Proportion Of Coarse Particles Research Articles

Sediment load with metallurgical slag admixture under diverse morphological conditions along submerging karst stream

This study investigates the clastic fluvial sediments of the Jedovnický submerging stream in the section between the Jedovnice village and Křtinský stream (Moravian Karst, Czechia). A total of 28 samples were collected to analyze clast composition, slag content, grain size, and roundness. The sediment primarily consists of allochthonous Lower Carboniferous material (greywackes, clayey shales) with varying amounts of metallurgical slag, occasionally mixed with autochthonous deposits such as rockfall accumulations and tailings from the excavation of connecting adits. The slag content fluctuates, peaking downstream of the erosive section of the Rudické propadání cave, near the Stará řeka passage connection. Grain size distribution is influenced by both surface and cave morphology, as well as hydraulic conditions. The alternation between erosive and depositional zones, along with the unique karstic and speleorelief features, plays a crucial role in clast mobilization. These features include ponors, erosive and paragenetic corridors, sumps, and rockfalls. Fine particle accumulations are particularly noticeable in front of sumps or dams. Throughout the studied section, the proportion of coarse particles (>10 mm and 5–10 mm) gradually decreases, while finer particle content increases toward the resurgence. The roundness of Carboniferous sediments remains relatively constant, although it is significantly influenced by the presence of well-rounded, weak and ductile slag clasts. Overall, both the slag content and the proportion of well-rounded and rounded clasts in the coarser fractions (>10 mm and 5–10 mm) show a decreasing trend toward the resurgence.

Enhanced Flowability and Slurry Characteristics of Limestone-water Suspensions Through the Integration of Coarse Particles and a Natural Additive

Mineral slurry preparation and pipeline transport require careful particle size distribution and additive selection to ensure cost-effective and reliable transportation. The research described here was aimed to better understand the flow behavior of a limestone sample by combining coarse and fine particles and a low-cost natural additive, Saponin, derived from Sapindus laurifolia. Four distinct bi-modal suspension samples were formed using various mixtures of limestone samples with sizes varying from 0–53 and 75–106 µm. The rheological characteristics of the suspension were investigated at shear rates of 50 to 500 s−1 for solid concentrations 40–70% by weight. The additive’s critical micelle concentration was found to be 1.8 weight percent. The Hershel-Bulkley model fits the experimental data the best. The appropriate proportion of coarse particles was discovered to be 30% based on critical factors such as apparent viscosity and pressure drop. The addition of the surfactant reduced the surface tension, increased the wettability, and decreased the particle-particle interaction to stabilize the limestone-water suspension.

Effects of Simulated Reclaimed Water on Soil Particle Sizes and Cd Adsorption and Migration in Soils at Smelting Sites.

This work studied the vertical migration characteristics of Cd in soil profiles from a zinc smelting site under the influence of simulated reclaimed water containing NaCl and Na2SO4. The isothermal adsorption curves of Cd in the soils of miscellaneous fill and weathered slate well fitted the Freundlich and Langmuir models, with R2 ranging from 0.991 to 0.998. The maximum adsorption capacity of Cd in the soils decreased significantly under the salt ion treatments with NaCl and Na2SO4. After leaching, the Cd concentrations in the leachates and Cd contents in the subsoil layers of 10-60cm followed the order NaCl treatment > Na2SO4 treatment > CK (p < 0.05), suggesting that the salt ions promoted the vertical migration of exogenous Cd. The proportion of coarse particles (> 0.02mm) decreased, while that of fine particles (< 0.02mm) increased under salt ion treatments (p < 0.05). The morphological characterization indicated that salt ions accelerated the erosion and fragmentation of coarse particles to form fine particles. The use of reclaimed water to flush smelting sites may increase the risk of Cd migration with small-sized soil particles from the soil to groundwater.

Non-linear response of sediment size characteristics and associated transport patterns to soil structural stability in sheet erosion under field rainfall simulation

Sediment transport patterns (suspension, saltation and rolling) not only depend on flow hydrodynamic characteristics, but also on sediment properties, both of which are largely influenced by soil structural stability. However, how sediment sizes and transport patterns response to original soils over a wide range of structural stability remains unclear. Herein, field plot rainfall simulation experiments on five soils along an increased gradient of structural stability were conducted at two rainfall intensities of 45 and 90 mm h−1 to investigate effective sediment size characteristics and associated transport patterns in sheet erosion. Differing from runoff and sediment yield, sediment sizes were most influenced by soil structural stability (F = 386.9) rather than rainfall intensity (F = 246.7, p < 0.001). Mean weight diameter of sediment (0.16–0.84 mm) and the proportion of coarse particles (>0.25 mm) exhibited a unimodal variation with increased soil structural stability. The effective sediment size distribution shifted from unimodal with the peak at < 0.10 mm for low and high stable soils to bimodal with two peaks at < 0.10 mm and 0.5–1 mm for medium stable soils. Correspondingly, suspension-saltation (>74 %) dominated sediment transport for low and high stable soils, which was determined by fine sized fragments from aggregate breakdown and small flow transport capacity, respectively; while both suspension-saltation (<0.10 mm) and rolling (>0.25 mm) jointly contributed to sediment transport for medium stable soils, which was controlled by the interaction between fragment size and flow transport capacity. Moreover, the positive effect of rainfall intensity on sediment sizes was more remarkable for the medium than for the low and high stable soils. A conceptual model of sediment transport mechanisms in response to soil structural stability is firstly proposed, which merits consideration in the future development of erosion modeling and soil conservation techniques.

New powder metallurgy preparation method of homogeneous and isomeric Al−Cu−Mg mixed crystal materials

A new idea of homogeneity isomerism is proposed in this work to break through the single restriction that traditional homogeneous powder metallurgy materials take refining particles as the only modification method. AA2024 alloy powders of different diameters are mixed in a certain proportion through low-energy ball milling, and then a kind of mixed crystal material is successfully fabricated by hot pressing sintering. The results show that the grain morphology of the traditional sample sintered with single-diameter particles tends to become irregular polygon shape, while the grain morphology of the mixed crystal materials forms a special structure in which larger grains are coated with smaller grains. Compared with the former, when the proportion of coarse particles is 20% (mass fraction), the tensile strength increases by 38.8%; when the proportion of coarse particles is 50%, the elongation increases by 14%. The mixed crystal material exhibits a mixed fracture mechanism of intergranular fracture and transgranular fracture, and the pinning effect of the second phase on the dislocation is more obvious, so the properties of the alloy are improved significantly. The above research provides a new idea for the preparation of high-performance homogeneous isomeric mixed crystal materials.

Soil erodibility after the removal of wood chip mulch: A wind tunnel experiment

Numerous field studies have investigated the effects of mulching on soil wind erosion. However, little is known about the changes in soil erodibility after removing the mulch layer. In this paper, we measured the physicochemical properties and aggregate characteristics of soil from an urban park after removing the mulch layer and estimated wind-erodible materials emission by wind tunnel experiments. Wood chips at 4,500 g m⁻² (mulch thickness of 5 cm, R5), 6,300 g m⁻² (mulch thickness of 7 cm, R7), and 8,100 g m⁻² (mulch thickness of 9 cm, R9) were used for mulching an area in Yuanmingyuan Park from October of 2019 to the end of February of 2021. The following four treatments were listed: unmulched soil (CK), R5, R7, and R9. Compared with CK, the soil moisture content (SM), the macro-aggregates (&gt;0.25 mm) ratio (M &gt; 0.25), the wind erodible fraction (WEF), and the dry aggregate stability (DAS) of R5, R7, and R9 were significantly increased after mulching (<i>P</i> &lt; 0.05), whereas the soil organic matter content (SOM) was only slightly increased. The calcium carbonate contents (CaCO₃) varied greatly among the different treatments. Based on the wind tunnel experiments, the distribution of wind erosion materials near the soil surface (0 to 30 cm) was fitted to logarithmic, power, and exponential functions (<i>R</i>² ranged between 0.7179 and 0.9859). The particle size distribution of all wind-erodible materials was unimodal, and the proportion of coarse particles (250 to 100 μm) was highest. Compared with the CK, the average wind erosion rate (AWER) of R5, R7, and R9 was decreased by 48.44%, 65.04%, and 70.03%, respectively, after mulching. The AWER was significantly (<i>P</i> &lt; 0.01) negatively correlated with SM, M &gt; 0.25, WEF, and DAS, and negatively correlated with CaCO₃ and SOM. The CaCO₃ was significantly (<i>P</i> &lt; 0.05) positively correlated with M &gt; 0.25, WEF, and DAS. Overall, despite the relatively short mulching period (16 months), wood chip mulch improved the physicochemical properties and aggregate characteristics of soil and decreased erodibility.

The Preparation of High-Volume Fraction SiC/Al Composites with High Thermal Conductivity by Vacuum Pressure Infiltration

The high-volume fraction SiC/Al composite is the new type of electronic packaging material, which plays an important role in the field of high-power integrated circuits. In this study, SiC/Al composites with high-volume fraction of SiC particles were prepared by vacuum pressure infiltration. The influence of SiC particle size and NH4HCO3 on the pores in the preform was explored, aiming to accurately adjust the volume fraction of SiC to meet the thermal performance requirements in different fields. In addition, the preform was infiltrated with different Al alloys, and the relationship between the porosity and thermal conductivity of SiC/Al was studied. For the SiC preform, the volume fraction of SiC can be adjusted regularly when 12 μm and 100 μm SiC particles are mixed in different proportions, and the volume fraction reaches the maximum when the proportion of coarse particles is about 77%. NH4HCO3 is conducive to the connectivity of pores in the preform, and about 40 vol.% of NH4HCO3 can effectively increase the porosity of the preform. Thermal conductivity is sensitive to the porosity of composites, especially in the range of 2.5–4.5%. A simple application of the Hasselman–Johnson model and a new thermal conductivity model, λd, established in this article, offer a good agreement with the experimental results.

Evolution Mechanism of Water-Conducting Channel of Collapse Column in Karst Mining Area of Southwest China

There are many karst collapse columns in coal seam roof in the southern coal field in China, which are different from those in coal seam floor in the northern coal field, due to the stratum characteristics. The karst collapse column in coal seam roof tends to reactivate and conduct water and induce the serious water inrush disaster, when the karst collapse column communicates with the overlying aquifer. In order to reveal the evolution mechanism of water-conducting channel of collapse column in karst mining area of southwest China, the aquifers and water inflow rule in 1908 working face in Qianjin coal mine are analyzed. Besides, the particle size distribution and mineral component of collapse column are researched by the X-ray diffraction test and the screening method, which are the basis for researching the water inrush mechanism in karst collapse column. On this basis, the water inrush of roof collapse column under the influence of mining is researched by establishing the numerical calculation model with the UDEC numerical software. The results show that the water flowing into the 1908 working face comes from the Changxing formation aquifer and Yulongshan formation aquifer above the coal seam, and the proportion of coarse particles and fine particles in collapse column is 89.86% and 10.14%, respectively. With the advance of working face, the water-conducting channel connected the working face with the aquifer, or the surface is formed by collapse pits, karst caves, and collapse column. The research results can be treated as an important basis for the water-preserved mining in southern coal field in China.

Effect of particle size distribution on rheological properties of chocolate.

This study focused on the influence of the particle size distribution (PSD) of ingredients used for chocolate preparation (cocoa powder and sugar) on viscosity of model chocolates with different fat contents. Model chocolates with varying PSDs and two particle size ratios (cocoa particles : sugar of 1 : 4 and 1 : 6) were prepared by mixing highly defatted cocoa powder as a fine fraction and sugar as coarse fraction in several proportions. Samples containing spherical quartz beads were included as a reference to gain insight into the role of particle properties. Comparing chocolate samples with the same composition, but different particle size ratio, the largest difference in viscosity was found at a proportion of coarse fraction of 0.6. This shows that at this proportion of coarse particles, the highest maximum packing fraction was reached, which is in accordance with theoretical predictions. However, for the investigated chocolate samples, the lowest viscosity values were obtained at a proportion of the coarse fraction of 0.8 or 1. This could be attributed to parameters other than PSD, such as a decrease in surface area with an increasing amount of coarse particles. Also the morphology and surface properties were shown to influence viscosity. Compared to cocoa and sugar particles, spherical and smooth quartz beads led to an improved particle packing, and therefore a lower viscosity. The addition of lecithin led to a decrease in viscosity due to a decrease in particle-particle interactions, particularly for hydrophilic sugar particles. The knowledge obtained in this study provides possible approaches on how to reduce fat content of chocolates.

Gradation and Rheological Characteristics of Glacial Debris Flow along the Kangding–Linzhi Section of Sichuan–Tibet Railway

To date, most research on the characteristics of glacial debris flow along the Sichuan–Tibet railway has focused on numerical simulations and remote sensing, resulting in a lack of direct experimental data from debris flow samples. Therefore, in the present study, a field investigation was conducted along the Sichuan–Tibet railway, and 55 samples of glacial debris flow deposits were systematically analyzed to determine their grading and rheological properties. This is the first systematic experimental study on glacial debris flow deposits. The results showed that the proportion of coarse particles was high and the proportion of fine particles was low in the glacial debris flow along the Sichuan–Tibet railway. The average gravel and sand contents were 37.8% and 58%, respectively, and the average contents of silt and clay were 3.7% and 0.47%, respectively. The average fractal dimension was 2.1507, which is much greater than that of viscous debris flow. Under the same gravity and shear rate, the stress of typical glacial debris flow was significantly less than that of viscous debris flow, whereas the variability of the stress was more significant. These findings will contribute to revealing the movement rules and disaster risk of glacier debris flow along the Sichuan–Tibet railway and have considerable theoretical and practical significance for ensuring safety during both its construction and later operation.

Lab Scale Vibrating Screen Study on Operational Variables that Affect the Separation Efficiency

Vibrating screening is an equipment of simple design and execution, but its full description may be difficult to predict, considering that several variables can influence it. This work evaluates the effects of the independent variables: proportion of particles larger than the screen aperture size, average feed rate and g-force on the separation efficiency of coarse particles in a lab scale vibrating screening, where the material to be screened was phosphate rock, with density of 3.25 g/cm3 and particle size range of 0.6–600 μm. For this, a central composite design (CCD) was applied to quantify the main effects of the variables. As a result, the average feed rate was not relevant and the proportion of coarse particles and the g-force contributed positively to the increase of the efficiency. The point where the variables have their highest values, the maximum experimental efficiency was observed (94.93%).

Patterns of species richness and abundance among cactus communities receiving different rainfall levels in the semiarid region of Brazil

This study examines the variation in cacti species richness and abundance among sites with different average rainfall and soil types. We assessed a total of 3,660 individuals of six species of Cactaceae: Cereus jamacaru, Melocactus zehntneri, Pilosocereus gounellei, Pilosocereus pachycladus, Tacinga inamoena, and Tacinga palmadora. The greatest species richness and abundance of cacti were at locations with low rainfall and more clayey soils. The species studied differed in multidimensional representation, with some species being more positively related to soils with a higher proportion of fine particles (M. zehntneri and P. gounellei), while others were negatively related to soils with a higher proportion of coarser particles (T. inamoena) or positively related to areas with higher rainfall and vegetation cover (C. jamacaru and P. pachycladus). The differential responses of the species of Cactaceae studied in relation to the gradients analyzed demonstrates the need for more research into the relationship between cacti and environmental variables in semiarid ecosystems with high environmental heterogeneity.

Analysis of the Influence Factors on High Compressibility Water Atomized Iron Powder

In this paper, the influence factors on high compressibility water atomized iron powder LAP100.29 were studied such as the processing parameters, the proportion of coarse particles, powder oxygen content and impurity. The results showed that, by increasing the purity of molten steel and improving atomization temperature, the iron content of water atomized iron powder particles reached more than 99.67 %, the oxygen content was less than 0.08 %, acid insoluble was less than 0.08 %, green density reached 7.21~7.22 g/cm3. The contents of +80 and -80～+100 mesh powder were 1.6 % and 7.5 %, respectively. The compressibility could be improved by the increase of the coarse particles and the reduction of the fine particles (for example, lowering the content of -325 mesh particles). Generally speaking, the compressibility of the water atomized iron powder can be improved fundamentally by reducing oxygen content, impurity content and the reasonable distribution of particle size.

Influence of habitat structure and environmental regime on spatial distribution patterns of macroinvertebrate assemblages associated with seagrass beds in a southern Gulf of Mexico coastal lagoon

Seagrass meadows are important for their ecological functions and ecosystem services, including habitat and shelter for a high diversity of species. The present study aims to assess the spatial distribution patterns of macroinvertebrate assemblages associated with Thalassia testudinum beds in a tropical coastal lagoon of the southern Gulf of Mexico. Environmental variables and core samples were taken from three shallow beds with different degrees of exposure to wind-driven waves: protected, exposed and semi-exposed. A total of 40 benthic macroinvertebrate species were recorded, molluscs being the most important group in terms of diversity and abundance. The highest species richness was recorded at the semi-exposed site (31 species), while the highest abundance was at the exposed site (5207 ind. m−2). Despite inter-site variations in environmental variables and physical descriptors of seagrass (seagrass biomass, shoot density, leaf length), the species richness and abundance of macroinvertebrates correlated only with seagrass biomass. Multivariate analyses showed a clear separation of macroinvertebrate assemblages into two main groups according to the degree of exposure of the sites as exposed/semi-exposed or protected. It was also determined that seagrass biomass, hydrodynamism, sedimentation/resuspension rates and the proportion of coarse particles in the sediment appear to be the variables that best explain the differences between sites. These findings support the importance of including sites with different degrees of exposure in assessing the biodiversity of seagrass beds at the landscape scale, because species composition, species richness and the abundance of associated fauna may vary considerably between sites within the same coastal region according to a combination of biotic and abiotic factors.

Influence of prepelleting inclusion of whole corn on performance, nutrient utilization, digestive tract measurements, and cecal microbiota of young broilers

The objective of the present study was to examine the effects of prepelleting inclusion of graded levels of whole corn on performance, digestive tract measurements, nutrient utilization, and cecal microbiota in broiler starters. Five diets, containing 600 g/kg of ground corn or 150, 300, 450, and 600 g/kg of whole corn replacing (wt/wt) ground corn, were formulated and cold-pelleted at 65°C. Each diet was offered ad libitum to 6 replicates (8 birds per replicate cage) from d 1 to 21 posthatch. The proportion of coarse particles (>1 mm) increased with increasing prepelleting inclusion of whole corn. Pellet quality, measured as pellet durability index, increased (quadratic effect, P < 0.001) with the inclusion of whole corn to 450 g/kg and then plateaued. Weight gain and feed intake decreased (linear effect, P < 0.001) with increasing prepelleting inclusion of whole corn. Feed per gain (quadratic effect, P < 0.05) increased as the inclusion level of whole corn increased to 300 g/kg and then plateaued with further inclusions. Relative gizzard weight (quadratic effect, P < 0.05) increased with increasing inclusion of whole corn up to 300 g/kg and then levelled off. The AME (quadratic effect, P < 0.05) increased up to 300 g/kg of whole corn inclusion and then decreased with further inclusion. Apparent ileal digestibility of DM (P < 0.001), N (linear effect, P = 0.07), and starch (linear effect, P < 0.001) increased with increasing inclusion levels of whole corn. Based on the fluorescence in situ hybridization method, a linear (P < 0.05) effect was determined for cecal microbiota numbers. Lactobacillus spp. counts increased and counts of Clostridium spp., Campylobacterium spp., and Bacteroides spp. decreased with increasing inclusion levels of whole corn. The present data showed that, despite increased gizzard weight and nutrient utilization, weight gain of broilers was poorer with prepelleting inclusion of whole corn due to reductions in the feed intake.

Effect of feeding diets based on coarse maize on productive performance, gizzard development and energy utilisation of laying hens

1. A total of 2200 White Leghorn layers were used to study the effect of feeding coarse maize on productive performance, gizzard weight, apparent metabolisable energy (AME) and egg quality parameters.2. The experiment was a completely randomised design with 5 treatments, each being replicated 5 times (88 birds per replicate). Dietary treatments included a control diet with 600 g/kg of ground maize (6 mm sieve) and experimental diets with 150, 300, 450 or 600 g/kg coarse maize (10 mm sieve) replacing (w/w) ground maize. Diets, in mash form, were offered from 39 to 62 weeks of age.3. Over the entire experimental period, dietary treatments had no effect on any of the production parameters, except on feed intake. A quadratic effect was observed for feed intake, where intake increased at 150 g/kg coarse maize inclusion. At higher inclusion levels of coarse maize, feed intake was similar to that of the control diet. But the differences in daily intake between dietary treatments were only around 1 g/bird and may not be of any biological significance.4. Dietary treatments had no effect on gizzard weight, AME or egg quality.5. The results indicate that coarse maize could completely replace maize in layer diets with no adverse effect on egg production, egg quality and dietary energy utilisation. In the current work, although the proportion of coarse particles (over 1 mm) increased with increasing inclusion levels of coarse maize, the differences in the percentage of particles above 1 mm between the fine control (0 g/kg coarse maize) and coarsest (600 g/kg coarse maize) diets was only 15%, and this may limit the value of the findings reported herein.

Influence of Feed Particle Size on the Performance, Energy Utilization, Digestive Tract Development, and Digesta Parameters of Broiler Starters Fed Wheat- and Corn-Based Diets

The influence of particle size and grain type on the performance, AMEn, and on gross morphological and histological parameters of the various segments of the digestive tract of broilers fed wheat- or corn-based diets was investigated. The experimental design was a 2 × 2 factorial arrangement of treatments evaluating 2 particle sizes (fine and coarse) and 2 grain types (wheat and corn). The 2 particle sizes were achieved by grinding the whole grains in a hammer mill to pass through 1-mm and 7-mm screen sizes. Broiler starter diets, based on wheat- or corn-soybean meal, were formulated, pelleted, and each diet was offered to 6 cages of 8 male broilers each from d 1 to 21 posthatching. The results showed that the differences in particle size distribution still existed between diets after pelleting especially in the proportion of coarse particles (1 mm and over). In corn-based diets, coarse grinding improved (P = 0.06) weight gains compared with fine grinding, but this particle size effect was not observed in wheat-based diets. In both diets, coarse grinding lowered (P < 0.001) feed per gain of broilers compared with fine grinding. In wheat-based diets, coarse grinding improved (P = 0.06) AMEn compared with fine grinding. Heavier (P < 0.05) gizzard weights were observed in birds fed the coarse corn-based diet, but particle size had no effect on the gizzard size in birds fed wheat-based diets. Villus height, crypt depth, and epithelial thickness in the duodenum were unaffected (P > 0.05) by particle size and grain type. Overall, the present results showed that the effect of feed particle size varies depending on grain type.

Relationship between ruminal starch degradation and the physical characteristics of corn grain.

The objectives of this study were to determine the range of variation in the rate and extent of in situ ruminal starch degradation of 14 corns differing in vitreousness and to predict ruminal starch degradability by physical characteristics of corn grains. This study was conducted with eight dent and six flint corns. Ruminal starch degradability was determined by an in situ technique on 3-mm ground grains. Physical characteristics of corn grain were measured: hardness by grinding energy and particle size distribution, apparent and true densities, and specific surface area. Ruminal DM and starch degradabilities averaged 50 and 55.1% and varied from 39.7 to 71.5% and from 40.6 to 77.6%, respectively. Ruminal starch degradability averaged 61.9 and 46.2% in dent and flint types, respectively. The proportion of coarse particles (61.9 vs. 69.6% for dent and flint, respectively), the apparent density (1.29 vs. 1.36 g/cm3 for dent and flint, respectively), and the specific surface area (.13 vs. .07 m2/g for dent and flint, respectively) varied with the vitreousness. Ruminal starch degradability could be predicted accurately by vitreousness (r2 = .89) or by the combination of apparent density and 1,000-grain weight (R2 = .91), a measurement faster than the vitreousness determination.

97/03978 Retrofits and its effects on burner, i.e. boiler performance

To convert existing coal-dust-fired steam boilers to LOW-NOx combustion, pulverized fuels with a favorable granulometry are required. Such ground products cannot be attained with the static classifying systems currently in use, as the proportion of coarse particles is too high. This results in an increased proportion of unburned matter in the flue ash and can lead to a decrease in efficiency. Rotary classifiers meet the particle size distribution quality requirements, whereby the proportion of coarse grains is substantially reduced compared with static classifiers. For meeting high requirements, the LOESCHE rotary classifier, model LKS, is available. To fulfill the very highest requirements, the LOESCHE high-efficiency classifier, model LKDKS, with static preliminary classification and dynamic reclassification, is recommended. The classifier designs are described.

Influence of grazing and soil conditions on secondary savanna vegetation in India

Abstract. Savanna vegetation and pertinent soil features were studied on 43 sites in a dry tropical forest region of India. Grazing intensity ranged from 0.68 to 0.98. Soil moisture was positively related to the proportion of fine soil particles (&lt; 0.1 mm), and the latter decreased while the proportion of coarse particles (2.0‐0.5 mm) increased with increasing grazing intensity. Canopy biomass ranged from 28 to 104 g/m2 in grazed communities and from 230 to 337 g /m2 in ungrazed communities and was positively related to vegetation cover which ranged between 30–72 % in grazed and 68 ‐ 91 % in ungrazed communities. Vegetation cover was negatively related to grazing intensity. Species richness and diversity were highest at low grazing intensity. Using community coefficients and Detrended Correspondence Analysis, the grazed stands were clustered into six and the ungrazed ones into three communities.The grazed communities were recognised as degradation stages and the ungrazed ones as recovery stages. Only five grass species, in various combinations were able to dominate in one of the different stages. Evidently the harsh climatic conditions (high temperatures, high variability in rainfall and a long dry period) in the region permit only a few species already adapted to these conditions to participate in the succession.