Tolerance of five riparian plants from the lower Colorado River to salinity drought and inundation

Two greenhouse experiments were conducted to compare the effects of salt stress and water stress on four native riparian species and one invasive species collected from the lower Colorado River, Mexico. Within a drying soil at the control salinity level, Populus fremontii, Salix gooddingii and Baccharis salicifolia were able to extract water from the soil equal to that of Tamarix ramosissima and Pluchea sericea. Yet, at elevated salinity levels T. ramosissima and P. sericea exhibited a superior water-use ability. Under flooded conditions all native riparian species outperformed T. ramosissima. The results show that the invasive species T. ramosissima has a competitive advantage over native species mainly with respect to salt tolerance. This suggests that pulse flooding along the river could reduce Tamarix's competitive advantage by flushing out accumulated salts from the bankside and subjecting T. ramosissima to prolonged inundation.