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[Objective] The effects of different long-term vegetation restoration types on differences of soil surface infiltration and water storage in the loess gully region of Western Shanxi Province were studied in order to screen and enhance the ecological benefits of natural vegetation restoration as well as artificial vegetation restoration in Loess Plateau in the future, thereby providing a scientific reference for an in-depth understanding of the ecological benefits of vegetation restoration. [Methods] We measured infiltration in the top 30 cm of soil under four types of restored vegetation (Pinus tabulaeformis pure forest, Robinia pseudoacacia pure forest, Platycladus orientalis pure forest, natural forest). We also measured soil physical and chemical properties such as soil bulk density and mechanical composition, and monitored soil moisture dynamics in the four types of restored vegetation in the loess hilly-gully region. We calculated soil water storage and analyzed differences due to vegetation type, and conducted correlation analysis and principal component analysis. Three soil infiltration models were then fitted to the measured processes in order to compare their suitability for use in vegetation restoration areas of the loess hilly-gully region. Differences in soil infiltration and water storage between different vegetation restoration types were also determined. We also evaluated the ability of the models to supplement and improve the surface soil water infiltration pattern under different vegetation restoration types in the Loess Plateau region. [Results] ① Natural forest was more effective in improving the physical properties of the 0—30 cm surface soil compared with pure planted forests. Natural forest had greater water content and better water retention, and planted forests were more effective in improving the infiltration capacity of the soil in the study area compared with natural forest. ② The stable infiltration rate of soil under different vegetation types from largest to smallest followed the order of natural forest > Robinia pseudoacacia pure forest > Pinus tabulaeformis pure forest > Platycladus orientalis pure forest (for the 0—10 cm layer); Pinus tabulaeformis pure forest > Robinia pseudoacacia pure forest > Platycladus orientalis pure forest > natural forest (for the 10—20 cm layer); Pinus tabulaeformis pure forest > Robinia pseudoacacia pure forest > Platycladus orientalis pure forest > natural forest (for the 20—30 cm layer); ③ The Horton model performed better than the Kostiakov and Philip models in fitting soil infiltration in the study area (R2=0.94), and will be helpful in better understanding the soil infiltration pattern in the study area. ④ The main physical characteristics affecting soil infiltration rate were soil bulk density, soil organic carbon, soil water storage capacity and soil clay particle content. [Conclusion] There were significant differences in soil infiltration properties due to different long-term vegetation restoration types. Compared with long-term replanted forests, the long-term natural forest had greater vegetation restoration benefits, and could effectively improve soil quality and enhance soil water retention capacity for the Loess Plateau.

Large-scale vegetation restoration has been performed to improve the fragile ecological environment of the Loess Plateau in the last decades. At present, the effects and mechanism of long-term vegetation restoration on soil properties in ecosystems require further exploration to provide a reference for rational ecological construction. Hence, we investigated the differences in vegetation attributes and soil properties between three typical vegetation types (Pinus tabulaeformis plantation forest, PTPF; Robinia pseudoacacia plantation forest, RPPF; natural secondary forest, NSF) after long-term (30–40 years) vegetation restoration in the western Loess Region, China. Our results showed that (1) the arborous synusia biomass of the plantation forests was twice that of NSF, whereas NSF had almost 50% higher near-surface synusia biomass than the plantation forests; (2) the soil nutrient contents of the plantation forests were lower (30%) than those of NSF; (3) the soil bulk density, organic matter, total nitrogen, and phosphorus were positively related to arborous and shrub synusia biomass; (4) the coupling effects of four biological synusiae (with the contribution of 47.67%) were the dominant factors affecting soil physicochemical properties. Natural forests have the better vegetation attributes and soil properties than plantation forests, indicating that the close-to-nature restoration should be considered in ecological restoration. These findings can provide scientific support and theoretical basis for reforestation and ecological restoration in the Loess Plateau region and similar areas in the future.

Aquatic vegetation of different heights is widely scattered in natural rivers and is conducive to their environmental function while affecting the flow hydrodynamic conditions. A semi-analytical velocity model is constructed and used to study the longitudinal velocity profile in open channel flow through double-layered rigid vegetation. The double-layered vegetation flow is separated into three zones according to the velocity profile: 1) nearly uniform distributed velocity zone 1A in the lower region of the short vegetation layer, 2) a mixing layer zone B, 3) uniform distributed velocity zone 2A in the upper region of the tall vegetation layer. Two force equilibrium equations about the gravity-driving and vegetation drag are solved to obtain the uniform velocity distribution equations in zone 1A and 2A. The velocity of zone 1A and B is further modeled as a linear superposition of two concepts: the uniform velocity distribution term of zone 1A and a hyperbolic tangent profile. Meanwhile, longitudinal velocity and the lateral vorticity profiles of open channel flow through double-layered rigid vegetation are studied by laboratory flume tests of different vegetation arrangements exposed to two water depths and three slopes. The experimental results show that the longitudinal velocity increases with the slope increase. The verification of the velocity model is based on the instantaneous velocity measured by Acoustic Doppler Velocimetry (ADV), which shows acceptable agreement, indicating that the model can give a reference to the longitudinal velocity of multi-layered vegetation flow in some cases. The effects of wake vortices and boundary friction on the model are further explored in the discussions. The results presented in this study could contribute to the management of aquatic vegetation configurations and the restoration of freshwater ecology.