جستجوی مقالات مرتبط با کلیدواژه « Exclosure » در نشریات گروه « آبخیزداری، بیابان، محیط زیست، مرتع »

Introduction and Objective:

Soil is a part of every ecosystem and one of the most valuable and important sources of food production in every country, which plays a significant role in the continuation of human life. Today, soil erosion is one of the most important threats to water and soil resources and has become one of the most important human environmental problems. Soil supports food security and environmental quality, both of which are essential for human life. The purpose of this research was to evaluate the performance of watershed management measures in the treated sub-watershed of Khamsan representative watershed. The lake of Gavshan Reservoir has receded at the maximum level to the outlet of the Khamsan watershed. This has caused soil erosion from this watershed to enter the Gavshan dam lake directly and with the shortest distance. Therefore, it is very important to evaluate the performance of the measures taken in this watershed, especially based on the distribution map of erosion and sedimentation.

Materials and Methods:

The first step of measuring soil erosion using cesium-137 is to select a control or reference area. Slope and land use maps were used to determine the final sampling points in this research. After measuring the activity of cesium-137 (becquerels per kilogram of soil), the presence of cesium-137 per square meter of soil sample is needed to calculate soil erosion. The activity of cesium-137 in reference points was compared with the activity of cesium-137 remaining in the research points. If the cesium-137 activity of the soil samples was lower than the activity in the reference profile, soil loss and erosion occurred. The increase in the activity of cesium-137 in the soil samples compared to the reference profile was indicative of soil transfer to the sampling point and considered as a sedimentation site.

Results  and Discussion:

The results of the comparison of the same points in the rangelands in both treated and control sub-watersheds showed that sedimentation conditions prevail over erosion. The amount of sedimentation in the rangelands with watershed management measures (contour trenching, seeding and exclosure) in the treated sub-watershed with a slope of 20-30% was more than the rangeland with the same characteristics in the control sub-watershed. In rangeland with watershed management measures, erosion conditions prevailed in the slope of more than 30-60%, but erosion in protected conditions was less compared to the same point in the control sub-watershed.

Conclusion and Suggestions:

The results of the amount of erosion and sedimentation in both treated and control sub-watersheds in rangeland with a slope of 20-30% showed that sedimentation conditions prevail. However, the amount of sediment deposition in the rangeland with watershed management measures in the treated sub-watershed showed an increase of 1445.65% compared to the rangeland without protective measures in the control sub-watershed, which indicates the positive effect of watershed management measures in the treated sub-watershed rangelands with a slope of 20-30%. This finding shows the special effect of contour trenching on increasing sediment trapping, reducing the volume and speed of runoff, and thus reducing the power of sediment transfer. Also, in the slope of 30-60%, although erosion conditions prevailed in both treated and control sub-watersheds, watershed management measures in rangeland in the treated sub-watershed showed a 28.57% reduction in soil erosion compared to the same point in the control sub-watershed. Considering the positive performance of watershed management measures, especially contour trenching, it is suggested to use these measures in other watersheds similar to Khamsan representative watershed.

IntroductionRangeland provides numerous ecosystem goods and services. Most rangeland management decisions focus on forage production, and this can lead to the loss of other rangeland ecosystem services. One of those services is carbon sequestration, the removal of carbon dioxide from the Earth's atmosphere and its storage in the ground. Rangeland, which covers approximately half of terrestrial ecosystems, is one of the most important sinks for atmospheric carbon dioxide. Photosynthesis, respiration and decomposition are the main processes in the ecosystem that determine how carbon is stored in the soil. Anthropogenic activities like livestock grazing can significantly alter soil carbon storage. Unfortunately, human activities have resulted in lower soil carbon and increased global climate change. Livestock grazing is one of the most significant factors affecting the structure and functioning of ecosystems. Grazing livestock can affect the amount of carbon in the soil through reduced vegetation cover, altered species composition, soil degradation, urination and defecation. On the other hand, changes in the quantity and quality of forage production by livestock grazing have a strong effect on the welfare of the beneficiaries. Consequently, knowledge of the relationship between forage production and other ecosystem goods and services such as soil carbon is essential to the sustainability of ecosystems. It is important to study the quantity and quality changes in rangeland production in relation to different livestock grazing intensities on soil carbon. However, this information can assist range managers in providing techniques to promote soil carbon storage. The purpose of the study is 1) to determine annual forage production in rangelands at different grazing intensities, 2) to study the quality of rangeland forages produced, 3) to assess soil carbon content at different grazing intensities, and 4) to assess the relationship between rangeland production and soil carbon content at different grazing intensities. Material and MethodsA rangeland adjacent to Khabr National Park in Kerman province was selected as the study area. The study area is shrub- dominated species Artemisia aucheri Boiss. Three sites with different grazing intensities (for example, exclosure, high grazing and moderate grazing) were sampled. At each site, three 100m transects with 50m intervals were set up. Ten quadrats were randomly assigned to each transect. For each quadrat, the species met were recorded and their number of individuals and the amount of forage produced were measured. The annual forage production (forage quantity) was measured using the clip and weigh method. To determine forage quality, crude protein, acid detergent fibre (ADF), dry matter digestion and metabolizable energy were estimated for each species. Additionally, a soil sample was taken from each of the quadrats. The samples were air-dried and sieved with a 2 mm sieve. The organic carbon of the soil samples was determined through wet oxidation with Walkley-Black chromic acid. Then, the species importance index (IVI) was estimated using relative frequency (Fr), relative density (Dr) and relative dominance (Dor). One-way ANOVA and LSD were used to compare different grazing intensities in terms of soil carbon, annual production, crude protein, ADF and metabolizable energy. Pearson's correlation was used to examine the relationship between soil carbon and annual production with the qualitative attributes of production, ie. The primary component analysis (PCA) was used to identify the most important species in terms of production at the three sites with different grazing intensities (exclosure, high grazing and moderate grazing). Principal Component Analysis (PCA) was used to identify the most important species in terms of production at the three sites with differing grazing intensities (exclosure, high grazing and moderate grazing). Results and DiscussionThe quantity and quality of forage has been reduced in the livestock grazing sites. The study area has a long history of cattle grazing, which has significantly altered the composition of the vegetation. About 26% of the exclosure site species had been removed from the plant composition of medium pasture sites, most of which are appetizing species. Although the amount of organic carbon in the soil increased at the exclosure site, it was not significantly different from grazing sites. Therefore, despite the improvement in forage quality and quantity, soil organic carbon had shown a lower reaction to the exclosure. Due to the presence of acceptable species, there was a positive relationship between forage quantity and quality at the exclosure site. Although A. aucheri was still dominant shrub species in the site with medium grazing intensity, there was no significant relationship between forage quantity and quality due to the decrease of palatable species. With the increase in the number of non-platable species in the high grazing site, there was a significant negative relationship between forage quantity and quality. There was a positive and meaningful relationship between soil carbon and the amount and quality of forage at the exclos site. The relationship between soil carbon and forage quantity and quality was not significant on grazing sites because of a change in plant composition. In the sites under grazing, palatable forbs such as Tragopogon jesdianus Boiss. and Lathyrus annuus L. were not observed and perennial grasses were significantly reduced. It should be noted that forage production of forbs has not changed much on the site with average grazing compared to the exclosure site. Perennials, especially woody plants, were severely reduced at the site with high grazing intensity. There were no bushes observed at that location. Annual grasses had increased in the site with heavy browsing. As perennials decrease, space and resources become available for the invasion of annual plants, especially annual grasses. Therefore, Bromus tectorum L. had the highest forage production in the   high grazing area. In terms of crude protein, the high grazing area had low quality forage. Since livestock grazing and subsequent changes in plant composition do not greatly impact soil carbon, livestock management can contribute to the improvement of plant composition and forage production at this site. Taking into account the impact of grassland management on other ecosystem functions, it is suggested to explore the relationship between the amount of production and other functions of quality rangeland ecosystems in order to sustainably manage rangeland ecosystems.

The aim of this study was conducted to investigate the effect of 25 years old exclosure on the function of aerial and underground organs of Trifolium pratense since may to july of 2017. Three sites inside and three outside of the exclosure were selected in the rangelands in Shoghaldare- Namin rangelands, Ardabil. Three transects with the length of 100 meters were established in each site and from 10 plots of 1 m2 vegetation characteristics including total production, canopy percentage and forbs canopy were estimated. In order to select T. pratense stand and measure the selected parameters (to study the effect of exclosure on the function of different organs of T. pratense), in addition to previous transects, in each site was randomly established 3 transect of 50 meters. Along each transect, 10 random points and in each point the nearest plant was selected. Length of root, stem, inflorescence, plant height and basal diameter of T. pratense were recorded. Moreover, the inflorescences, stems and roots of the selected T. pratense were cut and after air-drying, they were weighed with a precision scale. Results showed that the total production in the exclosure (2413/06 kg/ha) has significant difference (p < 0/01) with the outside of exclosure (963/84 kg/ha). The production of T. pratense inside exclosure (99.83 kg/ha) has also significant difference (p < 0/01) with outside the exclosure (22.75 kg/ha). Interaction of exclosure and elevation has significant effect on canopy cover (forbs and total), number of inflorescences, basal diameter, weight of plant organs (p < 0/01) and recovery effort (p < 0/05).

Current study is investigate the effects of range improvement treatments on vegetation performance in Zaloo-Ab rangeland that is 10 Kilometers far from west south of Abdanan County in Ilam Province. Vegetation sampling was done randomly in every control and corrective operation sites in length of three transects of 100 meters in 30 plots of one square meter. Vegetation specifications including production, density, percentage of cover crown, bare soil, stone and pebbles, litters and different classes of palatability. Obtained data were analyzed by version 16 of SPSS software using t-independent test and variance analysis to compare each corrective and control sites and three corrective sites together. The obtained results showed that provided corrective operations have caused increase in cover crown, production, density of class I and II plants and decrease in class III plants, bare soil and pebbles respected to control site (in one percent level). Results of one-way variance analysis and comparison of averages of measured vegetation specifications in three treatment sites also showed a significant difference in one percent level.

In view of the increasing adoption of rangeland exclosure in order to rangeland improvement and carbon sequestration, investigation of its effects on the soil properties and calculation of the economic value of sequestered carbon is important. The aim of this study was to evaluate the changes in some soil physico-chemical properties, carbon sequestration rate and its economic value following grazing exclosure as compared with open grazing areas in Bozdaghi rangelands in North - Khorasan province, Iran. Therefore, in each area (exclosure and open grazing) three transects of 500 meter length and 200 meter intervals) were set up. Along each transect, five soil samples were taken at the depth of 0–15 cm in a random – systematic method (15 soil samples in each area) and transferred to the laboratory. In the laboratory, some soil physical and chemical properties such as soil texture, bulk density, porosity, saturation percentage, pH , EC , percentage of organic matter, total nitrogen, the amount of cation exchange capacity, exchangeable sodium, potassium, calcium, and magnesium were measured and erodibility index was calculated by using the modified clay ratio relation. Data analysis was performed by using independent t test in SPSS v.16 software. The results demonstrated that establishment of exclosure in Bozdaghi rangelands had significant positive effects on soil physico-chemical properties, and reduced the soil erodability index significantly (P

This research was carried out at the Zagheh research station in Lorestan province. A number of 440 individuals in each year and 2200 individuals in five years were cut and weighted inside and outside the exclosure. The difference in weight between the individuals outside and inside the exclosure indicates the amount of consumption. According to the results, there is a significant difference between the mean value of forage production and consumption in months and in different species (P

The effects of grazing on vegetation and range conditions were investigated in Arshaq, Saiin and Sardul rangelands in Ardebil province over the past 9 years (1998 to 2006).) The vegetation composition, plant functional groups, biomass, species diversity and richness of ungrazed and grazed areas were compared. Plants canopy cover and forage production were measured using one square meter quadrats. According to the results, the average canopy cover of perennial species in the grazed and ungrazed areas were significantly different (P

This research was aimed to study the vegetation changes under grazing and non-grazing conditions during five years in order to evaluate vegetation improvement or destruction over time.The study of vegetation changes was carried out inside and outside the exclosure within the sample units. Each sample unit consisted of two parallel transects with 20 quadrates. Within each quadrate, the canopy cover percentage and composition percentage of each species were estimated. The forage yield was measured by clipping and weighing using one-square-meter quadrates. No significant difference was recorded for the canopy cover of inside and outside the exclosure. Statistical analysis was performed in a completely randomized block design and no significant differences were found among the study years. However, significant differences were found for forage yield of inside and outside the exclosure. Therefore, the reduction in forage yield of outside the exclosure is directly related to the intensity of utilization. The life form of species was determined based on Raunkiaer's system. Hemicryptophytes was the dominant form in the study area. The results showed that although the exclosure caused to improve rangeland vegetation, the difference between inside and outside the exclosure was not significant. Generally, the results indicated that vegetation changes in the study area were slow and gradual and exclosure could not be considered as an improvement method in short-term. Direct human intervention is required for the restoration of rangelands, located in arid regions.

This study was conducted to evaluate the effects of Atriplex canescens on soil properties and organism's activities under grazing and exclosure conditions at Shahriar rangelands. In each site, four transects were selected by random-systematic method and 10 quadrates of nine m2 were established along transects with 30-m intervals. In each quadrate, the amount of seed per plant, litter and the number of nests under shrubs were recorded. A number of five quadrates were also established randomly along each transect, and soil profiles were dug. Soil samples were taken at two depths to measure soil properties. Data analysis was performed by independent T-test and mean comparisons were done by Duncan's multiple range test. According to the obtained results, under exclosure condition, although the study species could increase the nitrogen and potassium of surface soil, increased sodium and EC negatively affected the soil. In addition, significant differences were found for the amount of seed and litter (p

This research was aimed to investigate the effects of exclosure on species diversity changes under grazing and exclosure conditions in the northeast rangelands of Delfan County, Lorestan province. For this purpose, 120 quadrates of 1*1 m2 were established in a randomized-systematic method along 12 transects of 100 m length at four altitude classes (three transects on each altitude class). In each quadrate, the list of species, density, the percentage of canopy cover, litter, stone and gravel, and bare soil were recorded. To evaluate the numerical indices of diversity, Ecological Methodology software (Ver., 6.2) was used and numerical indices of diversity and evenness were calculated. Data analysis was performed in SPSS software (Ver. 18). According to the obtained results, a number of 132 species were identified, belonging to 30 families and 104 genera, of which 124 and 108 species were recorded in the rangelands under exclosure and grazing conditions, respectively. Our results clearly showed higher numerical indices for richness, evenness, and species diversity under exclosure as compared with grazing condition. The canopy cover percentage of perennial grasses and forbs as well as litter percentage was higher inside the exclosure while the canopy cover percentage of annual grasses and shrubs as well as bare soil percentage was lower as compared with outside the exclosure. The density of perennial grasses and forbs increased, while the density of shrubs decreased inside the exclosure. In addition, a higher production was obtained from the rangeland under exclosure condition.

According to determine the factors influencing carbon storage in different land uses in Shahriar, different treatments of cultivation, age and land use, also grazing intensities were selected. These treatments included 18-year old Atriplex exclosure, mean and high grazing intensities, 8-year old Atriplex mean grazing intensity, 3-year old Atriplex exclosure and mean grazing intensity, 2-year old Atriplex exclosure, 8-year old Haloxylon exclosure, rain fed wheat, irrigated barley and control treatment (natural rangeland). after specifying the amount of carbon stored in ecosystem, also some soil and plant properties of study area, the most important factors associated with carbon storage, were tested using PCA test and PC ORD software. Results showed that the most important factors influencing carbon storage are clay of the 2nd and 3rd depth and HCO3 of 2nd depth, also N of 2nd depth, EC of 3rd depth, above ground biomass weight and root carbon. Irrigated barely and exclosure of 18 year old Atriplex fields have the most carbon content, which depends on clay and HCO3, on the other hand, Carbon is related to EC and root carbon in exclosure of 8 year old Atriplex fields.

Grazing animals affect rangeland vegetation structure and function both directly and indirectly. These effects can be assessed in exclosures. In this study, vegetation changesinside and outside of exclosures of Tanglaybid rangelands,located in south-western part of Yazd province, have been investigated. Vegetation changesstudy was carried out in 3 key areas inside and also 3 key areas outside of exclosure and lasted for 5 years (2000-2005). Every key area included 3 transects of 100 meters long and 40 meters intervals. The transects were selected vertical to slope, including 10 fixed plots (2×1 m2). Vegetation cover, density and frequency percentage of each plot species were measured annually. The random- systematic method was applied as a sampling method. Vegetation changes inside and outside of exclosure were assessed, in a completely random plan, applying Duncan's test (P

This research was aimed to investigate the soil function indices in an exclosure region in comparison with non-exclosure. Then, using random plots as a control method, vegetation cover, stones and gravel, and litter were measured. Our results showed that the exclosure region (Saral Research Station) had better condition in terms of function indices in comparison with non-exclosure regions, indicating the positive impact of no livestock grazing for a long time. Northern slope of the exclosure region and the southern slope of non-exclosure region were identified as the most stable (60.26) and unstable (52.8) in the study area. The highest infiltration was recorded for the southern slope of the exclosure region (58.7), and the northern slope of the exclosure region had the highest nutrient cycling (45.63). The western slope of the exclosure region represented the longest inter patch in the whole landscape and the northern slope of exclosure had the largest area and number of ecological patches. Considering the area and number of patches helps the range manager detect the effect of exterior and interior factors on rangeland easier. Overall, long-term exclosure in the Saral region could be mentioned as a suitable method to reduce the runoff, soil erosion, and sediment production.

In recent years the utilization rate of renewable resources especially the pressure of livestock grazing has increased. Uncontrolled livestock grazing has caused reduction of quantity and quality of forage، therefore، studying the effects of exclosure on vegetation changes is very important. In this research، the effects of exclosure on vegetation changes of Sahand rangelands were studied during 2001 to 2006. The vegetation changes were investigated inside and outside the exclosure area، using fixed transects. The results showed that total canopy cover and canopy cover of perennial grasses including Agropyrum trichophorum، Bromus tomentellus، Dactylis glomerata and Festuca ovina increased significantly inside the exclosure area (P<0. 01). In terms of palatability، class I species increased significantly (P<0. 01). Cirsium haussknechtii، one of the important invasive species of the area، decreased significantly inside the exclosure area. There was no significant changes on total canopy cover of outside of the exclosure area. Canopy cover of perennial grasses and perennial forbs decreased (P<0. 05) and shrubs canopy cover increased (P<0. 01). Class I species decreased and class III species increased in outside of the exclosure area but it was not statistically significant. Canopy cover of Cirsium haussknechtii increased in outside of the exclosure area (P<0. 05). No significant changes of soil organic matter were detected inside and outside of the exclosure area during six years.

This research was aimed to investigate the effects of exclosure on vegetation cover and soil properties in the rangelands of Gardaneh Zagheh, Lorestan.For this purpose, constant transects of 60*50 cm were placed with a distance of 1.5 m, and 10 quadrates were established on each transect. Vegetation changes were investigated inside and outside of exclosure. In addition, soil profiles with a depth of 40 cm were dug and soil samples were taken inside and outside of exclosure. According to the results, during the first and last sampling, the forage yield inside of exclosure was calculated to be 36.1 gm-2 and 67.2 gm-2, and outside of exclosure, it was calculated to be 46.1 gm-2 and 91.8 gm-2, respectively. The bare soil outside of exclosure was also higher as compared with inside of exclosure and soil conservation was calculated to be 74% and 95.6% in the years of 1998 and 2004, respectively. Our results clearly showed that in the last year of exclosure, the rock and gravel cover decreased inside of exclosure but it was increased up to two times outside of exclosure.