Submitted to: Ecological Society of America Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2005
Publication Date: July 1, 2005
Citation: Vermeire, L.T., Heitschmidt, R.K., Haferkamp, M.R. 2005. Northern plains plant community response to 10 years of livestock exclusion. Ecological Society of America Abstracts 90:661. Technical Abstract: Livestock exclusion has been proposed to restore rangeland health. However, herbivory is a key characteristic of many rangelands. We hypothesized that current year biomass, species composition, and species richness would be similar on livestock-grazed and livestock-excluded sites over a 10-year period. Four 12.1-ha livestock exclosures were established and paired with adjacent, moderately-grazed sites in 1993. Current year live and dead biomass were sampled annually by species and species groups from 1994 through 2003 to assess effects of livestock grazing and livestock removal on plant community composition in a northern mixed prairie. Carex filifolia, Koeleria macrantha, non-Bromus annual grasses, other perennial C3 grasses, forbs, woody plants, and cacti comprised about 22% of the biomass and each was similar across years and grazing treatments. Pascopyrum smithii, Poa secunda, Hesperostipa comata, C4 shortgrasses, and other perennial C4 grasses, and total biomass varied annually, but biomass of each was similar between grazing treatments. These species accounted for about 59% of the biomass. Year-by-grazing interactions occurred for annual brome biomass and composition, and C4 shortgrass composition. Annual brome biomass was greater within exclosures 2 years and composition was greater within exclosures 3 years. Annual bromes were greater on grazed sites only during 1996. The cause of increased annual brome on grazed sites is not readily explainable and brome frequency was similar between grazing treatments in 1996. Annual brome biomass, composition, or frequency was greater within exclosures from 1999 to 2003. From 2000 to 2003, C4 shortgrass composition was greater on grazed sites. Species richness varied by year (5 to 8 species per 0.25 m2), but was similar between grazing treatments. Introduced species were more abundant within exclosures (233 kg ha-1) than on grazed sites (71 kg ha-1). Exclosures and grazed sites were largely similar. However, livestock exclusion appeared to increase the presence of annual bromes and introduced species as a whole. There was no indication that livestock exclusion increased biomass or improved plant community integrity.