Ecology of Pioneer Species of Early Stages in Secondary Succession I

Abstract

Autecological studies were carried out about 14 important species which constitute the early stage of subsere. The comparative study of their germination behaviour is an attempt to account for the mechanism of plant succession in Kanto district, central Japan. The seed of Ambrosia elatior, Erigeron annuus, Chenopodium album var. centrorubrum, etc. were incubated under different light-temperature regimes, after preservation under three distinct conditions: 1) under room temperature, 2) stratification at 0-3°, 3) buried in the field soil. The weight of seed and their dissemination type of these species were examined, too. The seed of the pioneer species such as Ambrosia elatior, Setaria viridis and Polygonum nodosum are heavy, and the germination is characterized by: 1) slow progression of after-ripening, 2) acceleration of it by stratification at 0-3°or burying in the field. In the contrast with them, Erigeron annuus and E. sumatrensis which replace the pioneer species and become dominant of the community with the progress of succession, have light seed and high germination rate even in a younger age of after-ripening. Also they show no effect on the germination rate after stratification or burying treatment in the field soil. The characters necessary for the pioneer species in the first year are discussed based on the results mentioned above.