Structure, biomass production and dynamics of four white spruce (Picea glauca [Moench] Voss) plantations near Thunder Bay, Ontario / by William Donald Towill

Stand structure, biomass production and dynamics of
\nwhite spruce (Picea glauca (Moench) Voss) were investigated
\nin four plantations, ages 4, 10, 18, and 28 years,
\nrespectively, on similar lacustrine soils. Dry matter
\npartitioning of the white spruce component at the individual
\ntree and stand levels and under varying densities of
\ntrembling aspen (Populus tremuloides Michx.) was analyzed.
\nA general pattern of stand development tied to: (1)
\nthe timing and severity of site preparation preceding
\nplantation establishment; (2) the nature and distribution
\nof the post-cut vegetation; (3) soil and site conditions;
\nand (4) the successional processes in the tree strata, was
\nproposed which may also be applicable to plantations other
\nthan those in the study.
\nMajor differences in stand structure, biomass
\npartitioning and distribution, within the white spruce
\npopulations of each plantation existed. This variation was
\nattributed to differences in micro-site condition and the
\ndensity of trembling aspen and other herbaceous vegetation
\nsurrounding the planted white spruce. Severe scarification
\nusing a modified V-plough prior to establishment of the two
\nyoungest plantations resulted in highly variable early
\nheight and diameter growth and survival of the planted white
\nspruce.
\nBoth planted white spruce and second-growth aspen
\nproduced maximum height growth and biomass on micro-sites
\nwith deep surface horizons (Ah) where mixing of organic
\nmatter with the surface mineral soil has occurred. The
\npresence of trembling aspen, graminoids, wild raspberry
\n(Rubus idaeus L.), prickly rose fRosa acicularis Lindl.),
\nand other woody tall shrubs during the stand initiation and
\nthe stem exclusion stage were correlated with the decreased
\nheight and diameter growth of the surviving planted white
\nspruce. 
\nTotal standing crop for all species and the white
\nspruce component of the plantations each increased with
\nplantation age; partitioning of biomass to stemwood and
\nfoliage on individual spruce trees was significantly reduced
\nunder high aspen densities and where the standing crop
\nbiomass of graminoids, herbaceous plants and woody shrubs
\nwas greatest.
\nSpruce foliage efficiencies for wood production
\ngenerally increased with stand age, decreasing aspen density
\nand increasing dominance (crown class). A clearly defined
\nand fully integrated biological model relating foliage
\nefficiency of the individual white spruce growing in
\nassociation with trembling aspen could not be developed.
\nHowever, white spruce foliage, stemwood and total tree dry
\nweights were explained in multiple regression models which
\nincorporated the biomass of competing species, soil/site
\ncharacteristics, and a measure of the percent cover of the
\nspruce seedling by competing vegetation.

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