Alvars are rare communities that occur on thin, discontinuous soil that lies overtop beds of limestone or dolomite. Of all the alvars in North America, almost 75 percent of these alvars are located in Ontario, while the remainder can be found in New York, Michigan, and Ohio.
Located northeast of Lake Simcoe, the Carden Alvar is an outstanding example of globally-threatened alvar habitat combining alvar grasslands, shrublands, forests and wetlands. This alvar plain is a perfect habitat for lichens, mosses, moulds and fungi. The groundwater system is poorly developed on the alvar so that most precipitation remains on the surface, subsequently evaporating and creating flood/drought conditions. Almost no soil development takes place directly on the limestone pavement, where storm winds routinely scour the rock surface. Consequently, plant establishment is generally limited to cracks, joints, and depressions in the bedrock, where small amounts of organic matter, cobble, and finer sediments accumulate.
Because it is formed from marine organisms, limestone bedrock is rich in calcium carbonates, resulting in a mildly alkaline soil pH. Resistance of the bedrock to erosion is variable. Both limestone and dolomite (dolostone) are readily dissolved by rainwater, producing solution depressions and cracks that often connect to the underlying groundwater system. However, limestone rich in mineral soil particles originating from terrestrial sources is resistant to solution and typically contains few cracks.
The Carden Alvar falls into the category of Open Alvar Grasslands and Pavements of which there are five different communities. These communities and characteristics are listed below.
Community Type
|
Soil Characteristics
|
| Tufted hairgrass wet alvar grassland |
shallow organic soil usually < 10 cm deep over flat limestone or dolostone bedrock, soils often are wet (saturated or flooded) during spring and fall, and very dry during midsummer |
| Little bluestem alvar grassland |
shallow loam usually <10 cm deep over limestone bedrock, seasonally flooded and usually very dry midsummer |
| Annual alvar pavement-grassland |
shallow loam usually < 10 cm deep over flat limestone or dolostone bedrock. Soils are saturated during spring and fall, very dry during midsummer, over winter needle-ice formation occurs turning over small blocks of soil |
| Alvar nonvascular pavement |
a very shallow layer < 2cm may be present under a mossy mat |
| Poverty grass dry alvar grassland |
shallow loam that is well drained over limestone or dolostone bedrock |
Logging Requirements: You will need to visit two locations a short distance from each other. At no time will you be required to cross the fence line or enter private property to determine your answers. If you park along side of the road, please be careful and make sure you are well off the road to allow traffic clear passage.
You will need to answer the following questions and send the answers to my profile. Found logs without the answers being sent within 5 days will be deleted.
1. Looking north just past the fence, can you see evidence of the limestone bedrock. Is the limestone mostly exposed, partially exposed or totally covered by soil?
2. Determine the composition of the soil. Pick up a marble sized hunk of moist soil and roll it between your thumb, middle finger and forefinger. You may need to add a little moisture so bring a small quantity of water. Be careful not to add too much water. Roll the soil around until if forms a small ball.
Determine the type of soil dominant on the Alvar based upon the following:
a) Clay soil will successfully bind to form a marble sized ball
b) Loam soil will show promise but will eventually fall apart
c) Sandy soil will fall apart and refuse to bind.
3. Determine your elevation in metres.
At the second reference point perform the same tasks and observations.
4. Is the soil type the same at both locations?
5. What was the difference in elevation between the two locations?
6. Was the soil covering deeper or thinner at the lower elevation?
7. Hypothesize why there would be a difference in the depth of the soil covering the alvar between the two locations.
8. Based on your observations and information gathered from the two locations, to what community type (or types if more then one) does the Carden Plain Alvar belong?
Optional: Include an image of yourself next to the Carden Plain sign.
Take a moment to check out the logbook for the bird sighting along the alvar located at the posted coordinate. Hope you enjoy this location and the many bird watching stations posted around the Carden Plain.
Note: This earthcache is not winter friendly in that you will be unable to answer the questions if there is more then a dusting of snow on the ground. In the spring and summer there appears to be poison ivy along the fence line so watch your step.
| This cache placed by an Earthcache Master - Platinum level: |
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