Response differences of Eichhornia crassipes to shallow submergence and drawdown with an experimental warming in winter

Abstract

Eichhornia crassipes is a noxious weed and is cold sensitive. Water level treatments may affect its overwintering and regrowth capability during warming winter. To test this hypothesis, an experiment was conducted to analyze the effects of different water levels on the survival rates and regrowth of E. crassipes under experimental warm winter conditions. Three water levels were set up including drawdown with rooted, shallow submergence with rooted and floating. Regrowth characters including number of ramets, Fv/Fm, biomass and biomass allocation were surveyed. The results showed that warming significantly increased survival, ramet numbers and the biomass of plants. Warming also significantly increased Fv/Fm in drawdown plants. Water level only impacted plants under warming conditions. Compared to floating plants, drawdown significantly decreased survival but increased total biomass, while submergence led to 100 % survival, significantly higher ramet numbers and increased total biomass. In terms of biomass allocation, the effects of warming were similar for drawdown and submergence cases; it resulted in increased shoot biomass allocation and a lower root mass ratio. Warming only significantly increased the stem mass ratio of floating plants. Our findings suggested that warming help E. crassipes successfully overwinter and regrow during the next growing season. Drawdown or shallow submergence cannot effectively control this species but rather promotes its regrowth during warm winters. Thus, this species has the potential to spread with warm winters and frequent water level fluctuations caused by future climate change.