Tuesday, December 15, 2009

Autumn in Algonquin

Home, for me, is the Province of Ontario in eastern Canada (I was born in Toronto, and live now in nearby Mississauga). Those of us who hail from northeastern North America may not lay claim to the great wildlife spectacles of other regions (though we do have some dandies, including the spring bird migration at Ontario's Point Pelee), but we do have something shared with one other place on earth: the spectacular autumn spectacle of dying leaves blazing with reds, oranges and yellows before they shrivel and fall.

The reason why our fall colour show (and that of northeastern Asia) is so spectacular is that we share the greatest diversity of a single tree family, the maples (Aceraceae,now often lumped with the soapberries, horsechestnuts and buckeyes in the family Sapindaceae). While the leaves of many other temperate deciduous trees turn colour only because their chlorophyll disappears, revealing other pigments (such as the yellow carotenoids) that were hiding there all along, maples (and a few other plants, including sumacs and some oaks) actively synthesize new pigments, the anthocyanins, from sugar stored in the leaves, creating the rich reds, oranges and even purples that make our eastern forests blaze - especially in good years, when the trees produce higher sugar yields.

If you want to know more about the chemistry involved, there is a nice explanation here. Some very recent research suggests that anthocyanin production is actually, oddly enough, a defense mechanism against leaf-eating insects, and that this explains why Europe has less of an autumn show than we get in North America (see here if this sounds confusing). Alternatively, it has been proposed that anthocyanins act as a sort of sunscreen, protecting leaves so that they can stay on their trees (and manufacture more sugars) later into the season.

Maples are widespread across the northern hemisphere, but reach their peak of spcies diversity in eastern north America and eastern Asia. To demonstrate what I mean, consider that of the thirteen tree-sized maples on the continent only three occur widely in the west (mind you, even our eastern maple diversity pales beside the 60-odd species in China). Our most famous species, of course, is the sugar maple (Acer saccharum), one of the dominant trees of eastern forests, the bulwark of the maple sugar industry and the national symbol of Canada.

This is, I believe, mountain maple (Acer spicatum), one of the shrubbier species.

Here is a stand of white birch (Betula papyrifera) to show you how our autumn might look without maples (or anthocyanins): pretty, but pale....

Anyway, September 29, a dull and intermittently rainy day, found Eileen and I crossing east to west through the southern route of Algonquin Provincial Park, a long detour on our way home from Ottawa to Mississauga. I hadn't been to Algonquin for years, and Eileen had never been there at all, so it was something of a new experience for me and an entirely new one for my Malaysian wife.

As you can see, she enjoyed herself thoroughly!

We saw almost nothing in the way of animal life, but this impressive beaver lodge was a testament to the efforts of the species that, besides our own, has done the most to shape the Algonquin landscape.

Algonquin is beautiful any time of year - why has it taken me so long to get back here? - though it is not, I'm afraid, as pristine as it looks. According to the Wildliands League, only 22% of the park is actually protected from logging, though this is now to be increased to 35% under new action by the Ontario government.

Algonquin sits near the southern edge of the vast Canadian Shield, the largest expanse of exposed Precambrian rock on the planet; the roadside outcrop supporting this little maple tree may be a billion years old, or even two.

It also sits near the southern edge of the equally vast Canadian boreal forest, lying, strictly speaking, on the ecological boundary between the deciduous forests of the south and the coniferous forests to the north. The two worlds meet in this photograph.

Ferns add a delicate touch to the undergrowth; this looks rather like male fern (Dryopteris filix-mas) but I wouldn't bet on it...

If you look still lower, you can find lichens covering the rocks; I'll go out on a limb here and say, based on a quick perusal of the gorgeous book Lichens of North America by Irwin Brodo et al. (Yale University Press 2001), that this could be common goldspeck lichen (Candelariella vitellina). Corrections, please?

And here, nestled among leaves of red maple (Acer rubrum), is, I suspect, a clump of common antler lichen (Pseudevernia conoscians), fallen, like the leaves, from a tree - Brodo et al. say it grows on the trunks of conifers. They also say that this is the only Pseudevernia in North America with isidia, and they ought to know. Isidia, I gather, are very small bits of the top of the thallus (or body) of the lichen having to do with its complicated reproduction (since a lichen is a composite of a fungus and an alga living together, the two organisms have to reproduce in a way that disperses both partners as a unit - read all about it in Brodo, or here).

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