محمود زبیری

Biodiversity is important in human performance and interference in natural environments. Investigation on biodiversity in main forest communities makes the improved management of these valuable ecosystems possible. The aim of this research was the comparison of biodiversity in four major forest communities in Hyrcanian forests.  The four forest communities (i.e., Fagetum, Fageto-Carpinetum, Querco-Carpinetum, Parrotio-Carpinetum) were surveyed by full-callipering method in Patum District of Kheirood forest. Applying the collected data, the biodiversity of them were studied in three levels of trees, shrubs and seedlings. Biodiversity was studied among the mentioned three levels in each association and among the communities separately. The results showed that there was no significant difference among the applied indices (Simpson, Shannon-Wiener and Brillouin) in the study area. Also Shannon-Wiener index decreased in order from Querco-Carpinetum to Parrotio-Carpinetum, Fageto-Carpinetum and Fagetum. There was no significant difference among the associations in the biodiversity of shrubs. The diversity of shrub species in the study area is also independent of the diversity of tree species and seedlings. The study of Shannon-Wiener index showed that the studied communities are different from each other in terms of species diversity, which should be considered in the development of management strategies. Finally, it should be noted that in sustainable forest management should be sought to preserve the diversity of plant species and prevent its decline.

Forests and the environment play important role in providing income, food, energy, medicines and genetic resources, and a variety of essential materials for the well-being and living conditions of the people and the preservation of culture. In this research, an attempt has been made to elucidate the functions of forests and the environment in Iran and their links to food security and nutrition by reviewing documents and referring to statistics and data of national and international organizations. Direct forest and environment ecosystem services include the sale of wood products, fuel wood or firewood and by-products or   non-wood products. In this study, the statistics related to Iran's forests were briefly pointed out, which include revenues from the harvesting of wood and non-wood products, energy obtained from firewood in cooking for optimal use of food and the direct role of some  non-wood products in direct provision in the food system. Indirect forest and environment ecosystem services play a major role in the “availability” and “stability” components of food systems, including biodiversity, climate change, water regulation and quality, and soil and nutrient cycling conservation. Biodiversity makes production and livelihood systems more resilient to shock and stress including climate change. Climate change and climate diversity threaten the provision of a wide range of important products (timber and         non-timber) and forest environmental services. In this study, while examining the relationship between global environmental changes and food security, the strategies for overcoming the current situation were enumerated.

The use of land without considering landscape topography and climate of the region, can lead to disastrous consequences, such as erosion, desertification and environmental degradation. The present study aimed to investigate the landscape spatial pattern changes using ecological metrics in Chaharmahal Bakhtiari province between 1997 and 2011. After providing the land cover maps in four categories of residential, forest, rangeland, and agriculture, ecological metrics at the class level including class area, edge density, largest patch index, patch density and number of patches were analyzed. The results showed that according to the class area metric in the studied period, the rangeland area decreased compared to the other three land uses. The edge density metric for the four land uses increased, which means increase in the fragmentation of these land uses. According to the largest patch metric, the rangeland has been significantly reduced, indicating the fragmentation of this land use. The patch density metric has increased for all land uses, which is higher for rangeland. Also, the amount of the number of patches metric increased for four land uses, which is more evident for rangeland. In general, based on the findings of this study, rangeland had the highest degree of degradation and fragmentation during the studied period.

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 conservation value of Coarse Woody Debris (CWD), as critical microhabitat component, in forest ecosystems led to increasingly expand interests in researches about it. The scientific CWD information had gradually considered by decision-makers for implementing forestry planning. In this study, due to evaluate qualitative and quantitative characters of CWD and its proportion to live standing trees, full callipering method was applied. Data were collected from an unmanaged parcel (parcel no. 37, Gorazbon district, Kheyrud forest) situated in southern slopes of Caspian beech forests. The study site has never been under wood exploitation. The data of CWD (middle diameter ≥ 10 cm) and stand (D.B.H ≥ 7.5 cm) were measured using full calipering method. The results of this study illustrated the average number of live standing trees, snags, and fallen trees were 357, 8, and 26 per ha, respectively. Between all species, hornbeam had the highest volume proportion both in live standing trees and CWD. One fifth of total CWD volume was accounted to sangs and stumps and about half of the total volume was exposure in low degree of decomposition. CWD volume amounted 3.5% of total yield of site study. In summary, total CWD volume is lower than optimal value considered for CWD in temperate forests which sets alarms that any removal of CWD could bring irrecoverable consequences in site study.

Appropriate management of forest requires indices that can provide adequate information about forest structure condition and its changes with the least cost and time. In this research, the effect of tree marking on natural stand structure was evaluated in Gorazbon district of Kheirud forest using indices ofspatial and non-spatial distribution. For this purpose, 682 structural groups (trees) were studied from the lower up to the upper boundary of compartment in two rectangular plots. The results showed that the changes of some indices, including mingling, Uniform Angle Index, DBH dominance, DBH differentiation, Pielou segregation, Clark and Evans aggregation, stem per hectare, basal area and diameter at breast height were not significant. Also, the paired t-test results showed non-significant differences for Uniform Angle Index and DBH dominance, whereas the Mingling and DBH differentiation indices showed significant differences, in the two studied sample plot before and after the tree marking. According to the results of this research, one can conclude that the applied indices are able to show the changes in the stand structure over different time studies and they are suitable for comparison of stands. These indices could be useful tools for forest management in close to nature silviculture.

The quantitative description of forest structure is considered as one of the most useful working tools in modern forest management. This study aims at evaluating the optimal area of sample plot for correct and effective estimation of structural parameters of beech stands. For this purpose, a compartment with an area about 48 hectare in Gorazbon district in research forest of Kheirod, Nowshar, Iran was selected in which tree species and DBH of all trees with DBH > 7 cm were recorded. In addition, for stem mapping of trees, the location of each tree was obtained using azimuth and distance method. The square sample plots with different areas were laid out on simulated map of study area and nearest neighbor of spatial indices (spatial pattern index of Clark and Evans, mingling index, diameter differentiation index, relative mingling index) were then calculated in each sample plot. The comparison of resulted spatial indices in each of sampling schemes (1000, 1500, 2000, 3000, 4000, 5000, 7500, 10000 and 12500 m2 sampl plots) with calculated spatial indices for the whole of study area indicated that only spatial indices in sample plots with area of 12500 m2 did not show any significant difference with the spatial indices for the whole of study area. As long as the topographic and forest site conditions as well as management system do not change, horizontal structural indices could be investigated with one 1.25 ha sample plot, provided that this sample plot is not established in the margin of compartment and the forest road vicinity.

This study aims at analyzing spatial pattern and associations of Fagus oriantalis Lipsky in different vertical classes in intact beech forests. Data collection was done in 25 ha plot in Gorazbon district of Educational and Experimental Forests of University of Tehran. Species and DBH of all trees with DBH > 7.5 cm were recorded. The location of each tree was determined using azimuth and distance method in order to map the tree positions. Height of trees was calculated using diameter – height model developed for Gorazbon district. Trees were then divided in 4 Height classes: 25 m (U). Univariate O-ring statistic was used to analyze the spatial patterns of Fagus orientalis at different tree height classes, and the bivariate O-ring statistic was used to analyze interspecies spatial associations among these height classes. Programita software was used for all analysis. Results showed spatial pattern of Fagus orientalis in height class (S) was clustered. In height class (L) spatial pattern was clustered up to distance of 21 m and then changed to random pattern. In height class (M) spatial pattern was aggregated up to distance 8 meter and then changed to random pattern and in height class (U) Fagus orientalis showed random spatial pattern in all distances. Bivariate O-ring analysis showed positive correlation between trees at height class (S) and other height classes up to 30-40 m. Present study showed application of O-ring statistic in vertical structure analysis of forest ecosystems.

The aim of this research was to evaluate and select of appropriate indicators for different zones of Baghe shadi region where it have six different zones (restricted zone, protected zone, restored zone, inhibition zone, recreational zone and other uses zone). To do so, first top-down approach and Likert scale questionnaire was used for voting from 32 experts. After that using influence matrix, influence and importance of indicators were determined and the most important indicators as well. Then using system analysis and influence matrix, for the first five indicators of each criterion, influence and importance of indicators were determined in different zones and indicators were evaluated and then appropriate indicators were determined for each zones. Regarding to results of indicators evaluation, indicators related to area of forests and protective functions have the most importance and application in restored zone. Area of forests and other wooded lands, extent of area by forest type relative to total forest area, area of natural forests with healthy regeneration were appropriate indicators in restricted and protected zones. Also, Existence & implementation of management plan & protection for spectacular landscape area in region, extent of forest lands considered for recreation, accessibility for recreation and expenditure for access to tourism area were appropriate indicators in recreational zone.

To assess the diversity of woody species (as a major task to understand the changes in forest ecosystem), collection of appropriate qualitative and quantitative data is of particular importance. This study attempts to introduce the most appropriate sampling method for estimating woody species diversity in the northern Zagros forests. An area of 40 ha in Blakeh forest was selected, in which 40 quadrangular samples of one ha each in a 100 m × 100 m grid were established. In each plot a set of characteristics such as species, tree position, the number of trees and smallest/largest crown diameter were measured. All inventory data were processed in GIS to produce a dispersion map of trees. Different sampling methods (rectangular samples with 20 × 50 m, transect methods with 50 and 100 m length, quadrangular method with 10 × 10 m, 15 × 15 m, 20 × 20 m, 40 × 40 m sample sizes) were implemented in a 100×100m sampling grid. The %E2 ×T criterion was used to compare the results. In addition, quadrangular methods were analyzed using the Shannon-Wiener and Simpson diversity and the Margaleff and Minhinick enrichment indices. The quadrangular method with 40 × 40 m and 20 × 20 m sample size was shown to be the most appropriate method for estimating stem number per ha and percentage of canopy cover.

In this study, 50 hectare of mixed yew stand was structurally investigated across Gazoo forest, a study area between 1100-1300 m a.s.l located 50 km from Zirab town in Mazandaran province. All yew individuals above 7.5 cm D.B.H were full calipered by measuring their height and DBH. A transect of 20 ×100 m was selected to study the stand vertical structure. Within the transect, DBH, height, crown diameter and distance from origin of each tree were measured. The diameter distribution curve of yew stand resembled an even-aged stand, which was yet due to a long-term decrease of regeneration which resulted in absence of young yew individuals. The stand structure was two-story (three-story in thinning area), with Fagus orientalis and Carpinus betulus trees covering the overstory. Maximum height and DBH of yew trees were 30 and 2 m, respectively. Volume of standing tree was 593 m3 ha-1, which accounted for 17% of the total volume percentage within the stand.

To determine the Annual Allowable Cut (AAC) in agreement with sustainable development, presenting a comprehensive approach which considers the ecological indices, seems quite essential and inevitable. One of the principal and useful concepts for determining the allowable limits for environmental changes is Carrying Capacity (CC) concept, by which maintaining the key elements of the ecosystems. Therefore, present study addresses the determination of the AAC in Gorazbon district of Kheyrud Forest located in the Northern Forests of Iran applying the CC concept. For this purpose first, the site was classified into ecological homogenous units then the amount of increment was estimated for each unit. The analysis showed that there is no difference between the ecological units. Therefore, to find the real homogenous units with different ecological capability, units with the most similarity were integrated and finally the real homogenous units were distinguished. The results showed that Gorazbon district consists of two separated ecological units and in each unit the AAC estimated from the traditional method(4.90) is significantly different from the CC method(5.65 and 4.74) (p<0.01). For the parcels with different capability, we considered both upper and lower limit of CC to cover the heterogeneity. Regarding the comprehensiveness and fuzzy nature of the CC concept in making up the existing deficiencies and uncertainties in estimating the AAC, this method can be a highly practical alternative for determining the AAC in the forest ecosystems with the capability for wood harvesting.

The quantitative description of forest structure can be regarded as one of the most usable working tools in modern forest management. The study aims at analyzing the stand structure in unlogged beech forests using nearest neighbor indices. Data collection was done in compartment 319 with an area about 48 ha in Educational and Experimental Forests of University of Tehran. Species and DBH of all trees with DBH > 7. 5 cm were recorded. The location of each tree species was determined using azimuth and distance method in order to map tree positions. The nearest neighbor indices including Clark and Evans’s index، species mingling’s index (DMi)، Relative mingling index (S) and diameter differentiation index (Tij) were then calculated using Crancod ver. 1. 3 software. Using Clark and Evans’ index، the spatial pattern of trees in the study area was determined as clustered. The value of mingling index (0. 31) indicated low mingling of species in these forests. The mean value of Tij (0. 43) indicates moderate differentiation of trees regarding DBH، whereas S index (0. 44) which is greater than 0 implies species separation in the study area. This research emphasizes the application of nearest neighbor indices in studying the beech stands structure.

Hyrcanian forests are the most valuable forests in the north of Iran and industrial harvesting occurs only in this area. It is a productive region near the southern coast of Caspian Sea. In these forests mixed beech stands mostly shown uneven-aged structure that is managed under selection system. In order to determine the priority of uneven aged method not only from an ecological view, but also from other views, especially in economical view compared to other methods, should be prove this important by tools or methods. The growth models enable the simulation of stand development in alternative management schedules and select finally the best method. Nowadays sivicultural tendency has been applied here. 768.4 ha unmanaged forest of Gorazbon district in Kheyroud educational-experimental forest was studied using 258 permanent sample plots. The models were used to optimize the stand structure and the alternatives in which various initial stands should be converted to the optimal uneven-aged structure. The model set consists of individual-tree diameter increment model, individual tree height model, survival model, and a model for ingrowth. The models indicate that the annual volume increment of the forests ranges from 2.5 to 7 m3ha-1a-1 in uneven-aged management, depending on species composition. The models and analysis of this study indicate that the uneven aged forest is more practical and superior than other methods (young even-aged stand, mature even-aged stand, and two-storied stand) in forest conversation and economically wood production.

The oriental beech constitute one third of northern forests area and stocking volume in the north of Iran. These stands obseve in pure and mixed. In order to properly management which guarantee sustained yield, it is crucial to collect basic information including stocking (volume and stem number), tree growth, diameter distribution pattern, diameter-height relationship, diameter-volume relationship and models estimating wood production. This study carried out in the Gorazbon district in Kheirud forest with an area around 934.24 ha.Volume increment and stem number were measured directly using permanent sample plots. A steady state variable of DBH used for estimation of tree height and volume. Wood production was estimated by wood production models. Results showed that, with a fraction of 31% of all individuals, beech allocated 57% of standing volume in the Gorazbon district. The total stem number of beech trees were 70777 and 71567 in the years 2003 and 2012 respectively. Mean stem number of beech was 9203 and 9308 tree per ha in the years 2003 and 201 respectively. Standing volume of the species was increased from 192 sylv per ha in 2003 to 197 sylv per ha in 2012. Total stem number increment and total volume increment were 116203 stem and 115301 sylv,respectively. Analysis showed the Prodan model as a best fit to DBH-height.

Sustainable Forest management is process that includes planning, implementation and monitoring. This process calls for criteria and indicators framework. On the other hand, forest ecosystems are increasingly considered as resources that must be managed for a wide range of ecological, economic and social values. These changes need criteria and indicator framework by which sustainable multifunctional forest management can be monitored. The Aim of this study is to develop criteria and indicator frameworks for ecological function including conservation, protection, conservation, and recreation function. For this purpose, Analytical Hierarchy Process and experts’ opinions were used and initial criteria and indicators were weighted. Final framework consists of 7 criteria, 25 indicator and 29 verifiers. Formulating these criteria helps monitoring the forest’s functions and can be used in determining, measuring, analyzing and assessing the sustainability of the studied area.

Hyrcania is a productive region near the southern coast of Caspian Sea. Her forests are mostly uneven-aged beach-dominated hardwood mixtures. There is increasing willingness to treat these forests without clear-felling, following the ideas of continuous cover management. However, lack of growth and yield models have delayed this endeavor, and no instructions for uneven-aged management have been issued so far. 768.4 ha virgin forest of Gorazbon district in Kheyroud educational- experimental Forest was sampled using 258 permanent sample plots in which two inventories was done. This study developed a set of models which enable the simulation of stand development in alternative management schedules and select finally the best method. The models were used to optimize the stand structure and the way in which various initial stands should be converted to the optimal uneven-aged structure. These models firstly developed without site index and age. The model set consists of individual-tree diameter increment model, individual tree height model, survival model, and a model for ingrowth. Logistic model fitted with binary logistic regression analysis was used to model the probability of survival. Non-linear mixed-effects modeling was used in height and diameter increment modeling. The predictors used in survival and increment modeling described the influence of tree size, competition and species. A common model was fitted for all species, using indicator variables to account for any species effects. Competition was described by stand basal area and basal area in larger trees. Competition variables were not included in the tree height model since they would result in instantaneous (and illogical) changes in predicted tree height in simulated thinning treatments. Within the models individual-tree diameter increment model, individual tree height model, survival model had high accuracy, Fagus orientalis and Quercus casaneifolia species had highest incremental diameter between species. In the end, using of growth models have advantages and disadvantages in planning and forest management that aware of this importance can be taken correct and logical decisions.

There are natural and human threatening factors of forests sustainability. Deforestation human factors include grazing, fire, land-use, mining operation, wood smuggling and release of waste in the forest. There are very high harmful effects of livestock grazing in forest. In this study effects of livestock grazing were investigated on occurrence, diversity and changes in natural regeneration groups. These regions in this study consist of Bonjehbon and Patom corral were located in Patom district in the Kheyroud Educational and Experimental Forest which belonged to University of Tehran. For this purpose samples were collected by moving from each corral in four routes as transect until custom unit boundary. There were determined 2×2.5 (5 m2) plots in each regeneration group and was determined woody and herbage species in those plots. Diversity and evenness indices were calculated by using Ecological Methodology software at 500 m distances from corral. The results show that the most seedlings are Carpinus betulus and Acer velotinum which forms main species in this region. Graph change species showed reducing trend of the frequency of C.betulus and A.velotinum species while increased abundance of F.orientalis by increasing distance from corral. Rising pattern was observed in the diversity and evenness factors by increasing distance from corral. Dominant herbage species include Oxalis acetosella, Rubus fruticosus, Sambucus nigra, Euphorbia amygdaloides, Pteridium aquilinum, Oplismenus unulatifolios and dominant woody species include D.lotus, C.betulus, Crataegus Spp, Mespilus germanica, Acer cappadocicum, Parrotia persica and Prunus divaricata at closer distances to corral. High diversity of woody and herbage species showed severe degradation at the regions near the corral which has led to appearance invasive species.

Quantitative, qualitative and structure data are vital for forest management at Zagros region of Iran. For this study, a site (40 hectare) at Blake forest located at Armardeh village of Baneh township was selected and 100 percent of the trees were measured, using 25 x 25 m. sampling plots. In addition to location of the trees in relation to the plot's corner, trees characteristics, including diameter at breast height (dbh),total height, crown height and crown diameters (biggest and smallest diameters) were measured at each plot. In order to identify the appropriate sampling method, for different methods were applied at 100 x 100 inventory net, consisting of: random sampling at three levels of sampling plots (40, 50 and 60 numbers, each at 10 R. area), and systematic-random at three levels of sample plots area (5, 10 and 20 R.), systematic-random with rectangular sample plots at two levels of area (10 x 50 and 20 x 50 m.) and transect 50 m. (length). The statistical methods of Anova and Duncan t were used to analyze the trees characteristics data and the %E2*T criteria to determine the appropriate inventory method. The horizontal and vertical structure of the forest was showed in 25 x 25 m. sample plot, using SVS software. The results showed that structure of Blake forest contains of two layers, in which Quercus infectoria and Quercus libani (average height of 7 and 6 m., respectively) make the over story, and Crataegus azarolus and Acer cinerascens (average height of 5 and 4.5 m., respectively) make the under storey. Furthermore, for diameter measurement (29222), transect and for total height (6048) and crown height (6668) measurements, Systematic –random with 5 R. sample plots at 100 x 100 sampling net system, recognized as the best inventory methods. Overall, the systematic-random inventory method with 5 R. sampling plots at 100 x 100 sampling net system is suggested to determine structure and measure characteristics of coppice and aged forests of Baneh township of Kurdistan province of Iran.

One of the main and important knowledge for forest management and its optimal and sustainable utilization is to determine its trees volume and number and its production potential. Actually, future forest management is based on its inventory and information. Thus for a precise planning its required to have information about forest standing stock volume and increment, distribution of diameter classes curve and spices structure. Determination of annual allowable cutting is required for wood utilization planning and management, based on stands volume increment data. The research was conducted in Gorzbon district (934.24 ha) at Kheyroud Educational- Experimental Forest (Caspian region of Iran), using 258 permanent sample plots and applying the directed method of inventory to measure volume increment and trees number two times with nine year interval. Results showed that average trees number and stocking volume per hectare were 298.15 and 335.8 sylve in 2003 and 290.14 and 367.7 sylve in 2012, respectively. Although 31% of the forest tree number belonged to Fagus orientalis, but 57% of the standing stock volume belonged to this species. Volume increment was 4 sylve/ha/year and average trees number growth was 5.8 ha/year. Overall, the beech species had the greatest volume increment. In fact, such huge research area and data analysis was carried out for the first time in Khyroud forest and the results showed that applying permanent sample plots method provides essential and precise information and data for measuring forest increment

The aim of this research was to determine the number and volume changes after the implementation of a 10 years forest management plan period and comparing of these changes with the aimed purposes. Inventories have been done systematic random sampling in 1000 m2 area plots. Diameter at breast height، control trees height and quality of first 6 m trunk length of trees with dbh more than 42. 5 cm is measured and estimated. Volumes of inventoried trees were calculated based on forest management plan Taryf. To compare the mean volume and number of trees per hectare in the two inventories volume table، t test was aplicated. In order to compare trees height curves at the beginning and end of period، cloud points of control trees was drawn and then modeling with regard to it. The results showed that during the implementation، mean volume has increased 10 sylves per hectare and 47 trees has decreased in hectare، but these changes were not significant regarding to t test (d. f=32، P<0. 05). After implementation، the height curve of tress and volume of trees with high degree of quality has increased. Percent volume per hectare of beech species is passed from planned mode (ideal mode) and the species hornbeam and oak nears to ideal mode. The other species have not only failed to approach the ideal goals، but also we are far from it. Reforestation rate performed is almost 50 percent of planned.

In this research، we tested biasedness of canopy cover and density estimation of forest trees and shrubs by the use of line sampling method. For this aim، locations and crown width of all trees and shrubs with crown width more than 10 cm in a 53 ha forest area in Ardal located in Chahar-Mahal and BakhtiariProvince were recorded. Then، 100 segments of line transect with various length (50، 100، 150، 200، 250، 300، 350 and 400 meter) were sampled، and this procedure was repeated 100 times. We used ANOVA to see if there is any significant differences between the estimated forest density and canopy cover with the different transect length. Results showed that، there is no statistical significant difference between various transects length for both variables. Also، as could be expected، by increasing the length of transects، the coefficient of variation was decreased and this decrease were negligible for transects longer than 200 m. This means no more precision could be achieved by more effort on measuring sample lines longer than 200 m. Analysis showed that the line transect sampling method is biased (over estimate) and the average relative bias were between 4-6 and 6-10 percent for tree density and crown coverage، respectively. Based on results، it can be claimed that، by considering the ease and speed of transect sampling method، the bias of estimates are negligible.

Mountainous forest communities of Irano-Turanian vegetation region are characterized with Juniperus excelsa. These forests have involved too many changes in the past and nowadays mostly are not integrated. But there are still some dense or broad stands. In this research، we have studied such these communities and their ecological properties in north of Tehran to northwest of Semnan province. A data set including floristic data according to Braun-Blanquet method and environmental variables were provided. To classify the vegetation، TWINSPAN and analyzing vegetation data with JUICE، and to investigate the species-environment relationship، ANOVA and Ordination (CCA and PCA) was used. According to the results، the vegetation was classified into six groups which were specific in floristic composition and ecological characteristics، and were described by their site properties، constant and indicator species. These groups took placed in three forest communities: Juniperus excelsa - Rhamnus pallasii، J. excelsa - Cotoneaster nummularius and J. excelsa - Lonicera iberica. The first one is significantly related to lower altitude and soils with poor nitrogen and organic matters، the second community is interested in upper lands and nutrient soils with a high saturated water capacity and the third one comprises stands impressed by the moist climate of the Hyrcanian region.

Distance sampling methods are extensively used for forests management of Zagros region of Iran. In the present study، estimation of quantitative characteristics of sampling methods، including individual، nearest neighbor، second nearest neighbor، compound and joint point، were studied and compared. The individual sampling method was examined، using the estimators of Morisita، Byth & Ripley and Cottam et al. and the nearest neighbor method was assessed، using the estimators of Byth & Ripley and two predictors of Cottam & Curtis1 and Cottam & Curtis2. Location of total trees and shrubs of a 53 hectare forest stand at Ardal city of Chaharmahal and Bakhtiari Province was recorded. Having the actual trees density and canopy cover percentage، as well as their estimated values، the bias of each replication was obtained. Difference between the bias and the actual values (for bias test) by one-sample t-test method and analysis of variance by Games Howell test، were studied. The results showed that the differences between the distance sampling methods in respect to mean trees density per hectare were significant، except for the nearest neighbor method، using the Cottam & Curtis1 estimator، which was not significant، whereas in respect to mean canopy cover percentage، the differences were significant، except for the second-nearest neighbor and the combined methods. According to the results of this study، it is suggested to use the Cottam & Curtis1 method for estimating the density and to use the compound sampling and the second nearest neighbor methods for estimating the canopy cover percentage.

To study the frequency distribution of the data for the height of trees in uneven-aged stands in Gorazbon forest and its modeling، some statistical distribution were used. The utilized data belong to 196 trees (Fagus orientalis، Betulus carpinus، Quercus castaneifolia، Alnus subcordata، Acer velutinum etc.) that were extracted from the data related to the forest management plan of Gorazbon district located at Khyroud forest. The range of the trees’ height measured was between 5 and 51 meters which is an indication of height variable in the northern forests. After initial calculations، four distributions Weibull، Gamma، Normal and Lognormal for frequency distribution modeling of height variable were selected and related pertinent calculation were done. The results of Anderson-Darling test and P-P plot showed that lognormal distribution is not an appropriate model for frequency distribution modeling of trees’ height. Among the other three distributions، Weibull، Gamma and Normal are respectively more suitable.