Variation in salinity tolerance and water use strategies in an introduced woody halophyte (Tamarix spp.)

1. The form and function of terrestrial plants is largely governed by the availability of water, with plants in water limited environments expressing traits minimizing water loss and tissue damage during drought. Areas with high salinity are analogous to those with low water availability, even where water is abundant. We evaluated variation in salinity tolerance and water use strategies in an introduced halophytic shrub, Tamarix spp by measuring gas exchange rates, biomass accumulation, and turgor loss points. We hypothesized that salinity tolerance is not uniformly expressed, with high salinity ecotypes expressing more conservative water use traits that maximize hydraulic safety over high conductance rates.

2. We studied two populations of Tamarix spp. along the lower Colorado River where groundwater salinity differed by nearly six-fold. Cuttings collected from the sites were grown in a greenhouse with five salinity levels from 0 to 32 parts per thousand (ppt), imposing increasing w...