Rotational Grazing on Rangelands: Reconciliation of Perception and Experimental Evidence

TLDR: In this article, the authors present a synthesis of rotational and continuous grazing on rangelands and conclude that rotational grazing is superior to continuous grazing in terms of ecological effectiveness.

About: This article is published in Rangeland Ecology & Management.The article was published on 2008-01-01 and is currently open access. It has received 591 citations till now. The article focuses on the topics: Conservation grazing & Rangeland management.

Figures

Figure 1. Number of published grazing experiments that reported significantly higher, equal, or lower plant and animal production responses for continuous compared to rotational grazing at (A) similar stocking rates, (B) higher stocking rates for rotational grazing, and (C) across stocking rates for all experiments. Animal production is presented as both a per head and per land area response. Citations and other relevant information for the experiments comprising these data are presented in Appendix I.

Figure 2. Illustration of the consequences of (A) low and (B) high stocking rate on energy partitioning (kg C˙ha 21 ˙ d 21) between plant production and forage utilization by livestock in grazed ecosystems. Leaf area index (LAI) and forage utilization are interrelated so that neither can be optimized independently; rather, both must be simultaneously optimized to sustain plant and animal production. This fundamental requirement to balance plant growth and forage consumption by livestock partially explains why grazing research has found stocking rate to affect plant and animal response variables to a greater extent than grazing system on rangelands (redrawn from Parsons et al. 1983).

Table 1. Characteristics of basic rotational grazing systems implemented on rangelands.

Figure 3. Depiction of how infrequent and unpredictable rainfall and corresponding periods of plant growth can minimize the benefits of rest on vegetation responses in rotational grazing systems. Rest periods that coincide with limited plant growth convey minimal benefit to plants so that the impacts of increased grazing pressure during short grazing periods may not be offset during subsequent rest periods. This represents the most plausible ecological explanation for why grazing research has found the redistribution of grazing pressure to be of minimal benefit to vegetation compared to continuous grazing on rangelands.

Table 2. Conclusions from major reviews of grazing systems research spanning the last 50 years of the rangeland profession. Experimental data have consistently indicated that rotational grazing is not superior to continuous grazing on rangelands.

Frequently asked questions

Q1. What are the contributions in "Rotational grazing on rangelands: reconciliation of perception and experimental evidence" ?

For example, Hart et al. this paper concluded that rotational grazing is not superior to continuous grazing on rangelands. 

Q2. What is the protocol for grazing experiments?

Research protocol requires that grazing experiments be structured in a manner that minimizes both ecological and managerial variability to effectively test hypotheses that enhance their understanding of critical ecological processes operating in grazed ecosystems. 

Q3. Why does intensive grazing reduce the energy of raindrop impact?

This occurs because the removal of large amounts of plant cover and biomass by intensive grazing reduces the potential to dissipate the energy of raindrop impact and overland flow. 

Q4. What is the important factor in the response of soil hydrological characteristics to grazing?

These hydrological responses to grazing are strongly contingent on community composition, with communities that provide greater cover and obstruction to overland flow such as midgrass-dominated communities having greater hydrological function, including infiltration rate, than short grass–dominated communities (Wood and Blackburn 1981; Thurow 1991). 

Q5. What are the objectives of this synthesis?

The specific objectives of this synthesis are to 1) reevaluate the complexity, underlying assumptions, and ecological processes governing the response 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. 

Q6. What is the main reason why rotational grazing is not supported by empirical evidence?

A fundamental ecological explanation for why the unifying principles of vegetation responses to grazing do not support greater effectiveness of rotational grazing is that grazing management must optimize several competing ecological processes to attain production goals sustainably. 

Q7. What is the primary misconception underlying continued advocacy for rotational grazing on rangelands?

An overestimation of the presumed benefits of rest from grazing, within the framework of rotational grazing systems (e.g., several weeks rest between brief and often intensive grazing periods), may represent the primary misconception underlying continued advocacy for rotational grazing on rangelands (e.g., Taylor et al. 

Q8. What is the critical interpretation of continuous grazing?

The critical interpretation of continuous grazing, prompted by excessive stocking rates that werecommon prior to the implementation of proper grazing management, may still be promulgated today. 

Q9. What percentage of the experiments reported no differences for plant production/standing crop?

Eighty-nine percent of the experiments (17 of 19) reported no differences for plant production/standing crop between rotational and continuous grazing with similar stocking rates (Fig. 1A). 

Q10. What are the main conservation goals of grazing systems?

Conservation goals often emerge at large scales, and even though the flexibility associated with rotational grazing systems can provide managers with opportunities to manipulate grazing frequency, intensity, and seasonality to pursue specific conservation goals (e.g., bird nesting success, periodic plant establishment or reproduction, fuel accumulation or suppression), there has not yet been a comprehensive accounting of the conservation effects associated with the large-scale adoption of grazing systems. 

Q11. What is the main argument for rotational grazing?

The experimental evidence indicates that rotational grazing is a viable grazing strategy on rangelands, but the perception that it is superior to continuous grazing is not supported by the vast majority of experimental investigations.