Land preparation (e.g., leveled ditches, leveled benches, adversely graded tableland, and fish-scale pits) is one of the most effective ecological engineering practices to reduce water erosion in the Loess Plateau, China. Land preparation greatly affects soil physicochemical properties. This study investigated the influence of different land preparation techniques during vegetation restoration on soil conditions, which remained poorly understood to date.Soil samples were collected from depths of 0–10, 10–20, 20–40, 40–60, 60–80, and 80–100 cm, in the typical hilly watershed of Dingxi City, Loess Plateau. Soil bulk density (BD), soil organic matter (SOM), and total nitrogen (TN) were determined for different land preparations and vegetation type combinations. Fractal theory was used to analyze soil particle size distribution (PSD).(1) The effect of land preparation on soil properties and PSD varied with soil depth. For each land preparation category, SOM and TN values showed a significant difference between the top soil layer and the underlying soil depths. (2) The fractal dimension of PSD showed a significant positive correlation with clay and silt content, but a significant negative correlation with sand content. (3) The 20 cm soil layer was a boundary that distinguished the explanatory factors, with land preparation and vegetation type as the controlling factors in the 0–20- and 20–100-cm soil layers, respectively.Land preparation and vegetation type significantly influenced soil properties, with 20 cm soil depth being the boundary for these two factors. This study provided a foundation for developing techniques for vegetation restoration in water-limited ecosystems.

Terracing has long been considered a strategy for soil and water conservation in many mountainous regions of the world. However, the effectiveness of terracing is limited by many factors, such as climate, soil properties, topography, land use, culture, demography and socioeconomic status. The aim of this critical review is to evaluate the roles of terracing on water erosion control in China. A meta-analysis of 601 runoff and 636 sediment observations involving a diversity of terrace structures was conducted. These 1237 observations involved level terraces, slope-separated terraces, slope terraces, zig terraces, fanya juu terraces and half-moon terraces, wide geographical locations within China, a diversity of land uses from forests to bare land, and a slopes ranging from 3° to 35°. The results confirmed that terracing significantly and positively affected water erosion control. In terms of different terrace structures, bench terraces were superior with respect to runoff and sediment reductions. Land use also played a crucial role in the efficiency of erosion control; terraces associated with tree crops and forests conserved the greatest amount of soil and water. In addition, a significant positive correlation between slope gradient (3°–15° and 16°–35°) and the effect of terracing on water erosion control was observed with the greatest decreases in water erosion occurred at slopes of 26°–35° and 11°–15°. This study revealed the effectiveness and variations of terracing with respect to water erosion control at the national scale and can serve as a scientific basis for land managers and decision makers. However with increasing urbanization, terrace abandonment increases as does the loss of place-based knowledge regarding terrace construction and maintenance.

Terracing has long been considered one of the most effective measures for soil water conservation and site improvement. However, few studies regarding the quantitative effects of terracing on soil water dynamics and vegetation water use efficiency were reported. To fill these knowledge gaps, in this study, soil water content and canopy transpiration from 2014 to 2015 were monitored in both terrace and slope environments in the semiarid Loess Plateau of China. Results showed that terracing had positive influences on soil water content among layers. Mean soil water content of the terrace site was 25.4% and 13.7% higher than that in the slope site in 2014 and 2015, and canopy transpiration at the terrace site increased by 9.1% and 4.8%, respectively. Canopy conductance at the terrace site was 3.9% higher than that at the slope site and it decreased logarithmically with the increase of vapor pressure deficit. This study highlighted the critical role of terracing in soil-water improvement and water-stress mitigation in semiarid environments. Thus, terracing has the potential to enhance sustainable vegetation restoration in water-limited regions.

•Water erosion on gentle slopes remains far higher than the acceptable criterion.•Potato cultivation results in higher erosion rates than other crops on sloping land.•Potato farming using additional measures should be conducted on terraces.•Crop-shrub intercropping and farmland abandonment contribute to erosion control.•Effects of CRTs on water erosion are also influenced by rain features.Cultivation on steep land has long been blamed as a major contributor of water erosion in many fragile regions of the world. Soil and water loss from gentle slopes, however, are always subjectively considered less important and are even neglected in practice. In this study, 21 plots including seven crop-rotation types (CRTs) under three different slight gradients (10°, 15°, 20°), were established in Dingxi, a typical semiarid hilly loess area in China. Eight consecutive years of erosion data under different gentle-slope cultivation conditions were compared and analyzed. The most interesting and key finding is that water erosion remained far higher on slopes with gradients of less than 20° than the tolerable criterion, even when some CRT measures and field treatments (e.g., contour cultivation, stiletto, minimum tillage, and crop-shrub intercropping) were implemented. Newfield techniques targeting erosion control on gentle slopes should be developed. Secondly, compared with other crop species, potato cultivation under sloping conditions was confirmed to cause the highest soil and water loss and should be strictly forbidden at large scales. Being a major source of income for local farmers, potato plantation under terracing conditions, rather than on slopes, is strongly recommended as the first choice for achieving the double advantages of erosion control and farmer income. Thirdly, water erosion on gentle slopes was reduced significantly when different CRTs coupled with land-closure treatments (e.g., farmland abandonment, leaving artificial grassland under natural succession, and consecutive fallows) were conducted simultaneously. This result confirms that these measures are effective for conserving soil and water, and are feasible in practice. Finally, water erosion depended significantly on the timing and proportion of rainstorms in certain periods. The sensitivity of water erosion to natural rainfall, however, was also dependent on the specific surface status. In summary, a higher occurrence of rainstorms coupled with crops that have poor resistance to erosion (e.g., potato, flax, and wheat) and up–down cultivation will certainly accelerate runoff and erosion on slopes, whereas natural succession without human disturbance or appropriate CRTs with contour farming practices can markedly reduce water erosion rates.

Soil moisture is an effective water source for plant growth in the semi-arid Loess Plateau of China. Characterizing the response of deep soil moisture to land use and afforestation is important for the sustainability of vegetation restoration in this region. In this paper, the dynamics of soil moisture were quantified to evaluate the effect of land use on soil moisture at a depth of 2 m. Specifically, the gravimetric soil moisture content was measured in the soil layer between 0 and 8 m for five land use types in the Longtan catchment of the western Loess Plateau. The land use types included traditional farmland, native grassland, and lands converted from traditional farmland (pasture grassland, shrubland and forestland). Results indicate that the deep soil moisture content decreased more than 35% after land use conversion, and a soil moisture deficit appeared in all types of land with introduced vegetation. The introduced vegetation decreased the soil moisture content to levels lower than the reference value representing no human impact in the entire 0–8 m soil profile. No significant differences appeared between different land use types and introduced vegetation covers, especially in deeper soil layers, regardless of which plant species were introduced. High planting density was found to be the main reason for the severe deficit of soil moisture. Landscape management activities such as tillage activities, micro-topography reconstruction, and fallowed farmland affected soil moisture in both shallow and deep soil layers. Tillage and micro-topography reconstruction can be used as effective countermeasures to reduce the soil moisture deficit due to their ability to increase soil moisture content. For sustainable vegetation restoration in a vulnerable semi-arid region, the plant density should be optimized with local soil moisture conditions and appropriate landscape management practices.Highlights► Deep soil moisture decreased more than 35% after vegetation restoration. ► Different introduced vegetations may produce similar soil moisture pattern. ► High planting density is the key factor in soil moisture deficit. ► Landscape management can increase deep soil moisture effectively. ► Scientific management should be considered for sustainable vegetation restoration.