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UBC Theses and Dissertations

The effect of forage seeding on vegetation dynamics and the early growth and survival of lodgepole pine (Pinus contorta var. latifolia Engelm.) on a forest clear-cut Powell, George Wilfred


Field trials of orchardgrass (Dactylis glomerata L.),smooth bromegrass (Bromus inermis Leys.), alsike clover (Trifolium hybridum L.), and a mixture by weight of 40%orchardgrass, 40% alsike clover, and 20% white clover (Trifolium repens L.), with five seeding rates by weight (0.5, 1.5, 3.0, 6.0 and 12.0 kg/ha), were conducted on a forest clear-cut in the Very Dry, Cool Montane Spruce biogeoclimatic subzone in the southern interior of British Columbia. The treatments were monitored for the first two growing seasons for their influence on the vegetation dynamics, and the resultant interactions of the vegetation on the growth and survival of planted 1+0 lodgepole pine (Pinus contorta var. latifolia Engelm.) seedlings. Forage seeding had no effect on lodgepole pine survival. There was no significant difference in the height, basal diameter or stem volume growth of lodgepole pine in 1990 among different species of forage or between domestic forages and native vegetation. In the second year of the study (1991), decreases in the increment in lodgepole pine basal diameter were weakly associated with increasing seeding rate; however, lodgepole pine height, and stem volume remained unaffected by species or seeding rate of forages. There was no difference in the effect of different forage species or native vegetation on lodgepole pine growth in 1991. Stem volumes were lower in 1990 and 1991 on conifers with surrounding vegetation compared to the control groups with competing vegetation removed. Unit needle mass decreased with the absence of vegetation in 1991. There was a positive correlation between cover of orchardgrass and overwinter rodent damage of the lodgepole pine seedlings following the first growing season; however, lodgepole pine survival was independent of rodent damage. Density, cover, and height of vegetation were positively correlated with pure live seeds sown per ha, although this effect was delayed to the second growing season for height, and cover. Two-dimensional partitioning of the cover indicated that the seeded fraction of the total vegetative response was influenced by seeding rate and species of forage sown in both growing seasons. The variability introduced by native vegetation masked the treatment effect in the first year, such that overall there was no treatment effect for total vegetative cover. Initial germination of forages was not linearly related to the initial cover of soil, litter or wood on the plots; however, development of the vegetation, in particular the clovers, was often correlated with the initial cover of these non-floristic cover components.

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