Effect of sand deposition on germination depth and spatial distribution of Ischaemum anthephoroides and Fimbristylis sericea of coastal sand dune plants

Abstract

To clarify the determinants of spatial distribution of two coastal sand dune species, Ischaemum anthephoroides and Fimbristylis sericea, we evaluated the relationship between sand deposition and germination depth of seedlings for each species. We surveyed vegetation, microtopography and sand deposition along three transects from the shoreline to the commencement of the black pine forest on the Fukude coast, facing the Enshu-Nada Sea, Japan. We measured the germination depth of seedlings in 1 m × 1 m quadrats at the top, landward slope and backland of the foredune area of the coast. We also weighed fruits of the two plant species. I. anthephoroides was mainly distributed at the top of the foredune with greater sand deposition, whereas, F. sericea was mainly distributed at the backland of the foredune with relatively little sand deposition. The germination depth of I. anthephoroides was greater than that of F. sericea at the landward slope of foredune where both plants appeared. In addition, seeds of I. anthephoroides were heavier than those of F. sericea. It was found that I. anthephoroides could emerge from a greater depth in the sand, because heavy seeds have greater energy content than lighter ones. Collectively, our results suggest that the distribution of I. anthephoroides and F. sericea is affected by tolerance of seedlings emergence to sand deposition.