Coal extraction is associated with the creation of waste dumps, in which the soils are extremely depleted owing to dilution of the existing topsoil by mixing with the subsoil; however, the evolution mechanism of such soils re-mains unclear. Here, we investigated the changes in the soil properties over time, focusing on organic acid content in restoration areas following coal mining. The soil of three soil depths (0-10, 10-20, and 20-30 cm) from natural land and three waste dumps with primary succession ages of 5 (R5), 10 (R10), and 20 (R20) years in the Heidaigou open-pit coal mine of Northwest China, were analyzed to examine changes in the soil properties and to highlight relationships between these properties. Results showed soil pH, total nitrogen, alkali -hydrolyzable nitrogen, available phosphorus, soil organic matter, and organic acid increased with increasing restoration age. However, only soil organic matter and organic acid were influenced by soil depth and the interaction of restoration age and soil depth. Moreover, the total phosphorus content did not alter with the restoration age, soil depth, or their interactions. In contrast, the N:P ratio increased with increasing restoration age, indicating that the total phosphorus content might restrict restoration. The alkali-hydrolyzable nitrogen was significantly correlated to available phosphorus, acetic acid, soil organic matter, and pH. The available phos-phorus was significantly correlated to the oxalic acid, while the pH and soil organic matter significantly influ-enced the acetic acid. Our findings provide theoretical support to improve the soil quality and may assist in restoration in coal dam areas.

Global climate change and the increasing population have increased the difficulties associated with grain production. Several measures have been established to maintain a high crop yield, while preserving or increasing soil health, including biochar application to soil, and producing new complex soil with soil amendment application, e.g., biochar and soft rocks. However, previous studies have focused on the effect of complex soil on a single crop but have not considered crop rotation. In this study, field plots with foxtail millet cultivated for two years under biochar and soft rock application were selected for licorice cultivation to detect the effects of biochar and soft rock application on soil properties and licorice yield. The results showed that the biochar-treated plot had the highest licorice biomass (251.76 g/m2), followed by the combined biochar and soft rock treatment, and that the soft rock and control treatments had the lowest licorice biomass (97.65 g/m2). Plants in biochar-treated plots had the highest liquiritin and glycyrrhizic acid contents, followed by those under soft rock treatment. Soft rocks and biochar increased the soil catalase activity, organic matter, oxalic acid, tartaric acid, formic acid, and available phosphorus (AP). Correlation analysis showed that the licorice biomass was significantly positively correlated with oxalic acid and AP and negatively correlated with soil pH. AP was positively correlated with catalase activity and oxalic acid (p < 0.05) and negatively correlated with soil pH (p < 0.05). Therefore, it can be concluded that the addition of biochar and soft rocks for two years could increase soil organic acid contents (especially that of oxalic acid), which function to reduce soil pH, increase soil AP content, and enhance licorice biomass.

To cope with the growing population, there is a growing demand for more land to be rendered cultivable. A complex soil created by applying soft rocks into sandy soil can be cultivated. However, the strong water-retaining ability and extreme poverty in nutrients of this complex soil has a negative effect on plant growth. To solve this problem, a complex of microbes and bacterial manure (BM) was added to the complex soil. The soil column culture test was used to detect the influence of BM application on soil bulk-density and infiltration parameters, and a pot experiment was conducted to evaluate its effect on the physical and chemical properties of soil, and ryegrass growth. The addition of 0.15% of BM to the complex soil decreased soil bulk-density, and increased the wetting front migration distance and soil hydraulic conductivity. The BM application also increased soil enzyme activities, which increased the available nitrogen and phosphorus content. As a result, BM increased the ryegrass root and shoot biomass. Overall, this study indicates that BM could be used as an eco-friendly sandy soil conditioner for improving the quality of complex soils, thereby, sustaining agricultural production in arid and semi-arid regions.

以退耕还林实施效果的显现期(2003-2011年)为背景,采用指纹识别技术反演淤地坝泥沙来源及小流域侵蚀产沙演变.结果显示,9年间,沟道、人工林、灌木地和缓坡耕地的平均泥沙贡献率分别为40％、25.9％、20.3％和13.8％,淤地坝泥沙主要来自沟道.根据各源地泥沙贡献率及其与面积占比的关系,确定小流域中不同土地利用类型的平均侵蚀强度由大到小依次为沟道>缓坡耕地>人工林>灌木地.随着退耕年限的增加,人工林泥沙贡献率出现小幅增长,沟道侵蚀有下降趋势,但沟道仍为黄土高原丘陵区侵蚀泥沙的主要来源地.退耕还林时期栽植的灌木有效减少了侵蚀作用,缓坡耕地则仍需辅以相应的水土保持措施.

为研究植物根系对三峡库区消落带紫色土崩解性能的影响,通过设置裸土对照(CK)和根系土样(RS)2种处理模式试验条件,利用自制崩解装置研究不同坡度下试样崩解过程,对比分析植物根系对紫色土崩解过程和崩解量的影响.结果 表明:随着崩解时间的增加,CK和RS这2种处理模式下累计崩解量均呈现先快速增加之后缓慢增加并趋于平稳的趋势,而崩解速率随崩解却呈现不同的变化趋势.植物根系能够显著减小各时段的累计崩解量和前期崩解速率.坡度增加能够增加2种模式下的累计崩解量和最大崩解速率.中低坡度(10°和20°)时植物根系对崩解的影响较大,而在高坡度(30°)时影响减小.与CK相比,植物根系能够降低50％以上的崩解量,表明植物根系能够有效减缓崩解的发生.

The information of aggregate disintegration mechanisms during splash erosion is scant. This study was conducted to quantify contributions of the mechanisms of aggregate disintegration to splash erosion. Six soils with five soil textures were used. Soil aggregate stability was determined by the Le Bissonnais (LB) method. Deionized water was used to simulate the combined effect of slaking and mechanical disaggregation, while ethanol was used to estimate the sole contribution of the mechanical breakdown. Simulated rainfall with intensity of 60 mm h(-1) was applied at five fall heights (0.5 m, 1 m, 1.5 m, 2 m and 2.5 m) to achieve different levels of rainfall kinetic energy. The results indicated that slaking caused the most severe aggregate breakdown, and followed by mechanical breakdown, while chemical dispersion in slow wetting with deionized water was the weakest breakdown mechanism. The splash erosion rates due to the effects of slaking and mechanical breakdown increased with an increase in rainfall kinetic energy. The contributions of the slaking (mechanical breakdown) to splash erosion decreased (increased) as rainfall kinetic energy increased. The contribution of mechanical breakdown had a power function relation with rainfall kinetic energy, and had the most significant correlation with RSI (relative slaking index)/RMI (relative mechanical breakdown index). A power and a linear function could be used to describe the relationships between the contributions of mechanical breakdown with rainfall kinetic energy and RSI/RMI, respectively, which could be used to estimate the contribution of mechanical breakdown. The results of this research would be helpful to improving the soil erosion prediction models.

Tracer techniques, such as the multi-element tracer technique, have been studied in recent decades to determine their effectiveness in estimating the sediment sources in the Loess plateau. The first step in studying sediment sources using the multi-element tracer technique is to screen for indicating factors; however, few studies have presented a reference of the trace elements that can be used in the study of sediment sources in the Loess plateau. Furthermore, because the loess deposition resulted from the long-term operation of wind power and loess is generally homologous, significant differences usually do not occur among the concentrations of the loess’ chemical elements. To determine obvious differences in the chemical element concentrations, additional factors must be selected. For our study site, we selected a typical small closed watershed in the Peng-yang region of the Ningxia Province in China, and 20 cm surface soil samples were collected at each of the following five geographical locations: (i) ridge, (ii) hill slope, (iii) shoulder line of the valley, (iv) channel slope and (v) area in front of the dam. A neutron activation analysis was then performed, and 31 major soil constituents were detected in the standards and soil samples. The results showed that marked differences occurred among the concentrations of Eu, Fe, Al, Co, Cs, Hf, Sc, Th, Cr, Rb and Mn. And combining a previous study, we suggest that the soil nutrient index, soil magnetic susceptibility and soil concentrations of Al, Eu, Cs, Hf, Sc, Co, Th, Cr, Rb, 137 Cs, 7 Be, 210 Pb and 226Ra can be used as indicating factors in the study of sediment sources in the Loess plateau.

Using hydraulic parameters is essential for describing soil detachment and developing physically based erosion prediction models. Many hydraulic parameters have been used, but the one that performs the best for describing soil detachment on steep slopes when the lateral expansion (widening) of rills is not limited has not been identified. An indoor concentrated flow scouring experiment was performed on steep loessial slopes to investigate soil detachment rates for different flow rates and slope gradients. The experiments were conducted on a slope-adjustable plot (5 m length, 1 m width, 0.5 m depth). Sixteen combinations of 4 flow rates (10, 15, 20, and 25 L/min) and 4 slope gradients (17.6%, 26.8%, 36.4%, and 46.6%) were investigated. The individual and combined effects of slope gradient and flow hydraulic parameters on soil detachment rate were analysed. The results indicated that soil detachment rate increased with flow rate and slope gradient. Soil detachment rate varied linearly and exponentially with flow rate and slope gradient, respectively. Multivariate, nonlinear regression analysis indicated that flow depth exerted the greatest influence on the soil detachment rate, followed by unit discharge per unit width, slope gradient, and flow rate in this study. Shear stress and stream power could efficiently describe the soil detachment rate using a power equation. However, the unit stream power and unit energy of the water-carrying section changed linearly with soil detachment rate. Stream power was an optimal hydraulic parameter for describing soil detachment. These findings improve our understanding of concentrated flow erosion on steep loessial slopes.

Understanding changes in Holocene erosion is essential for predicting soil erosion in the future. However, the quantitative response of natural erosion to Holocene climate change is limited for the Loess Plateau of China. In this study, two soil profiles were investigated on the Luochuan and Yanchang sites in the central Loess Plateau of China; and four climate indicators, i.e. magnetic susceptibility, calcium carbonate content, total organic carbon content, and clay content (<0.005mm), were analyzed to describe climate change. The equations fitted using modern pedogenic susceptibility, precipitation, and temperature were used to quantitatively reconstruct paleoprecipitation and paleotemperature in the Holocene. The current relationship between soil erosion intensity and precipitation was determined and used to estimate historical erosion. Results indicated that climate was coldest and driest between 12,000 and 8500cal.yrBP, and became warmer and wetter during 8500 to 5500cal.yrBP. The warmest and wettest climate was from 5500 to 3000cal.yrBP and was getting colder and dryer over the last 3000years. Holocene erosion intensity changed with fluctuation of mean annual precipitation, and these changes were different on both sites. The peak erosion values were 20,966t·km−2·yr−1 in 7500cal.yrBP and 21,148t·km−2·yr−1 in 3300cal.yrBP on the Luochuan and Yanchang sites, respectively. Furthermore, more severe soil erosion with a faster increase was estimated on the Yanchang site than Luochuan site with a range between 6547 and 11,177t·km−2·yr−1 during the last 1800years. This study proposed a new method to quantify historical soil erosion triggered by climate change, which not only can derive detailed soil erosion intensity change with variation of climate, but also provide a way to compare soil losses between different areas.

Summary The contributions of different mechanisms of aggregate breakdown to splash erosion are still obscure. This study was designed to investigate the effects of various mechanisms of soil disaggregation on splash erosion. Loamy clay, clay loam and sandy loam soil types were used in this research. Soil aggregate stability was determined by the Le Bissonnais method. Deionized water was used to simulate the combined effect of slaking and mechanical disaggregation, whereas alcohol was used to estimate the contribution of mechanical breakdown only. Simulated rain with an intensity of 60 mm hour −1 was applied at five heights (0.5, 1, 1.5, 2 and 2.5 m) to achieve different amounts of rainfall kinetic energy. The results indicated that the rate of splash erosion increased with the increase in rainfall kinetic energy in tests with both deionized water and alcohol. The rates of splash erosion for three types of soil followed the order of loamy clay soil < clay loam soil < sandy loam soil, but the mean weight diameter (MWD) of disintegrated aggregates followed the reverse order. The rates of splash erosion from the effects of slaking and mechanical breakdown increased with an increase in rainfall kinetic energy. The contributions of slaking and mechanical breakdown to splash erosion decreased for the former, whereas it increased for the latter as rainfall kinetic energy increased. The slaking effect contributed more than 50% of splash erosion. The rates of contribution of slaking and mechanical breakdown to splash erosion depended on rainfall kinetic energy and soil type. Highlights Contributions of different mechanisms of aggregate breakdown to splash erosion remain obscure. Alcohol was used to simulate the effect of mechanical breakdown only. Slaking contributed more than 50% of splash erosion. Contributions by mechanisms of aggregate breakdown depend on rainfall kinetic energy and soil type.

Sediment discharge significantly decreased in the Yellow River because of the effect of the ‘grainfor-green project’ (GGP).The typical watershed parsing method was applied to obtain the sediment yield and analyze the variation of the annual erosion modulus in a typical watershed in the loess hilly-gully region between 2003 and 2011.The results indicated that sediment yield from the watershed declined dramatically,and the average erosion modulus was less than 500 t/(km2 · a),which was 8.3％ of that before the implementation of GGP.Moreover,when excluding the data in 2003 because of the influence of the beginning of dam implement,the average erosion modulus during 2004-2011 was 144.93 t/(km2 · a),which was only 2.4％ of that before the implementation of GGP,suggesting that there was a mild erosion in this watershed after the GGP.This study proved the significance of the effects of controlling sediment yield of the GGP,and it may help the planners and managers to make proper decisions for the control of soil erosion from watersheds under similar conditions.

The new built multi-stair slope in gully of loess area is susceptible to soil erosion.We used the simulated rainfall experiment to examine the relation among soil and water conservation measures,rainfall intensity and the phenomenon of soil erosion on multi-stair slope in loess area and observed the development process of soil erosion.The results show that the extreme weather conditions (rainfall intensity 120 mm/h) and upslope runoff are two key factors leading to soil erosion on multi-stairs slope in loess area.When the rainfall intensities ranged between 60 mm/h～90 mm/h,the sediment yield rate influenced by the rainfall was stable.There was no obvious difference between phenomena of soil erosion and the slope without obvious damage,When the rainfall intensity was 120 mm/h the sediment yield rate rose quickly,the phenomenon of soil erosion was obvious.The reverse slope measure can effectively reduce the sediment yield by 58.4％,35.2％,62.1％ and reduce the runoff by 69.6％,26.6％,60.8％,respectively,under the rainfall intensities of 60 mm/h,90 mm/h and 120 mm/h.At the same time,the erosion rate decreased.Water test was used to simulate the slope without drain measures.The results show that drain measures can effectively reduce the sediment yield by 92.7％,and at the same time changed the development phenomenon of erosion,the drain measure turned the erosion phenomenon from rill erosion to sheet erosion.From the point of view of water and sediment reduction,the drain measures and reverse slope measures are both effective measures to prevent water loss and soil erosion on multi-stair slope in loess area.

Previous research on sediment transport capacity has been inadequate and incomplete in describing the detachment and transport process of concentrated flows on slope farmlands during rill development. An indoor concentrated flow scouring experiment was carried out on steep loessial soil slope with erodible bed to investigate the sediment transport capacity under different flow rates and slope gradients. The results indicated that the sediment transport capacity increases with increasing flow rate and slope gradient, and these relationships can be described by power functions and exponential functions, respectively. Multivariate, nonlinear regression analysis showed that sediment transport capacity was more sensitive to slope gradient than to flow rate, and it was more sensitive to unit discharge per unit width than to slope gradient for sediment transport capacity in this study. When similar soil was used, the results were similar to those of previous research conducted under both erodible and non-erodible bed conditions. However, the equation derived from previous research under non-erodible bed conditions with for river bed sand tends to overestimate sediment transport capacity in our experiment.

A soil aggregate represents a key soil structural unit that influences several physical soil properties such as water infiltration, runoff and erosion. The relationships between soil aggregate stability and interrill and rill erodibility are critical to process-based erosion prediction models yet remain unclear, likely due to the difficulty of distinguishing between interrill and rill-eroded sediment during the erosion process. This study was designed to partition interrill and rill erosion rates and relate them to the aggregate stability of Ultisols in subtropical China. Six kinds of rare earth elements (REEs) were applied as tracers mixed with two cultivated soils developed over Quaternary red clay or shale at six slope positions. Soil aggregate stability was determined by the Le Bissonnais (LB)-method. Simulated rainfall of three intensities (60, 90 and 120mmh−1) was applied to a soil plot (2.25m long, 0.5m wide, 0.2m deep) at three slope gradients (10°, 20° and 30°) for a duration of 30min after runoff initiation. The results indicated that rill and interrill erosion rates in the soil developed over shale were considerably greater than those in the soil developed over Quaternary red clay. Equations using an aggregate stability index As to replace the erodibility factor of interrill and rill erosion in the Water Erosion Prediction Project (WEPP) model were constructed after analysing the relationships between estimated and measured rill and interrill erosion data. The results show that these equations based on As have the potential to improve methods for assessing interrill and rill erosion erodibility synchronously for subtropical Ultisols by using an REE tracing method.

[Objective] Soil aggregate is a basic unit in soil structure and its stability is an important index describing soil's resistance to breakdown in the process of water erosion.However,in splash erosion how raindrops function through mechanical impact and slaking effect on soil aggregates and what are the mechanisms and contribution rates of the two are still unclear.This study is oriented to investigate effects of mechanical impact and slaking effect of rain drops on breakdown of soil aggregates during splash erosion.[Method] A series of indoor splash erosion experiments were carried out in the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau,Institute of Soil and Water Conservation,Chinese Academy of Sciences and Ministry of Water Resources,China.Samples of Loessal soil (Sandy loamy soil) collected from Yan'an and Lou soil (Loamy loam soil) collected from Yangling in Shaanxi province,two typical soils in the Loess Plateau,were tested in the experiments.A home-made needle type rainfall simulator,consisting of three parts:water supply apparatus,needle nozzles and support frame,was used to simulate rain drops of ultra-pure water and alcohol to determine effect of mechanical impact alone and joint effect of mechanical impact and slaking on soil aggregates,separately.The splash erosion experiments were designed to have two type of soils and 5 treatments in height for rain drops to fall,i.e.0.5 m,1 m,1.5 m,2 m and 2.5 m.[Result] Results show that in the two soils soil aggregate stability exhibited an order of MWDfw ＜ MWDws ＜ MWDsw.Slaking effect (Fast wetting) was the major mechanism of the breakdown of soil aggregates,and followed by mechanical disturbance (Wetting and Shaking),and then chemical slaking (Slow Wetting) in the end.The soil of loamy clay was higher than the soil of sandy loam in RSI (Relative Slaking Index),suggesting the former is more susceptible to slaking effect than sandy loam soil,while the latter is more to mechanical impact.In splash erosion,when rain drops fell from the same height,splash erosion rate was lower in loamy clay soil than in sandy loam soil,and splash erosion rate caused by rain drops of pure water through the joint effect of mechanical impact and slaking was higher than that caused by drops of alcohol through mechanical impact alone in both soils.Regardless of pathways of the rain drops affecting soil aggregates,splash erosion rate increased with rising kinetic energy of the rain drops,and power function could be used to well describe the relationship between splash erosion rate and rain drop kinetic energy.The splash erosion rates caused by slaking effect and/or mechanical impact of rain drops both increased with rising rain drop kinetic energy or rising height where rain drops fell from.The slaking effect contributed more than 50％ to the splash erosion rate,indicting slaking effect was the main factor causing aggregate breakdown effect,but the slaking effect decreased in contribution to splash erosion rate with rising rain drop kinetic energy,while the mechanical impact acted reversely.In the cases the same in rain drop kinetic energy,the contribution of slaking effect was higher in loamy clay soil than in sandy loam soil,but that of mechanical impact was just the reverse.[Conclusion] Contribution rates of slaking effect and mechanical impact vary with rain drop kinetic energy and soil type.All the findings in this study could be of great significance to evaluation of aggregate stability and to in-depth understanding of the mechanism of aggregate breakdown during splash erosion.

Understanding soil erosion processes at different landscape positions is important in order to predict and control watershed soil losses. Rare earth elements (REEs) can be used to trace eroded soil sources but their efficacy may be soil dependent. We constructed a miniature watershed model of a small watershed located in the Three Gorges Area of China, and used oxides of eight REEs to trace the erosion of a purple soil. The miniature watershed was divided into eight regions containing a different landform type as a potential sediment source. A different REE was applied in each region. Redistributions of the REEs under three successive simulated rainfall events with intensities of 1.0, 1.5 or 2.0mmmin−1 were examined. The percentage contribution from each region to the total soil loss from the watershed fluctuated relative to landform type during the three rainstorms. Contributions from the lower main gully decreased before stabilizing, while those from the upper main gully increased before decreasing, and those from other sources all increased before stabilizing. Overall, the contribution of the gully system, comprising main and branch gullies, was greater than that of the slopes. Contributions from the gully system tended to decrease with increases in rainfall intensity and rainstorm duration while those from the slopes increased. A comparison of the calculated and actual soil loss masses indicated that the accuracy of the REE tracing method was less for the coarse textured purple soil than those previously found for fine textured soils. The increased errors, likely due to the assumption used in the calculation that there is no particle size selectivity during erosion, needs to be addressed. This pilot study provided a technical reference for the use of REEs in monitoring sediment sources from a natural watershed, and a theoretical basis for soil conservation in the Three Gorges Area.

The use of rare earth elements (REEs) as tracers provides a high-precision method for quantitative determinations of soil particle movement in soil erosion studies. In this study, a new calculation method was developed and tested to improve the precision of the REE tracing method and to expand the application of this method to areas with coarse-textured soils.

Rill erosion caused by concentrate flow is one of the main erosion types on cultivated slope in the Loess Plateau. It is necessary to research on the response of concentrate flow hydrodynamic characteristics for a better understanding of rill erosion mechanism. However, the optimal runoff hydrodynamic parameter for estimating detachment rate was still ambiguous. An indoor concentrate scouring experiment was carried out was carried out in the State Key Laboratory of Soil Erosion and Dryland arming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, China to investigate the response of runoff hydrodynamic characteristics to detachment rate under concentrate flow condition with different inflow rates and slope gradients. Loessal soil collected from Yanan (35°21′-37°31′ N and 107°41′-110°31′ E) in Shaanxi province, a kind of typical soil in the Loess Plateau, was prepared for this research. The experiments were applied to a soil plot with 5 m long, 1 m wide and 0.5 m deep. Packing was carried out layer by layer to attain the desired uniform bulk density (about 1.25 g/cm-3) with 40 cm in depth. The bottoms of the boxes were perforated and covered with a layer of 10 cm sand under the gauze to facilitate even drainage of percolating soil water. After packing, the soil was watered to saturation with an electric sprayer to reduce the variability caused by packing. Four flow rate (10, 15, 20 and 25 L/min) combined with four slope gradient (10°, 15°, 20° and 25°) were designed for this research. The experiment lasted for 10 min after runoff initiation. Runoff and sediments were collected in a series of plastic containers at intervals of 1 min throughout the 10 min. The volume of water in each container was measured, and the sediment was dried in an oven and weighed. The flow velocity was measured by dye-tracing technique within the 1-4 m away from the bottom and the flow width was also measured at 4 sections between 0.5-4.5 m to estimate flow depth at every minute during the experiment.The relations between runoff hydrodynamic characteristics, including shear stress, stream power, unit stream power and unit energy of water-carrying section, and detachment rate were analyzed. The results showed that all the mean and instantaneous runoff hydrodynamic characteristics factors fitted the detachment rate well with different regressions equations except instantaneous unit energy of water-carrying section. The mean runoff hydrodynamic characteristics factors were better than those of average values for fitting with detachment rate. The optimal runoff hydrodynamic characteristics factor in our research was mean stream power because it was of the largest determination coefficient 0.97. The curve of linear regressions of mean shear stress and stream power with detachment rate became ascended because of collapse during the experiment process, which also led to a negative value for corresponding critical shear stress and stream power. By comparing results with that from a published paper that only considered the flow effect on soil surface in the same soil, the detachment rate directly estimated based on mean stream power were more reasonable than those estimated based on mean shear stress. The collapse could account for 90.93% of the detachment rate, indicating an important role of collapse during rill development process. The results provide valuable information for a better understand of the response of concentrate flow hydrodynamic characteristic factors to detachment rate and its corresponding erosion mechanism.

The process of soil development can be studied quantitatively by analyzing the chronofunctions of soil based on its physical and chemical characteristics, which provide a basis for establishing soil development models. In this paper, the physical and chemical characteristics as well as the 14 C age of Holocene dark loessial soil profiles found in Luochuan and Yanchang areas on the central Loess Plateau were analyzed to establish soil chronosequences. Then, linear functions, logarithmic functions, and third-order polynomials were used to fit the soil chronosequences to establish the soil’s chronofunctions, which were verified both theoretically and empirically. In the two soil profiles, third-order polynomials could best fit the age of clay (<0.002 mm), silt (0.002–0.02 mm), and sand (0.02–2 mm), and their trends reflected the characteristics of dark loessial soil layers. The changes of soil organic carbon and pH in relation to soil age could be fitted by logarithmic functions. Lastly, third-order polynomials could best fit changes in the soil’s CaCO 3 content and Fe/Zr, K/Zr, P/Zr, Na/Zr and Mg/Zr ratios with soil age, which represented the migration processes of CaCO 3 and various elements in the soil.