Alpine grazing: does it reduce blazing?

Williams R.J., Ashton D.H. (1987) Effects of disturbance and grazing by cattle on the dynamics of heathland and grassland communities on the Bogong High Plains, Victoria. Australian Journal of Botany 35, 413–431.

Aim: 
To examine the factors affecting the establishment of shrubs within both heathland and grassland communities, and to assess the role which grazing by domestic livestock may have in this process (pp. 413).
Type of Study: 
Manipulative experiment
Key Results: 
The establishment of shrub seedlings (of several species) occurs primarily upon bare ground, and is absent where the cover of vegetation or fixed Poa hiemata litter remains intact. The survival of Poa hiemata seedlings on bare ground is low, except where local shelter is afforded. Disturbances which cause bare ground, including domestic cattle activity, can create microsites suitable for the establishment of shrub seedlings. Shrub establishment and development may be inhibited by cattle trampling, and some palatable shrubs... are especially affected (pp. 413).
Treatments: 
Plots established in two community types (open heathland or closed heathland) in grazed and ungrazed areas, initially dominated by either snowgrass and shrub vegetation. Three intensity treatments applied to plots (total removal of vegetation, partial removal of vegetation and undisturbed). Plots assessed over 3 consecutive years.
Response: 
If cattle are removed from previously grazed grassland and heathland sites where shrubs such as Asterolasia and Grevillea have established, the encroachment of such shrubs will be more rapid than on similar sites subject to continued grazing. However, continued cattle activity is unlikely to inhibit the development of non-palatable, vegetatively reproducing shrubs such as Prostanthera cuneata and Phebalium squamulosum within closed heath communities (pp. 413). Continued grazing will also increase the abundance of bare ground patches, which are necessary for the establishment of shrub seedlings.
Models: 
Frequentist (P values): ANOVA.
Comments: 
Unequivocal experimental demonstration of the need for bare ground for the establishment of shrub seedlings.
Reviewer: 
Imogen Fraser; Dick Williams
Locations: 
Bogong High Plains, Australian Alpine National Park, Victoria, Australia
Response variable : 
Shrub seedling density, overlapping vegetation cover.
Replication: 
Each treatment combination replicated 5 times. 120 (1m2) quadrats in total.
Ecosystem: 
Open heathland and closed heathland.
Survey: 
0.5–4 ha study areas, 2 study areas (Cope creek and Rocky Valley).
Full Reference: 
Williams R.J., Ashton D.H. (1987) Effects of disturbance and grazing by cattle on the dynamics of heathland and grassland communities on the Bogong High Plains, Victoria. Australian Journal of Botany 35, 413–431.