Riparian plant communities remain stable in response to a second cycle of Tamarix biocontrol defoliation

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Reduced abundance of non-native Tamarix shrubs in western U.S. riparian systems following biological control by a defoliating beetle has led to concerns that replacement plant communities could be dominated by other invasive species and/or not provide some of the ecosystem services that Tamarix was providing. In previous studies, Tamarix decline following biocontrol was accompanied by small increases in native and non-native herbaceous species, with variable responses of woody vegetation. However, none of these studies spanned periods longer than a decade since beetle release. This is an important caveat, given the cyclical nature of plant-herbivore interactions and potential lags in vegetation recovery. We report plant community response to an eight-year-long second cycle of Tamarix defoliation-refoliation in two reaches of the upper Colorado River in eastern Utah, 11–13 years after beetle arrival. Tamarix cover across sites initially declined an average of ca. 50% in response to the beetle, but then recovered. Changes in the associated plant community were small but supported common management goals, including a 47% average increase in cover of a native shrub (Salix exigua), and no secondary invasions by other non-native plants. We suggest that the effectiveness of biocontrol programs must be assessed case-by-case, and on a long-term basis.

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Publication type Article
Publication Subtype Journal Article
Title Riparian plant communities remain stable in response to a second cycle of Tamarix biocontrol defoliation
Series title Wetlands
DOI 10.1007/s13157-020-01381-7
Volume 40
Issue 6
Year Published 2020
Language English
Publisher Springer
Contributing office(s) Fort Collins Science Center, Southwest Biological Science Center, Western Ecological Research Center
Description 13 p.
First page 1863
Last page 1875
Country United States
State Utah
Other Geospatial Upper Colorado River
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