Secondary succession on cut slopes of forest roads in Nukumi-daira, at the base of the Iide Mountains, Yamagata Prefecture (V)

Biological spectra and community organization

Abstract

To analyze the community dynamics on permanent plots on sprayed cut slopes of forest roads, in the cool-temperate snowy region, from 1974 to 1981, the composition of RAUNKIAER's dormancy forms, NUMATA's migrule forms (disseminule and radicoid forms), and growth forms were studied, and the community organization was compared with the calculated ΣDS (degree of succession). The biological spectra indicate successional change during the eight years according to the increase of N (M+MM), D₁, R₃, and erect forms and the decrease of H, D₄, R₄+R₅, and tufted, prostrate forms. For the community types consisting of the life-form combinations, Th-R₅-D₄, and H-R₃-D₄ types decreased, and N-R₅-D₄ and MM-R₅-D₄ types increased. These changes were attributed to the decline of introduced species and the luxuriance of the native species. The plant community organization on the cut slopes was considered to be of three important types, linear, L-type, and S-type, in terms of the relative dominance-species sequence relationship. Linear relationships were observed in the case of small specific-densities and under severe environmental conditions. The dominance-rank relationship seems to show development of the plant community from MOTOMURA's linear type to PRESTON's S-type with increasing species density. The ΣDS commonly reflected the type of secondary succession, such as the correlations of ΣDS with the woody species percentage and with the vegetation height being high, but the species density being low.