Soil Properties and Species Diversity of Grazed Crested Wheatgrass and Native Rangelands

Abstract

Crested wheatgrass (Agropyron cristatum (L.) Gaertn.) is an introduced grass used extensively for rangeland revegetation in the semiarid and arid regions of western North America. The long-term effects of crested wheatgrass on soil properties and plant community were evaluated on 5 grazed sites in the south ern interior of British Columbia, Canada. Each site included plant communities of native bluebunch wheatgrass (Pseudoroegneria spicata (Pursh) Scribn. & Smith) and 14- to 60year-old stands of crested wheatgrass. Soil samples and plant data were collected in June 1997. Species numbers were similar for native and crested wheatgrass rangelands, while the diversity index of crested wheatgrass rangeland was lower due to lower evenness. Crested wheatgrass and native grasses were observed to produce similar amounts of root biomass. Most soil properties were similar under the 2 rangelands. One of the exceptions was soil carbon at 0‐7.5 and 7.5‐15 cm depths, which was higher on crested wheatgrass than native rangeland. Soil nitrogen at 15‐30 cm depth was also higher on crested wheatgrass rangeland. Greater soil penetration resistance was observed at 7.5 and 9 cm depths on crested wheatgrass than native rangeland. Higher soil compaction was caused by grazing of crested wheatgrass earlier in the season when soils are wetter relative to the native range land. The results of this study indicate that seeding of crested wheatgrass combined with the long-term grazing by cattle did not result in the degradation of soil properties, but plant diversi ty was reduced relative to grazed native, bluebunch wheatgrass rangeland.