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Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/9/2012 Publication Date: 4/1/2012 Citation: Longland, W.S. 2012. Small mammals in saltcedar (Tamarix ramosissima) - invaded and native riparian habitats of the western Great Basin. Journal of Invasive Plant Science and Management. 5:230-237. Interpretive Summary: Invasion of riverside vegetation by saltcedar species changes the appearance of these “riparian” habitats in the arid western US conspicuously. Because riparian environments are rare on arid lands yet support a large number of animal species, there is considerable concern regarding effects of saltcedar invasion on wildlife. Small mammals were monitored annually for up to 10 years at several sites in the western Great Basin in both saltcedar-invaded and native riparian habitats. The number of small mammal species live-trapped was similar for native and saltcedar habitats. A general effect of saltcedar invasion was an increase in rodents in the “heteromyid” family. This is consistent with well known adaptations of these rodents to open, arid environments and conversion of riparian areas to more open, desert-like habitats at many sites invaded by saltcedar. By contrast, rodent species such as montane voles and western harvest mice that are typically associated with native riparian vegetation tended to be uncommon or absent in saltcedar-converted habitat. Such species may provide useful indicators of habitat conditions in mixed native and saltcedar riparian woodlands, such as in the intermediate stages of invasion. An insect introduced for biological control of saltcedar has not had any consistent effects on small mammals. Technical Abstract: Invasive saltcedar species have replaced native riparian trees on numerous river systems throughout the western US, raising concerns about how this habitat conversion may affect wildlife. For periods ranging from 1-10 years, small mammal populations were monitored at six riparian sites impacted by saltcedar in western Nevada and eastern California. At five of these sites, saltcedar and native riparian woodlands were trapped simultaneously. Small mammal species richness was generally similar in saltcedar and native habitats. Heteromyid rodents were more likely to occur in saltcedar habitats, but other rodent species, particularly the montane vole and western harvest mouse, occurred more often in native habitats. The most common species at all sites, the deer mouse, occurred in similar frequencies in the two habitat types and showed no habitat-specific differences in mean body mass or sex ratio. However, an uncommon congener, the pinyon mouse, had greater mean body mass in native habitats than in saltcedar. A biological control insect that defoliates saltcedar has not yet had any conspicuous effects on small mammals. However, two species showed trends toward increasing capture frequencies as biological control progressed, and recapture frequencies of western harvest mice have decreased in saltcedar habitats at some sites. |
