オオキンケイギクが侵入した河川敷における表土はぎとりによる礫河原植生の再生効果

概要

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A large number of buried seeds of Coreopsis lanceolata accumulate on the topsoil in C. lanceolata-dominant communities. The objective of this study was to investigate the effects of removing the topsoil on the C. lanceolata-dominant community, in terms of the elimination of the buried seeds of C. lanceolata and the restoration of the native vegetation in dry gravel riverbeds. After the removal of the topsoil, the number of buried seeds of C. lanceolata decreased by 80% as compared to the number of buried seeds of C. lanceolata before the removal of the topsoil in the experimental plot. Three years after the removal of the topsoil, the total number of shoots of C. lanceolata occurring in the experimental plot decreased by 97 to 99% as compared to the number of shoots of C. lanceolata before the removal of the topsoil. These results show that removal of the topsoil is effective in eliminating the buried seeds of C. lanceolata as well as in decreasing the accumulation of C. lanceolata. On the other hand, the dominance of the endemic species in dry gravel riverbeds, such as Artemisia capillaris and Potentilla chinensis, was low. However, the number of individuals of these species began to increase two years after the removal of the topsoil.