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  • 1
    Electronic Resource
    Electronic Resource
    Evaluation of Fine Root Length and Diameter Measurements Obtained Using RHIZO Image Analysis (1999)
    Springer
    Semigroup forum 91 (1999), S. 142-147 
    Details
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: -2 . For samples with higher values, however, the method underestimated total length by 〉5%. It is therefore recommended that users of image analysis systems determine this maximum length per unit area for accurate determinations of total root length. In samples that contained different string diameters, the total sample length and average string diameter could accurately be measured. However, the length per diameter class was underestimated by 〉20% when the string diameter was less than one pixel smaller than the upper limit of the diameter class. Adjustment of diameter intervals and increasing the scanner resolution are required to reduce this underestimation. Both the length and the angle of the short segments analyzed were found to influence diameter measurement. Similar sets of experiments are proposed for a rigorous evaluation of the performance of other image analysis systems on root measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of soil mixing on soil nutrient status, recovery of competing vegetation and conifer growth on cedar-hemlock cutovers in coastal British Columbia (1995)
    Springer
    New forests 9 (1995), S. 163-179 
    Details
    ISSN: 1573-5095
    Keywords: Thuja plicata ; Tsuga heterophylla ; Gaultheria shallon ; organic matter dynamics ; competition ; disturbance ; soil pH ; soil temperature ; soil N and P availability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In 1988 an experiment was established to stimulate the effect of windthrow on low-and high-productivity forest types in coastal British Columbia. It was hypothesized that site productivity may be improved by mixing the upper 1 m of the organic matter and mineral soil. Results of this study indicated that soil mixing (1) slightly increased soil pH and temperature on both forest types after 2 and 5 years, (2) decreased all soil nutrient availability indices on the high productivity type after 2 years, but resulted in no difference from the control after 5 years, and (3) decreased microbial activity and cellulose loss rate and most soil nutrient availability indices on the low-productivity type after 2 and 5 years. Soil mixing greatly reduced Gaultheria shallon above-ground biomass on both low- and high productivity forest types, whereas biomass of Epilobium angustifolium and other plant species increased slightly on the high-productivity type after 2 and 5 vears. Tsuga heterophylla was taller on high-productivity type and on mixed plots in both types after 2 and 5 years. Thuja plicata was taller on the high-productivity type after 5 years only. The increased conifer growth measured on the mixed low-productivity type was attributed to higher levels of available nutrients due to reduced G. shallon competition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035485
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  • 3
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    Functional ecology of advance regeneration in relation to light in boreal forests (1999)
    Canadian Science Publishing
    Details
    Publication Date: 1999-06-01
    Description: This paper reviews aspects of the functional ecology of naturally established tree seedlings in the boreal forests of North America with an emphasis on the relationship between light availability and the growth and survival of shade tolerant conifers up to pole size. Shade tolerant conifer species such as firs and spruces tend to have a lower specific leaf mass, photosynthetic rate at saturation, live crown ratio, STAR (shoot silhouette area to total needle surface area ratio), and root to shoot ratio than the shade intolerant pines. The inability of intolerant species such as the pines and aspen to survive in shade appears to be mainly the result of characteristics at the shoot, crown, and whole-tree levels and not at the leaf level. Although firs and spruces frequently coexist in shaded understories, they do not have identical growth patterns and crown architectures. We propose a simple framework based on the maximum height that different tree species can sustain in shade, which may help managers determine the timing of partial or complete harvests. Consideration of these functional aspects of regeneration is important to the understanding of boreal forest dynamics and can be useful to forest managers seeking to develop or assess novel silvicultural 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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  • 4
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    Forest dynamics following spruce budworm outbreaks in the northern and southern mixedwoods of central Quebec (2007)
    Canadian Science Publishing
    Details
    Publication Date: 2007-04-01
    Description: The effects of 20th century spruce budworm ( Choristoneura fumiferana (Clem.)) outbreaks on forest dynamics was examined in the southern and northern parts of the mixedwood forest zone in central Quebec, Canada. In each region, three study areas were placed in unmanaged stands that had not burned for more than 200 years. Disturbance impacts and forest succession were evaluated using aerial photographs and dendrochronology. Spruce budworm outbreaks occurred around 1910, 1950, and 1980 in both regions. The 1910 outbreak seemed to have limited impact in both regions, and the 1950 outbreak caused heavy mortality in conifer stands (mostly of balsam fir, Abies balsamea (L.) Mill.) in the southern region. The 1980 outbreak caused major mortality in the northern region, but had little impact in the southern region. Successive spruce budworm outbreaks led to a massive invasion by hardwood species in the last century in the southern region but not in the northern region. The reason for such contrasting dynamics between regions is unknown, but we hypothesize that differences in disturbance intensities, influenced by climate, played a major role. Results from this study emphasize that generalizations about the effect of spruce budworm outbreaks on forest dynamics cannot be derived from observations made during a single outbreak or at a single location.
    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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  • 5
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    Patterns of above- and below-ground response of understory conifer release 6 years after partial cutting (2002)
    Canadian Science Publishing
    Details
    Publication Date: 2002-02-01
    Description: An increased pressure to use silvicultural techniques not based on clear-cutting followed by planting has led to an interest in systems that take advantage of existing understory seedlings (advance regeneration). Earlier studies have suggested that following harvesting, understory seedlings may experience growth reductions before responding with growth increases. We hypothesize that this "growth shock" following release results because seedlings are ill adjusted to the new growing conditions and that this can be investigated through a comparison of growth in different parts of the tree over a 6-year period. This study compares the growth response of three size classes of lodgepole pine (Pinus contorta Dougl. ex Loud.) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings to a partial overstory removal in relatively dry conifer forests of central British Columbia. Growth was evaluated in four parts of the studied trees: radial increment in roots, in the base of the stem, and in branches, as well as leader height growth extension. Our findings show that following release from the overstory, early growth increases were largest in the roots and stems irrespective of the species or the size class. Differences between the species were observed in greater absolute height growth for pine, whereas Douglas-fir invested in greater stem growth, especially in the larger individuals. Important differences also occurred temporally. Both species (and all size classes) responded with an immediate increase in root growth followed, after a 1-year delay, by an increase in stem growth. Branch radial increment (for pine) and leader height growth (both species), however, experienced 2 to 3 year growth reductions before responding. It is therefore suggested that individuals restore the rootshoot balance by greater initial investments to root growth to offset the increased transpiration losses associated with the greater light and higher temperature conditions and the relative changes in the photosynthetic versus nutrient uptake capacity following the canopy opening. Foresters may therefore be able to manipulate tree growth responses by using an appropriate degree of overstory removal or opening size.
    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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    Overstory influences on light attenuation patterns and understory plant community diversity and composition in southern boreal forests of Quebec (2006)
    Canadian Science Publishing
    Details
    Publication Date: 2006-09-01
    Description: We have characterized overstory light transmission, understory light levels, and plant communities in mixed wood boreal forests of northwestern Quebec with the objective of understanding how overstory light transmission interacts with composition and time since disturbance to influence the diversity and composition of understory vegetation, and, in turn, the further attenuation of light to the forest floor by the understory. Overstory light transmission differed among three forest types (aspen, mixed deciduous–conifer, and old cedar-dominated), with old forests having higher proportions of high light levels than aspen and mixed forests, which were characterized by intermediate light levels. The composition of the understory plant communities in old forests showed the weakest correlation to overstory light transmission, although those forests had the largest range of light transmission. The strongest correlation between characteristics of overstory light transmission and understory communities was found in aspen forests. Species diversity indices were consistently higher in aspen forests but showed weak relationships with overstory light transmission. Light attenuation by the understory vegetation and total height of the understory vegetation were strongly and positively related to overstory light transmission but not forest type. Therefore, light transmission through the overstory influenced the structure and function of understory plants more than their diversity and composition. This is likely due to the strong effect of the upper understory layers, which tend to homogenize light levels at the forest floor regardless of forest type. The understory plant community acts as a filter, thereby reducing light levels at the forest floor to uniformly low levels.
    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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    Balsam fir (Abies balsamea) establishment dynamics during a spruce budworm (Choristoneura fumiferana) outbreak: an evaluation of the impact of aging techniques (2001)
    Canadian Science Publishing
    Details
    Publication Date: 2001-01-01
    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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    Growth and morphological responses of yellow birch, sugar maple, and beech seedlings growing under a natural light gradient (1998)
    Canadian Science Publishing
    Details
    Publication Date: 1998-07-01
    Description: Height and lateral growth, biomass distribution, leaf morphology, and crown architecture were studied in yellow birch (Betula alleghaniensis Britton), sugar maple (Acer saccharum Marsh.), and beech (Fagus grandifolia Ehrh.) seedlings growing under 1-50% of above-canopy light in a sugar maple stand, in Quebec. All three species showed increasing growth with increasing light, but growth of yellow birch was higher and more responsive than that of sugar maple and beech. All three species showed typical sun-shade morphological responses, such as decreasing specific leaf area and leaf area ratio, and increasing leaf area index, with increasing light availability. Sugar maple was morphologically more plastic than the other species. It showed variations in biomass allocation to leaves and branches, a decrease in branch length to seedling height ratio, and a marked increase in the ratio of leaf area to stem length. Although our results clearly demonstrate the ability of these three species to modify several of their morphological features in response to variations in light, they do not show a clear relationship between species shade tolerance and morphological response to light variations. We suggest that species-specific developmental patterns may act as important constraints to morphological acclimation to light variation.
    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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  • 9
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    Can forest management based on natural disturbances maintain ecological resilience? (2006)
    Canadian Science Publishing
    Details
    Publication Date: 2006-09-01
    Description: Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance.
    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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    Consequences of various landscape-scale ecosystem management strategies and fire cycles on age-class structure and harvest in boreal forests (2004)
    Canadian Science Publishing
    Details
    Publication Date: 2004-02-01
    Description: At the landscape scale, one of the key indicators of sustainable forest management is the age-class distribution of stands, since it provides a coarse synopsis of habitat potential, structural complexity, and stand volume, and it is directly modified by timber extraction and wildfire. To explore the consequences of several landscape-scale boreal forest management strategies on age-class structure in the Mauricie region of Quebec, we used spatially explicit simulation modelling. Our study investigated three different harvesting strategies (the one currently practiced and two different strategies to maintain late seral stands) and interactions between fire and harvesting on stand age-class distribution. We found that the legacy of initial forested age structure and its spatial configuration can pose short- (
    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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