Regenerative strategies of aquatic macrophytes in flood disturbed habitats: the role of the propagule bank

Citation

Combroux I, Bornette G, Willby N & Amoros C (2001) Regenerative strategies of aquatic macrophytes in flood disturbed habitats: the role of the propagule bank. Archiv fur Hydrobiologie, 152 (2), pp. 215-235.

Abstract
Recovery of plants from disturbance is frequently associated with the presence of an extensive seed bank. In a cut-off channel of the Rhône River subjected to fluctuating water levels and scouring forces during flash floods, regenerative strategies of aquatic plants were investigated through the study of the sediment propagule bank and its comparison with the established vegetation. Within this channel, the zone disturbed only by scouring floods (zone F) had a small propagule bank (as assessed by greenhouse germination trials), whereas more propagules regrew in zone FE which was subjected to both scouring floods and episodic sediment emersion. There, regrowth was mostly from sexual propagules, with the stonewort Chara vulgaris being the dominant component. In zone F, no relationship between propagule bank composition and established vegetation was demonstrated. In zone FE, a strong positive relationship between vegetative propagules (buds + rhizomes + fragments) and the established vegetation occurred. The disturbance history of the site indicated that the flowering and seed production of most species was disrupted by the flood regime, the result being that only one third of the hydrophyte species present in the established vegetation were present in the seed bank. Consequently, in this habitat, resistance type regenerative strategies, involving fragments and rhizomes, were adopted by most species. Resilience regenerative strategies involving seed- or bud-banks, together with resistance strategies involving the development of a terrestrial growth form, were adopted by plants that had to face both floods and sediment emersions. The precise nature of disturbance appears to affect regenerative strategies of aquatic plants and merits greater attention in studies of trait-environment relationship. The diversity of regenerative strategies within and between aquatic plant species is likely to contribute significantly to the underlying stability of vegetation in flood disturbed habitats.

Keywords
recovery of aquatic plants; seed-banks; floods; sediment emersions; Rhone River

Journal
Archiv fur Hydrobiologie: Volume 152, Issue 2