Reproductive phenology of macrophyte community in response to wetland flooding cycle

Abstract

The phenology of macrophytes in response to environmental stressing factors is easily evidenced in wetlands under seasonal floods, such as the Pantanal. In these environments, the survival and establishment of seedlings of aquatic plants are restricted, limited to episodes with the presence of water, resulting in posterior sexual propagation for dispersal of seeds adapted to hydrochory, overcoming the dry period dormant in the sediment. We described the reproductive phenology of the macrophyte community in relation to the phases of flooding and between the species life forms. We sampled monthly the phenology of the macrophyte community of twenty ponds in the Pantanal, during two years, during the four phases of the flood pulse: ‘drought’, ‘rising’, ‘flood’ and ‘receding’. The peak of flowering and fruiting in species of community occurred at the begin of rising, under the influence of the water depth variation on flowering. The species with different life forms develop flowers and fruits in the phases with water (flooded). Amphibious species present wider phenological amplitude, flowering also in the drought phase. There is a correlation between the species flowering in the community and the water depth in the ponds, not observed when considering the life forms of the species. There is a correlation between flowering of amphibious plants and temperature, and rainfall; and a correlation between flowering rooted floating plants and temperature. The macrophyte community presents phenology associated to seasonal alterations of the flooding cycle, such as the presence and depth of water, by means of the diversified life histories and life forms, determining the dynamics, resistance and resilience of this flora in the Pantanal.