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

Fire is a significant ecological factor that influences rangeland ecosystems, particularly in arid and semi-arid regions, where it plays a crucial role in the growth, development, and evolution of plant species. Historically, controlled burning of vegetation in natural ecosystems has been one of the simplest methods for altering and enhancing habitats, as well as for eliminating pests, diseases, and undesirable plants, while also modifying vegetation cover. Understanding the effects of fire on the characteristics of rangeland vegetation is essential for effective post-fire management. Therefore, this study aims to investigate the impact of fire on specific vegetation characteristics and to analyze vegetation responses to fire, with the goal of improving the management of the Sanandaj rangelands.

For this study, three areas Khalichian, Hasanabad, and Haft Asiab located around Sanandaj and affected by fires one to three years prior were selected. Following field surveys and sampling, the flora of these areas was identified using available resources. Vegetation types were determined through the physiognomic-floristic method. Six sites were established for vegetation sampling, comprising three burned sites and three control sites. Each pair of burned and control sites was matched based on topographic conditions, including elevation, slope percentage, and slope direction, to minimize the effects of environmental gradients and focus on the impact of fire. In each site, two transects (one along the slope and one perpendicular to it) were established, with 15 plots along each transect, resulting in a total of 12 transects and 180 plots. Within each plot, vegetation characteristics such as the percentage of canopy cover of plant species, bare soil, stones and gravel, and litter were estimated. The Shannon-Wiener index was utilized to calculate diversity and evenness, while the Margalef index was used to assess richness. An independent t-test was conducted to compare the mean vegetation characteristics.

The results revealed a significant decrease in the canopy cover of shrubs in the burned sites, accompanied by notable increases in the cover of grasses and both annual and perennial forb plants. Total canopy cover, bare soil percentage, production, and species richness significantly increased in all three areas as a result of fire, while litter significantly decreased. Total rangeland production in the fire-affected sites was significantly higher than in the control sites (P < 0.01), with increases of 26.48%, 26.48%, and 40.14% observed in Khalichian, Hasanabad, and Haft-Asiab, respectively. The difference in the species diversity index (Shannon-Wiener index) was not significant in Khalichian; however, it showed a significant increase in the other areas. Comparisons of the Margalef species richness index indicated that fire enhanced species richness in all three areas, with increases reaching significance at the 1% level. The species evenness index exhibited a significant increase in Hasanabad and Haft-Asiab, but not in Khalichian. An examination of plant composition in the studied areas indicated that fire reduced the prevalence of woody species while promoting an increase in herbaceous plants.

This study concluded that fire generally results in an increase in live vegetation cover, a reduction in litter, and an increase in bare soil. Additionally, fire alters plant composition, favoring herbaceous plants over woody species. Therefore, it is recommended that controlled burning be implemented in grasslands where plant composition has shifted and woody species have proliferated. Such practices should be considered alongside other economic, social, and environmental factors to enhance rangeland conditions.

Livestock grazing significantly influences the structure and dynamics of vegetation in rangelands, prompting the implementation of exclosure operations as a management strategy. Exclosure involves restricting livestock access to rangelands and is recognized as an effective method for rangeland management and improvement. Numerous studies suggest that exclosure operations lead to positive changes in vegetation indicators, including cover structure, production levels, and species diversity. This research aims to investigate changes in vegetation canopy percentage, production rates, and species diversity under exclosure management in the semi-steppe rangelands of Ghalehgharak, Shahrekord.

Sampling locations were selected within the exclosure site (Ghalegharak) and an adjacent grazed site. Plant cover sampling was conducted using a random-systematic method over multiple years (2016 to 2021). Four parallel transects of 100 meters in length were established at each site, with 40 plots of 2 * 2 square meters placed along the transects. Canopy cover percentage was determined using the theoretical estimation method, while biomass was measured through the cutting and weighing method. Species diversity was assessed using Simpson and Shannon-Wiener indices, and species richness was compared using Margalef and Menhinich indices in the Past software. Range condition was determined using modified four-factor and six-factor methods, and trends were evaluated using scale and comparison methods.

Over the five-year study period, the exclosure site exhibited canopy cover percentages ranging from 34.57% to 52.68%, while the grazed site showed variations from 22.15% to 32.76%. Biomass on the exclosure site ranged from 1215 to 1908 kg/ha, whereas the grazed site's production varied from 693 to 1025.6 kg/ha. The rangeland status was determined as moderate for the exclosure site and poor for the grazed site. The trend for the exclosure site was positive, while the grazed site trend was negative. Significant differences were observed between most evaluation indicators for the enclosed and grazed sites, with exclosure enhancing vegetation indices, canopy cover, and biomass. Exclosure significantly increased species diversity and richness, as indicated by Simpson, Shannon-Weiner, Margalef, and Menhinich indices.

The research findings indicate that exclosure positively influences vegetation, biomass, and species diversity in rangelands. Given the declining performance of grazing rangelands in recent years, implementing exclosure operations and strategic livestock grazing management emerges as a favorable approach for pasture improvement and altering current trends.

The impact of grazing on the carbon cycle in mountain rangelands depends on various factors, including management practices and environmental conditions. However, the effects of grazing on carbon stocks remain uncertain due to challenges in tracking small changes in rangeland carbon stocks, lack of baseline information, and limited long-term grazing management data. This study aims to investigate the relationships between plant and soil parameters and organic carbon storage in a 10-year-old exclosure in the mountain rangelands of Asadabad, Hamadan.

Two study sites, one under grazing and the other under a 10-year-old exclosure, were selected in a manner that minimized the gradient effect of ecological and biological factors. Vegetation and topsoil samples were collected along two 100-meter transects at 20-meter intervals, resulting in a total of 10 plots in each area. Vegetation parameters, including percentage cover, diversity (Simpson index), evenness (Shannon-Wiener index), and richness (Margaluf index), were calculated using Past 4.03 software. Soil organic carbon, phosphorus, potassium, and nitrogen were measured. Statistical analysis was performed using SAS V.4.1 software, and the distribution of variables was analyzed using principal component analysis (PCA) in Canoco 5 software.

The findings revealed higher vegetation cover and plant diversity (richness and evenness) in the exclosure area. The vegetation cover percentage and species count in the grazing area were 35.1% and 127, respectively, while in the exclosure area, they were 67.6% and 139. The carbon stocks in vegetation and soil were significantly higher in the exclosure area, with values of 83.13 and 74.35 ton/ha in the soil surface, and 0.00219 and 0.00273 ton/ha, respectively (p < 0.05). The exclosure area exhibited a significant increase in Simpson diversity index (13.83) compared to the grazed area (12.63). Additionally, the Margaluf richness index showed a significant increase in the exclosure area. Soil phosphorus, potassium, and nitrogen nutrient measurements indicated an increase of 51%, 25.7%, and 15% in the exclosure area (p < 0.05). Correlation analysis revealed a significant linear relationship between organic carbon and phosphorus (r = 0.55) and nitrogen (r = 0.80) (p < 0.05). However, no significant correlation was observed between plant diversity indices and vegetation organic carbon storage.

The study demonstrated the positive impact of long-term exclosure on soil and vegetation parameters in mountain rangelands (p < 0.05). Exclosure not only enhanced plant and soil organic carbon storage but also resulted in increased soil nutrient levels, vegetation cover, and diversity and richness indices. The significant increase in plant diversity highlights the suitability of the Simpson index for evaluating diversity in mountain rangelands. However, the lack of a significant linear relationship between diversity index and organic carbon stocks in plants and soils suggests that factors other than plant diversity directly influence carbon stocks in mountain ecosystems.

A large area of Iran rangelands is located in arid and semi-arid areas which a significant percentage of them have been degraded and are not in good condition. In these areas, vegetation restoration is not easy due to the water scarcity. Water harvesting operations are among the necessary management measures to restore and develop the rangelands of these areas. Water harvesting operations improve the rangeland restoration conditions by increasing the available moisture for plants. But not all water harvesting operations are equally effective and may not have the same effect on rangeland restoration in different areas. Therefore, it is necessary to compare such operations in different areas to be able to choose the best water harvesting operations. Therefore, this study investigates the efficiency of two water harvesting methods in the rehabilitation of arid vegetation in Hormozgan province.

In this study, three treatments have been considered: control area, area under microcatchment operation and area under water spreading system. Systematic-random sampling method was used to measure vegetation. Three 100 m transects were laid out in each area. Vegetation attributes were measured in ten 2×2 m plots located along each transect. In total 90 plots, the percentage of canopy cover and the number of the plant species were recorded. The biological form of plant species was determined based on the Rankier classification method. In addition, the percentage of rocks and pebbles, litter and bare soil were determined in each plot. To study the flora of the study area, all plant species in the region were sampled and identified using reliable references. To evaluate species composition in all three sites, plant functional types were used. One-way analysis of variance followed by LSD were used to compare control area, area under microcatchment operation and area under water spreading system in terms of vegetation attributes. The rate of vegetation attributes change was also determined. Detrended correspondence analysis was used to investigate the relationship between plant species and water harvesting operations and control areas.

The results showed that there was a significant differences between water harvesting operations and control areas in terms of bare soil, litter and vegetation (P <0.05) The water spreading system and microcatchment operation had a significant effect on vegetation canopy and litter cover in the region (P <0.05). Examination of plant functional types also showed that palatability classes II and hemicryptophytes had more chance to develop under water harvesting operations respectively. In terms of life form, water harvesting operations had the most positive effect on forbs and grasses, respectively (P <0.05). The results also showed that the families Poaceae, Chenopodiaceae and Fabaceae were successful families in the sites under water harvesting operations, especially the sites under water spreading system. The rate of vegetation attributes change was increasing in the area under water spreading system compared to the area under microcatchment operation, except for the bare soil. The highest and lowest positive changes belonged to litter and Simpson index with a mean of 9.07±0.62 and 0.48±0.25, respectively. The results of DCA showed that Cenchrus pennisetiformis،، ‏Tephrosia persica، ‏Atriplex leucoclada‏ ، ‏Cornulaca monacantha‏ ,‎ ‎Cynodon dactylon were the most important species related to water spreading system and microcatchment operation.

Both water spreading system and microcatchment operations improved the quality and quantity of vegetation in the region, but the effects of water spreading system were greater than microcatchment operation in restoring vegetation. According to the ecological indicators considered in this study, water spreading system is recommended to restore vegetation in arid and semi-arid regions. In the end, it is suggested that economic and social indicators such as the cost of implementing various water harvesting operations should be also considered in future studies, to combine all ecological, economic and social indicators to suggest the best water harvesting operations for rangeland restoration.

Urban green spaces, particularly trees, have great potential to sequester carbon from the atmosphere and mitigate the impacts of climate change in cities. The aim of this study was to estimate the carbon accumulation in the biomass and soil of Robinia, Cupressus, Fraxinus and Chamaecyparis tree species in Toos Nozar forest park in Sanandaj. For this purpose, the type of species, height and diameter equal to the chest for total trees in the permanent plots were recorded to determine the carbon biomass of the tree above and below ground and estimates of carbon storage were performed using allometric equations. The results showed that the total carbon storage in Toos Nozar forest park is 113.68 tons per hectare. Examination of the total density of stored carbon showed that the highest amount of carbon was stored in the soil and the lowest in the litter and grass cover of Toos Nozar forest park. The results emphasize the effect of tree species on carbon sequestration. Cupressus is more potent than other species in carbon storage. By recognizing the species that have more potential for carbon storage and also examining the management factors that affect the carbon storage process, it is possible to follow the improvement and rehabilitation of urban forests from the perspective of carbon sequestration index. The results of this study reveal the value of urban trees not only as ornamental and aesthetic lands but also in reducing the effects of climate change at the local level.

Biodiversity of rangeland ecosystems is directly affected by the biotic traits and environmental factors of the ecosystem. These ensures the sustainability of the ecosystem against environmental and biological changes. The aim of this study was to investigate the response of Performance diversity and species diversity indices to topographic-climatic factors in Angmar region, Mazandaran province. For the task plots were placed in the study area Plant feature including leaf area, dry matter percentage and plant height in each plot were measured and recorded. Environmental factors included topography (slope, aspect and altitude) and climatic factors included average annual temperature, humidity and rainfall were mostly the target features. Performance diversity indices including FAD1, FAD2 and MFAD, FDvar performance divergence indices and FRao performance uniformity indices as well as species diversity indices (Simpson, Shannon, richness and uniformity indices) were calculated in Fdiversity package and to evaluate the significance of the relationship between environmental factors and these indicators, the generalized linear regression (GLM) model was used in R software. The results showed that relationship between species richness and rainfall, altitude and Shannon index was significant only with slope. Simpson index was significantly associated with direction and altitude variables, but uniformity was not significantly associated with any of the environmental factors. The results of Spearman correlation between species diversity indices and performance characteristic diversity indices show that among the species diversity index, Shannon index has the highest correlation with FAD1 yield diversity index. In general, the results showed that topographic-climatic factors have an important relationship with yield. There is a positive relationship between species characteristics in the ecosystem and ecosystem processes.

The complexities of the relationship between biodiversity and human welfare can be simplified by identifying the impact of species diversity on ecosystem function. Since annual production plays an important role in the grazing management and sustainability of rangeland ecosystems, this study examines the relationship between species diversity and annual production of semi-arid rangelands in Khabar National Park under the hypothesis of ecological nest. The annual production of species in 1×1 square plots was estimated in two rangeland types of Artemisia sieberi and Artemisia sieberi- Stipa barbata using the cutting and weighing method. The results showed that although the two plant types differed significantly in terms of annual production (p < /em> <0.05), but there was no significant difference between the two rangeland types in terms of diversity indicators of Shannon, Simpson, Margalf, Manichae, and uniformity index. Pearson’s correlation analysis showed that annual production had a positive and significant relationship with species diversity indicators in Artemisia sieberi- Stipa barbata type; however, no significant relationship was observed in Artemisia sieberi. Contrary to the hypothesis of the ecological nest, species did not have the same contribution in annual production, and the dominant species of Artemisia aucheri had the highest contribution in production. According to the hypothesis of mass ratio, the diversity of functional traits in the dominant species has led to better success of rangeland type the Artemisia aucheri- Stipa barbata than the Artemisia aucheri in terms of annual production. In general, it is recommended that conserving of the composition of plant communities is more important to protect ecosystem services compared to maintaining the maximum number of species.

The plant communities locating at the margins of the waterways play a vital role in the ecological processes and ecosystem services in the semi-arid mountainous regions. In this study, variations of plant diversity and composition at different distances from the waterway and its slope aspects were investigated. For this purpose, 15 sub-basins with a variety of area and length of waterway, in both northern and southern directions, were selected in the mountainous rangelands of Anbaran Chai. For measurements 20 plots of 1m2 in each sub-basin were established and vegetations were surveyed. Different distances from the waterway (0-25, 25-50 and 50-75 m) were selected for the measurements in the growing season in 2017. By grouping the species into scientific groups and calculating species diversity, statistical comparison of the parameters was performed by one-way ANOVA and t-test. The results showed that the highest diversity happens at the second distance group (25-50 m).This put emphasis on the hypothesis of occurring maximum diversity in the medium environmental disturbance conditions. In this regard, Shannon-Wiener species diversity index values ​​were 1.38, 1.40 and 1.39 for first to third distances, respectively. Northern slopes are more diverse (1.45) than southern slopes (1.30) due to high humidity. The results suggests that if the goal of range management is to prioritize the area on the basis biological practices emphasis should be put on the first and third distances from the waterway.

With thirteen critical erosion hubs containing an area of roughly 532 thousand hectares, and 14 regions influenced by wind erosion with an area of 1144311 hectares, the Yazd province ranks fifth among the Iranian provinces in terms of the magnitude of crisis hub, and third in terms of the extent of affected areas. The history of desertification activities in the province dates back to 1970, based on which some 42,000 hectares of the Yazd-Ardakan plain has been afforested. As a phreatophyte member of the Chenopodiaceae family, Haloxylon aphyllum is mainly characterized by such features as xerophyteness, halophyteness, and psamophyteness, and is considered as the most compatible species among desert plants. On average, each mature Haloxylon aphyllum tree needs 2.4 m3 water annually for optimal growth. This study sought to evaluate and identify the strengths and weaknesses of the Haloxylon plantations carried out with ripping method in arid region in an attempt to fight against desertification. The annual precipitation rate in the Ashniz Meybod Desert rangeland was estimated to be 74 mm, and the vegetation was found to be less than 2% before Haloxylon plantations. The region’s soil has a medium block structure up to a depth of 30 cm and is structureless from the depth of 30 to 120 cm, and its stability in a dry state is very tough. The soil texture in this horizon is clay-silty. The maximum depth of the area’s ripper is 80 cm, and hardpan layer is not completely eliminated. Moreover, during the 1990s, ripping operations and Haloxylon plantations was carried in the study area where 250 Haloxylon trees were planted in each hectare within three years in the water distribution plain and irrigated 12 times.  

This study investigated the Haloxylon aphyllum plantations in the region mentioned. To this end, four transects (300 M) were randomly – systematically considered in each area, on each of which some fifteen plots (10 m2) were randomly collected. For each plot, the vegetation characteristics including the total percentage of vegetation, density, Haloxylon and Artemisia species’ canopies, harmony, and richness and diversity of species, and soil characteristics including Permeability‎ and carbon sequestration, were measured. Moreover, to study the harmoniousness, richness, and diversity of species, the Sympson, Hale, and Margolf methods were used respectively. In addition, to measure the soil’s permeability and moisture, Double Cylinder and TDR methods were used, respectively. The collected data were examined in terms of normality via Shapiro-Wilk test, and analyzed through one-way variance and Dunken tests. As for the inventory, the transect-plot method was performed systematically-randomly. Therefore, for preparing the inventory of the region’s vegetation, eight transects and one-hundred and twenty 10 square meter-plots were used. Moreover, eight and sixteen measurements of the soil’s water permeability and carbon sequestration were made in each site and the whole area, respectively. Furthermore, each season’s soil’s moisture was measured eight and sixteen times in each site and the whole area, respectively, leading to 24 and 48 measurements for the three seasons in total.  

The study’s findings showed that the ripping operations and Haloxylon plantations with a density of two hundred trees per hectare increased total vegetation by 1.87 percent, Haloxylon canopy by 1.68 percent, and the Haloxylon density by 83 trees Per hectare. It was also found that ripening operations had no significant effects on the Artemisia’s density and canopy as the region’s dominant species, and the richness, diversity, and uniformity indices. The pits made following the ripping operations for seeding have led to the accumulation of the surrounding wastewater inside the pits, with the soil moisture in the ripping operations site being 4.25% greater than that of the control site in May. Moreover, the ripping operations have increased the soil’s permeability and carbon sequestration by 0.75 cm per and 1.31 tons per hectare, respectively, which are not significant.  

As ripping operations up to a maximum one meter cannot eliminate the hardpan, the implanted seedlings cannot develop their roots in the soil not be able to take root and would only remain survived and fresh so long as they are irrigated. On the other hand, continuous irrigation to maintain the current situation would be very costly and economically unjustified. Therefore, due to low precipitation rate, inappropriate distribution, and frequent droughts in arid and desert regions, and the high costs of preparing the ground, provision of seedlings, plantation, and irrigation, the attempt to implement the Haloxylon plantation operations with high density for three consecutive years based merely on the region’s precipitation whose maximum ecologic capacity comprised of 1.87% vegetation with regard to the climatic and adaptive conditions of the study area, seems really unusual and.

This study aimed to investigate the effects of livestock grazing in the way, changing the qualitative and quantitative composition of the plant As well as the different groups of plant species density in the enclosure in Boralan area. The vegetation and soil samples and 360 plots at 18 transect method - systematic random out of the enclosure and enclosure in three annual enclosures took place. The position of each plot were recorded using a Global Positioning System. Tilt maps and directions enclosure was prepared. Using the parameters plots a square meter of canopy cover, density, percentage of dead leaves, rocks and pebbles and bare soil were measured. During the growing season and plant species samples were identified using available resources. Shanon Vynz, Brillouin and uniformity Simpson and Simpson, Camargo, Smith and Wilson nor at the species level using Ecological Methodology software version 6.2, respectively. Compare enclosure vegetation parameters using SPSS software (version 16) and The enclosure and the enclosures were analyzed using multivariate methods. The results showed that the obtained in the studied sites (enclosure) 11 dark, 24 genera and 24 species, is widespread. Inside the enclosure with 24 species, with 17 species richness is more than grazed out. Values ​​of richness, diversity and uniformity within the enclosure is greater than the outside enclosure.

Lack of rainfall and the subsequent drought could lead to changes in rangeland ecosystems. Monitoring rangelands to distinguish climate change from management is considered as one of the favorite research areas among range experts. Several studies have so far conducted on the effects of drought on vegetation in rangelands whose results indicate that vegetation and species density are strongly affected by drought. For instance, Zhang et al (2016) investigated the drought events in China over the period 1982–2012 and examined the impacts of droughts on vegetation productivity. The findings of his study showed that vegetation productivity was significantly influenced by droughts, and that the effects of drought on vegetation productivity varied with vegetation type. It was also found that from among major vegetation types, grasslands displayed the greatest sensitivity to droughts. However, the impact of climate change on biodiversity indicators has been underresearched. In fact, the problem of biodiversity response to changing microhabitat conditions has not been fully elucidated (Jastrzębska et al, 2009). Therefore, Ammodendron persicum reserve was selected for an investigation of trend change of soil physical and chemical properties and plant biodiversity inn response to climate change.

Having studied the region's climate and annual rainfall, soil and vegetation sampling was done at a specified time and place in wet (2007) and dry (2018) years based on Standardized Precipitation Index (SPI), taking a specific framework into account0. Inside the reserve, three points were selected as the known sites, digging 10 soil profiles 100 cm deep in the places that had already been determined. Physical and chemical properties such as soil texture, EC, pH, Organic matters, lime, and soil saturation were identified at the soil laboratory. In order to determine the plot size, a minimal area method was used for sampling. In each plot, a list of plant species, density, the percentage of canopy cover, stone and gravel, bare ground and litter were recorded. As for setting the range condition and its trend, four-factor and scale methods were used (Moghadam, 2009). The total vegetation, litter, soil, rock cover, species density and biodiversity indices such as total richness, average richness, Shannon-Wiener diversity index and Simpson dominance index, were also estimated. Furthermore, physical and chemical properties of soil, vegetation cover percentage, and the number of individuals, richness and diversity of two years were compared by the t-test.

The results of the study indicated that after 11 years, the amount of sand, silt and pH increased and clay, electrical conductivity and soil moisture content decreased significantly. Soil texture had also changed from loamy sand to fine sand. It was found that Amiodendron persicum reserve was changed from the hydrologic group B to the hydrologic group A because of drought. Moreover, differences of density, total richness and Shannon-Wiener and Simpson dominance indices were significant at 0.05 and 0.01 between 2007 and 2018. Also, the percentage of vegetation and rock cover, species density, total richness and species diversity showed a significant decrease, and the range condition changed from moderate to poor. However, there was no change in the soil organic material, lime, litter, and bare soil percentage.

The soil and vegetation of the study area have undergone some changes due to wind erosion and the recent 10-year drought, the first of which seems to be the change in soil texture. Actually, the soil texture has changed from loamy sand in 2007 (as wet) to fine sand in 2018 (as a drought). In a similar vein, Zhao et al. (2006) investigated the effects of desertification on soil and crop growth properties in Horqin sandy cropland in Inner Mongolia, north China, concluding that wind Erosion increased soil pH from 8.66 to 8.92, and that soil clay and average soil moisture decreased by 59.6% and 51.8% respectively.The findings of our study suggested also a slow change in the percentage of litter, soil organic matter, and lime, and that drought, except for the average number of species in the plot (average species richness), had a significant effect on other biodiversity indices including the total richness, species diversity, and species dominance, resulting in a decrease in the number of species (total richness). Furthermore, the shannon-weiner diversity index was found between 2007 and 2018. It could be argued that the area has barely been covered by annual and seasonal species due to drought, and there are perennial species such as Ammodendron persicum and Stipagrostis pennata in most sampling plots, leading to an increase in the dominance of Simpson index in 2018.

Management methods and utilization levels may significantly affect species diversity in the protected regions. Therefore in this research, 3 protected sites were selected in the marginal rural areas at the eastern edge of Golestan National Park, Iran. Dasht, Chashmehkhan and Robat Gharebill villages were respectively under use by human, livestock and wildlife. In May 2018, 3 modified Whitaker plots were established. Each plot included 3 quadrates of 100 m2, 6 quadrates of 10 m2 and 30 quadrates of 1 m2. Total plant diversity and diversity of medicinal plants were highest in Dasht and lowest in Chshmehkhan sites. Intense livestock grazing in Cheshmehkhan led to higher (27%) proportion of medicinal plants, but the plant species were mainly annuals and spiny with low medicinal values. In contrast, highest number of valuable medicinal plants and high number of endemic species were in Dasht site, where slight utilization were done by local inhabitants. In conclusion, livestock grazing may lead to the highest negative impacts on reducing diversity of total plants and medicinal plants as compared to the wildlife and human use.

One of the ways of restoration and reclamation of damaged rangeland is to use different methods of rain harvesting such as pitting, counter furrowing, flood spreading, small arc basins system and etc., along with the reduction of runoff, it increases the soil moisture content and thus increases vegetation cover. Biodiversity is most commonly used to describe the number of species. It is studied in 3 levels, including genes, species, and ecosystems. However, species diversity is a major issue of biodiversity on a local and regional scale. Species composition and biodiversity are among the fastest and most important indicators for determining rangeland ecosystems condition. Due to the new construction of this structure in the rangelands of Iran, so far, little research has been done on the effect of small arc basins system on vegetation and forage production. Particularly, there is limited research on the variation of richness and species diversity by Construction of this structure. Abdollahi et al. (2016) investigated the effects of crescent pond structure on vegetation and soil parameters in Saravan rangelands of Sistan and Baluchestan province. The results of their research showed that, significant differences were found for all vegetation parameters between the crescent structure and control treatment, indicating the positive effect of crescent structure on vegetation parameters. The purpose of this study was to investigate the effect of constructing small arc basins system has been investigated on the composition of vegetation and biodiversity in the rangelands of South Khorasan province. Sampling in the rangelands of Sarbisheh, South Khorasan Province, was carried out in small arc basins area. Vegetation sampling was carried out in the rangelands by systematic-random method at the flowering stage of the dominant plant species in the spring of 2014.vegetation characteristics such as density, composition, cover percentage, and species richness indices (Margalef and Menhinick), species diversity indices (Simpson, Shannon - Wiener and Fisher's alpha) and species evenness (Pielou) were investigated in two areas (small arc basins area and the control area).The all biodiversity indices were calculated using PAST software. To compare the vegetation characteristics including density, composition, vegetation percentage, species richness, diversity and evenness, independent samples t-test were used. In general, 30 plant species were identified in two areas (small arc basins area and the control area), which belong to 17 families and 27 genera. The results showed that the number of plant species in the control area is 9 and in the small arc basins area is 30 species. The results of comparing the total vegetation cover percentage in both areas showed that the percentage of total coverage is very significant (p <0.01). The effect of construction of the small arc basins area system on the density of rangeland plants was very significant (p <0.01) and this system has significantly increased the density of rangeland plants., there is a significant difference in species diversity between the two regions in terms of Simpson diversity index and Shannon-Wiener's diversity index, but this difference is not significant in the alpha-Fisher's index. The results of the data on the study of richness indices also show that the Margalaf's richness index shows a very significant difference in the comparison of species richness in the two study areas, but this difference was not significant in terms of the Menhinick's index. Discussion and The results showed that the construction of small arc basins in the study area increased the number of plant species, species density and vegetation percentage compared to the control area, which indicates the positive effect of this structure on improving the ecosystem conditions. Research in this area also confirms this result. The results of this study indicate that the number of annual and perennial species in the control area (totally nine species) from 4 and 5 species in the control area has increased to 15 species for both species (a total of 30 species) in the small arc basins area. As well as, the results indicate that the vegetation cover percentage and frequency of perennial species is more than annual species. Several studies have indicated that species diversity has a significant relationship with soil texture and soil moisture. Since the construction of small arc basins leads to changes in soil moisture content and soil texture. Therefore, it has a significant effect on species diversity. Finally, according to the results of this research as well as previous researches, we can say that the effect of small arc basins system was positive on the ecological characteristics of vegetation in the study small arc basins treatment. Therefore, it can be considered as one of the most effective methods for the restoration of degraded rangelands.

Knowing medicinal plants, measuring structural features and their species diversity indices are of the essential requirements to determine the suitability of rangelands for the use of medicinal plants. In this regard, the research was carried out in the mountain rangelands of Anbaran. For this purpose, vegetation cover was measured using 320 plots of one square meter, with a distance of 10 meters from each other along 100-meter transects in 16 vegetation types, and the values of species diversity indices in different elevation classes and aspects were calculated. Based on the results, 16 medicinal species are distributed in the plant composition, with a relative importance varying from 0.9 to 59. The highest relative importance is related to Verbascum erianthum, Cynodon dactylon and Acroptilon repens, and the least belongs to Papaver acrochaetum, Hyoscyamus arachnoideus, Iris falcifolia, Allium scabriscapum and Matricaria chamomilla.The results showed that the values of the Shannon–Winear  in the altitudes of 1750-1500 meters and 1750-200 meters were 0.569 and 0.651, respectively, showing no significant difference with each other. The value of the index in the northern and southern directions is equal to 0.691 and 0.511, and the northern aspects are more favorable than the southern ones. Therefore, with regard to the range of Shannon–Winear index (0-4.5), it seems that the rangelands are not desirable for the species diversity of medicinal plants, which is necessary to increase species diversity with direct management. The findings of this study can be used to locate medicinal plants in order to protect, exploit, seed production and provide part of the livestock holder’s income.