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Natural Areas Survey (1996)

City of Mississauga
Natural Areas Fact Sheet by Geomatics International

Scanned copy, if there are errors, please e-mail me with corrections - my comments are at the end, click on the highlighted text to go to specific comments, which will have numbers in brackets e.g.. {1}

This page is out of date.  The City had more work done in 2000 but even that was not up to date.

The Cawthra Bush, in Canada, Ontario, Mississauga, was in 2000 declared a Provincially Significant Wetland Complex and the Jefferson Salamander was also in 2000 declared a federally threatened species by COSEWIC (Committee On the Status of Endangered Wildlife In Canada).  Also, Cawthra Bush has been called an old-growth ecosystem by Paul Maycock, Forest Ecologist, Erindale Campus, University of Toronto but the City will not recognize this fact.

In the map below the EE section was logged in the 1920's and the DD, which is actually a larger section then shown, has never been cut.  All the way back to the ice age.

Natural Area Name - LV7 (Cawthra Woods)

Planning District Area - Lakeview

Hectares - 21.56

UTM Grid Reference - 6148 48261

1. Location - Directly east of Cawthra Road, between the Queen Elizabeth Way and Atwater Avenue.

2. Classification - Significant Natural Site

3. Description - A. Physical Features
The topography of this site is undulating with numerous shallow depressions present in the northern portion that are inundated with water for most of the year. A high perched water table is present in the northeast section of the site. The underlying bedrock geology consists of the grey shales of the Georgian Bay Formation. In the northern portion of the site the soil is Berrien sandy loam which has developed within the Iroquois sand plain. The southern portion has Chinguacousy clay loam soil which has developed within the Halton till plain. Both of these soil types are imperfectly drained. Soil moisture is wet-mesic to wet throughout the site. This site is located primarily within the Cooksville Creek subwatershed, however, the northernmost portion is within the Serson Creek subwatershed.

B. Biota
There are 292 floral species and 75 faunal species documented for this site. Two vegetation communities are present at this site (see accompanying figure): a sugar maple (Acer saccharum ssp saccharum) - red ash (Fraxinus pennsylvanica) - red maple (A. rubrum) forest (EE) in the north, and a sugar maple - American beech (Fagus grandifolia) forest (DD) in the south. The canopy is approximately 25 m in height. The trees are typically 30 cm in diameter, but can range up to 70 cm, and are approximately 80-90 years old {1} (Bird and Hale Ltd., 1989).

The sugar maple-red ash-red maple forest is dominated by mature sugar maple, red ash, and red maple with American beech and black cherry (Prunus serotina) as associates. The canopy in this community is slightly more open as a result of recent logging activities. The shrub layer is dominated by choke cherry (P. virginiana) and maple-leaved viburnum (Viburnum acerifolium). The diverse ground cover includes white trillium (Trillium grandiflorum), red trillium (Trillium erectum), wild leek (Allium triccocum), false Solomon's-seal (Maianthemum racemosum), and yellow trout lily (Erythronium americanum). The depression areas contain a subcanopy of American elm (Ulmus americana) and an understorey dominated by large patches of jewelweed (Impatiens capensis), silvery glade fern (Athyrium thelypterioides), Christmas fern (Polystichum acrostichoides) and sedges (Carex spp.).

The sugar maple-beech forest is dominated by mature sugar maple and beech that form a closed canopy. The leaf litter layer here is thick in places, but, sparse to absent in areas near the east boundary. Large erratics are present throughout. The ground flora is similar to that present in the northern portion of the site, however, it is not as rich. The shrub layer is virtually absent.

The fauna capable of using this site is limited by the former, predominantly agricultural land use that occurred in the area and the current suburban context of the City. With few exceptions, the existing fauna of the City's natural areas is fairly tolerant of urban and suburban conditions and includes common species such as: gary squirrel (Sciurus caroliniensis), raccoon (Procyon lotor), striped skunk (Mephitis mephitis), blue jay (Cyanocitta cristata), northern cardinal (Cardinalis cardinalis), common grackle (Quiscalus quiscula), mourning dove (Zenaida macroura), American robin (Turdus migratorius), and American crow (Corvus brachyrhynchos). These and other tolerant species can be expected in any of the natural areas. Red fox (Vulpes vulpes), coyote (Canis latrans), opossum (Didelphis virginiana) and white-tailed deer (Odocoileus virginianus) are also common residents in some areas of the City. During the spring and fall migration periods, the diversity of birds increases as numerous species utilize remnant natural areas as stopovers en route to breeding or wintering habitat. Also, a few species such as snowy owl (Nyctea scandiaca) and common redpoll (Acanthis flammea) move south in winter and may utilize natural areas in the City. This site is known to be an important roosting area for migrating crows (Ecologistics, 1979). Warblers, thrushes and sparrows utilize this site during migration (Geomatics International, 1995).

This site is currently in good condition. Minor disturbances include old estate relicts within the forest, numerous trails, some beech windthrow, pit excavation, excessive trampling, abundance of litter, and excessive road noise from the Queen Elizabeth Way. The lack of leaf litter and exposed tree roots in some parts along the southeast boundary suggest a drying out of the soils and possible surface erosion. Two recent major disturbances to this site are the installation of a water main along the eastern edge of the site and forest management in the winter of 1994/95. Invasive plant species present at this include Norway maple (A. platanoides), Japanese barberry (Berberis thunbergii), common buckthorn (Rhamnus cathartica) and multiflora rose (Rosa multiflora). One hundred and one introduced plant species are present at this site (representing 33.9% of the total number of species present). This is a high proportion of exotics, partially owing to the former use of the site as an estate. The native FQI is 57.67 and the native mean coefficient is 4.171, both of which are high values. Surrounding land use is residential.


* High native FQI and native mean coefficient

* Identified as a regional Area of Natural and Scientific Interest and Environmentally Significant Area (Cawthra Woods)

* Historical nesting record for red-shouldered hawk (Buteo lineatus).

* Diversity of plant species (292 species)

* Large size (21.56 ha)

* Twelve plant species documented from this site are considered to be rare within the City (known from 3 or fewer locations). These species are: silvery glade fern, stout wood grass (Cinna arundinacea), eastern manna grass (Glyceria septentrionalis), wood millet (Millium effusum), woodland poa (Poa alsodes), the sedges (Carex albursina, C. grayi, and C. laxiculmis), bulrush (Scirpus pendulus), moonseed (Menispermum canadense), skunk currant (Ribes glandulosum), and angelica (Angelica atropurpurea).

* Thirty-four plant species documented from this site are considered to be uncommon within the City (known from 4 to 10 locations). These species are: scouring-rush (Equisetum hyemale), cinnamon fern (Osmunda cinnamomea), glandular wood fern (Dryopteris intermedia), New York fern (Thelypterioides noveboracensis), tamarack (Larix laricina), upland bent grass (Agrostis perennans), nodding fescue (Festuca subverticillata), bottle-brush grass (Hystrix patula), the sedges (C. arctata, C. intumescens, C. plantaginea, C. projecta, and C. retrorsa), nut grass (Cyperus strigosus), false Solomon's-seal (Maianthemum stellatum), bellwort (Uvularia grandiflora), sandbar willow (Salix exigua), shining willow (S. lucida), wood nettle (Laportea canadensis), spearscale (Atriplex patvia), sharp-leaved hepatica (Hepatica acutiloba), hooked buttercup (Ranunculus recurvatus), pink spring cress (Cardamine douglassii), foam flower (Tiarella cordifolia), smaller forget-me-not (Myosotis laxa), long-spurred violet (Viola rostrata), honewort (Cryptotaenia canadensis), sweet cicely (Osmorhiza claytonii), Indian pipe (Monotropa uniflora), turtlehead (Chelone glabra), marsh bedstraw (Galium palustre), Indian tobacco (Lobelia inflate), red-stemmed aster (Aster puniceus), and flat-topped white aster (Aster umbellatus). Area known as a migratory stopover


* Access to the site should be controlled.

* After the water main is installed the Right-Of-Way lands could be restored to expand the area of natural habitat.

* Non-native plants need to be controlled/removed from the site

* The apparent drying out of soils in areas of the southeast portion of the woods should be investigated.

7. Principle References

Bird and Hale Ltd. (1989) Brownell (1993)
City of Mississauga (1978)
Ecologistics Limited (1979)
Geomatics International Inc. (1995)
Hana (1984)

1. Floristic quality is explained in the introduction of Natural Areas Survey.

It will make a difference!
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[ Comments by Don B. -
{1}. In 1989 they were saying trees 90 years old, well it is 1999, they must be 100 !! ]

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