Growth Characteristics of Bolboschoenus planiculmis on the Eulsuk Tidal Flat of the Nakdong River Estuary, Korea.
Bolboschoenus planiculmis is an important prey species for winter migratory birds in the Nakdong River Estuary region, but its population has declined in the last decade due to a physio-chemical shift. To identify the growth and development characteristics of B. planiculmis, we carried out an experimental survey on the aboveground and belowground sections of B. planiculmis specimens in the Eulsuk tidal flat from April to September 2019. We divided the belowground area into two groups: a vegetation group in which B. planiculmis exists and a non-vegetation group in which B. planiculmis does not exist and measured the rate of tubers. We observed a 45% appearance frequency in the vegetation group and only a 5% frequency in the non-vegetation group, indicating that there were no supplies for plant growth. The mean density, length, and biomass of B. planiculmis aboveground were 166.90±149.62 n m-2, 44.39±5.45 cm, and 67.63±54.46 g DW m-2, respectively, which was approximately half of those obtained from the study in the Eulsuk tidal flat in 2002. Tuber number was the highest in the 15~25 cm deep layer (41.50%). The mean number of total tubers belowground was related to different sediment conditions (FS: flat surface, DS: disturbed surface) 251.75±16.86 n pot-1 for FS and 171.00±25.18 n pot-1 for DS, which was significantly different (total tubers: p<0.005). The mean biomass of B. planiculmis above-ground was 21.11±1.60 g DW pot-1 for FS and 15.41±1.38 g DW pot-1 for DS, which was significantly different (p<0.05). This research provides primary materials for the restoration of the Nakdong River Estuary, wintering sites for migratory birds, and protection of B. planiculmis.