Salter, Jacqueline, Morris, Kay and Boon, Paul I (2008) Does salinity reduce the tolerance of two contrastingwetland plants, the submerged monocot Vallisneria australis and the woody shrub Melaleuca ericifolia, to wetting and drying? Marine and Freshwater Research, 59 (4). pp. 291-303. ISSN 1323-1650

Abstract

Adverse hydrological regimes and secondary salinisation are ubiquitous stressors to wetland plants in southeastern Australia. To test whether salinity stress interacts with hydrological stress to affect the growth and survival of aquatic plants,we examined the responses of Melaleuca ericifolia Smith, a shrub favouring drained sites, and the obligately submerged monocot Vallisneria australis (S.W.L. Jacobs & D.H. Les) to different hydrological regimes under freshwater and saline conditions. Under freshwater conditions both species recovered from water regimes that were considered prima facie unsuitable to their growth form: M. ericifolia from 5 and 10 weeks of submersion, and V. australis from a simulated water-level drawdown and exposure to air. Salinity, however, markedly compromised the survival of M. ericifolia after it was re-exposed following submersion. Salinity not only reduced the recovery ofV. australis after its release from a period of drying that desiccated aboveground organs, but prohibited recovery when the soil dried out.We conclude that M. ericifolia and V. australis can tolerate short periods of submergence and drying, respectively, under freshwater conditions, but that salinity compromises the ability of both taxa to recover from water regimes that, based on the plant’s growth form, would be considered unsuitable for long-term survival and growth.

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