Soil compaction of forest plantations in interior British Columbia

Grazing cattle on forest plantations in the interior of British Columbia (B .C.) is a common practice, but its impact on soil compaction is not well do cumented. This study evaluated the effects of cattle grazing and forage see ding on soil compaction in lodgepole pine (Pinus contorta Dougl. ex Loud. v ar. latifolia Engelm.) plantations near Kamloops, B.C. Grazing regimes cons isted of ungrazed exclosures and pastures grazed to achieve 50% utilization of forage vegetation. Seeding treatments were 0 and 12 kg ha(-1). Soil bul k density and penetration resistance were determined in 1996 and 1997, befo re and after the one-month grazing period on study sites grazed since 1989. Water infiltration rates were measured in 1997 after the one-month cattle grazing period. Bulk density was 6% higher on grazed pastures compared to t he exclosures. Pastures seeded to domestic forage species had significantly greater soil bulk density at the 0-7.5 cm depth than unseeded pastures. So il penetration resistance was higher throughout most of the soil profile in the grazed treatments than in the ungrazed exclosures. On pastures without grazing, seeding of the domestic forage species resulted in lower soil pen etration resistance relative to unseeded pastures. This was especially true at depths below 6 cm. The rate of water infiltration was not affected by l ong-term grazing and forage seeding. The bulk density and penetration resis tance data indicate that plantation grazing at 50% forage utilization does not lead to root-limiting increases in soil compaction.