淡咸水轮换浇灌抑制互花米草的克隆生长和繁殖

ALTERNATE IRRIGATION OF FRESH AND SALT WATER RESTRAINS CLONAL GROWTH AND REPRODUCTION OF SPARTINA ALTERNIFLORA

作为典型的盐沼植物,入侵种互花米草(Spartina alterniflora)具有较强的耐盐性,能否以淡水或淡咸水的轮换浇灌扰乱其耐盐机制,降低其生态入侵性,进而寻求其控制对策是一个重要命题。为此,对互花米草进行了6种浇灌处理:单一的淡水(D)或咸水(X)浇灌;1次浇灌转换,即先淡水后咸水(DX)或先咸水后淡水(XD);2次浇灌转换,即由淡水开始转而咸水,再转而淡水(DXD),或由咸水开始转而淡水,再转而咸水(XDX)。结果显示,D处理的总生物量最高,与其它各处理均差异显著(p<0.05),且是X处理的1.67倍;DXD和XDX处理的总生物量最低,与D和X处理的差异显著(p<0.05),两者均约为D处理的50%。浇灌处理对根冠比、茎重比、叶重比和根茎重比的影响不明显,对根重比有较大影响,X处理的根重比最高,与D处理的差异显著(p<0.05),但与DX、XD、DXD和XDX处理之间的差异不显著。D处理的克隆生长新生总株数(Propagule)最多,与其它处理均差异显著(p<0.05),且是X处理的1.34倍;DXD和XDX处理的新生总株数最少,与D和X处理的差异显著(p<0.05),仅为D处理的55%。浇灌处理对分蘖的影响明显,DX和DXD处理的分蘖数分别是D处理的62%和50%;XD和XDX处理的分蘖数分别是X处理的50%和47%。就开花株数而言,X处理显著高于其它处理(p<0.05);DXD和XDX处理的开花株数为0。因此,持续的淡水浇灌可能会促进互花米草的生物量积累,并且采取快速的克隆生长为主的繁殖策略;而在淡水和咸水交替的生境下,互花米草的生物量积累、无性和有性繁殖能力都会受到抑制。

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. aiterniflora 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. Ahemating 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.