The Otindag sandland, located at the boundary of the East Asian monsoon area, is sensitive to climate change and is therefore an ideal place to investigate past environmental evolution. Due to frequent volcanic eruptions that have occurred since the Cenozoic, numerous interbeds of multi-stage basalt and sand exist in the stratigraphic sequence, which allowed older sand to be preserved due to the protective effect of the overlying rock. Previous studies of climate change in the sandland mainly focused on the time interval since the last glacial period, and information is lacking regarding climate change over longer timescales and younger volcanic activity. The key reason for this is that suitable geological carriers are rare, which prevents the expansion of the desired sediment chronological scale. In order to establish the chronological framework, samples of the sandy paleosoil, aeolian sand, lacustrine sand and volcanic baked layer were collected and dated by the optically stimulated luminescence (OSL) method. The conventional SAR, TT-OSL and pIRIR((200,290)) procedures were used to obtain equivalent doses of quartz and feldspar. To ensure the accuracy of the dating data, the age of the feldspar dating of the oldest aeolian sand sample (TBB) was compared with the quartz result, and the quartz and feldspar ages were found to be consistent with each other within the error range. Considering the error of the age measured by TT-OSL (384.2 +/- 68.0 ka) exceeded 10%, the age measured by the pIRIR((200,290)) method (321.2 +/- 11.5 ka) was adopted to represent the deposition age of the aeolian sand sample. In addition, the age of the oldest sand deposition in the three sections of the Otindag sandland may reach 300 ka, mainly due to the different thermal history and provenance from other areas such as Loess Plateau, resulting in the different saturation dose and dose rate lever of quartz or feldspar. The sedimentary age framework established by OSL dating enabled the reconstruction of the evolution process of the Otindag Sandland. The climate was cold and dry during the periods corresponding to 321.2, 160.3-151.6 and 4.4 ka, and the aeolian sand material quickly accumulated during these times, as dunes were activated and the sandland expanded. During the periods corresponding to 5.0 ka and 2.4-1.3 ka, sandy soil developed efficiently, implying the dunes were fixed. The oldest lacustrian sand age is 320.4 +/- 16.0 ka for quartz dated by the SAR method. Hence, aeolian sand and lacustrine sand developed in the same period, which indicates that there was a landscape where dunes and lakes coexisted around 320.4 ka, such as at present. The Optical Stimulated Luminescence dating results of the volcanic baking layer and the underlying coarse sand layer confirm that volcanic activity occurred around 321.2 and 155.0 ka. Combined with results of previous research, this study indicates that the northeast and northwestward basement faults of the northern margin of the North China Craton and the Central Asian orogenic belt are characterized by extensional tectonic properties in the background setting of plate subduction, and relative uplift and settlement occur in the sandland formation zone.

Groundwater is the key factor of determining the growth of vegetation. Identifying the characteristics of groundwater is an important basis to formulate a management plan for water resources and develop the technology of controlling desertification in arid areas scientifically. It is also important to the environmental protection in China. Ground penetrating radar (GPR) signals produce a special response to the changes in water content during propagation, thus it is essential to study the propagation of electromagnetic pulse in aeolian sand with different water content. The GPR tests of aeolian sand samples with different water content were conducted by a GPR system, dielectric constant meter, and conductivity meter. The temporal and frequency spectral characteristics of electromagnetic signals measured from aeolian sand samples were analyzed. The results show that the dielectric constant and conductivity of aeolian sand increase nonlinearly as the water content increases, and the attenuation coefficient of electromagnetic pulses increases parabolically. Meanwhile, the temporal waveform fluctuates significantly at the boundary of different media, and its two-way travel time increases nonlinearly as the water content increases, the pulse velocity decreases nonlinearly. Furthermore, the peak frequency of the spectrum for a signal propagating through aeolian sand decreases as the water content increases. The peak frequency is concentrated in the 1000 to 1400 MHz range, but the shape and bandwidth of the spectrum are less affected by water content.The abovementioned correlations can provide a water content estimation of aeolian sand with direct value to the local authorities which are involved in the decision-making process for effective water management in arid and semi-arid area.

The evaluation of aeolian desertification of sand dunes in north Assuit, Middle Egypt, has been achieved throughout a variety of detailed field investigations and laboratory measurements. The study area lies in hot dry desert climatic conditions where the sand dunes migration represents an effective threat cultivated lands, reclaimed lands, asphaltic roads and the systems of human distribution. Its mean annual rainfall is about 51 mm. Except the Nile Valley, Egypt is mostly considered as dry desert lands so about 4% of its surface area is under plough. The study barchans are mainly composed of poorly graded sands and consist of fine sand, medium sand and a negligible amount of coarse sand, silts and clays. Compositionally, the studied sand dunes are mainly consist of quartz, rock fragments and negligible amounts of feldspars with the absence of any chemically active constitutes (e.g. chert, flint, chalcedony and dolomite). These sands are also free of organic matter. The removal of dune sands in hazardous sites considers a short-term solution method of the aeolian desertification problem.

Sandy soils cover approximately 900 million ha worldwide particularly in arid and semi-arid regions. There are extensive areas of sandy soils under cultivation, but the soil fertility is often low and dependent on the levels of soil organic carbon (SOC). Here, we review SOC levels of sandy soils across the world using pedon databases, data from literature, and three detailed case studies. Pedons were selected from five major databases and the pedons had a minimum of 850g sand kg(-1) in the top 30cm. Sandy soils occur in all climates and several soil orders (mainly Alfisols, Entisols, Inceptisols, Spodosols, Ultisols). Soil organic carbon was highest in sandy soils of the temperate and cold zones (mean 19gkg(-1)), and lowest in soils of the arid zone (<5g kg(-1)). The SOC concentrations was highest when mean annual precipitation was between 700 and 1300mm, and SOC was lower when annual temperatures were higher. Sandy soils under forest had on average 23g SOC kg(-1) whereas the soils under prairie had on average 7g SOC kg(-1). Spodosols had the highest SOC concentrations, and SOC was lowest in Aridisols. The average A-horizon thickness of sandy soils was 17cm, and it was thickest in Mollisols, and thinnest in Inceptisols. The thickness of the A-horizon is important since most of the SOC of sandy soils is found in the A-horizon. Over 32,000 papers have been published on sandy soils since 1914, and in the past 10 years, some 1000-1800 papers are annually published on sandy soils. We extracted papers since the early 1990s, and grouped them by continent, land cover, soil order, and focus of the research. Three soil-forming processes have been extensively studied in relation to SOC and sandy soils: podzolization, humification, and melanization. Several studies found that SOC increases when sandy soils were fertilized, but sandy soils become more water repellent with an increase in SOC and a decrease in pH. From published literature, it was found that SOC was high in sandy soils under forest (<= 90g kg(-1)) and grassland (<= 187gk(-1)), and low in sandy soils under agriculture (<= 38g kg(-1)) or under shrub (<= 36gkg(-1)). Lastly, we present case studies from Southern Africa, Western Europe, and North America. Sandy soils cover about 273 million ha in Africa, and SOC rarely exceeds 10g SOC kg(-1) in the top 30cm. The plaggen soils of Western Europe have high SOC (up to 66g kg(-1)) due to the long-term additions of sod, litter, manure, and sea sand to increase the soil fertility. In the Wisconsin Central Sand Plains, SOC stocks in soils under agriculture were high (60Mg ha(-1)) compared to the soils under forest (15Mg ha(-1)) and grassland (25Mg ha(-1)). Available water capacity increased with an increase in SOC. From this review, we conclude that sandy soils are found throughout the world, and the sandy soils in the temperate and cold zones have the highest SOC levels. In sandy soils, soil organic carbon increased the cation exchange capacity and lowered the bulk density. Soil organic carbon levels can be significantly increased in sandy soils under agriculture when amendments are made in combination with irrigation.

In Romania, the afforestation projects of degraded terrains are carried out in accordance with the technical norms issued by the ministry responsible for forest management. According to recent statistics, across the country there is a significant area of different types of degraded lands, more than 0.4 million hectares being affected by wind erosion. The goal of this study was to highlight the best afforestation alternative for the sandy soils across Oltenia and Carei Plains, corresponding to ecological group number 93 of the Technical Norms regarding the compositions, schemes and technologies for forest regeneration and afforestation of degraded lands. The best alternative resulted by using an Analytic Hierarchy Process, that took into account eight criteria. The combination between black locust and bird cherry proved to be the best choice. The significant area of sandy soils across Romania, but especially the lands from Oltenia and Carei Plains should be regarded rather as an opportunity to increase the forest fund through afforestation than a problem for the local communities and national economy.

Aeolian sand specialists are traditionally recognized among the most threatened species of central European landscapes due to habitat loss. In the present study, we examined the diversity of bees and wasps, and the cover and composition of vegetation in 17 neglected small fragments of Artemisio campestris-Corynephoretum canescentis acidophilous grasslands, which developed on weathered granodiorite rocks in the Czech Republic. The size of the examined fragments ranged from 128 to 14,000m(2), with a total area of only 5.7ha. At the examined sites, we identified species-rich assemblages of endangered aculeate hymenopterans that were previously thought to be specialized on aeolian sands. We found that despite the small area and relative isolation of the examined sites, they hosted 26 Red-Listed species of bees and wasps and a species new to Bohemia (Megachile pilicrus), respectively. The examined habitats also supported the presence of 18 Red-Listed receding field weeds and steppic grassland specialists. The analyzed bee and wasp assemblages were characterized by their low dominance (1-Simpson index=0.091) and high alpha diversity (Fisher's alpha=48.9). Although the examined fragments of acidophilous steppic grasslands differed in size by two orders of magnitude, the total abundance and species richness of the bees and wasps were not correlated with the size of the fragments. This suggests the long-term stability despite the minute size of some of the residual fragments. Land protection and active management are proposed to conserve these habitats for future generations.

The reasons for the hysteresis of the soil water-retention capacity are indicated. An explanation of the closed loop, which is formed by the main drying and wetting branches, as well as open loops, which are formed with the participation of scanning hysteresis branches is proposed. The problem of the possible manifestation of an undesirable pump effect is analyzed, and a way to solve this problem is indicated. Mathematical models describing this phenomenon are presented. In these models, three functions of water-retention capacity of the soil are used: (i) Van Genuchten's function, (ii) improved Kosugi function, (iii) improved Haverkamp and co-authors function. A physical interpretation of an additional additive parameter in the improved functions of the soil water-retention capacity is proposed. The prospects for the use of hysteresis models for calculating precision irrigation rates in land reclamation agriculture are characterized. Using the Williams-Kloot criterion, a comparative analysis of the presented hysteresis models was carried out with respect to the error of the point approximation of experimental data on the main branches (parameter identification), as well as with respect to the error in estimation of the scanning branches of water-retention capacity of the soil using the example of Dune Sand.

The moisture content w(s) of a beach surface strongly controls the availability of sand for aeolian transport. Our predictive capability of the spatiotemporal variability in w(s), which depends to a large extent on water table depth, is, however, limited. Here we show that water table fluctuations and surface moisture content observed during a 10-day period on a medium-grained (365 mu m) planar (1:30) beach can be predicted well with the nonlinear Boussinesq equation extended to include run-up infiltration and a soil-water retention curve under the assumption of hydrostatic equilibrium. On the intertidal part of the beach the water table is observed and predicted to continuously fall from the moment the beach surface emerges from the falling tide to just before it is submerged by the incoming tide. We find that on the lower 30% of the intertidal beach the water table remains within 0.1-0.2 m from the surface and that the sand is always saturated (w(s)approximate to 20%, by mass). Higher up on the intertidal beach, the surface can dry to about 5% when the water table has fallen to 0.4-0.5 m beneath the surface. Above the high-tide level the water table is always too deep (>0.5 m) to affect surface moisture and, without precipitation, the sand is dry (w(s) < 5 - 8%). Because the water table depth on the emerged part of the intertidal beach increases with time irrespective of whether the (ocean) tide falls or rises, we find no need to include hysteresis (wetting and drying) effects in the surface-moisture modelling. Model simulations suggest that at the present planar beach only the part well above mean sea level can dry sufficiently (w(s) < 10%) for sand to become available for aeolian transport. (c) 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.

Soil nitrogen is a key indicator of soil quality and plays a significant role for plant growth. Therefore, it is very important to study soil nitrogen distribution, especially in semi-arid area of western China. Fewer scholars paid attention to the effect on soil nitrogen due to coal mining in semi-arid mining areas of western China. In this paper, soil samples of different locations were tested in both the loess region and the aeolian sand region in the Daliuta mining area in Shaanxi Province. The impacts of mining subsidence on soil nitrogen were investigated. The soil nitrogen distributions between the loess region and the aeolian sand region were compared, and used the principal component analysis method to evaluate soil quality in semi-arid mining area. The results showed that the comprehensive score of soil quality in the loess region was as follows: the internal pulling stress zone (NLS) > the external pulling stress zone (WLS) > the compressive stress zone (YS) > the neutral zone (ZX). The content of soil total nitrogen in YS-zone was the lowest in the loess region. The loss of nitrogen increased with time in the mining area, in which the total nitrogen loss at the depth of 0-15 cm was 0.27 g/kg, and the alkaline nitrogen loss at the depth of 0-15 cm was 1.08 mg/kg. In the aeolian sand region, the comprehensive score of soil quality was as follows: WLS > FC (the non-mining zone) > ZX > NLS > YS. The amount of soil nitrogen content in the loess region was larger than that in the aeolian sand region. It was found that for the loess region, the relationship between total nitrogen and nitrate nitrogen showed a significant positive correlation. It was also a significant positive correlation between ammonium nitrogen and alkaline nitrogen. In the aeolian sand region, there was a significant positive correlation between total nitrogen and alkaline nitrogen. There was no significant correlation among other nitrogen forms.

Under a background of a significantly warming climate, current aeolian desertification in China's northeastern Tibetan Plateau (NETP) has been widely studied, but disagreements related to its causes continue to persist. In order to understand the present through the past, this study determined the various phases of aeolian desertification in the NEW based on the statistical analysis of 40 optically stimulated luminescence (OSL) aeolian sand dates from 23 aeolian sections. Because the redistribution of aeolian sand by wind processes can reduce the number of older sand dates, this research only affects exactly the past millennium. Following this, we analyzed the relationships between aeolian desertification phases in conjunction with reconstructed climatic data. Results revealed three distinct aeolian desertification phases that approximately correspond to 1480 CE, 1680 CE, and 1800 CE, respectively. By comparing these dates to well-established paleoclimate records, we determined that these three aeolian desertification phases all occurred under a cold and dry climate background. Accordingly, aeolian desertification in the NEW today under its current warm and wet climate background can therefore be attributable to irrational human activities rather than rising temperatures. Accordingly, we can infer that under the current warmer and wetter climate background, aeolian desertification in the NEW today can be reversed as long as human activities remain moderate, even without the implementation of artificial revegetation initiatives.