Assessment of a Grazing Pressure Index to Determine Optimal Grazing Management on Clearcuts Planted to Lodgepole Pine in the Southern Interior of British Columbia

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Grazing pressure (Animal Unit kg^-1 of available forage) describes the ratio of animal demand per unit mass of forage at any instant in time (Scamecchia 1985). It has been shown that grazing time of heifers increases dramatically as forage availability declines. Increased grazing time also implies that animals spend more time walking through the pasture searching for forage. Regenerating lodgepole pine seedlings may therefore suffer increased trampling damage as forage supply diminishes.

Compared to stocking rate, grazing pressure may provide a more useful prediction or measure of the potential impacts of cattle grazing on tree seedling damage.

The primary research objectives were to (1) determine the grazing pressure threshold that results in physical damage to regenerating lodgepole pine seedlings, and, (2) determine the relationships among percent forage utilization, forage availability, stocking rates, stocking density, and grazing pressure in order to provide an efficient, reliable method by which resource managers can prescribe grazing management programs that enhance lodgepole pine survival and growth.