vegetation and vegetation-environment relationships in a muskeg-fen near thunder bay, ontario
abstract
this study takes place in an endangered peatland
within the city of thunder bay ontario. the study area,
william bog, is one of a few remaining peatlands in the
thunder bay district which have developed on abandoned
minong phase lake basins on the north shore of lake superior.
an inventory of vascular plants, mosses, hepatics, and
ground lichens reveals that the vascular flora is richer
than the moss or hepatic flora and that ground lichens are
rare. vegetation zones identified in the study area are
similar to communities described for peatlands in ontario
by jeglum et.al. (1974). the study area is centered on a
carex spp. dominated graminoid fen which is bounded to the north and west by a conifer swamp, and to the east by a
shrub rich treed bog. ordination of vegetation data reveals
that vegetation varies continuously from fen to swamp and
from fen to bog. the nature and flow of groundwater is
related to vegetation type such that within the fen, and
to the north and west, vegetation can be classified as
mlnerotrophic. east of the fen vegetation appears to be
ombrotrophic in nature. the ph of both soil and water,
calcium concentration , and conductance of water samples
varies continuously along the vegetation gradients. this
results in a corresponding environmental gradient which
runs from strongly minerotrophic (fen) to weakly minerotrophic (conifer swamp) to the north and west, and from strongly minerotrophic (fen) to ombrotrophic (bog) in the east.
william bog exibits consistently higher and lower
air temperatures when compared to the thunder bay airport,
3 km sw, this peatland has a significantly shorter frost
free period. within the study area peats are coolest in
ombrotrophic sphagnum spp. hummocks east of the fen, and
frost persists within these hummocks well into the growing
season. west of the fen peats are warmer, likely the result
of subsurface groundwater flow. there is no evidence of
permafrost in the study area.
the historical and evolutionary development of william
bog is based upon the lateral expansion of phragmites communis
marshes through paludification of the sandy lowland basin.
this resulted in two developmental sequences which are based
upon the flow of groundwater within the basin. minerotrophic
communities evolve where groundwater flow is concentrated.
ombrotrophic communities develop in drier sites where sphagnum
spp. growth elevates the surface above the influence of
groundwater. dynamics between these communities are based
upon local climatic variations during the period following
initial colonization of the site, and disturbance by wildlife.
the proposed development of vegetation in william bog appears
to resemble sequences proposed by several peatland
studies undertaken in northern minnesota, southern ontario,
and southern quebec.
collections
- retrospective theses [1604]