Development of Vegetation Bands and Beneath Soil Core in a Meandering River

Meandering rivers are among the most common river patterns on earth. Instability of flow causes bank erosion at one side, and the river bend is developed to a meandering route until cutoff occurs at meander neck or on the plane of inner bank. The studied river is actually meandering in a vegetation-growing river basin. Along with failure and erosion at concave bank, silt and mud will deposit upon the inner bank beach with coarse sand during flood period, and vegetation develop quickly at silt-mud deposition layer. The development of vegetation helps its soft base to mitigate flood scouring in return, and pushes the flow path to enlarge its meandering sinuosity. Along with the meandering processes, there are several vegetation bands on convex bank plane paving together with concave bank retreating. They have different elevation and distance from convex bank. In this study, the vegetation bands and the relative soil cores were sampled at two meandering rivers with different river classes at the alpine meadow area in the source region of the Yellow River. The plant communities are different among vegetation bands in this region. It was observed that the further from the bank it is, the higher elevation and the thicker soil layer it would be. The thicker the soil layer is, the richer the plant population is. The first closest band only develops water-tolerant single plant. Translated by 1 or 2 bands, the plant community will be stable at higher convex plane. It is actually a piece of newborn grassland, but different from the aged background steppe basin behind the concave bank in some s. River flow has different migration rates when it cuts the newborn grassland and aged steppe. It is because the aged steppe is usually higher and tougher than the newborn grassland. Its collapsed blocks may pile up at the bank foot, even ladder on the bank slope, in this sense it can slow down the bank retreat effectively, rather than of the blocks draping over the concave bank of newborn grassland.