Response of the soil nematode community in a shortgrass steppe to long-term and short-term grazing

Abstract

Nematode abundance and community structure were used to determine if grazing by cattle was a disturbance to soil. Soil samples were collected in bare ground, interplant spaces and under Bouteloua gracilis (H.B.K.) Lag. ex Griffiths (blue grama) in the arid shortgrass steppe of Colorado. Grazing treatments were long-term grazed (GG), long-term ungrazed (UU), short-term grazed (UG) and short-term ungrazed (GU). Long-term treatments were fifty-five years old. The short-term treatments were either grazed (GU) or ungrazed (UG) from 1939–1991, and then ungrazed or grazed for 2 years, from 1992–1994. Bacterial feeding nematodes and plant parasitic nematodes were the dominant nematode trophic groups. Grazing treatments had no effect on nematode absolute abundances, but did influence the percent contribution of fungal feeding nematodes. Total nematodes were higher in the under-plant locations, as were all trophic groups except omnivores and predators which had similiar densities in both locations. However, on a percentage basis, community composition was similar except for omnivores which were higher in the interplant location. These results suggest that grazing has no effect on belowground biota in the shortgrass steppe, with the exception of fungal feeding nematodes.