Impact of Combined Grazing by Prairie Dogs with Goats or Cattle on Vegetation and Hydrology of a Chihuahuan Desert Grassland

Abstract

Impact of combined grazing by prame dogs with goats or cattle on
vegetation and hydrology of a Chihuahuan desert grassland of northern Mexico
was assessed. Twice replicated grazing treatments were: (1) yearlong continuous
goat grazing at a high intensity in a prairie dog colony, and (2) sequential rotation grazing
by cattle along with prairie dogs at a moderate intensity. The pasture grazed by
prairie dogs with cattle supported fewer plant species (n = 50) than the pasture
grazed by goats with prairie dogs (n = 63). The synergistic grazing by goats and
prairie dogs caused a 68% reduction in the aboveground biomass, with a directional
change favoring herbaceous vegetation at the expense of grasses. The average biomass
production of forbs increased 65% and the average grass standing crop decreased
by 400% under the combined grazing regime of prairie dogs and goats, in comparison
to the pasture grazed by prairie dogs and cattle. Most forbs with higher contribution
to the total standing crop on the site grazed by prairie dogs and goats were non-edible.
The standing crop of shrubs was higher (P<0.05) on the site grazed by prairie
dogs and goats than the site grazed by prairie dog and cattle.· Plant diversity was
higher on the pasture grazed by prairie dogs and goats than the pasture grazed
by prairie dogs and cattle. The infiltration rate was higher (P<0.05) in the pasture
grazed by prairie dogs and cattle than the pasture grazed by prairie dogs and
goats. Uncontrolled continuous grazing by goats at a heavy stocking rate in a prairie
dog colony had a drastic impact on plant community structure and hydrology in
the vicinity of the goat pens in comparison to the site grazed by prairie dogs
and cattle. Thus, confinement of large herds of goats to the same pasture year-round
in prairie dog colonies must be avoided.