SEED BANK AND VEGETATION SUCCESSION IN ABANDONED FIELDS IN KARKALI-NATURE-RESERVE, SOUTHERN FINLAND

The vegetation of three abandoned fields in Karkali Nature Reserve in southern Finland developed without human impact for 21 years. In 1967, the first summer after abandonment, permanent sample plots were set u p to study the succession of the vegetation; these were inspected ever y fifth year. In autumn 1988 and 1989, soil samples were taken for see d germination. The composition of the seed bank is here correlated wit h the successional vegetation cover. The average size of the seed bank was 50 000 viable seeds m-2 to a depth of 25 cm. The most abundant ta xa were Gnaphalium uliginosum (L.) Opiz, Juncus spp., Hypericum spp., Sagina procumbens L. and Veronica serpyllifolia L., representing speci es common in the early stages of succession. Seeds of 17 species were found to have remained viable for 5-21 years. Analysis of the vertical structure of the seed bank is shown to be a useful means of evaluatin g which seeds arrived before and which after the abandonment of the fi elds.