And I see your True Colours Shining Through

My favourite season tends to depend on my mood, but most often, my answer is autumn. It’s refreshing, a cool breeze washing away the heavy haze of summer. Paradoxically, it also feels warm, like shrugging into your favourite coat as you catch a whiff of someone’s wood stove in the crisp morning air.

I think it’s the colours of fall that give the days their warmth. The cool greens slowly fade into yellows, golds, russets and umbers. The forests are suddenly ablaze with a riot of hues.

In the boreal mixedwood forest where I live, the dominant colour is yellow. The poplars and birches sparkle with it against the sapphire September sky. Still, if you look closer to the ground, you can find a little more variety. The dogwoods (Corylus stolonifera) go purple, their leaves a lovely compliment to their reddish branches. The mountain maple (Acer spicatum), like the one pictured above, show quite a bit of variation, ranging from a pale yellow in individuals that are growing in the shade to brilliant orange and deep red for those lucky shrubs that are exposed to full sun.

But, where do these colours come from?

To a certain degree, they’re always there, hiding just below the surface, waiting for their curtain call. New, functioning leaves are full of chlorophyll, a brilliant green pigment that is packed into structures within the cell appropriately known as chloroplasts.  These are the food factories for the tree, working throughout the growing season to transform carbon dioxide and sunlight into nourishing sugars via photosynthesis that are then funnelled into the rest of the tree. During this period, chlorophyll is constantly being degraded and replaced, keeping the leaves a brilliant green, overshadowing any other colours lurking within.

However, as the days become shorter and the sun’s intensity begins to wane, these factories shut down, using up their last stores of chlorophyll until there’s nothing left. Once the green is gone, the veil is pulled back giving other the hues a chance to shine. Carotenoids, a pigment that also plays a role in photosynthesis, remains, painting the trees with bright yellows and oranges. Some leaves also contain pigments known as anthocyanins, a watery dye that stains leaves with intense washes of reds and purples.

Just how bright and varied the fall palette is depends a lot of the weather. Warm, sunny days, followed by cool, but not frosty nights gives the leaves a chance to build up a lot of sugars and trap them within their cells. High sugar levels often results in greater amounts of anthocyanin, yielding more reds and purples, adding to the variety in the forest.

This year’s fall in the north woods has been just the kind we need for a spectacular display and the trees have not disappointed. Every day for the last few weeks, I’ve watched in awe as more and more of the canopy sparkles with colour, filling in the autumn landscape, a spectacular display against the clear blue skies.

Still, all good things must come to an end. Eventually, the nights get too cold and the days too short, signalling to the tree that it’s time to lock down for winter. The veins bringing moisture to the leaves close up and the branches seal over, cutting off the leaf’s lifelife. The late October winds howling off the lake will tear the foliage from their bases, sending them fluttering to the forest floor and returning their nutrients back into the soil to feed next year’s crop. However, those days are a little ways away, and in the meantime I plan enjoy nature’s yearly blaze of glory for as long as I can.

Feed Me, Seymour

I have to admit that plants are not the first things that come to mind when I think of the word carnivore. However, after spending a morning mucking about in a peat bog last week, I was reminded that ‘meat-eaters’ can be found in pretty much any kingdom and  like their animal counterparts, carnivorous plants can be as beautiful as they are deadly.

In the boreal forests of Manitoba, pitcher plants (Sarracenia purpurea) are probably the most commonly encountered carnivorous plant. If you happen to stumble into the right habitat, they can be downright plentiful. We found dozens of them springing up from the carpet of sphagnum, looking like the bloodied tubes of an expansive green pipe organ.

These plants are truly a wonder of evolutionary design. The pitchers are modified leaves, curled in on themselves and fused to form a vessel that holds rainwater. The fluted edges are boldly pattered to be attractive to insects. However, what an unsuspecting bug doesn’t realize is those leaves are also covered in stiff, slippery downward-pointing hairs. When an insect lands on the rim, they immediately head for the mouth of the pitcher, in search of the nectar promised by the bold colours of the plant. However, the deeper they go, the more difficult it becomes to retreat. The hairs only go one way, drawing their quarry down into their watery doom. The ill-fated arthropod eventually drops into the water and ultimately drowns, its decomposing body providing much-needed nutrients for the plant.

But what would drive the evolution of such a set-up? Most plants are more than capable of feeding themselves, transforming carbon dioxide into energetic sugars through photosynthesis and drawing nutrients from the substrate they’re growing on. For pitcher plants, the big problem is finding enough nitrogen to grow and reproduce. Bogs are cold, acidic places and nitrogen is hard to come by. However, bogs have a lot of insects, flies, mosquitoes and all sorts of critters flitting about, their little nitrogen-filled bodies just there for the taking.

So plants, like pitcher plants and sundews have evolved a way to take advantage of the situation and as a result, thrive in an environment where many organisms could never get a footing and those that do only manage to barely eke out a living.

Although they may be hardy and can go where few vascular plants have gone before, pitcher plants are still vulnerable. Bogs are fragile ecosystems, often taking from decades to millennia to form. Forestry, oil and gas exploration, wetland draining and peat harvesting destroy these habitats, often permanently. The good news, however, is that in part because of just how hard most boreal wetlands are to get to, there are still over 100 million hectares of peat bogs and fens in Canada.

Most of us don’t realize just how important these regions are. These often bleak-looking stretches of greens and browns that wrap around the boreal belt can store on average 3.5 times more carbon per hectare than the forests that surround them. They also hold vast volumes of water, slowing run-off and filtering out pollutants from watersheds. Although Canada’s peatlands are still relatively intact, the world has already lost over 25% of these wetlands to agriculture and harvesting in a number of countries, releasing tonnes of CO2 into the atmosphere and changing water dynamics. It’s a slippery slope. We’re on the lip of the pitcher plant. If we as a species don’t pull back hard on the reins of our need for carbon and other natural resources, more of these valuable sinks will be lost and we will find ourselves tumbling down into our dark pool.

So, put on your boots and venture out into these wet and wonderful places. Admire the pitcher plants and other unique organisms that call this seemingly desolate place home and remember that just because something’s beautiful doesn’t mean it’s not dangerous and sometimes that which seems dull and ordinary is often extraordinary.

Double Rainbow All the Way

Double rainbow over Lake WinnipegThere’s just something about rainbows. They’ve been immortalized in endless songs, myths, stories, movies and even cellphone commercials based on the painfully hilarious mushroom-induced exaltations of an overly-enthusiastic youtube star.

Rainbows just capture the imagination. For the vikings of old, they were the Bifrost Bridge between Asgard, the home of the gods and our world of Midgard. In ancient Rome, they were the path of a messenger between Earth and the heavens and of course we all know they’re where leprechauns store their pots of gold.

But what are they really? Why can you never find the rainbow’s end? I think Kermit the Frog had it right when he labelled them ‘only illusions’.

Rainbows are the product of an observer standing in the right place at just the right time. What is that right place? It’s about 42 degrees from the direction opposite the sun. You can never get to the end of the rainbow because it will keep moving with you as you walk towards it. Stray off the bearing and the image will vanish into the mist.

What you’re seeing is sunlight being refracted, dispersed and reflected back at you through millions of water droplets suspended in the air. You usually only get enough water hanging around after a storm has passed, hence the name ‘rainbow’. Of course, if you’re standing next to a waterfall, fountain or someone’s sprinkler, you can often get the same effect if you’re in that magical optical sweet spot.

I’ll try and keep the physics simple, but here’s how it works. The white sunlight enters the water droplet and is dispersed into the full spectrum of colours. Then, it’s reflected off the back of the raindrop, just like the inside of a camera. On the way back out of the drop, each wavelength is refracted (their direction of travel is changed) as it passes from the water back out into the air.  How much each wave is refracted depends on the wavelength (colour) of the light. Red light (short wavelengths) are refracted less than blue (long wavelengths). The result is what was once a beam of ‘white’ light is now spread out into an arc of continuous colour. Double rainbows appear when the light is reflected off the back of the droplet lens twice. This second fan of light comes out at a slightly different angle and the spectrum of colour is inverted.

To us, the viewer, we see that colour in bands of red, orange, yellow, green, blue, indigo and violet because of the way photopigments in our eyes receive the light that is then interpreted by our brains. Take a black and white photo of a rainbow and you won’t see any bands, just a continuous gradation in intensity.  Animals whose brains can interpret wavelengths we can’t, like ultraviolet or infrared, would see a completely different rainbow than we do.

I think that’s what I find so fascinating about rainbows. Their beauty is truly in the eye of the beholder.