Half of the world’s land base is grazed by domesticated livestock. Because of the important functional role of ants in grasslands, it is important to understand the effect of livestock grazing on ant abundance and diversity. The objectives of this study were to examine the effect of cattle grazing and site productivity on the abundance, species richness, and species diversity of ants in Lac du Bois Grasslands Provincial Park, British Columbia, Canada. We hypothesized that the measured ant variables would be lowest in grazed areas and at low site productivity. Pitfall trapping was conducted at four sites: two at each low and high site productivity levels. At each site an ungrazed (fenced exclosure) and grazed transect was sampled during May, July, and August of 2008. Captured ants were preserved in ethanol and identified. Eight genuses of ants were collected: Tapinoma, Camponotus, Formica, Lasius, Aphaenogaster, Myrmica, Solinopsis, and Temnotharox. The mean number of ants per pitfall was higher at high site productivity sites that were grazed (15.10 6 2.96 SE) compared to high productivity sites ungrazed (3.28 6 0.47 SE); grazing at low productivity reduced numbers of ants from 5.07 (6 0.70 SE) to 2.20 (6 0.39 SE) (F 5 21.806; P , 0.001). Tapinoma sessile and A. occidentalis had the greatest numbers in the pitfall traps. Species richness (F 5 23.330, P , 0.001) and diversity (F 5 11.764, P 5 0.001) followed a similar trend. Because productivity and cattle grazing affect ant diversity and abundance, and ants impact ecosystem functioning, these factors should be considered in management of grasslands.Peer revieweddisturbanceFormicidaeproductivityrangelandssemiarid grassland

Grasslands are of vital importance to the ranching industry. Cattle grazing can alter the structure and composition of the plant community, and may indirectly affect insect communities. We investigated the effects of cattle grazing and site productivity on carabid beetle abundance, dried weight (biomass), species richness and diversity. We used pitfall traps to capture beetles in three sessions in 2008 in Lac Du Bois Provincial Park, British Columbia (B.C.), Canada. To test for main and interacting effects of elevation and grazing, carabid beetles were quantified by trap for abundance, dried weight (biomass), species richness and Shannon's diversity. We found that elevation (a proxy of site productivity) was the most important predictor of carabid parameters, with lower elevation (low site productivity) having lower abundance, biomass, species richness and diversity compared to upper elevation (high site productivity). Although there was no main effect caused by grazing, there was a reduction in carabid biomass and diversity at grazed upper elevation sites compared to ungrazed upper elevation sites, suggesting that site productivity and plant structure affects carabid communities. Cattle management of natural grasslands benefits by considering biodiversity of all biota, including invertebrates. Carabid species diversity can be maximized by restricting grazing at high site productivity where plant biomass and litter is high.