British Columbia Mine Reclamation Symposium

Effects of alsike clover/Rhizobium symbiosis on lodgepole pine seedlings and soil nitrogen in west central British Columbia Trowbridge, Rick L.; Holl, F. Brian

Abstract

Losses of site nitrogen have been reported in British Columbia following prescribed burning and mechanical blading treatments used for site preparation in reforestation. While these treatments often lead initially to improved tree seedling establishment and survival, amelioration of nitrogen losses may be necessary to sustain long-term site productivity. Inoculated Trifolium hybridum L. (alsike clover) was seeded at O, 10, 20, and 30 kg/ha with Pinus contorta Doug, ex Loud (lodgepole pine) seedlings to determine 1) the effects of site preparation on infection and effectiveness of the clover-Rhizobium symbiosis and clover cover, and 2) the effects of the clover-Rhizobium symbiosis on survival, early growth, and foliar nitrogen concentration of the lodgepole pine seedlings and on soil nitrogen content and availability. The nitrogen-fixing symbiosis successfully established in all treatments, and site preparation (broadcast burn, windrow burn, and mechanical forest floor removal) had no significant effect on clover percent cover. After four growing seasons, the symbiosis had no effect on survival or height and diameter incremental growth of the seedlings. However, both needle mass and foliar nitrogen concentrations were significantly greater in clover-seeded plots compared to controls. There were significant increases in forest floor total and rnineralizable nitrogen as rate of seeding increased, although a similar effect was not detected for the mineral soil layer.

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