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Vegetation response to invasive Tamarix control in southwestern U.S. rivers: a collaborative study including 416 sites
Author(s) -
González Eduardo,
Sher Anna A.,
Anderson Robert M.,
Bay Robin F.,
Bean Daniel W.,
Bissonnete Gabriel J.,
Bourgeois Bérenger,
Cooper David J.,
Dohrenwend Kara,
Eichhorst Kim D.,
El Waer Hisham,
Kennard Deborah K.,
HarmsWeissinger Rebecca,
Henry Annie L.,
Makarick Lori J.,
Ostoja Steven M.,
Reynolds Lindsay V.,
Robinson W. Wright,
Shafroth Patrick B.
Publication year - 2017
Publication title -
ecological applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.864
H-Index - 213
eISSN - 1939-5582
pISSN - 1051-0761
DOI - 10.1002/eap.1566
Subject(s) - tamarix , vegetation (pathology) , invasive species , abundance (ecology) , revegetation , ecology , riparian zone , environmental science , native plant , introduced species , habitat , agronomy , biology , ecological succession , medicine , pathology
Most studies assessing vegetation response following control of invasive Tamarix trees along southwestern U.S. rivers have been small in scale (e.g., river reach), or at a regional scale but with poor spatial‐temporal replication, and most have not included testing the effects of a now widely used biological control. We monitored plant composition following Tamarix control along hydrologic, soil, and climatic gradients in 244 treated and 172 reference sites across six U.S. states. This represents the largest comprehensive assessment to date on the vegetation response to the four most common Tamarix control treatments. Biocontrol by a defoliating beetle (treatment 1) reduced the abundance of Tamarix less than active removal by mechanically using hand and chain‐saws (2), heavy machinery (3) or burning (4). Tamarix abundance also decreased with lower temperatures, higher precipitation, and follow‐up treatments for Tamarix resprouting. Native cover generally increased over time in active Tamarix removal sites, however, the increases observed were small and was not consistently increased by active revegetation. Overall, native cover was correlated to permanent stream flow, lower grazing pressure, lower soil salinity and temperatures, and higher precipitation. Species diversity also increased where Tamarix was removed. However, Tamarix treatments, especially those generating the highest disturbance (burning and heavy machinery), also often promoted secondary invasions of exotic forbs. The abundance of hydrophytic species was much lower in treated than in reference sites, suggesting that management of southwestern U.S. rivers has focused too much on weed control, overlooking restoration of fluvial processes that provide habitat for hydrophytic and floodplain vegetation. These results can help inform future management of Tamarix ‐infested rivers to restore hydrogeomorphic processes, increase native biodiversity and reduce abundance of noxious species.