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 st ress and water stress on four native riparian species and one invasive spec ies collected from the lower Colorado River, Mexico. Within a drying soil a t the control salinity level, Populus fremontii, Salix gooddingii and Bacch aris 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 competiti ve advantage over native species mainly with respect to salt tolerance. Thi s suggests that pulse flooding along the river could reduce Tamarix's compe titive advantage by flushing out accumulated salts from the bankside and su bjecting T. ramosissima to prolonged inundation. (C) 2001 Academic Press.