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ABSTRACT:The utilization of exotic grasses as cover plants for erosion control has received considerable attention in recent years, particularly because these exotic grasses have the potential to become invasive. This study examined succession of exotic grass communities that have been established on the cut slopes of the volcano, Mt. Sakurajima. The results showed that although the exotic grasses, such as Cynodon dactylon, Festuca rubra and Dactylis glomerata, that have been used for erosion control on the cut slopes were dominant for the first two years, marked decreases were observed as the native herbaceous plant, Miscanthus sinensis, became dominant after three years. By the sixth year, all of the exotic grasses vanished completely. This high rate of succession would result in the suppression of exotic grass dispersal on Mt. Sakurajima. It was also suggested that the chemical properties of volcanic soils, and the bio-engineering technique employed on Mt. Sakurajima may have facilitated this high rate of succession.

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In this work, we describe the synthesis of porous Au structures by galvanic displacement reaction using porous Si exhibiting arrays of parallel pores with diameters near 100nm as template material. Two metal ions were used as Au precursors: tetrachloroaurate(III) and bis(ethylenediamine)Au(III). Fluoride was employed to etch the Si oxides that form as a result of the displacement reaction. The porous metal layer that forms with tetrachloroaurate(III) is an agglomerate of spherical particles with ca. 100nm diameter. Metallization with bis(ethylenediamine)Au(III) preserves the morphology of the original porous Si layer, creating a porous Au layer containing an array of parallel pores with ca. 100nm diameter. The displacement process is under diffusion control for both reagents. The expansion rate of the porous metal layer into the substrate agrees well with a simple one-dimensional reaction-diffusion model entailing the displacement of Si in a large extent. The electrochemical behavior of the synthesized porous Au layers was studied by voltammetry.