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  • 1
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    Root-system morphology of common boreal forest trees in Alberta, Canada (1983)
    Canadian Science Publishing
    Details
    Publication Date: 1983-12-01
    Description: Twenty-four specimens of six boreal tree species were excavated: eight Pinusbanksiana Lamb., five Populustremuloides Michx., four Piceaglauca (Moench) Voss, three Piceamariana (Mill.) B.S.P., two Abiesbalsamea (L.) Mills., and two Lara laricina (Du Roi) K. Koch. Root systems were described, and percent biomass determined for above- and below-ground components for half these specimens. Tree ages ranged from 3 to 120 years. Horizontally spreading lateral roots dominated the root systems of all species and occurred within 3– 15 cm of the ground surface. Nutrient and moisture absorption appear to be the principal functions of lateral roots. Maximum vertical root growth occurred near the tree stump as: tap-, heart, sinker, and oblique lateral roots. Vertical root morphology is influenced by site conditions. In addition to providing mechanical support, sinker and taproots may be important adaptations for deep-water utilization on xeric sites. Our data suggest that roots may be important in boreal succession processes through two related mechanisms: (i) nutrient and water deprivation occurring through preemptive growth of tree roots from climax species over roots of serai species, and through interception by mosses; and (ii) niche partitioning occurring below ground between serai and climax, and among climax tree species, by vertical separation of the root systems.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 2
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    Rooting depths and successional development of selected boreal forest communities (1983)
    Canadian Science Publishing
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    Publication Date: 1983-08-01
    Description: The root density and depth patterns of four boreal forest age sequences were analyzed for successional trends. Rooting depths increased with age on sandy substrates which supported aspen (Populustremuloides Michx.) and jack pine (Pinusbanksiana Lamb.) communities. Rooting depth did not change in an aspen series on fine-textured substrates or in a black spruce (Piceamariana (Mill.) BSP) series growing on organic substrates. Plant communities growing on mineral soils showed a decrease in near-surface root densities and understory vascular plant cover with increasing age. Maximum rooting was deepest on sandy substrates and shallowest on organic deposits. Roots in all stands were concentrated near the ground surface. In most cases 50% of all roots were located within 15 cm of the forest floor. Root densities in this zone ranged from 11 000 to 30 000 roots m−2 of vertical surface. Densities were approximately 4300 roots m−2 for the overall rooting zone.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 3
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    Genes, Vol. 2, Pages 608-626: Protein Folding Absent Selection (2012)
    Molecular Diversity Preservation International (MDPI)
    In: Genes
    Details
    Publication Date: 2012-06-12
    Description: Biological proteins are known to fold into specific 3D conformations. However, the fundamental question has remained: Do they fold because they are biological, and evolution has selected sequences which fold? Or is folding a common trait, widespread throughout sequence space? To address this question arbitrary, unevolved, random-sequence proteins were examined for structural features found in folded, biological proteins. Libraries of long (71 residue), random-sequence polypeptides, with ensemble amino acid composition near the mean for natural globular proteins, were expressed as cleavable fusions with ubiquitin. The structural properties of both the purified pools and individual isolates were then probed using circular dichroism, fluorescence emission, and fluorescence quenching techniques. Despite this necessarily sparse “sampling” of sequence space, structural properties that define globular biological proteins, namely collapsed conformations, secondary structure, and cooperative unfolding, were found to be prevalent among unevolved sequences. Thus, for polypeptides the size of small proteins, natural selection is not necessary to account for the compact and cooperative folded states observed in nature.
    Electronic ISSN: 2073-4425
    Topics: Biology
    Published by Molecular Diversity Preservation International (MDPI)
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  • 4
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    USE OF SOIL HORIZONS AS ECOLOGICAL SAMPLING UNITS (1988)
    Canadian Science Publishing
    Details
    Publication Date: 1988-02-01
    Description: Extractable nutrients and physical properties of Eutric Brunisols from pine and aspen stands were evaluated for their relationship to soil horizons classified according to morphological criteria. The results indicate strong horizon-nutrient associations, suggesting that soil horizons are appropriate sampling units for ecological studies concerned with below-ground nutrient and edaphic conditions. Key words: Nutrients, principal components analysis, soil horizon
    Print ISSN: 0008-4271
    Electronic ISSN: 1918-1841
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 5
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    A comparison of mature with recently clear-cut and scarified lodgepole pine forests in the Lower Foothills of Alberta (1976)
    Canadian Science Publishing
    Details
    Publication Date: 1976-03-01
    Description: Mature, even-aged lodgepole pine (Pinuscontorta Dougl. var latifolia Engelm.) forests on upland sites with Orthic Gray Luvisols in the Lower Foothills of Alberta have been clear-cut for pulpwood and scarified by bulldozer since 1958. Undisturbed stands had weak shrub strata, well developed herb – dwarf shrub strata, and continuous feather moss strata.In 25 clear-cut stands 6–12 years old, the average cover of vascular plants was 54% and did not change significantly during the sampled age interval. Cover of tree 'regeneration' (immature size classes) was 5%, increasing slowly, and codominated by lodgepole pine and aspen (Populustremuloides Michx.). Shrub cover was also 5% and dominated by prickly rose (Rosaacicularis Lindl.). Herb – dwarf shrub cover was 44% and dominated by nine species of the mature forest. Bryoid cover was 13 %.The density of young trees stabilized within 6 years after clear-cutting, and the above-ground biomass of both pine and aspen increased rapidly during the sampled age interval.An ordination of the clear-cut stands showed that the distribution and abundance of several important plant species were well correlated with soil moisture on two gravimetric sampling dates in summer.A comparison of dominance–diversity curves and indices for mature and clear-cut stands revealed that the clear-cut community was richer in vascular species (100 cf. 57) and had a more even distribution of cover among species.The early stages of secondary succession after clear-cutting and scarification of lodgepole pine forest are discussed.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 6
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    A strategy for concurrently monitoring the plant water potentials of spatially separated forest ecosystems (1986)
    Canadian Science Publishing
    Details
    Publication Date: 1986-04-01
    Description: A technique for estimating plant water potentials in plant communities was used in six forest stands representing a jack pine (Pinusbanksiana Lamb.) and a black spruce (Piceamariana (Mill.) B.S.P.) successional sequence. A set of 31 plants composed of 16 species were measured at 4-day intervals from early May to late August 1982. The six stands had similar patterns of summer plant water potentials with greatest differentiation among species occurring during periods of maximum water stress. Plant water potentials varied more in jack pine stands on sand than in black spruce stands on organic soil. Shallow-rooted ericaceous and (or) evergreen species (e.g., Vacciniummyrtilloides Michx., Vacciniumvitis-idaea L., and Pyrolaasarifolia Michx.) had the widest range of water potentials during summer, whereas deep-rooted Alnuscrispa (Ait.) Pursh had the narrowest range. Maximum morning (0700) water potentials reached−3.1 MPa. All species had fine roots (
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 7
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    Forest understory plants as predictors of lodgepole pine and white spruce site quality in west-central Alberta (1991)
    Canadian Science Publishing
    Details
    Publication Date: 1991-11-01
    Description: The feasibility was explored of using cover estimates of a few understory species with high indicator value, rather than total species lists, to evaluate site quality for lodgepole pine (Pinuscontorta Loudon var. latifolia Engelm.) and white spruce (Piceaglauca (Moench) Voss). Analysis of 112 vascular and 7 nonvascular understory plant species from 211 lodgepole pine and white spruce dominated forests revealed that 39 and 30 of these species had significantly different percent cover among site-index classes for stem-analyzed pine and spruce, respectively. Individual species cover values were then used in simple and multiple linear regression equations to predict the site index (at 70 years) for pine and spruce in 60–90 year and 91–160 year stand age subsets. Equations for pine based on understory species cover explained 38% of the variance in site index in younger stands and 59% in older stands; comparable maxima for spruce were 42% in younger stands and 50% in older stands. These percentages may be too low for stand-alone predictions of site index. Several possible sources of error may cause the low explained variance, including crude field estimates and seasonal variations of cover. Many of these potential sources of error could be minimized, allowing better prediction of forest site quality.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 8
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    Analytical Study of a Braced Excavation in Weak Clay (1972)
    Canadian Science Publishing
    Details
    Publication Date: 1972-05-01
    Description: Analysis of the problem of braced excavations is complicated by the large number of variables involved and by the complex interaction and behavior of the soil and the supporting materials. For this reason a parametric study was made using the finite-element method of analysis to evaluate the influences of the variables. A rather unique computer modelling technique has been used to accommodate both the large number of variables and the problem of interaction and dissimilar behavior. An example of a computer simulation of a well-instrumented braced cut in Norway is given in sufficient detail to illustrate the applicability of the program.For the parametric study a typical excavation with fully penetrating sheet-pile walls was chosen. Of the parameters concerning soil conditions, the soil deformation modulus was found to have the greatest influence. The relative influence of shear strength, of initial in situ stress, of direction of mobilization of shear stress, and of soil-to-pile adhesion is also shown. All of the parameters concerning support conditions are important but pile stiffness and effective strut stiffness are the most important. The influence of prestressing and strut spacing is also shown.
    Print ISSN: 0008-3674
    Electronic ISSN: 1208-6010
    Topics: Geosciences
    Published by Canadian Science Publishing
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