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United States Department of Agriculture

Agricultural Research Service

Title: Vegetation Response to Seven Grazing Treatments in the Northern Great Plains

Authors
item VERMEIRE, LANCE
item Heitschmidt, Rodney
item Haferkamp, Marshall

Submitted to: Agriculture, Ecosystems and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 4, 2007
Publication Date: January 4, 2008
Citation: Vermeire, L.T., Heitschmidt, R.K., Haferkamp, M.R. 2008. Vegetation Response to Seven Grazing Treatments in the Northern Great Plains. Agriculture, Ecosystems and Environment 125:111-119.

Interpretive Summary: Grazing strategies may alter botanical composition and productivity of rangelands through differential use in time, space, or intensity. Seven simulated grazing strategies were applied six years in eastern Montana to determine effects on plant community composition and standing crop. Treatments were moderate stocking of cattle using 3-pasture rotation, season-long, high-intensity low-frequency, short-duration, 3-pasture winter rotation, and spring calving systems. The final treatment was severe growing season grazing. Treatments were randomly assigned to 14, 6.1-ha pastures. Post-treatment grass and total standing crops were 49 and 54% of their pre-treatment measures because of extended drought. Cacti increased from 0 to 80 kg•ha-1 over the same period. No single grazing system affected standing crop of any herbage component. Standing crops of western wheatgrass, other perennial cool-season grasses, perennial warm-season grasses, and shrubs were similar across grazing treatments. Severe grazing produced twice as many forbs (142 kg•ha-1) as moderate stocking. Annual grasses increased from 134 kg•ha-1 on pastures grazed after May to 362 kg•ha-1 on pastures grazed before June. Cacti also increased from 47 to 187 kg•ha-1 on early-grazed pastures. Rotational and continuous grazing strategies produced similar effects on all vegetation components. Grazing systems were not effective in altering standing crop or functional group composition after six years of treatment and one year of rest. Standing crop changes over time and limited shifts in forbs, cacti, and annual grasses indicate northern mixed prairie is most responsive to weather, with stocking rate and timing of grazing contributing minor influences.

Technical Abstract: Grazing strategies may alter botanical composition and productivity of rangelands through differential use in time, space, or intensity. Seven simulated grazing strategies were applied six years in eastern Montana to determine effects on plant community composition and standing crop. Treatments were moderate stocking (28.8 AUD•ha**-1•y**-1) of cattle using 3-pasture rotation, season-long, high-intensity low-frequency, short-duration, 3-pasture winter rotation, and spring calving systems. The final treatment was severe growing season grazing (108.2 AUD•ha**-1•y**-1). Treatments were randomly assigned to 14, 6.1-ha pastures. Post-treatment grass and total standing crops were 49 and 54% of their pre-treatment measures because of extended drought. Cacti increased (P<0.02) from 0 to 80 +_ 17 kg•ha**-1 over the same period. No single grazing system affected standing crop of any herbage component. Standing crops of Pascopyrum smithii Rydb. (Love) (691 +_ 200 kg•ha**-1; P > 0.78), other perennial C3 grasses (95 +_ 135 kg•ha**-1; P > 0.80), perennial C4 grasses (186 +_ 114 kg•ha**-1; P > 0.13), and shrubs (13 +_ 34 kg•ha**-1; P > 0.57) were similar across grazing treatments. Severe grazing produced more forbs (142 +_ 16 kg•ha**-1; P < 0.01) than moderate stocking (67 +_ 16 kg•ha**-1). Annual grasses increased (P < 0.01) from 134 +_ 54 kg•ha**-1 on pastures grazed after May to 362 +_ 54 kg•ha**-1 on pastures grazed before June. Cacti also increased (P < 0.03) from 47 to 187 +_ 52 kg•ha**-1 on early-grazed pastures. Rotational and continuous grazing strategies produced similar effects on all vegetation components. Grazing systems were not effective in altering standing crop or functional group composition after six years of treatment and one year of rest. Standing crop changes over time and limited shifts in forbs, cacti, and annual grasses indicate northern mixed prairie is most responsive to weather, with stocking rate and timing of grazing contributing minor influences.

Last Modified: 9/10/2014
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