کامبیز طاهری آبکنار

Chestnut (Castanea sativa Mill.) is one of the native species of Guilan province. Due to fungal diseases and animal grazing, as well as the high amount of unhealthy seeds, native chestnut in vitro culture is one of the effective methods for mass production of this endangered plant. The aim of this research is to determine the optimal culture medium for chestnut tree regeneration through tissue culture. The culture medium used in this research includes GD (Gresshoff & Doy), DKW (Driver and Kuniyuki Walnut) (1 mg/liter BA*) and (Murashige Skoog) MS (half nitrogen concentration) with three different hormone combinations (1 mg/liter + BA 0.1 mg per liter TDZ), (0.5 mg/liter TDZ), and (1 mg/liter + GA3 0.1 mg/liter BA). For in vitro culture of chestnut, lateral buds of one-year-old plants grown in the greenhouse were used. One-way analysis of variance (ANOVA) was performed to investigate the effect of culture media with plant growth regulators on explant length, number of leaves, and stems. The results showed that the length of explants has a significant difference in culture media. No significant difference was observed in the number of stems and leaves. The results of the comparison of means using Tukey's test showed a significant difference between the length of explants in DKW medium and other media. DKW medium with 1 mg/liter BA was found to be the best medium for regeneration and longitudinal growth of chestnut explants. In the present study, in vitro culture of Chestnut is introduced an effective method for mass production of this species.

The main purpose of this study was to determine the quantitative and qualitative characteristics of maple trees in the plantation of Lomar Asalem,. The measurement and comparison of quantitative and qualitative characteristics of maple trees and regeneration status in plantation and natural forests and compared to other species is concerned. This study was conducted in Maple plantations at the age of 25 based on a systematic random sampling method with 30 sample plots of 400 m2. The results of t-test showed a significant difference between the number of trees per hectare, basal area, volume, slenderness coefficient and diameter growth of the maple trees in the two areas. However, there was no significant difference in the mean height of trees in the two regions and their height growth. In terms of qualitative characteristics, there was no significant difference in the trunk health of maple trees in the two areas. However, there was a significant difference at the level of 0.05 compared to the trunk form of these trees between the two areas. Significant differences were observed in the crown symmetry of the maple trees in the two areas, but there was no significant difference in the crown health and vitality of these trees. Regeneration density in the natural forest was higher than in the plantation. While the frequency of healthy seedlings and single trunk seedlings in the plantation was significantly higher than natural forest. Plantation in the area had a suitable condition in terms of quantity and quality than natural forest.

The aim of this study was to study the effects of altitude and slope factors on beech natural regeneration around dead trees in Siahroud forests of Guilan province. In order to conduct this research, 45 dead trees were selected using selective sampling method. Then, around the standing dead trees, a circular plot with a radius of 5meters and around the fallen dead trees, a rectangular plot with 4meters width (2meters from two sides of each log) were measured. Inside each plot, regeneration frequency, slope (in three classes of <30, 30-30 and > 50%) and altitude (in three classes of <700, 700-1500 and >1500 m) were measured. In order to compare regeneration in 50m distance from dead tree, the measured variables were collected in samples with the center of healthy trees with the same DBH. The results showed that the regeneration frequency of all tree species around dead trees was higher than around of healthy trees. The ANOVA test showed that there is a significant difference between the regeneration frequency in different classes of altitude and slope. Also, with increasing altitude and slope, the regeneration frequency of around healthy and dead trees was decreased. The results showed that physiographic factors have an important effect on the tree regeneration around of dead trees.

In this research, morphological, physiological and biochemical of 6 tree species in industrial Foolad Mobarakeh of Isfahan region at different irrigation intervals (seven, 14, 21 and 28 days) were studied in a completely randomized design and factorial in 2019. Survival, height, diameter, crown characteristics, photosynthesis, transpiration, stomatal conductance, water use efficiency, proline, and whole leaf chlorophyll were evaluated. The results of comparing the means showed that with the prolongation of irrigation cycles from once every seven days to once every 28 days, the survival rate of species and morphological traits such as height, diameter, and crown of the species decreased. Physiological and biochemical characteristics under the influence of species did not differ statistically significantly, while increasing the irrigation period from seven days to 28 days showed dramatic changes in these characteristics. Photosynthesis, stomatal conductance, transpiration, water use efficiency and total leaf chlorophyll were highest in irrigation cycle once every seven days and minimum once every 28 days, while leaf proline content had the opposite trend so that the lowest amount in the irrigation cycle once every seven days and its maximum amount was observed in the irrigation cycle once in 28 days. There was no difference between species in terms of physiological parameters. Generally, the results showed that the species Caucasian nettle tree, chinaberry and black locust have good performance in irrigation periods. Although it has been determined that the best irrigation treatment is once every 7 days, but 14 and 21 days also have high survival rate and can be used to reduce water consumption‎.

With the registration of Hyrcanian forests in UNESCO and increasing environmental sensitivities, these forests are in a state of conservation. The aim of current study is to investigate the effects of conservation on the structure, biomass and diameter distribution of mixed beech forests of Asalem of Guilan province. For this purpose, two protected and unprotected parcels were selected in a series five of watershed-12. In each area, 50 sample plots were accomplished by randomized systematic method and the diameter and height of all trees in the plots were measured. After calculating the common quantitative indicators, aboveground biomass of trees in the two stands was estimated using allometric equations. Then, the diameter distribution of trees in the two regions was modeled using eight probability distribution functions. Based on the results, the average number per hectare, basal area and volume of trees in non-conserved stands were calculated significantly less than the conserved stand. The biomass of the non-conserved area was 75.25 tons per hectare less than the conserved area. Among the distribution functions used, Johnson and beta functions in the conserved stand and Johnson and gamma in the non-conserved stand showed the best fit with the diameter distribution of the trees. The results of the this study showed that conservation had a significant effect on the biomass structure and diameter distribution of trees and lack of conservation had the greatest negative effect on low-diameter trees.

Dust storms are a major source of solid particles in the world that significantly impact air pollution and human and environmental health. Generally, trees and plants not only improve air quality by absorbing airborne particles on the surface of their leaves, but also they are affected by the accumulation of fine particles on their leaf surfaces. In this study, the uptake of fine dust by some dominant forest species of the Zagros region (Quercus Brantii Lindl., Q. libani Oliv., Q. infectoria Oliv. and Pistacia atlantica Desf.) was evaluated in the North Zagros Forests of Iran. For this purpose, soil, leaves and microdust on tree leaves were sampled by using a random systematic sampling network in the forests of Marivan County, Kurdistan province. The leaf ultrastructure of these species was examined by electron microscopy (SEM). Elements in the soil of the area and microdust deposited on the leaves of the trees were evaluated using the EDS (Energy Dispersive X-ray Spectroscopy) system and atomic absorption spectrometry. Finally, the ability of each hectare of forest to absorb fine dust was derived. Results showed that the leaves of all three oak species as well as wild pistachio are structurally different, which plays a distinct role in the deposition of microdust on tree leaves. The highest amount of microdust uptake by leaves was observed for Q. Brantii (0.012 g per leaf), followed by Q. infectoria (0.006 g per leaf) and Q. libani (0.005 g per leaf). In contrast, the lowest amount was observed for P. atlantica (0.0015 g per leaf). Based on the results, the amount of deposited dust in one hectare of forest in the study area with appropriate coverage (400 units per hectare) was estimated at 87.7 kg. The results of EDS test showed that the tested soil samples did not contain radioactive elements as well as heavy, toxic and dangerous elements. The results of the current study indicate the notable role of forest trees in the purification of air polluted by microdust as well as the the difference between species in their ability to absorb microdust.

In most parts of the Zagros, the structure of coppice oak stands is very fragile and unstable due to the lack of diversity in the horizontal and vertical profile. The aim of this study was to evaluate the effect of tending operations on the structural characteristics of Brant`s oak in Chegeni forests of Khorramabad, Lorestan province after 3 years. The study was conducted in a randomized complete block design with three replications with four treatments of light, medium and heavy thinning, which were thinned by 10, 20 and 30% of the basal area of the sprout-clumps, respectively, and the fourth treatment as a control. Measurements of quantitative variables were done. To investigate the effect of tending operations on dominance and dimension differentiation indices in the studied stands, the dominant and three neighboring sprouts in each sprout-clump were selected separately in different treatments and the quantitative characteristics of height and diameter of dominant and neighboring sprouts were measured. The results showed that due to tending operations, dominance and dimensional differences (collar height and diameter) indices of sprouts in heavy treatment were significantly higher than other treatments. Based on this, it can be concluded that heavy thinning treatment has been able to help improve the structure of the studied stands. Studying the effectiveness of other structural variables can help to identify the optimal thinning treatment. Also, this study emphasizes the importance of structural characteristics as a suitable tool for the management of oak coppice stands in order to help their sustainability.

Spatial patterns of trees and their interactions specifically reflect mortality, gap creation, resource use, and also determine population dynamics such as seed dispersal, understory development, initial survival and establishment, growth, and competition. In this study, three one-hectare sample plots in the three stages of early development, maturity and decay were selected in an untouched mixed beech forest in order to consider competition of trees from different height stories along developmental stages and all trees with a diameter at breast height (DBH) larger than 7.5 cm by species were measured based on chest diameter, height and determination of cartesian coordinates using distance-azimuth method. Then, these stems data were first divided into three groups (lower, middle and upper stories) depending on their location in the vertical strata. The spatial patterns and spatial associations were analyzed among different tree height classes using univariate and bivariate Ripley’s K-function. Results showed that spatial pattern varied with canopy strata and scales in different development stages. Positively spatial associations of Fagus orientalis at upper and lower stories in initial and optimal staged and also among F. orientalis at upper and middle stories in decay stages influenced by shade-tolerance characteristics, seed dispersal limitation and the role of larger nurse trees as a shelter of small trees. Competition for resources was observed between Fagus orientalis at the middle story and Carpinus betulus at upper story in the all development stages. Recognizing spatial pattern and natural events guided by nature over time are necessary to carry out targeted forestry operations and In proportion to the evolutionary stages of forest stands.

Quercus macranthera is extended in forest areas of the upper elevations in north of Iran and play an effective role in conserving soil and water infiltration. The biggest problem in the regions is livestock grazing and forest dwellers. The aim of this study was to study effects of protection on the quantity and quality characteristics of Persian oak(Quercus macranthera) in Roudbar forests of Guilan province.

In total, 40 plots of 1000 m2 (20 plots in protected area and 20 plots in unprotected area) were collected using randomized systematic method and grid sampling of 100 × 100 m. In each plot, number and type of tree and shrub species, diameter in breast height, height, crown position and trunk quality were measured. Also, a micro-plot of 100m2 in center of plots was used to calculate regeneration.

The results showed that density of trees, the average of diameter at breast height, total basal area, plant height, volume and regeneration were significantly were higher in protected than unprotected areas. There were no differences in other tree species. Density of barberry (Berberis vulgaris L.), Crataegus microphylla K. Koch and cherry plum (Prunus divaricata) were significantly higher in unprotected than protected area. Also, quality of crown and trunk were better in protected than unprotected area. Study of diameter classes in structure triangle showed that protected area located in irregular section and degraded area located in small-medium diameter section.

As Quercus macranthera trees play an important role in upper parts of the forest, maintaining this valuable species and continuity programs of livestock and human emersion is essential.

Importance of probability distribution functions in natural resource studies is increasing due to their effective roles in better understanding of vegetation structure and providing conceptual models of quantitative indices of plant species. The present study was performed to model the distribution of height and canopy area of Cionura erecta L. shrub, using probability distribution functions in Chahar-Tagh forest reserve in Chaharmahal and Bakhtiari Province. Height and crown cover (the largest and smallest diameters) of the studied species were measured by a strip meter in 35 sample plots of 10r area. The area of canopy cover was calculated by considering the crown shape of the studied species as a circle. Normal, Log-normal, Beta, Gamma, Weibull and Exponential probability distribution functions were used to model the height and canopy cover of the studied species and their goodness of fit were examined by Kolmogorov–Smirnov and Anderson Darling tests. Results showed bell-shaped distributions skewed to the right for height classes and in the case of the canopy cover it was decreasing. Beta and Gamma distribution functions were identified as the most appropriate functions for fitting to the height curve and Log-normal and Weibull functions were the most suitable ones for modeling the canopy cover. The present study showed that the quantitative characters of the studied species are far from a normal distribution under the influence of human activities.

In recent years, blight or boxwood blight, caused by a fungus, has spread from Western Europe to the Hyrcanian forests. In this study, the aim is to investigate the effect of breeding operations that reduce the humidity and temperature of these populations in controlling this disease.

For conducting a surface study equivalent to 3 hectares in series 1 of Gombl in Lahijan forests was selected, part of which was intact and as a control and part also had a forestry plan. All trees in two stands by 100% measurement method and variable diameter equal to chest for all species and small variables equal to diameter, collar diameter, height, number of reproductions in three classes as well as qualitative variables of trees Boxwood was recorded and analyzed statistically including the percentage of leaf freshness, branches and crowns of trees.

Based on the results of quantitative variables of canopy diameter, height, cross section and number of regenerations in the height class less than 1.3 m and the vigor of leaves, branches and trunks of boxwood trees in the managed massif were evaluated with better conditions. Only the number per hectare of total reproductive area in the control area was better.

According to the results obtained in this study, it can be said that management practices in the populations infected with boxwood blight by reducing the moisture trapped under the canopy of trees, prevent the spread of disease and resistance of rootstocks to this disease Increases.

This study was carried out to study the habitat characteristics of Persian juniper trees due to the topographical factors and site exposure in Spiro forest habitat, located at Damghan County. Inventory done by systematic method (Net dimensions: 300×400m). Trees number and diameter at breast height in 10 R area sample plots were taken. Then, the topographic factors effects on some of the growth variables of Persian juniper stands such as basal area and number per hectare were evaluated using stepwise regression model. The results showed that three indices of aspect, site exposure and topographic wetness had a positive and significant correlation with the number of hectares of trees. Also, elevation from the sea level, site exposure and roughness had a positive and significant correlation with trees basal area variable per hectare. According to the results, the most correlation between cypress quantitative characteristics, including number per hectare and its basal area, was obtained by topographic factor of site exposure.

The present study aimed to assess the effect of canopy combination of beech trees and mixed species (beech-hornbeam-maple, beech-hornbeam, beech-maple and pure beech) on microbial indices and soil nutrient stockscharacteristics in Mazandaran Province, north of  Iran. Leaf litter sampling was done by using litter traps and soil samples (30 × 30 × 30 cm) were taken in each of the stands with five replicaties under the canopy of beech trees. Characteristics of litter (organic carbon, total nitrogen, carbon to nitrogen ratio, phosphorus, potassium, calcium and magnesium) were measured. The physical, chemical, biochemical and microbial properties of soil (bulk density, Sand, silt, clay, pH, EC, organic carbon, total nitrogen, carbon to nitrogen ratio, sequestration of organic carbon, total nitrogen, phosphorus, potassium, calcium and magnesium, ammonium, nitrate, microbial respiration, metabolic and microbial quotient) were also investigated. The results showed that beech-hornbeam-maple stand had the highest pH, nitrogen sequestration, phosphorus, potassium, magnesium, microbial biomass of carbon and nitrogen, and microbial respiration. Also, the highest amount of soil carbon, carbon to nitrogen ratio, carbon sequestration, metabolic and microbial quotients were allocated to pur beech stands. In addition, the highest ammonium and nitrate levels were also observed in beech- maple and beech-hornbeam stands. According to the present study, beech-hornbeam- maple stand improved the litter quality, nutrient storageand microbial indicators of the soil, followed by beech-hornbeam, beech- maple and pure beech stands. The practical results of this research indicate the positive effects of tree species diversity on improvement of soil qualitaty and health.

One of the most important factors for determining the volume of trees is selection of an appropriate form factor. This study determined the most appropriate form factor formula and modeling the actual form factor in the Caspian region of northern Iran, Guilan’s forests. Totally, 150 beech (Fagus orientalis) trees were measured. Three coefficients of natural, artificial, and Hohenadel were compared with the actual form factor using pair-wise comparison test. Several nonlinear equations including logistics, Chapman-Richard, and exponential functions were used for modeling the form factor of beech trees. These functions were evaluated in terms of coefficient of determination (R2), paired t test, and accuracy statistics of ME, Root Mean Square Error (RMSE), MEr and RMSEr. The result showed that there were significant differences between the actual form factor and   the each mentioned coefficients. None of the models presented high R2 values. Accuracy statistics showed that exponential and logistic models can be usefully applied for estimation of the actual form factor coefficient. Also the results of t-test showed that there was no significant difference between of actual and estimated means of form factor derived from the logistic model. Therefore, logistic model was selected as the best for the estimating form factor of beech trees in Guilan’s forests of the Caspian region.

The present study aimed to assess the effect of canopy combination of beech trees and associated species (beech-hornbeam- maple, beech-hornbeam, beech- maple and pure beech) on basis of litter and soil characteristics in Mazandaran Province, northern Iran. Litter and soil sampling was made at each beech stand composition, using litter bags and plastic bags (30 × 30 × 30 cm), respectively by five replicates beneath Canopy of central beech trees. Also, in order to effect different seasons on the presence and activity of fanua, were done sampling in addition to summer season in spring, autumn and winter. Characteristics of litter quality (carbon, nitrogen, carbon to nitrogen ratio), Physicochemicaland biological properties of soil (water content, pH, organic carbon, total nitrogen, carbon to nitrogen ratio, earthworm density and biomass, nematodes and microbial respiration) was investigated. The results showed that nitrogen content of soil ( 0.48%), pH (7.43), biomass (56.88 mg m-2) and density (57.05 nm-2) of earthworm, total nematodes (55.02 in 100 gr soil) in beech-hornbeam-maple stand was higher than other studied stands. In all the studied combinations, dansity (45012) and biomass (46.08) of earthworms and nematodes (56.78) had the maximum activities in autumn while the highest of soil microbial respiration (58.5) was recorded in summer season. The based on findings, the stand of beech-hornbeam-maple has significantly impact on the soil organic and mineral characteristics. of the applied results of this research can be to prioritize in the selection of broad-leaved species for revive of degraded areas of the country North.

Herbal Medicines are valuable natural resources that nowadays absorbed the attention of developed countries. Also this plants are using as raw materials to produce Low-risk and potent drugs for humans. One of these valuable species is the Cionura erecta shrub, distributed in a limited area of our country. The aim of this study is investigating the chemical composition of the essential oil of this species. For this purpose, samples from leaf, stem and fruit were collected from Chahar-tagh region of Chaharmahal and Bakhtiari province and essence were extracted by Clevenger machine. In order to identify the essential oil composition, the gas chromatograph (GC) and gas chromatograph attached to mass spectrometer (GC-MS) were used to compare the inhibitory and mass spectrometry indices. The results showed that the essential oil of this species has valuable compounds such as Eugenol, Caryophyllene oxide, Cedron-9-one and Alpha cadinol, which are widely used in industry and pharmacy and pest control. In this study, 23 main chemical compounds were identified totally, that Cedron-9-one and Eugenol Had the highest percentage among identified compounds. Also, the results of this study showed that the essential oil of this species is a rich from the mineral elements including: phosphorus, magnesium, iron, copper, sodium and zinc.

Fire is one of the main causes of carbon emission from forest stands. Therefore, the present study was conducted to investigate the amount of carbon emission caused by fire in the loblolly pine plantations in the Takhsam region that located in area of Lakan city of Guilan province. For this purpose, a burned region with 5 hectares’ area and a control region next to burned stand were selected and 5 circle sample plots with 4r­ (400 square meters) areas were accomplished in two stands by random-systematic method and trees diameter at breast height and total height in sample plots were taken. Then, by investigating the conducted studies Finally, 5 models selected to calculate the trees biomass in two stands. According to the results of this study, the average of trees biomass in the control stand was estimated between 93086.98 (P model) to 10536.9 kg/ha (model M) and the average of trees biomass in the burnt stand was estimated from 67829.73 (P model) to 83509.04 kg /ha (model M). The results of this study also showed that the carbon stock content in the control and fired stands was 48.853 and 38.357 tons per hectare respectively which showed significant difference in t-test. The amount of carbon emissions from the fire was 10495.69 tons per hectare and the total carbon emission at the surface of the fire spot was about 52.478 tons. Among the selected models, P model (BD = β0 β1(DBH­β2)) provided the least standard deviation in the calculations.

This research was conducted to study the spatial patterns, inter and intra-specific associations of tree species that may provide valuable insights into processes and mechanisms that maintain species coexistence. Data collection was done using three one-hectare (100 m × 100 m) plots from three development stages (initial, optimal and decay) in an intact mixed beech forest. The positions of all trees with diameter at breast height (DBH) larger than 7.5 cm were recorded using azimuth-distance method. The measured trees were then divided into four diameter size classes. Spatial patterns and spatial associations among tree size classes (intra-specific) and among species (interspecific) were analyzed using univariate and bivariate Ripley’s K-function. Results indicated that spatial patterns of trees are aggregated, slightly aggregated and random for initial, optimal and decay stages, respectively. Over time, shade-tolerant nature and intra-specific competition of beech trees from different size classes as well as inter-specific competition between beech- hornbeam and among beech- other species across different development stages indicated the different situations. Structural differences, various ecological nature, various reaction of different species to environmental variables at different life stages, difference in growth and physiological mortality due to mixed studied stands can be considered as effective factors in these difference. Knowledge about spatial pattern and natural events are the prerequisite for the implementation of targeted silvicultural interventions and commensurate with the potential and development stages of forest stands.

Deh- Kohneh forest is an enclosed area by 466 hectares, in the north of Fars province. This area has been protected as a wild pear species genetic storage since 1973 by the Fars Province Department of Natural Resources and Watershed Management. In order to study effects of protection in forest zone, a fifty hectare area from enclosed forest and a 50 hectare area from unclosed forest, which are same in topography and forest type, were compared. The results showed that the numbers of tree and shrub species in enclosed area were significantly more than unclosed area. Compare the abundance of trees and shrubs represents a decline of P.glabra and P.syriaca and upgrades F.rotundifolia and D.mucronata identified in the unprotected area. The canopy cover in both areas was almost the same. The average of height for trees and shrubs in the protected area were smaller than unprotected area, because of regenerations. The current results showed that protection of Deh-kohneh forest for nearly half a century has been improved the quality and quantity of the forest structure. Therefore, it is suggested that with protection of such area, conservation of genetic resources in forests and creation a research area for other researchers can be provided in future.

Canopy gaps have an important role in establishing of natural regeneration and determining the vegetation composition in forest ecosystems. The regeneration of oak trees can lead to better management of forest stands. This study was performed in the Oak forest of northern Khorasan to investigate the characteristics of established seedlings in forest gaps. To study the natural regeneration in the forests, 30 gaps in the protected area and 30 gaps in the unprotected area were selected (in three classes). At first, the gaps area was recorded and the selected parameters such as slope, direction, height, herb layer were measured. The specifications of quantitative parameters (light intensity, regeneration, diameter at breast height (1.30 m) and collar diameter of oak seedling (Quercus castaneifolia) and qualitative (mode of branching, crown shape) in various gaps were studied. There was a significant difference between these two regions in terms of the parameters mentioned except collar diameter and diameter at breast height of the seedlings. The regenerations in both areas in the gaps of 500-800 m2 have had a better situation than other gaps. In addition, the best condition was qualitatively observed in the gaps of500-800 m2. Finally, it can be concluded that the regeneration in the protected area both quantitative and qualitative was in a more suitable situation than the unprotected area, because the unprotected area was closer to the village and under more destruction and utilization than the dense area.

The development of forest ecosystems compromises three stages including initial, optimal and decay.In all these stages, the changes in canopy volume and amount of light reaching lead to changes in soil physiochemical and biological properties. Enzymes activities as biochemical properties are of the most important indicators to determine the soil quality. This research aims at assessing the soil condition is in different development stages. For this purpose, phosphatase enzymes activities and some physical properties of soil in different development stages of Fagus orientalis Lipsky forests in Rezvanshahr area were determined. Soil samples were randomly taken from 0-10 and 10-20 cm depths. Activity of phosphatase enzymes was measured by spectrophotometry method. Some physical properties of soil such as bulk density, porosity were determined by standards methods. The results indicated acid and alkaline phosphatase enzymes activities were significantly different in terms of silt percent (p≤0.01), bulk density amount, and first depth (p≤0.05) in three development stages. The values of all measured properties were higher in decay stage except for bulk density amount in 0-10 cm depth than two other stages. In addition, the activity of acid phosphatase (depth 0-10) and alkaline phosphatase (depth 10-20) was positively correlated with available phosphorus in decay stage. It is concluded that the decay stage provides better conditions to the soil micro-organisms and phosphatase activity.

The establishment and survival of seedlings is one of the main objectives of forest management which ensures continues production. The aim of this article is the investigation of dead trees effect on beech and hornbeam seedlings in Masal's forests. For this reason, 30 dead trees were selected, and the control trees were selected in four aspects around the dead trees. They were the same as dead trees in terms of species and diameter. In general, 30 and 120 sampling plots were taken around dead trees and control trees, in respectively. The quantity and quality (crown equality, multi trucks and verticality) of seedlings were recorded. In addition, the volume of dead trees were assessed by measuring their diameter and height, and also their decay classes were investigated. According to the results, abundance of seedlings doesnt significantly differ among decay and canopy coverage classes, whereas dead tree's diameter classes significantly effect on seedlings abundance. The forked seedlings were significantly higher than other forms of stem growth. Abundance of seedlings, in terms of quantity and quality (the forked) around the dead trees, showed significant differences with control trees. Based on the finding of this research and the overall impact of dead trees on regeneration, it is recommended that large dead trees be considered as a seedbed in the management of natural regeneration in the forest stands.

Water repellency is a soil property with short-term (or seasonal) variations and reduces or even prevents water infiltration into the soil. When soils are dry, water repellency is found to be at its most extreme. The objective of this study was to investigate variations of soil water repellencyand determine critical soil water contents in 10 forestry sites covered by different plant species (Pinus taeda, Alnus subcordata, Pterocarya fraxinifolia, Sambucus ebulus, Boxus sempervirens, Parotia persica, Quercus castanefolia, Fagus orientalis, Acer sp. and sparse grass) in Guilan province. The soils were sampled two times at autumn and summer from 0-5 cm depth. The water drop penetration time (WDPT) test was used to measure the actual water repellency at the selected sites under the natural field-moist conditions. The potential water repellency was measured in undisturbed samples dried at 25 °C taken from the same sites. Actual water repellency was determined only at forest sites in summer. A wide range of soil water repellency classes (hydrophilic to extremely water-repellent soils) were detected at the examined sites. The results show that water repellency is the largest at the sites with sandy texture. In this research, positive correlations between logWDPT and organic matter content(r=0.42) and sand percentage (r=0.27) were obtained. Correlations between Log WDPT and clay percentage was negative (r= -0.35) and no correlation was found between pH and Log WDPT. The soil water content zone at which soils became water repellent (critical water content) was different for each site and it was a function of the soil properties. Critical water content was assessed in sandy soils (0-5 -cm depth) and ranged from 4.0-6.7 %, in silty­ clay­ loam and silty­loam, between 10.1-15.8%, and in silty ­loam and clay loam with high organic matter varied from 13.3-21.3%. Apparently, soil organic matter and texture influence the critical water content.

Associations between plant coverage and environmental parameters help to understand the natural habitats, as well as the effective functions on growth and establishment of plant species. The Marsdenia erecta (L.) R. Br. ex DC.is one of shrub species which occurs in forests of Chaharmahal and Bakhtiari province, about which almost no report on ecological characteristics and regional distribution has been published so far. In this study, growth regions of Marsdenia erecta were initially identified following site visits and preliminary checks, based on which two habitats of Chahartagh and Dorak Anari were selected. Field sampling was accomplished by means of 35 circular plots of 1000 m2 each. In each plot, quantitative characteristics of species, including number of standing trees, average crown diameter and height were measured. In addition, a mixture soil samples were collected from the surface soil horizon, which were then analyzed in terms of chemical and physical properties such as electrical conductivity, organic carbon, lime, phosphorus, potassium, nitrogen, sand, silt and clay contents. The properties were statistically analyses on species level. Furthermore, the relationship between Marsdenia erecta distribution and soil characteristics was surveyed by principal component analysis. The results showed maximum diameter, height and canopy of Marsdenia erecta across Dorak Anari test site, whereas Chahartagh test site revealed the highest density. Quantitative results also revealed a significant difference between the measured heights of Marsdenia erecta individuals across the two test sites. However, no significant difference was observed by comparing the mean values of soil variables (acidity, organic carbon, lime, phosphorus, potassium, nitrogen, sand, silt and clay). Based upon the applied principal component analysis, soil texture was the most influential factor on distribution of Marsdenia erecta in Dorak Anari, whereas chemical variables of soil such as organic carbon, phosphorus, potassium and nitrogen were the major determinants in Chahartaghtest site.