جستجوی مقالات مرتبط با کلیدواژه « تنوع زیستی » در نشریات گروه « اکولوژی »

Changing the Land-uses of forests effects biodiversity and other ecosystem components. There is little information about biodiversity and soil characteristics in different Land-uses in Zagros forests. For this purpose, the effect of changing natural oak forests to coniferous plantations, deciduous plantation, rangeland, and agricultural on the biodiversity of herbaceous species and soil characteristics was investigated in the forests of Chardavol river, Ilam, in 2018. In each of the land uses, 5 square-shaped sample plots with dimensions of 20 × 20 meters were randomly taken, and in each of the main plots, four 1.5 × 1.5 square meters plots were used to check the herbaceous plant species. In order to check soil characteristics a mixed sample of soil was prepared at two depths of 0-5 and 5-15 cm in each plot. The results showed that different land uses have significant differences in terms of Shannon-wiener diversity and Margalof richness of herbaceous species. The highest value of Shannon-wiener diversity index was observed in rangeland and the lowest was observed in agricultural land uses. Also, the highest richness of herbaceous species was observed in rangeland. The results of soil characteristics at two depths showed that phosphorus and nitrogen were affected by land use and soil depth. The results show that the change in land use from the natural oak forest to agriculture and forest plantation has caused a decrease in biodiversity and richness of herbaceous species. Also, the change of land use to agriculture and forest plantation has caused an increase in salinity, bulk density, and a decrease in organic matter.

Protecting wetlands and the life in them requires recognizing the biodiversity of these ecosystems. Waterfowl and shorebirds that are ecologically dependent on wetlands are used as environmental indicators. This research was conducted in the winter of 2021 in order to investigate the species diversity of wetland birds in Poldakhter city. Half-winter census data for a period of 13 years (2009-2020) was received from the General Environment Department of Lorestan province. Simpson's photo index and Simpson's dominance were used to investigate the species diversity of Poldakhter wetland birds. During the statistical period under review In Poldokhtar wetlands, 10 orders out of 19 orders, 16 families out of 84 is and 60 species out of 545 species identified in Iran were counted and recorded, which were 52.6 percent of the order, 19.04 percent of the family and about 11 percent, respectively. Iranian bird species have lived in Poldokhtar wetlands. 68.3 percent of Poldokhtar wetland bird species are in the category of unprotected and normal species, 26.67 Percent in the category of protected and protected species and 5 Percent that include species. Vanlellus gregarious, the world's highest conservation species (CR), and Aythya ferina, a vulnerable species (VU), Phoenicopterus minor, and Phoenicopterus minor Oak duck (Aythya nyroca) live in correct the endangered species (NT) category. In Poldokhtar wetlands, 53.3percent of birds were wintering birds, 30 percent were migratory birds, 8.3 percent were summering and hatching birds, 6.7 percent were normal (four seasons) and only 1.7 percent were summering birds without hatching. The results of the investigation of species diversity indicators of Poldakhter wetland birds showed that the year 2013 had the lowest species uniformity and the year 2018 had the highest amount of species diversity. Therefore, Poldakhtar wetlands are one of the important wetland habitats in the region and play an important role in the migration of waterfowl and wintering waterfowl.

Conservation and development of biodiversity are some of the most important issues in lake management. Calculating and studying biodiversity is a difficult, time-consuming, and costly process, and there is no well-established and planned biodiversity guidance. The purpose of this study was to evaluate the significant reduction of Parishan lake biodiversity and its changes due to the reduction of habitat over fourteen years. Census data from 1997 to 2011 were collected and analyzed. In this study, based on the number of species in different conservation categories, 64 species of least concern (LC), 4 endangered species (NT), 2 endangered species (VU), and 1 endangered species (EN) were identified. The frequency of each family was observed with a total of 135347 birds. Most of the birds observed belonged to the Eurasian coot (Fulica atra) species of the Rallidae family. Some biodiversity indices (Simpson, Shannon-Wiener, and Camargo) were used to investigate the species biodiversity and evenness of birds during the years 1998 to 2012. The results showed that the Simpson index of 0.925 in 1998 to 0.348 in 2008 year. It was the second year that showed an increase in biodiversity over an eight-year period, and the Camargo Index confirmed the same results. To achieve this, Ecological Methodology software was used. Generally, the results of this study showed that decreasing the water level of Parishan lake significantly reduced the biodiversity of many species.

Soil macrofauna plays a critical role in the development of soil structure and provides a variety of ecological functions. The present study aims to compare the biological index of soil macrofauna in broadleaved, coniferous, and mixed stands during growing and resting seasons in Geno protected area, Hormozgan Province, Iran. After a half-hectare broadleaved stand, a half-hectare coniferous stand, and a half-hectare broadleaf-coniferous (mixed) stand in the Geno protected area were selected to identify the soil macrofauna and measure the physical, chemical, and soil properties and their relationship with soil macrofauna, 10 soil samples were randomly collected from different soil depths including under the canopy to a depth of 15 cm, during the growing and resting seasons. The macrofauna were isolated from the soil samples and were then submitted to a laboratory for chemical analysis. Data were analyzed using SPSS26 software. Richness, evenness, and biodiversity indices were compared using t-test, and then ANOVA and Duncan tests were used to compare physical and chemical properties of macrofauna soil in growing and resting seasons. The results showed a significant difference biological index of macrofauna in broadleaved, coniferous, and mixed stands in the growing and resting seasons.Tperesence of macrofauna the soil, their great diversity and activity as one of the key factors in the supply of nutrients and soil fertility can play a constructive role in the health of ecosystems and maintaining its balance

Safe sites are microhabitats that provide the basic requirements for seed dormancy breaking, germination, and seedling establishment. They reduce threats from seed predators, herbivores, pests, and competitors. We identified and assessed living and non-living safe sites in the rocky outcrops and their effects on species diversity at six sites along a rainfall gradient in the north of Iran. Four dominant plant species were considered as living safe sites, but crevices and rocks were attributed as the non-living safe sites. Ten transects of 10 meters long were established at each site, along the rainfall gradient. Plant abundance and canopy cover were measured for all species along the transects. Soil physiochemical properties, moisture and temperature were recorded at the safe sites along the transects and their adjacent open areas. Rainfall had a significant effect on species diversity in non-living and living safe sites. Abundance and evenness increased in all safe sites; diversity indices increased in living safe sites and decreased in non-living safe sites. Soil nitrogen, carbon, potassium, and clay were significantly higher under the nurse shrubs. Results of this research indicate the crucial role of safe sites in maintaining the diversity of plant species under the harsh conditions of stressful environments on the limestone outcrops.

The reduction of biodiversity and its adverse effects on plant and animal species is one of the consequences of global warming.  The wide spread of non-native species has inherent negative effects on other species and ecosystems and may pose a double and more serious threat to biodiversity in the future due to climate change. Knowing the future distribution of these species can be used for biodiversity conservation. In the current study, the distribution of non-native stone moroko fish was predicted under two optimistic and pessimistic (RCP 2.6 and RCP 8.5) scenarios for the years 2050 and 2080 by the MaxEnt model. The results showed that the performance of the model in predicting species distribution was excellent (0.988) based on the Area Under the Curve (AUC) criterion. In addition, it is predicted that the distribution of the species is likely to increase significantly (more than 100%) in all years and optimistic and pessimistic scenarios. Therefore, managers and decision-makers should consider the significant expansion of this species in the future as well as, its potential effects on biodiversity and take necessary and appropriate management actions.

One of the goals of natural resource management is to preserve biodiversity in natural ecosystems. In this research, the effect of topographical factors on species diversity in the elevation gradient of Grain mountains rangeland in Delfan County in 2022 was investigated. In this elevation gradient, five habitats were selected. Vegetation typing was done by the physiognomic method and in the Key area of ​​each plant type, vegetation sampling was done by a random-systematic method. The sampling plot area was determined by the minimum area method (one to four square meters) and the number of plots was determined by statistical method for each habitat, 30 plots. Three transects with a length of 100 m were deployed in each habitat and 10 plots were sampled along each transect (30 plots per habitat). Species were collected from the surface of the plots, identified and their vegetative form was determined. The Biodiversity of plant species was calculated using dominance, Shannon-Wiener and Simpson diversity indices, Margalf and Mannhing richness index and homogeneity index Hill using PAST software. A One-way analysis of variance was used to compare the differences between sites and the Duncan test was used to compare the means. In order to determine the most important factors affecting species diversity changes, principal component analysis was used. The results showed that changes in height, slope and direction had a significant effect on the indices of diversity, richness, homogeneity and dominance at the level of all plants. At the total level of plants, the highest values ​​of richness and diversity indices were observed at an altitude of more than 2600 meters and dominance at an altitude of 1850 meters. In low slope (0-15%) the dominance index had the highest value and the indices of diversity, richness and uniformity in slopes higher than 30% had higher values. Most indices in northern, northwestern and western geographical directions had higher values ​​than in other directions and the difference was significant (P <0.01). The results of the principal component analysis showed that high altitude and slope and north, west and northwest directions have the most impact on species diversity in the study area. In general, it can be concluded that due to the number of livestock exceeding the grazing capacity and human activities in the lower elevations of the studied area, species diversity and richness have decreased.

Ecosystem services are usually divided into four categories: (a) provision services, (b) regulating services, (C) cultural services and (d) supporting services. Ecosystem services are managed in agroecosystems primarily for food production. But, agricultural ecosystems provide provision, regulating and cultural services for human society. These services respond strongly to human socio-economic needs. Quantifying the various services and functions of agroecosystems is one of the most important effective strategies in order to increase attention pay to these services. Therefore, the purpose of this study was evaluation and quantification of ecosystem services in wheat (Triticum aestivum L.) agroecosystems of Dasht-e-Naz, Sari.

This experiment was performed as an unbalanced completely design in wheat agroecosystems of Dasht-e-Naz, Sari (Mazandaran province), during 2019-2020. In this study, 9 wheat plots with 4 cultivars including Tirgan, Ehsan, Collector and N-92-9 were surveyed and monitored. In this study, some ecosystem services such as insect and weed biodiversity (using Shannon-Weiner, Simpson, Margalf, Uniformity and Menhinick indices), soil microbial respiration, carbon sequestration, organic matter, abundance of earthworms, grain yield, protein content oxygen production, and soil protection (by the stability of aggregates) were evaluated and quantified. Soil samples were taken from a depth of 0-30 cm before wheat planting in November 2019 and after harvest in June 2020 for assessment of rate of microbial respiration, organic matter and carbon sequestration. Also, oxygen production was estimated based on net primary production. Sampling of yield and plant biodiversity was harvested based on W pattern and with quadrate 0.5 × 0.5 m2. All samples were moved to the crop research laboratory of Gorgan University of Agricultural Sciences and Natural Resources and the plant flora was determined by genus and species names.

The results showed that crop management and performance of intensive agricultural system were effective on providing many services of ecosystems in wheat fields of Dasht-e-Naz, Sari. These services are influenced by several factors such as cultivar type, crop rotation, tillage, etc. The results showed that the effect of different cultivars was significant on grain yield and protein percentage. The highest percentage of grain protein as a provision service was obtained from Ehsan cultivar (12.15%) and the lowest content was obtained about 11.42% from N-92-9 cultivar. The highest wheat grain yield and oxygen production were calculated from plots under Collector cultivar. In additional, the highest amount of carbon sequestration (2.33 ton/ha) and microbial respiration rate in before planting and after harvest (76.46 and 38.52 mg CO2 per kg of soil per day, respectively) belonged to plot 15. Also, it was determined that plot 15 was better than other plots from soil protection service view based on the diameter mean weight index (MWD) and the geometric mean diameter index (GMD). In this research, three beneficial insects (biodiversity assessment) were observed such as Coccinella septempunctata Linnaeus and Aphidius matricariae, and Chrysoperla carnea. The highest values of Shannon-Weiner and uniformity indices of weeds were as 2.63 and 0.82 in plots 23 and 15, respectively. Furthermore, Shannon-Weiner and uniformity indices of insect communities were obtained as 2.07 and 0.94 from plot 22, respectively.

 Generally, carbon sequestration, organic matter, microbial respiration, earthworm abundance, aggregate stability index, average weight diameter (MWD) and geometric mean diameter index (GMD) were better in plots 14 and 15 under wheat cultivation  than other plots. The results of this study showed that crop management and implementation of intensive agricultural system were effective in providing many ecosystem services in wheat fields in Dasht-e Naz region of Sari. So that, these services were affected by several factors such as cultivar, crop rotation and tillage methods.
Acknowledgment
The authors gratefully acknowledge the financial support of Gorgan University of Agricultural Sciences and Natural Resources and Dr. Hamid Sakinin for his help.

The main purpose of this study is to investigate the quantitative and qualitative characteristics of dominant tree species and their regeneration status in the Arasbaran forests. Data were collected by transect sampling and regeneration was assessed by plot with an area 100 m2. In the sample plots, we recorded information on species type, diameter at breast height, height, quality of seedlings and the presence of cut trees. Three customary areas, Hoosh, Dinehvar, and Aghamirloo villages were selected for study in Arasbaran protected area. The values ​​of species diversity were calculated using the species diversity indices of Shannon Weiner and inverse Simpson. The results showed that the number of trees per hectare in the customary areas of Hoosh, Dinehvar and Aghamirloo were 498, 388 and 260 trees per hectare, respectively. The basal area of ​​the trees was 10.77, 7.78 and 5.76 m2 per ha in the Hoosh, Dinehvar and Aghamirloo, respectively. The regeneration status showed that hornbeam (Carpinus betulus), oak (Quercus macranthera) and maple (Acer campestre) had 828, 506 and 360 seedlings per hectare, respectively. The volume of woody debris of hornbeam, oak and maple species were 2.56, 1.28 and 0.19 cubic meters per hectare, respectively. The stand regeneration were in the middle and good classes in terms of vitality. About 27.5% and 72.4% of the seedlings had good and medium quality, respectively. The crown cover percentage were between 50 and 90 percent, so the canopy of these areas was semi-closed. The results showed that in Aghamirloo and Hoosh customary area, the diversity of Shannon Weiner species and Simpson inverse index had the highest and lowest value, respectively. Uncontrolled human interventions and over harvesting in Arasbaran forests have caused significant quantitative and qualitative changes in these forests and the dependence of local communities on these forest have impacted on the species diversity.

Iintercropping can be considered as one of the ways to increasing the yield and production stability per unit area. So, this experiment in order to investigate yield components and yield as well as competition indices in triticale and winter vetch intercropping under different tillage systems done.

The experiment was conducted as a split plot based on randomized complete block design with three replications at the Bu-Ali Sina University. Three tillage levels (conventional, reduced and no tillage) were set as main plot and five planting patterns) sole cropping of winter wetch (M) and triticale (T) and intercropping of 50T+50M, 67T+33M and 33T+67M) were considered as sub plot.

Results showed that tillage and planting pattern had a significant effect on number of spikes per m-2, number of seeds per spike, 1000-seed weight and biological and grain yield in triticale. Also, such significant impact was recorded for the number of pods per plant, number of seeds per plant, 100-seed weight and biological and grain yield in winter vetch. The highest grain yield for triticale and winter vetch was relvealed at sole cropping under conventional tillage. Highest LER (1.30) and RCC (4.60) were obtained from 50T+50M treatment. The positive values of the aggressivity and the higher values of the competition ratios in 50T+50M treatment for triticale indicates the competitive superiority of triticale over winter vetch or better using of inputs in intercropping. Actual yield loss and intercropping advantage were positive in triticale and winter vetch.

Therefore, by estimating the competitive indices in order to evaluate the ststuse of the two species in the intercropping, it was determined that in the different intercropping treatments, therewas no actual yeild loss which shows the superiority of intercropping over the sole cultivation of the two species. So, planting patterns of 50T+50M in addition to creating biodiversity and ecosystem sustainability, causes maximum productivity of the land.

Develop of sustainable green spaces in cities will lead to unsustainability, if this development is done without evaluating the factors affecting the resilience of plant species and applying inappropriate planting pattern due to ignore the aforementioned factors. The main purpose of this study is to evaluate factors affecting the resilience of plant species for the development of urban green space in Qom and providing a list of plant species compatible with specific semi-arid environmental conditions. This study tries to quantify the qualitative indicators of plant species characteristics to evaluate their comparison in relation to resilience criteria. For this purpose, beforehand the criteria and sub-criteria of plant resilience were determined based on related literature and the authors’ experiences. Then, according to the criteria of plant resilience to soil, water, climatic conditions, urban pollution and ecological conditions of the region, plant species is properly evaluated and prioritized by Fuzzy Hierarchical Analysis (FAHP) and FTOPSIS. Consistent findings indicate that from the experts' point of view, the most crucial factors affecting plant resilience in green space of Qom are, water (0.273), soil (0.254), climate (0.199), Ecological conditions (0.180) and urban pollution (0.092) accordingly. Moreover, plants' resistance to soil salinity (0.075), resistance to evapotranspiration conditions (0.069), resistance to water shortage (0.067), resistance to water salinity (0.067) and resistance to adverse environmental factors (0.063), were promptly recognized as the most relevant sub-criteria of plant resilience. Finally, tree species including Tamarix gallica, Populus euphratica, Eucalyptus globules, Aianthus altissima, Pistacia chinensis, Pinus Mugo and black pine and Pinus nigra are determined as resilient species. The allocated proximity coefficient is 0.90, 0.89, 0.88, 0.86, 0.85, 0.85 and 0.84 respectively. As result, aforementioned species can be widely used in urban green spaces based on the local facilities and conditions of each area of the city.

Pollination is an ecological service with high economic values related to human and ecological wellbeing. This study aims to evaluate the correlation between landscape complexity and pollination service (bee) in Qazvin province at the landscape scale. Landscape pattern metrics (Number of Patches (NP), Patch Richness (PR), Edge Density (ED), and Shannon Index (H)), as a proxy of landscape complexity, were calculated by the model builder in the ArcGIS and pollination service was generated by InVEST. The correlation between landscape complexity and pollination service was evaluated by SPSS software. Results of the correlation between landscape metrics and pollination service, using Linear regression, showed that H has the highest and the most significant relationship with pollination at the 0.01 level (0.420**). Correlation between other metrics and pollination was found to better explauned by Quadratic regression, showing a significant correlation with NP (0.171**) and PR (0.352**) at the 0.01 level and a non-significant relationship with ED (0.002). It was concluded from our results that in the low NP and PR, correlation is high and positive, and in the high NP and PR, correlation is negative, indicating the effect of fragmentation on pollination service. The results of this study can be used in agricultural system planning and biodiversity management to preserve the ecological processes.

Phytoplankton is one of the main components of wetlands, which plays a vital role in providing nutrients, oxygen for other organisms, stabilizing nitrogen and carbon dioxide. In the meantime, the current status of Lake Urmia highlights the need to conserve and protect wetlands related to these ecosystems and their living and non-living components. Therefore, this study was conducted to assist in the restoration of Lake Urmia by monitoring the hydrobiological status of Solduz wetland. Field surveys and sampling of Solduz Wetland were carried out from 6 stations in summer and winter of 2016. Sampling was performed using a vertical rotor with a diameter of 10 cm. The effects of physicochemical factors and temporal variations on the diversity, abundance and biological characteristics of phytoplankton in the ecosystem were investigated. In total, 49 phytoplankton species were identified from the Solduz wetland: 17 species belonging to green algae, 16 species belonging to diatoms and 9 species belonging to cyanobacteria and some others species. The results of this study showed the presence/absence of the mentioned algae may be caused by changes in the physicochemical especially temperature, nitrate, phosphate, pH and electrical conductivity which occur naturally in different seasons. So that the population density index and biodiversity indices such as species richness, species diversity and dominance was observed in the warm season more than the cold season. The results of this study can assist executive managers in Urmia Lake monitoring plans for better management and utilization of related wetlands of Lake Urmia.

Biodiversity is one of the important concepts in ecology and vegetation management, and plays an important role in the health, production, and evaluation of ecosystems. Species diversity is a major part of biodiversity and one of the most important parameters of ecosystem changes. In this research, the data of the rangeland evaluation different climate zones of Isfahan province were used in five range sites of Alavijeh, Charmshahr, Khondab, Kalahroud and Mouteh to study the variations of the diversity and richness of species with production in the steppe rangelands. The sampling was done on random -systematic and the density and percent of vegetation conopy of each species along the transects using constant plots and production are also estimated by double measurement using the coating. The diversity numerical indices were calculated using Excel, PAST, Ecological Methodology and PRIMER softwares. In order to investigate the relationship and presentation of the model between species diversity indices with parameters (production, density, and canopy cover percentage) from pearson correlation analysis and multivariate regression analysis were used in spss software. The results from the correlation analysis mirror the significant correlation between some species diversity indices and vegetation parameters. The results from the correlation analysis show mirror the significant correlation between some species diversity indices and plant cover parameters. The correlation coefficient of different indices of biodiversity in different regions with density of 0.76 to 0.98, vegetation percentage is 0.74 to 0.92 and production is 0.71 to 0.92. Also, the results from the multivariate regression analysis reflect the effect of the density, vegetation of herbaceous broadleaf (%), and total Coverage on the production. In the rangelands under study, Menhinickchr('39')s richness index was able to justify 13.1% of the changes of herbaceous broadleaf productions. Among the species diversity indices, Hill’s index N2, Simpson index, and McIntosh index and among the evenness indices, Camargochr('39')s index and Shannon-Wiener’s index had the most connection with production and they can justify its changes.

The present study was performed to identify diversity indices of herb layer functional groups and its relation to physiographical factors in central Zagros forest, Lorestan. For this purpose, sampling of herbaceous plants was conducted randomly in plots of 2×2 m (n=50) in site. All plants were classified to functional groups including forbs, graminoids and legumes, also Raunkiaerchr('39')s life-forms. Diversity values (Richness, Shanon-weawerchr('39')s diversity and Hillchr('39')s evenness indices) were measured in each plot. Totally, 103 plant species were identified which belong to 27 families and 82 genera. Results indicated that aspect influenced the forbs as well diversity indices of graminoids and legumes, but slope and altitude had no effect on diversity indices. In research site, aspect had important impact on plant distribution and diversity of plant functional groups. Generally, it can be stated that ecological and managemental factors including landuse changes and grazing intensity in Zagros region influenced the plant species composition.

Iran has high vegetation diversity due to different climates and ecological conditions. Golestan province is one of the most diverse vegetation provinces in the country. Among the plant species of this province, the Juniper genus, with the presence of 6 native species, is one of the few coniferous species which is an important part of the under story vegetation flora of the area. Chahar Bagh Juniper Reserve with an area of 600 hectares, located in the Southern of Gorgan, with altitude range of 2150 to 3150 meters above sea level, was selected as a study area. In order to identify plant species and introducing the floristic composition, biological form and geographical distribution of plants in the area, Plant specimens were collected and identified during the vegetative seasons of 2017 and 2018. The results show that in total, the under story flora of Char-Bagh Juniper Reserve has 111 taxa including 31 families and 84 genera. The largest genus, belonged to the Poaceae (12 species), Lamiaceae (11 species), Brassicaceae (9 species), Asteraceae (8 species), Apiaceae (7 species) and Alliaceae (7 species), respectively. According to Rankiairechr('39')s plant biological form, 44% of plants belong to the hemicryptophytes, 22% in trophytes and 12% in comfit. An examination of the geographical range of vegetation in the area reveals that 61.3% of identified plants belong to Iran-Turanian vegetative zone and 7.2% of the species have European-Siberian origin and at the same time, 2.7% of the species share the same area. In addition, 9.9% of the species are common between the Iran-Turanian and Mediterranean vegetative regions and the remaining 18.9% are related to other vegetative areas or are shared between several vegetation areas. The conservation status of the plant species in the area showed that none of them were endangered. One species is in the group of less threatened (relatively vulnerable) plants and one species is in a group with insufficient information on their condition.

Habitat and ecosystem fragmentation and, consequently, the loss of landscape connectivity are major causes of biodiversity destruction, leading to disruption of material, energy, and information flow at the landscape scale. Given the importance of this issue, the current study aimed to evaluate the ecological connectivity and spatial planning of Qazvin Province, in order to re-establish and protect material, energy, and information flow corridors, using a landscape ecology approach. With that in mind, land use/land cover map was used to identify ecologically functional areas and to map barrier effect and ecological connectivity indicies by mathematical modeling techniques using model builder algorithms in Geographic Information System (GIS). Appropriate patches were, then, spatially selected for restoration and conservation across the landscape. The results showed that 90% of the province has the ecological function, but 10% of the area lacks the function. Three percent of the area has lost its ecological function by physical barriers such as road networks and industrial and residential expantions, and 7% of the area lost its functionality due to anthropogenic effects. In this research, four corridors were identified for spatial planning. Results of this study can be used for management of protected areas and land use planning, as well as environmental impact assessment and envuronmental strategic assessment.

Application of organophosphate pesticides especially diazinon is a common phenomenon that cause pollution wide area of terrestrial and aquatic ecosystem. Therefore, an investigation of the effect of this organophosphorus pesticide on some beneficial soil microorganisms was investigated. In a laboratory research, diazinon in the concentration of 0, 4, 12, 50 mg.kg-1 was added to the soil and incubated. Then the soil sampled in different time of incubation, after preparing proper dilution, fungi, actinomycete, pseudomonas, intestinal bacteria and azotobacter cultivated in the specific medium in three replicates. The analysis was considered as completely randomized design (repeated measurement test). The effect of diazinon on biodiversity index of the cultivable microorganisms also evaluated.  In comparison to the control, after application of 4 mg.kg-1 diazinon in the soil the frequency logarithm of actinomycete and azotobacter decreased and pseudomonas increased. The frequency logarithm of intestinal bacteria and fungi were similar to untreated soil. In concentration of 12 and 50 mg.kg-1 the frequency logarithm of all the studied microorganisms reduced. Soil richness in the treatment of 4 mgkg-1 diazinon was more than control and significantly decreased in other concentrations. Biological diversity and evenness decreased in all concentrations of applied diazinon but dominance index increased in comparison with the control. Therefore, most studied soil microorganisms were incompatible with these concentrations of pesticide and this could reduce soil health and fertility.

<p</pThis study was conducted to compare regeneration density and biodiversity indices in the natural and man-made gaps in the Tutaki forests of Siahkal in Gilan province. Data were collected from 60 gaps (including 30 natural and 30 man-made gaps). The results of species composition indicated that three tree species including Diospyros lotus L., Carpinus betulus L. and Alnus glutinosa L. in both gaps. In the shrub floor, for both gaps and all kinds of species, the  average number in hectares of man-made gaps (with the exception of  Ilex) was  higher than that of natural gaps. Ilex & Crataegus pentagyna indicated the significant difference at 95% level between 2 gaps. Also, the regeneration density for all species at the natural gaps was more than man-made gaps and the average number in hectares for Diospyros lotus, Alnus glutinosa and Acer sp indicated the significant difference at the 95% level between the 2 gaps. So the regeneration of Fagus orientalis Lipsky was observed only in the natural gaps. The results of biodiversity indices  also revealed that in natural gaps, the average of diversity, evenness and richness had the highest value, whereas in shrub, the average of these indices had the highest value.

The present study aimed to examine the effects of stratification on tree layers diversity and some features of beech trees in Hyrcanican forest, Guilan, Asalem. Also, interactions between tree diversity and some characteristics of beech leaves was investigated. The Nine research plots are sampled as a gradient from pure beech stands to mixed stands with up to 9 deciduous tree species with three replications for each. Each research site had a size of 2500 m2 (50 m × 50 m). In each tree layers, diversity indices, crown diameter, DBH and frequency of beech tree were measured within plots. The results showed that the highest value of richness and diversity indices belonged to the second tree layer. The highest amount of basal area and crown diameter were observed in the first tree layer (overstorey). Regression analysis showed that tree layer diversity and richness measures were significantly positively correlated with fresh and dry weight of beech leaves. Correlation coefficients indicated that beech frequency was significantly positively correlated with weight of fresh leaves and negatively with dry weight of leaves. There was significantly negatively correlation between basal area of beech trees with fresh and dry weight of leaves within stands. In general, it can be stated that diversity-functioning relationships might occur in the tree-layer of the deciduous beech forest under investigation.