جستجوی مقالات مرتبط با کلیدواژه « Forest structure » در نشریات گروه « جنگلداری »

In order to properly manage the forest, we need tools that can be used to study the changes in the forest structure. In this research, the structure of degraded oak forests of Piranshahr and Sardasht in West Azerbaijan province were investigated. Characteristics of the stand were investigated in two one-hectare sample plot with dimensions of 100 x 100 meters in two different forest types, including Darsarvin Sardasht (30% canopy cover, coppice with standard) and Piranshahr Pardanan (90% canopy cover and all of trees were of coppice). Using 100% inventory and a set of indices based on the nearest neighbor, three characteristics of location, mixture and dimensions of trees were investigated.

The investigation of the structure was done by using the indices of density, diameter, height, basal area and trees location. As well as the indices based on the nearest neighbor in two sample plots were used. The structural variables of all the trees in the sample plot were measured separately for coppice and standard trees. The characteristics of the species, spatial coordinates, diameter at the height of 0.5 meters of the trunk, and height of all trees were measured. Three criteria of species density, basal area and canopy cover were also used for forest typology. To describe and quantify the structural features of forest stands in this research, indices based on the nearest neighbor were used. For this purpose, distance to neighbors, uniform angle, Clark and Evans, Mingling, DBH differentiation and CC differentiation were used. The calculations related to the structural characteristics of the examined stands were done using SPSS version 20 software and the calculations related to the structural indices were done using the Crancod software set (ver 1.3).

The Clarke and Evans index with values of 0.82 and 0.94 for Darsarvin and Pardanan, and uniform angle with values of 0.56 and 0.52, respectively, showed a cluster distribution pattern and random species distribution pattern in both stands. Mingling index shows that there is more mixture of neighboring trees in Pardanan (0.65) than in Darsarvin (0.38). The diameter difference index shows a greater difference in the half-meter trunk diameter of Pardanan (0.55) compared to Darsarvin (0.46). But the canopy differentiation index shows a greater difference in the canopy cover of Darsarvin (0.58) than in Pardanan stand (0.53). The results of the combined diversity index showed that the structural diversity in Pardanan (0.41) is higher than Darsarvin (0.36). This index shows that there is a low level of combined spatial, species and dimensional diversity in the two stands. Results are consistent with the situation of the two regions that are affected by destructive factors and limited regeneration. These results can be used for comparing structural characteristics of forests and determining the impact of human intervention.

The results of the composite diversity index showed that there is a low level of spatial, species and dimensional composite diversity in the two forest stands, and these results are consistent with the influence of destructive factors as well as the limitation of regeneration. Considering the difference in the stands in the two sample plots in this investigation, the results of these indices can be used as a basis for comparison with other similar forests and determining the amount of deviations caused by natural processes and human interventions. Also, it seems necessary to achieve a suitable management model and Silviculture practices in the forests of this region and determine the structure and planning based on the current situation using these indicators.

Several studies have been conducted to estimate stand volume in Hyrcanian beech forests (pure and mixed beech satnd type), so that different results have been obtained from these studies. Meta-analysis is a quantitative statistical method for combining the results of a set of separate studies that are all about a specific topic. In meta-analysis, by collecting data from many studies, the number of samples increases and therefore the range of changes becomes smaller, as a result, the importance of statistical findings increases. In meta-analysis, if there is homogeneity between the articles used, the model with fixed effects is used, and if there is heterogeneity between different articles, the model with random effects is used to combine different articles. Therefore, in a meta-analysis, a series of researches in Hyrcanian beech forests were examined. In this research, some arguments have been made about the reason for the difference in the satnd volume in different areas of the Hyrcanian forests. This is the first meta-analysis research in the field of stand volume in Hyrcanian beech forests.

Researches related to the topic of stand volume were searched in national and international databases without time limit until the winter of 2022. In this research, after a detailed review of numerous articles, the data (mean, standard deviation and number of samples) of 18 original studies related to the stand volume variable in Hyrcanian beech forests were used. These researches were published in the International Journal of Agricultural and Biosystems Engineering, European Journal of Forest Research, and Natural Areas Journal, Iran's Forest and Poplar Research (seven researches), Wood and Forest Science and Technology Researches (three researches), Iranian Forest Ecology (three studies), Forest and Wood Products (one study) and Forest Research and Development (one study)) were published. In this research, only the estimation of stand volume (not growth of stand volume) was considered. In some cases, the required data, such as standard deviation, were not available in the published articles, so these articles were excluded from the meta-analysis process, or in few cases, they were calculated by accessing the raw data of the authors. These data had different names such as stand volume, forest stand volume, and growth stand volume in forests with different structural characteristics in these articles. Due to the significance of the Cochran Q test (P≤0.05) and values greater than 75% for the I2 statistic, the random effects model was used for meta-analysis. To find the source of heterogeneity between studies, subgroup analysis was performed based on geographical regions (province) and stand composition. The results of a meta-analysis can be shown in the form of an forest plot, which is the most general and common method of displaying effect sizes. In this research, the software Comprehensive meta-analysis ver. 3 was used.

According to the significance of the Cochran Q test and the I2 index, the average stand volume was estimated to be 386.805 sylve/h (95% confidence interval: 334.92-438.68) for Hyrcanian beech forests based on the random effect model. . The lowest and highest amounts were 252.3 and 685 sylve/h respectively in the forests of Mazandaran. Most of the research was done in different places of beech forests in Mazandaran province. The subgroup analysis based on the province (geographical regions) showed that the highest value is based on the random model in the forests of Guilan province with the amount of 424.45 sylve/h (95% confidence interval: 277.57-438.46). The lowest was estimated as 285.63 sylve/h (95% confidence interval: 167.26-404.01) based on the random model in the forests of Golestan province. The meta-analysis of standing volume in the Hyrcanian forests based on tree stand composition showed that the highest value was based on the random model for the pure type of beech at the amount of 394.272 sylve/h (95% confidence interval: 277.510-688-417). The lowest value of 147/38 sylve/h (95% confidence interval: 325.94-444.34) was obtained for mixed beech type. According to the results of this meta-analysis, the volume of stands in the Hyrcanian beech forests in the pure type of beech is 125.9 sylve/h more than in the mixed type of beech.

The average volume of stands in Hyrcanian beech forests was estimated at about 386 sylve/h. The highest amount in the forests of Guilan is about 424 sylve/h. The highest amount is 394 sylve/h for the pure type of beech. So, in management plans to maintain the stability and proper tolerance of the stand, it is recommended to keep the volume of the stand at the average level. Estimating the average value of structural characteristics on a large scale provides quantitative information on the structural condition of forests to adopt a suitable and realistic policy.

The investigation of chemical, physical and biological soil properties in developmental stages could be an appropriate approach in low-altitude forest management concerning these ecological services. Investigating the changes in soil properties during the developmental stages of the low-altitude forest is of great importance in improving the ecological services. This research aimed to investigate the effect of different developmental stages of the mixed hornbeam stands on some physical, chemical and biological properties of soil in two seasons, autumn and summer (with a time interval of one year) in series number two of forestry plan of Shastkalateh, Gorgan.

35 half-hectare rectangular sample plots with dimensions of 50 x 100 meters were considered to identify the different developmental stages after the field visit. In each of the samples, the type of tree species, shrubs and the diameter at breast height were measured. Finally, using Feldman et al. (2018) index, three developmental stages of initial, optimal, and decay were determined for all samples and three replicates were considered for each stage. In each of these nine main sample plots of half a hectare, five micro-samples of 20 x 20 meters were selected; one of them in the centre and four others in the corners, then soil samples were taken from a depth of 0-15 cm in each micro-sample at summer and autumn. A total of 270 soil samples were analyzed.

The results of this study showed that there is no significant difference in the physical properties of the soil including sand, clay, silt and bulk density in the different developmental stages in the two seasons autumn and summer. But in both seasons, the soil moisture in the optimal stage was significantly higher than in other stages. Examining the chemical and biological properties of the soil showed that electrical conductivity, organic carbon, and the ratio of carbon to nitrogen, ammonium, and nitrate of the soil had significant differences between different developmental stages in the autumn. In the summer, acidity, electrical conductivity, percentage of organic carbon, total nitrogen, and microbial biomass of carbon, ammonium, and nitrate had significant differences between different developmental stages. The results of principal component analysis using the studied variables showed that, in general, the first and second main components accounted for 39.16 and 15.11 percent of the total changes, respectively. The acidity, electrical conductivity, and percentage of organic carbon, ammonium and nitrate had a high correlation with the first axis. Soil moisture, ammonium and nitrate had a positive correlation with microbial carbon biomass. While the variables of acidity, electrical conductivity and percentage of organic carbon had a negative correlation with microbial carbon biomass. Ammonium and nitrate also had a negative correlation with acidity, and electrical conductivity and organic carbon percentage showed a positive correlation with soil moisture.

Based on the results of the present study, it can be stated that in the low-altitude forest of the mixed hornbeam stand, the development stages had a significant effect on the chemical and biological characteristics of the forest soil. Although in other studies the significant effect of developmental stages on the physical properties of the soil has been reported, in the present study, the developmental stages had no significant effect on the physical properties of the soil. The results of this research contain valuable information about the seasonal dynamics of the soil characteristics of the low-altitude Hyrcanian forests in different developmental stages, which shows the relationship between the forest stands and the changes in soil characteristics over time.

In this study, the structure of Zagros forest stands was analyzed using neighborhood-based indices such as Clark and Evans, uniform angle, mingling, diversity of dimensions, diversity of combined structure, and distance to the nearest neighbor in two one-hectare (unprotected) sample plots in Chaharzebar and Barzeh forest areas (as a sample of the majority of Kermanshah province's forests). Clark and Evans index values of 0.87 and 0.88 for quadrupeds and ridges, respectively, and uniform angles of 0.51 and 0.5, respectively, revealed a spatial distribution pattern in both hilly areas and a species distribution pattern in random quadrants and the Barzeh region. The average mingling index values of 0.13 and 0.005 revealed that the Barzeh region had substantially lower species mixing than the Chaharzebar region. In addition, the mean diameters of differentiation indices with values of 0.55 and 0.38, and height differentiation with values of 0.2 and 0.19, were determined for Chaharzebar and Barzeh, respectively, indicating a minor height difference and the diametric superiority of Chaharzebar trees over Barzeh. In general, the structure of the forest in the analyzed regions has been significantly altered, and the findings of the hybrid diversity index revealed a low level of biological, species, and dimensional variety in the two studied forest stands.

In close to nature silviculture, dead trees have great importance because of their essential role in the conservation of biodiversity in forest ecosystems. In this regard, the amount (volume) of dead trees in pristine natural forests can be a guide for its maintenance in managed forests. One of the most important questions in recent years is how much dead trees can be recommended to retention in the managed natural forests. Related resources show different results for this variable. Therefore, in a meta-analysis, studies in Hyrcanian forests were collected and analyzed. This is the first meta-analysis for important structural factor in close to nature silviculture, dead tree volume, in the Hyrcanian forests.

This study includes design and search strategy, collecting articles and extracting data from them, include and exclude criteria and finally statistical analysis of extracted data. Dead tree related research was searched in national and international data base, including SID, Science Direct, Web of Science, Scopus, Google Scholar and IranDoc until May 2022. In this study, after review of several articles, data (mean, standard deviation and sample size) of 16 original studies related to the dead tree volume variable in Hyrcanian forests were collected that had 163 samples and the total area of the sample plots was 92.44 hectares. After extracting the data, Cochran's Q test and I2 index were used to evaluate the heterogeneity the studies and select the appropriate model for data analysis. To find the source of heterogeneity between studies, subgroup analysis was performed based on geographical areas (province) and tree composition. In this study, Beggs and Egger tests were used to investigate the publication bias. Data analysis was done with Comprehensive meta-analysis ver. 3.7.

The mean of dead tree volume was estimated to be 35.293 m3/h (Confidence interval 95%: 24.769 - 45.817) for Hyrcanian forests according to the significance of Cochrane Q test (p = 0.0001) and I2 index (99.735) based on the random effects model. Subgroup analysis showed that the highest dead tree volume was estimated based on a random model in the Golestan province forests as 50.520 m3/h (95% CI: 45.669 - 55.372). In this study, the publication bias test was not significant (p-value for Egger and Beggs tests was 0.28 and 0.24, respectively).

The average of dead tree volume in the Hyrcanian forests was estimated to be "average". Accordingly, the maintenance of at least 35 m3/h of dead tree in Hyrcanian-managed forests can be a guarantee for the preservation of the biological functions of these trees.

Structural properties of forest stand affect forest soil and soil characteristics. The purpose of this study is to investigate the changing of soil physical and chemical properties under different forest structure in Kurdistan province. At first, four one-hectare (with dimensions of 100 × 100 m) plots were selected in Baneh (two stands), Marivan and Sarvabad (one stand) and structural characteristics of stands were determined. Seven soil samples were taken from a depth of 0-10 cm in each site (a total of 28 soil samples) and the physical and chemical were measured. Results of one-way analysis of variance test show a significant difference in most of the physical and chemical properties of soil (except nitrogen and electrical conductivity) in the four stands. The results showed that forest stand with young coppice structure (with higher canopy percentage ) increased organic carbon (3.15%), absorbable potassium (5.37 mg/kg), absorbable phosphorus (10.5 mg/kg), electrical conductivity (483 d s m-1) and soil moisture content (9.95%) in compere of another site. The results of principal component analysis showed that the first and second components account for 90.27% of site changes and the first component includes electrical conductivity and potassium variables and the second component includes absorbable phosphorus, organic carbon and weight moisture. Considering the positive effect of forest stand with young coppice structure (with higher canopy percentage and higher tree density) on the forest soil, it is recommended to regenerate and develop the forest in coppice stands with a density of less than 150 tree in hectare.

The Arasbaran Forests are the main habitat of Caucasian black grouse (Lyrurus mlokosiewiczi Taczanowski) as one of the most important endangered avian species in Iran. Quantitative analysis of the structure and composition of woodlands provides an appropriate basis for conservation programs in its habitat. This research was conducted to quantify the structural characteristics of woody communities in the Caucasian black grouse habitats in Iran. For this purpose, after determining the absence and presence regions, three one-hectare plots in each region were selected, in which all trees were inventoried. Results revealed that the greater amount of relatively large trees (DBH > 20 cm) and the vast range of tree diameter were observed in the presence area. The mean comparison showed that the mean of DBH (11.1±0.6 cm) in the bird's presence was significantly greater than that in the bird absences region (8.5±0.7 cm). The coefficient of variation of DBH, tree size diversity, tree species richness, tree height class richness, and tree heights in overstory were similar in both presence and absence areas. However, the tree and shrub heights in the understory were significantly greater in the presence area (1.5±0.06 m) compared with the absence area (1±0.02 m). Moreover, the abundance of dead trees was significantly different in those areas. In conclusion, the habitats with the relatively higher dominance of Quercus macranthera Fisch. & C.A.Mey. and the presence of dog rose (Rosa canina L.) and black currant (Ribes biebersteinii Berland.) are favorable for the black grouse. The relatively homogeneous structure with the presence of large diameter oak trees and the least amount of fallen dead trees provides suitable conditions for this species. This should be considered in the reconstruction of bird habitats and the restoration of previously manipulated habitats.

Forest structure, as measured by the physical arrangement of trees and their crowns, is a fundamental attribute of forest ecosystems that its measurement can serve as indicators in ecosystem management. In this research, the horizontal and vertical structure of a part of the northern Zagros forests was studied. For this purpose, conventional region forests of Havare-khol village in Baneh city was selected and sixty 20×20 m2 plots in a grid of 200×300 m2 by randomized-systematic method were established in an area of about 345 ha. In each plot, diameter at breast height of all trees and coppices thicker than 1 cm, height of trees and coppices, two crown diameters, crown height and spatial locations of all trees and coppices were measured. SVS software was used to display the horizontal and vertical structure of the forest, and stand statistical indices were analyzed using SPSS software. Distribution of trees and coppices in the height classes showed a two-three storied forest structure in Havare-Khol with the highest abundance in the middle story and the lower abundance in the overstory. The highest distribution of trees and coppices in Havare-Khol forest were within 2-4 m height class and more than 84% of stems had less than 4 m height. Most trees and coppices were less than 10 cm in diameter, indicating a young forest for Havare-Khol with a low diameter distribution range, and a low abundance of thick and old stands in the forest. The horizontal structure of the forest showed large vacant patches and discontinuities of the canopy in the nearest villages that the amount of these empty spots is gradually diminishing as they approach the conventional region border. Also, the vertical structure of the forest shows that in the areas closer to the center of the village the trees and coppice shoots are more concentrated in the middle story and understory, and the greater the distance from the center of the village, the higher the presence of trees in the overstory. Overall, drawing the forest structure showed that with increasing distance from the center of the village, the diameter at breast height, height and area of canopy cover and coppice shoots increased.

The tree species regeneration is a critical process in the population dynamics of forests and significantly influences the composition of forest communities. Quantitative analysis of tree regeneration may provide baseline information for conservation and management strategies. Zagros oak forests have been subjected to dramatic changes in forest regeneration, cover and structure in recent decades. Zagros forests have critical national importance. These forests capture over one third of the country’s annual precipitation, and are the headwaters for 40% of the country’s rivers and streams which provide water to the dry central plateau of Iran. Given the national and regional importance of Zagros forests, it is extremely useful for restoration management to evaluate spatial distribution of tree regeneration. Disturbing of ecosystems, changes the dynamic of species and ecosystem processes. Ecosystems are therefore moving in a self-organizing way towards a more efficient use of energy/nutrients to the total energy input. This self-organizing of the ecosystem is an inherent feature of non-linear interacting systems. Techniques used to study non-linear systems could be able to quantify the structure of complex objects and spatial dynamic of plants.

The mathematical features of spatially complex systems are often fractal. Fractal has the potential to exposure a new way to understand and analyze such natural spatial phenomena, which are not smooth, but rough and fragmented to self-similarity. We investigated the spatial patterns of tree regeneration density and diversity in 126 plots (100 m2). The study was conducted at a preserved area (12 years) in Zagros forest of western Iran. We applied autocorelation methods to examine the spatial structure in distribution of regeneration. Fractal analysis was also used to characterize the complexity of the spatial patterns.

We found that preservation favored density and diversity of tree regeneration in this area. On the whole the variables have weak autocorrelation but regeneration density of C.microcarpa, total regeneration density, regeneration height and Shannon index are the variables which have the most autocorrelation. On the other hand, fractal dimension, representing the unpredictability of spatial patterns, is high for trees and regeneration. This implies that although spatial dependence exists, it is generally fairly weak.

These results revealed the scattered and homogeneous spatial distribution of trees and their regeneration. Indeed, our results showed a recovery of regeneration but not the spatial structure of it. It seems that conservation efforts must be continue to complete the recovery of regeneration and their spatial structure.

Forest structure is a key factor in growth, yield and how changes occur in the forest stands, and evaluating the structure of plantations can play an important role in improving afforestation and timely implementation of forestry treatments in each stand. This study aimed to evaluate structural characteristics of plantation forests in the Saib Tabrizi forest park located on Tabriz, after 25 years of planting have passed, and abandon its management.

For this purpose, after initial field surveys, three one-hectare plots were selected and based on quantitative indicators, the structure of each plot-sample was investigated. In each plot, structural characteristics of all trees (species type, diameter at breast height, tree height, canopy height, and canopy diameter) were measured and the distance method (based on nearest neighbor’s) were used to quantify stand structure. In order to study of stand structural some index including nearest neighbors distance index (density of trees), uniform angle index and Clark and Evans index (variety of location), Mingling index (species mixture), diameter and height differentiation indices (dimensional differences of trees), and complex structural diversity index (tree diversity) were used.

Based on the results, the average density of trees was 448 per hectare. In the studied sample plots, the average DBH was equaled to be 12.9 cm, the average height of the trees was 5.1 m and the average basal area was calculated to be 0.013 m2 per hectare. The highest abundance among the species belonged to the species of Pinus nigra with 50.4% and Robinia pseudoacacia 32.4%, respectively. The results of the uniform angle index showed that a cluster pattern in spatial distribution of trees, however Clark and Evans index showed a regular pattern. According to the Mingling index, the studied stands have relatively moderate mixing. The height and diameter differentiation indices showed that the dimensions of the trees had a slight difference, and have a homogeneous structure. According to complex structural diversity index, tree diversity was obtained at the low level.

In conclusion, it can be said that after nearly three decades of planting trees in this park, tree communities have maintained the homogeneity of their structure, and trees have moderate mixture. Therefore, it can be stated that the development of forest structure in the research area is slow. Hence it is recommended to increase the biological sustainability, silvicultural treatments are needed to increase mixture and heterogeneity of structure. The results of this study can provide objective justifications for the importance of consciously creating forestry strategies in the country's forestry as a missing link in the forest management.

Tourism in natural areas can affect the biodiversity, density and structure of stands and plants health. The present research aims at studying the effects of tourism on vegetation structure and species diversity in Noor Forest Park, Mazandaran province. To do so, the study area was divided into three main zones: without pressure, moderate, and high tourism pressures. Then, sampling was done with 20 sample plots of 20 × 20 m sample with random-systematic distribution in each zone (60 plots in total). Within each sample plot, trees, shrubs, herbs and regenerations were counted and quantitative and qualitative characteristics of all woody species were measured. The species richness, evenness and diversity indices were then calculated and the calculated indices and forest structural features were compared amongst the mentioned zones. Based on the results, diversity of forest floor flora in high tourism pressure zone was higher than other zones and there was no significant difference in woody species diversity among three zones, nevertheless a considerable reduction was seen in density of both woody and floor species. The lowest regeneration abundance was observed in high tourism pressure zone and the most, in medium tourism pressure zone. In zone without tourism pressure, average height and canopy of trees were more compared with the high tourism pressure zone. Also, most snags, the highest ratio of broken trees to total trees and the highest number of diseased and damaged trees were observed in high tourism pressure zone. In this zone, Alnus glutinosa, Populus caspica and Parrotia persica had the lowest vitality.

This study aimed to evaluate the structural characteristics of Quercus macranthera forests in the Arasbaran region, Hatam Mashe Si, Meshgin-Shahr. To achieve this, all trees and shrubs were full calipered in three one-hectare plots. Additionally, the structural characteristics were measured using the nearest neighbor’s method. To measure intensity of trees, several indices like nearest neighbor distance index (density of trees), uniform angle index and Clark and Evans index (variety of location), Mingling index and Shannon-Wiener index (tree diversity in diameter classes), diameter and height differentiation indices (dimensional differences of trees), and complex structural diversity index (tree diversity) were used. The results showed that Q. macranthera represented a relatively homogeneous structure in its main site, and the mean of distance to the neighbors was 2.59 m. The results of uniform angle and Clark and Evans indices showed that the spatial pattern of trees was regular. Mingling and Shannon-Wiener indices showed a low tendency of Q. macranthera to mix with other tree species so that the majority of trees were Q. macranthera. The height and diameter differentiation indices illustrated that the dimensions of the trees had a slight difference. According to complex structural diversity index, tree diversity was at the medium level. It can be concluded that the Q. macranthera communities have a homogeneous structure in a study region with a low mixture and single canopy layer. The information can provide the opportunity to monitor future changes in Q. macranthera communities in this region. To promote ecosystem stability, it is suggested to create heterogeneity of stand structure and support other tree species in this area.

Monitoring forest structure, to understand many issues in ecology and forest management is essential. In general, the term "structure" emphasizes the combination of tree communities in terms of specific characteristics. Monitoring forest structure is essential for understanding many issues in ecology and forest management. Today, many indicators have been developed for assessing the position and biodiversity of the trees, which simplifies the structural analysis of the forest. The use of these indices in constant sample units facilitates population dynamics studies over time and makes it possible to monitor the diversity of the location, dimensions, diversity of trees and height of the trees. Due to the smallness of these indicators and the possibility of comparing a mass at two different times, these indicators are a useful tool for achieving sustainable forest management. Combination indexes, uniform angles, diameters and altitudes are among the most important indices in the analysis of forest spatial structure in static studies. These indicators are preferable to other methods because of their simplicity in calculations and balancing accuracy. In this research, using a randomized random method, a rectangular grid of 200 * 150 * meters was used to identify the Gorazbon of Kheyroud forest in the city of Noshahr. Then, in order to study the structure of the forest species (beech, oak, hornbeam, alder, apple, lambs, lambs, almonds, and durum wheat) over a period of ten years, the uniform angle index, Ming-Ling blending, close The largest neighbor and the index of differentiation of diameter and height of trees were used. According to The results, Average indexes uniform angle index, mixing Ming Ling, nearest neighbor and the diameter and height dominate the index, in the first period and the end of the monitoring period was calculated) 0/598 and 0/525, 0/582 and 5/645 and 5/35, 0/762 and 0/720, 0/5521 and 0/591 respectively This represents a cluster random distribution pattern, an optimal mix of diversity and high density and the average dispute between the diameter and height of neighboring trees then the reference tree. In order to compare species diversity, location, and size, paired t-test was used. Paired t-test results showed that there is no significant difference between these indices before and after the period of monitoring (ie, the ten-year period). Also, the results of t-pair test for each species were proved, that there is a significant difference between the indices of differentiation of hornbeam tree before and after the observation. But there was no significant difference between the other species before and after the observation. This is due to the dominance of hornbeam trees in neighboring trees

Quantification of forest structure and its various components helps to better understand the forest ecosystem and supports its improved management. Here, the Gini index were used as a spatial distribution index for evaluating the structural diversity. The main objective was to analyse the stand structure and determine the necessary factors for the structural heterogeneity and homogeneity. This study was conducted in compartments 305, 306, 309, 310 and 311 in Gorazbon district, Kheyrud forest by means of a full calipering method. Then Gini index was calculated and finally the Lorenz curve was derived by using frequencies of stems, diameter class, as well as cumulative relative frequencies of trees and their basal area. The results showed Gini index values of 39.5%, 66%, 44%, 82% and 74% for compartments 305, 306, 309, 310 and 311, respectively. In addiiton, the diameter structure for 305 and 309 compartments was shown to be close to homogeneity, whereas it was close to medium for compartment 306 and close to heterogeneity for compartments 310 and 311. Finally the use of Gini index and Lorenz curve was concluded to he helpful in reclecting the near-real structural diversity in natural beech stands.

The study of forest structure is one of the basic requirements to achieve the objectives of close to nature silviculture. The purpose of this study was to identify the structural characteristics of coppice forest stands in Fandoghlou forest, Ardebil province. Three representative sites were carefully selected after detailed field survey. In each site, 3 sample plots with one hectare area (100×100 m) were established according to a random systematic design. In addition, in each sample plot, 25 subplots (4×5m) were determined for regeneration study. In each microplot, the frequency of regeneration was recorded in different diameter and height classes. Data were analyzed using appropriate softwares (Excel and SPSS). Results showed that, Fagus orientalis Lipesky, is the dominant species in one of the sites and in two other sites, beech accompanied hornbeam and hazelnut. The situation of stand structure and regeneration in site one and two were better than site three. Distribution charts of number in diagonal classes showed uneven-aged and irregular stands. Mean comparison of structural parameters in studied sites showed a significant difference at 5% confidence level for various sites.

This study was carried out in Noyjian forests of Khorramabad, the destructed and less destructed stands were investigated in terms of three structural aspects: species diversity, spatial pattern and dimension variation have been compared. For this purpose, at first based on the available information and see the forest closely, two classes of crown dense 35% and more than 35% were bounded. Then in each of this part, 10 (one-acre) sample plots were taken with the similar physiographic conditions. According to the results, the diversity in these stands is low, but in general, the diversity in the less destructed stands is more than the sparse stands. Among the species diversity indices, the Margalef index shows the most difference. In relation to the pattern of distribution, the mean aspect and uniform angle indices show similar results based on random distribution of most species in both stands. According to the dominant index these species (Quercus brantii, Acer monspessulanum and pears) are dominant and other species are defeated. In general, the mean of the differentiation index shows a large difference between canopy coverings in different stands, which is more than that in sparse stands. According to the result, in general, the structure of less- destructed stands is in a more favorable position in different aspects. Since the physiographic conditions of these stands are similar, human factors can be considered as the main cause of the apparent difference between these stands. Therefore, it can be concluded that in the reduction of these factors, protection and support of destructed stands, the condition of this destructed stands will be more desirable.

The aim of this study is to investigate the effect of fire on stand structure (qualitative and quantitative factors of trees) and regeneration of oak coppice forests, Kuhdasht city, Lorestan province. The study area with an area of 90 hectares is located at 5 km in north of Kuhdasht city. This area has been burned by a surface fire on 6 July 2005. In this study, A total of 60 square plots with an area of 400 m2 were taken in linear transect with 100 m interval. Two types of sample plots were used. Tree cover was measured in main plot. Herbaceous (%) and regeneration were measured in micro plots with an area 4m2. The unpaired t test results showed that the fire caused a significant reduction in canopy cover percent, individuals/ha and an increase in herbaceous cover percent, diameter at breast height, basal area per hectare and regeneration of oak trees in fire area. In general, it can be concluded that the fire caused making an even aged stand and had a negative and positive impact on quality-density and oak regeneration respectively.

This current research was investigated the long – term effects of fire on vegetation and regeneration of beech (Fagus orientalis L.) in the mountain forest in Lesakoti forests in Tonekabon city in north of Iran. In both of burnt and unburnt areas, 30 plots 1000m2 and in total 60 sampling plots were identified using random-systematic 100 m × 150 m grid and density and DBH of trees and density of shrub and regeneration were recorded. Results indicated that the fire has changed the forest uneven aged structure to irregular even aged structure in burned area, and by destroying of low diameter trees and establishment of more light demanding species instead of shade tolerant species, changed primary situation of the burned area. The fire has changed forest tree composition from pure stands to mixed stands as the species of Carpinus betulus, Carpinus orientalis, Acer velutinum, Acer platanoides, Acer cappadocicum, Acer campester, Cerasus avium, Fraxhnus excelsior and Quercus macranthera were appeared. The result showed that fire decreased tree density in the burned area (130.02 in burned area and 236.71 in unburned area). There was significant difference as total density of regeneration between burned and unburned areas (1765 in burned area and 1283 in unburned area), and for each species regeneration there was significant difference. There was significant difference in density of shrubs between two areas, so that density of shrubs in burned area (250.02) was more than unburned area (193.77). According to the conditions of the study area, the implementation of silvicultural operations can improve the regeneration composition and density condition.

In this study, some forest biometric parameters were studied to evaluate the decline severity in Tang-e Solak forest area in Kohgiluyeh and Boyerahmad province. Hundred plots of one hectare each were used. The Fierke method was used to evaluate the decline severity. In this method, crown condition classes (CCC) and Basal Emergence hole Classes (BEC) are divided into 6 groups. Finally Rapid Estimation Index (REI) was calculated by aggregating CCC and BEC. REI was then classified into tree classes for determining the dieback severity. The result of this study showed that 88% of broad-leaved trees are in weak severity, while only 12% include medium severity of decline.

By examining the forest structure not only the forest conditions such as species composition, story and succession are determined, but also the future of forest in relation to growth, species diversity changes, canopy cover and basal area could be predicted. The purpose of this study was to quantify the stand structure and forest stands dynamics through triangle structure method. The current survey was carried out in compartments 305, 306, 309, 310 and 311 about 150 ha in Gorazbon district of experimental Kheyrud forest. For this purpose, two full calipering periods were used. The frequency and stocking volume at each diameter class were then obtained. The results showed that there was not significant differences between two inventory periods about beech, hornbeam, and maple individuals and their volume by using paired t-test. Generally, due to subtle changes, it is concluded that a 10-year period is not appropriate to examine the considered factors. Therefore, it is necessary the changes monitoring is done by repeated inventories in successive 10 year periods. Therefore, it is suggested the monitoring methods and control of forest structure dynamics over times through reliable data, as a solution for the forest management practices to increase the quality and quantity of forest stands by management interferences in the nature oriented silviculture context are specially considered.