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  • 1
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    Canadian Journal of Forest Research
    Ottawa : National Research Council of Canada
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    Call number: ZS-027
    ISSN: 0045-5067
    Branch Library: GFZ Library
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of temperature on mechanical properties of standing lodgepole pine trees (2000)
    Springer
    Trees 14 (2000), S. 424-428 
    Details
    ISSN: 0931-1890
    Keywords: Young's modulus Modulus of rupture Tree bending Frozen sapwood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. To estimate strength parameters of living lodgepole pine stems over a range of temperatures (–16 to +17°C), trees were winched near or past the point of breakage, during which the applied force and deflection of the stem were measured. Trees were 43 years old, 10 m tall, and since the experiments were conducted in the late winter and early spring, when the soil was frozen and the roots were held rigid, the resistance of the stem to deflection could be isolated from the resistances of the root and soil. Static flexure theory for cantilever beams was used to estimate stress, strain, Young's modulus (E), and modulus of rupture (MOR) of the stem. Trees were stiffer and stronger in the winter when wood was frozen, with a nearly 50% increase in E and MOR compared with the spring, when wood was thawed. In winter stems failed on the tension side, while in spring stems buckled on the compression side. Compared with strength estimations reported in the literature from small samples of clear green wood at standard temperatures, modulus of elasticity (MOE) estimates of the whole stem were 35% lower in spring, and in winter MOR exceeded published values by 53%. This suggests that the sway behavior of trees is probably temperature dependent in northern forests and whole-tree strength characteristics should be considered in wind sway models used in these regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004680000065
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  • 3
    Electronic Resource
    Electronic Resource
    Naturally Saline Boreal Communities as Models for Reclamation of Saline Oil Sand Tailings (2005)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Restoration ecology 13 (2005), S. 0 
    Details
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Reclaimed landscapes after oil sands mining have saline soils; yet, they are required to have similar biodiversity and productivity as the predisturbance nonsaline landscape. Given that many species in the boreal forest are not tolerant of salinity, we studied the effects of soil salinity on plant communities in natural saline landscapes to understand potential plant responses during the reclamation process. Vegetation–soil relationships were measured along transects from flooded wetlands to upland forest vegetation in strongly saline, slightly saline, nonsaline, and reclaimed boreal landscapes. In strongly saline landscapes, surface soil salinity was high (〉10 dS/m) in flooded, wet-meadow, and dry-meadow vegetation zones as compared to slightly saline (〈5 dS/m) and nonsaline (〈2 dS/m) landscapes. Plant communities in these vegetation zones were quite different from nonsaline boreal landscapes and were dominated by halophytes common to saline habitats of the Great Plains. In the shrub and forest vegetation zones, surface soil salinity was similar between saline and nonsaline landscapes, resulting in similar plant communities. In strongly saline landscapes, soils remained saline at depth through the shrub and forest vegetation zones (〉10 dS/m), suggesting that forest vegetation can establish over saline soils as long as the salts are below the rooting zone. The reclaimed landscape was intermediate between slightly saline and nonsaline landscapes in terms of soil salinity but more similar to nonsaline habitats with respect to species composition. Results from this study suggest it may be unrealistic to expect that plant communities similar to those found on the predisturbance landscape can be established on all reclaimed landscapes after oil sands mining.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1526-100X.2005.00085.x
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  • 4
    Electronic Resource
    Electronic Resource
    Stomatal conductance and xylem sap properties of aspen (Populus tremuloides) in response to low soil temperature (2004)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 122 (2004), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The mechanisms regulating stomatal response following exposure to low (5°C) soil temperature were investigated in aspen (Populus tremuloides Michx.) seedlings. Low soil temperature reduced stomatal conductance within 4 h, but did not alter shoot xylem pressure potential within 24 h. The xylem sap composition was altered and its pH increased from 6.5 to 7.1 within the initial 4 h of the low temperature treatment. However, the increase in abscisic acid (ABA) concentration in xylem sap was observed later, after 8 h of treatment. These changes were accompanied by a reduction in the electrical conductivity and an increase in the osmotic potential of the xylem sap. The timing of physiological responses to low soil temperature suggests that the rapid pH change of the xylem sap and accompanying changes in ion concentration were the initial factors which triggered stomatal closure in low temperature-treated seedlings, and that the role of the more slowly accumulating ABA was likely to reinforce the stomatal closure. When leaf discs were exposed to xylem sap extracted from low soil temperature-treated plants, stomatal aperture was negatively correlated with ABA and positively correlated with K+ concentrations of the xylem sap. The stomatal opening in the leaf discs linearly increased in response to exogenous KCl concentrations when K+ concentrations were in the similar range to those detected in the xylem sap. The lowest concentration of exogenous ABA to induce stomatal closure was several-fold higher compared with the concentration present in the xylem sap.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.2004.00385.x
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  • 5
    Electronic Resource
    Electronic Resource
    Photosynthetic strategies of summergreen and evergreen understory herbs of the boreal mixedwood forest (1997)
    Springer
    Oecologia 112 (1997), S. 173-178 
    Details
    ISSN: 1432-1939
    Keywords: Key words Evergreen ; Light and temperature response ; Physiology ; Summergreen ; Understory herbs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal differences in photosynthesis and stomatal conductance of four herbaceous perennials from beneath a deciduous canopy was assessed at two light levels (60 and 400 μmol m−2 s−1 photosynthetic photon flux density, PPFD) and two leaf temperatures (7 and 20°C). Leaves of an evergreen, Pyrola asarifolia Michx., a wintergreen, Cornus canadensis L., and two summergreen species, Rubus pubescens Raf. and Aralia nudicaulis L., were collected at four times during the growing season. In addition, midsummer light response curves were obtained for one summergreen (A. nudicaulis) and one evergreen species (P. asarifolia) at both 7 and 20°C. Gas exchange measurements were made in the laboratory under controlled environmental conditions. For leaves collected in April, when insolation was high due to the leafless overstory, only P. asarifolia had green leaves, and there was no effect of temperature or light on this species' photosynthesis. P. asarifolia's net assimilation rate (NA) in April was about 30% of it's maximum in late summer. In early summer (June), A. nudicaulis and R. pubescens had higher NA at the higher temperature; at this time, these summergreen species also reached their maximum NA. Midsummer photosynthetic light response curves showed that the light-saturation point was higher and more responsive to leaf temperature in the summergreen A. nudicaulis than in the evergreen P. asarifolia. The summergreen species appear to have a photosystem which performs at high rates during early- and mid-summer, as well as a taller stature which allows them to intercept more light. The photosynthetic system of the ever/wintergreen species is adapted to the low ground-level light conditions in the summer and there does not appear to be an adjustment to take further advantage of the higher light in the spring and fall period. The adaptation of the evergreen and wintergreen understory species is tolerance to low temperatures, enabling them to photosynthesize into the fall till the first continuous frosts occur in the understory and also permitting the evergreen species to begin photosynthesis early in the spring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050297
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  • 6
    Electronic Resource
    Electronic Resource
    Is long-lived foliage in Picea mariana an adaptation to nutrient-poor conditions? (1992)
    Springer
    Oecologia 91 (1992), S. 184-191 
    Details
    ISSN: 1432-1939
    Keywords: Foliar nutrient retranslocation ; Needle age ; Photosynthesis ; Nitrogen ; Phosphorus ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study evaluated the contribution of different ages of foliage to the nutrient and carbon balance of black spruce (Picea mariana (Mill.) B.S.P.) from a nutrient-poor peatland in Alberta. Seasonal patterns of foliar nitrogen and phosphorus concentration and content were examined in six needle cohorts up to 10 years old. Trees were treated to simulate excess nutrient deficiency (removal of all one-year-old foliage), nutrient excess (fertilized with 250, 50, 100 kg ha−1 NPK split application in June and July), or left as controls. Gas exchange (net assimilation-Na, stomatal conductance-gs, mesophyll conductance-gm, water-use efficiency-WUE, dark respiration-RS) was measured on six different needle cohorts in several control trees in 1989 and 1990. Nitrogen and phosphorus concentration decreased with needle age. Foliar nutrient concentration fell from April to June and then was stable until September except for the fertilized trees where it increased. There was no evidence of greater than normal retranslocation of nutrients from older needles for defoliated trees or greater than normal nutrient loading in older needles of fertilized trees. NA, gs, gm, WUE, and RS were similar for all needles up to six or eight years old, these older needles having NA of 65% of current needles and similar RS. The results do not support to conclusion that older needles of black spruce are retained as an adaptation to nutrient stress. It does not appear that older needles serve as a nutrient storage site in conditions of excess nutrient availability or a greater than normal nutrient source during times of excess nutrient deficiency. It appears that the maintenance of long-livedfoliage in black spruce does not provide for greater flexibility in tree nutrient allocation. Their contribution to the carbon balance of the tree seems to be sufficient to explain their retention.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317782
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  • 7
    Electronic Resource
    Electronic Resource
    Rhizome growth of Calamagrostis canadensis into mounds created for tree seedling establishment (1999)
    Springer
    New forests 18 (1999), S. 245-262 
    Details
    ISSN: 1573-5095
    Keywords: competition ; mounding ; rhizome ecology ; rhizome resources ; silviculture ; site preparation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Mineral soil-capped, inverted mounds (a layer of organic matter topped by a mineral soil cap on an undisturbed in situ soil horizon) are often created as planting sites for tree seedlings in areas dominated by a very competitive grass, Calamagrostis canadensis. Mounding, however, has had variable success at slowing the spread of this grass into the planting sites. A series of three field experiments investigated the pattern of rhizome growth of C. canadensis into mounds. Experiment 1 tested the interaction of mound thickness and clonal connections of C. canadensis to plants outside the mounds; experiment 2 the removal of the organic layer containing most of the rhizomes (screefing) prior to mounding, and experiment 3 the effect of mulching and fertilising on penetration and distribution of rhizomes through the mound. The thickness of the mineral soil cap was the most important factor determining the success of C. canadensis colonisation, while clonal connections were only of importance for shallow mounds. Screefing before creating the mound resulted in a reduction of C. canadensis establishment. Rhizome penetration from plants outside of the mound was not strongly affected by fertilising and mulching. A fourth experiment, conducted in a controlled environment, tested the ability of rhizomes from buried C. canadensis sods to grow through mineral soil caps of different thickness. The grass sods had different growth potentials which were achieved by a pre-treatment of two levels of light and nutrients, resulting in high and low rhizome carbohydrate concentrations. Low reserves did not reduce the ability of rhizomes to penetrate any thickness of the mineral soil cap. Strategies of C. canadensis establishment on mounds are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006689224611
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  • 8
    Electronic Resource
    Electronic Resource
    Diurnal cycles of rhizosphere acidification byPinus contorta seedlings (1994)
    Springer
    Plant and soil 162 (1994), S. 299-302 
    Details
    ISSN: 1573-5036
    Keywords: diurnal pattern ; light ; nitrogen nutrition ; nitrogen source ; pine ; pH ; proton extrusion ; roots ; solution culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The pH of the nutrient solution bathing the roots of four-month-oldPinus contorta var.latifolia Englm. seedlings was monitored continuously between additions of nutrients. Nitrogen was supplied in the form of NH4NO3, and was added three times per week in amounts relative to seedling fresh weight. No pH change was associated with the nutrient addition cycle; however, extinguishing of the lights at night resulted in a decrease in pH of almost half a pH unit in the first hour. The pH reverted to normal within a few hours. Re-illumination resulted in a pH increase of a smaller magnitude, but over a similar time span. Estimation of the proton extrusion rate gave values of about 17 µmol (g FW root)−1 h−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01347717
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  • 9
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    Ecology of and control strategies for Calamagrostiscanadensis in boreal forest sites (1993)
    Canadian Science Publishing
    Details
    Publication Date: 1993-10-01
    Description: Calamagrostiscanadensis (Michx.) Beauv. is a widely distributed rhizomatous grass that can seriously inhibit growth of white spruce (Piceaglauca (Moench) Voss) seedlings in the boreal forests of North America. We review the dynamics of this grass during four successional stages: the colonization of disturbed sites; dominance of the site by the grass a few years after disturbance; gradual loss of dominance with overstory development; and maintenance of the grass at low levels in the understory of the mature forest. We also describe C. canadensis in relation to recruitment from clonal growth and seed, environmental conditions for growth, the effects of grass litter buildup on conifer seedling microclimate, and overall competitive abilities. Control strategies for C. canadensis are as follows. If the grass is found in nearly every square metre in the understory prior to logging, there will be rapid spread when the stand is clear-cut unless clones are killed using herbicides or a deep burn. Large spruce seedlings, planted on large soil scalps or mounds, coupled with release by way of herbicides or sheep grazing, may be necessary for plantation establishment under conditions of encroachment by C. canadensis. Alternatively, the shade provided by a partial canopy may inhibit the grass sufficiently to allow spruce seedlings to establish. If grass is not abundant in the understory, we recommend (i) minimizing forest floor disturbance to reduce sites for grass seedling colonization or (ii) a slash burn with the hope of encouraging colonization by herbaceous species that have less impact on conifer seedlings.
    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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  • 10
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    Assisted lodgepole pine regeneration on reclamation sites using logging slash as both a mulch and natural seed source (2016)
    Canadian Science Publishing
    Details
    Publication Date: 2016-09-01
    Description: In this study, we tested the efficacy of establishing lodgepole pine (Pinus contorta Dougl.) from seed using woody mulch produced from slashed tree tops from a pine harvesting site; this mulch contained the closed serotinous cones of the lodgepole pine. Mulch was spread on prepared reclamation sites at depths of 0, 1, 3, and 5 cm. Broadcast seeding of pine was also done at mulch depths of 0 and 1 cm. Mulch cover that was 1 cm thick was the preferred treatment, as it produced 17 000 seedlings·ha−1 by the third year after treatment while being similar in seedling density to the 3 and 5 cm treatments. When 50 000 seeds·ha−1 were added, seedling density went up more on the sites with 1 cm of mulch than the sites with no mulch. Soil temperature was lower and temperature extremes were reduced under the mulch layer compared with the control plot. The plots with 1 cm of mulch also had higher soil moisture in the mineral layer than the plots with 0 cm of mulch. A thin layer of woody mulch, therefore, provided a source of pine seed and the covering of the ground provided a more benign environment for the establishment of pine germinants.
    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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