جستجوی مقالات مرتبط با کلیدواژه "density" در نشریات گروه "کشاورزی"

Introduction : 

Tulip flower (Tulipa L.) from the family Liliaceae is a bulbous and monocotyledon plant that has the highest level under cultivation among this family group. Tulips can be propagated by seeds and bulbs. Its seeds produce bulbs up to two years after planting and it takes six years for the bulbs to reach the flowering stage. In fields, the quality characteristics of flowers can be changed to some extent by changing some planting characteristics such as planting pattern and plant density. Some researchers have reported changes in the quantitative and qualitative characteristics of various crops and orchards, including ornamental plants, with changes in planting pattern and plant density. One effect of changes in planting patterns and plant density is alterations in photosynthesis and plant growth regulators. The purpose of this study was to identify the best planting pattern and determine the optimal planting density, as well as to examine the impact of these factors on the quantitative and qualitative characteristics of tulip (Tulipa L.) cv. 'Spryng'.

To evaluate the effect of planting pattern and density on growth and flower characteristics of tulip cv. ʹSpryingʹ, present study study was conducted as a factorial experiment based on completely randomized block design (RCBD) with 3 replications in 27 plots. The first factor was three planting patterns (square, triangle and rectangle) and three planting densities (25, 45 and 65 plant/m2) as the second factor. Morphological and physiological traits such as height, length and diameter of stem, leaf and flower, flowering time, cut flower number, flower longevity, number, diameter and weight of bulb and bulblet, and the content of chlorophyll and carotenoid were measured. Statistical analysis of data was performed with SAS 9 software and mean comparison of the data with LSD test at 5% probability level. Graphs were drawn in Excel.

Results showed that the maximum number of cut flowers (59.90) was counted in plants cultivated in triangle cultivation design with planting density of 65 plants/m2. The lowest time to start of flowering (69.30 days) and the highest content of leaf chlorophyll (13.57 μg/ml) was obtained in plants cultivated in trianle cultivation design with planting density of 45 plants/m2. The most flower longevity (12.73 day) and the highest content of carotenoid (1.68 μg/ml) was obtained in plants cultivated in square cultivation design with planting density of 45 plants/m2. The height of the flowering stem is one of the important traits for the marketing of cut flowers. The results of the present study showed that the height of the tulip plant was affected by plant density and planting pattern. This result was consistent with the results reported by some researchers. At low plant densities, long plant spacing reduces plant competition for water and nutrient uptake, resulting in larger plant growth and leaf size. Also, long plant distances cause the roots to develop and grow, and the leaves to grow and thicken. Increasing the vegetative competition of adjacent plants at high densities causes photosynthetic organs to be placed in the shade (change in the quantity and composition of the received radiation spectrum in the shade leaves), which has a great effect on the balance of plant growth regulators, resulted in longitudinal and superficial growth of plant organs. It intensifies the longitudinal growth of the petiole and accelerates all the developmental processes of the plant. Plant morphology and angle of leaf deviation can also be effective in increasing leaf size. Uniform distribution of plants and greater absorption of light and nutrients increased leaf length and width. The results revealed that plants compete for light and nutrients, and in these competitive conditions, roots and stems are taller than optimal, and the distance between nodes increases. The effect of planting pattern on flowering process can be related to changes in plant photosynthesis and the availability of photosynthetic materials for the developing reproductive parts. Changes in planting distance or pattern can alter inflorescence characteristics by affecting root growth and modifying the production of plant growth regulators in the roots. These regulators are then transferred to the aerial parts, influencing inflorescence characteristics. Adjusting the planting distance or pattern can also impact various traits of bulbs and bulblets in bulbous plants. Competition for receiving maximum light and photosynthesis is a key factor in changing bulb and bulblet traits. This competition is influenced by planting arrangement and plant density. Some studies have shown that planting pattern and plant density affect the amount of plant pigments such as chlorophyll and carotenoids, the main reason being the difference in light intake.

To study the effect of the pre-mix herbicide, clodinafop propargyl+ metribuzin (29% WP), to control weeds of wheat fields an experiment was carried out in a randomized complete block design with 8 treatments and 4 replications in Alborz (Karaj), Fars (Darab), Semnan (Shahroud), and Khorasan Razavi (Mashhad) during 2021-2022. The treatments included the application of the herbicides pre-mixture herbicide Clodinafop propargyl+ Metribuzin ("CloMetri" is used as an abbreviation) at the rates of 500, 600, and 700 g/ha, Metsulfuron methyl+ Sulfosulfuron (Total@, 80% WG) at the rate of 45 g/ha, Mesosulfuron+Iodosulfuron+ Diflufenican (Othello@, 8.25% OD) at the rate of 1.6 l/ha, Clodinafop propargyl (Tapik@, 8% EC)+ Tribenuron methyl (Geranestar@, 75% DF) at the rate of 0.8 l/ha + 20 g/ha, Tapik@ + Bromoxynil+ MCPA (Bromicide MA@, 40% EC) at the rate of 1 + 1.5 l/ha, , and a Weed-free (Hand-weeded) control. The results showed that the application of herbicide treatments significantly reduced weed density and dry weight and increased grain yield of wheat. The Clometri (700 g/ha) showed control efficacy against Veronica persica Poir., Malva neglecta Wallr., Hirschfeldia incana (L.) Lagr.-Foss., Fumaria officinalis L., and Centaurea iberica Trevir. ex Spreng., ranging from 70% to 85%. Overall, compared to the other herbicides in the experiment, the efficacy of clometry herbicide in controlling most weed species was weak and unsatisfactory. Therefore, its use is not recommended as an option for weed control in wheat fields.

Japanese brome (Bromus japonicus Thumb.) is known as the most important grass weed in the wheat fields of Sistan & Baloochestan. Using an additive series design we conducted field experiment over 2008-09 and 2009-10 growing seasons at Zahak, Zabol to characterize interference between wheat and Japanese brome. Wheat densities were considered at five levels of zero, 350, 400, 450, and 500 plants per m2 and Japanese brome at four levels of zero, 100, 200, and 300 plants per m2. Here, we estimated the intraspecies and interspecies competition coefficients, relative competitive ability and niche differentiation. For both years of experiment and in both stages of tillering and physiological maturation of wheat, the intraspecies competition coefficient of wheat ( ) was negative and the interspecies competition coefficient ( ) between wheat and Japanese brome was positive. The relative competitive ability of wheat ( ) showed that each Japanese brome plant was able to have a negative effect on the dry weight of a wheat plant equal to 2.5 wheat plants. The coefficient  showed that the competitive potential of each wheat plant in the tillering stage was 9.5 and 3.3 times more than a Japanese bromus plant in the first and second years of the experiment, respectively. In the interference of wheat and Japanese brome, wheat had a higher competitiveness, especially at the tillering stage. No niche differentiation observed between wheat and Japanese brome and their ecological niche strongly overlapped, which it was more at the tillering stage.

Hemp (Cannabis sativa L.) is one of the oldest cultivated annual crops in the world belonging to the cannabaceae family and annual wind-pollinated broadleaf. It is originated in central Asia and considered a multi-purpose crop including stalk fiber (apparel, fabric, bags), stalk hard (animal bedding, mulch, biofuel, filter, and so on), seeds (nut, and snacks), oil (salad oil, cosmetic, shampoo, soap, oil paint, industrial oil, and solvent), leave and inflorescence (anti-microbe (hand soap), and agrochemical products (insecticide and herbicide). Weed competition for nutrients, water, and light led to decreased growth and yield of hemp. Mechanical and agronomical techniques are commonly used for weed management in hemp. Since mechanical and agronomical techniques are expensive and time-consuming, finding a new approach to save time and money is essential. Determination of weed critical period may facilitate arriving at this approach. The critical period of weed control (CPWC) refers to a part of the integrated weed management (IWM) program and is defined as a part of the crop growth cycle in which weeds must be removed for avoiding economic yield losses due to weed competition with crops for water, light, and minerals. On the other hand, CPWC is a period in which crops must be growth-free of weeds. Numerous agents' effects on CPWC include crop species and growth characteristics, crop density, crop variety, and crop planting pattern. The main goal of this study was to determine the effect of hemp density on CPWC and hemp yield and yield components' responses to the critical period of weed control.

A field trial was carried out in 2016 at the research field of Birjand University in South Khorasan Province, Birjand, Iran (latitude 32°, 86′, 49″ N, longitude 59°, 22′, 62″ E, and altitude 1491 m). Before sowing seeds, the field was fertilized with urea (250 kg ha-1) split at two times (sowing time, 2 mount after emergence), P2O5 (100 kg ha-1), and K2O (100 kg ha-1). The field was plowed with a mouldboard plough (30 cm depth), and then harrowing by a disk used for seedbed preparation twice, and finally, leveling the soil surface by leveler tools. Hemp has never been cultivated in this field. The hemp seeds were sown on May 4, 2016, in a cluster, 5 seeds in each hole with 60 cm between rows and 10 and 20 cm between plants in the row for 8 and 16 plants/m2, respectively. Sown depth was 3 to 4 cm. Crop emergence began about 2 weeks after planting. Two weeks after emergence (four weeks after planting), the plants were thinned to reach a determined density. The experiment was arranged in a randomized complete block design (RCBD) in a factorial arrangement with three replications. Each experimental plot was 6 m long, 3 m in width, and included 5 rows. Data were collected in three central rows. Treatments included six weed-infested periods (2 (WI2), 4 (WI4), 6 (WI6), 8 (WI8), and 10 (WI10) weeks after crop emergence (WAE)), in which weeds were allowed to grow to 2, 4, 6, 8, and 10 weeks after that control conducted by hand hoeing until harvest time. In weed-infested control (WIC), weeds were allowed to grow in all growing seasons duration. Six weed-free periods (2 (WF2), 4 (WF4), 6 (WF6), 8 (WF8), and 10 (WF10) weeks after crop emergence (WAE)), which weeds were hand hoeing control to 2, 4, 6, 8, and 10 WAE and then weeds were allowed to grow until harvest time. In weed-free control (WFC), weeds control in all season growth duration. The experimental treatments during the growing season of hemp are described in Figure 1. Seed hemp yield and yield components were determined at the end of the growing season.

Weed-infested and weed-free periods treatments have significant effects on the seed yield and yield components including flower number and seed number per plant of hemp (Table 1). Moreover, hemp density has a significant effect on the seed yield and yield components including flower number and seed number per plant of hemp (Table 1). Higher crop density led to limited CPWC since under weed-infested fields using higher crop density led to improved crop competition ability (Zimdal, 1993). (Hayat et al.,2003) reported that high crop density led to decreased seed yield of crops by increasing inter-species competition. (Purcell et al.,2002) demonstrated the seed yield of soybean depends on crop density whereas by increasing crop density firstly seed yield was increased but under high crop density seed yield was decreased. Therefore, using proper crop density is known as an important challenge to crop production. Flowers per plant, seed number per plant, and seed yield were affected by crop density. Results of this study demonstrated that under weed-infested fields using 16 plants/m-2 is more suitable than 8 plants/m-2 compared to weed-free in Birjand conditions (Dry climate)(Table 2).

A greater understanding of weed behavior can help with IWM strategies. The critical period of weed control determination is a key factor for IWM strategies that led to less introduction of herbicides into the environment, saving money and time, and so on. Data obtained from the results of this study revealed that more crop density led to a decrease in the duration of the critical period of weed control in hemp.

The phenomenon of desertification has always been considered as one of the most important challenges facing Iran, which has been aggravated by human and climatic factors in recent years. Therefore, it is necessary to implement anti-desertification plans and projects set through the Development planning to curb desertification and restore and improve degraded lands. In this regard, the severity of the phenomenon can be decreased by applying appropriate management solutions and methods and preventing its expansion and progress. Implementing anti-desertification management and rehabilitation projects according to the ecological conditions of each region improves the condition of the vegetation, strengthens the soil stability, and protects the soil from the risks of water and wind erosion. Therefore, analyzing different aspects of the anti-desertification projects which are planned and carried out by the government is required for improving management in the natural resources sector. One such measure can be the restoration of desert pastures with regard to unfavorable climatic conditions. Thus, this study set out to investigate the influence of anti-desertification management and restoration projects in improving soil stability indicators and vegetation characteristics.

This study was conducted in four sites located in the Yazd-Ardakan plain, including the seedling site, the water weed management site, the mulched site, and the enclosure site. The main species investigated in each of these sites was Haloxylon aphyllum. To this end, four transects were placed in the site at regular intervals. It should be noted that the transects were placed parallel and perpendicular to each other in flat and sloping areas, respectively. The number of plots on each transect was 15 and the area of the plots was 210 cm. Moreover, the index Plant characteristics such as canopy percentage, density, reproduction, and freshness of Haloxylon aphyllum species were measured. Finally, after collecting the required data, statistical analysis was performed using the SPSS software.

  According to the results of statistical analysis performed via independent t-test, a statistically significant difference was found in the percentage of vegetation and density at the error level of 1% in all investigated sites. Duncan's multiple range test revealed significant differences in mean values among treatments. The treatment associated with herbaz exhibited the highest mean values for vegetation cover (72.5%), plant density (75.4), regeneration (542.0), and vigor (33.61). Conversely, the treatment subjected to enclosure showed the lowest mean values for vegetation cover (68.1%), plant density (2.0), regeneration (111.0), and vigor (24.12).

Compared to the control area, the percentage of vegetation and density of the effective area was significant in the seedling site (where the seedling project is based on seedling irrigation), which is due to the lack of suitable conditions and rainfall in the seed establishment. The wastewater management site demonstrated increased vegetation cover and density due to enhanced water infiltration and readily available moisture, which facilitated plant establishment and growth. Similarly, the mulched site exhibited higher vegetation cover and density compared to the control, attributable to the creation of a subsurface moisture layer beneath the mulch, providing a favorable environment for seed germination and plant development In the enclosure site which is less affected by human changes, the amount of soil erosion and ecosystem destruction is lower than other sites in all dimensions, leading to the higher percentage of vegetation and plant density. The establishment and expansion of vegetation cover through various methods have been implemented in recent decades as a means to combat desertification and mitigate the damages caused by dust storms in arid regions. However, water scarcity poses a significant constraint. Consequently, it is recommended that, in the context of desertification management and rehabilitation projects in the Yazd-Ardakan plain, the most effective approaches be prioritized as follows: runoff water management, mulching, afforestation, and enclosure.

The jujube lace bug, Monosteira alticarinata Ghauri is one of the important pests of jujube in South Khorasan province which gained great economic importance in recent years. To study the seasonal population fluctuations of M. alticarinata and its natural enemies, sampling was done weekly from the start to the end of the cropping season during 2020-2021. Jujube leaf was selected as sampling unit. Ten jujube trees were selected, at each sampling time200 leaves (20 leaves from each tree) were collected from different geographical directions and the number of different biological stages of the jujube lace bug as well as its natural enemies were counted using a stereomicroscope. The Pearson correlation coefficient was used to determine the relationship between lace bug density and temperature and relative humidity as variables. The highest population density of egg, nymph, and adult lace bug stages were 394.3±69.09, 114.4±20.5, and 42.4±6.92 on August 15th, September 5th, and August 1st, respectively in 2020 and 434.9±75.31, 126±20.43, and 40±11.50 on August 9th, August 30th, and September 20th, respectively in 2021. In both years, a positive and significant correlation was observed between jujube lace bug total population density (r2020= 0.603, P2020=0.0001 and r2021= 0.475, P2021=0.08) with temperature, however the correlation was negative and non-significant for relative humidity (r2020=-0.265, P2020=0.175 and r2021= -0.349, P2021=0.059). In total, seven ladybird species, one lacewing species, and one parasitic mite species were collected and identified as natural enemies of the jujube lace bug in Birjand. The results of present study can be used in the integrated management of the jujube lace bug.

Astragalus brevidens belongs to the Fabaceae family which has high palatability and a lot of forage production. The aim of present study was to investigate the relationship between production, frequency, density and cover percentage of A. brevidens with the soil physicochemical properties. After the field survey, random-systematic sampling was done in three areas with high, medium and low A. brevidens cover. In each area, 2 transects of 100 meters were considered in the direction of the slope and perpendicular to the direction of the slope, and in each transect, 10 plots (2m2)  were established with a distance of 10 meters from each other and data on frequency, density and cover percentage were recorded. Plant production of aerial parts was estimated via cutting and weighing method. In each transect (beginning, middle and end of each transect), three soil samples were taken from two depths of 0 to 10 and 10 to 30 cm. Once in the laboratory, some soil physical and chemical properties such as texture, bulk density, salinity, acidity, organic carbon percentage, total nitrogen percentage, amount of adsorbable phosphorus and exchangeable cations were measured.  Data were analyzed by One-way analysis of variance and mean comparisons were made by the Tukey test using SPSS18 software. Step by step multiple regression analysis was used to predict the estimation model of A. brevidens measurements with soil properties. The results demonstrated that A. brevidens with canopy cover percentage of 2.53 to 16.65% and dry forrage production of 41.7 to 37.40 gr/m2, grows in sandy clay loam soils with electrical conductivity less than 1.81 dS/m and acidity of 7.82-8.10. Moreover, soil bulk density and clay percentage of soil texture had the most influence on the measurements of A. brevidens (p< o. o5). This species is not s Preparation of soil map of vegetation types of rangelands and investigate the relationship between soil properties and dominant plant species to correctly locate plant species in the rangeland improvement operation is suggested.uitable for use in improvement of rangelands with heavy texture and salty soil.

The distribution of plants in different habitats is influenced by environmental and edaphic conditions. Identifying the relationship between soil factors and vegetation, as well as the specific soil characteristics in which these species are found, is one of the important goals of this research. Taking steps in this direction will help prevent habitat destruction and facilitate the restoration of damaged areas. Let me know if you need any further adjustments!

The study identified three representative areas using the physiognomic-systematic method, focusing on the habitat of Ferula assafoetida L. Areas with less than 15% coverage were classified as low-density, those with 15-30% coverage as medium-density, and areas with more than 30% coverage as high-density. In each representative area, eight transects of 1000 meters were systematically established and positioned perpendicularly to each other. To account for slope variations in sampling, quadrat sampling along the transects was employed. The plot size was determined using the minimum level method, with species density measured in 2 x 2 square meter plots across a total of 240 plots. To prepare soil samples, two soil profiles were dug at a distance of 500 meters along each transect, resulting in a total of 48 profiles from which soil samples were collected at depths of 0 to 30 cm. In each representative area, three transects of 1000 meters were placed perpendicularly, with ten sampling bases spaced 100 meters apart along each transect. The collected samples were transported to the Water and Soil Laboratory of Hormozgan University for analysis. The amount of gum collected from each base was measured using a digital scale with an accuracy of 0.001 grams. A comparison of the production of this plant gum was conducted across the different habitats. The changes in edaphic factors in representative areas were analyzed using SPSS software with the GLM test, revealing low density at 15.8 bases per hectare, medium density at 27.8 bases per hectare, and high density at 46.9 bases per hectare of Ferula assafoetida L.

In the areas with low density, the soil acidity level was measured at 7.4, while in the medium-density area, it was 7.8, and in the high-density area, it reached 8. These results indicate that soil acidity is higher in densely populated areas and lower in areas with low density, suggesting that Ferula assafoetida is more compatible with alkaline soils. As soil acidity increases, the density of this plant decreases. The analysis of density changes in relation to organic matter percentage showed that organic matter has a direct effect on plant density; as organic matter increases, so does the density of the plant. Conversely, when the soil has low organic matter content, the density of Ferula assafoetida declines. Additionally, the comparison of average potassium levels revealed that the low-density area had the lowest potassium content, while the high-density area had the highest. The combined levels of calcium and magnesium were also lowest in the low-density area and highest in the dense Angozeh habitat. Furthermore, the number of Ferula assafoetida bases per unit area increased in regions with higher sand content, whereas the number of bases decreased in clay soils. This plant is not compatible with saline or acidic soils.

Understanding the ecological needs and performance of plant species is essential for implementing remedial activities in dry and desert ecosystems. Bestak city, located in Hormozgan province, is home to numerous Anghuzeh plantations, which have the potential to produce gum, generate currency, and provide significant economic value for local communities. The region is characterized by elevations ranging from 1900 to 2500 meters. This species exhibits a greater geographical distribution in areas with sand, silt, and high acidity, with increased density and decreased distribution in clay-rich areas. According to the findings, it appears that this plant thrives in light soils.

 As a very important and widely used construction material, wood is easily decomposed by biological agents such as bacteria, fungi and termites. However, some wood species are more resistant to these destructive factors, while others are very susceptible to destruction. The aim of this study was to investigate the effective factors on the resistance of the wood of four species of poplar, maple, chinaberry and Cypress against the attacks of the subterranean termite Microcerotermes diversus Silvestri. Since the tropical provinces of Iran, including Khuzestan, are among the regions where different species of termites are considered as the main factors in the destruction of lignocellulosic materials, therefore, knowing resistant woods, which in their natural and untreated state can have high durability compared to the attacks of this insect can help to choose better wood for making wooden products and structures.

 To check the natural durability of the four mentioned species, first, wooden samples were selected and cut from healthy trunks without visible defects. Then, with the aim of collecting termites to conduct selective and non-selective feeding tests, an abandoned palm grove was considered in Dodangeh village, located 20 km from Behbahan city, and then beech wood with dimensions of 2.5 x 4 x 20 cm were planted in the soil as bait for two weeks. After this period of time, the bait sticks were removed from the soil and transferred to the laboratory. Then, the cut wood was subjected to M. diversus termite infestation according to AWPA-EI:06 2008 standard obtained from baits. After the desired period of time, the chemical and physical properties of wood such as the percentage of extractive materials, specific gravity, lignin and cellulose content of each species were calculated according to the standard.

 The results showed that the percentage of extractive substances in maple species has a significant difference compared to other species and is lower than other species, while the highest amount of extractive substances is related to Cypress. Among the investigated species, cypress exhibited the highest lignin content, while poplar displayed the lowest. Notably, both cypress and poplar significantly differed in lignin content compared to the other two species. Cellulose analysis revealed a significantly higher percentage in spruce compared to all other species (p< 0.05). Conversely, no significant differences in cellulose content were observed between the remaining three species. The lowest amount of specific mass belongs to spruce and the highest It belongs to the maple species. This difference is significant at the 95% level. The results of selective, non-selective and field tests of termite feeding on wooden samples are shown in figure number five. The results show that Cypress and chinaberry samples showed the lowest percentage of weight loss and poplar and maple samples showed the highest weight loss.

 What increases the natural durability of wood species against termite attacks and other destructive factors are wood anatomy, wood density, lignin and cellulose content, moisture content, and the composition of extractive materials in the wood. Examining the extractives of the researched species, it can be seen that maple has the lowest percentage of extractives and Cypress has the highest amount, and this problem can have a serious effect on the intensity of termite attacks. Extractive substances play a critical role in enhancing wood's natural resistance to destructive agents, particularly insects. Their significance is evident in certain durable wood species. Removing these extractives renders the wood susceptible to decay. Furthermore, the weight loss observed in both selective and non-selective decay tests, along with field trials, demonstrates a clear correlation with the content of lignin and cellulose in the wood. By increasing the percentage of lignin, the desirability of wood for termites decreases, and on the other hand, with the addition of cellulose percentage, the desirability of the species for termites increases. Lignin is a polymer that, as the second component of wood after cellulose, plays an important role in wood, and due to its phenolic groups, it is considered a toxic substance for destructive agents and has repellent properties. When lignin coats the cell wall, it forms a more impermeable matrix, making the cellulose less accessible and making the wood more resistant to biodegradation. In this research, the highest amount of lignin belongs to Cypress and the lowest amount belongs to poplar, and a significant difference between the amount of lignin in these two species is observed. Physical characteristics such as specific mass is also considered as determining factors of durability against termite attacks, and species with lower and lighter specific mass are more likely to be attacked by termites. According to the obtained results, poplar is different from other species in terms of specific gravity and is considered a lighter species, and this issue, along with the high percentage of cellulose, which is the material preferred by termites, can increase the vulnerability of this species. Based on the obtained results, the effect of factors such as chemical composition and physical characteristics of the studied species on the intensity of subterranean termite attacks M. diversus and according to the mentioned parameters, Cypress species was the most resistant and poplar was the weakest species to the attack of this termite species.

Structure of forest ecosystems undergoes changes in the temporal and spatial scale that this changes cause development. Development process is very slow and takes place in long term in this unites. For evaluation of this changes are used density, canopy and mixing amount. Structural attributes, show the ecological diversity and sustainability of forest ecosystems well. We conducted this study to compare changes in the structural attributes of density and canopy with diversity of tree species between different stories, as well the relationship these variables with diversity indices, between two periods of inventory in fixed location and natural environment where external factors have the least proportion in stand development.

Permanent sample plot with an area of 16 ha is located at 770-920 elevation and Northwest and west directions in 32 compartment, district one Shast Kalateh forest. Inventory was carried out using 100 % sampling method with 1 ha sample plot. Differences from 2003 to 2023 quantitative attributes of density, canopy and biodiversity indices were measured with standard method and compared through ANOVA in different stories.

The density of trees in the investigated plot reduced from 306.31 to 275.44 trees per hectare in 2003 and 2023. Only, Beech (Fagus orientalis Lipsky) species increased in density during this period. The highest frequency of tree individual belonged to under story in 2003, but in 2023, it was transferred to middle story. The average crown coverage percentage reduced from 86% to 70%. The highest amount of canopy percentage assigned to middle and upper stories. The average of Shannon's heterogeneity in 2003 in three story was (1.32, 1.29, 0.72) and in 2023 (0.49, 0.53, 0.58) respectively. The Shannon Wiener diversity index provided a better judgment of the species diversity in the investigated plot than other indices.

The investigated plot is a Mixed beech stand in which Beech shade tolerance species is dominant. Mixing more tree species while increasing diversity at different levels will bring stability of forest ecosystems. The results of this research showed that the indices of species diversity are only one of the methods of interpretation and evaluation of forest ecosystems and other characteristics should also be paid attention to. The periodic monitoring of this indices correctly shows changes trend of forest ecosystem. The results of used indices can be basis of evaluation and comparison with similar forest. Keywords: Structure dynamics, Diversity, Tree strata, Mixed beech stand

From the limitations of detecting the amount of useful life remaining in the components of the structures in the conditions of use with acoustic methods is the impossibility of calculating the modulus of elasticity due to the impossibility of removing the part from the structure. Therefore, most of the classifications during use in the components of structures such as historical buildings are based on measuring the speed of sound. In this research, to calculate the local and global density with the method of pin penetration rate in wooden tie in order to calculate the amount of their remaining useful life by combining stress wave and free longitudinal vibration methods has been studied. There was no significant difference between the values of global sound velocity and global modulus of elasticity with the local results of these factors at the five tested points in each of the wooden tie.

The number of three saturated wooden tie from Iran Railway Company and with the dimensions of 15x25x260 cm, which are made of beech species (Fagus orientalis) and the density was measured by pin penetration method at 5 points of each wooden tie (50 cm distance between each point) and the average results of 5 points were compared with the results of ISO 13910 standard method. The stress wave test was carried out at the same 5 points of density determination by pin penetration rate method to determine the local modulus of elasticity and the results of each point were compared with the global modulus of elasticity of the beam. Longitudinal vibration test was also performed to calculate the damping factor values of the samples.

The results showed that there was no significant difference at the 95% level between the values calculated with both the ISO 13910 standard methods and the pin penetration rate method, and there was a favorable linear correlation between the results of the two methods. According to the results, there was no significant difference between the global sound speed of the beams and their local sound speed in any of the five measured points at the 95% level and there was a linear correlation between the values of the global sound speed and each of the five local points. There was no significant difference at the 95% level between the values of the global modulus of elasticity and the values of the local modulus of elasticity calculated in each of the five points. Also, there was a linear correlation between the values of the global modulus of elasticity and the results of the local modulus of elasticity in each of the five points. There was an exponential correlation between the values obtained from the global modulus of elasticity and the damping factor of each of the wooden tie.

The equality of density according to the ISO 13910 standard method and the nail penetration method, as well as the equality of the modulus of elasticity calculated by the stress wave method and the free longitudinal vibration method, make it possible to obtain all the data required for calculations without removing the part from the structure. The remaining strength of wooden components should be provided according to EN338 standard.

In order to investigate the changes in weed flora in the irrigated wheat fields of Isfahan county over a 15-year period (from 2019 to 2004), a systematic sampling of weeds was conducted in 100 farms with W pattern during wheat tillering to stem elongation stages. In 2004, the dominant weed species was winter wild oat (Avena ludoviciana) with a abundance index of 76.1; however, in 2019 three weed species, including winter wild oat, wild barley (Hordeum spontaneum), and littleseed canarygrass (Phalaris minor) were recognized as the dominant species with abundance indices of 70.1, 42.3, and 28.6, respectively. In 2004, the dominant broadleaf weed species were lambsquarters (Chenopodium album) with a dominance index of 67.9 and prostrate knotweed (Polygonum aviculare) with a dominance index of 31.96. However, in 2019, the highest dominance indices were observed in lambsquarters, prostrate knotweed, and Flixweed (Descurainia Sophia) with abundance indices of 78.4, 38.5, and 39.04, respectively. The correlation between weed distribution and soil factors (nitrogen, phosphorus, potassium, soil texture, and electrical conductivity), crop rotation, and herbicides was examined using canonical correspondence analysis (CCA). Littleseed canarygrass, wild barley, field brome (Bromus commutatus), licorice (Glycyrrhiza glabra), hoary cress (Cardaria draba), and yellow sweet clover (Melilotus officinalis) showed the highest correlation with soil nitrogen levels.

Introduction:

 Wheat (Triticum aestivum) is one of the most important crops in Iran. The area under cultivation of this crop in Fars’s province is 421,000 hectares. Weeds are one of the most significant factors limiting crop production. They primarily decrease grain yield by competing with the crop for light, nutrients, water, and root space.  Weeds can cause a significant reduction in wheat yield, with an average by 23-35%. The most important weed species of wheat in Fars are including Lolium rigidum L., Bromus tectorum L., Mavla neglecta Wallr., Hirschfeldia incana L., Carthamus oxyacanthus M.B., Centaurea solstitialis L., Veronica persica L. The rigid ryegrass (Lolium rigidum) is one of the most troublesome weeds in winter wheat fields of Fars province. Lolium rigidum, has the capacity to produce 45,000 seeds m−2 in infested wheat fields. Its highly competitive nature for nutrients has been reported to cause a significant reduction in wheat yield. The application of herbicides is the most common method of weed control in wheat fields. Herbicides are registered for weed control in winter wheat fields included of Axial®, Topik®, Othello®, Atlantis®, Total®, Bromicide® MA, Geranestar® and Apiros®. There are a limited number of herbicides that is used in wheat. Therefore, it is necessary to register new herbicides in winter wheat. The objectives of this research were to optimize the dosage of FenoMetri in combination with a non-ionic surfactant, Tifis®, and to compare its efficacy with other pre-mixed herbicides (Bromicide® MA, Othello®, and Atlantis®).

 In order to study the efficacy of herbicides for controlling weeds in wheat fields, an experiment was conducted at the Fars Province Agricultural and Natural Resources Research and Education Center, Darab, Iran, during 2021-2022. This experiment was carried out using a randomized complete block design with 14 treatments and 4 replications. The treatments included post emergence application of Bromicide MA® at 1.5 L ha–1 + Topik® at 1 L ha–1, Bromicide MA® at 1.5 L ha–1 +Puma-super® at 1 L ha–1, Granstar® at 20 g ha–1 +Topik® at 1 L ha–1, Atlantis® at 1.5 L ha–1, Othello® at 1.6 L ha–1, Tifis® at 300 g ha–1, FenoMetri  at 0.8, 1 and 1.2 L ha–1 with and without surfactant at 1 L ha–1, Sencor® 800 g ha–1 (400 g ha–1 in the 1- 3 leaf stage + 400 g ha–1 in the tillering stage of wheat and Control (hand weeding). Each plot was divided into two subplots. One subplot was treated with the herbicide applications, while the other subplot was left unsprayed to consider as a weedy check treatment for comparison purposes. Herbicide treatments were applied in tillering stage of wheat (Zadoks’ scale = 25) using a pressure backpack sprayer equipped with an 8002 flat fan nozzle tip, which delivered 350 L ha-1 at 2 bar spray pressure. Traits were recorded including weed density, weed biomass, plant height, grains per spike, number spikes, 1000 grains weigh, grain yield and biological yield. Weed density and dry weight were determined in random 0.50-m2 quadrates per plot. The grain yield and biological yield were recorded for a 3 m2 and 0.50 m2 from each plot, respectively. Weed control efficiency (WCE) representing the degree of reduction in the density or dry biomass of weeds due to herbicide treatment was determined using Equation 1. A and B are the density or dry biomass of weeds in the unsprayed and sprayed subplots, respectively (Somani, 1992). The changes in each trait of yield wheat (Yi), as mentioned above, were determined using Equation 2 Ys and Yu are the amount of each trait in the sprayed and unsprayed subplots (weedy check treatment), respectively. After checking data normality, the data were subjected to analysis of variance using SAS 9.2 software. To compare the means, the Fisher's Least Significant Difference (LSD) test was used at the 5% level of significance.

 Weeds infestations included Lolium rigidum L., Convolvulus arvensis L., Melilotus officinalis (L.) Lam and Carthamus oxyacanthus M.B. The highest and lowest density were observed for L. rigidum (56%) and C. oxyacanthus (5.1%), respectively. While, the highest and lowest weight were observed for L. rigidum (74%) and C. oxyacanthus (4%), respectively. The statistical analysis of the data on the weed density and biomass were revealed that applied herbicides significantly decreased both weed density and biomass. Additionally, the herbicide treatments led to a significant increase in the number of spikes per m², grains per spike, 1000 grains weight, grain yield, and biological yield. The Bromicide MA® had the best treatment for controlling the broad-leaved weed by 80 – 85%, On the other hand, Sencor had the best control for ryegrass (L. rigidum) by 80%. The application of FenoMetri at 1.2 L ha–1 with Surfactant® decreased the biomass of C. arvensis, C. oxyacanthus, M. officinalis, L. rigidum and total weed by 71, 63, 52, 48 and 73% respectively. It also increased grain and biological yields up to 20% and 22% as compared to the weedy check treatment. Additionally, the herbicides of Sencor® and Othello® showed the highest- grain yield after hand weeding, respectively.

 The application of FenoMetri at 1.2 L ha–1 with surfactant effectively controlled the density of weed species by 45–71% and the dry biomass of weed species by 48–72%. It also increased grain and biological yields by up to 20% and 22%, respectively, compared to the weedy check treatment. However, the efficacy of FenoMetri herbicide in controlling weeds was lower compared to commonly used herbicides such as Othello®, Bromicide MA® + Topik®, and Bromicide MA® + Puma super®. Therefore, it is recommended to evaluate the FenoMetri herbicide with higher application rates.
 

Agricultural residues and wastes are the main source of biomass for use in bioenergy production and animal and poultry feed production industries. These biomasses in their original form have a large volume and low energy (per unit volume) and require a lot of space and extensive movement. Therefore, one of the methods of optimal use of these biomasses is to transform them into pellets, which have more mass and energy per unit volume and enable their easier use and transportation. Currently, biomass has the fourth place in energy supply after oil, natural gas and coal and provides approximately 14% of the world's energy needs. The use of biomass, especially in European Union countries, as an attractive source for replacing fossil fuels is developing and expanding. The use of biomass as fuel has significantly reduced the amount of environmental pollutants, so that the amount of CO2 absorbed from the atmosphere during biomass growth is similar to the amount produced during combustion, followed by a net cycle of production.

 The raw materials for making pellets were prepared from spruce wood sawdust (collected from a sawmill in Sari) as well as corn stalk and soybean residues in the fields of Dasht Naz in Sari. The desired materials were transferred to the laboratory in the necessary amount and kept at ambient temperature until the experiments. The samples were first crushed into 20 mm sizes and then powdered using a grain mill (Mehr Tehiz company, Iran) and passed through 18 mesh sieves in the range of 1 mm to make pellets. A palletization mechanism was used to compress the pellet. This system was designed and built in biosystem mechanics of Sari University of Agricultural Sciences and Natural Resources. The material was placed inside a steel mold with a cylinder inner diameter of 8.05 mm and a height of 150 mm with a blocked end. A piston with a diameter of 8 mm connected to the driving arm of the tension-compression test machine was used to compress the material. Loading by a piston with a quasi-static speed of 5 mm per minute is compressed to a pressure of 1300 N.

In this research, the mechanical and thermal properties of pellets made from the combination of spruce sawdust and corn and soybean residues were evaluated. In the present study, the effect of four combinations of agricultural and forest materials at two moisture levels (12% and 18% based on fresh weight) on the indices of density, compressibility, Hausner ratio, strength and calorific value of the produced pellets were investigated and evaluated. it placed. The results showed that the pellet density at 18% humidity was lower than the density at 12% humidity. The highest density related to the combination of 60% spruce wood sawdust-40% corn stalks was obtained with a value of about 149 kg/m3 and the lowest value related to 100% soybean stalks was about 110 kg/m3. Also, the ratio of Hanser and CI in the combined pellets that have a higher percentage of sawdust and also in the combination of sawdust with corn stalks are within the permissible range. The highest pellet strength was 23.8 N/cm corresponding to 100% sawdust at 18% humidity and the lowest was 15.4 N/cm corresponding to 100% soybean stalk at 12% humidity. The calorific value of the pellets is in the range of 14.37 to 18.52 MJ/kg, which is the minimum value for the pellet made from 100% soybean stalk at 18% humidity and the maximum value for the pellet made from 100% fir wood sawdust and It was obtained at a humidity of 12%. Therefore, the use of agricultural wastes and their proper combination is a good option for the production of biofuels due to their density and strength.

 The type of biological waste and moisture percentage affect the physical and mechanical properties of the produced pellets. In general, the combination of spruce wood sawdust with corn stalks and soybean improved the mechanical and thermal properties of the pellet. Hanser's ratio and compressibility in the combined pellets that have a higher percentage of sawdust and also in the combination of sawdust with corn stalks are within the standard range. Also, in the compositions that have a higher proportion of spruce wood sawdust and lower moisture, the density and strength factors of the pellet increase. The highest and lowest calorific values were obtained in a higher ratio of sawdust and a higher ratio of corn, respectively. Therefore, it is possible to make pellets from the waste of garden and agricultural products that have good density and strength and high calorific value.

Rice (Oryza sativa) is a major cereal crop and staple food for more than half of the world's population. About 90% of the world's rice is produced and consumed in Asia. Iran is one of the arid and semi-arid regions and due to the lack of water in many parts of the country, the area under rice cultivation decreases. Direct rice cultivation is a good way to save water. The most important challenge in this cultivation system is weed control. The traditional methods of weed control in rice include hand-weeding by hoe or hand pulling, but this is becoming less common because of labour scarcity at critical time of weeding and increasing labour costs. Herbicides play a key role in weed control and are used extensively today. Therefore, this experiment was conducted to evaluate the effectiveness of different weed management practices for direct seeded rice at varying row spacing. This study was conducted to investigate the effect of planting distance on rows and herbicides on weed suppression and direct rice cultivation performance in the research farm of Sari Agricultural Sciences and Natural Resources University as a factorial experiment in a randomized complete block design with three replications in 2019. Distance between plants at two levels of 3 and 5 cm and chemical management of weeds in five levels of weed-free (control), weed-infested (control), application of trifamone + ethoxysulfuron herbicide 30% (council active) at the rate of 150 g ha-1 in stage of 2 up to 6 leaves of weeds, application of bisopiribac sodium herbicide OF10% (nomini) at the rate of 250 ml ha-1 in stage of 2 to 6 leaves of weeds and application of a mixture of two herbicides halofop butyl OD 20% with 2.5 liters ha-1 with basagran (bentazone) were 3 liters ha-1 in the 2 to 6 leaves stage of the weeds. Results showed that although planting row spacing had no effect on the desired traits; however, weed management had a significant effect on the studied traits. Visual evaluation of weed damage in two evaluation stages (15 and 30 days after spraying) showed that among the chemical control treatments, trifamone + ethoxysulfuron herbicide was superior to other herbicides with 75 and 83.33% weed control, respectively. The lowest weeds biomass was observed in 6 weeks after spraying (20.50 g m-2) and 10 weeks after spraying (20.83 g m-2) in trifamone + ethoxysulfuron herbicide treatment, which was not significantly different with weed free (control). The highest height of rice plants (103.17 and 98.41 cm) was observed in the complete weed control and trifamone + ethoxy-sulfurone herbicide treatments, respectively. It is worth mentioning that the maximum biological yield of rice (6244.4 and 5808.4 kg ha-1) and grain yield (2391.218 and 2290.27 kg ha-1, respectively) was observed in weed-free (control) and application of triafamone + ethoxysulfuron herbicide. According to the results of this experiment, the use of trifamone + ethoxysulfuron herbicide at the rate of 150 g ha-1 is recommended for proper control of weeds in direct rice cultivation. The highest and lowest height, number of tillers and spike length were observed in weed-free control treatment and weed-infected control treatment. Among the herbicides used in this experiment, in the treatment of triafamone + ethoxysulfuron with better weed control, In plant height, tiller number, spike length and number of seeds per spike were superior to other herbicides. According to the results of the experiment, the application of the herbicide triafamone + ethoxysulfuron, while better control of weeds, can increase grain yield.

It seems that there is a mutual relationship between the classes of rangeland conditions and the characteristics of vegetation and biodiversity. However, there is relatively little and contradictory information in this regard. This research was conducted to compare the percentage of cover, litter, density, production, and numerical indicators of biodiversity among 11 types of plants in the Darmian-Sarabisheh protected area. 

After the field survey and identification of plant types, 11 plant types could be identified in the entire area. Sampling was done by the random-systematic method. For this purpose, three key areas were selected for each plant type, three transects were established in each key area, and 20 plots of 4 square meters were sampled in each transect. In each plot, the percentage of vegetation cover, litter, density, and production was measured. Canopy cover and litter percentage were determined visually. Plant density was calculated by counting plants per unit area. Production was estimated through cover vegetation by double sampling. The Adelaide method was used to estimate shrub production. The range condition was evaluated by the modified four-factor method. Species diversity components, including species richness, evenness, and dominance, were calculated by numerical indices. Also, species abundance distribution models (broken-stick, log-normal, log series, and geometric series) were applied to evaluate plant diversity graphically. The chi-square goodness-of-fit test was used to determine the most accurate fit of species distribution to each statistical model. To compare vegetation characteristics and species diversity components among the 11 studied plant types, one-way analysis of variance (ANOVA) and Duncan's multiple range tests were conducted.  

The results of the analysis of variance showed that between the 11 plant types studied in terms of vegetation characteristics, including the percentage of vegetation cover, litter, plant density, and production, and numerical indices related to species diversity, including species richness, evenness, and dominance, there is a significant difference at the p≤0.01. The mean comparison results showed that the highest vegetation cover percentage belongs to Artemisia aucheri - Stipa barbata (51.23%) in good condition. Acantholimon scorpinus - Cousinia eryngioides and Eryngium bungei- Cousinia eryngioides (46.27% and 40.44%, respectively) in poor condition are in the next. The highest plant density belongs to Artemisia aucheri - Stipa barbata (157 individuals) in good condition, followed by Eryngium bungei- Lactuca orientalis (126 individuals) in poor condition. Astragalus verus- Artemisia aucheri in good condition and Acantholimon scorpinus - Cousinia eryngioides in poor condition have higher species diversity (H¢=2.51 and 2.48, respectively). The species abundance of Eryngium bungei- Cousinia eryngioides and Eryngium bungei- Lactuca orientalis types (in poor condition) follows the log-normal series, which represents stable communities. Also, Astragalus verus- Artemisia aucheri and Artemisia aucheri- Stipa barbata, which are in good condition, follow the log series and the geometric series, which represent unstable and fragile communities. 

Range condition was independent of vegetation cover, production, density, species richness, diversity, evenness, and dominance. Some vegetation types are in poor condition despite high vegetation cover, density, and production. The present study also showed that high species diversity is observed even in the poor-condition class of vegetation types and does not necessarily indicate rangeland stability. Determining ecosystem stability and biodiversity based on species abundance distributions (SADs) is also impossible.

In order to evaluate yield and yield components in intercropping barley with vetch, a two-year field experiment was conducted at the Agricultural and Natural Resources Research Station of Miandoab. The arrangement consisted of 9 mixing treatments with densities of 200 Vetch plant + 300 Barley plant, 200 Vetch plant + 500 Barley plant, 200 Vetch plant + 700 Barley plant, 400 Vetch plant + 300 Barley plant, 400 Vetch plant + 500 Barley plant, 400 Vetch plant + 700 Barley plant, 600 Vetch plant + 300 Barley plant, 600 Vetch plant + 500 Barley and 600 Vetch plant + 700 Barley plant per square meter and sole culture of both crops. The experimental design was a randomized complete block design with four replications. The result showed The highest spikes per square meter, thousand kernel weight, biological yield, and grain yield in barley were observed in the sole culture of barley. Also, the highest plant height, number of seeds per plant, thousand kernel weight, biological yield, and grain yield in vetch belonged to the sole culture of vetch. However, the highest Land equivalent ratio (LER) belonged to treatments of 200 Vetch plants + 500 Barley plants by 1.49,

The study is Considering the importance of the role of benthic communities in evaluating the ecological status of aquatic ecosystems and part of a research project in the southern coasts of the Caspian Sea (depths less of 30 meters) was conducted in 2019. The aim of this study was investigation of the distribution, density and biomass of macrobenthos organisms in the water at a depths of 5, 10 and 30 meters south Caspian Sea. Sampling was seasonaly at eight with using Van Veen Grab. Overall 34443 organisms of Polychaeta including 3 families, 4 genuses and 4 species. The results showed that the highest density at Sefidrood station with mean of 327±27.71 N/m2 and lowest was at Bandartoraman station with mean 77±5.33 N/m2. The highest of Polychaeta was in summer and depth 30 meters with mean 285±26.18 N/m2 and lowest density in spring and depth 10 meters with mean 38±10.81 N/m2. The highest biomass was in spring and depth 30 meters with mean 0.23±0.02 g/m2. The highest species was assigned to S. gynobranchiata with mean 352±19.74 N/m2 and frequency 80%. In general, the results showed that in most seasons of the year, S. gynobranchiata was the dominant Polychaeta species.

The beech tree has the ability to produce shoots and form a coppice stands under specific natural climatic and environmental conditions or under unusual circumstances caused by human interference. The current research aims to compare the structural characteristics of coppice and standard stands of beech in the Hyrcanian forests in the Chetan area in Nowshahr. The diameter at breast height of all trees was measured using the full calipering method to determine the stocking volume. Half-hectare sample plots were established using the distance-azimuth method to study the spatial structure. The standing and log stocking volumes were also determined. According to the results, the number of live and dead trees in the coppice stand was 174 and 9.7 per hectare, respectively, and their volume was 146.2 and 3.6 m³/ha, respectively. In the standard stand, the number of live and dead beech individuals was 145 and 11 per hectare, respectively, while their volume was 147.5 and 12.1 m³/ha, respectively. About 55% of the standing dead trees in the coppice stand and 35% of the standing dead trees and 42% of the fallen dead trees in the standard stand were primarily in the first decay degree. The highest number of individuals in a beech coppice group included four, which is 17%. Groups of five individuals and two individuals also accounted for 16.9% and 16.5%, respectively. Spatial structure indices of beech coppice, including the Pielou segregation, Clark and Evans, Mingling, DBH differentiation, DBH dominance, and uniform angle, indicate species continuity, clustering, severe dominance of beech species, moderate differences, small size dominance, and clump distribution, respectively. Traditional uses of forests have influenced the structural characteristics of beech stands. Therefore, it is suggested that these and other similar stands be protected as a forest reserve to ensure the development of these habitats towards a more favorable state and the stability of the landscape in these areas.