克隆植物大米草 (Spartina anglica) 目前在我国出现了严重的自然衰退 (Dieback) ，为了阐明大米草衰退的机理，分析影响大米草形态可塑性的因素与自然衰退之间的相关性，以期为近缘植物互花米草 (S.alterniflora) 这一爆发种群的生物控制提供借鉴，对3种不同初始克隆分株数 (单克隆、三克隆和五克隆)大米草的克隆生长、生物量累积与分配和异速生长特征进行了野外栽培试验。研究结果表明，初始克隆分株数对间隔子长度影响较弱；初始多克隆的分支强度高于初始单克隆；初始三克隆和五克隆在总生物量 (7.921 5～10 .431 7 g 和 8.903 9～10.431 7 g)、地上生物量 (3.396 1～4.255 8 g 和3.618 4～4.338 9 g )、地下生物量 (4.286 9～5.206 6 g 和 5.298 8～6.079 3 g)和根状茎生物量 (1.318 6～1 .767 7 g 和 1.499 1～2.038 7 g) 积累上均显著高于初始单克隆，不同初始克隆分株数条件下根生物量差异不显著；初始多克隆倾向于将资源更多地分配给根状茎，而初始单克隆倾向于将更多的资源分配给根系。由此推断，在不同初始克隆分株数条件下，大米草的形态可塑性和生物量分配格局的差异显示出在同样资源格局下，初始多克隆的克隆生殖能力较初始单克隆强。初始多克隆生长的大米草较初始单克隆生长的大米草更能占据优势生境，选择生境 “觅养”的能力与克隆繁殖能力更强。
Aims Spartina anglica, a world-wide invasive species introduced from Europe in 1963, rapidly increased in coastal China before the 1990s and thereafter drastically declined. Researchers hypothesized that small initial clone numbers might be responsible for the decline. We investigate the effect of different initial clone numbers on morphological plasticity and biomass allocation of S.anglica.
Methods From May to November 2005, field experiments were conducted in S.anglica vegetation located along the coast of the Yellow Sea (32°34′-34 °28′ N, 119°48′-120°56′E). We set up three treatments with one, three, and five initial clones. For each plant, we measured height, stem diameter, leaf thickness, leaf area, number of leaves, spacer length and branching intensity as morphological parameters and number of ramets, rhizomes and rhizome nodes and total length of rhizomes as growth traits. We also analyzed biomass accumulation, allocation and allometric growth of S. anglica.
Important findings With greater initial clone number, branching intensity, total biomass, above-ground biomass, below-ground and rhizome biomass increased significantly, but initial clone number did not affect root biomass and spacer length. Plants in multi-clone treatments tended to allocate more resource to rhizomes, while those in the single-clone treatment tended to allocate more resource to roots. Results indicated that S. anglica plants with multiple clones had more effective asexual reproduction than plants with a single clone. Because most environments likely were invaded by a single clone and then added additional clones, we hypothesize that the main reproduction strategy of S. anglica has changed from sexual to asexual reproduction, which may account for the population dieback since the 1990s in China.