Rotational Grazing on Rangelands: Reconciliation of Perception and Experimental Evidence
AuthorBriske, D. D.
Derner, J. D.
Brown, J. R.
Fuhlendorf, S. D.
Teague, W. R.
Havstad, K. M.
Gillen, R. L.
Ash, A. J.
Willms, W. D.
MetadataShow full item record
CitationBriske, D. D., Derner, J. D., Brown, J. R., Fuhlendorf, S. D., Teague, W. R., Havstad, K. M., ... & Willms, W. D. (2008). Rotational grazing on rangelands: reconciliation of perception and experimental evidence. Rangeland Ecology & Management, 61(1), 3-17.
PublisherSociety for Range Management
JournalRangeland Ecology & Management
AbstractIn spite of overwhelming experimental evidence to the contrary, rotational grazing continues to be promoted and implemented as the only viable grazing strategy. The goals of this synthesis are to 1) reevaluate the complexity, underlying assumptions, and ecological processes of grazed ecosystems, 2) summarize plant and animal production responses to rotational and continuous grazing, 3) characterize the prevailing perceptions influencing the assessment of rotational and continuous grazing, and 4) attempt to direct the profession toward a reconciliation of perceptions advocating support for rotational grazing systems with that of the experimental evidence. The ecological relationships of grazing systems have been reasonably well resolved, at the scales investigated, and a continuation of costly grazing experiments adhering to conventional research protocols will yield little additional information. Plant production was equal or greater in continuous compared to rotational grazing in 87% (20 of 23) of the experiments. Similarly, animal production per head and per area were equal or greater in continuous compared to rotational grazing in 92% (35 of 38) and 84% (27 of 32) of the experiments, respectively. These experimental data demonstrate that a set of potentially effective grazing strategies exist, none of which have unique properties that set one apart from the other in terms of ecological effectiveness. The performance of rangeland grazing strategies are similarly constrained by several ecological variables establishing that differences among them are dependent on the effectiveness of management models, rather than the occurrence of unique ecological phenomena. Continued advocacy for rotational grazing as a superior strategy of grazing on rangelands is founded on perception and anecdotal interpretations, rather than an objective assessment of the vast experimental evidence. We recommend that these evidence-based conclusions be explicitly incorporated into management and policy decisions addressing this predominant land use on rangelands.
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Paddock Size and Stocking Density Affect Spatial Heterogeneity of GrazingBarnes, Matthew K.; Norton, Brien E.; Maeno, Motoko; Malechek, John C. (Society for Range Management, 2008-07-01)The claim that intensive rotational grazing (IRG) can sustain higher stocking rates can be partially explained by more even spatial distribution of grazing such that livestock consume forage from a greater proportion of a pasture. To test the hypothesis that utilization is more even at the higher stocking densities of smaller paddocks, mean absolute deviation (heterogeneity) of utilization estimates by plot was compared in paddocks of sizes and stocking densities representing increasing subdivision from two-paddock deferred rotation grazing (DRG) to 16-, 32-, and 64-paddock, two-cycle IRG. These 70-, 4-, 2-, and 1-ha paddocks were grazed for 7 wk, 4 d, 2 d, and 1 d, respectively, at 32 animal unit days (AUD) ha-1 during 2000 and 34 AUD ha-1 during 2001. Within IRG there was no response to the treatment gradient. After one cycle in the IRG paddocks, heterogeneity of use was generally lower than in the DRG paddocks, in both 2000 (3-11% [outlier 18%] vs. 14-19%) and 2001 (9-17% vs. 24-28%). After a second cycle in 2001, heterogeneity in half of the IRG paddocks (17-21%) was nearly as high as the early-grazed (24%), but not the late-grazed (28%), of the DRG paddocks. This lack of a stronger difference between systems was probably due to the fixed two-cycle IRG schedule and lack of plant growth during the nongrazing interval. Across both systems heterogeneity of utilization was strongly positively correlated with paddock size. Because utilization was not severely patchy in the largest treatment, the difference between systems would likely be greater in commercial-scale paddocks. Thus grazing distribution can be more even under intensive than extensive management, but this depends on how adaptively the system, particularly the aspects of timing and frequency, is managed.
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