Seasonal flooding regime effects on the survival, growth, and reproduction of Bolboschoenus planiculmis under East Asian monsoon

Abstract

Seasonal flooding regimes are key hydrodynamic features in estuarine ecosystems, and are mainly influenced by climatic conditions. Today, the original seasonal flooding regimes can be altered due to artificial infrastructure or following sea-level rise. Although the altered flooding regimes determine flooding duration and depth, which further influence growth and development of marsh plants, little is known about the effects of seasonal flooding regimes on marsh plants under the East Asian monsoon climate zone. Therefore, we investigated the effects of different seasonal flooding regimes on survival, growth, and reproduction of the marsh plant Bolboschoenus planiculmis. A greenhouse experiment was conducted to compare the responses of B. planiculmis under combinations of four flooding durations (0-month, 2-month, 3.5-month, and 5-month) and flooding depths (0-cm, 20-cm, and 40-cm). Flooding duration affected the survival and growth of B. planiculmis: Extended flooding (5-month) decreased the survival rate and initial shoot density, while shoot length and biomass increased under extended (5-month) and natural (3.5-month) seasonal flooding after shoots reached the water surface. The flooding depth affected sexual reproduction: Medium flooding depth (20-cm) resulted in the highest flowering rate. According to the results, the natural seasonal flooding duration in the East Asian monsoon climate did not negatively influence survival, growth, and reproduction of B. planiculmis. However, if the seasonal flooding duration was extended, B. planiculmis responded negatively to survival and growth during the young stage. The shortened seasonal flooding duration resulted in the repressed shoot length and biomass of B. planiculmis. For the sustainable conservation of B. planiculmis under East Asian monsoon, it is important to maintain the original seasonal flooding regimes and minimize the effects of embankment on the seasonal flooding regimes.