The effects of salinity and flooding on Phragmites australis

Published source details Hellings S.E. & Gallagher J.L. (1992) The effects of salinity and flooding on Phragmites australis. Journal of Applied Ecology, 29, 41-49.
Share Tweet Email

Summary

The need to control common reed Phragmites australis in the tidal marshes of Delaware and other mid-Atlantic US states became a priority of coastal zone managers due to a dramatic expansion in the area occupied by this robust grass. Mowing and burning has been attempted as a means of control but has usually resulted in little or no success. Herbicide control may be effective but may not be compatible with other marsh management objectives. This study examined the effects of water salinity and flooding conditions on P.australis growth in a glasshouse experiment.

Study site: This glass house study was undertaken at the Halophyte Biology Laboratory in Lewes, Delaware, USA.

Experimental design: In spring 1988 three watertight wooded boxes (70 x 170 x 60 cm deep) where placed in the glasshouse and filled to 50 cm woth water of 0, 15 or 30 g/L salinity. Two wooden platforms were placed in each box resulting in three warter levels and drainage conditions (i.e. soil added up to the surface, 10 cm or 20 cm above the constant water level)

P.australis buds with attached rhizomes were planted in PVC tubes (15 cm diameter, 50 cm long filled with dredge material from the collection site near the Halophyte Biology Laboratory) and grown under these various salinity and flooding conditions for one growing season.

Reed survival: After 9 weeks, P.australis buds did not emerge from 17 of 18 cores flooded to the soil surface, regardless of salinity. When extracted, these plants were sulphidic and flaccid indicating a possible lack of oxygen transport to below-ground structures. Survival was otherwise generally very high.

Effects of salinity: Culm density (0 g/L salinity: 2,200; 15 g/L salinity: 1,400; and 30 g/L salinity: 900 culms/m²), height (0: 200 cm; 15: 140 cm; and 30: 100 cm) and biomass (0: c.9,000; 15: c.3,800 ; and 30: c.1,900 g/m²) were all negatively affected by increasing salinity, as were recoverable underground reserves (RUR) and rhizome non-structural carbohydrate concentration (RNCC).

Effects of flooding: Height (10 cm soil: 120 cm tall; 20 cm soil: 160 cm tall) , biomass (10 cm soil: 3,100; 20 cm soil: 5,000 g/m²), RUR and RNCC decreased with increased flooding level (20 and 10 cm of the core above water level). Culm density was about equal for these two core heights (10 cm soil: 1,400; 20 cm soil: 1,500 culms/m²).

Conclusions: The results of this glass house experiment suggest that it may be possible to control P.australis stands in marshes by controlling water tables/flooding and salinity levels in areas where this is feasible.

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: