Competitive ability of dwarf bamboo (Sasa borealis) through long‐term clonal growth in mixed dwarf bamboo communities in the understory of a temperate deciduous forest

We investigated the clonal competition of three co‐occurring dwarf bamboo species, Sasa borealis, Sasa nipponica, and Sasaella ramosa, for 32 years in an old‐growth beech forest in central Japan. A study plot (10 m × 24 m) was established to examine the culm dynamics of these species. Sasa borealis had a competitive advantage over the other species. It invaded the other bamboo populations at a rate of 0.84–0.89 m/y from 1988 to 2020, while S. nipponica invaded at a rate of 0.17 m/y until 2003. After that, S. nipponica started to retreat at a rate of 0.85 m/y along with the invasion of S. borealis until 2020. The invasion rate of S. borealis did not change before and after the competition with S. nipponica. Our results showed that it would take 13.9–14.8 years from S. borealis invasion for S. nipponica to disappear. The density of S. ramosa decreased but it did not disappear from the plot because it retreated at a slow rate of 0.08 m/y. Sasa borealis almost achieved its potential maximum culm density, but the other two bamboo species did not. If stable conditions were maintained, S. borealis would continue to invade, dominate, and eliminate the other bamboo species. The ecological traits of dwarf bamboo species, such as the maximum density, size, and longevity of culms, are good indicators for assessing their competitiveness. Our findings demonstrate that dwarf bamboo species are actually replaced by another bamboo species in the forest understory during a long period. The ecological traits of dwarf bamboo species, such as the maximum density, size, and longevity of culms, are good indicators for assessing their competitiveness. Our findings demonstrate that dwarf bamboo species are actually replaced in the forest understory during a long period.