Carrizo Plain National Monument

Kimball, S. and P.M. Schiffman. 2003. Differing effects of cattle grazing on native and alien plants. Conservation Biology 17: 1681-1693.
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Collaborator: Paula Schiffman

Links to Additional Research Topics:

Traits influencing plant community composition

Penstemon hybrid zone: pollination, physiology, and fitness

Pollinators

Physiology

Reproductive Isolation

Local ecology and geographic range limits

Cattle grazing is a management practice used for reducing the cover of alien plants in California grasslands and elsewhere in the western United States. This study tested the effectiveness of grazing as a restoration method by examining the effects of simulated herbivory on native and alien plants.

Plots at Carrizo Plain National Monument were established in which plants were clipped or mulch (dead biomass) was removed. Species from the field were also grown in pots and clipped, and individuals in the field were marked and clipped with and without competitiors.

Native plants were negatively affected by clipping in 1999, 2000, and 2001 while alien species were unaffected.

The California grassland community assembled in the absence of grazing herds, while invasive European species have been exposed to grazing for centuries. It may be that the European invaders have adaptations that better enable them to recover from grazing. In the plot experiment, the European forb Erodium cicutarium was able to compensate in growth and reproduction following herbivory. In contrast, the native perennial bunchgrass Poa secunda was significantly impacted by simulated grazing and experienced a negative effect on reproduction and height one year following herbivory. In pots, Erodium cicutarium overcompensated and grasses undercompensated. European grasses were not affected by the removal of competitors.

It is unclear by what mechanism E. cicutarium was able to compensate, but the ability may be related to its basal rosette growth form and indeterminately growing inflorescences. The current strategy of grazing for grassland restoration actually harms native plants and promotes aliens.

One of the clipped study plots
surrounded by native Lasthenia
californica.

Cattle grazing within the national
monument.