Submitted to: Western North American Naturalist
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/15/2006
Publication Date: 10/10/2007
Citation: Longland, W.S. 2007. Desert rodents reduce seedling recruitment of salsola paulsenii. Western North American Naturalist. 67:378-383. Interpretive Summary: Barbwire Russian thistle is an exotic plant that has become a very problematic invasive weed in arid environments of the southwestern US. In this study, I used fenced plots at a site in western Nevada to compare numbers of barbwire Russian thistle seedlings in areas that were inaccessible to seed-eating desert rodents versus directly comparable areas that were accessible to these animals. Nearly all such comparisons revealed that seedlings were less common in the presence than in the absence of rodents, indicating that foraging by desert rodents reduced the number of barbwire Russian thistle seeds in the soil, and thus the number of seedlings subsequently produced by this weed.
Technical Abstract: Heteromyid rodents in the deserts of North America have been shown to harvest large quantities of seeds of both native and introduced plants from soil seedbanks, but rarely has the impact of this seed removal been demonstrated experimentally. I used a series of fenced plots (some of which excluded rodents) to demonstrate that heteromyids at a western Nevada study site can measurably reduce seedbanks and subsequent seedling establishment of Salsola paulsenii, an introduced invasive weed that has become a significant problem over much of the desert southwest. The frequency of Salsola seedlings in both 2004 and 2005 was significantly greater around the interior perimeters of plots that permitted access by rodents than in plots that excluded rodents. Density of Salsola seedlings was significantly greater inside than outside rodent exclusion plots, but there was no such difference in seedling density inside versus outside plots that permitted rodent access. Salsola has such a conspicuous presence in many desert environments, such my study site, that the effects of rodents in reducing its abundance may not be visually apparent, but this may still ameliorate competitive effects of this weed on coexisting plants.