SPRAY-01-005

Effects of Livestock Grazing, Wildlife Browsing, and Forest Harvesting on Lodgepole Pine Regeneration
Sponsor: 
Spray Lakes Sawmills 1980 Ltd.
Lead Researcher: 
Ed Korpela, Ph.D., Alberta Research Council, Vegreville, Alberta
Body: 
This study investigates the effects of livestock grazing, wildlife browsing and forest harvesting on lodgepole pine regeneration. Results from this study may be referenced and used to improve reforestation success and facilitate discussion between the forest industry and ranchers.

The study took place between 1996 and 2000 in the Foothills south and west of Sundre, Alberta. The study evaluated the effects of slash disposal techniques, competing vegetation, wildlife and livestock browsing and grazing upon lodgepole pine regeneration and forage production.

The study confirmed that livestock does browse and trample seedlings, however it was found that wildlife browsing may exceed the impacts of cattle, as mortality was actually 10% higher in the enclosures that excluded cattle. Browsing was found to have negligible effects on height growth after five years. The data demonstrated that the greatest reduction in both survival and growth of the regenerating seedlings was in fact due to competition. Bracke scarification increased survival and growth of planted seedlings, however also increased the incidence of browsing. The presence of slash in the block increased the number of pine germinants. It also increased the incidence of browsing perhaps due to the lack of alternative forages resulting from the slash accumulation. The presence of slash also increased the amount of mechanical damage to the seedlings possibly from animals stepping on seedlings to avoid stepping on slash. The study suggested that winter desiccation and resultant top kill may reduce the ability of regenerating cutblocks to meet provincial reforestation standards. Harvested cutblocks can supply a significant amount of forage for both livestock and wildlife for a number of years following harvesting however, there was no clear relationship between cutblock age and forage production. This finding has significant implications to grazing management, and survival and growth of lodgepole pine regeneration.