Fish-scale Pits Research Articles

Regulatory mechanism of soil and water conservation measures on understorey erosion in a subtropical hilly region

Vegetation restoration affects soil erosion by altering near soil-surface characteristics and hydrodynamic mechanisms. However, the regulatory mechanisms of vegetation restoration in reducing soil erosion under forests are not fully clear. Five soil and water conservation measures (SWCM) with different vegetation structures and characteristics were used in the pure forest of Pinus massoniana which included the grass and shrub, grass, grass and shrub + level furrow, grass, shrub and trees and grass + fish-scale pits, to analyze the impact of vegetation restoration on near soil-surface characteristics and soil erosion. The data were analyzed using Structural Equation Modeling (SEM) to find the key indicators affecting soil erosion under forest. The findings revealed that, as opposed to the control plots (CK), there were significant alterations in the near soil-surface attribute following the application of SWCM. These changes were characterized by an increase in soil porosity, soil water content, soil nutrient content, root biomass, litter, and vegetation cover, and a decrease in soil compaction, disintegration coefficient, and bulk density, with the most significant improvement occurring in 0–10 cm soil layer. The SWCM significantly reduced soil erosion, with runoff and soil loss reduction ranging from 60.46 % to 74.09 % and 67.62 % to 79.99 %, respectively. Structural equation models revealed the influence of SWCM on soil erosion. Specifically, soil water content and litter had a favourable influence on reducing soil erosion, root biomass had a direct positive impact on soil erosion, and vegetation cover directly leads to a reduction in soil erosion. Soil physical properties primarily influenced soil erosion through their effect on vegetation cover. Combining bioengineering and vegetation measures is superior at enhancing soil structure, improving nutrient content, and decreasing soil erosion compared to single vegetation measures. It is recommended to combine bioengineering with vegetation strategies to effectively curb understory forest erosion and enhance soil quality in pine forests.

Enhancing Sustainable Afforestation through Innovative Earth Auger Design: A Simulation Study in Hilly Regions

The objective of this study was to advance sustainable forestry development through the creation of mechanical equipment, taking into account forestry operational methods. A suspended automatic feeding and retracting excavation device for tree pits was engineered, and its interaction with soil was investigated by integrating the Discrete Element Method (DEM) with Multi-Flexible Body Dynamics (MFBD). Based on simulation results, the research explored the impact mechanisms of the machine on soil transportation, working load, and fatigue lifespan of the spiral blades for different terrains and operating conditions. The coupling simulation method demonstrated the potential for designing and testing forestry equipment in specific operating environments, reducing time and resource consumption for field testing. Terrain significantly influenced soil disturbance variability, while the effect of operating direction was minor. Operational parameters should consider soil and water conservation, favoring the formation of fish-scale pits. Field tests in forested areas validate the practicality of the apparatus, providing valuable insights for the operation and equipment design of earth augers in hilly regions.

Enhancing Afforestation Practices in Hilly Terrain: A Study on Soil Disturbance by Earth Augers Based on the Discrete Element Method

Afforestation operations in hilly regions are both arduous and unsafe. The mechanized afforestation method that takes into account soil and water conservation measures is deemed highly important. This paper examines the operational process and the auger’s mechanism of digging below the ground using the discrete element method (DEM). Using this model, soil disturbance parameters and reaction forces are satisfactorily predicted, exhibiting similar trends to experimental observations. This research also examines the influence of key parameters on soil disturbance and distribution patterns and analyzes the conditions and mechanisms of the formation of fish-scale pits to preserve soil and water. A field experiment of pit digging in woodland is carried out to test the performance of the device. The error rates for the actual and simulated values of the efficiency of conveying soil and the distance of throwing soil on plain terrain and slopes were 12.7% and 8.2%, and 8.6% and 15.7%, respectively. Overall, this research provides a theoretical basis for the innovative exploration, development, and optimized design of earth augers in hilly regions.

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.

Rainwater infiltration and nutrient recharge system significantly enhance the growth of degraded artificial forest in semi-arid areas with shallowly buried soft bedrock

The improvement of deep soil water and nutrient pools by maximizing in situ rainwater resource utilization and soil nutrient recharge is an important approach to promote slope vegetation restoration in the Chinese Loess Plateau, especially in areas with shallowly buried soft bedrock (Pisha Sandstone). However, the effects of integrated slope engineering measures (fish scale pits (a semicircle-shaped pit), infiltration holes, organic fertilizer) on runoff utilization, nutrient restoration and vegetation growth are not well known. This study combined rainwater infiltration and nutrient recharge (RINR), and evaluated the effect of RINR on soil water, organic carbon, total nitrogen storage and vegetation growth in a field experiment in slope artificial forestland (David peach, Prunus davidiana Franch) one year later (from 2018 to 2019). Four treatments: (1) rainwater infiltration and nutrient recharge (RINR) system (fish scale pit + infiltration hole + hole filling with 30% organic fertilizer and 70% surface loess, PHF treatment), (2) fish scale pit + infiltration hole + filling surface loess (PH treatment), (3) pure fish scale pit (P treatment) and (4) natural slope land (control, SL treatment, CK). The results showed that, compared with the control (162 mm), PHF, PH and P treatments increased the soil water storage of 0–100 cm soil layer by 37 mm, 76 mm and 30 mm, respectively. The RINR system (PHF treatment) had a significantly higher restoration effect of SOC and STN value than other treatments in all soil profiles (0–100 cm), especially at 40 cm. Compared with the control (2.42 kg/m2, 0.28 kg/m2), the RINR system 0–40 cm soil layer soil organic carbon storage increased by 320%, and total nitrogen storage increased by 129%. Meanwhile, changes in height of tree (David peach), crown width and annual branch length under RINR system increased by 0.18 m, 0.30 m and 0.33 m, respectively. Overall, the RINR system is an effective approach for enhancing the growth of degraded revegetation. This system is conducive to mitigating the water and nutrient scarcity and maintaining the persistence of vegetation restoration in arid and semi-arid areas with shallowly buried soft bedrock.

Numerical simulation and parameter optimization of earth auger in hilly area using EDEM software

Digging in hilly regions is an important measure to promote afforestation on difficult sites. In view of the working conditions to build fish-scale pit on slope, the auger mechanism of soil lifting and throwing was investigated in this study. This study utilized EDEM software to establish the operation model of the earth auger and conduct DEM (Discrete Element Method) virtual simulation experiments. A quadratic rotating orthogonal center combination test was implemented by setting the efficiency of conveying-soil (Y1) and the distance of throwing-soil (Y2) as the evaluation indices. Variance analysis and response surface optimization were performed on the virtual experimental data. The results indicated that the weight of the factors affecting the Y1 and Y2, were feeding speed > helix angle > rotating speed > slope angle, and slope auger > rotating speed > feeding speed > helix angle. The optimal parameter combination of each influencing factor was obtained. Among them, when the slope preparation was required, the optimal operating parameter combination of the auger was: Slope of 26.467°, Helix angle of 21.567°, Feeding speed of 0.1 m/s, Rotating speed of 67.408 r/min. This research provides theoretical references for the design optimization of the earth auger in hilly regions.

The effect of flow speed on the bubble dynamics: A numerical study

The Naiver-Stokes equations are utilized to investigate the bubble dynamics subjected to the flow speed in the vicinity of a rigid wall. The predictions are compared with the Gilmore method and available experimental results, and a reasonable agreement is obtained. The important flow properties, e.g., bubble morphology, collapse time, jet development, pressure wave propagation, and vorticity evolution are studied in detail. The results demonstrate that the combined effect of the flow speed and rigid wall results in the generation of oblique jet, which may contribute to the development of the fish-scale pits on the surface of the hydraulic machinery. Moreover, our results show that the impulse loads caused by the bubble collapse in moving water are lower than those in stationary water. Finally, it is indicated that the stretching term plays a major role in the vorticity both inside and outside the bubble, while the dilatation term mainly influences the vorticity inside the bubble.

Evaluating soil-water conserving performance of land management strategies for spoil tips on the Chinese Loess Plateau

Surface runoff decrease (SRD) and sediment concentration change (SCC) are accountable for sediment reduction by anti-erosion strategies. Using a design of horizontal stages, contour trenches, fish-scale pits, as well as their combinations, this study evaluated the two components for sediment reduction after the implementation of various land management strategies on steep spoil tips. The study highlighted the interactions between SRD and SCC in reducing sediment, and characterized the temporal variations of sediment-reducing capacity by SRD and SCC. Results showed that slope erosion was well controlled with control ratios of sediment yield ranging from 0.4 to 0.59, 0.2 to 0.22, for horizontal stage- and contour trench-based strategies, respectively. Sediment-reducing benefit by SRD accounted for 52%–77% of the total sediment reduction and highly determined the performance of SCC. Quadratic relationships between sediment-reducing capacity by SCC and that by SRD were observed. The function of SCC only operated when the sediment-reducing capacity by SRD reached a certain threshold. These thresholds varied greatly in the range of 0.75 kg m−3–0.91 kg m−3 and 0.61 kg m−3–0.66 kg m−3 for horizontal stage- and contour trench-based strategies, respectively. The upper limits for sediment-reducing capacity by SCC varied in the range of 0.32 kg m−3–0.44 kg m−3 and 0.63 kg m−3–0.76 kg m−3 for horizontal stage- and contour trench-based strategies, respectively. An efficiency coefficient of 55% and an M-N ratio of 1:1 indicated that sediment-reducing benefits by SRD and SCC were effectively exerted by combining contour trenches and fish-scale pits. The findings emphasized that the application of land management strategies must be considered based on particular goals to restore spoil tips. In practice, if targeted to enhancing sediment-reducing efficiency, contour trenches and fish-scale pits should be primarily considered. However, if the aim is to decrease water consumed for sediment control, then horizontal stages should be principally considered.

New Taxonomic Features of Fossil Clam Shrimp Aquilonoglypta (Spinicaudata) and its Implication for Origin of Triglyptids

The Triassic clam shrimp genus Aquilonoglypta Novojilov, 1958 was first erected based on a specimen collected from the Lower Triassic along the Laptev Sea coast of Russia. Its original diagnostic ornament was described as fish scale pits. Then, the genus was recovered in the Lower and Middle Triassic in the Ordos Basin in northwestern China. Because the Chinese specimens have punctate ornamentation, they were interpreted as the ancestor of the Jurassic triglyptids. In this study the diagnosis of Aquilonoglypta is revised following a re-examination of the Russian type specimens under a scanning electron microscope (SEM). In Aquilonoglypta growth bands near the umbo are ornamented with polygonal fine reticulation, which transitions to puncta on growth bands in the middle part of the carapace. The ornamentation on growth bands in the ventral part of the carapace clearly shows the transition from the puncta to a size-increasing fine reticulation pattern. This research result shows that Aquilonoglypta could not be the close link with triglyptids because of lacking of the fine reticulation on growth bands in the dorsal part of the carapace in the latter. On the contrary Triglypta Wang, 1984 could be more closely related to Punctatestheria Zhang et al., 2017.

Assessing the performance of conservation measures for controlling slope runoff and erosion using field scouring experiments

Slope runoff acts as a driving force for soil erosion on the Loess Plateau but is also an important water source for alleviating water shortages and maintaining vegetation growth. Identifying how to regulate runoff can help solve the problems of water shortages and soil erosion. This study aimed to determine the effectiveness of conservation measures on controlling slope runoff and soil loss in a 20° runoff plot using scouring experiments. The treatments included plots with bare slope (CK) and three typical soil and water conservation (SWC) measures—engineering measures (fish-scale pits, FSPs), vegetation measures (grass revegetation by alfalfa, GR), and agricultural measures (straw mulching, SM). The results showed that the SWC practices significantly (P < 0.05) controlled runoff and soil loss. The GR, FSPs, and SM significantly delayed runoff start time by 150–250%, 200–300%, and 250–400%, respectively, compared with CK, and reduced runoff coefficients by 25–60%, 7–50%, and 40–80%, respectively. The runoff reduction rate (RRB) and sediment reduction rate (SRB) averaged 33.6% and 82.1%, 43.7% and 76.4%, and 82.3% and 94.0%, respectively, for the GR, FSPs, and SM treatments. However, the effectiveness decreased with increasing inflow rate, especially for the FSPs as they were gradually destroyed and lost their ability to control runoff scour at 7.0 m3 h–1. The RRB and SRB were most affected by SM compared with FSPs and GR. All three SWC measures increased the Darcy-Weisbach friction coefficients (f) and reduced the velocity (V), Reynolds (Re), and Froude (Fr) numbers. Except for FSPs at 7.0 m3 h–1, all SWC treatments had a laminar flow regime and subcritical flow state. Gray correlation analysis (GRA) showed that stream power and Reynolds number had better relational degrees with erosion rate for conservation measures, followed by shear stress, indicating that they may be preferred descriptors of the erosional process. These results provide meaningful guidance on measures for preventing soil erosion on sloping farmland in the Loess Plateau.

Effects of terracing measures on water retention of pinus Tabulaeformis forest in the dryland loess hilly region of China

Terraces, which are distributed worldwide, play a key role in water conservation, vegetation restoration and agricultural production particularly in dryland mountainous environments. Due to the uncertainties caused by water balance dynamics and diverse terrace structures, different findings on the soil-water retention effects of terracing were identified across the globe. To further understand the effect of terraces on soil water retention, a field experiment was conducted between 2015 and 2019 in the dryland loess hilly region of China. The experiment compared the combination of Pinus tabulaeformis with natural slope (PS), zig terrace (PT), and fish-scale pit (PF). We found that terrace measures can greatly manipulate the hydrological dynamics and compounds. Compared with the non-terraced treatments, terrace fields reduced runoff (26.9 mm/a for PF and 34.6 mm/a for PT), increased interception (13.6 mm/a for PF and 12.1 mm/a for PT) and transpiration (14.8 mm/a for PF and 2.4 mm/a for PT) during five years of the experiment. The advantage of terracing in soil water retention was temporal, mainly during heavy rainfall periods (e.g., June to August). Zig terrace promoted soil infiltration and transpiration while fish scale pit suppressed evaporation but increased transpiration. The results indicated that temporal factor and terrace structure were essential in understanding its soil-water retention services.

Model Design and Processing of Bionic Non-smooth Surface of Fish-scale Concavity

Based on the basic methods of engineering bionics research, this paper is inspired by the desert surface morphology on the basis of the existing drag reduction microstructures, and extracts the characteristics of ecological surface drag reduction information, thereby establishing a fish-scale pit model. This paper designs and builds a diamond stamping platform to stamp and stamp copper sheets, and proposes a method that can effectively process the non-smooth surface of the fish-scale pits of the required size.

Analysis of the Influence of Pit Unit Arrangement on the Drag Reduction Performance of Fish-scale Pits

Apply Computational Fluid Dynamics (CFD) method to calculate the drag reduction effect of fish-scale pits with different arrangements under the same conditions. Through the analysis of wall shear stress, wall turbulence energy and axial velocity cloud diagram and velocity vector. It was found that the fish-scale pits can effectively reduce the shear stress and turbulent flow energy on the wall. At the same time, it was found that the bottom of the fish-scale pits formed tiny vortices flowing in the opposite direction. The “vortex cushion effect“ is combined with the “pushing effect“ caused by the friction generated by the bottom vortex, thereby reducing the friction. The research results show that the rhombus arrangement 2 can arrange a denser pit unit in the effective area to achieve a better drag reduction effect, and its drag reduction rate reaches 6.05%.

Water-Saving Soil Conservation Measures Should Be Used in Northern China: Evidence from Runoff Plot Data

Most of the current studies on soil conservation measures mainly focus on their soil control effect, neglecting their impact on water quantity. In the present study, the latest seven years (2014–2020) of monitored data from 22 runoff plots in the upstream catchment of the Miyun Reservoir, Beijing were used to evaluate the effects of slope, rainfall, and soil conservation measures on soil and water loss, and some implications were given in this water-scarce region. Excluding the impact of soil conservation measures, soil loss increased with the slope gradient and slope length. Runoff and soil loss were greatly affected by the rainfall amount and maximum 30-min rainfall intensity on the bare and cultivated slopes, or by rainfall amount and rainfall duration on almost all of the plots with soil conservation measures. The results indicated that the bare soil suffered the most severe soil loss, with a mean annual soil loss rate (SLR) of 4325 t km−2 year−1, followed by the cultivated lands without any measure, with an annual SLR of above 3205 t km−2 year−1. Contour tillage cannot effectively control soil loss on steep slopes. The vegetation measures and terrace, level bench, and fish scale pits, as well as their combinations, can decrease runoff by above 86% and decrease soil loss by 95%, respectively. Water-saving measures should be implemented in the study region. The measures, such as vegetation coverage, terracing, contour tillage, etc., should be carefully implemented on slopes. Bare and cultivated lands should further be implemented with soil conservation measures in this and similar regions in the world.

Rainwater collection and infiltration (RWCI) systems promote deep soil water and organic carbon restoration in water-limited sloping orchards

Measures that maximize in situ infiltration and utilization of rainfall are urgently needed on the Loess Plateau to minimize problems associated with drought and soil erosion, and to improve the sustainability of arid and semi-arid agricultural production in this region. Here, we present a two-year field assessment of two rainfall control systems—a rainwater collection and infiltration (RWCI) system and a semi-circular basin (fish-scale pit, FSP)—that could improve soil water storage (SWS) and deep soil organic carbon (SOC) levels in apple (Malus pumila Mill.) orchards on a slope. The RWCI system performed better than the FSP system at conserving and utilizing rainwater resources and conserving rhizosphere soil water to meet the water demand of commercial apple orchards. The RWCI system decreased the soil water storage deficit (WD) and enhanced the SOC content of the root zone due to precipitation, whereas the FSP had little effect. The RWCI system (RWCI60 and RWCI80) significantly increased soil water and SOC contents by 73 % and 81 %, respectively, relative to the control. The design depth of the RWCI system should match the root distribution of adjacent crops to make RWCI a recommended sustainable approach for maximizing the utilization of rainwater resources and the conservation of rhizosphere soil water in standing orchards. This system should help to mitigate the effect of climate change on water scarcity in arid and semi-arid regions, with potential for application in other orchard crops and regions.

Assessment of soil quality indexes for different land use types in typical steppe in the loess hilly area, China

Soil quality indexes (SQIs) are important for evaluating grassland ecosystems. The objective of this study was to assess different land-use soil quality using total data set, minimum data set (MDS), and revised minimum data set (RMDS) indicator selection methods and linear and non-linear scoring methods. Four land-use, which were including grazing grassland (GG), fencing grassland (FG), contour trench grassland (CG) and fish-scale pits grassland (FPG) in a typical steppe of loess hilly area in Ningxia, were taken as the research object. Eighteen indicators (soil bulk density; GMD: geometric mean diameter; MWD: mean weight diameter; FWC: field water-storage capacity; capillary porosity; total porosity; soil organic carbon; TN: total nitrogen; total phosphorus; AK: available potassium; available nitrogen; microbial biomass carbon; microbial biomass nitrogen; SA: sucrase activity; protease activity; CA: catalase activity; PPA: phosphatase activity; and urease activity) of soil physical, chemical, and biological characteristics of the 0–40 cm soil layer under different land use types were measured. Principal component analysis was used to select the MDS and RMDS. The results showed that three (SA, MWD, and PPA) and six (FWC, GMD, TN, AK, SA, and CA) soil indicators were included in the MDS and RMDS, respectively. The agreement values of SQIs for the linear scoring method were higher than those of the non-linear scoring method. The linear scoring-revised minimum data set was regarded as the most appropriate method to calculate the SQI because of its highest F and CV (Coefficient of Variation) values and correlation coefficient. The ranking of the SQI values of the four land use types was FG > GG > CG > FPG. The results showed that FG is the most beneficial measure for the restoration of degraded grassland, which has important guiding significance for the ecological construction of degraded grassland in the study area.

Erosion‐reducing effects of revegetation and fish‐scale pits on steep spoil heaps under concentrated runoff on the Chinese Loess Plateau

AbstractMassive spoil heaps, formed during production and construction activities, have suffered from severe soil erosion, leading to land degradation and damaging the environment. Fish‐scale pits (FSPs) and revegetation (RG) are the most common measures for controlling soil erosion on spoil heaps on the Loess Plateau. To evaluate the effects of FSPs and RG on concentrated runoff erosion, scouring‐erosion experiments were conducted on FSP plots, RG plots, and bare plots (the control) in the field on two types of spoil heaps: low gravel content in soil (LGS) and high gravel content in soil (HGS) at various inflow rates. Mass movement was the main cause of the considerable fluctuations in erosion rate and sharply increased the sediment concentration, which could exceed 800 kg m−3 and cause hyperconcentrated flows. Conversely, the FSP and RG treatments observably reduced the sediment concentration and erosion rate. The erosion‐reducing benefits (ERBs) of both the FSPs and RG treatments were significant. However, the ERB of the FSPs treatment was superior to that of the RG treatment under concentrated runoff, especially high‐intensity concentrated runoff. The ERB of the FSP treatment was on average 78.5% and 80.9% for the LGS and HGS, respectively. The ERB of the RG treatment was on average 36.4% and 56.5% for the LGS and HGS, respectively. The ERBs of the FSPs and RG treatments for the HGS were greater than those for the LGS. Moreover, gravel inhibited concentrated flow erosion. Our results provide important guidance for preventing soil erosion on abandoned spoil heaps in semiarid regions.

Effects of rainfall and terracing-vegetation combinations on water erosion in a loess hilly area, China

Terracing and vegetation restoration are the basic measures to protect soil from water erosion and to combat land degradation. However, long-term quantitative evaluation on the erosion control benefits of different terracing techniques and vegetation types are still insufficient, particularly under variable rainfall. The aim of this article, therefore, is to evaluate the coupling effects of different terracing-vegetation combinations and rainfall types (RTs) on runoff retention and erosion reduction in a loess hilly catchment of China. Six types of terracing-vegetation combinations, including leveled benches-C. microphylla (LM), fish-scale pits-P. orientalis (FO), leveled ditches-P. armeniaca (LA), zig terraces-P. orientalis (ZO), fish-scale pits-P. tabulaeformis (FT), zig terraces-P. tabulaeformis (ZT) and the corresponding plots with same vegetation cover and non-terracing measures were designed and monitored. Based on five consecutive years of monitoring data, 69 rainfall events causing runoff and erosion were observed. Rainfall eigenvalues, including rainfall amount (RA), maximum 10-min intensity (I10), maximum 30-min intensity (I30) and rainfall duration (RD) dominated water erosion processes. Surface runoff and sediment reduction benefits differed with different terracing techniques. Mean runoff coefficients (Rc) among all kinds of terracing-vegetation combinations were FT > LM > FO > LA > ZO > ZT, while mean soil loss rates (Em) among all kinds of combinations were FT > FO > LM > LA > ZT > ZO. ZT showed the highest mean runoff reduction (44.03%), while ZO generated the highest sediment reduction (39.08%). The worst performance was observed in FT. With regards to the results, it is necessary to select the optimal terracing-vegetation measures for erosion control based on the dominant rainfall eigenvalues in different areas. Overall, ZT, ZO and LA combinations are recommended, while uncertainty was detected in combinations with fish-scale pits. Suitable terracing-vegetation measures should be selected after considering the micro-relief construction, the optimization of plant disposition and the efficiency of water erosion reduction. Management should focus on the construction standards, the threshold of resisting erosion for each terracing measure, and timely maintenance of the terraces.

Effects of terracing on root distribution of Pinus tabulaeformis Carr. forest and soil properties in the Loess Plateau of China

Terracing is one of the most effective ecological engineering practices that improve soil anti-erosivity properties and support plant growth in the dryland loess hilly area and other similar regions. The objective of the study was to understand the vertical distribution of root in different terraces and their relationships with soil environmental factors in the Loess Plateau of China. The vertical root distribution in the 0–400 cm soil profile, fine root distribution and soil moisture, soil nutrients (soil organic carbon, total nitrogen, and total phosphorus) and soil anti-erosivity in 0–160 cm soil profiles (every 20 cm for one layer) were investigated using the ground-penetrating radar and soil coring methods in a Pinus tabulaeformis Carr. forest under three terrace types during the growing season of 2018. We highlight several key findings here. First, level benches had the highest root density (18.14 kg m−2), followed by fish-scale pits (13.95 kg m−2) and reverse-slope terraces (9.84 kg m−2), as well as the highest soil water content, nutrients and soil stability. Second, terracing caused significant differences in root distribution (P < 0.05), leading to the variation of soil moisture, nutrients, anti-erosivity (explained over 80% variation) and reduced spatial heterogeneities of soil water content and nutrients. Third, fine root density parameters attained the highest values in the topsoil (0–40 cm soil layer) and decreased with increasing soil depth in all the three terrace types (P < 0.05). Finally, fine roots contributed to soil water improvement, nutrient promotion and soil stabilization, while higher density of coarse roots might consume soil nutrients and reduce soil anti-erosivity. We thus suggest that level benches could be a more suitable terracing measure for plantation of P. tabulaeformis Carr., and to achieve soil melioration and fixation during the ecosystem restoration process in the Loess Plateau and other arid and semiarid regions.

Fish‐scale pit effects on erosion and water runoff dynamics when positioned on a soil slope in the Loess Plateau region, China

AbstractSoil moisture construction is a very important way to reduce soil erosion and maintain crop growth in arid and semiarid regions of China. A microcatchment technique for soil erosion prevention widely used on soil slopes on the Loess Plateau are fish‐scale pits (FSPs). This technique is combined with afforestation techniques to store runoff, interrupt the dynamics of soil erosion, and help mitigate frequent water deficiencies encountered by forest trees. This study investigated the effects of FSPs on soil erosion dynamics including rill formation and runoff. A three‐dimensional (3D) laser scanner was used to evaluate the erosion resistance of a 15° slope treated with FSPs arranged in a triangular pattern and the hydraulic characteristics of the flow on this slope during several intermittent simulated rainfall events. The following results were obtained. (a) The FSP‐treated slope displayed eight progressive stages of erosion: splash erosion, sheet erosion, scouring by water streams, formation of the scour pits, rill erosion, down‐slope erosion, up‐slope erosion, and collapse of the pit walls. (b) As the rainfall duration increased, the runoff velocities at various locations on the slope fluctuated, but generally, the runoff velocities were significantly higher in the down‐slope positions than for the midslope and upslope positions. When the cumulative rainfall duration reached approximately 58 min and the total rainfall reached approximately 88.5 mm, the ability of the FSPs to intercept and store runoff rapidly decreased. In the first two rainfall events, both the runoff reduction benefits (RRB) and sediment reduction benefits (SRB) were positive, but following the third rainfall event, the SRB and RRB of the FSPs were negative. The accuracy of erosion parameters extracted using the 3D laser equipment and the ArcGIS software in comparison with the measured rill erosion parameters all less than 10%. The relative error between the measured sediment and the calculated sediment is within 5.66–22.13%. (c) During the rainfall process, the flow on the upslope was constantly in the laminar regime, but after the FSPs were completely filled with water, the laminar flow on the downslope transitioned into a turbulent flow. (d) As the cumulative rainfall duration increased, the degree of topographic relief and the number of rills increased, as did the measurements of surface roughness and flow resistance. In conclusion, the microcatchment methods reduced the rill erodibility and enhanced the soil's resistance to concentrated flow erosion.