The transport/detachment regimes of each particle size vary with size. Moreover, the changing transport/detachment regimes of sediments with size and their related mechanisms considerably affect sediment transport capacity (Tc). To investigate the transport/detachment regimes of each particle size and their explanation for Tc prediction, 27 simulated rainfall experiments were conducted under slope gradients of 8.7%, 17.6%, and 26.7% and rainfall intensities of 60, 90, and 120 mm h−1. The experimental soil was Cumulic Anthrosols, and the duration of each rainfall was 1 h. Results showed that for rain-induced overland flow erosion, the average transport ratios (Trs) of clay, fine silt, and coarse sand (<0.002, 0.002–0.02, and >0.25 mm, respectively) for rainfall, were greater than 1.0, and their erosion regimes were detachment-limited. The Trs of coarse silt and fine sand (0.02–0.05 mm and 0.05–0.25 mm, respectively) were less than 1.0, and their erosion regimes were transport-limited. The transport-/detachment-limited degree of each size class of particles, except for coarse sand, increased with the slope gradient, but slightly and complexly changed with rainfall intensity. The Trs of each size class of particles on the gentle slope (8.7%, 17.6%) increased with the Trs of total sediments. In the case of the steep slope (27.6%), however, the Trs of fine silt and clay increased with a decrease in the Trs of the total sediment particles. Different prediction equations were established to simulate the Tcs of sediments with different sizes in the two slope ranges (R2 > 0.823, p < 0.01). The findings will help to elucidate the selective transport mechanisms of all sizes of sediment particles and improve the prediction of Tc in the future.

Soil may be a carbon source or sink under the effect of sediment and soil organic carbon (SOC) erosion, transport and deposition. Partial SOC processes to determine whether soil subjected to water erosion is a carbon sink or source have not been clarified but are essential for increasing and predicting SOC storage. In this review, the associations between SOC mineralization, stability and stock at erosion sites, in transported sediments and at deposition sites are clarified. An overview is given for possible determination standards that define soil carbon sinks and sources. Methods for enhancing SOC sequestration and suggestions for improving SOC prediction are also presented. Particle transport is an important intermediate process that determines the material base for SOC stability and sequestration in each erosion and deposition element. When subject to water erosion, a high probability of SOC physical stabilization and a thick soil layer are essential for soil to function as a SOC sink. Sediment transport weakens SOC physical protection in eroded areas but can promote aggregation factors at deposition sites in some cases while increasing the depth of SOC in the soil. In this circumstance, a good soil environment for plant growth facilitates the occurrence of carbon sinks. A concept for critical erosion intensity is proposed to understand SOC sink determination; the concept is presented as the volume of soil erosion per square kilometre (m3 km−2) for which the maximum reduction in vegetation cover or plant biomass still permits plants to provide enough organic matter to compensate for erosion‐induced SOC loss. If erosion intensity is higher than critical erosion intensity at the erosion site, soil degradation is obvious, and soil is presented as an OC source, and vice versa. Finally, the SOC burial method for increasing the soil carbon storage amounts in regions with thick soil layers is presented to explore the SOC sequestration potential in deep soil. The factors considered for SOC prediction should vary with research scale. We hope our review will have direct implications for the modelling of SOC dynamics under water erosion on both slopes and at large scales. Highlights Changes in soil texture and soil thickness greatly affect the amount of SOC storage at erosion and deposition sites. Selective transport of soil materials or chemical elements promotes soil aggregation. Possible standards that define soil carbon sinks and sources and suggestions for improving SOC prediction are presented. SOC burial may be a good method for increasing C storage amounts in regions with thick layers of fine soil.

Splash erosion plays a vital role in the loss of eroded materials. Unlike those in slope central areas, laterally ejected splashed materials in slope border areas cannot be replenished easily because slope edges prevent splash erosion particles from entering the slope. Thus, splashed materials in slope border areas are less than those in slope central areas because of the lack of source areas for splash-eroded materials. However, this phenomenon, called the slope border effect, has received minimal attention by researchers. The partially missing

Pine wilt disease (PWD) is a highly destructive disease in forest ecosystems, resulting in extensive forest decline and substantial economic losses. As soil pH plays a critical role in soil microbial activity and significantly impacts the prevalence and severity of diseases, we conducted an experiment to regulate soil pH for alleviating PWD in a black pine (Pinus thunbergii) forest. The result reveals that: (1) The pH of the soil under a P. thunbergii forest was 5.19 ± 0.40, which was significantly lower than that of soils under other vegetation types at 8.53 ± 0.44. (2) Finely ground shell powder (F-SP) was the optimal size for long-term and efficient regulation, but quicklime (QL) exhibited the strongest efficacy in raising soil pH, followed by F-SP and plant ash. The regulation effect strengthened with the dosage amount. (3) In the situ experiments, part of symptomatic black pine in F-SP or QL plots were apparently improved and converted to asymptomatic trees separately by 15.9% and 5.4%. Applying F-SP can alleviate PWD in a sustainable way. This paper presents the first investigation to assess the effects of regulating soil pH for controlling PWD. It holds significant practical value for the rational planning and the sustainable development of artificial forests in coastal regions.