Propagule banks and regenerative strategies of aquatic plants

Abstract

The role of the propagule bank in aquatic plant maintenance was studied in two riverine wetlands. Four sites were selected, characterized respectively by flooding, drying up, both disturbances operating, and neither operating. Our hypothesis was that recolonization after drying up would mostly involve seeds and buds from the propagule bank, whereas recolonization after floods would mostly involve rhizomes. Dry sites were characterized by a high density of seeds, and a high similarity between seed species and established vegetation. Unspecialized fragments remaining in wet parts of the sediment probably also contribute to species maintenance. Species maintenance in sites subjected to flooding was highly dependent on deeply anchored rhizomes, as indicated by the strong floristic similarity between species that occur in the established vegetation and rhizomes in the bank. Regeneration of the community after scouring floods also involved seeds, some species being able to flower under water. When scouring flooding and drying up were superimposed, regenerative strategies exhibited in the bank did not simply result from the 'addition' of the two disturbance effects. When the disturbances did not occur too closely together in time, species were able to survive either by: (1) producing many propagules under aquatic conditions or (2) coping with the temporal variability by producing several types of propagules.

Does mechanical disturbance affect the performance and species composition of submerged macrophyte communities?

“…Previous studies showed that fragmentation into small pieces caused by mechanical disturbance can affect the growth of wetland plants36434445. In the present study, strong mechanical disturbance greatly decreased the growth of the submerged macrophyte communities.…”

Fragment Propagation and Colonization Ability Enhanced and Varied at Node Level after Escaping from Apical Dominance in Submerged Macrophytes

“…It is widely known that most aquatic plants exhibit asexual reproduction by forming specialized propagules, like stolons, rhizomes and turions, or unspecialized fragments (Van et al 1978; Titus and Hoover 1991; Barrat‐Segretain 1996). Some early reports found that the scouring caused by flooding favored regeneration through unspecialized fragments in aquatic plants and these fragments contributed to species maintenance (Combroux and Bornette 2004). Then, if an unpredictable disturbance like flood or grazing occurs, these plants, particularly the fragile submerged macrophytes, may be fragmented and the fragments may be then washed away by running water and dispersed to other habitats (Johansson and Nilsson 1993; Barrat‐Segretain et al 1998).…”

Effects of Water Level Fluctuations on Spawning Habitat of an Endangered Species, the Australian Lungfish (Neoceratodus Forsteri)

“…), which do not have mechanisms for minimizing water loss (Salter et al ., ). Populations can recover following re‐inundation via regeneration from vegetative organs (rhizomes and turions) or germination from seedbanks (Madsen and Smith, ; Casanova and Brock, ; Combroux et al ., ; Combroux and Bornette, ). However, prolonged desiccation can cause damage to belowground organs, thus impairing the plant's ability to recolonize after re‐inundation (Harwell and Havens, ; Salter et al ., ).…”