Spatial and temporal flowering patterns of the monocarpic dwarf bamboo Sasa veitchii var. hirsuta

In order to clarify spatial and temporal patterns in the flowering process of S. veitchii var. hirsuta, the authors investigated the flowering of the species at a regional level in a mountainous area of Kyoto City, and at population/individual culm levels at experimental forest stations within the same municipal region. S. veitchii var. hirsuta flowered in several separate areas spanning ranges between several and more than 10 km north-south and east-west from 2004 to 2007. Sporadic flowering occurred the year before mass flowering. In the mass-flowering year, 98% of the culms in an S. veitchii var. hirsuta population flowered, and the other 2% or so flowered in the years before and after mass flowering. These results show a spatiotemporal synchronous flowering pattern (with most culms of populations gregariously flowering in a year over a large area) and an asynchronous flowering pattern (with a small percentage of the culms of populations flowering before and after the mass-flowering year) for S. veitchii var. hirsuta. It was also clarified that the year and scale of mass flowering differ by area, and that mass flowering occurs in individual areas in successive years. The survey performed at the individual culm level revealed that the mean numbers of open florets and attached seeds per culm showed two peaks from April to July, suggesting that S. veitchii var. hirsuta flowering events occur twice a year.