نشریه بوم شناسی جنگل های ایران
پیاپی 18 (پاییز و زمستان 1400)

One way to study the problems of forests, to study its changes over the years and access to accurate information, is to use remote sensing technology and satellite data. The use of GIS as one of the most important tools for analyzing the extent, location of degradation and auxiliary factor to identify the cause and factors in the solution of the phenomenon of deforestation. Research shows that between 1990 and 2000, an average of 6.8 hectares of forest area in Ilam province decreased. On the other hand, the phenomenon of oak tree droughts and deforestation has intensified due to severe droughts and land use changes, especially constructions that have been done in forest areas. Therefore, this study was conducted to investigate the distribution of oak tree drought with physiographic factors and also land use change in Zagros forest areas in Ilam province.

In conducting this research, first the digital elevation model of the province was prepared based on topographic maps, then based on this model, information layers of slope class, geographical directions and elevation classes were extracted. In order to prepare the oak tree drought site location layer, in addition to processing satellite images, the location of oak tree drought trees was collected at 100 points in the province. To ensure the accuracy of the obtained maps, the accuracy assessment method was used, which is based on comparing the map extracted from satellite data with ground reality information such as field perceptions and visits, existing maps and the expert knowledge of the interpreter. In the following, the location map of the distribution of dry masses was overlapped and integrated with slope classes, geographical directions, altitude classes and land use. Then the frequency of dead trees in the units of the mentioned layers was calculated and presented as a percentage.

According to the physiographic units of the region, the highest amount of dry masses is related to the altitude of 1200 to 1600 meters, slope class of 0 to 15% and the geographical direction of the southwest. The lowest of them are in the altitude floor less than 400 and more than 2400 meters, the slope class is more than 30% and the geographical directions are northeast and southeast. The highest frequency of oak tree drying in Ilam province is in the classification of forest areas related to thin class 42%, medium 39% and dense forest areas 5%, respectively.

In general, it can be stated that physiographic factors (slope, geographical directions and altitude) as well as land use changes in different forms and different intensities and weaknesses can contribute to the destruction of temples. Zagros and especially in the area of ​​Ilam province to be effective. Based on the obtained results, dried oak trees have different distribution in physiographic units. In the study of this distribution, the use of satellite images, especially in the study of forest areas, both in terms of the phenomenon of oak tree drying and in terms of deforestation due to land use changes or other natural factors, has many applications.

Precision surveying of plantations is important for forest management. But on the other hand, terrestrial area calculation of plantations has problems such as topography, presence of herbaceous, woody intrusive species, relatively low accuracy of conventional GPS in forestry plans, the cost and time of use of DGPS. UAVs have plenty of advantages, such as time and space flexibility in surveying with precise accuracy in centimeter level.

In this research, a drone was used without ground control points, (RTK) system or (PPK) for surveying, and its accuracy was compared to conventional GPS in forestry. The UAV that used was a quadcopter with a spatial resolution of 2/5 centimeters. In order to compare the precision, 7 sites 0/5, 1, 1/5, 2, 2/5, 3 and 4 hectares were used. GPS tracking was done using point and track method. UAV, s flight conducted at heights of 50 and 75 m, and a surveying with theodolite was used as a precision alignment index.

The results of this study showed that surveying using conventional GPS in forestry is based on point method is more accurate than track method, and UAV surveying with no ground control points or (RTK) system or (PPK) is not more accurate than the conventional GPS used in forestry and with increasing flight altitude, its error increases with a nearly constant trend, but by applying the correction coefficient obtained from the ground index, the precision of the UAV surveying is more accurate than the GPS, and the error will be less than one percent decrease.

Considering that in Iran, this technique has not yet entered the studies of preparation and implementation of forestry plans and monitoring of afforestation and their surveying, the results of this study can be effective in the implementation of forestry plans.

One of the most important causes of the destruction and decline of natural ecosystems is the lack of a market to determine the value of services produced by these ecosystems, and as a result, consider these services free. One of the most valuable services provided by ecosystems is the production of fresh water which in the present study, a model has been presented for achieving the spatial distribution of service value of water production ecosystem in Darabkola watershed that is located in Mazandaran Province.

In this study, was used the water yield model in InVEST to quantify the water production service. In the model, the water production was calculated the based on the Budyko curve, which in fact determines the amount of water running off each pixel of land as the total precipitation minus evapotranspiration. The required data include maps of land use and land cover, average annual precipitation and potential evapotranspiration, soil depth, plant available water content, boundary of watersheds and sub-watersheds as well as a biophysical table. In order to evaluate this ecosystem service has been valued with the replacement cost and thus it has been possible to obtain a spatial distribution map of the value of water production ecosystem service in the study area.

According to the calculations done by the model in whole Darabkola watershed, annually 43094152  of water is produced. The results of different land uses indicated that the highest amount of runoff in land uses is in man-made land use equal to 3743.76  and followed by agriculture and garden land uses with values of 3601.34  and 3592.18  had the highest water production, respectively. Also, the lowest runoff was related to the uses of semi-dense forest and dense forest with values of 2960.82  and 2602.19 , which indicates that the presence of the canopy of forest trees and their spatial distribution has an important effect on increasing water penetration in the soil and reducing runoff production. The study area is classified into four different classes of value in terms of economic value of water ecosystem services. These classes differ from a minimum of 24 - 29 million Rials to a maximum of 39 - 43 million Rials per hectare.

The results of this study showed that Although InVEST model needs available and relatively simple data but it has high efficiency and we can use it for mapping ecosystem services and decision making. Also, using the quantitative results obtained from the implementation of the InVEST model, it was possible to show the spatial distribution of the value of ecosystem services in the study area. The results of this section showed that attention to the spatial dimensions is very important in determining the value of water production service, because the change in spatial characteristics will greatly affect the value of water production service.

Forest hazelnut (Corylus avellana L.) is a hardy rooting plant and therefore its propagation by conventional asexual methods is almost impossible. The aim of this study was to determine the effect of auxin and inoculation of mycorrhizal fungi on callus, rooting and vegetative traits of hazelnut cuttings.

semi hardwood cuttings were collected on July from Arasbaran forests (Makidi site). Cuttings were firstly treated with concentrations of 0, 500, 1000, 2000 and 3000 mg L−1 IBA and then were inoculated individually with Glomus intraradices and Trichoderma harzianum fungi. Cuttings were cultured in perlite - sand medium and then they were kept in a mist system equipped greenhouse. After 70 days from planting, the percentage of callusing, rooting, root number, root dry weight, total plant dry weight, length cuttings, leaf area and Colonization were recorded.

The highest callusing (34.3 %), rooting (27.2 %), root number (2.6 n), root dry weight (0.35 g), total plant dry weight (3.39 g), length cutting (12.32 cm), leaf area (29.13 cm2) and Colonization (28.77%) was observed in cuttings that treated with IBA 2000 mg. L−1 and then inoculated with G. intraradices. Overall, it was confirmed that the hazelnut is difficult rooted via cuttings and application of IBA growth regulator is necessary for rooting of semi-hardwood cuttings plants.  

The best form its vegetative propagation is collecting cuttings from 1-year old cutting off shoots in June and treating by IBA growth regulator (2000 mg L-1) in combination with Glomus intraradices.

Gleditschia  caspica Desf is one of the one of the tree species of the Hyrcanian forests. Extreme grazing, overexploitation of livestock, and the lack of natural regeneration system in diverse ecosystems have put Gleditsia caspica in danger of extinction. In this study, the conditions of the callus induction and regeneration were investigated under different growth regulators treatments. For this purpose, Stem, hypocotyl and root specimens were cut from sterile intact seedlings and considered as a separate explant. The MS medium supplemented with IBA, NAA and 2,4-D at different concentrated levels (0.5, 1.5, 3 and 4 mg / l) and TDZ, 2ip, BAP and Kin at different concentrations (0.1, 0.5 and 1 mg/l) were used for callus induction. Growth regulators of TDZ and 2,4-D on 0.5, 1 and 2 mg/l concentration in MS medium were used to regeneration. Regarding rooting, callus-derived plantlets exposed to 5 µM IBA in MS media. The characteristics of callus percentage, fresh and dry weight, callus area, color, type and growth curve of calluses were compared. Also, the proliferation percentage and mean number of shoots in each explant were examined. The results showed that the effect of explants and hormone type on the callus induction percentage showed a significant difference at the level of 99%. The percentage of callus induction in the stem explants were much higher than that of the hypocotyl and roots. The effect of different hormones on all stem explant characteristics was significantly different at 99%. The results showed that the 2,4-D yielded the highest and IBA resulted to the lowest percentage of callus induction among the studied auxins. Among the cytokines, Kin had the lowest and TDZ leads to the highest percentage of callus induction. The growth curve of fresh and dry weight in regenerated calli indicated the privilege of 2,4-D compared to other hormones(P<0.05). In general, according to the obtained results, it is recommended to use MS + 0.5 mg/l 2.4-D + 0.5 mg/l TDZ formula for indirect regeneration of Gleditschia  caspica.

Estimating the amount of wood produced in poplar plantations is not possible without determining the area of poplar plants. Estimating the amount of wood produced is very important for the production management of wood industry units. Industry owners need to know how much poplar wood can be extracted in the coming years. Therefore, identifying areas of poplar cultivation in Mazandaran province is one of the main objectives of the present study.

This study was conducted to estimate adult poplar cultivations area using Sentinel2 satellite in Mazandaran Province. Firstly, the general survey carried out on poplar cultivation with full canopy distribution and its cultivation area at the regarding area. Then, in the whole area, the numbers of 202 cultivated areas have randomly been mapped using Global Positioning System (GPS) as Training Samples. In the next step, the relevant images have been identified in term of time and downloaded, and also radiometric, atmospheric, and geometric corrections have been done on them. Also, banding appearance, color compositions, images mosaicking and bands calculations have been performed. The Support Vector Machine (SVM) algorithm has been used in order to extract poplar cultivation in the growth period of 2018 (March to December). Evaluation of the accuracy of the classification results of the generated maps was performed using 183 ground trust points via GPS.

The results showed that in 2018, 705 hectares of Mazandaran area are under poplar plantations, which Mahmoudabad and Neka cities with an area of 167 hectares and 33 hectares, respectively, had the highest and lowest area of poplar cultivation. Poplar cultivation area estimated in this study was excluding young poplar stands. Furthermore, the results of the accuracy assessment demonstrated that the overall accuracy is 95.35. The average area of poplar stands was 800 square meters. But the number of stands less than 500 square meters (7121 plots) includes more than 80% of the stands. Only 0.2% of the total stands (57 stands) make up more than one hectare. These 57 stands occupied about half of the province's poplar plantations.

Despite the favorable climatic conditions in Mazandaran province, the area of poplar cultivations was lower than expected. Therefore, it is suggested that in the future, the necessary measures should be taken to meet the wooden needs of Mazandaran province through wood farming.

Rapid, low-cost and accurate estimation of tree metrics in the forest ecosystem is one of the challenges facing forest managers and inventories. Therefore, given that the forest areas of northern of Iran, mainly deciduous and uneven-aged forests, are covered with various tree ‎species of different sizes, mensuration techniques could be developed and established to suit the particular ‎circumstances. Methods used in forest inventory should be user-friendly, repeatable, relatively low cost, and also have high accuracy and precession for forest inventory operation.

Thanks to technological advances in the photography industry, one of the attractive and proposed methods could be the use of digital cameras, in which the potential and performance of this method was evaluated to estimate diameter at different heights of trees. For this purpose, using a digital camera which is mounted on a pre-designed horizontal index and in different shooting distance, diameter at stump height, DBH, and diameter at top of trunk for 108 trees, in REFTMU and in the altitude range of 750 to 1100 meters above sea level and in autumn was estimated. The distance from each shooting station to each tree was captured using the audio and laser rangefinder of the Vertex device as well as the laser meter.

The overall results showed that at 95% significance level, there was a significant difference with real data only in estimating the diameter at stump height. It is also showing an underestimation in estimating the diameter at breast height and at the top of trunk, and in estimating the upper trunk diameter, it was overestimated. The lowest amount of %CV.RMSE was also observed in estimating breast diameter (4.99%).

The evaluated method showed that in the middle classes of metrics captured data, it was more accurate and less error than the upper and lower classes. The results also showed that with increasing the distance of the shooting point, the error rate was increased. Consequently, the results of time study showed that the average operational time for capturing data in digital camera and the traditional method were 3.88 min.tree-1, and 3.42 min.tree-1, respectively.

Canopy gaps in different sizes have been created by the implementation of different silvicultural practices such as single-tree selection in beech forest stands in Hyrcanian forests. Investigating the effects of forest gaps on the characteristics of trees and soil in the forest ecosystem can be very helpful in planning silvicultural operations. Shade-tolerant beech trees in this ecosystem are of ecological and economic importance and knowing the reaction of such a valuable tree can be effective for forest management and selection of forestry methods.Therefore, the purpose of the present study was to determine the correlation between structure, fine roots properties of beech trees and soil biology(MBC,MBN and MBP) in different gaps (n = 15) created by single-tree selection system with competition index in beech forest stands in Mazandaran-Sari province.

In the beech forest stand, 15 forest gaps were identified including three classes of small (80-130), medium (175-131) and large (176-300m2) size and five replicates were selected for each level. In four cardinal positions of each gap, beech trees were selected and their height, diameter at breast height, crown diameter, area, volume and fine roots as well as competition index were measured.

Pearson correlation coefficients showed a significant positive correlation between competition index with height, DBH, crown diameter, crown area and length of Bole and also negative correlation with height to diameter ratio (H/D) of beech trees. There was a significant negative correlation between competition index and microbial biomass nitrogen and a significant positive correlation with microbial biomass carbon to microbial biomass nitrogen ratio (MBC/MBN). With increasing density, specific root length and specific area of fine roots, the values of competition index increased. There was a significant correlation between some structural characteristics of beech trees with fine root characteristics at the edge of gaps. Correlation coefficients between fine root characteristics of beech trees show significant correlation between some variables.

In general, the results of the study showed that forest management through the application of single-tree selection system and the formation of canopy gaps in beech stand has influenced the structural characteristics and fine roots of beech trees six years after the creation of gaps.

Traditional knowledge is knowledge that is obtained due to the experience and traditions of the local people of a region and using the method of trial and error in a laboratory called nature. The identification of traditional forest-related knowledge has become very important in recent decades, especially in the field of achieving sustainable forest management and with the ultimate goal of achieving sustainable local, regional, national and global development. The purpose of this study is to identify the traditional knowledge related to harvest of acorns of Quercus brantii Lindl.

This research was carried out in two local regions of Chigo and Bidleh located in Monj section of Lordegan city in Chaharmahal and Bakhtiari province. The required information was obtained from the local community by reputation approach and using 56 interviews. The role of acorns in formal studies was also examined separately using library studies to evaluate the traditional knowledge of acorn harvesting of these trees. Finally, using qualitative evaluation and analysis of effects and consequences, ten criteria for measuring traditional and formal knowledge and the difference between the two knowledge were explained.

Among other uses of acorns which is almost common in most rural households in the study area the use of oak seeds (acorns) to prepare various muskets is common. The various uses of oak that are commonly used by local people living in the Zagros, such as: oak sap, oak kebab and boiled oak. Also, a brown colored juice called Qazūlah honey is formed on the fruit cup in late summer and early autumn, which is called "Man Shocked".

The results showed that since a formal knowledge can be based on scientific needs, the speed of information production, the rule of scientific regulation, scientific accuracy and media communication in line with research related to the seeds of Quercus brantii trees can be the benefits of formal knowledge. In this process (similar to other formal knowledge), but on the other hand, traditional knowledge due to adaptation to local conditions and social acceptance can provide the basis for participatory management in the Zagros forests.

Today, the use of modeling methods to predict and modeling of regeneration for different species in forest conservation and management plans is increasing. It is possible to predict the condition and density of forests in the future by forest regeneration modeling and based on that, adopted different management scenarios.

With regard to importance of the subject, in this study the regeneration rate of oak species in a part of oak forests of Manesht and Qalarang protected area-Illam province was estimated using artificial neural network (ANN) and environmental variables such as primary topographic properties, secondary topography, soil physical properties, soil chemical properties and forest structural characteristics as independent variables. For this purpose, various functions and models were evaluated. After sampling, 70% of the, oak regeneration samples was used as training samples to implement the ANN model and the remaining 30% of the data was used to evaluate the model results. Finally, the sensitivity of the oak regeneration model was analyzed.

The results showed that the artificial neural network with error standard error equal to 0.99 was able to estimate the oak regeneration in the study area. The results of sensitivity analysis showed that the highest R2 is related to the model with all input variables, which indicates the positive effect of all input parameters to the model, so that by removing each of the input variables, the accuracy of the model in predicting oak regeneration decreases. However, the results also showed that forest structural and soil chemical characteristics are the most important factors affecting oak regeneration in the study area. The least effect on oak regeneration in the prepared model are secondary topographic variables, which although had a positive role in predicting the regeneration. However, the effect of these variables was less than other variables. The results showed that about 21% of the study area has less than 100 regenerations per hectare. Also, more than 12% of the study area has more than 1200 regenerations per hectare.

In general, the simultaneous use of all primary and secondary topographic features, soil and forest structural characteristics increase the accuracy of regeneration modeling of Zagros oak forests. On the other hand, ANN due to its flexibility, allows the selection of the various variables according to the study area conditions and the available information, as a result, it increases the accuracy of modeling.

Quercus castaneifolia C.A. May is one of the most valuable species of Hyrcanian forest ecosystems in terms of an environmental and economic aspects. The aim of this study was to assess the effects of multicultural mixing patterns on the quantitative characteristics and soil properties in Q. castaneifolia stands in the natural habitat, which can provide useful information in the sustainable management close to the nature of future afforestation with this species.

Three stands of Q. castaneifolia; i) pure stand (at least 90% Q. castaneifolia), ii) Querco-Parroteum with Acer (ca. 50% Q. castaneifolia) and iii) Acero-Parroteum with Quercus (less than 20% Q. castaneifolia) with four replications were selected to investigate some silvicultural and soil characteristics in the Sorkhdary forest management plan in Golestan province. For this study, in each of the studied stands, a 150×200-meter sampling network was implemented using a random-systematic method and 15 circular sampling samples of 1000 square meters were collected (a total of 45 circular sampling plots in all stands).

The results showed that the average trees number, in three pure Quercus stand, 50% and 20% Q. castaneifolia mixed stands were 274, 289 and 252 ha-1 and the calculated mean stands volume were 442.27, 394.87 and 371.65 m3ha-1, respectively. In pure Quercus stands had trees mostly the diameter breath height (DBH) >35 cm and in 20% Q. castaneifolia mixed stand had most trees DBH< 35 cm. The highest total tree height was measured in the DBH >55 cm in Q. castaneifolia pure stands. The highest soil pH was measured in Quercus pure stands (6.6) and the lowest values were measured in 20% Q. castaneifolia mixed stands (5.99). Moreover, the highest soil organic matter and nitrogen contents were measured in Q castaneifolia pure stands (6.90% and 0.85%) and the lowest values were measured in 20% mixed Q. castaneifolia stands (4.15% and 0.40%). In terms of phosphorus and potassium contents, both pure and mixed 50% Q. castaneifolia stands showed higher values in compare to mixed 20% Q castaneifolia stands.

Consequently, the higher intensity of Q. castaneifolia in stands enhanced quantitative stand growth and improved chemical properties of soil such as organic matter, nitrogen, potassium and phosphorus content.

Collembola are most abundant decomposer soil living arthropoda in forest ecosystems. They are among the best indicators within the soil mesofauna to determine the health and sustainability of forest ecosystems. The Hyrcanian forests, most of which are located in Iran, are among the most valuable forests on Earth, which, despite their climatic diversity, unique plant and animal species, are inscribed on the UNESCO World Heritage List. Despite the very important role of Collembola in ecological processes of forests, including the decomposition of organic matter and nutrient cycles but the role of these small arthropods in the Iranian Hyrcanian forests has not been much studied. The study was conducted to investigate and identify the fauna of Collembola in the forest soils to introduce their importance for forest ecologists in Iran.

The research was carried out at a station in the Samsakandeh mixed forest of Sari as part of the temperate deciduous forests of the Hyrcanian region. For studying collembolan fauna in soil and leaf litter of the forest, in 2016-2017, soil and leaf litter samples were collected from different locations by soil core (depth 10 cm) and pitfall traps. The springtails were extracted by Berlese funnel and were identified after preparing microscopic slides with available keys.

In sum, 25 species belonging to 21 genera from 9 families were collected and identified as species level. The specimens of Lepidocyrtus, Sminthurinus, Neanura, Sphyrotheca and Dicyrtoma identified as genus level.

Six species including Entomobrya obscurella (Brown, 1926), Heteromurus gigans (Mari Mutt & Stomp, 1980), Heteromurus variabilis (Martynova, 1974), Orchesella spectabilis (Stach, 1960), Pseudachorutes corticicolus (Schaffer, 1897) and Protaphorura ombrophila (Stach, 1960) were reported for the first time for Iran fauna. Two species, Neelus murinus (Folsom, 1986) and Pseudachorutes subcrassus Tullberg, 1871, are re-reported to the Samsakandeh mixed forest, 38 years after the first Cox report (1982).

The aim of this study was to investigate the woody and herbal frequency and species diversity in the mountain forests of northern Iran, Poudeh village of Roodsar, over time and as a result of traditional exclosure of these forests.

The study area is located in the forests of Poudeh village, Roodsar, Guilan province. According to the traditions of the region, people protected the spots of the destroyed forest areas near their hazelnut gardens for flood prevention and personal exploitation. They do this by using stones and placing shrubs on it, or using wooden stems and barbed wires. In this area, there are many of exclosure forest spots that have been protected and enclosed by the native people. Three exclosure forest spots were selected for this study. For this purpose, plots with different conservation history including low-term enclosed forest area (Less than 40 years), middle-term enclosed forest area (More than 40 years) and reference forest area were selected and the indicators of relative frequency, relative ecological importance value and species diversity were calculated.

The results showed that with increasing the duration of forest protection, the relative abundance of beech in both strata levels increased the relative abundance of hornbeam and the amount of species diversity also decreased. The highest and lowest differences in relative abundance of beech between the two strata were observed in reference forest area and low-term enclosed forest area respectively. The ratio between the abundance of beech in the upper story to the understory for low-term enclosed forest area and middle-term enclosed forest area was 1.18 and 1.24, respectively. In the control area where the highest relative abundance of beech species (80%) was recorded in the upper floor (tree), there is a moderate relationship between the two floors (r = 0.61, p <0.001) and in short-term protection, this relationship is significant (r = 0.72, p <0.001). In the middle-term enclosed forest area (more than 40 years) with increasing the relative abundance of beech in the upper story, its relative abundance in the understory also increased significantly (r = 0.88, p<0.001).

The process of species change is a complex and time-consuming process. The results show in the evolution of the stand structure in the affected areas, medium-term protection can facilitate the formation of understory. It is recommended that middle-term enclosed forest area along with silvicultural treatment be applied to formation of understory.

Recognition of the available moisture content and its changes in the habitat can be a dynamic ecological indicator. The aim of this study was evaluating the soil moisture storage volume with the distribution model of the Turc in the oak forest located in the Meleh-Siah Ilam.

The research was conducted from October 2013 to September 2015. Monthly rainfall and temperature data, monthly solar radiation, water holding capacity map and DEM of the region were used as input data.  To validate the soil moisture data from the water balance model, 33 humidity sensors 110 cm were installed in different locations of the habitat. Then, soil moisture was measured with TDR moisture meter in monthly time step. To evaluate the model, the mean absolute error (MAE) and mean error deviation (MBE) statistics were used and the results were analyzed.

The results showed that the accuracy of the model in estimating soil moisture in wet months is low and is overestimated, and Suitable in a dry month. Other results showed that in the first and second year of the study, precipitation was 680 mm and 383 mm, respectively and the share of evapotranspiration from precipitation is 56% and 77%, respectively. Also, in the study site the available water capacity of the soil is 125 mm, which the maximum in March and the downtrend continued until September and reached a minimum of zero. Other results indicate that the vegetation in the study area was drought tolerant in the first year (normal in terms of rainfall), in two months of August and September and increased in the second year (drought), in the months of July, August, September and October. The results also showed that 73% of the dried oak stands correspond to the areas that Soil moisture reached below the wilting point (15%) in September.

Therefore, reducing soil moisture in droughts has played an important role in the drying of oak bases and effect of the intensity and persistence of drought periods on the drying of oak trees needs further investigation.

Today, Metropolises require more green space because of air pollution, but water scarcity in aried areas  should lead to irrigation of unconventional sources such as wastewater, which due to the contamination of these sources, tree species with high phytoremediation capability should be used.

In this study, two-year-old seedlings of four species of Judas Tree (Cercis siliquastrum L.), Arborvitaes (Thuja orientalis L.), Persian Lilac (Melia azedarach L.) and White Mulberry (Morus alba L.) were planted in pots and were irrigated with Tehran West Water Treatment Plant effluent which contained manganese and chromium from March to October 2017.

The amount of chromium and manganese in the organs of species irrigated with effluent showed a significant increase compared to ordinary water. All four species irrigated with water treatment plant effluent showed a same growth compared to ordinary water. The highest amount of manganese was in leaf and chromium in root of all four species. The lower than one BCF and more than one TF for manganese in all four species indicated that they were not suitable for phytostabilization of this metal, but all four species (Cercis siliquastrum L.) (1.87), (Morus alba L.) (2.07), (Thuja orientalis L.) (1.96) and (Melia azedarach L.) (1.83) with a more than one TF are suitable for manganese phytoextraction. However, because BCF in them is lower than one, further investigation is needed. White mulberry and Persian lilac with a lower than one BCF and TF for chromium indicated that none of them were suitable for chromium phytostabilization and phytoextraction; But both Judas tree (1.39) and arborvitaes (1.04) with higher than one BCF and lower than one TF for chromium were appropriate to phytostabilization of this metal.

As a result, Judas tree and arborvitaes, which have both the ability to phytostabilization chromium and the ability to phytoextraction manganese, are the best species for the phytoremediation of these two elements in soil irrigated with effluent. Equal growth parameters of all four species after irrigation with this effluent indicated that reuse of Tehran West Water Treatment effluent can be an approach to compensate water scarcity but further studies and monitoring of conditions in order to select the most suitable species for phytoremediation of heavy metals as well as long-term effects of irrigation with effluent, are required.

Due to the scattering of poplar plantations in the city of Sowme`eh Sara, Gilan province and the lack of timely, documentary and scientific information from the current status, it is necessary to determine the exact location of the distribution, area and volume of its poplar plantations. In the present study, area, distribution and status of poplar plantation and biometric statistics of poplar trees in Sowme`eh Sara city and their wood production were measured separately for each village.

First, through field operations, the field of poplar plantations with the Global Positioning System (GPS) and the use of GPS Fields Area Measure PRO application was located and uploaded to Google Earth and the poplar cultivation pattern was determined. After drawing the poplar plantation polygons on Google Earth, they were transferred to ArcGIS and converted to an integrated polygon layer in shp format. After the completion of the map each village, the field control was performed and the biometric information of each section was recorded, including the measuring diameter at breast height and height of trees and then their volume was calculated, and then the distribution map and the total location of the existing poplar plantations in the city were prepared. Also, climate maps of temperature and precipitation this city were drawn by receiving data from three meteorological stations related to the ten-year period (2008-2017) and some soil characteristics of Sowme`eh Sara city were prepared separately for each village related to 0-30 cm depth with 138 harvest points.

The results showed that the total area of poplar plantations in Sowme`eh Sara city is 6,944 ha and Ziaber village with 29.65% is the first grade in the percentage of land allocation to poplar plantation with maximum area of poplar plantation section and the highest number and volume of trees. There are a number of 99 poplar plantations fields with an area of less than 500 m2 and 1584 poplar plantations fields with an area of more than 1 ha, which include 3.22 ha and 5471 ha of poplar plantations areas in this city, respectively. The wood obtained from about 91% of the total area of poplar plantation in the city is dedicated to concentrated cultivation and industrial uses. The highest average diameter at breast height and height of trees in Tolmat village and the lowest of them in Hendukhaleh village were obtained. The results of soil properties showed that the soil texture of the studied villages was mainly loamy-clay texture that is suitable for poplar cultivation and development, but the pH of the soil showed different values in each village.

Considering the total volume of trees in Sowme`eh Sara city with the amount of 3411884 m3, this amount of wood volume can provide about a quarter of the country's annual wood consumption.

The humus index is a numerical score based on the visual assessment of organic horizons and humus forms identification. This index reflects different characteristics of forests stand and soil. Forest humus is an intermediate between plants and soil, which is affected by various factors, such as topography, climate, vegetation and soil. Nevertheless, by digging the humus profile and determining its index, it is also possible to determine many ecological factors. The aim of this study was to investigate the humus index and its relationship with topographic, soil and forest cover characteristics along an altitudinal gradient in the four-altitude class, including 0, 500, 1000 and 1500 meters above sea level (m a.s.l.), in Vaz forests located in Mazandaran province.

In each altitude class, the characteristics of the trees such as crown canopy, density, diameter and height, as well as topography and soil characteristics such as altitude, slope percentage, soil moisture and temperature were taken in 400 m2 plots, and in each plot, five 30 × 30 cm profiles for identification of humus forms were drilled and then identified and classified based on Humusica classification. In order to evaluate the humus index between different altitude classes was used one-way analysis of variance (ANOVA), as well as to analyze its relationship with the mentioned characteristics, multiple linear regression analysis (MLR) was used.

The results showed that the highest amount of humus index and litter thickness belonged to the altitude class 1500 m a.s.l. and their trend is increasing along the altitudinal gradient. Also, the results of MLR indicate the existence of a linear and significant relationship is between humus index and topographic and soil characteristics with high determination coefficient (R2 = 0.76), especially soil temperature with (P-value = 0.000), while the tree cover characteristics with a low determination coefficient (R2 = 0.31), cannot well be a good predictor for evaluating the humus index. Meanwhile, soil temperature and trees crown canopy are two factors that have shown the highest t-statistics in relation to the humus index, so that the decrease in soil temperature and trees crown canopy has increased the humus index.

In general, it can be concluded that with increasing altitude, the organic part of the forest floor and Humus index increase, and their variability is mostly due to changes in topographic and soil temperature characteristics.

The tree crown component is one of the decisions making tools in units of forest management and commonly used in growth and yield models. One of the indices in related to tree crown in crown ratio which is the ratio of live crown length to the total height of the tree. The purpose of this study was to crown ratio modeling of poplar trees (Populus deltoides) using linear and nonlinear regressions (exponential, logistic and Chapman-Richard) in plantations of Guilan province.

For this purpose, the data related to 660 poplar trees including DBH, collar diameter, total height, crown length, crown width, crown area, crown diameter, basal area, tree slenderness coefficient, stem height and crown ratio were measured and recorded. To evaluate and compare different models were used coefficient of determination (R2), paired-samples t-test and four accuracy statistics including ME, RMSE, MEr and RMSEr.

The coefficient of determination of linear and nonlinear models showed that all models have acceptable coefficient of determination. Also, the results of accuracy statistics showed that the exponential and linear models were more accurate than the other models. But the results of mean comparison test indicated there was no significant difference between of measured mean with estimated mean of crown ratio derived from exponential model. While there was significant difference between of measured mean of crown ratio with estimated mean of linear, logistic and Chapman-Richard models. Regarding to the results of precision and accuracy of studied models, exponential model was selected as the more suitable model for estimation of crown ratio of poplar trees in plantations of Guilan province.

Based on the obtained results, it can be suggested to use the crown ratio index in order to select a suitable species for wood cultivation.

Climate change and global warming is one of the major challenges in the context of sustainable development, which is due to increasing concentrations of greenhouse gases, especially carbon dioxide. Afforestation is one of the practical and simple ways to reduce atmospheric carbon dioxide and increase carbon uptake in the soil. Therefore, the purpose of this study was to investigate the trend of soil carbon sequestration in Populus deltoides plantation located on different elevation classes.

Three sites (Mahdasht, Pahnekola and NaghibdehMazde) were selected at elevations between 150 to 1200 m in Sari city. Quantitative variables including diameter at breast height, total height, basal area of all trees with a diameter more than 7.5 cm were recorded (full inventory method). Ten soil samples were taken at a depth of 0-10 cm in each site using the core method in order to study soil physical (moisture, texture and bulk density) and chemical properties (pH, EC, nitrogen, phosphorus, potassium and organic carbon).

The highest diameter (27.83 cm), height (21.13 m), basal area (0.046 m2) and volume (2.11 m3) was observed in Mahdasht and the lowest values ​​were observed in Pahnekola. The lowest amount of pH (6.26±0.04), EC (0.3±0.01 ds/m), total nitrogen (0.11±0.01 %), potassium (169.49±25.00 mg/kg) and organic carbon (1.43±0.06 %) were observed in NaghibdehMazde (highest altitude). The highest and lowest rate of carbon sequestration was observed in Mahdasht (lowest altitude) and NaghibdehMazde (highest altitude), respectively. In general, in lower altitudes, poplar trees had a much better diameter growth than higher altitudes.

According to results, it can be stated that planting Populus deltoides in lower altitudes can be a suitable approach to reduce the concentration of atmospheric carbon dioxid.

Studying and evaluating the canopy gaps structure provides an accurate understanding of the process of forest stands dynamics as well as natural disturbances that play an important role in the future management of the forest ecosystem. The purpose of this study was to investigate the relationship between gaps and quantitative and qualitative characteristics of regeneration in the natural forest of Haftkhal in Mazandaran province.

For this purpose, gaps in the area were identified and recorded. Then the characteristics of collar diameter, height, seedling abundance in growth stages were recorded. According to the smallest and largest gap area, gaps divided into three classes of small (less than 300 m2), medium (300 to 600 m2), and large (more than 600 m2).

The results showed that gaps area was 3.65% of the total study area. In terms of area, 85% of the gaps were in small and medium-sized classes, which could indicate small-scale disturbances. The relationship between the gap area and perimeter and the study of Miller's elongation index showed more elliptical shape in small gaps to a circular shape in large gaps. The value of the Miller elongation index in small, medium and large gap area classes was 0.42, 0.59 and 0.86, respectively. The results showed that 85% of the regenerations in the gaps were related to the beech species. The highest frequency of regenerations was in the pole stage with a diameter of less than 5 cm and a height of 4 to 8 meters, which is an essential factor in starting the competition for light. Comparisons also showed that the frequency, diameter growth, and height growth of regenerations decreased significantly with increasing canopy gap area due to ecological needs, especially shade-tolerant growth of beech species, which provided by small canopy gap area.

Finally, the results indicate that pathways smaller than 600 m2 have more suitable conditions and in forest management, the creation of gaps larger than 600 m2 should be avoided as much as possible.