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Sediment connectivity is closely related to geomorphology, topography, ecological hydrology, soil erosion, nutrient and pollutant movement, and water quality conservation. As one of the hot topics in soil erosion research during the past decade, sediment connectivity is required to be fully examined from the perspective of soil erosion. Sediment connectivity describes the interactions of sediment cascades between different topographical and landscape units in a system which is usually quantified with the structural connectivity and functional connectivity in four dimensions, i.e.,lateral, longitudinal, vertical and temporal. Its impacting factors include climate, lithology, geomorphology, watershed characteristics, topography, soil properties, vegetation, hydrological processes, soil erosion and human activities as well as their temporal and spatial variations. The specific influencing mechanisms vary among these factors and among different spatial scales, therefore resulting in distinct responses of sediment connectivity. Field survey and mapping, graph theory, index and model simulation are frequently applied to investigate and quantify sediment connectivity. The theories behind these methods are different, so do the required data, specific procedures, and the corresponding results. The index of connectivity（IC） is the most widely employed in the quantification of sediment connectivity. Nevertheless, IC well reflects the structural connectivity, rather than the functional connectivity. From the perspective of soil erosion, future studies regarding sediment connectivity should focus on the concept, influencing factors and their dynamic mechanisms, method comparison and index optimization, relationships of sediment connectivity with hydrological connectivity, soil erosion and sediment delivery ratio, as well as the effects of soil conservation measures on sediment connectivity and the corresponding mechanisms. [ABSTRACT FROM AUTHOR]

Sediment transport capacity of overland flow, which is the maximum equilibrium sediment load that a flow can transport, is a key concept for developing process-based soil erosion models because it plays a pivotal role to determine soil detachment rate and sediment transport. Few studies have been conducted to investigate the mechanism of sediment transport capacity by overland flow on steep slopes. In this paper, based on the systematic definition of sediment transport capacity of overland flow, the influences and their mechanisms of hydraulic properties of overland flow and sediment characteristics on sediment transport capacity were deeply analyzed. Sediment transport capacity of overland flow has great spatial and temporal variations due to the comprehensive effects of precipitation, topography, soil, vegetation, land use, sealing formation, rill development, and gravel covering. Therefore, it is very difficult to measure sediment transport capacity of overland flow directly in field conditions. The commonly used methods to determine sediment transport capacity of overland flow can be categorized into the modification from river sediment transport capacity formula, the rational method, the model simulation, and the direct measurement. The advantages and disadvantages of each method were compared and analyzed. Further studies should be focus on the measuring methodology and techniques for sediment transport capacity of overland flow, the hydro-dynamic mechanism of sediment transport process, sediment transport capacities of typical soil types, transport capacity formula development and performance evaluation, and sediment transport capacity of overland flow under changeable conditions. It is helpful to summarize the conclusions of different studies, promote the research on sediment transport capacity of overland flow, and improve the prediction precision of the process-based soil erosion models for better service to water and soil conservation planning and design. [ABSTRACT FROM AUTHOR]