Cattle grazing effects on plant species composition and soil compaction on rehabilitated forest landings in central interior British Columbia

摘要

Soils on forest landings (areas of cutblocks where harvested trees are processed and loaded onto trucks) are often degraded and unable to support optimal growth of planted conifers unless rehabilitation practices are applied. In British Columbia (BC), cattle often graze forage on forest landings. This study evaluated the effects of cattle grazing on native and non-native plant species composition, soil compaction, and tree growth on rehabilitated forest landings in the central interior of BC. Three study sites (landings) were rehabilitated by tillage in 1998, planted with lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) in 1999, and sampled during May-September 2003. Grazing regimes consisted of ungrazed exclosures and landings grazed to achieve 50 percent utilization of forages. Abundance of native species and non-native weeds was not affected by grazing, while alsike clover (Trifolium hybridum L.) was the only non-native forage species reduced by grazing. With greater mechanical resistance and less stable aggregates, the soil on the grazed landings was less favorable to plant growth. Canopy cover of lodgepole pine, tree height, diameter, and leader growth were all reduced on areas of the landing used by cattle. Trampling damaged 75 percent of trees, but 70 percent of planted lodgepole pine survived. Cattle grazing on rehabilitated landings may be feasible but managers should recognize the potential for cattle damage to regenerating tree seedlings and incorporate plans to prevent or mitigate such damage.