Instability of development and fractal architecture in dryland plants as an index of grazing pressure
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Authors: C. L. Alados, J. M. Emlen, B. Wachocki, and D. C. Freeman
Date: 1998
Journal: Journal of Arid Environments
Volume: 38
Number: 1
Pages: 63-76
Summary of Methods: Stress from grazing can influence the development of plants and this study uses statistical developmental instability analyses to relate growth characteristics of plants to stress levels caused by sheep and other ungulate grazing. In some plant species (C. greenii, O. hymenoides) that are not grazed by sheep during winter, analyses of plants exposed to heavy grazing pressure showed that stress decreased in comparison to other treatments, due to less competition from neighboring plants that were grazed during the winter time. Seriphidium novum, a plant that is preferred by sheep, increases the distance between its leaves as a response to stress, which the analyses indicated is frequent when exposed to grazing. In general, developmental instability analyses found that grazing releases ungrazed plants from competition, which reduced stress as expected, and that growth forms can change when plants are exposed to stress.
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: developmental instability, chrysothamnus greenii, oryzopsis hymenoides, seriphidium novum, grazing impact, allometric relationships
Annotation: Plants were exposed to three levels of grazing intensity: Light - 25 sheep days / ha; Medium - 35 sheep days / ha; Heavy - 42 sheep days / ha. This study mainly looked at sheep grazing, but there was a control area that is naturally grazed by pronghorns, jackrabbits, and cottontail rabbits (the most important herbivore species inhabiting the Desert Experimental Range in Utah) that were examined.
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