Soil Wind Erosion Research Articles

Spatial and temporal evolution of soil wind erosion in the Beijing-Tianjin sandstorm sources

<p indent="0mm">Dust emissions due to soil wind erosion and its transport are the most important natural sources of inhalable particulate matter in the atmospheric environment of sandstorm sources and the regions where sandstorms occur. To control the impact of dust emissions caused by soil wind erosion on the atmospheric environment in the Beijing-Tianjin resources, the Chinese government implemented a strategic significance ecological governance project in the Beijing-Tianjin sandstorm sources at the beginning of this century. However, there is still much controversy about soil wind erosion in the Beijing-Tianjin sandstorm sources and the resulting dust emissions. Based on field surveys, laboratory tests, remote sensing images and meteorological data, this paper calculated soil wind erosion in the Beijing-Tianjin sandstorm sources under three conditions, including the typical years of 2000, 2005, 2010, and 2015, land-use change conditions (land use in 2000, 2005, 2010, and 2015 but other factors with 2015), and climate change conditions (land use in 2015 but other factors with 2000, 2005, 2010, and 2015), by using the specified soil wind erosion model in the National Plan for Dynamic Monitoring of Soil and Water Loss from 2018 to 2022 and the Technical Regulations for Dynamic Monitoring of Regional Soil and Water Loss (Trial Version). In 2000, 2005, 2010, and 2015, the fluctuation in wind erosion modulus in the Beijing-Tianjin sandstorm sources decreased. Wind erosion modulus gradually decreased from northwest to southeast, and the value in desert or sandy land was higher than that in the surrounding areas. With the advancement of governance projects in the Beijing-Tianjin sandstorm sources, the distribution of wind erosion modulus changed significantly. Wind erosion modulus in the desert steppe was the largest and was approximately 2.67–2.98 times that of the Beijing-Tianjin sandstorm sources. Wind erosion modulus in the Hetao Plain and Hunshandake Sandy Land, were roughly the same as that in the Beijing-Tianjin sandstorm sources. Wind erosion modulus in other subregions was 42.69% of that in the Beijing-Tianjin sandstorm sources. Wind erosion area and variability in the above years in the Beijing-Tianjin sandstorm sources were <sc>385800–464500 km²</sc> and −9.35%–9.14%, respectively. The area of ​​mild and moderate wind erosion accounted for 91.56%. Overall, wind erosion area in the northwestern Beijing-Tianjin sandstorm sources was large, and its area proportion was high, followed by that in the middle area, and the southeast area had the smallest area. The wind erosion area in ​​desert steppe accounted for the largest proportion, with a value of 25.88%, and that in the southern part of the Greater Khingan Mountains was only 3.18%. Intense and extremely intense soil wind erosion was concentrated in the desert steppe and the western part of the Hetao Plain. Intense soil wind erosion was mainly distributed in the Kubuqi Desert and Hunshandake Sandy Land. Moderate and mild erosion involved each subregion in the Beijing-Tianjin sandstorm sources. There were obvious differences in the changes in the wind erosion area and intensity in each subregion during 2000–2005, 2005–2010, and 2010–2015. Climate change and land-use change had important impacts on soil wind erosion in the Beijing-Tianjin sandstorm sources. The variability of the wind erosion modulus and the area affected by climate change was equivalent to the corresponding variability of the year but greater than the influence of land-use change. In addition, the area of wind erosion under land-use change generally decreased, especially from 2010 to 2015, which had a decrease of 4.10%, indicating that the Beijing-Tianjin sandstorm source control project played an important role. These results provide a scientific basis for the evaluation of the benefits of the Beijing-Tianjin sandstorm source control project and the optimization of its layout.

Calibração de parâmetros de simulação para a erosão eólica fluxo de gás sólido em duas fases em solos áridos e semiáridos

ABSTRACT To construct a coupled simulation model of soil wind erosion and two-phase flow in arid and semiarid regions, the proper contact parameters of the soil discrete element simulation model are obtained based on the angle of repose (AoR) calibration test. The coupled simulation model is established by combining computational fluid dynamics. The response value of the wind speed of sand initiation is used to verify the model’s accuracy. Due to the characteristics of arid and semiarid soils, this paper uses the Hertz-Mindlin with JKR contact model in EDEM software to calibrate the soil parameters based on soil physical tests and designs the Plackett-Burman, steepest climb, and Box-Behnken tests according to Design-Expert software to obtain the soil AoR second-order regression. With the AoR of 33.52° as the target, the best combination of parameters is obtained: soil-soil collision recovery of 0.64, soil-steel static friction coefficient of 0.31, JKR surface energy of 3.302 J m-2. Finally, by using calibrated parameters and the threshold wind velocity as the response value, the wind-sand air-solid two-phase flow test is conducted in ANSYS Fluent and EDEM, with the relative error between the starting wind speed recorded by the high-speed camera in the wind tunnel test and the threshold wind velocity shown in the simulation model calculated to be 8.7%, and the calibrated soil parameters met the requirements of the coupled simulation.

Determination of the threshold velocity of soil wind erosion using a wind tunnel and its prediction for calcareous soils of Iran

AbstractDetermination of the threshold velocity (TV) is a crucial step for wind erosion evaluation. Due to the difficulties of direct field measurements, pedotransfer functions (PTFs) and easily measurable soil properties could be used to save time and cost in predicting TV. Therefore, the present study was conducted to predict the TV using PTFs and to assess its influential parameters for calcareous soils of Fars Province, southern Iran. To this end, the TV was measured by a portable wind tunnel at 72 locations in different land uses and soil types across the study site. Various physicochemical and mechanical soil properties were used to develop six PTFs using multiple linear regression. Results showed that the TV varied from 3.0 m s−1 in poor rangelands to 12.83 m s−1 in saline lands. Soil surface shear strength (SS) with a correlation coefficient of 0.85 was the most influential parameter affecting the TV, followed by aggregate mean weight diameter (MWD). Results of the predictive models revealed that PTF 5, which was developed using SS and penetration resistance (PR;R2 = 0.86, RMSE = 0.85 m s−1), and PTF 6, which was developed using MWD and PR (R2 = 0.81, RMSE = 1.07 m s−1), had the highest performance for predicting the TV. PTF 5 was selected as the final model for predicting the TV since it only needed easily measurable soil properties without soil sample collection. We concluded that the use of PTFs could be an applicable alternative way to predict the TV, particularly at large scales.

Spatio-Temporal Evolution of Sandy Land and its Impact on Soil Wind Erosion in the Kubuqi Desert in Recent 30 Years

Continuous remote-sensing monitoring of sand in desert areas and the exploration of the spatio–temporal evolution characteristics of soil–wind erosion has an important scientific value for desertification prevention and ecological restoration. In this study, the Kubuqi Desert was selected as the study area, and the Landsat series satellite remote sensing data, supplemented by satellite remote sensing data such as GE images, SPOT-5, ZY-3, GF-1/2/6, etc., integrated object-oriented, decision tree, and auxiliary human–computer interaction interpretation methods, developed the Kubuqi Desert area dataset from 1990 to 2020, and established a soil erosion intensity database of the past 30 years based on the soil–wind erosion correction equation. The results show that the application of the training samples obtained by a high-score collaborative ground sampling to land use/cover classification in desert areas can effectively improve the efficiency of remote-sensing mapping of sand changes and the accuracy of change information identification, and the overall accuracy of the classification results is 95%. In general, the sandy area of the Kubuqi Desert area has decreased year by year, during which the mobile sand in the hinterland of the desert has expanded in a scattered distribution. The overall soil–wind erosion intensity showed a downward trend, especially since 2000; the ecological improvement trend after the implementation of desertification control projects is obvious. Changes in the sand type contributed the most to the reduction of soil–wind erosion intensity (contribution 81.14%), ecological restoration played a key role in reducing the soil–wind erosion intensity (contribution 14.42%), and the increase of forest and grass vegetation covers and agricultural oases played a positive role in solidifying the soil- and wind-proof sand fixation. The pattern of sandy land changes in desert areas is closely related to the national ecological civilization construction policy and the impact of climate change.

Spatial and temporal evolutions of vegetation coverage in the Tarim River Basin and their responses to phenology

Vegetation plays an important role in soil erosion, and its coverage as an important parameter appears in almost all soil erosion models, such as USLE (Universal Soil Loss Equation), RWEQ (Revised Wind Erosion Equation) and WEPS (Wind Erosion Prediction System) et al. In the past several decades, scientist have paid attention to photosynthetic vegetation coverage (PVC) based on Normalized Difference Vegetation Index (NDVI). However, in soil wind-eroded region, there is almost no PVC in the nongrowing season and is a large amount of nonphotosynthetic vegetation (NPVC) in the growing season. Because the effect of NPVC on soil erosion is the same as that of PVC, vegetation coverage (FVC) in soil erosion field would include PVC and NPVC. Based on field observation, NDVI and meteorological data et al., this paper studied temporal and spatial distribution of vegetation coverage in the Tarim River Basin, and its response to surface temperature (T) and rain (R). The main conclusions are as follows. (1) PVC based on NDVI, would result in an underestimation of FVC in the growing season with about 30%, which led to an overestimation of soil wind erosion with 12%, indicating great errors in the nongrowing season. (2) FVC had obvious region distributions. FVC with 10%∼40%, 40%∼70%, and>70% were distributed in the mountain of middle elevation and the edge of oasis, the cultivated of the oasis, and the alpine grass of the Kongque River Subbasin, respectively; FVC<10% was widely distributed. With increasing of FVC, its area proportion (y) decreased as an exponential function (y = 73.19e-0.038FVC). FVC in the Kongque River, Aksu River, and Weigan-Kuqa River subbasins was better than that in the Hotan River, Keriya River, Cheerchen River, and mainstream Tarim River subbasins. Since the restoration of the ecological environment in the Tarim River Basin in 2000, FVC of 0 ∼ 10% decreased, while that of 40%∼70% increased, and the other fluctuated. (3) There was a linear relationship (FVC = a1T + a2R + b, where a1, a2, and b were the fitting coefficients) among FVC, T, and R, although the coefficients would change in different subbasins or half-months.

MANAGEMENT MODELS OF AGRARIAN PRODUCTION TAKING INTO ACCOUNT NATURAL AND TECHNOGENIC IMPACTS ON THE ENVIRONMENT

It is proposed to take into account the damage from man-made and natural impacts in ecological and mathematical models for optimizing agricultural production by introducing coefficients of negative impact on the environment in the mathematical model. An algorithm for determining the coefficients of negative influence in conditions of incomplete information is proposed. These indicators characterize water and wind erosion of soils, land pollution and soil degradation as a result of the activities of agricultural producers. The formulation and solution of the problem of optimizing the production of agricultural products with an assessment of damage to nature in the conditions of economic activity and climatic phenomena are given. The developed linear programming model contains in the objective function and constraints the coefficients of negative influence in the form of interval estimates. An applied extreme problem was solved for two agricultural enterprises of Eastern Siberia. Its capabilities are shown for planning the production of agricultural products in conditions of minimizing damage to the external environment.

Theoretical Research of the Potato Harvester Lifting Plowshare to Reduce Yield Losses and Soil Erosion

Introduction. The potato harvester operation quality depends not only on the design features, but also on the method for harvesting of potatoes. Cultivation of potatoes involves the implementation of a set of measures aimed at improving and preserving the quality of commercial products when harvesting of potatoes. In this regard, to reduce yield losses and prevent wind erosion of soil, a unit and method for harvesting of potatoes is proposed. To reduce the number of clods commensurate with the size of tubers, there are installed ripper tines ahead of the potato harvester tool. The aim of the work is to conduct a theoretical research of the tool of the potato harvester to reduce yield losses and soil erosion. Materials and Methods. The lifting plowshare operation has been analyzed. Its angle to the horizon determines the least displacement of the lifting plowshare, the minimum resistance to the soil layer movement and optimal height of lifting soil mass. The optimal value of the plowshare inclination angle has been determined taking into account the condition that the back pressure of the soil layer should be minimal. Results. There has been proposed a mathematical dependence for determining the optimal value of the angle of plowshare inclination, which determines the minimum value of the soil layer back pressure acting along the plowshare. As a result of the research, there have been plotted graphical dependences of the optimal value of the plowshare inclination angle on the coefficient of soil friction on the plowshare and dependences of the height of a soil layer lifting with the plowshare on the inclination angle optimal value at a fixed plowshare length. Discussion and Conclusion. In carrying out the theoretical research of the potato harvester plowshare, the soil type and coefficient of a soil layer friction on the plowshare were taken into account. There has been determined the optimal angle of plowshare inclination to provide optimal breaking down of soil with minimum soil bulldozing, thus ensuring reduction in yield losses.

Soil wind erodibility and erosion estimation using Landsat satellite imagery and multiple-criteria decision analysis in Urmia Lake Region, Iran

Assessing variations in soil wind erosion (SWE) is critical for identifying key change areas and formulating desertification control strategies. Satellite images with an expansive spatial coverage and temporal repeatability make it possible to monitor the process of soil degradation and its consequences such as SWE. This research aims to model SWE in the eastern shoreline of Urmia Lake in the 2005–2017 period through multiple-criteria decision analysis (MCDA). Soil moisture, soil erodibility (SE), soil crust index, number of snow cover days, wind field intensity, and vegetation fraction were determined as critical factors affecting SWE. The analytic hierarchy process (AHP) method was applied to determine the weight of each factor. High SE and poor vegetation were the most important factors in the developed SWE model. The SE was precisely estimated (relative percent deviation (RPD)=2.01) by the support vector regression (SVR) method using Landsat-8 image. The developed SWE estimation method had an overall accuracy of 81%. Most of the eastern shoreline of Urmia Lake Region was classified in the severe SWE class. Results showed a declining erosion intensity trend from central parts with high wind erosion (47% of the region) to northern and southern parts of the region. Increasing the distance from the lake led to an increase in SWE.

Capparis spinosa L. Cenopopulation and Biogeochemistry in South Uzbekistan.

The article provides an analysis of the cenopopulation and tissues element composition of the medicinal caper plant Capparis spinosa L. distributed on Calcisols formed on eroded alluvial-proluvial gravel textured rocks in the south of the Fergana Valley (Uzbekistan, Central Asia). The predominance of immature plants in the cenopopulation was detected in the Arsif hills massive, and quantitative indicators of micronutrients in the vegetative and generative organs of C. spinosa L. were determined. The study of biomorphological characteristics of the plant during the growing season (April-October) was carried out in the identified 10 observational experimental field populations. The cenopopulation dynamics and plant development patterns of Capparis spinosa L. were characterized for environmental conditions of south Uzbekistan for the first time. Soil, plant element analysis was performed by neutron-activation method. In this case, the samples were irradiated in a nuclear reactor with a neutron flux of 5 × 1013 neutrons/cm2 s, and their quantities were determined in accordance with the half-life of chemical elements. It has also been compared with research materials conducted by world scientists on the importance and pharmacological properties of botanicals in medicine and the food industry, as well as their botanical characteristics. The plant can serve to conserve soil resources, as it prevents water and wind erosion of dense clay soils in the dry subtropical climate of Central Fergana and could be considered an effective agent of destroyed soils remediation. The development of this plant will contribute to the diversification of agriculture in Uzbekistan (Central Asia) and the development of the food industry and pharmacology.

Identification of driving forces for windbreak and sand fixation services in semiarid and arid areas: A case of Inner Mongolia, China

Soil wind erosion is a global problem that leads to increasingly serious regional land degradation, where the need for windbreak and sand fixation services (WSFS) is substantial. Inner Mongolia plays an important role in global semiarid and arid areas and the severe land degradation resulting from soil wind erosion warrants an urgent solution. However, the mechanism of influence of various driving factors on windbreak and sand fixation services is still not fully studied. In this paper, the revised wind erosion equation (RWEQ) model was used to synthesize the monthly spatiotemporal dynamics of soil wind erosion modulus (SWEM) and WSFS in Inner Mongolia from January 2000 to February 2020 from a semi-monthly scale. The influencing factors of WSFS were examined from both natural and anthropogenic aspects. Results show that over the past 20 years, the average SWEM in Inner Mongolia was 118.06 t ha−1 yr−1, the areas with severe wind erosion were mainly concentrated in the desert areas in the southwest of Inner Mongolia, and the forests in the northeast suffered less soil wind erosion. Meanwhile, the average WSFS was 181.11 × 108 t yr−1, with the high-value areas mainly located in major deserts, sandy land, and the area bordering Mongolia in the north and the low-value areas mainly located in the densely forested northeast and the Gobi Desert in the northwest. Both SWEM and WSFS showed a clear downward trend and a certain periodicity over the past 20 years. WSFS showed two peaks a year (April and October). Among the natural factors, precipitation and NDVI showed a significant correlation with WSFS and were identified as the main driving factors of WSFS, whereas temperature had no significant correlation. Among the anthropogenic factors, farming and animal husbandry intensity and GDP showed a positive correlation with WSFS, whereas population showed a negative correlation. These four types of factors were identified as socio-economic factors that drive WSFS. Meanwhile, WSFS did not show any significant correlation with the administrative area. Land use change contributed to a large proportion of WSFS change, thereby suggesting that the intensity of human activities is another central driver of WSFS.

Enhancing Ecosystem Services in the Agro-Pastoral Transitional Zone Based on Local Sustainable Management: Insights from Duolun County in Northern China

Ecosystem and associated ecosystem services (ESs) in the agro-pastoral transitional zone of northern China (APTZNC) are sensitive to climate change and human activities. Essential to designing targeted policy interventions toward achieving sustainability in the APTZNC is a comprehensive understanding of the spatiotemporal changes in ESs and their drivers. This study identified the spatiotemporal changes in six ESs in Duolun County from 2000 to 2017. The impacts of drivers—temperature, precipitation, wind speed, vegetation cover (FVC), land use/cover (LULC), soil type, altitude, and slope—on the changes in the ESs in the county and its ecological production zones were then explored. The results indicated that the six ESs improved during the study period. The drivers influencing changes in ESs over time exhibited similarities across regions. Although FVC contributed to improvements in the food supply, grass production, carbon sequestration, and soil wind erosion (SLwind), it also reduced water yield, which may exacerbate the water shortage in arid and semi-arid areas. In regions where the ecology was in the recovery phase, especially in slope farmland, the inhibition of soil water erosion (SLwater) by FVC was easily offset by the higher SLwater potential from increased precipitation. The decrease in wind speed improved the regional ESs, whereas the increase in temperature posed a threat to SLwind. The drivers affecting the spatial patterns of ESs varied among zones. Across the three zones, the greater influential drivers of ESs were FVC and LULC. The impacts of topographic drivers and soil type on the distribution of ESs should also be noted in the agro-zone and agro-pastoral zone, respectively. Our study advocated that ES management should be adjusted to local conditions, and differentiated planning policies should be implemented in line with the ecological characteristics in the APTZNC, which will contribute to regional ecological sustainable development.

Seed Germination Response and Tolerance to Different Abiotic Stresses of Four Salsola Species Growing in an Arid Environment.

Land degradation caused by soil salinization and wind erosion is the major obstruction to sustainable agriculture in the arid region. Salsola species have the potential to prevent land degradation. However, there is limited information about seed germination requirements and tolerance to salinity and drought for representative Salsola species. This study aimed to assess the effects of the winged perianth (seed structural features) and abiotic factors (light, temperature, salinity, and drought) on the seed germination of these species. These Salsola species varied considerably in seed germination characteristics. Compared with naked seeds, winged seeds had lower germination percentages for S. heptapotamica S. rosacea, and S. nitraria species. Darkness decreased the germination percentage of winged and naked seeds of S. rosacea, however, for S. heptapotamica and S. nitraria, decreased seed germination was only when the winged perianth existed. Germination of S. heptapotamica, S. rosacea, and S. nitraria seeds depended on the perianth and light conditions. The naked seeds of these three species could germinate at a wide range of temperatures, especially in light. The presence of perianth, light, and temperature did not significantly influence the germination of S. ruthenica seeds. When cultivating these species, it is beneficial to remove the winged perianth of seeds and sow it on the soil surface when the temperature is above 5/15°C. In addition, seed germination of Salsola displayed high tolerance to salinity and drought. Compared with winged seeds, naked seeds showed lower recovery germination under high salinity but had a similar recovery of germination under high PEG concentration. Our study provides detailed germination information for the cultivation of these four representative Salsola species in degraded saline soils of the arid zone.

Assessment of the effects of ecological restoration projects on soil wind erosion in northern China in the past two decades

Wind erosion is a typical natural hazard in arid and semiarid regions. In recent decades, China has shown significant changes of greening trend due to a range of several ecological restoration projects (ERPs), Meanwhile, the wind erosion in northern China changed significantly. The debate about whether climatic change or ERPs dominated the variations in wind erosion was never truly resolved, which seriously affect the deployment of ERPs in the future, and it is a concerns of both academia and the Chinese government. To address this debate, we distinguished the ERPs’ effects on wind erosion from the climate change background by modeling the wind erosion under the different surface vegetation scenarios with the revised wind erosion equation (RWEQ) that was validated by our field observations. The simulated results shown that relative to the benchmark year (2000), the ERPs caused a rate of decrease of 17.77% of wind erosion modulus (WEM) in northern China during the period of 2001 to 2019, which occupied approximately 61% of the total decrease of WEM by ERPs and climatic fluctuations. This result means that the ERPs played the dominant role in wind erosion decreasing overall. Considering the effects of ERPs to wind erosion, the wind erosion intensity, the climatic fluctuation, and vegetation carrying capacity, this study concluded that the Gurbantunggut Desert, the Otindag Sandy Land, the Lop Nor, the Gashun Gobi Desert, the Mongolia Gobi Desert and the Hexi Corridor are the potential regions for ERP deployment in the future. We believe this study should provide robust evidence to resolve the debate on what dominates the variations in wind erosion processes in northern China, and give the valuable suggestions for ecological restoration project deployment in the future.

Assessing the influencing factors of soil susceptibility to wind erosion: A wind tunnel experiment with a machine learning and model-agnostic interpretation approach

Soil wind erosion is a worldwide environmental concern. This study explored the feasibility of using a machine learning (ML) algorithm with a model-agnostic interpretation approach to infer the mechanism by which multiple features influence the soil susceptibility to wind erosion. Arenosols were collected from the Ulanbuhe Desert, China, and soil samples with different treatments, including wet-dry and freeze-thaw processes, were used in a wind tunnel experiment and provided a basic dataset for modelling. The Shapley additive explanations (SHAP) method was used to provide global and local interpretations for the ML model. The results showed the following. (1) The mean particle size tended to decrease and the soil organic carbon (SOC) and soil calcium carbonate (CaCO3) contents tended to increase in the transition from mobile to fixed sand dunes. (2) The ML models presented a better performance than the interpretable models, and the random forest model (R2 value of 0.898 on the test dataset) was adopted. (3) All the features except the SOC content showed monotonic or nearly monotonic relationships with the wind erosion rate. Relatively low SOC contents and high particle sizes tended to show positive interaction effects with wet-dry and freeze-thaw processes. An SOC content of 2.46 g kg−1 was deemed a threshold, above which SOC worked to resist wind erosion. ML algorithms and model-agnostic interpretation methods have the potential to improve the reliability and flexibility of inferring the mechanism by which soil is susceptible to wind erosion and thus deserve popularization in future studies.

Diverse responses of vegetation phenology to changes in temperature and precipitation in Northern China

The start and end of the vegetation growing season (SOS and EOS) determine the length of the vegetation growing season and are necessary parameters to assess the primary productivity and carbon stocks of vegetation as well as the key dates to determine the start and end of soil wind erosion in arid zones. However, how SOS and EOS of different types of vegetation respond to changes in temperature and precipitation is still unclear. In this study, Moderate-resolution imaging spectroradiometer (MODIS)-normalized difference vegetation index data from 2001 to 2015 were used to estimate SOS and EOS for each vegetation type, the temperature and precipitation data recorded by the meteorological stations in the study area were used to calculate the average temperature and precipitation in 19 periods from June of the previous year to November of the following year, Spearman's rank correlation analysis was used to analyze the response relationships of SOS and EOS to average temperature and precipitation in each period. The results showed that SOS, EOS, the average timing of SOS (AvSOS) and the average timing of EOS (AvEOS) all had strong spatial heterogeneity. Precipitation is the key factor controlling SOS and EOS, an increase causing SOS to advance and EOS to be delayed, while higher temperature has the opposite effects. Overall, the average advancement rate of SOS was 0.88 day/year, the average delay rate of EOS was 0.33 day/year. From southeast to northwest, AvSOS gradually changed from 121st day to 141st day, whereas AvEOS was the opposite, advancing from 271st day to 282nd day. We divided the vegetation into 12 types in the soil wind erosion area of northern China according to latitudinal zonation and dominant vegetation species, the results avoided t a shortcoming of previous studies in which SOS and EOS were identified without distinguishing vegetation types.

The impact of Tamarix invasion on the soil physicochemical properties

The exotic Tamarix species, T. ramosissima and T. chinensis, were introduced into South Africa in the early 1900s reportedly either for ornamental or soil wind erosion control purposes in the mines. They are, however, currently invading several riparian ecosystems in the country and threatening its biodiversity and proper functioning. The objective of this study was to assess the effects of the exotic Tamarix species on the soil physicochemical properties vis-à-vis the indigenous Tamarix at the Leeu River in the Western Cape Province, of South Africa where they are purvasive. Three transects were laid from the riverbank towards the outer land, where the exotic followed by the native Tamarix species predominantly occurred. Soil was sampled from three points per transect and three soil depths (0–10, 10–20 and 20–30 cm) per point in winter and summer to determine selected soil physicochemical properties. The results showed that total nitrogen (TN), total carbon (TC), Sodium (Na), Potassium (K) and Magnesium (Mg) concentrations under the native and exotic Tamarix species were significantly higher than those in the open land without Tamarix species. The salinity under the native and exotic Tamarix species was greater (P < 0.05) in the topsoils (0–10 cm) than in the deeper soils (20–30 cm) with 5.05 mS cm−1 and 4.73 mS cm−1, respectively. Soil electrical conductivity (EC) was higher (P < 0.05) during the winter season under the exotic Tamarix species (5.05 mS cm−1) followed by the native species (4.73 mS cm−1) and it was the lowest in the control (0.16 mS cm−1) at 0–10 cm soil depth. Similarly, sodium and sodium absorption ratios (SAR) under the native and exotic Tamarix species were significantly greater than those in the control. The highest levels (P < 0.05) of TC were recorded at the topsoil (0–10 cm soil depth) under the exotic Tamarix species (1.17%), followed by the native Tamarix (1.07%) with the control recording the lowest (0.53%). There were no significant differences (P < 0.05) in K, TC, TN and SOC concentrations at lower soil depths (20–30 cm). The soil texture was significantly affected by the Tamarix species. The soil bulk density was lower under the exotic Tamarix followed by native Tamarix species than the control soils. The soil volumetric water content was higher under the exotic Tamarix species compared to the control. This study concludes that the invasion of the exotic and native Tamarix species altered the soil properties underneath and created conducive soil conditions for their predominance.

Transport preferences of P forms in wind-blown sediments of two susceptible soils

• P forms concentrations of aeolian sediments of different textured soils was assessed. • Mineral and organic P were transported in particulate matter of both soils. • Labile mineral P was transported in saltating sediments of both soils. • Labile P showed a secondary accumulation in particulate matter of the sandy loam soil. • The total P reflected the vertical distribution of the major form, the mineral one. • P forms vertical distribution depended greatly on the bulk soil characteristics. Wind erosion of agricultural soils affects their stock of essential elements for plants, like phosphorus (P). It is known that the composition of the eroded sediments varies with height, according to the size and density of the transported substances. Aim of this study was to analyze the concentration and enrichment ratios of P forms in sediments transported by the wind. A wind-tunnel study was performed on a sandy- and a sandy loam soil in order to measure P forms concentrations in the saltating sediments. P concentrations were also measured in the particulate matter (PM) of each soil, gained with the Easy Dust Generator. In both soils, inorganic- (P i ) and organic P (P o ) were preferentially transported in PM, with enrichment ratios of 1.8 and 5.5, respectively. Nevertheless, a P i /P o of 0.9 indicated that the accumulation of the minor P o in PM was more pronounced than P i . This agrees with P-rich light and easily erodible organic compounds, almost exclusively accumulated in PM, and in relatively heavy and less erodible minerals, like apatites, in lower height sediments. Labile P (P l ) was preferentially transported in saltating sediments of both soils. This was attributed to the selective Bray & Kurtz I’s extraction of the abundant inorganic P forms of these sediments. Total P (P t ) copied the transport trends of P i , the major form. According to the transporting trends, P i and P o would be re-sedimented at longer distances from the source than P l . Outcomes become useful for modeling the influence of wind erosion on P cycling.

Investigating the Effect of Microbial Induced Carbonate Precipitation on Reducing Wind Erodibility of Soils in Segzi Desert Area, Isfahan

Investigating the Effect of Microbial Induced Carbonate Precipitation on Reducing Wind Erodibility of Soils in Segzi Desert Area, Isfahan

A comparison of the aerodynamic characteristics of four kinds of land surface in wind erosion areas of northern China

Aerodynamic characteristics is a crucial factor influencing soil wind erosion, which is closely related to the properties of surface roughness elements. In the expansive arid and semi-arid northern China, grassland, farmland, mobile sandy land, and gobi are the main land surface types that suffer wind erosion to varying degrees. To investigate the aerodynamic characteristics of different surfaces, we used three-dimensional ultrasonic anemometers to observe the near-surface wind speed above grassland, farmland, mobile sand, and two types of gobi surfaces in areas of northern China (a total of five observation sites). We compared the aerodynamic characteristics of the five surfaces and their causes (i.e., the surface roughness length, wind speed pulsation, turbulence intensity, and drag coefficient), and analyzed how surface roughness elements weakened the airflow. The roughness length was greatest for grassland, followed by farmland, sand, fine gobi, and black gobi. The pulsation intensity of near-surface wind speed increased linearly with increasing wind speed at all sites. At a given wind speed, increasing roughness length increased the pulsation intensity of wind speed. The probability distributions for the drag coefficient and turbulence intensity of the five surfaces followed a positively skewed distribution. The drag coefficient and turbulence intensity were greatest for grassland, followed by farmland, sand, fine gobi, and black gobi surfaces. The drag force exerted on the roughness elements increased with increasing wind speed, but the ratio of drag force exerted on the roughness elements to the total drag force (τR/τ) for flexible roughness elements (i.e., plants) increased as the wind speed increased; for rigid roughness elements, τR/τ decreased with increasing wind speed. This confirms that the shelter capability of flexible roughness elements against soil wind erosion increases with the increase of wind speed, while that of rigid roughness elements is opposite.

Full Title: Quantifying the ecological carrying capacity of alpine grasslands on the Qinghai-Tibet Plateau

Ecological carrying capacity (ECC), as an efficient approach in sustainable management, also was used to indicate ecosystem stability in vulnerable ecoregions. In this study, we proposed a new framework of ECC quantification focusing on vulnerable ecoregions and analyzed ECC on the Qinghai-Tibet Plateau (QTP) based on the ecogeographical regionalization. Some indicators were introduced in ECC assessing, such as effective vegetation cover required to make soil water erosion lower than the threshold of soil loss (EVCwater), effective vegetation cover required to make soil wind erosion lower than the threshold of soil loss (EVCwind), and above-ground net primary production that can be used for human activities (UANPP). The results showed that: (1) EVCwater increased from northwest to southeast on the QTP, and exceeded 70% in the southeastern QTP; (2) EVCwind for the entire Qinghai-Tibet Plateau increased from southeast to northwest, and was ≤ 30% in most areas of the eastern QTP; (3) the UANPP in most study areas ranged from 0 to 408.69 g m−2 yr−1, with a regional average of 95.06 g m−2 yr−1, and areas with a UANPP < 0 g m−2 yr−1 were mainly distributed in the HID1 ecoregion; and (4) the average ECC for alpine grasslands on the Qinghai-Tibet Plateau is 1.47 sheep unit hm−2, although values increased gradually from northwest to southeast.