The boundary filtration effect of reed-dominated ecotones under water level fluctuations

TLDR: The boundary filtration effect of land/water ecotones with reed-bed/ditch systems under water level fluctuations was studied in Baiyangdian Lake of North China as mentioned in this paper.

Abstract: The boundary filtration effect of land/water ecotones with reed-bed/ditch systems under water level fluctuations was studied in Baiyangdian Lake of North China. It was found that the changes in reed bed areas which were primarily affected by water level fluctuations and the root channels in the wetland soils together largely determined boundary filtration efficiency. The ecotones displayed the greatest boundary effect at a moderate water level of about 8 m above sea level. The massive root channels in the wetland soils promoted water flowing into the reed beds as far as 8 m horizontally by subsurface in wet years. In dry years, when the water level was below the root channel distribution zone, the lateral water exchange width of ecotones was limited to 0.5 m along the fringe area. It is calculated that, at 8 m water level, the total boundary length of ecotones is 7,273 km and the boundary exchange volume is 5.8 × 106 m3. While at 6.5 m water level, the total boundary length of ecotones is reduced to 2,699 km and the boundary exchange volume is 1.1 × 105 m3. The standard capacity for phosphorus retention was 105.9 and 2.5 tonnes at water levels of 8 and 6.5 m, respectively. This suggests that the boundary filtration effect of reed-bed/ditch wetlands is important for improving the water quality of inland waters, and this effect should be considered in regulating and managing lake water levels.