Lowest Elevation of Plant Growth and Soil Characteristics in Natural Drawdown Areas in the Jiangjin Section of the Yangtze River

This study explores the effect of flooding on the vegetation and soil of the water level fluctuation zone (WLFZ) in the Jiangjin section of the Yangtze River. The vegetation community and physical and chemical soil properties at water level elevations of 188–200 m above mean sea level (a.m.s.l) were studied using the belt transect method and the quadrat method when the section was at its lowest water level, with the nonfluctuating zone above 200 m a.m.s.l as a control. Perennial and flood-resistant species, such as Phalaris arundinacea, were dominant in the herbaceous community from 193 to 200 m, and the apparent lowest elevation of plant growth was from 188 to 193 m. From 193 to 206 m, soil bulk density decreased with increasing elevation but increased with soil layer depth. The soil nitrogen (N), phosphorus (P) and potassium (K) in the nonfluctuating zone were higher than those in the WLFZ zone. However, the soil organic matter from 193 to 200 m was higher than that in the nonfluctuating zone. The soil N, P and K from 188.06 to 188.09 m were higher than those from 188.3 to 189 m, except for hydrolysable N. The lowest elevation of plant growth did not result from a lack of soil fertility due to long-term submergence.