Soil compaction of forest plantations of interior British Columbia.

Abstract

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 documented. This study evaluated the effects of cattle grazing and forage seeding on soil compaction in lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) plantations near Kamloops, B.C. Grazing regimes consisted of ungrazed exclosures and pastures grazed to achieve 50% utilization of forage vegetation. Seeding treatments were 0 and 12 kg ha-1. Soil bulk density and penetration resistance were determined in 1996 and 1997, before 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 the exclosures. Pastures seeded to domestic forage species had significantly greater soil bulk density at the 0-7.5 cm depth than unseeded pastures. Soil 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 penetration resistance relative to unseeded pastures. This was especially true at depths below 6 cm. The rate of water infiltration was not affected by long-term grazing and forage seeding. The bulk density and penetration resistance data indicate that plantation grazing at 50% forage utilization does not lead to root-limiting increases in soil compaction.