Effects of Eutrophication and Different Water Levels on Overwintering of Eichhornia crassipes at the Northern Margin of Its Distribution in China.

Haihao Yu,Dan Yu,Chunhua Liu,Xianru Dong,Shufeng Fan

doi:10.3389/fpls.2019.01261

Abstract

When exotic species are introduced into new areas, establishment is a vital step in their invasion process. Therefore, overwintering strategies determine whether an exotic species from low latitudes can successfully invade middle- and high-latitude areas. In this study, we investigated the effects of nutrient and water drawdown on overwintering in an exotic aquatic plant from the tropical zone, Eichhornia crassipes, at the northern margin of its distribution in China. The population density, size of individuals, and the size and nitrogen concentration of overwintering organs (stem base) of E. crassipes that grew in high-nutrition water were greater than those that grew in low-nutrient water before winter. The overwinter survival rate of E. crassipes was significantly affected by the water level and nutrient. The thick and dense floating mat of E. crassipes can increase the temperature of water bodies; therefore, the overwinter survival rate of E. crassipes was higher in constant-water-level and high-nutrient treatment. In contrast, due to the loss of heat preservation provided by the floating mats and the low nitrogen concentration in the stem base, all individuals of E. crassipes died in constant-water-level and low-nutrient treatment. In the water-drawdown treatments, the stem base of E. crassipes was directly exposed to low-temperature air; therefore, the overwinter survival rate of E. crassipes was lower. Our results reveal that eutrophication can not only improve the competitiveness of E. crassipes but can also improve the survival rate of overwintering plants in temperate regions. Our study also suggests that removing nutrients from the water and regulating the water level can limit the invasion of E. crassipes in temperate and subtropical regions.

Highlights

When exotic species are introduced to new ranges, only a few species can establish populations and become invasive
In order to test whether eutrophication and water level changes can facilitate the overwintering of E. crassipes as well as climate warming and found the reasons, we investigated the effects of nutrients and water drawdown on the overwintering of E. crassipes, at the northern margin of its distribution in China
The average temperature in winter ranges from 3 to 7°C, which is the critical temperature for the overwintering of E. crassipes; Liangzi Lake is located at the northern margin of the E. crassipes distribution in China (Li and Xie, 2002)

Summary

Introduction

When exotic species are introduced to new ranges, only a few species can establish populations and become invasive. Low-temperature and freezing events in winter result in the invasion failure of many introduced exotic species or restrict the distribution ranges of species that have successfully invaded (Owens et al, 2004; Walther et al, 2009; MacIsaac et al, 2016). Water level is an important factor affecting the growth and reproduction of aquatic plants in freshwater ecosystems (Chambers and Kalff, 1985; Ishii and Kadono, 2004; Deegan et al, 2006; Smith and Brock, 2007; Xiao et al, 2007; Xie et al, 2008). Water level changes can influence the overwintering of exotic species

Methods

Results

Conclusion