alvars & shrike hooligans

Posted on: August 25, 2009


a trip to the Carden Alvar in the morning was overseen by the Couchiching Conservancy, where kaira first brought us around the alvars and told us what they were. areas with very shallow soil over limestone rock, vegetation on this habitat is very specific and have special adaptations to deal with the drought and floods that come with the seasons, as well as the overall lack of rain/water.

granite deposited when glaciers retreated resulted in a mix of granite and limestone rock in the area, and this particular alvar is an ecotone and supports many plant and animal species (especially birds like the Nighthawk and Bobolink, which are species at risk in Canada). alvars have calcareous soil and are nutrient poor, and this results in low competition: which then allows for more species to move in in a bid for space. calcareous soil also is better for plants compared to acidic soil, so this type of habitat ends up having more biodiversity than ones with acidic soil.

so enough about the introduction of alvars, here it is:

DSC_0151 alvar picture #1

looks like man-made pavement? that’s exactly what i thought as i stepped into the area, walking from a graveled road to what i thought led to the most bio-diverse habitat in the temperate regions of this part of the world. lo and behold, it actually was limestone alvar that we were standing on, and one must remember that while the tropics are species diverse in every spot you look, temperate regions are different, and that’s still something to celebrate. i was still surprised though, but some of the rock in the area had fossils!

DSC_0182 fossils in alvar rock

in one square metre of land the alvars contain as a habitat comparatively more species than any other habitat in the temperate countries, containing lichen, mosses, woody vegetation and grasses, which in turn provide a suitable system for many insects, grassland bird species to nest, as well as snakes and other predators.

DSC_0153 alvar #2

you can see tall grasses and some woody vegetation here, and generally it looks like meadows and tall grasses. the alvars cannot support large trees (unless you leave succession to take over in many decades) easily, though Cedar tends to grow here. even though this particular alvar is largely undisturbed, humans have already introduced a couple of invasive species into the area.

to give you a bit more information about the Couchiching Conservancy, they work like the Nature Conservancy in that  they buy land (though funds from the federal and provincial government, as well as through donations/fundraising efforts) and then work on conservation through that. on top of that, the CC also works together with private landowners on managing their land effectively and in an environmentally friendly manner.

DSC_0155 Saxifraga virginiana [flower]

i could hear the distinct sound of crunching and crackling as i walked around the dry habitat, and looking down, one could see many plants amongst the twigs and dry grass. there is lichen (white in colour) at the top of this picture, moss in a dark green colour all around, and in the centre stands a succulent plant that is an indicator of alvars, and is also an arctic disjunct species that breaks up stone as they grow, and retain moisture in their succulent state. click on flower to see photos of their flowers.

DSC_0158 clumping effect – caespitose

plants in water deficient areas also tend to have an adaptation to ‘clump’ at the base to absorb and retain more moisture, and this can be seen in a number of plants in the area. plants that have this ability are called caespitose plants. pretty cool eh!

skullcap Skullcap

kaira also talked about indicators of alvar habitats, and these plants include the Skullcap (above) and the Field Chickweed (below). plants have what is known now as an ‘alvar association’ rank in percentage, and this tells you how much it is dependent on alvars for survival. plants like Fragrant Sumac and Bee Balm however, can live on alvars (though its tough to do so because of harsh conditions) but do not NEED to live on them. on the far extreme edge of the coin then also presents you with North Honeysuckle and Grey Dogweed that are unwanted species.

DSC_0181 Field Chickweed

DSC_0150 Butternut

thoughout our walk through the alvar landscape, kaira told us about how different plant species were at different levels of endangerment – special concern, threatened, endangered, expatriated, extinct – and giving us examples for some of them. one of them is the Butternut tree, seen above, whose attack by an invasive fungus brought in by numerous vectors (insects, water/wind) was bringing down its numbers and making it almost a matter of time before it would die out. sad! [comparable to dutch elm disease]

the other example she gave us was about the Red Mulberry, whose situation of limited numbers was brought about both by the introduction of a invasive introduced virus as well as hybridisation with the White Mulberry, of which hybrids are no longer Red Mulberries (which is how they are reducing their numbers).

DSC_0183 DSC_0197

and here we see two frogs! not sure what species they are, but this made us recall the various frog sounds Mary taught us the day before (see entry: fields) at Dufferin Marsh.


it was cool to see the alvars and get educated by them – i had never before heard of the term even before this!

so, two concepts for you:

1. the main threat to the alvars now are the lack of natural disturbances. knowing that grazing and nature fires used to be present but are now gone (as a result of human intervention), the woody vegetation is not being pushed back anymore, and these threaten to take over the alvar area (which is essentially open grassland) and through succession create an entire forest where alvar once was.

without natural small fires also means that tinder would have built up over the years and if a fire comes one day it would burn hotter and consume more land – eventually resulting in what happened to some other forests that suppressed fires: nearly two feet of burnt soil, barren land, seeds that would not generate because they died due to the too-hot-fires. extreme, but possible.

this would mean alvar habitat would be lost and species that depend on alvar habitats are gone – and the most bio-diverse area in the temperate regions are also lost. so now what would one do? introduce grazers? carry out prescribed, control fires?

2. when do you know if it is worthwhile to protect an area/species? do you necessarily have to choose areas to ‘sacrifice’ or ‘keep’? if an area is too small, or a species population is too small to sustain itself, would you invest money to sustain it by hand? what about fragmented areas – if, like the Dufferin Marsh, you know that the marsh was surrounded by urban sprawl and you know that it could not be expanded – is it worth putting in effort to sustain it?


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