Introducing cattle grazing to a noxious
weed-dominated rangeland shifts plant communities
J.S. Davy, L.M. Roche, A.V. Robertson, D.E.
Nay and K.W. Tate.
California Agriculture 69(4):230-236.
DOI: 10.3733/ca.v069n04p230. October-December 2015.
Invasive weed species in California's rangelands can
reduce herbaceous diversity, forage quality and wildlife habitat. Small-scale
studies (5 acres or fewer) have shown reductions of medusahead and yellow
starthistle using prescribed grazing on rangelands, but little is published on
the effects of pasture-scale (greater than 80 acres) prescribed grazing on weed
control and plant community responses.
This study provides the results of a 6-year
collaborative study of manager-applied prescribed grazing implemented on
rangeland that had not been grazed for 4 years. Grazing reduced medusahead but
did not alter yellow starthistle cover. Medusahead reductions were only seen in
years that did not have significant late spring rainfall, suggesting that it is
able to recover from heavy grazing if soil moisture is present. Later season
grazing appears to have the potential to suppress medusahead in all years. In
practice, however, such grazing is constrained by livestock drinking water
availability and forage quality, which were limited even in years with late
spring rainfall. Thus, we expect that grazing treatments under real-world
constraints would reduce medusahead only in years with little late spring
rainfall. After 10 years of grazing exclusion, the ungrazed plant communities
began to shift, replacing medusahead with species that have little value, such
as ripgut and red brome.
Read the full report at: http://ucanr.edu/repositoryfiles/cav6904p230-159795.pdf
