Effect of forage seeding on early growth and survival of lodgepole pine

Abstract

Smooth bromegrass (Bromus inermis Leys.), orchardgrass (Dactylis glomerata L.), alsike clover (Trifolium hybridum L.), and a mixture by mass of 40% orchardgrass, 40% alsike clover, and 20% white clover (Trifolium repens L.), were sown at 0.5, 1.5, 3.0, 6.0, and 12.0 kg/ha on a forest clear-cut in the southern interior of British Columbia. The seeding treatments were monitored for 3 growing seasons following planting to determine their influence on the growth, survival and damage of planted one-year old lodgepole pine (Pinus contorta var. latifolia Engelm.) seedlings. Competing vegetation reduced lodgepole pine diameter by up to 38% (P < 0.004) and heights by up to 30% (P < 0.005). Lodgepole pine basal diameters (P < 0.002), height (P < 0.02) and survival (P < 0.03) decreased linearly with increasing forage seeding rate. Lodgepole pines planted with smooth bromegrass had up to 59% larger (P < 0.01) diameters and were up to 33% taller (P < 0.06) than those planted with orchardgrass at equal seeding rates by mass. Lodgepole pine cumulative mortality was 2 to 5 times greater (P < 0.0001) on plots sown to alsike clover compared to plots sown with smooth bromegrass or orchardgrass. Rodent damage peaked between the first and second growing seasons at 24% of the lodgepole pine seedlings; rodent damage was similar (P > 0.05) among the treatments and controls, and conifer survival was independent (P > 0.05) of rodent damage.