Our results also indicate that rotational grazing, if properly implemented, has the potential to provide better for adequate fine fuel and to enhance range condition through provision of periodic deferment from grazing and regulation of grazing pressure after burning. The periodic deferment in the 2 rotationally-grazed treatments allowed the more heavily grazed areas in these treatments to recover between periods of occupation to decrease bare ground and improve range health. Relative to the continuously-grazed control, the 8-paddock rotations had a much lower percentage of bare ground, and the 4-paddock treatments were intermediate. The percentage of bare ground is an important indicator of rangeland health, and these results emphasize the importance of periodic deferment from grazing and regulation of grazing pressure afforded with rotational grazing, as indicated in other research. Recovery rest during the growing season after grazing has been shown to be very important for range condition improvement and maintenance (Teague et al. 2004), and was probably the major reason for the lower levels of bare ground on the rotationally grazed treatment areas. Rotational grazing resulted in less bare ground and no reductions in herbaceous biomass or decrease in desirable plant species relative to the continuously grazed control.

When summer growing conditions were favorable, the rotational grazing treatment resulted in greater increases of perennial herbaceous basal areas (p < 0.05) and lower proportions of bare ground (p<0.10) than the continuously grazed treatment. Although rotational grazing did not prevent deterioration in basal area and bare ground with the series of four drought years, it did decrease the rate of deterioration. The changes in basal area were primarily due to changes in summer growing perennial C4 midgrasses and C4 shortgrasses. Grazing treatment did not influence species aerial biomass composition (p > 0.1). When monitoring to effect sustainable use, the commonly used parameter of species composition appears to be a much less sensitive indicator of change than bare ground and basal area.

Figure 4. Herbaceous basal area (%) on degraded patches on clay-loam sites under continuous grazing (Rectangle ) and an 8-pasture rotational grazing treatment (Shaded rectangle ). Bars represent ± 1 SE.

To sustain the range resource, it is of paramount importance that management practices minimize bare ground, increase herbaceous perennial basal area, and decrease the area of patches dominated by low successional species. The process of patch selective grazing induces a micro-pattern of heavily grazed areas and lightly grazed or ungrazed areas. The heavily grazed areas are overgrazed even when the stocking rate for the grazing unit as a whole is within the carrying capacity.

This study indicates that in large paddocks, rotational grazing can reduce degradation caused by patch overgrazing. To prevent the deterioration of heavily grazed patches, adequate lengths of time between successive defoliations must be provided. Planned rotational grazing is the tool that provides managers with the opportunity to address the root cause of patch overgrazing and deterioration. It is, therefore, a key tool in managing for sustainable use of rangeland.

References

Teague, W.R. and S.L. Dowhower. 2003. Patch dynamics under rotational and continuous grazing management in large, heterogeneous paddocks. Journal of Arid Environments 53:211-229.

Teague, W.R. S.L. Dowhower and J.A. Waggoner. 2004. Drought and grazing patch dynamics under different grazing management. Journal of Arid Environments 58:97-117.