Iran, they have received less attention than Coarse Woody Debries (CWD). FWD is a component of natural forests, in addition to increasing the productivity of forest trees, helping to trees regeneration, maintaining and increasing soil moisture and nutrients, and long-term carbon storage, contribute the enhanced function of newly developing microhabitats with an important function in plant understory richness. Therefore, not paying attention to FWD leads to wrong estimation of the total volume of woody debries and its key role on the performance of forest ecosystems. Therefore, it was considered for current study that Boosted Regression Tree (BRT) machine learning technique used to model the PSR in unmanaged forest stands. For this aim, Oak - hornbeam stand in Loveh forest in the east of Golestan province, Iran was selected for sampling.Methodology: For this purpose, 30 sample plots 400 m2 (20 m × 20 m) were set in the study area, and the type and percentage of plant cover was recorded based on the Braun-Blanquet index. In the following, the number of plant species recorded in each sample plot was the basis for calculating species richness. In order to measure the volume of FWD, the alignment of the sides of the sample plot of 400 square meters was used as the basis of calculation. Therefore, in line with the sides of each sample plot and in the form of a linear transect with a total length of 80 meters (equal to the perimeter of each sample plot), FWD intersected with the transect were identified. The names of tree species of each of the FWD is specified, and according to the cross diameter with the transect, the FWD were placed in one of three diameter classes: 1 to 2.5 cm, 2.5 to 4.5 cm, and 4.5 to 7.5 cm. To measure the percentage of soil moisture and organic matter, the soil was taken from the center of each sample to a depth of 15 cm. Soil moisture percentage was obtained by using the difference between wet and dry weight of soil and also the amount of soil organic matter by Walkley-Black method in the laboratory. The gmb package in R programming language was used to fit the boosted regression tree model. This model is one of the methods that helps to improve the performance of a single model by using the combination of multiple models. Therefore, in this method, the combination of two algorithms "regression tree and classification" and "boosting" is used. It should be noted that in this research, in order to reach the optimal number of trees, the number of 1000 was used as the starting point. In this study, the amount of species richness in each plot as the response variable, and the variables of slope percentage, slope aspect, altitude, soil moisture percentage, soil organic matter percentage, average of total volume of fwd, average volume of fwd in decay class 1, average volume of fwd in decay class 2 and the type of fwd were considered as predictor variables.Results: Based on the results, the initial model fitted in the number of trees 7700 showed the highest accuracy. However, due to the lack of influence of some variables in the model, the variables of slope, slope aspect, altitude, the type of fwd and the average volume of fwd in decay class 1, these variables were excluded from the model based on the deviation changes. And the model was refitted in the optimal number of trees of 7800. Based on the final model of the BRT, the highest amount of species richness was recorded with the increase of soil organic matter to > 2.15% and in a soil moisture percentage >30%. Furthermore, a high amount of FWD from the first diameter class and with the decay class 2 (rotten) led to an increase in plant richness in the studied area. In the present study, the adjusted R squared > 0.99 with the Root Mean Square Error (RMSE) < 0.039 shows the high accuracy of the BRT model.Conclusion: Although fwd comprise a large part of woody debries in the forests of the north of Iran, no specific place has been considered for it in any of the statistical protocols. This matter has led to the fact that there is no specific estimate of the volume of fwd and its role on the forest ecosystem is neglected. Therefore, this study was conducted with the aim of modeling the effect of this important component on the richness of plant species in a broadleaf stand in Loveh forests of Golestan province. The findings of the research showed that by creating favorable habitat conditions, the fwd increase the abundance of plant species and maintaining this component is important in increasing the organic matter of the forest soil. The high rate of decomposition in fwd compared to cwd causes that while maintaining and increasing the soil moisture, the organic materials in the wood are available to the soil layer in a short period of time. In recent years, some experts in the field of natural resources have emphasized the collection of fwd and their use in cellulose industries. A large part of these opinions has also found a scientific basis in the shadow of the minimization of the volume and role of the fwd and the lack of sufficient information about this very important component. If the findings of this research clearly show that the collection and removal of fwd will have a negative impact on soil moisture and organic matter and thus on the richness of plant species. Conducting similar and additional studies by including soil nutritional variables as well as other plant indicators can significantly help in confirming or rejecting this result

Background and objectives: In forest ecosystems, the decomposition of leaf litter is one of the most important ways of entering nutrients into the soil, and the availability of soil nutrients is largely due to the dynamics of nutrients and leaf litter decomposition in the forest. Decomposition of dead leaves enables important ecological functions and affects the composition of the internal nutrients of trees. Decomposition processes influence the formation of soil organic carbon stocks. It is necessary to understand how climate change and global warming affect the decomposition process and thus the amount of carbon stored in the soil. The space-for-time (SFT) approach makes it possible to compare litter decomposition in current conditions and at different altitude levels, and to investigate the effects of increased temperature on litter decomposition. The present research was conducted with the aim of investigating the effects of increasing or decreasing temperature on the decomposition rate of leaf litters in pure and mixed states.Methodology: In the present research, by using the space-for-time approach, the decomposition rate of leaf litters (in two pure and mixed states) in three tree species (Quercus brantii, Celtis australis and Pistacia atlantica) was carried out in three altitude classes of 750, 900 and 1050 meters in the forests of Dareh Shahr. The forests of this region have relatively severe topography and have mountains and hills with steep and smooth slopes, and there are rocky outcrops in many parts of it. The average height of the area is 1200 meters and the average slope is 15%. The average annual temperature is 21.40°C and the average annual precipitation in this region is 426.3 mm. The climate type of the studied area is semi-humid. To achieve the objectives of the research, the leaf litter of the studied species were randomly and manually collected from the forest floor in the fall season of 2020. After preparing litter bags, a number of 243 single-pocket and double-pocket litter bags were installed on the mineral soil at the litter collection sites and during 180 days with intervals of 30, 60 and 180 days and the decomposition rate of the leaf litters were measured. In order to measure the decomposition rate of the leaf litters, the primary and secondary weight of the leaf litter was recorded and the weight loss of the leaf litter was calculated through the weight relationships. To determine the initial quality of leaf litters, the nutritional elements of leaf litters such as nitrogen, carbon, phosphorus, calcium, potassium and magnesium were measured.Results: Based on the results, it was found that the studied leaf litters are similar in terms of magnesium, phosphorus and nitrogen concentrations. Quercus brantii leaf litters had the highest amount in terms of potassium and carbon concentrations. Also, Celtis australis leaf litters had the highest amount in terms of calcium concentration. The quality ratio of C:N in Celtis australis litter was low, this issue shows the high quality of this leaf litter. The results showed that in the studied time periods, litter type, height above sea level (except for the period of 180 days) and the interaction effects of litter type and height had significant effects on decomposition rate, so that increasing the altitude above sea level has led to further decomposition process. Based on the findings of the research, it was found that in the period of 30 days, the highest amount of decomposition related to the combined treatments of Celtis australis (Celtis australis+Pistacia atlantica) and Quercus brantii (Quercus brantii + Celtis australis) (14.61% and 14.40% respectively) at the height of 1050 meters and the lowest was related to the treatment of Pistacia atlantica (4.52%) at the height of 750 meters. In the period of 60 days, the highest amount of decomposition rate was observed in the combined treatment of Celtis australis (Pistacia atlantica + Celtis australis) at the height of 1050 meters (15.41%) and the lowest amount of mass loss was observed in the treatment of Pistacia atlantica at the height of 750 meters (5.31%). Also, at the end of the incubation period, the highest amount of decomposition rate belongs to the combined treatment of Celtis australis (Celtis australis+Pistacia atlantica) at the height of 1050 meters (16.12%) and the lowest is related to the pure leaf litter of Pistacia atlantica at the height of 750 meters (10.12%).Conclusion: In general, based on the findings of this research, with the increase in altitude above the sea level, the rate of mass loss not only did not decrease, but also increased significantly (especially in the first two months of incubation) compared to the lower altitude classes. Also, at the end of the study period, only the interaction of height and type of litter was able to affect the amount of decomposition of litter.