Effects of water level regulation on the seed germination and production of annual plant Xanthium sibiricum in the water-level-fluctuating-zone of Three Gorges Reservoir

Jianhui Liu,Shaohua Shi,Feng Lin,Bo Zeng,Songping Liu,Qiaoli Ayi

doi:10.1038/s41598-017-04599-4

Abstract

Vegetation effectively slows down the deterioration rate of the ecosystem in the water-level fluctuation zone (WLFZ). In this study, we investigated the impact of impoundment on the germination of seeds from Xanthium sibiricum fruits with various degrees of maturity and produced by X. sibiricum plants growing at different elevations in the WLFZ. Seed production by X. sibiricum under the current water level regulation mode was also investigated. Seeds were collected from seven elevations of the WLFZ of Three Gorges Reservoir (TGR) and exposed at these elevations to submergence. Seed production of the plants germinated from X. sibiricum seeds was observed. The maturity degree of X. sibiricum fruits from different elevations has no influence on the seed production by the plants that are produced from the fruits. Under the present water-level regulation mode, X. sibiricum growing above 155 m are able to generate mature seeds and thus provide seed sources for population maintenance, although the plants growing at an elevation below 165 m failed to produce fruits in 2010 due to unusual flooding. This study is useful for the vegetation recovery and reconstruction in other regions with hydrological characteristics similar to that of the TGR.

Highlights

Vegetation effectively slows down the deterioration rate of the ecosystem in the water-level fluctuation zone (WLFZ)
Whether an annual can grow and reproduce naturally in the WLFZ in the Three Gorges Reservoir (TGR) primarily depends on the completion of two processes in its life history: (1) seed germination, i.e., whether seeds produced prior to impoundment can tolerate long-term and deep complete submergence in the WLFZ and germinate successfully after water recession, and (2) seed generation, i.e., whether the plants in the WLFZ can generate a sufficient number of mature seeds prior to impoundment, providing sufficient seeds for population persistence
In a field survey conducted in the TGR WLFZ, we found that plants in X. sibiricum communities growing at different elevations in the WLFZ show different degrees of maturity before the impoundment, and the maturity degree of the seeds produced by X. sibiricum plants differs

Summary

Introduction

Vegetation effectively slows down the deterioration rate of the ecosystem in the water-level fluctuation zone (WLFZ). Under the present water-level regulation mode, X. sibiricum growing above 155 m are able to generate mature seeds and provide seed sources for population maintenance, the plants growing at an elevation below 165 m failed to produce fruits in 2010 due to unusual flooding. Whether an annual can grow and reproduce naturally in the WLFZ in the TGR primarily depends on the completion of two processes in its life history: (1) seed germination, i.e., whether seeds produced prior to impoundment can tolerate long-term and deep complete submergence in the WLFZ and germinate successfully after water recession, and (2) seed generation, i.e., whether the plants in the WLFZ can generate a sufficient number of mature seeds prior to impoundment, providing sufficient seeds for population persistence. Annual plants can exist naturally in the TGR WLFZ only when these species can successfully complete these two life processes

Methods

Results

Conclusion