Differing effects of cattle grazing on native and alien plants
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Authors: S. Kimball, and P. M. Schiffman
Date: 2003
Journal: Conservation Biology
Volume: 17
Number: 6
Pages: 1681-1693
Summary of Methods: Effects of herbivory on grazed and ungrazed alien and native species in the California annual grasslands was evaluated using greenhouse and field trials. This study was conducted on the Carrizo Plain National Monument that includes the largest California grassland remnant. Due to the discovery of two endangered forbs a portion of the study site was excluded from grazing ten years prior to this study. In the grazing exclosure, five treatments: control, clipped once (late Feb), clipped twice (late Feb, and early March), clipped three times (late Feb, early March, and early April), mulch removal (late Feb removal of only dead plant material). Plants were clipped to 1 cm above ground level and over three years. Following the first clipping treatment a subplot were used to estimate cover for each species within the plot. Density and cover of both alien and native species were measured over three years. In the greenhouse study, an alien and native grass and forb species were germinated with one plant per pot. Three clipping treatments (no clipping, clipping at 1 month, clipping at 1 and 2 months following planting) were applied to each species. Flowers and fruit were counted 1 month after the last treatment was applied, and total production was also determined. Effect of competition elimination was also evaluated by weeding around individual plants within the exclosure.
Article Summary / Main Points: Native species declined in cover after a single year of clipping in the field trials. Field plots showed that growth and reproduction was reduced on the perennial bunchgrass Poa secunda with only one year of clipping. Alien species Erodium cicutarium, was negatively affected by clipping in the field, but in the greenhouse this plant overcompensated in productivity. The presence of cattle grazing, regardless of season of use or intensity can negatively affect native species in this particular ecosystem.
Vegetation Types: California Grasslands (including all annual grasslands) Oak Woodlands
MLRA Ecoregions: 14 Central California Coastal Valleys 15 Central California Coast Range
Agrovoc Control Words: Weeds Rangelands Grazing
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: erodium cicutarium, invasive alien plants, native plant diversity, overcompensation, plant cover, plant density
Annotation: This study is applicable but is limited in applicability to California grasslands that did not evolve under grazing pressure unlike other grass and shrubland communities.
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