In Hamasaka Sand Dune , Tottori Prefecture, San'in Region, we investigated the vertical changes of the distribution pattern of shoots of Carex kobomugi OHWI population buried in the sand. For an excavation survey, three plots were sampled from a quadrat of 4 m X 4 m in size.Plot A of 1 m X 1 m was dug to 70 cm in depth, Plot B of 0.5 m X 1 m was to 40 cm and Plot C of 1 m X 1 m was to 60 cm, respectively. In the former two plots, the location of shoots was mapped in every 10 cm layer, and plant materials were collected and their fresh weights were measured. In the last plot, only plant materials were weighted in every layer without mapping shoots .
Distrubtion pattern of shoots was analyzed by Iδ-biomass method. Contagious distribution with samll or large clump, in which intra-clump distribution is uniform, was detected from almost sand layers in Plot A and B , except for the most upper two layers of Plot B showing random distribution. There existed a trend that the larger is the biomass, the lower is the maximum Iδ-value of each layer. Contagiousness of shoot distribution of C. kobomugi population is the intrinsic property which may be represented constantly in time and space sequence.