SALICORNIA EUROPAEA COMMUNITY ON THE OKHOTSK SIDE IN HOKKAIDO, JAPAN : ECOLOGICAL STUDIES ON THE SALT MARSH VEGETATION IN HOKKAIDO, JAPAN(3)

Abstract

Salicornia europaea is found in Hokkaido, Honshu and Shikoku in Japan. In Hokkaido, it occurs in Lake Akkeshi, Lake Huren, Cape Notsuke, and the lagoons along the Okhotsk Side, namely Lakes Mokoto, Notoro, Saroma and Shibunaito. The writer investigated the Salicornia europaea community in the Lakes Notoro and Saroma, and divided it into 3 sociations ; 1) Salicornia europaea Sociation 2) Salicornia europaea-Spergularia var. asiatica Sociation and 3) Salicornia europaea-Juncus gracillimus Sociation. The community of Salicornia europaea can not keep the stable phase. In Lake Notoro, the floating ice renders great influence to the Salicornia vegetation. Sometimes the destructive action of the floating ice and the full extent of flooding due to its melting in spring cause quantitative or qualitative changes of the community over the whole salt marsh. The best development of Salicornia vegetation occurs near the mouth of the rivers emptying into the lagoons. Salicornia europaea forms often a pure community and sometimes it is accompanied by Spergularia salina var. asiatica. Glaux maritima var. obtusifolia is also found in the salt marsh but it also grows in drier places. Juncus gracillimus tends to be incresed by horse-grazing. The number of individuals of Salicornia europaea in one square metre amounts to 6,760 from 427 in 7 quadrats taken. Measurement of the salinity of the soil in contact with the plant roots shows that Salicor nia sp. has a preference for wider salt concer tration, 6‰-25‰. Spergularia sp. for medium, 9‰-12‰ and Juncus sp. for lower, 5‰. The salinity may be one of the factors which control the development of the communities mentioned above.