Ant communities and livestock grazing in the Great Basin, USA

TitleAnt communities and livestock grazing in the Great Basin, USA
Publication TypeJournal Article
Year of Publication2001
AuthorsNash M.S., Whitford WG, Bradford D.F., Franson S.E., Neale A.C., Heggem D.T.
JournalJournal of Arid Environments
Volume49
Pagination695-710
Date PublishedDecember 1, 2001
ARIS Log Number150386
AbstractThe objectives of this study were to determine if metrics for ant species assemblages can be used as indicators of rangeland condition and to determine the influence of vegetation and ground cover variables, factors often influenced by livestock grazing, on ant communities. The study was conducted in two areas in the Great Basin: a sagebrush-steppe in southeastern Idaho (n = 30 sites) and salt-desert shrub in western Utah (n = 27 sites). Sites were selected based on known rangeland conditions (i.e., good, fair, poor) associated with livestock grazing. Ant communities differed considerably between the two study areas. Collectively, more ant species occurred at the Idaho sites (30) than at the Utah sites (21), relatively few species (8) occurred in both areas, species richness was significantly greater at the Idaho sites (mean = 12(.)0 species) than the Utah sites (mean = 6(.)9 species), and Formica spp. were diverse (total of 15 species) at the Idaho sites but rate (1 species) at the Utah sites. In Idaho, all species collectively, generalists and Formica spp., were significantly less abundant on sites in poor condition than that on sites in good or fair condition; whereas in Utah, seed harvesters and Pheidole spp. were significantly more abundant on sites in poor condition than on sites in good or fair condition. In Idaho, species richness was significantly lower on sites in poor condition. In Idaho, species richness and relative abundances of several ant groups were significantly related to bare patch size and parameters for cover or species richness of several vegetation groups. In contract to the comparisons involving sites in poor condition, no differences in any communities in either Idaho or Utah were evident between sites in good and fair condition. Thus, the ant communities responded only to large changes in rangeland condition and to large differences in climatic/edaphic conditions between the two areas. Hence, ant community metrics appear to have limited utility as indicators of rangeland condition in the Great Basin.
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