In the late nineteenth century Anne and Wilfrid Blunt described horse-shoe shaped hollows they called fuljis in dunes in the Nafud sandsea of Nejd in Arabia. Since then the term has been sparsely used but investigators have tended to associate these features with coalescing barchans. Examination of images from Google Earth, however, have shown that such hollows are associated with quite a large range of other dune types including star dunes, parabolics, network dunes, and mega-barchanoid ridges. The paper concludes with the suggestion that the term is superfluous, and that such rather neglected features, which deserve further investigation, should simply be called ‘interdunal hollows’.
Soil enzyme activity is an indicator of microbial community and functions that reflects changes in soil biological properties, soil organic matter dynamic and nutrient cycling. Therefore, this study was conducted to investigate the enzyme activity in different sequences of biocrusts and loess soils in the semi-arid region of Incheh Borun, Golestan province, Iran. The Incheh Borun region has the highest abundance of biological crusts on loess plateau. Biocrusts were identified based on morphological characteristics. Enzyme activity was measured (cellulase, chitinase, α-glucosidase, β–glucosidase, acid phosphomonoestrase, arylsulfatase, β-xylosidase, butyrate esterase and leucine aminopeptidase) in the presence of cyanobacteria, lichen and moss crusts and their absence (i.e., the physical crust) as affected by three treatments (crust, soil and soil + crust) and three replications at a depth of 0- 2 cm. The results showed that the presence of biocrusts compared to physical crust in the surface parts (0 to 2 cm depth) improved the activity of enzymes in all three treatments. The highest enzyme content was related to the β-glucosidase enzyme in the lichen biocrust, and the lowest content was observed in the β-xylosidase enzyme in the physical crust. The lichen crust (Diploschistes diacapsis (Ach.) Lumbsch) had the greatest enzyme activity compared to other crusts. This species can fix he carbon of atmosphere by photosynthesis and increasing soil stability better than the other biocrusts. The most enzyme activity in the presence of biological crusts indicates a more active biological diversity or microbial population compared to the physical crusts. This can improve soil quality.
The usage of sewage sludge in agriculture has increased the accumulation of some heavy metals (such as cadmium, copper, lead, etc.) in soil and plants, due to the high concentration of these elements. Therefore, this research was conducted to investigate the best method to reduce the toxicity of heavy metals in sewage sludge while causing less environmental pollution. This approach utilized NaOH and HCl, along with humic and fulvic acids, to precipitate heavy metals from sewage sludge complexed with heavy metals in sludge to reduce the concentration of heavy elements and produce liquid organic fertilizer. In this research, the concentration of heavy metals (As, Cd, Cu, Ni, Pb, and Zn) in the sewage sludge, humic, fulvic, and liquid organic fertilizer were measured. Also, the humic, fulvic, and the produced organic fertilizer were tested on corn plants in terms of two treatments (10%, and 20%) and the heavy metals of those were analyzed. All experiments were conducted in three replications. The results showed the values of heavy metals in the humic, fulvic and liquid organic fertilizer were lower than the acceptable contents of EPA. The content of these elements in corn plants treated with humic, fulvic, and liquid organic fertilizers were lower than the EPA standard. Therefore, this liquid organic fertilizer can be used as two concertation (10% and 20%) for plant nutrition and compared to chemical fertilizers, is not only economically cost-effective, but also does not have the pollution caused by the use of chemical fertilizers.
Iran's geographical location causes the majority of the country to be semi-arid, arid, or hyper-arid. The existence of ergs and dunefields in the central and eastern parts of Iran has caused residential areas and all kinds of land use to be affected by sand movement and dust risk. Despite this, there is no comprehensive research on ergs and dunefields in Iran. The aim of this study is to identify, classify, and monitor Iran's ergs and sand dunes, as well as their wind characteristics. We used 66 synoptic stations throughout the country, satellite images from the Ergs region (Landsat 8 and Google Earth), geological and topographical maps at scales of 1:100000, 1:250000, and 1:50000, a digital elevation model with 12.5 meter resolution, and data from field work to achieve our objectives. In addition, using different software, classification of sand dunes, wind erosion potential, and descriptive and analytic maps were prepared. According to the findings, the total area of ergs and dunefields in Iran covered approximately 2.9 percent of the country. Sand dunes come in a variety of shapes and sizes, due to climate and geomorphological diversity in different parts of Iran. Also sand dunes in the south-east of Iran have migrated at a rate of more than 18 meters per year over the last 16 years. The results of the correlation between sand dunes movement and wind characteristics show a close direct correlation, so that sand dunes have the most displacement in areas with high wind velocity and Total Drift Potential (DPt), but have low displacement in other areas due to sand dunes stabilization with vegetation and topographic obstacle.
Soil water repellency (SWR) is a widespread natural phenomenon that results from a complex interplay between the hydrosphere, lithosphere, biosphere, atmosphere, and anthroposphere. Sewage sludge application can induce soil water repellency (SWR), impacting soil hydraulic properties. This research examined the effect of soil microbial manipulation (removal and addition) on SWR and water retention in a silty-clay-loam soil amended with varying sludge amounts. Three levels of water repellency (zero, weak and strong) were artificially created in a silty clay loam soil by adding urban sewage sludge. The results showed that the elimination of soil microorganisms such as fungi and bacteria and their interactions significantly (P≤0.01) affect the hydrophobicity, soil water retention curve (both wetting and drying) of the sludge-treated soils. Microbial exclusion significantly reduced SWR (21-49%), suggesting that microbial activity contributes to the formation of hydrophobic compounds. Conversely, microbial inoculation increased SWR (27.5-50%), indicating microbial production or transformation of hydrophobic substances. It is concluded that soil microorganisms can increase soil water repellency. Also, soil microorganisms can affect the soil water retention curve through their influence on soil water holding capacity, depending on microbial diversity. These findings highlight the critical influence of microbial activity on SWR and water holding capacity in sludge-treated soils.
