Ecological Characteristics of Remnant Populations in the Rare Plant Scrophularia takesimensis Nakai

초록

Population size, vegetative and reproductive components, vegetation structure, and habitat quality in the rare perennial plant Scrophularia takesimensis were investigated in the Ulnung Island. S. takesimensis is limited to the only Ulnung Island and occures in a sheltered rocky coast. It has decreased in abundance due to habitat degradation and fragmentation from the construction of read and enbankment in a coastal area. In 2000 only about 13 populations with two-300 individuals survive in the whole island. Plant height was 150 cm to the maximum and 80 cm on average. Plants had 14 branches to the maximum and produced 1100 capsules on average. In the community of S. takesimensis, Calystegia soldamella and Aster spathylifolius often cooccured. Electric conductivity of soil (soil:water = 1:2 w/v) was on the wide range of organic matter was 5.4% at the habitats of S. takesimensis. The fragmented remaining populations of this rare plant were to decline further or even become extinct due to a consequence of human-related habitat destruction.