遷移からみた埋土種子集団の解析I

抄録

The senior author and his collaborators have made experimental studies on the plant succession, especially its earlier stages (NUMATA and YAMAI 1955,NUMATA 1956,NUMATA and SUZUKI 1958,NUMATA 1961), where the sociological structure and succession were analysed in detail. However, there have been published very few informations on the buried-seed population which is the mother's womb of plant communities. Concerning the studies on seeds, there are many reports on the agricultural and silvicultural seeds in applied fields, and physiological studies in pure fields. But there are very few reports on the "ecology of seeds" ("Okologische Samenkunde") where they must be studied related to the structure and succession of the plant communities. For this reason the purpose of the present project is to obtain precis knowledge on the seeds. In this paper, the Erigeron stage (I), the Imperata stage (II), and the Pinus stage (III) in the campus of the Chiba University were studied and compared with each other concerning their floristic composition (Table 2), biological spectra (Table 3), and the degree of succession (Table 4). The buried-seed populations in the same stands were examined. Ten units (sampling unit : 40 cc) of soil were sampled based on the species-volume curve (Fig. 1) according to the stratification of 0〜1,1〜2,2〜5,5〜10,10〜20,and 20〜30cm in depth. Buried-seeds in the soil were separated by 50 per cent K_2CO_3 solution. The buried-seed populations in the three seral stages does not exactly correspond with the floristic composition of the actual plant communities, and that in a seral stage contains seed-grains of the former stages as well as some of the later stages. The number of seed-grains and the number of species decrease as the succession proceeds. The number of seed-grains the rank of species relationship (Fig. 3) satisfies the law of geometrical progression as in the terrestrial parts of the plant communities. The decrease of the number of seed-grains with increasing soil depth frequently shows a certain tendency (Fig. 4).