Role of rhizomes in tussock formation byCarex thunbergii var.Appendiculata

Several types of tussock formed byCarex thunbergii var.appendiculata were compared with respect to the growth pattern of their rhizomes at various developmental stages at Benten Marsh in Yufutsu Mire, Hokkaido, Japan. The rhizomes were classified into three types based on their function: 1, very short rhizomes; 2, intermediate-length rhizomes which grow upwards to raise the shoot base; 3, long rhizomes which grow horizontaly to spread the plant. The extent of development of the tussock and the total length of rhizomes per shoot was inversely related with the number of Type 3 rhizomes, and positively related with Types 1 and 2 rhizomes. The tussock was made of dead roots, dead rhizomes and much litter, which provided a substitute for soil for the rhizomes and absorbing roots. The growth conditions of theCarex changed from aerobic and eutrophic to anoxic and oligotrophic with tussock development. It is concluded that the tussock is adaptive to anoxic conditions.