Effect of Rancher’s Management Philosophy, Grazing Practices, and Personal Characteristics on Sustainability Indices for North Central Texas Rangeland Page: 17
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defoliation removing 50% or more of the shoot volume retarded root growth in 7 of 8 perennial
species examined. This observation, among others, prompted the often used term, "take half -
leave half," as a saying for grazing management that emphasizes stocking rate. However,
Hormay (1956) observed that preferred plants in preferred sites are utilized closely and
repeatedly even when the entire management unit is lightly or moderately stocked on average.
Other study results refute the notion that grassland herbivory leads to a reduction in root
productivity, and a decline in soil carbon content. Frank et al. (2002) insists that grazers
stimulated aboveground, belowground and whole-grassland productivity. They found the major
effect of herbivory was a positive feedback on root growth. It is reported that grazers are
important regulators of carbon and nitrogen ecosystem processes (Frank and Groffman, 1998).
Grazers can increase forage nutrient concentrations and aboveground plant production (Frank
and McNaughton, 2002). Grazers also enhance mineral availability for soil microbial and
rhizospheric processes that ultimately feedback positively to plant nutrition and photosynthesis
(Hamilton and Frank, 2001), in addition to increasing nutrient cycling within patches of their
urine and excrement (Holland et al., 1992). However, the positive feedbacks from grazers on the
ecosystem are contingent on suitable climatic conditions. During drought, these feedbacks are
diminished (Wallace et al., 1984; Coughenour et al., 1985; Louda, 1990).
A plant can produce leaves only at an intact growing point. The lower that point is to the
ground, the more grazing tolerant the plant. Destruction of that point will prevent the production
of seeds and new seedlings. Thus grasses need to be rested periodically to allow for production
of leaf material to feed the plant and produce seeds (Hanselka et al., 2009).
Livestock prefer to consume certain plants compared to others. In the context of
rangeland evolution and ungulate migration, these preferred plants have probably always been
severely grazed when encountered. It is suggested that the intermittent nature of the severe
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Becker, Wayne. Effect of Rancher’s Management Philosophy, Grazing Practices, and Personal Characteristics on Sustainability Indices for North Central Texas Rangeland, dissertation, December 2011; Denton, Texas. (digital.library.unt.edu/ark:/67531/metadc103289/m1/28/: accessed February 27, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .