Tuesday, July 19, 2011

The Stoco Fen

The Stoco Fen is a law unto itself, a singular habitat supporting some distinctive species that can't be found in other local wetlands though they are situated as little as a few hundred meters down the road. The difference is apparent even at a distance; whereas other local marshes sustain cattails, alders and willows, the fen's graminoids tend to be lower growing species and the prevalent shrubs are white cedar and tamarack.

Two of our smallest dragonflies inhabit the fen. North America's tiniest, the Elfin Skimmer (Nannothemis bella), was still flying on July 27th.

Our other diminutive dragonfly is the Eastern Amberwing (Perithemis tenera). With the humidex factored in the temperature was in the low 40's and this female was obelisking to in an effort to regulate her body temperature. By pointing its abdomen and wings toward the sun the insect reduces the amount of surface area exposed to radiation.

Although common at other locales near Tweed, our largest butterfly, the Giant Swallowtail (Papilio cresphontes), is likely breeding at or near the fen. Several individuals were encountered during this brief visit and their bright colors and lack of wear and tear on their wings indicates that they have just recently emerged from their chrysalides.

A closer examination the flora reveals how different the Stoco Fen is from other more typical local wetlands. Two representatives of the Heath family (Ericaceae) are resident here. Bog Labrador Tea (Rhododendron groenlandicum) can be identified by its leaves, with their rolled under edges and brown undersides.

The alternately arranged leaves of Bog Rosemary (Andromeda polifolia) distinguish it from Bog Laurel, which has opposite leaves. The flowers and fruits of these two plants are also quite different (it was too late in the season to get photos of the flowers ... next year).

This is the first (and to date only) site that I've found the Sticky False Asphodel (Tofieldia glutinosa). Named for the sticky, rough feel of its stem this small lily is a wetlands indicator species.

Since three of our four species of Lady's Slipper are denizens of the Stoco Fen it's reasonable to expect other orchid species in this habitat. My copy of Wetland Plants of Ontario calls this orchid a Swamp Pink but the more commonly accepted name seems to be Grass Pink (Calopogon tuberosus). Unlike other orchids, the specially modified lip is at the top of the flower rather than the bottom.

The delicately tinted little orchid in the next two photos is a Rose Pogonia (Pogonia ophioglossoides).

It appears that I've reached an impasse in my efforts to research the reasons the Stoco Fen so different from neighboring environments. Members of the heath family such as Bog Labrador Tea and Bog Rosemary, and orchids such as the Grass Pink and Rose Pogonia, tend to prefer acidic soil conditions. On the other hand, according to the sources I've found on the Internet, the Small White Lady's Slipper, one of the fen's species of interest, favours rich, highly calcerous soils.

There's good reason to think that the soil in the fen is anything but rich. In addition to the ubiquitous Pitcher Plants there are other plant species growing in the fen that find it necessary to supplement their nutrient intake by capturing and digesting insects, for example, the Flat-leaved Bladderwort (Utricularia intermedia). Of course, a plant that grows in water-filled roadside ditches isn't necessarily the best indicator species of soil conditions in general.

A closeup shot of the submerged bladders and leaves.

Due to its small size at first I completely missed this Round-leaved Sundew (Drosera rotundifolia). The tiny white blossom, on the end of a stem little thicker than heavy thread, is only a few millimeters in diameter. Luckily I had a friend with me who made up for my oversight and pointed out the location of the flower he'd just photographed ...

The leaves are arranged in a basal rosette, a bit difficult to see as they are hidden amongst other vegetation in this photo. (The "other vegetation" looks like it might be Grass of Parnassus ... time will tell.)

With a liking for acidic, low nutrient soils the Round-leaved Sundew is another of the plant kingdom's meat eaters. The hairs on the leaves are coated with sticky droplets that attract insects. The leaf eventually curls around the adhered insect and produces enzymes that extract the nutrients from its body.