Product Type: Journal Article
Author(s): Merritt, D.M. and P.B. Shafroth
Merritt, D.M. and P.B. Shafroth. 2012. Edaphic, salinity, and stand structural trends in chronosequences of native and non-native dominated riparian forests along the Colorado River, USA . Biological Invasions 14(12): 2665-2685.
This publication is available from Springer Science+Business Media B.V. (outside the USA) .
Tamarix spp. are introduced shrubs that have become among the most abundant woody plants growing along western North American rivers. We sought to empirically test the long-held belief that Tamarix actively displaces native species through elevating soil salinity via salt exudation. We measured chemical and physical attributes of soils (e.g., salinity, major cations and anions, texture), litter cover and depth, and stand structure along chronosequences dominated by Tamarix and those dominated by native riparian species (Populus or Salix) along the upper and lower Colorado River in Colorado and Arizona/California, USA. We tested four hypotheses:
We found that salt concentration increases at a faster rate in Tamarix-dominated stands along the relatively freeflowing upper Colorado but not along the heavily regulated lower Colorado. Concentrations of ions that are known to be preferentially exuded by Tamarix (e.g., B, Na, and Cl) were higher in Tamarix stands than in native stands. Soil salt concentrations in older Tamarix stands along the upper Colorado were sufficiently high to inhibit germination, establishment, or growth of some native species. On the lower Colorado, salinity was very high in all stands and is likely due to factors associated with floodplain development and the hydrologic effects of river regulation, such as reduced overbank flooding, evaporation of shallow ground water, higher salt concentrations in surface and ground water due to agricultural practices, and higher salt concentrations in fine-textured sediments derived from naturally saline parent material.