Seed germination and dispersal of Eleocharis acuta and Eleocharis sphacelata under experimental hydrological conditions

The occurrence and distribution of aquatic macrophytes within a wetland depends on the hydrological requirements of each species and the hydrological conditions. The aims of this study were to: (1) determine relationships between germination of Eleocharis acuta and Eleocharis sphacelata and hydrological regime, (2) determine the buoyancy of the seeds of E. acuta and E. sphacelata and hence their ability to disperse by hydrochory and (3) determine whether E. acuta and E. sphacelata exhibit dormancy. The seeds of E. acuta and E. sphacelata both germinated best on soil-soaked and when inundated for 80 days (to a depth of 5 cm). No seeds of either species germinated under rainfall conditions. Viability testing following the experiment showed that some seeds of both species remained ungerminated and viable following soaking, inundation and rainfall conditions for 90 days, demonstrating that E. acuta and E. sphacelata exhibit dormancy. At least 50% of E. acuta seeds floated for 32 days, while 50% of E. sphacelata seeds remained floating for at least 39 days. These germination and dispersal characteristics define where and when these Eleocharis species establish related to temporal and spatial hydrological variability.