Primary plant succession was examined on the foreland of the retreating Twin Glacier
at Alexandra Fjord, Ellesmere Island. The position of the glacial front was monitored directly
from 1980 to 1995 (except 1986-1991), and airphotos show the position of the glacier in 1959.
Hence, there was an excellent opportunity to study primary succession where there was
adequate chronological control. Presently, a well preserved pre-Little Ice Age plant
community and organically rich (paleo) soil are being released from the Twin Glacier, in
addition to glacio-fluvial sediments, rendering this foreland study unique.
A terrain age scheme was developed using direct retreat measurements, airphotos and
Salix aging. The relationship between the clump diameters of Luzula confusa and terrain age
was determined to provide an alternative to lichenometry. Vegetation cover was assessed in
1994 and 1995 using a stratified random design. TWINSPAN and canonical correspondence
analysis (detrended and non-detrended) were used together to examine vegetation patterns in
relation to environmental variables. Soil seed bank and seed rain patterns were examined in
relation to the above-ground vegetation. The seed bank was sampled in 1994, including
samples from paleo-soil and glacio-fluvial sediment. To assess the fall-winter seed rain, seeds
were collected between mid-August 1994 and early June 1995, using seed traps (artificial turf).
Winter seed rain was sampled by collecting snow-core samples in early June 1995.
Terrain age accounted for most of the variation in species composition over the study
area. By directional-replacement, the succession followed four main stages of dominance in
44+ years: mosses —> graminoid-forb —> deciduous shrub-moss —> evergreen dwarf-shrubmoss.
There was little difference in the successional sequences exhibited by the vegetation
growing on the paleo-soil compared to that growing on the glacio-fluvial sediment. The
relationship between the Luzula confusa clump diameters and terrain age was logarithmic.
Luzula confusa dominated the above-ground vegetation, as well as, the germinable seed bank
and seed rain. The average germinable seed bank, fall-winter seed rain and winter seed rain
densities were 367 ± 32, 384 ± 47 and 180 ± 53 seeds/m2, respectively. The seed bank was
significantly positively correlated with the above-ground vegetation cover for all species
combined, Luzula confusa (monocotyledons), dicotyledons and Papaver radicatum. There
was a significant positive correlation between the fall-winter seed rain and the above-ground
vegetation cover for Luzula confusa. No difference was detected in seed bank density between
the paleo-soil and the glacio-fluvial sediment. However, the total vegetation cover was
significantly higher on the paleo-soil.
The relationship determined between Luzula confusa clump diameters and terrain age
appears to be a valuable alternative to lichenometry on the Twin Glacier foreland. Although
the results showed that directional-replacement is possible in high arctic environments, this
mode of succession is likely atypical of such environments; the Twin Glacier foreland is located
in one of the very few polar oases in the Queen Elizabeth Islands. The positive correlation of
the above-ground vegetation with the seed bank and fall-winter seed rain suggests that
colonization is largely constrained by seed availability. The winter seed rain appears to be
relatively important on the Twin Glacier foreland. The higher vegetation cover on the paleosoil
versus the glacio-fluvial sediment suggests, at least for some species, that the former
provides conditions more favourable for establishment and growth than the latter.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/5817 |
| Date | 05 1900 |
| Creators | Jones, Glenda A. |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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