A
pungent, earthy, vibrant aroma seemed to squirt out of the bog with every sinking
footstep. Even through the soles of my muck boots I could enjoy the varying
textures of this living carpet. Soggy sphagnum moss offered almost no
resistance, while the skeletons of tough twigs buried within the moss crackled,
bent, and snapped. At some point in each footfall, the cushion of living and
dead plants pushed back toward me just enough so that I didn’t fall through.
Bogs
are a unique, almost alien landscape, with a charm all their own. Funny plants,
few trees, and a wonderful, squelchy, squashy, shaky, shivery, sucking
substrate can turn adults back into giggly, wiggly kids. These twenty-two
Wisconsin Master Naturalist Volunteer trainees were no different as they spread
out to explore the Secret Bog.
Squatting
down next to a domed hummock, I peered into a miniature jungle. Delicate vines
of bog cranberry – with bright pink, swept-back petals on their tiny flowers;
the wiry lattice of leatherleaf twigs; and bog laurel’s leaning stems with deep
green leaves all poked their heads out of the mat of sphagnum moss like
drowning rats. Sphagnum moss may be the bog’s bully – pulling itself up on the
stems of others, using woody plants like scaffolding – but it is also the
reason that the bog is here.
Sphagnum’s
primitive leaves are like tiny sponges, and can absorb up to 26 times their own
weight in water. This can raise the water table. Such a saturated environment
is low in the oxygen that microbes need to accomplish decomposition, so
nutrients stay locked up in dead vegetation. To deal with the lack of available
minerals, sphagnum shoots hydrogen ions into its environment, dislodging scarce
nutrients for its own use. This acidifies the bog, which further limits what
plants can grow there.
Life
is not easily discouraged, though, and a special suite of plants thrives in
sphagnum’s world.
Peering
over the side of the hummock, a sparkle caught my eye. Looking closer, I
discovered a cluster of bright pink, hairy spoons, only an inch or two high.
“Sundew!” I squealed, pulling over the nearest student naturalist to exclaim
about it with me.
Round-leaf
sundew are beautiful little plants, with a circumboreal distribution (around
the Northern Hemisphere), and a penchant for animal flesh. Well, a taste for
insects and spiders at least.
Sundews
love the sunny, moist habitat created by sphagnum, but they still need to eat.
Nitrogen is a limiting nutrient in bogs. Some plants get their nitrogen through
complex root systems and relationships with fungi, while others conserve it
with the austerity of evergreen leaves. Sundews catch bugs.
The
sparkle that caught my eye was actually a drop of “dew” clinging to the tip of
a tiny tentacle. The bowls of sundew’s spoon-shaped leaves are dotted with these
tentacles. Long ones hold a drop of sweet, sticky nectar that attracts and
entraps prey. Once an unsuspecting insect has been mired in this mucilage, the
leaf curls inward. This response to touch is known by the comical term:
thigmonasty. From the bug’s perspective: thing most nasty.
Death
usually occurs within 15 minutes, as the prey succumbs to exhaustion or is
suffocated by the goo. Shorter tentacles, with drops of digestive enzymes at their
tips, make contact with the prey and reduce it to nutrient-rich soup, which is
absorbed through the leaf surfaces. The valuable nitrogen is use to make
chlorophyll, enzymes, proteins, and seeds.
The
seeds are produced in a delicate, white-petaled flower held aloft on a long
stalk. But how, might you ask, does the insectivorous sundew avoid eating its own
would-be pollinators? In nature’s wisdom, a completely different set of bugs is
attracted to the flower from those who are lured in by the saccharine dew.
The
group of students was lured in, too, a few at a time, to look at the impressive
patch of sparkling leaves. As we headed back to solid ground for our closing
discussion, I plucked a little cluster of sundew leaves to bring in for a
closer look. At first I was annoyed when the tentacles stuck stubbornly to my
finger. Then I chuckled at my own surprise. It seems that Master Naturalists
are no more immune than bugs to the cloying charms of sundew.