Control of Tamarix in the Western United States: Implications for Water Salvage, Wildlife Use, and Riparian Restoration

Abstract

Non-native shrub species in the genus Tamarix (saltcedar, tamarisk) have colonized hundreds of thousands of hectares of floodplains, reservoir margins, and other wetlands in western North America. Many resource managers seek to reduce saltcedar abundance and control its spread to increase the flow of water in streams that might otherwise be lost to evapotranspiration, to restore native riparian (streamside) vegetation, and to improve wildlife habitat. However, increased water yield might not always occur and has been substantially lower than expected in water salvage experiments, the potential for successful revegetation is variable, and not all wildlife taxa clearly prefer native plant habitats over saltcedar. As a result, there is considerable debate surrounding saltcedar control efforts. We review the literature on saltcedar control, water use, wildlife use, and riparian restoration to provide resource managers, researchers, and policy-makers with a balanced summary of the state of the science. To best ensure that the desired outcomes of removal programs are met, scientists and resource managers should use existing information and methodologies to carefully select and prioritize sites for removal, apply the most appropriate and cost-effective control methods, and then rigorously monitor control efficacy, revegetation success, water yield changes, and wildlife use.

Development of a decision support tool for water and resource management using biotic, abiotic, and hydrological assessments of Topock Marsh, Arizona

“…This deep-rooted phreatophyte (groundwater-dependent plant) often has significant effects on the water table in arid environments, particularly in thick-canopied stands with high evapotranspiration (Shafroth et al 2005). Dense tamarisk monocultures on stream banks accumulate sediment in their extensive root systems, which may benefit erosion control in some habitats, while in others may narrow stream channels and increase flooding potential (Sher and Quigley 2013).…”

Use of tamarisk as a potential feedstock for biofuel production.

“…Nevertheless, riparian restoration efforts following tamarisk removal have led to minimal water recovery as evapotranspiration rates of native vegetation are often similar to that of tamarisk [Shafroth, 2005;Tamarisk Coalition, 2009]. Control of tamarisk is considered a practical approach to realizing restoration goals rather than total eradication due to cost and ecological concerns.…”

“…Saltcedar is viewed to have negative ecological and economic effects in riparian environments including streamflow depletion from increased evapotranspiration rates, displacement of native vegetation, and increased soil salinity [Shafroth, 2005]. Nevertheless, riparian restoration efforts following tamarisk removal have led to minimal water recovery as evapotranspiration rates of native vegetation are often similar to that of tamarisk [Shafroth, 2005;Tamarisk Coalition, 2009].…”

An analytic solution for groundwater uptake by phreatophytes spanning spatial scales from plant to field to regional

“…The discharge vector associated with a phreatophyte located at z p is obtained through the integration process in (11). For a uniform groundwater uptake, this gives…”

“…At a global scale, phreatophytes redistribute soil water by drawing water upward and depositing it in drier surface layers, which significantly increases photosynthesis and evapotranspiration, and establishes a direct link between plant-root functioning and global climate [9]. Within riparian corridors, phreatophytes impact flood intensity and channelization of stream networks, and provide wildlife habitat and migratory routes for birds [10,11]. While phreatophytes do not directly tap surface water [12], they may intercept groundwater and change the dynamics of groundwater-surface water interactions with consequences to biomass production and species diversity [13].…”