Pisha Sandstone Area Research Articles

Spatiotemporal Variability of Soil Erosion in the Pisha Sandstone Region: Influences of Precipitation and Vegetation

The Pisha sandstone area, situated in the upper and middle reaches of the Yellow River in China, is characterized by severe soil and water erosion, making it one of the most critical regions on the Loess Plateau. The rugged terrain and exposed bedrock complicate management efforts for this area, posing challenges for accurate forecasting using soil erosion models. Through an analysis of terrain, vegetation, and precipitation impacts on soil erosion, this study offers theoretical support for predicting soil erosion within the exposed Pisha sandstone area of the Loess Plateau. This has substantial implications for guiding water and soil conservation measures in this region. Focusing on China’s exposed sandstone area within the Geqiugou watershed, temporal and spatial changes in vegetation cover and land use from 1990 to 2020 were analyzed. The result shows that, from 1990 to 2020, the grassland area has exhibited a consistent downward trend, with successive reductions of 64.86% to 59.46%. The area of low vegetation cover witnessed a significant decline of 59.29% in 2020 compared to that in 1990. The moderate erosion area decreased from 84.52 to 57.17 km2. The significant reduction in soil and water loss can be attributed to the expansion of forest and grassland areas, with the implementation of the Grain for Green project serving as a key policy driver for facilitating this expansion. This study provided a good example of combining rainfall with vegetation coverage to fast estimation soil erosion. A mathematical relationship between the vegetation rainfall coupling index (RV) and soil erosion was established with strong fitting effects, enabling estimation of the soil erosion volume under varying slope conditions within Pisha sandstone areas. The main focus of future soil and water conservation in the Pisha sandstone area should be on effectively managing the channel slope and minimizing exposed bedrock areas through a combination of slope cutting, the application of anticorrosive materials, and the implementation of artificial vegetation planting.

Comparison and mechanism study on solidification of loose pisha sandstone by indigenous bacteria and sporosarcina pasteurii

Pisha sandstone is a kind of sandstone which is easy to collapse by water in Shanxi, Shaanxi and Inner Mongolia of China, and suffers from hydraulic erosion all the year round. In recent years, some scholars have used microbial induced calcium carbonate precipitation (MICP) technology to solidify Pisha sandstone to improve the water erosion resistance of Pisha sandstone. However, for the climate environment with low average temperature in Pisha sandstone area, the commonly used Sporosarcina pasteurii are not well adapted. The purpose of this study is to use the indigenous strainsto solidify the loose Pisha sandstone, and to compare the growth adaptability, mechanical properties and water erosion resistance of the solidified layer with Sarcina pasteurii at different temperatures, and to explore the mechanism of different temperatures and strains affecting the microbial solidification of Pisha sandstone from the micro scale. At the same time, a mixed bacterial liquid solidification test was also set up. The results showed that the solidified thickness of indigenous strains was 4.65 % higher than that of Sporosarcina pasteurii, and the thickness and strength of mixed strains were increased by 19.57 % and 36.62 %, respectively. The growth and solidification effect of indigenous strains were less affected by low temperature. Compared with Sporosarcina pasteurii, at low temperature, the bacterial concentration decrease of indigenous strains was reduced by 26.13 %, the thickness loss of solidified layer was reduced by 13.04 %, and the strength loss of solidified layer was reduced by 13.39 %. The effect of low temperature on the growth of bacteria is mainly reflected in affecting the maximum concentration of bacteria and the growth rate. The effect on MICP mainly reflected in affecting the life activities of bacteria and the crystal form and morphology of calcium carbonate. The research results provide a theoretical basis for the MICP technology application of indigenous strains and multi-strains in Pisha sandstone area soil reinforcement and solidification slope.

Spatiotemporal variation and driving force of gully erosion in the Pisha sandstone area

The experiment was conducted on gully slopes with slopes ranging from 80° to 90° to investigate the relationship between erosion rates, spatial and temporal changes in microtopography, and drivers of erosion on gully slopes in different seasons. To precisely characterize the microtopography of slopes where debris slides occur, we used the RIEGL VZ-400 3D laser scanner to scan the observation site and acquire point cloud data on the slope’s microtopography. Using the “data conversion module” of ArcGIS software, the point cloud data were transformed into raster data. Through the “3D analysis,” “hydrological analysis,” and “grid calculator” modules, the basic microgeomorphological indicators were extracted from the gully slope grid data, and the erosion rate and microterrain evolution mechanism of the gully slope in different seasons were also determined. The results revealed the following: (1) in the Pisha sandstone area, erosion was relatively strong in the first quarter, with 65% of the area being eroded. The average erosion rates over the four quarters followed the order of first quarter > fourth quarter > second quarter > third quarter, from fastest to slowest. (2) As the soil on the gully slope thawed, melt water increased soil moisture. This phenomenon sharply increased surface roughness in the first quarter. The correlation coefficients between the erosion rate and temperature in the first and fourth quarters were 0.75 and 0.82, respectively. Temperature mainly affected the erosion rate through surface roughness. The direct path coefficient of this effect was 0.72. (3) In the first and fourth quarters, temperature and wind speed were the main factors influencing the erosion rate; the relationship between surface roughness and other factors was evident, making surface roughness the best topographic factor for assessing slope erosion in the Pisha sandstone area. The results of this study aim to provide theoretical references for understanding the gravity erosion mechanism of gully slopes in the Pisha sandstone area and contribute to the high-quality development of the Yellow River Basin.

Effect of W-OH Material on Water/Fertilizer Retention and Plant Growth in the Pisha Sandstone Area of China

Effect of W-OH Material on Water/Fertilizer Retention and Plant Growth in the Pisha Sandstone Area of China

Geochemical indicators to constrain weathering, provenance and tectonic setting of the Pisha Sandstone (Early–Middle Triassic) in Northeast Ordos Basin, China

The Pisha Sandstone is widely exposed in the northeastern margin of the Ordos basin. Since the Mesozoic the basin was subjected to uneven uplift several times, strong weathering and erosion have been occurring and a large amount of sediments derived from these erosional strata are input into the lower Yellow River, posing a fragile ecological environment along the river. However, the geochemical characteristics of the Pisha Sandstone have remained poorly understood. In this study, we focus on the Pisha Sandstone from Early–Middle Triassic Liujiagou, Heshanggou and Ermaying Formation, present a very first petrographic and geochemical data together with detailed field geological characteristics, aiming to place geochemical indicators on weathering, provenance and tectonic setting of the Pisha Sandstone. The results show that sandstones in Pisha Sandstone are classified as arkose, litharenite and wacke. The geochemical proxies including Chemical Index of Alteration (CIA = 67.2), Chemical Index of Weathering (CIW = 80.1), Plagioclase Index of Alteration (PIA = 75.6) and Index of Compositional Variability (ICV = 1.6) indicate Pisha Sandstone experienced first–cycle deposit and moderate to strong chemical weathering. Trace element and rare earth element concentrations together with their ratios (La/Sc, La/Co, Th/Sc, Th/Co, Cr/Th) reveal a felsic provenance, and source rock compositions are predominantly granodiorite and granite from the north margin of the Inner Mongolia Paleo–Uplift (IMPU), with a small amount of mafic or intermediate components. The geochemical signatures and tectonic discrimination diagrams display a collision setting for the Pisha Sandstone and further reveal the sediments had been deposited in a continental island arc setting. The results of this work may provide new theoretical basis for environmental protection in the Pisha Sandstone area.

Dynamic simulation study of soil erosion intensity on slopes with different vegetation patterns in pisha sandstone area

The study of soil erosion is significant to soil and water conservation and ecological construction planning. CA, a dynamic modeling method, has been widely used to simulate the future changes of soil erosion intensity. In this study, three slopes with different vegetation patterns (uniform distribution, aggregated distribution, and random distribution) and a bare slope in the Baojiagou watershed in the Pisha sandstone area were taken as the study objects. Based on the soil erosion intensity grade maps of slopes with different vegetation patterns under the three periods of rainfall, the soil erosion intensity grade maps of the four slopes were simulated by combining multi-criteria evaluation (MCE) and Markov chain (CA-Markov). Through tests, the Kappa coefficients of the simulated maps of uniform distribution, random distribution, aggregated distribution and a bare slope reached 80.15%, 75.41%, 75.92% and 76.48%, respectively. The results revealed that the soil erosion types on slopes with different vegetation patterns were transferred differently, and fewer erosion areas were generally transferred into highly eroded ones, with moderately and slightly eroded areas as the main transfer flows. After simulating the grade map of soil erosion intensity on slopes with different vegetation patterns, it was found that the slopes with uniform and random vegetation distribution primary displayed the transfer from highly eroded areas to less eroded ones, and the sedimentary area was enlarged, while the slope with aggregated vegetation distribution and the bare slope mainly presented the transfer from less eroded areas to highly eroded ones. The sedimentary area was diminished. Therefore, compared with the bare slope, the slopes with uniform and random vegetation distribution exerted a better inhibitory effect on the soil erosion degree of hydraulically eroded slopes, and the inhibitory effect of aggregated vegetation distribution-type slope was the weakest. The study results provide critical information for planning and implementing soil conservation measures in the study area.

Analysis of the Ecological Value of Pioneer Plants in the Yellow River Basin

Pioneer plants are plant species that appear early in the community succession or show strong adaptability, which can improve the local ecological environment and create conditions for the succession and recovery of other plants and animals. After analyzing the general situation in the Yellow River Basin, this paper explores the main ecological values of pioneer plants, such as treatment of salt-alkali land, soil and water conservation, improvement of soil quality, community succession and biodiversity promotion. Also, typical cases of pioneer plants used for treatment and restoration in ecologically fragile areas such as Shanxi-Shaanxi-Inner Mongolia Pisha sandstone area, coastal saline-alkali land, abandoned mine pits in Yellow River Basin are introduced and analyzed to provide a theoretical basis for further embodying the ecological function of pioneer plants in the Yellow River Basin.

Combining infiltration hole and mulching techniques with fish-scale pits effectively improved soil water storage in semiarid areas with shallow buried bedrock (Pisha Sandstone) in China

Effectively regulating slope runoff and infiltrating maximum rainwater are essential to reduce soil and water loss, and promote vegetation restoration in the Pisha Sandstone areas of China, which are semiarid areas with shallow buried bedrock. However, the effects of individual or combined rainwater regulation measures, such as infiltration holes, mulch, and fish-scale pits (a semicircle-shaped pit), on soil water infiltration and restoration in such regions have not yet been fully explored. In this study, the responses of soil water to rainfall in the 0–1.6 m soil layer was investigated through in situ monitoring during the two main rainy seasons under four rainwater regulation treatments in the Pisha Sandstone area of China covered in thin soil layer (0–0.3 m): fish-scale pits with grass mulching and infiltration holes (PGH), fish-scale pits with grass mulching (PG), fish-scale pits without mulching (P), and slope land (control, CK). The results have shown that because of the relatively low permeability (0.08–0.17 m d−1) of Pisha Sandstone, individual torrential rainfall events (63.2 mm) increased the soil water only in the 0–0.3 m layer after 3 days under the CK, P, and PG treatments. However, the PGH treatment simultaneously and significantly increased the soil water in the 0–0.3 m and 0.7–0.8 m layers. Compared with the CK treatment, rainwater replenishment depths under the P, PG, and PGH treatments increased from approximately 0.4 m to 0.9 m, 1.0 m, and 1.1 m, respectively, and the average soil water storage increased by 27 mm, 34 mm, and 50 mm, respectively, in the 0–1.6 m soil layer. Moreover, the PGH treatment enhanced rainwater storage in deep soil (0.6–0.9 m), which decreased the potential for water loss by evaporation. We concluded that the PGH treatment was effective in increasing soil water storage and reducing soil erosion in areas with shallow buried bedrock.

Effect of Hydrophilic Polyurethane on Interfacial Shear Strength of Pisha Sandstone Consolidation under Freeze-Thaw Cycles.

The W-OH type polyurethane (W-OH) has been proven to be an economical and environmentally friendly slope protection solution for slope maintenance in Pisha sandstone areas. However, the Pisha area belongs to a typical temperate continental climate with large diurnal temperature changes in winter, spring, and autumn and freezing and thawing occurring alternately between days and nights. Under freeze-thaw cycle conditions, the effect of slope treatment largely depends on the interface shear strength between W-OH-treated Pisha sandstone and pristine sandstone. Therefore, this paper studies the interfacial shear strength and long-term durability of Bisha sandstone consolidation (W-OH-treated Pisha sandstone) and Pisha sandstone under freeze-thaw cycles. First, the effects of different W-OH concentrations and different water contents on the freeze-thaw cycle interface were studied using a direct shear test. Based on the experimental results, the W-OH material was further modified with ethylene vinyl acetate (EVA). Finally, the damaged surface of the sample was observed through an ultra-depth-of-field microscope, and the damage mechanism of the interface caused by the freeze-thaw cycles was further discussed. The experimental results show that the peak shear strength at the interface increases with the increase in W-OH concentration and decreases with the increase in freeze-thaw cycles. The cohesion at the interface generally increases with the increase in W-OH concentration and reaches a maximum value of 43.6 kPa when the W-OH concentration is 10%. At the same time, under the condition of high water content, the curing of the W-OH material has no significant effect on the bonding performance of the interface. Using EVA to modify the W-OH material can improve the freeze-thaw durability of the interface. After modification, the interfacial cohesion of the sample increases with the increase in the EVA concentration and can reach 162% of the original. Using an ultra-depth-of-field microscope, it was found that the repeated solidification-melting action of water between the interfaces makes the consolidated body on the damaged surface fall off, resulting in cracks. As the water content between the interfaces increases, the damage to the material is greater. However, the addition of EVA can fill the uncovered pores of W-OH cement, thereby improving the cohesion at the interface and effectively alleviating the freeze-thaw damage caused by the high water content at the interface. The results of this study can provide some theoretical references for slope treatment in the Pisha sandstone area using W-OH materials.

Identification of Vegetation Coverage Variation and Quantitative the Impact of Environmental Factors on Its Spatial Distribution in the Pisha Sandstone Area

Over the past few decades, global vegetation cover has obviously changed, particularly in the Loess Plateau, due to vegetation restoration projects in China. This study focuses on the Pisha Sandstone area (PSA) and uses various statistical analysis methods to study the spatiotemporal changes in vegetation coverage (VEC) at different time scales. The effects of topographical and climatic factors on VEC were also quantitatively evaluated using the GeoDetector in the spatial distribution. The results of the study confirm that, on an annual scale, the area with a significant increase in VEC has reached 63.89% (p < 0.05). Change points were diagnosed to have occurred mainly between 2002 and 2012 at different time scales, with the percentage of significant change points in VEC accounting for more than 20% from April to October (p < 0.05). Temporal and spatial changes in precipitation mainly caused VEC changes. In 45.35% of the region, precipitation was significantly and positively correlated with VEC at an annual scale (p < 0.05). Moreover, VEC was most conducive to growth and increase at 1050–1500 m above sea level and 0–21° slope, respectively. In most areas, there was an enhanced interaction relationship between various factors on VEC. Converting farmland to forests in suitable areas, selecting appropriate tree species, and improving soil is conducive to ecological restoration in the PSA in the future.

Variation Characteristics of Two Erosion Forces and Their Potential Risk Assessment in the Pisha Sandstone Area

Precipitation and wind, as the main external erosion forces in wind–water erosion crisscross regions, have profound impacts on water and soil loss. Meanwhile, with the intensification of climate change and human activities, the variation characteristics and risks caused by erosion forces need to be reassessed. In this study, we explored the time-varying characteristics, differences in action period and spatial distribution, and temporal evolution of risk for the compound events of two erosion forces, including precipitation and wind, in the Pisha sandstone area, one of the most seriously eroding and difficult-to-control areas in the Loess Plateau. The results indicated that: (1) the stationarity of regional precipitation was not destroyed, but the mean change existed in the five subseries divided by the detected change points in wind; (2) wind acted earlier than precipitation and increased from southeast to northwest, while precipitation did the opposite; and (3) precipitation-led erosion has become the main erosion type in this area. The above results reveal the evolution and dominant types of regional external erosion forces in a changing environment and thus have implications for regional erosion studies and policy adjustments.

Characteristics of sediment particle size distribution in the Pisha sandstone area of the middle Yellow River under the effects of vegetation and complex erosion

AbstractPisha sandstone is a soft bedrock composed of sandstone, sand shale and mudstone, with very low diagenesis and erosion resistance. The sources of coarse sediment and the processes of sediment production and transportation in Pisha sandstone areas are currently little understood. Understanding these processes will help us to comprehend the characteristics of sediment particle size distribution on slopes and gullies under the effects of vegetation and complex erosion. This will provide a scientific basis for the control of coarse sediments of the Yellow River and ecological restoration of the Pisha sandstone area. In this study, the process of sediment selectivity and transportation in the slope–gully system was analyzed through soil sampling in different seasons in the Erlaohugou small watershed, China. There is a clear selectivity phenomenon in the process of transporting sediment particles from the slope to the gully, and the coarse sediment particles are transported preferentially from the slope to the gully. There is a good response relationship between the distribution characteristics of sediment particles and the multi‐dynamic interaction. The complex erosion type in different seasons has a significant impact on sediment production and transportation, and most particles were transported under hydraulic power.

Evaluating the applicability of the water erosion prediction project (WEPP) model to runoff and soil loss of sandstone reliefs in the Loess Plateau, China

Soil erosion is one of the most serious environmental issues, especially in vulnerable areas such as the Pisha sandstone regions located in the Loess Plateau (China). In these types of reliefs, long-term studies monitoring runoff and soil loss are scarce, and even more considering the efficiency of different soil management techniques applied to reduce land degradation. In this study, seven years (2014–2020) of in-situ measurements of surface runoff and soil loss for different land uses (forestland, shrubland, grassland, farmland, and bare land) in a Pisha Sandstone environment at the Loess Plateau were conducted. We applied the Water Erosion Prediction Project (WEPP) model combining the large database with the precipitation regimes. Our results showed that runoff volume coming from observed and simulated data exhibited significant differences among them depending on the different vegetation types. Runoff and soil loss were different among diverse land use types as follows: farmland > grassland > shrubland > forestland. After conducting a calibration, we found satisfactorily simulated surface runoff and sediment yield based on precipitation regimes and land uses at sandstone reliefs. Simulation performance of surface runoff was better than sediment yield. The range of standard error of the model simulation for event and annual values of runoff were 4.71 mm and 12.19 mm, respectively. The standard error for event and annual values of soil loss were 4.19 t/hm2 and 21.86 t/hm2. In the calibration group, R2 of runoff and soil loss were 0.92 and 0.86 respectively, while Nash-Sutcliffe coefficient (E) reached 0.90 and 0.85, respectively. In the validation group, the R2 for both runoff and soil loss were 0.82 and 0.56, respectively. Nash-Sutcliffe coefficient (E) were 0.77 and 0.54 for the runoff and sediment yield. We concluded that using a detailed monitoring dataset, the WEPP model could accurately simulate and predict water erosion in the hillslopes of Pisha sandstone area.

Strength and microscopic mechanism analysis of CFBCA-based geopolymer-Pisha sandstone cement composite soil.

Solidification of soil mass by geopolymer is a novel technology that can be used to prevent soil and water loss in the Pisha sandstone area of the middle reaches of the Yellow River. In this paper, to realize the effective utilization of a large number of loose Pisha sandstone and circulating fluidized bed combustion fly ash by adding combustion fly ash into Pisha sandstone cement-soil by alkali excitation, we prepared CFBCA-based geopolymer-Pisha sandstone cement composite soil, which is often used in agricultural engineering. The results show that the content of (C, N)-A-S-H gel in composite soil is affected by alkali equivalent and alkali excitation temperature, while the content is the main factor affecting the strength of composite soil. However, (C, N)-A-S-H gel will gradually transform into chabazite (gmelinite) crystal in a high-alkali environment, which will eventually lead to expansion and cracking occurring in the samples. When the alkali excitation temperature is 20°C, and the alkali equivalent is 5%, the CFBCA-based geopolymer-Pisha sandstone cement composite soil is the optimal physicochemical reaction condition. At this time, the strength of the composite soil is 6.85MPa; the porosity is 23.88%; and the proportion of internal micro-pores is 16.32%. The results of this study can provide a theoretical basis for the practical application of CFBCA-based geopolymer-Pisha sandstone cement composite soil, and also provide a scientific basis for the local resource utilization of Pisha sandstone and bed combustion fly ash.

砒砂岩区植被覆盖度环境驱动因子量化分析——基于地理探测器

PDF HTML阅读 XML下载 导出引用 引用提醒 砒砂岩区植被覆盖度环境驱动因子量化分析——基于地理探测器 DOI: 10.5846/stxb202103020564 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（42077074）；国家重点研发计划（2017YFC0504501） Quantitative analysis of environmental driving factors of vegetation coverage in the Pisha sandstone area based on geodetector Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:砒砂岩区地形破碎，生态环境恶劣，降水量少且以暴雨为主，研究该区植被覆盖变化及环境驱动因子作用机制对区域植被建设具有重要的理论意义。基于1999-2018年的NDVI数据分析了砒砂岩区近20年植被覆盖度时空变化特征，利用了地理探测器方法量化分析了不同环境因子对植被覆盖度的影响。结果表明：1）近20年砒砂岩区平均植被覆盖度为42.3%，时间尺度上1999-2018年区域植被覆盖度呈增加趋势，平均上升幅度为0.086/10 a，空间尺度上植被覆盖度呈现从东南向西北递减的空间分布特征；2）近20年区域植被覆盖整体得到改善要比退化的区域面积大，45.5%的区域面积植被覆盖度极显著增加，主要分布在砒砂岩区东部区域，该区植被覆盖度未来变化趋势将以持续性改善为主，但仍有约41.6%的植被将由改善向退化方向变化；3）降水、土壤水分和气温是影响砒砂岩区植被覆盖空间分布的主导环境因子，且降水同其他环境因子的交互作用对植被覆盖影响最大。 Abstract:The Pisha sandstone area is broken in topography, with little precipitation and mainly rainstorm, the ecological environment in the area is harsh. It is of great theoretical significance for regional vegetation construction to study the dynamic change of vegetation and explore the response characteristics of vegetation coverage to environmental factors. Based on the normalized difference vegetation index (NDVI) from 1999 to 2018, this study analyzed the spatio-temporal change characteristics of vegetation coverage in the Pisha sandstone area. In addition, the geodetector was used to analyze the influence of different environmental factors on the change of vegetation coverage, then we determined the most suitable range and type of each factor to promote vegetation growth. The results show that:1) In the past 20 years, the average vegetation coverage in the Pisha sandstone area was 42.3%. On the time scale, the regional vegetation coverage had an increasing trend from 1999 to 2018, with an average increase of 0.086/10 a. On the spatial scale, the vegetation coverage presents a distribution characteristic of decreasing from southeast to northwest. The vegetation coverage of the three areas changes from large to small in order of soil-covered Pisha sandstone area, sand-covered Pisha sandstone area, and bare Pisha sandstone area. 2) In the past 20 years, the overall improvement of vegetation coverage in the Pisha sandstone area is greater than the degraded area. About 45.5% vegetation coverage of the regional area has increased obviously, mainly in the eastern part of the Pisha sandstone area whereas the significantly reduced areas were scattered in the middle of the bare area. The future trend of vegetation coverage in the Pisha sandstone area will be dominated by continuous improvement, accounting for 50.5% of the total area, mainly distributed in the southern soil-covered Pisha sandstone area. Although the vegetation in this area is showing an overall trend of improvement, it still faces greater challenges. About 41.6% of the vegetation is at risk of changing from improvement to degradation. 3) Precipitation, soil moisture and temperature are the dominant environmental factors that affect the spatial distribution of vegetation coverage in the region, while the slope and aspect have the weakest explanatory power for vegetation coverage. The interaction among environmental factors is dominated by a two-factor enhancement trend. As the dominant climate factor in the spatial distribution of vegetation coverage in this region, precipitation has the greatest influence on vegetation coverage under the interaction with other environmental factors. 参考文献 相似文献 引证文献

Analysis of complex erosion models and their implication in the transport of Pisha sandstone sediments

Coarse sediment of the Yellow River in the complex erosion area of the Pisha sandstone region of the Ordos Plateau is deposited on the downstream riverbed, posing a threat to the flood control safety of the river. The objectives of the present study were to analyze the mechanisms of combined erosion and sediment yield under the synergistic action of multiple dynamics, employing the indoor artificial rainfall-wind-freezing-thawing cycle solid model test to explore the temporal and spatial variation of the coarse sediment production and the transportation process. In this study, complex erosion indoor tests were carried out through the artificial rainfall-wind-freezing-thawing cycle solid model. The enrichment rate (ER), fractal dimension, and median diameter (d50) of soil particles were used to quantify the size distribution characteristics of sediment particles under different erosion dynamics. The coarse sediment was first transported in the process of soil erosion because of the special texture and terrain characteristics of Pisha sandstone soil. Moreover, the degree of heterogeneity of sediment under complex erosion was larger than that under water erosion. The effect of wind could aggravate the instability of the erosion dynamic system. Under the combined action of freezing-thawing, wind, and water, the particle size composition changed greatly, and the erosion energy was extremely unstable. The effect of complex erosion created conditions for the coarse sediment transportation. Under the freezing-thawing-wind-water combined action, the particle size of eroded sediment was the coarsest, and that of water erosion was the smallest. We concluded that the reason why the Pisha sandstone area has become the core area of the concentrated source of coarse sediment in the Yellow River is related not only to the special nature of the Pisha sandstone soil itself but also to the effect of complex erosion.

Effects of shrub-grass patterns on soil detachment and hydraulic parameters of slope in the Pisha sandstone area of Inner Mongolia, China

Effects of shrub-grass patterns on soil detachment and hydraulic parameters of slope in the Pisha sandstone area of Inner Mongolia, China

Effects of a compound microbial agent and plants on soil properties, enzyme activities, and bacterial composition of Pisha sandstone.

The objective of this study was to investigate the effects of the microbial agent on the improvement of Pisha sandstone soil and find out an effective measure for the control of soil erosion in the Pisha sandstone area. Pisha sandstone containing the microbial agent composed of Bacillus halotolerans P75, Sinorhizobium meliloti D10, Bacillus megaterium H3, Bacillus subtilis HB01, and organic substrate was utilized to be the soil matrix for pot experiment, and then alfalfa, ryegrass, and caragana were planted, respectively. Effects of the microbial agent plus plants on the soil properties of Pisha sandstone were evaluated, and the results showed that the microbial agent plus plants significantly increased the organic matter content, alkali hydrolyzed nitrogen content, available phosphorus content, available potassium content, invertase activity, and urease activity. Meanwhile, inoculation with the microbial agent significantly promoted the growth of alfalfa, ryegrass, and caragana and also influenced the number of soil bacteria and the relative abundance of Proteobacteria, Bacteroidetes, Actinobacteria, and others. However, the effects of the microbial agent plus different plants on the soil properties and bacterial composition of Pisha sandstone were different, while the growth of different plants showed differences, suggesting that there was a different interaction between microbes and different plants in Pisha sandstone soil. In conclusion, the microbial agent plus plants could improve Pisha sandstone soil which could provide some theoretical and experimental references for soil erosion control in the Pisha sandstone area.

Vegetation Growth Status and Topographic Effects in the Pisha Sandstone Area of China

Fractional vegetation coverage (FVC) plays an important role in monitoring vegetation growth status and evaluating restoration efforts in ecological environments. In this study, FVC was calculated using a binary pixel model and analyzed in the Pisha Sandstone area of China, using MODIS-EVI data from 2000 to 2019. Topographic effects were analyzed from elevation, slope and aspect using a terrain niche index model. The results were as follows. (1) From 2000 to 2019, FVC in the Pisha Sandstone area of China gradually increased at a mean rate of 0.0074/a, and the growth status of vegetation gradually improved. (2) The spatial distribution of FVC steadily decreased from southeast to northwest. FVC was the lowest in bare parts of the Pisha Sandstone area, whereas those in the sand- and soil-covered parts were the middle and highest, respectively. (3) With increasing elevation, the inferior coverage area and terrain niche index increased, and inferior coverage distribution changed from non-dominant to dominant. Meanwhile, the low, medium and high coverage areas decreased, and their distributions changed from dominance to non-dominance. (4) With increasing slope, distributions of the inferior, medium and high coverage areas changed from dominant to non-dominant, while the low coverage area had a dominant distribution. (5) Analyses of aspect effects revealed that the inferior coverage area was the dominant distribution in shady slopes but was non-dominant in semi-shady, semi-sunny and sunny slopes. The low, medium and high coverage areas were non-dominant in shady slopes, but dominant in semi-shady, semi-sunny and sunny slopes.

Profile distribution of soil moisture response to precipitation on the Pisha sandstone hillslopes of China

The Pisha sandstone area in China is located on the upper and middle reaches of the Yellow River, which is a region with some of the most severe soil erosion in both the Loess Plateau and in the world. Soil moisture is an important link between rainfall, surface water, and groundwater, and it plays a critical role in vegetative growth, ecosystem health, and the restoration of degraded vegetation. This study investigated the dynamic characteristics of soil moisture and its influencing factors in the hillslopes of the Pisha sandstone area using mathematical statistics and hydrochemical analysis methods. The results resolved that precipitation is the major direct source of soil moisture. Soil moisture fluctuated with precipitation, but the response time of these fluctuations was directly related to the antecedent soil moisture. Thus, while precipitation events increase the soil moisture content of the Pisha sandstone, they will not change the vertical distribution of moisture in the soil profile. The positive effect of precipitation on soil moisture was obvious in the soil layers above 50 cm, but deep soil moisture was less responsive to precipitation.