ALTERNATE IRRIGATION OF FRESH AND SALT WATER RESTRAINS CLONAL GROWTH AND REPRODUCTION OF SPARTINA ALTERNIFLORA
淡咸水轮换浇灌抑制互花米草的克隆生长和繁殖

Aims Spartina alterniflora is a world-wide, notorious invasive species that has colonized large areas in coastal China since it was introduced in 1979. Its wide range of salinity tolerance and resistance to salinity stress contribute to its invasiveness. However, if its mechanism of salt tolerance can be degraded in freshwater or disturbed by alternating irrigation between fresh and salt water, the invasiveness of S. alterniflora may be reduced. Methods We exposed S. alterniflora for three months to six irrigation treatments: single irrigation with freshwater (D) or saltwater (X), single alternating irrigation with freshwater and saltwater (DX and XD) and double alternating irrigation (DXD and XDX). Important findings With only freshwater, biomass accumulation and asexual reproduction of S. alterniflora was significantly higher than that with only saltwater. Alternating irrigation between fresh and salt water significantly affected biomass, number of propagules and flowering stems, with much stronger effects in the double alternating irrigation treatment. But irrigation treatment displayed weak effects on the root-shoot ratio, stem weight ratio, leaf weight ratio and rhizome weight ratio, although they strongly affected the root weight ratio. Results indicate that single irrigation with freshwater may benefit the biomass accumulation of S. alterniflora and make the species apt to adopt asexual reproduction. However, alternating irrigation between fresh and salt water may restrain biomass accumulation and both sexual and asexual reproduction.