A generalized model of the effects of grazing by large herbivores on grassland community structure
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Authors: D. G. Milchunas, O. E. Sala, and W. K. Lauenroth
Date: 1988
Journal: The American Naturalist
Volume: 132
Number: 1
Pages: 87-106
Summary of Methods: Current disturbance models (predation hypothesis, intermediate-disturbance hypothesis, and the Huston hypothesis) do not adequately account for the wide range of responses by grassland plants communities to grazing by large herbivores. This model looked at data from areas representing the four boundary cases of the moisture gradient and the evolutionary-history-of-grazing gradient. Feedback mechanisms are manifest in the rapid switching capabilities of subhumid grasslands with long evolutionary histories of grazing and divergent selection pressures. Switching capabilities do not exist in semiarid grasslands with long evolutionary histories of grazing and convergent selection pressures. Feedback mechanisms are not well developed in systems with short evolutionary histories of grazing. In these cases, the differences in response to grazing by semiarid and subhumid situations arise mainly from differences in the grazing tolerance of plants adapted to semiaridity or of plants adapted to competition for light and from the different effects of grazing on canopy structure.
Article Summary / Main Points: None
Vegetation Types:
MLRA Ecoregions:
Agrovoc Control Words: Riparian zones Rangelands Wildlife
Article Review Type: None
Article Type: None
Keywords: grazing, herbivory, grassland community structure, predation hypothesis, intermediate-disturbance hypothesis, huston hypothesis, grazing model, moisture, evolutionary history of grazing
Annotation: This model uses characteristics of grasslands ranging from Colorado and Washington to Africa and South America. This summary only includes information regarding North America. Season of use is not specified.
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