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Niagara
Issues - White Cedar http://www.mobot.org/plantscience/ResBot/niag/ |
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Niagara
Issues - White Cedar The series of images
below show population of White Cedar (Thuja occidentalis), an
evergreen species mostly associated with swamps on level ground. Their
occurrence in these substrates seems counter-intuitive were it not for
year-round seepage. Special tufa-forming moss communities also enjoy such
discharges and form the substrate for vascular species of interest, such as Cystopteris
bulbifera, one of the most distinctive ferns of the gorge and the Niagara
Escarpment, as well as Lobelia kalmii, the type locality of which was
thought by some to have derived from Niagara Falls. The rare fern Pellaea
glabella also grows on such forbidding exposures and nowhere else here.
In spring the gray rock-face is illuminated by the nodding scarlet blooms of Aquillegia
canadensis. Although populations of
White Cedar have been found to show ancient growth along the Niagara
Escarpment in Ontario, it remains problematical whether the Niagara
populations display similar ages. Note in the final two images specimens that
appear to be juveniles. Since such trees grow in the caprock, they are
vulnerable to sapping by authorities who judge caprock ledges to be
dangerous, the so-called 'table rocks' that project out into space, their
softer supporting substrates having eroded away from under them. Gorge forests display
formation in horizontal tiers: above the gorge rim there is Sugar Maple (Acer
saccharum) and Red Oak (Quercus borealis) dominated woods with
certain interesting Oak-Hickory assemblages as in the southern sector of Whirlpool
woods including aboriginal trees allowed to flourish on the Robert Moses
Parkway there. The next tier are the Thuja-dominated caprock trees.
Talus slopes display Walnut species (Juglans
nigra and cinerea), Hop-hornbeam (Ostrya virginiana),
Basswood (Tilia americana) and a host of secondary species. The bottom
tier along the shoreline is Paper Birch (Betula papyrifera), Yellow
Birch (Betula allegheniensis), lovely species of Shadbush (Amelanchier
spp.), three species of Poplar (Populus tremuloides, P. deltoids,
P. grandidentata) and various willows, including the big foreign species Salix
fragilis and S. alba, but also shrubby native species such as
Pussy willow (Salix discolor) and Bebb's Willow (Salix bebbiana). This does not include
extensive areas of replacement forest dominated by Box Elder (Acer negundo)
and Norway Maple (Acer platanoides).
A note of caution for
those who might expect to identify and count White Cedar tree populations
from photographs or from a distance, as with binoculars from the base or top
of the gorge, or across the river to the opposite shore. The Juniper is also
an evergreen tree with similar shape and texture. It has needle-shaped
leaves, whereas those of the White Cedar are scale-shaped. This specimen at
Devil's Hole in the town of Lewiston above the escarpment is a Juniper tree (Juniperus
virginiana). |
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