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  • 1
    Electronic Resource
    Electronic Resource
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 11 (2003), S. 0 
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Spring burning of sedge-grass meadows in the Slave River Lowlands (SRL), Northwest Territories, Canada was applied between 1992 and 1998 to reduce shrub encroachment and enhance Bison bison (bison) habitat, although the impact of fire on preferred bison forage was unknown before management. In the summer of 1998 we conducted a study in the Hook Lake area of the SRL to test the effect of burn frequency (unburned, burned once, or burned three times since 1992) on herbaceous plant community composition and Salix spp. L. (willow) shrub vigor. Plant species abundance, litter biomass, soil pH, and depth of the organic soil horizon were measured in 300 1-m2 quadrats nested within 30 1,000-m2 plots in both burned and unburned dry meadows. To test the relationship between frequency and willow vigor, all willow shrubs within the plots were assigned a vigor score from I (dead) to IV (flourishing). The spring burns appear to have reduced willow vigor; however, shrub survival remained high (76%) on the most frequently burned meadows. Ordination plots resulting from canonical correspondence analysis suggest that multiple spring burns influenced plant community composition in dry meadow areas and that less palatable bison forage species (e.g., Carex aenea Fern. and Juncus balticus L.) were correlated with a regime of three spring burns. Our results suggest that frequent spring fires in the Hook Lake area have only a small negative effect on willow cover but may reduce the abundance of primary bison forage plants compared with less frequently burned meadows.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 100 (1994), S. 221-228 
    ISSN: 1432-1939
    Keywords: Triticum aestivum ; Competition ; Abiotic stress ; Multiplicative interactions ; Nickel toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using recently developed solution culture techniques, the effect of a non-resource abiotic stress, nickel toxicity, was tested on intraspecific nutrient competition among wheat. The choice of an appropriate statistical model was of paramount importance in interpreting these effects. We argue that a multiplicative model is more appropriate for experiments on interactions of competition and abiotic stress. By such an analysis, nickel had no relative effect on the ability of competition to reduce plant size in two experiments, and caused a small reduction in competition in another. These results are contrary to other reports of the effect of a non-resource abiotic stress on competition and appear to be due to an increased demand for nutrients in the presence of toxic levels of nickel. The effects of an abiotic stress on competition may thus be specitic to the stress and not generalized across all abiotic stresses.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 34 (1997), S. 137-154 
    ISSN: 1573-5052
    Keywords: Community ; Ecological coincidence ; Graph theory ; Influence ; Phytosociology ; Sampling ; Signed digraphs ; Structure ; Unidirectional association
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A method employing samples of variable size is assumed and shown to be useful in the detection of unidirectional associations of one species with another, whether caused by direct influence or by coincidence of ecological requirements. The pattern of these associations from a signed digraph (directed graph), the graph theoretical properties of which give insight into the phytosociological structure of the plant community. The properties of transitivity, balance, homogeneity, reachable sets and types of subgraphs are examined.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 35 (1977), S. 35-46 
    ISSN: 1573-5052
    Keywords: Association ; Digraphs ; Ecological coincidence ; Influence ; Mixed forest community ; Phytosociology ; Sampling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A sampling method, compatible with the theory elaborated in the previous paper, was used to investigate the mixed-forest community of a woodlot in Southern Ontario. The results provide an illustration of the graph theoretical methods developed for the elucidation of a community's phytosociological structure. Certain conjectures about the community are tested and it is found that Goodall's hypothesis concerning the nature of a plant community is supported. The tests also show that the vegetation of the study area forms a single natural grouping despite the disparity of the position ofAcer saccharum and the polarity evident among the other tree species.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 63 (1985), S. 79-88 
    ISSN: 1573-5052
    Keywords: Community ; Graph theory ; Phytosociological structure ; Signed digraph ; Similarity measure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper describes some methods that can be used to compare the phytosociological structure of plant communities using some graph theoretic properties of the directed graphs that represent them. In such a graph, the species are represented by points and the association of species A with species B is represented by a directed line segment going from B to A. Two communities can be compared using simple indices to measure the similarity of their species-lists (point similarity) and of the species associations in them (line similarity). A more sophisticated and informative measure of line similarity is the probability that, given the number of points shared by two graphs, they have at least as many lines in common as they are observed to have. A formula for calculating that probability is given here. The graphs of community structure can also be compared with respect to the homogeneity of the distribution of the lines among the points, a property related to the number of species that are important in determining the composition of the community. These techniques are illustrated using the graphs of the phytosociological structure of intertidal seaweed communities on the southeast coast of Nova Scotia.
    Type of Medium: Electronic Resource
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  • 6
    Publication Date: 2002-08-01
    Description: Post-fire regeneration of Picea glauca (Moench) Voss on boreal mixedwood sites appears to be highly variable over time. Our objectives were to determine whether ground-level ring counts underestimate root collar age of understory P. glauca and whether aging errors increase with stand age. Trees were collected from one to nine stands in each of three fires occurring in mast years between 1961 and 1991. Trees were cut at ground level (humus soil level), and the belowground stumps were excavated, sectioned, and internally cross-dated with skeleton plots after identifying the root-collar location. Ground-level disks were visually cross-dated with a master chronology, which was constructed using the dendrochronology program COFECHA. Ground-level ring counts underestimated age by a mean of 2.4 years (range 06) and 6.4 years (range 013) in 20- and 38-year-old stands, respectively. Age underestimation was significantly greater at the root collar than ground level because of missing rings. Cross-dated age structures showed that apparent regeneration lags in 20- and 38-year-old stands were artifacts of ground-level ring counts and that the first year post-fire was the most important establishment year in all mast year burns. We conclude that aging errors have led to inaccurate depictions of regeneration patterns during early mixedwood stand development. Our results portray a different picture of P. glauca succession and have important implications for forest management.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 7
    Publication Date: 2006-06-01
    Description: The timing of white spruce regeneration in aspen (Populus tremuloides Michx.) white spruce (Picea glauca (Moench) Voss) boreal mixedwood stands is an important factor in stand development. We examined boreal mixedwood stands representing a 59-year period of time since fire and determined (1) whether and when a delayed regeneration period of white spruce occurred, (2) whether the relative abundance of initial (
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 8
    Publication Date: 2007-07-01
    Print ISSN: 1286-4560
    Electronic ISSN: 1297-966X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Springer
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  • 9
    Publication Date: 2009-01-01
    Print ISSN: 1286-4560
    Electronic ISSN: 1297-966X
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Springer
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  • 10
    Publication Date: 2015-01-07
    Description: The nature of tide-topography interaction reflects the topographic scales experienced by water parcels during their tidal excursions. In the deep ocean these scales are typically sub-kilometre, yet direct observations of tidal processes on such scales are lacking. At one site, a saddle amid steep and complex Mid-Atlantic Ridge topography, observations reveal tidally-pulsed, bottom-trapped fronts, overflows and lee waves in response to a tide combined with a mean flow of similar amplitude. The tidal pulsing of the fronts and overflows was only evident locally, and their phase became unpredictable over scales of hundreds of metres. Enhanced turbulence in a 100-200 m thick bottom boundary layer had an estimated dissipation rate of 2.6×10 -2 Wm -2 , exceeding the large-scale average of tidal dissipation in mid-ocean ridge environments but by less than an order of magnitude. This site was not a dissipation ‘hotspot’, and the processes observed could provide widely-distributed mixing to the meridional overturning circulation.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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