Rare nationwide synchronized massive flowering and decline event of <Emphasis Type="Italic">Sasa borealis</Emphasis> (Hack.) Makino in South Korea

Sasa borealis, a monocarpic species of dwarf bamboo, is widely distributed throughout Korea. It dominates forest floors, thereby inhibiting mainly the biodiversity. Although it flowers very rarely, examples have recently been observed in multiple locations, providing a good opportunity to study reproduction phenomena, and to aid in biodiversity restoration. Therefore, we investigated the nationwide timing of flowering events by using data collected from a social network service (SNS). We also more closely examined flowering and decline event, focusing at the patch and culm levels on Mt. Jeombong. We then analyzed the main factors affecting flowering. Our SNS and survey results showed that S. borealis is in a current flowering cycle that started in 2013 and continues to the present (83% of all events happening within this period) with a peak in 2015 (48% of the cases occurring in that year). This clearly demonstrated nationwide, synchronized, and massive flowering. Although the culm density in patches was not related to flowering, patches with large culms tended to flower (F = 8.241, p = 0.01). We suspected that this nationwide flowering event was triggered by prolonged drought during the spring months of 2014 and 2015 (F = 5.207, p < 0.05), which led to concurrent, massive flowering in patches mature enough to do so. Because this species prefers a wet habitat, we concluded that severe, prolonged drought induced environmental stress for those plants. After flowering, culms in those particular patches tended to die off within one year. This large-scale synchronized decline should have an enormous effect on the vegetation dynamics of a forest dominated and suppressed by Sasa. Future investigations might incorporate methods of ecological control and manipulation to increase biodiversity there.