Title

Secondary Invasions of Noxious Weeds Associated with Control of Invasive Tamarix are Frequent, Idiosyncratic and Persistent

Authors

Eduardo González, EcoLab (Laboratoire Ecologie Fonctionnelle et Environnement), Université de Toulouse, Department of Biological Sciences, University of Denver
Anna A. Sher, Department of Biological Sciences, University of DenverFollow
Robert M. Anderson, Department of Biological Sciences, University of Denver
Robin F. Bay, Department of Biological Sciences, University of Denver
Daniel W. Bean, Colorado Department of Agriculture, Biological Pest Control, Palisade Insectary
Gabriel J. Bissonnete, U.S. Bureau of Land Management
David J. Cooper, Department of Forest and Rangeland Stewardship, Colorado State University
Kara Dohrenwend, Rim to Rim Restoration
Kim D. Eichhorst, Bosque Ecosystem Monitoring Program (BEMP), Department of Biology, University of New Mexico
Hisham El Waer, Department of Biological Sciences, University of Denver
Deborah K. Kennard, Department of Physical and Environmental Sciences, Colorado Mesa University
Rebecca Harms-Weissinger, Northern Colorado Plateau Network, National Park Service
Annie L. Henry, Department of Biological Sciences, University of Denver
Lori J. Makarick, Grand Canyon National Park
Steven M. Ostoja, USDA California Climate Hub, Agricultural Research Service, University of California
Lindsay V. Reynolds, Department of Biology, Colorado State University
W. Wright Robinson, Grand County Weed Department
Patrick B. Shafroth, U. S. Geological Survey, Fort Collins Science Center
Eric Tabacchi, EcoLab (Laboratoire Ecologie Fonctionnelle et Environnement), Université de Toulouse

Document Type

Article

Publication Date

7-11-2017

Keywords

Ecological restoration, Invasive species management, Noxious weeds, Riparian systems, Secondary invasions, Tamarix control

Organizational Units

College of Natual Science and Mathematics, Biological Sciences

Abstract

Control of invasive species within ecosystems may induce secondary invasions of non-target invaders replacing the first alien. We used four plant species listed as noxious by local authorities in riparian systems to discern whether 1) the severity of these secondary invasions was related to the control method applied to the first alien; and 2) which species that were secondary invaders persisted over time. In a collaborative study by 16 research institutions, we monitored plant species composition following control of non-native Tamarix trees along southwestern U.S. rivers using defoliation by an introduced biocontrol beetle, and three physical removal methods: mechanical using saws, heavy machinery, and burning in 244 treated and 79 untreated sites across six U.S. states. Physical removal favored secondary invasions immediately after Tamarix removal (0–3 yrs.), while in the biocontrol treatment, secondary invasions manifested later (> 5 yrs.). Within this general trend, the response of weeds to control was idiosyncratic; dependent on treatment type and invader. Two annual tumbleweeds that only reproduce by seed (Bassia scoparia and Salsola tragus) peaked immediately after physical Tamarix removal and persisted over time, even after herbicide application. Acroptilon repens, a perennial forb that vigorously reproduces by rhizomes, and Bromus tectorum, a very frequent annual grass before removal that only reproduces by seed, were most successful at biocontrol sites, and progressively spread as the canopy layer opened. These results demonstrate that strategies to control Tamarix affect secondary invasions differently among species and that time since disturbance is an important, generally overlooked, factor affecting response.

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