جستجوی مقالات مرتبط با کلیدواژه « قرق » در نشریات گروه « محیط زیست »

Each of the different exploitation and management methods in rangelands have different effects on the rangeland ecosystem functions. Incorrect and inappropriate ways of rangeland use, especially in the last few decades, have caused severe damage to natural resources. There is a few research on the effects of grazing on sand habitats of desert areas. The aim of the current research is to investigate the effect of different methods of rangeland utilization on ecological characteristics, including the percentage of vegetation cover, plant density, species richness, diversity, evenness and dominance, and species similarity in the studied rangelands.

This research was conducted in the outskirt, seminomadic, settled nomadic and enclosure in Zirkouh, South Khorasan province. In each rangeland, the list of plant species, density and vegetation cover of each species was determined separately. Also, the range condition was evaluated by the modified four-factors method. In addition to numerical indices, the ranking of species diversity was investigated using the Renyi diversity ordering curve. In order to check the species similarity between the four studied rangelands, Jaccard's similarity index was used, and hierarchical cluster analysis (Euclidean distance and Ward's method) was used to better display the species similarity. Finally, the relationship between vegetation cover and the number of species and biodiversity indices was tested by Pearson's correlation coefficient.

Based on the modified four factors method, the condition of outskirt and seminomadic rangelands were moderate and settled nomadic rangeland was poor and enclosure rangeland, has been evaluated as good. The results of ANOVA showed that the effect of grazing methods on the vegetation cover (at the 0.05 level) and the total and average species richness (at the 0.01 level) were significant. Enclosure rangeland had the highest plant cover percentage and plant density (54.73% and 80, respectively) and the settled nomadic rangeland had the lowest plant cover percentage and plant density (15% and 5, respectively). The highest species richness belonged to enclosure rangeland and there was no difference between other rangelands. Compared to other rangelands, the seminomadic rangeland had the highest proportion of native plants and the lowest proportion of increaser plants in the plant composition of total richness. The highest proportion of increaser plants was observed in settled nomadic rangelands. In terms of species diversity, enclosure rangeland had the highest Shannon-Wiener diversity index (2.03) and Simpson diversity index (0.80) compared to other rangelands. The results of the correlation coefficients of vegetation cover and the number of species and species diversity indices showed that, in general, there is a significant positive correlation between the diversity indices and vegetation cover and the number of species. In addition, there is a significant negative correlation between the species evenness and dominance indices, as well as vegetation cover and the number of species. The results of the Jaccuard similarity index show that the highest degree of species similarity is observed between the outskirt and the settled nomadic rangelands (62%).

The results showed that the overgrazing around the livestock pen in the settled nomadic rangeland is clearly visible and it has led to a significant decrease in vegetation cover, plant density and species diversity. Resting in rangelands (in the enclosure) and delaying grazing (in seminomadic rangeland) can also enhance vegetation and biodiversity. In terms of the percentage of vegetation cover, density and plant composition, the seminomadic rangeland is located next to the enclosure. The most proportion of forage species was observed in the plant composition of the seminomadic rangeland. If we accept the hypothesis that range enclosure causes the plant succession towards the climax stage and in range management, the sub-climax stage is always better than the climax stage, in this case, in terms of livestock and range management, the temporary settlement of nomads will be more beneficial than range enclosure.

Studying the effects of different types of water and soil protection systems on soil properties is of great importance in soil planning and management and is considered as a move towards sustainable development. The purpose of this study was to investigate the effect of three systems of water and soil protection in Chaharmahal and Bakhtiari province on topsoil and subssoil of soil organic carbon content, bulk density, soil stability, nitrogen, potassium, phosphorus, soil texture, acidity, electrical conductivity and soil permeability at depth of 0-30 and 30-60 cm. By comparing each of the soil physical and chemical properties in exclosure, contour furrow and Pitt seeding and the control areas, it was concluded that in soil and water conservation systems, organic carbon, bulk density, stability, Phosphorus, soil texture, acidity, electrical conductivity of topsoil did not increase significantly and in some cases nitrogen and potassium increased significantly (at the level of 5%). The lowest amount of surface soil nitrogen (0.087%) was observed in excavation improvement operation which had a significant difference with surface soil nitrogen (0.072%) in contour operation. The lowest and highest amount of surface soil organic carbon with significant differences (1.02 and 1.43%) were related to pitt seeding and contour farrow, respectively. Comparison of permeability data in control and protected areas showed that the implementation of water and soil protection operations had a positive effect on soil permeability. In general, the effect of water and soil protection systems on improving soil quality is not absolute and depends entirely on different climatic conditions, geology of each region.

Grazing as one of ecological disturbances causes changes in soil characteristics of rangelands. This study was carried out to study the effect of Grazed pasture on plant cover, microbial deposits and some soil characteristics of Gonbad in Hamedan.

Five transects of 1000 meters were considered separately for soil characteristics in each region (grazed and ungrazed). Systematic sampling of soil was performed every 100 meters in May 2016. The elements of Cu, Fe, K, Mg, Mn and Zn were measured by atomic absorption spectrometer, acidity with pH meter, bulk density from clavicle method, total nitrogen from Kjeldahl method, organic carbon and soil organic matter by the oxidation method of Walkybak and Zeitous Carbon microbial was calculated by quenching-extraction method.

After analyzing, it was determined that the concentrations of K and Zn in the soil of the sample area and the concentration of Mg in the soil of the control area increased significantly at 5% level. Soil acidity in the control area increased from 7/1 in the sample area to 7/23. Soil moisture content decreased significantly in the control area and from 27.11% in the sample area reached 18.12%. Soil bulk density in the control area was 1.16 g / cm3, which decreased significantly in the sample area and reached 0.98 g / g / cm3. The carbon microbial biomass was significantly differed in the soil of grazed and control areas. The comparison of the mean microbial carbon content in studied rangelands showed that this parameter ranged from 0.83 g / kg in the control area (grazed) to 0.95 g / kg and increased significantly.

 The exclosure area has been enclosed with exclosure, soil characteristics in the path of sequencing and achieving ideal conditions, but it still needs attention and continued conservation.

The purpose of this study was to evaluate the impact of the enclosure on the quality of gonbad rangelands using density, diversity and species richness indices.. vegetation sampling was done based on systematic random sampling. Five transects of 1000 meters were considered separately for vegetation characteristics in each region. The species density was calculated by counting the number of bases in the plot, the species diversity was calculated by the Shannon-Wiener diversity index and species richness counting the number of species in each plot. After analyzing, it was determined that the enclosure has a significant effect on species density, species diversity and species richness. Generally, palatability plants and diversity and richness of the species were significantly increased in the protected area. Species diversity in the grazed area increased from 1/798 in the protected area to 2/236. There was a significant decrease in the amount of species richness in the affected area, and from 11.626 species per square meter in the protected area, it reached 9.253 species per square meter. The results indicate that the specimen area has been enclosed with enclosure, vegetation characteristics in the path of sequencing and achieving ideal conditions, but it still needs attention and continued

Our dependence on plants for survival is so strong that its exploitation and management are special sciences. One of the key rangeland species is Agropyron trichophorum. Awareness of its ecological information is of particular importance. The aim of this study was to determine the seasonal changes in production and consumption of Agropyron trichophorum in summer rangelands of Lorestan province.

In this study, production inside the enclosed part and consumption outside it (control), from 2007 to 2010 were investigated. Each year, 50 average rootstocks of the species were identified at the beginning of the growing season and 5 medium rootstocks were selected at the beginning of the season for each month of the grazing season inside the enclosed plot and 5 similar rootstocks outside the grazing area and cut and weighed in each month of the grazing season. Data were analyzed in MSTATC software and the mean was compared with Duncan's multiple range tests.

The difference between the mean effects of year, month and the interaction of year, months are statistically significant (P <0.01). The difference in production in different years was large, so that the forage produced in the year of low production was about 42% of the forage produced in the year of high production. On average, about 80% of the production of this species was used by livestock during the grazing season, which fluctuated between 75% and 87% in the study years.

Production in June, which is the result of plant metabolism in the second half of May and the first half of June, is higher and decreases in July and August. In total, this species produces an average of 149.4 kg / ha of forage, of which 119.8 kg / ha (80.2%) is consumed. In July and August, the pressure of grazing was transferred to the back of the fields; this is due to the presence of forage in the lands near the village, as well as increasing the temperature and reducing water resources in the rangeland.

Identifying indicator species facilitate predicting ecological characteristics of arid and semi-arid ecosystems and help managers to introduce appropriate plant species for rangeland restoration. This study focused on indicator species related to four different utilization methods including, exclosure, rangeland, abandoned area and agriculture area in rangelands of Mahoor Mamasani in Fars province. Vegetation and soil seed bank were sampled in 1 m2 quadrates systematically located on transects. Soils were sampled from 0-5 and 5-10 cm depths. Then seed bank composition was identified after seed germination in glasshouse. In order to identify indicator species and examine changes in characteristics of vegetation and soil seed bank, we used indicator species analysis (ISA). The result on indicator species analysis showed that in exclosure there were 24 and 3 indicator species in vegetation and seed bank, respectively. These were 4 and 3 indicator species for rangeland area, 11 and 2 indicator species for abandoned area and 13 and 3 indicator species for agriculture area. As some vegetation and soil seed bank indices damaged under overgrazing and land use change it is recommended to make some changes in current rangeland management and utilization in order to restore vegetation.

Introduction Climate change is one of the most important challenges in sustainable development, which has a negative impact on aquatic and terrestrial ecosystems. This will change rainfall patterns the power to increase hurricane and the risk of drought, flood and will strengthen pressure on water resources. Researchers generally agree that the main cause of the increase in global temperature is carbon dioxide. So in order to reduce atmospheric carbon dioxide and greenhouse gas balance of content, in the form of numerous atmospheric carbon capture and should be sequestration. Rangelands us good options for research on carbon sequestration projects, because on the one hand, many pastures Iran located in the arid and semiarid region that encompasses an area of about 90 million hectares. Due to the pasture species on carbon sequestration, several studies within and outside the country have been conducted. to investigate the carbon sequestration potential shrub species dominate (Helianthemum lippii, Dendrostellera lessertii and Artemisia sieberi) in arid rangelands Grbaygan FASA, showed that the ability of the three species differ in carbon sequestration and Artemisia sieberi plant was highest. Effect of different vegetation types on carbon sequestration in grasslands Miankaleh showed that the rate of carbon sequestration in plants and different species And with increasing levels of woody cover and percentage increases. Increase the electrical conductivity of the soil in sand sagebrush species like the atmosphere, reducing the amount of precipitation, but has an adverse effect on the species of wild pomegranate. In the review of rangeland carbon sequestration in North America, it was concluded that the relationship between carbon sequestration and the percentage of annual plants in pastures grazed negative. Mills rangeland carbon sequestration potential in two different species of Artemisia sieberi and Stipa barbata in management were assessed. According to the results, the percentages cover of plant species in the area because of the most plain and at the lowest long-term protection. The highest rate of carbon sequestration in the area because it was so S.barbata. In recent years the role of pastures as a basis for reducing atmospheric carbon dioxide and carbon sequestration are given more importance. But so far, many studies on the effects of grazing management on carbon sequestration is taken. This study evaluated the effects of grazing and enclosure management on carbon sequestration potential species (Astragalus peristerus) as one of the dominant species in Fasham rangelands. Material & Methods Material Study area at a distance of approximately 24km from the city Shemiran and the North East of Tehran is made. The study area has a 314 /5 ha area.159 acres it to preserve plant and animal species, enclosure the surface contains 155/5 hectares that are grazing in the face. Such a wide geographic region between longitudes51° 29¢to 51 ˚ 36¢and35˚ 55¢ to35˚ 58¢ is located. Based on data recorded rainfall, average rainfall will see website Fasham station as the station 696/ 2mm, mean maximum and mean minimum annual rainfall is in 1321 and 248/5 mm. The average annual temperature in 15/2C° and the average warmest and coldest months of the year July and January, respectively, with 28/4 and 1/7C° have been. The absolute maximum and minimum recorded temperatures such as those belonging to two months, and 39 /8 and -11/4 C° is. Prevailing wind direction in the area southwest of the annual average wind speed of most is 6/3 Nat. The strongest wind direction and speed this year average West is 47 nots. General area of bare soil or soil with very low stone, gravel depth of medium to heavy texture on the floor with FAO classification Lithicand Eutric Leptosols or Calcaric Regosols are classified. Soil acidity this is the area between 7/2-7/5. Methods After preliminary identification and delimitation of the study area, in order to study the vegetation variables, stochastic methods - systematic methods. That each of the treatments (enclosure and under grazing) two transect length of 100 meters (a transect perpendicular to the direction of the slope and a transect slope) along each transect, 10 plots of one square meter (based on plant distribution pattern) was established. To determine canopy cover and dominant species, the existing plant lists and percentage of vegetation cover within each plot was determined to be separate species. For estimating above-ground biomass of crops including direct measurement method (cutting and weighing) were used. Underground biomass estimate of the root: shoot ratio was used. To this end, 10 of these were selected by digging the soil to a depth of root penetration root biomass was harvested. Then having a total weight of plant biomass (above ground biomass + underground biomass) mass ratio biomass underground aerial biomass was determined by applying the ratio of the weight of the aerial biomass, the weight of the underground biomass were estimated land area. aerial and ground to determine the conversion coefficient of carbon to organic carbon, the combustion method was used. Therefore, the plant samples were dried in the oven thoroughly grinding of any third sample was prepared from 5 g. Both were estimated land areas. Then the samples were weighed and the electric oven temperature to 550 C° was 5 hours. Samples (organic material or ash) after leaving electric oven and cool were weighted by the desiccator. Then the amount of organic carbon (g) of each plant organ separately calculated. Thus, the total weight of carbon sequestration was to (g m). This study was conducted in a completely randomized block design. The data normality by the Kolmogorov-Smirnov and homogeneous variances were analyzed by test Leven. To compare plant biomass weight, feed conversion and plant carbon sequestration in enclosure and area under grazing-Test was used totes it. SPSS16 software for statistical computing and graph drawing was done in Excel 2010. Discussion of Results&Conclusions Biomass weight The mean weight of aboveground and underground biomass of the species listed in the area of protection and because there is a significant difference (P < 0.01), but the biomass of plant species in the area, there is no significant difference. coefficient of biomass Conversion coefficient of biomass to organic carbon by comparing aerial and ground feed in the pasture enclosure and grazed A.peristerus determined no significant differences between feed There are two areas of the body (P<0.05). Carbon Sequestration Aerial biomass carbon sequestration and biomass of plant species in the area grazed and ungrazed A.peristerus no significant difference. But biomass carbon sequestration underground, cant difference was significant (P<0.05). Carbon distribution Both grazed and enclosure grassland carbon underground organs over shoots. Grassland ecosystem carbon levels are the best tools for effective management: grazing intensity and frequency of grazing through the system why are applied. More biomass of plant species in grazed A.Peristerus greater amount allocated to is.Compared to carbon convert coefficient of the two treatments grazed and enclosure A.peristerus grazing doesn’t represent cant difference in the two regions. Maybe animal grazing don’t have a large influence on the ability to store carbon is. Conversion coefficient of carbon in underground organs to above ground because of the higher wood moisture content less is more. Increase carbon sequestration from biomass grazed A.peristerus is underground. Among these are perennial plants that which is grazing the normal range increases the underground biomass of this species is the result of increasing carbon sequestration. Perhaps the greatest effect because the carbon dynamics because of the effect on the composition of plant communities. Grazing encourage the species of grasses and annual Forb which is the root cause of the fiber density, not down can contribute to carbon sequestration. The distribution of carbon in A.peristerus biomass underground was more than aerial biomass. Biomass carbon content below about 10% of the total carbon in biomass and its turnover is very slow performing (every 7 years). Thus, short-term disturbances above ground biomass can not only because of the great variation of soil organic carbon is stored. A large amount of organic matter inputs to soils of grazing land is the organ part underlying soil (e.g. root). As a result, the upper land disturbances such as grazing, fire, etc. on the bottom of the soil organic matter is indirectly. Can be said in general, pasture management is multi-faceted. Achieved if biomass is increased with moderate grazing, due to larger amounts of organic matter to the soil system will enhance the total carbon in pasture. There sult is making moderate grazing capacity of rangeland management is the best option to accompany taking advantage of the natural benefits of carbon storage and sequestration and them Itigation of global warming shall be. It is worth noting that in terms of soil and vegetation in enclosure pastures are stall condition, cand eploy and protectthe soiland be effective to taken later in the pasture ready to be principled.

Pastures cover about 50% of earth area and contain one third of world’s carbon reservoirs. Consequently, these lands have enough capability to prepare carbon sequestration. This research is aimed to determine amount of carbon sequestration in Psathyrostachys fragilis pasture type and also compare it in its two form of enclosure and grazing areas. For this reason, after initial definition and determination of limits under survey, random-systematic sampling has been used to study the vegetation covering. Then, the biomass of vegetation and the amount of organic carbon existing in different organs of plants were determined. Finally, carbon sequestration was determined the weight and organic carbon content of overland and underground biomass. The non-coupling t-test was used in order to compare the carbon sequestration and the weight of vegetation biomass between two ways of enclosure and grazing. The results showed that there is one percent difference between the average biomass weights of overland and underground in two enclosures and grazed regions. In the grazed area this difference was more than enclosure region. There was no significant deference (P<0.05) between the replacement coefficients in two enclosure and grazing regions. Also between amount of carbon sequestration in overland, underground and vegetation biomass of P.fragilis type in two grazed and enclosure areas, there is no any important differences and in both enclosure (P<0.05) and grazed pastures amount of carbon in underground organs is more than overland organs. Generally, carbon sequestration in grazed areas is more than in enclosure regions which is due to the lighter grazing.

Rangelands are containing more than one-third of earth's biosphere carbon stocks that can able to absorb atmosphere carbon dioxide by their vegetation and accumulate in plant tissues and soil. Animal grazing as a human factor could be effect on the amount of absorption. In this study, the effect of grazing on carbon sequestration is studied in grazed and ungrazed winter rangelands of Sorkhkola in Sari. After determining the type of vegetation and dominant species (Hordeum glaucum), sampling was done by randomly-systematic method and 20 plots (1m2). The plant biomass of shoot and root was determined by direct measurement. Then, samples were weighed and dry matter was calculated for each organs. The soil sampling was done from each horizon (0-15 and 15-30 cm) based on boundary separation of the surface and underlying horizon in the area. Organic carbon percentage of plant and soil samples was obtained in laboratory. As well as other soil properties including bulk density, soil texture, calcium carbonate, electrical conductivity and soil reaction was determined. Finally, the grazed and ungrazed area data was analyzed using independent t-test in SPSS 16 software. The results showed that a significant reduction of carbon sequestration from aerial to underground organs area in grazed and protected sites (p≤0/01). Despite the decline in soil carbon sequestration through grazing to protected area had no significant differences between the first and second soil depth. Also, the result showed that sequestration rate was much higher in the soil to plant. It was 97% and 99% of the carbon sequestration in the protected and grazed area respectively.

The conversion of natural ecosystems into artificial or man-made ecosystems due to land use change can alter both ecosystem structure and function. The soil seed bank contains a source of viable and germinable seeds which can germinate under suitable environmental conditions. This can produce a new population or renew the present plant community. Information about the soil seed bank for Iranian flora is scarce and this study aimed to study the soil seed bank in rangeland which has been excluded from livestock grazing and the nearby area with a history of rangeland conversion into arable lands. We measured the seed bank in soils taken from two depths (0-5 and 5-10 cm) and how soil seed diversity and richness changes with land use changes. The results of this study showed that land use change significantly influenced soil seed bank diversity, species richness indices and functional group. The exclosure area showed the highest species richness, diversity and functional group while these indices significantly declined as rangeland became converted into arable lands. However, the abandoned area did not show significant differences from other two sites. Moreover, some functional groups such as annuals, therophytes, Gramineae and forb significantly reduced from the exclosure to the dryland area. This may show that abandoned areas have a potential according to their diversity and richness for returning into rangelands.