Demographic analysis of interspecific interaction in sand dune plants

Karex Kobomugi是日本沿海沙丘植被的主要组成部分。据推测，该物种在沙丘的有限分布是由于其他内陆物种的竞争排斥，因为没有种间竞争，小叶苔草可以在内陆条件下生存和生长。在日本中部的一个沙丘系统中，我们监测了该物种在有和没有白茅共生的地方的新梢种群动态。在生长季节结束时，我们挖掘地块以确定母亲和女儿芽之间的联系。在Carex kobomugi中，母枝产生两种类型的子枝：一种附着在母枝上，另一种在距离母亲有根茎的地方产生。白玉兰占优势的样地中前一类枝条所占比例要小于没有白玉兰的样地。这表明，在白茅林的拥挤条件下，小叶苔草的新梢往往在母枝形成的空隙中再生。从转移矩阵模型中，我们找不到证据支持白茅的存在减少了苔草种群的生长。

Carex Kobomugi is a major component of coastal sand-dune vegetation in Japan. It is hypothesized that the restricted distribution of this species to sand dunes is due to competitive exclusion by other inland species like Imperata cylindrica var.koenigii, beacuse without interspecific competition, Carex kobomugi can survive and grow in an inland condition. In a sand dune system at Ajigaura, central Japan, we monitored shoot population dynamics of this species at places with and without coexistence of Imperata cylindrica. At the end of a growing season, we excavate the plots to determine the connection between the mother and daughter shoots. In Carex kobomugi, a mother shoot produced two types of daughter shoots : one type attached to the mother shoot and the other produced at a distance from the mother with a rhizome. The proportion of the former type of shoots was smaller in a plot where Imperata cylindrica was dominant than in a plot without Imperata cylindrica. This implies that under crowded conditions with Imperata cylindrica, the shoot of Carex kobomugi tend to regenerate in a gap which was created by their mother shoot. From a transition matrix model, we could not find evidence which supports the reduction of growth of the shoot population of Carex kobomugi by the presence of Imperata cylindrica.