Morphological responses to different flooding regimes in Carex brevicuspis

Water regime can be described by the depth, duration, frequency, and timing and predictability of flooded and dry phases. Despite growing recognition of the importance of water regimes in the regulation of plant growth and distribution, which components of water regimes that determine plant growth are not well known. To identify the causative components, 72 ramets of Carex brevicuspis were grown under six different water regime treatments (treatment A: constant 0 cm water level; treatment B: constant 30 cm water level; treatment C: 0 cm water level to 30 cm water level for 30 days, repeated 2 times; treatment D: 30 cm water level to 0 cm water level for 30 days, repeated 2 times; treatment E: 0 cm water level to 30 cm water level for 5 days, repeated 12 times; and treatment F: 30 cm water level to 0 cm water level for 5 days, repeated 12 times). Biomass accumulation, below: above ground biomass ratio, number of ramets, and proportions of spreading and clumping ramet were assessed. Biomass accumulation decreased only in relation to length of flooding. The highest biomass accumulation occurred in the 120-day. 0 cm water level treatment, it was intermediate in the four 60 day. 30 cm water level treatments, and lowest in the 120 day. 30 cm water level treatment. Likewise, the below: above ground ratio decreased only with increasing length of flooding. Ramet number was highest in the 120 day. 0 cm water level treatment, intermediate in the four 60 day. 30 cm water level treatments, and lowest in the 120 day. 30 cm water level treatment. The proportion of spreading ramets increased from 28.0% in the 120 day. 0 cm water level treatment to 76.4% in the 120 day. 30 cm water level treatment. These data suggest that the growth of C. brevicuspis was only limited by the duration of flooding. Reduction of the below: above ground ratio and change from phalanx to guerrilla growth form are effective strategies for C. brevicuspis to acclimate to flooding stress, because they allow the plant to grow above the water surface and escape from anoxic conditions. Our study provides experimental information on the role of different components of water regimes in regulating plant growth, and may assist in protection and restoration of the C. brevicuspis community.