Vegetation response to seven grazing treatments in the Northern Great Plains

• Published in: Agriculture, ecosystems & environment ecosystems & environment, 2008-05, Vol.125 (1), p.111-119
• Main Authors: Vermeire, Lance T., Heitschmidt, Rodney K., Haferkamp, Marshall R.
• Format: Article
• Language: English
• Subjects: Agnatha. Pisces; Agronomy. Soil science and plant productions; annuals; Biological and medical sciences; botanical composition; Bromus; C3 plants; C4 plants; cacti and succulents; crop yield; drought; dry matter accumulation; forbs; functional diversity; Fundamental and applied biological sciences. Psychology; General agroecology; General agroecology. Agricultural and farming systems. Agricultural development. Rural area planning. Landscaping; General agronomy. Plant production; Generalities. Agricultural and farming systems. Agricultural development; grasses; Grassland; grasslands; grazing; grazing management; Mixed prairie; Pascopyrum smithii; perennials; range management; Rangeland; rangelands; Rotational grazing; seasonal variation; Standing crop; Stocking rate; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
• ISSN: 0167-8809; 1873-2305
• DOI: 10.1016/j.agee.2007.12.003

Grazing systems may alter botanical composition and productivity of grasslands through differential use in time, space, or intensity. Seven simulated grazing treatments were applied six years in eastern Montana, USA to determine effects on plant community composition and standing crop. Treatments were moderate stocking (28.8 AUD ha −1 year −1) of cattle using 3-pasture summer 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 year −1). Treatments were randomly assigned to 14, 6.1-ha pastures. Post-treatment grass and total standing crops were 54 and 58% of their pre-treatment measures because of extended drought. No single grazing system affected standing crop of any herbage component. Standing crops of Pascopyrum smithii Rydb. (Love) (674 ± 186 kg ha −1; P > 0.69), other perennial C 3 grasses (102 ± 156 kg ha −1; P > 0.77), perennial C 4 grasses (178 ± 111 kg ha −1; P > 0.22), 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 C 3 grasses increased ( P < 0.01) from 131 ± 55 kg ha −1 on pastures grazed after May to 362 ± 55 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. Greater total standing crop on pastures grazed before June ( P < 0.03) was accounted for by increases in annual C 3 grasses and cacti. 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 one year after six years of treatment. Standing crop changes over time and limited shifts in forbs, cacti, and annual C 3 grasses indicate northern mixed prairie is most responsive to weather, with stocking rate and timing of grazing contributing minor influences.