Variation in response to defoliation between populations of Bouteloua curtipendula var. caespitosa (Poaceae) with different livestock grazing histories
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Authors: S. E. Smith
Date: 1998
Journal: American Journal of Botany
Volume: 85
Number: 9
Pages: 1266-1272
Summary of Methods: Sideoats grama (Bouteloua curtipendula var. caespitosa) plants, grown from plant communities with similar composition that did or did not have a long history of cattle grazing, were defoliated every 14, 28, or 56 days to determine whether previous exposure to grazing affected plant response to herbivory. Plants grown from populations that had been previously exposed to grazing had lower mortality than plants grown from ungrazed populations, indicating that grazing history influenced plant herbivory tolerance. Plant height and leaf growth angle were not as responsive to clipping treatments in plants that were grown from previously grazed populations, indicating that resistance mechanisms were present in the previously grazed plants before clipping treatments were applied. These results suggest that plant populations can develop grazing tolerance and resistance mechanisms when exposed to a long history of grazing, however, the author cautions that plants populations with these specific mechanisms may have lower genetic variability and will be less adaptive to other disturbances than plant populations without them.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: defoliation resistance, genetic variation, phenotypic plasticity, sideoats grama, bouteloua, simulated herbivory
Annotation: Ramets were clipped 5 cm above the soil surface (removing all leaf blades) every 6 weeks during the 13.5 month acclimatization period. This clipping height, which represents ~70% removal of aboveground biomass, was used because it corresponds to the average defoliation observed on grazed plants on the cattle-impacted site when plants were dug. 14 days after the final clipping of the acclimatization period, 3 defoliation treatments were imposed on the 15 genets from each population using a split-plot arrangement with 4 replications. Defoliation treatment (every 14, 28, or 56 days) was the main plot factor and population was the sub plot factor. Season of use is not specified.
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