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UBC Theses and Dissertations
Plant succession after active layer detachment slides, in high Arctic tundra, Fosheim Peninsula, Ellesmere Island, Canada Desforges, Manon
Abstract
Vegetation succession patterns and processes were studied after active layer detachment slides. These natural disturbances were grouped into four age categories in the valleys Hot Weather Creek and Big Slide Creek on the Fosheim Peninsula, Ellesmere Island (80°N). A time-space substitution was used to build a surrogate revegetation sequence in order to evaluate primary succession in the scar and secondary succession in the toes of the slides. Vegetation cover and environmental characteristics were measured using haphazard sampling along transects laid across the slide, during the summer of 1994. TWLNSPAN and detrended canonical correspondence analysis were used together to examine vegetation patterns in relation to environmental variables. Sexual reproduction effort was measured from harvested seed and seed bank samples to assess it role as one mechanism driving plant succession. The change in viable seed production for species of two life history groups (ruderal and late-sere grasses and forbs) and the change in seed bank density and composition were examined in relation to the above-ground vegetation and terrain age. Variation in species composition was accounted for by a combination of terrain age and environmental factors. In the scar, where environmental conditions improved over time, primary succession was directional with eventual replacement only in the oldest terrain. The succession followed four main stages of dominance: ruderal grass and forb -> late sere grasses and forb -> shrubs, late sere forbs and grasses -> shrubs and cushion plants. In the toe, which experienced and reduction in soil moisture over time, a retrogressive succession was observed with reduced density and diversity of species, and shift to species better adapted to surviving drought. Large seed production by ruderal species in all terrain ages of the scars suggest that the absence of these species in the oldest terrain does not result from a reduction of resource allocation to reproductive efforts due to possible inter-species interaction. However, the slight reduction of seed production in the more severe environment of the aging toes indicates the important role of physical environmental factors. Total seed bank densities were large and more comparable to temperate environments or disturbed habitats, confirming the importance of sexual reproduction efforts in these ecosystems. Dissimilarity between the germinable seed bank and the extant vegetation composition throughout the successional sequence was expressed by the large number of seeds of late sere grasses in the young scars and the large number of seeds of ruderal species in the old scars. This suggests that seed dispersal occurs at a scale beyond the local vegetation cover, most likely as a result of winter seed rain. This study agrees with succession models that incorporate levels of environmental severity. In habitats with low environmental stress, patterns of community change, with eventual species replacement, were possibly governed by the same sort of processes described in more temperate environments and classical models of succession, but with a much slower rate of change. However, with increases in environmental stress, succession shifted from species replacement to species establishment and survival.
Item Metadata
Title |
Plant succession after active layer detachment slides, in high Arctic tundra, Fosheim Peninsula, Ellesmere Island, Canada
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2001
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Description |
Vegetation succession patterns and processes were studied after active layer
detachment slides. These natural disturbances were grouped into four age categories in the
valleys Hot Weather Creek and Big Slide Creek on the Fosheim Peninsula, Ellesmere Island
(80°N). A time-space substitution was used to build a surrogate revegetation sequence in
order to evaluate primary succession in the scar and secondary succession in the toes of the
slides. Vegetation cover and environmental characteristics were measured using haphazard
sampling along transects laid across the slide, during the summer of 1994. TWLNSPAN and
detrended canonical correspondence analysis were used together to examine vegetation
patterns in relation to environmental variables. Sexual reproduction effort was measured
from harvested seed and seed bank samples to assess it role as one mechanism driving plant
succession. The change in viable seed production for species of two life history groups
(ruderal and late-sere grasses and forbs) and the change in seed bank density and composition
were examined in relation to the above-ground vegetation and terrain age.
Variation in species composition was accounted for by a combination of terrain age
and environmental factors. In the scar, where environmental conditions improved over time,
primary succession was directional with eventual replacement only in the oldest terrain. The
succession followed four main stages of dominance: ruderal grass and forb -> late sere
grasses and forb -> shrubs, late sere forbs and grasses -> shrubs and cushion plants. In the
toe, which experienced and reduction in soil moisture over time, a retrogressive succession
was observed with reduced density and diversity of species, and shift to species better
adapted to surviving drought.
Large seed production by ruderal species in all terrain ages of the scars suggest that
the absence of these species in the oldest terrain does not result from a reduction of resource
allocation to reproductive efforts due to possible inter-species interaction. However, the
slight reduction of seed production in the more severe environment of the aging toes indicates
the important role of physical environmental factors. Total seed bank densities were large
and more comparable to temperate environments or disturbed habitats, confirming the
importance of sexual reproduction efforts in these ecosystems. Dissimilarity between the
germinable seed bank and the extant vegetation composition throughout the successional
sequence was expressed by the large number of seeds of late sere grasses in the young scars
and the large number of seeds of ruderal species in the old scars. This suggests that seed
dispersal occurs at a scale beyond the local vegetation cover, most likely as a result of winter
seed rain.
This study agrees with succession models that incorporate levels of environmental
severity. In habitats with low environmental stress, patterns of community change, with
eventual species replacement, were possibly governed by the same sort of processes
described in more temperate environments and classical models of succession, but with a
much slower rate of change. However, with increases in environmental stress, succession
shifted from species replacement to species establishment and survival.
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Extent |
8684703 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-07-27
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0089829
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2001-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.