Changes in silica in litterfall and available silica in the soil of forests invaded by bamboo species (Phyllostachys pubescens and P. bambusoides) in western Japan

In Japan, the total area covered by bamboo species has been increasing in recent years. A limited number of studies have been conducted to elucidate the changes in nutrient dynamics in forests invaded by bamboo species. Bamboo species are silica accumulators, taking up silica actively from the soil and accumulating most of the absorbed silica in the leaves. Therefore, it could be assumed that bamboo forests will absorb and return substantial amounts of silica to the soil especially when compared with forests in which non-silica accumulators are dominant (other types of forests). In addition, abundant silica uptake and return in bamboo forests might also change the available silica in the surface soil between bamboo forests and other types of forests. In this context, the silica content in litterfall and the available silica concentration in the surface soil from April 2004 to April 2005 were compared in forests invaded by bamboo species (Phyllostachys pubescens and P. bambusoides) and adjacent evergreen broad-leaved forest or coniferous forest in western Japan. The results showed that bamboo forests had a significantly higher silica content in litterfall through a year than the other two forest types and had a significantly higher available silica concentration in the surface soil from June to November in 2004 than the other two forest types. These findings suggest that when non-bamboo forests are invaded and dominated by bamboo species, the silica content in litterfall and the available silica concentration in the surface soil changes.