acid bogs: really insanely cool.

12 June 2008

If you’ve ever been to an acid bog and you didn’t think it was really insanely cool, you clearly don’t know enough about botany.

Acid bogs are formed when a type of moss called sphagnum (or peat moss) more or less invades asphagnum moss normal pond or lake. Sphagnum is special because, rather than just out-competing other species by getting the most it can out of its environment, it actually changes its environment to be less hospitable to other species. It does this through a process called cation exchange: in order to pick up its nutrients from the water it grows into, sphagnum pumps out one kind of ion, hydrogen, in order to take in the other ionic nutrients it needs (calcium, potassium, etc.). Hydrogen ions, as anyone who remembers basic chemistry should know, acidify water (the pH level is based on the concentration of hydrogen ions). A well established colony of sphagnum moss can generally lower the pH of its host lake to around 3.5.

This, of course, makes the bog rather inhospitable to normal plants, and whole new species have evolved just to fit into the ecosystem that sphagnum creates. One particularly cool adaptation is carnivory: plants like sundew and pitcher plants capture insects in order to obtain pitcher plantthe nutrients that are missing from their acidic habitat. (A cool counter-adaptation: pitcher plant moths have learned to cut holes in the bottoms of pitcher plants, draining out the digestive juices from the cup, and then settle in to raise their young in a nice, pre-made, edible house.) Other plants that thrive in acid bogs include members of the family Ericaceae, such as blueberries and cranberries.

I should probably mention at some point the structure of an acid bog, because that’s also cool. Generally, the sphagnum grows inward from the edges, swelling as it takes in up to twenty times its dry weight in water and forming a raised mat. At some point, this mat stops being directly connected to the bottom, and if you’re walking out onto the bog, you’re literally being held up only by floating sphagnum. (This is very fun to bounce around on — ever heard of a “quaking bog”? — but not so fun if you go through.) Plants are growing up out of the sphagnum mat, including larch trees, which thrive in acidic habitats, and a number of other specially adapted species, as I mentioned before. One particularly cool member of the Ericaceae, leatherleaf, grows at the very edge of the inner ring of open water and arches out into it, putting down roots and helping provide a structure for the continued building of the sphagnum mat. Eventually, the entire lake will be filled in.

One last thing about sphagnum before I go: it blows smoke rings. No, really. A smoke ring is a pattern called a vortex ring, which is what forms when air is blowing faster through the center of ansphagnum capsules area than through its outsides (bear with me here; physics is not my strong suit). Sphagnum disperses its spores in the exact same fashion. As the capsules that produce sphagnum’s spores (see photo) dry out, they squish down steadily until finally they pop, flinging bright orange spores into the air at 30 mph — which is fast, for a plant. And all this happens in less than a thirty thousandth of a second.

If you’ve got any more questions about sphagnum or acid bogs, don’t hesitate to ask — it’s been tough keeping myself even to this length of a post!

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