The Effects of Salinity and Flooding on Phragmites australis

Phragmites australis buds with attached rhizomes were planted in PVC tubes and grown under various salinity and flooding conditions in a greenhouse for one growing season. 2. P. australis buds did not emerge from cores flooded to the soil surface, regardless of salinity, indicating a possible lack of oxygen transport to below-ground structures. 3. Density, height and biomass were all negatively affected by increasing salinity (0, 15 and 30 g l1), as were recoverable underground reserves (RUR) and rhizome non-structural carbohydrate concentration (RNCC). 4. Height, biomass, RUR and RNCC decreased with increased flooding level (20 and 10 cm of the core above water level). 5. Cutting and flooding P. australis plants also reduced growth and survival in a separate outdoor experiment. When plants were cut and the stubble flooded with brackish (salinity 10gl-') water, there was no further above-ground growth for 18 months, i.e. all plants apparently died. 6. The results suggest that it may be possible to control P. australis stands in marshes by controlling water tables/flooding and salinity levels.