Responses of lakeshore herbaceous plant guilds to altered water level fluctuations in Yangtze floodplain lakes, China

Abstract

River–lake disconnection has led to alterations in natural water level fluctuations (WLFs) in lakes along the middle and lower reaches of the Yangtze River to various extents. To predict the effects of altered WLFs on lakeshore vegetation, lakeshore herbaceous plant guilds (LPGs) in six Yangtze floodplain lakes were classified in this study. The lakeshore herbaceous plant distribution pattern, main influencing factors, and responses of different LPGs to altered WLFs were analyzed. A total of 130 plant species were identified from the six lakes. With the increase in the amplitude of WLFs, the total species number in the six lakes showed a hump–shaped trend, whereas the lakeshore herbaceous plant coverage showed a positive correlation. The Qili Lake with the largest WLFs had the lowest species number and highest plant coverage. The species numbers, average biomass, and coverage of lakeshore herbaceous plants in all the six lakes were obviously higher in spring than in autumn. The lakeshore herbaceous plants in the six lakes were classified into eight guilds. Small differences in pH, organic matter, total nitrogen, and total phosphorus were detected in the substrate among the eight LPGs, but obvious differences in soil moisture content and duration and depth of submergence were observed. The canonical correspondence analysis showed that the main environmental factors affecting the distribution of different LPGs in the six lakes in spring and autumn were the amplitude of WLFs and duration of submergence. The regression analyses showed that the biomass of perennial mesophyte with erect stem guild and perennial hygrophyte with well–developed rhizome guild responded sensitively to alterations in the amplitude of WLFs and duration of submergence, and the guilds could be considered as indicator groups at a regional scale. Morphological parameters such as plant height, stem diameter, leaf thickness, and specific leaf area of the eight LPGs showed no significant linear relationships with the increase in WLFs. The use of these parameters in the evaluations of alterations in WLFs needs to be further analyzed.