Vegetation on grazed and ungrazed pinyon-juniper grassland in New Mexico

  • Published source details Pieper R.D. (1968) Vegetation on grazed and ungrazed pinyon-juniper grassland in New Mexico. Journal of Range Management, 21, 51-53.


A study was undertaken at Fort Stanton Cooperative Range Research Station, New Mexico (southwest USA), to compare vegetation of pinyon-juniper (Pinus-Juniperus) grassland on cattle-grazed areas with that on comparable areas protected from livestock grazing for 12 years.

The area was grazed by livestock at varying intensities from 1900 to 1952. Three study sites (open Pinus-Juniperus woodland with a grass-dominated understorey) were selected: a loamy bottomland, a loamy upland and a stony hills site. Main grasses were blue grama Bouteloua gracilis, sideoats grama B.curtipendula, galleta Hilaria jamesii, ring muhly Muhlenbergia torreyi and mat muhly M.richardsonis.
In 1964, plant cover by species (and litter, bare soil and rock) were determined on cattle-grazed and protected areas (livestock excluded for 12 years) at each site along a 100 ft (30.5 m) long transect. Herbage production (cages used to protect grassland from cattle in grazed areas) was determined by clipping randomly located (1 x 2 ft; 30 x 60 cm) plots at the end of the growing season (late September), drying and weighing.

Herbage production (lb dry weight/acre) was significantly higher on protected areas at all three sites (protected: stony - 560; loamy bottom - 610; loamy upland - 650 vs. grazed: stony - 470; loamy bottom - 295; loamy upland - 550). Height of blue grama (the main forage species) was also significantly higher on protected areas at all three sites.
Plant species composition was not significantly different between grazed and protected areas on the stony hills site.
Mat muhly composition was significantly higher on grazed areas on loamy bottom and loamy upland sites (protected: stony - 0%; loamy bottom - 0.7%; loamy upland - 1.0% vs. grazed: stony - 0.1%; loamy bottom - 48.2%; loamy upland - 25.1%).
Composition of blue grama (protected: stony - 88.2%; loamy bottom - 73.3%; loamy upland - 72.3% vs. grazed: stony - 90.7%; loamy bottom - 44.3%; loamy upland - 65.0%) and western wheatgrassAgropyron smithii (protected: stony - 0%; loamy bottom - 15.0%; loamy upland - 0.1% vs. grazed: stony - 0%; loamy bottom - 1.7%; loamy upland - 0.4%), was significantly lower on the grazed area on the loamy bottomland site.
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