Exploring Black Spruce Bog
The sphagnum moss-matted surface looked solid enough.
But when Bill Moorhead pushed his soil core sampler probe through that moss, it cut through and dropped through it to its handle in sodden peat.
Moorhead — a botanist and ecologist with the state Department of Energy
and Environmental Protection — was exploring the world along the boardwalk at the 19-acre Black Spruce Bog at Mohawk State Forest in Cornwall.
It’s one of the few bogs in the state, with a unique collection of fauna that grows only in such a high-acid environment.
The peat, compacted there over centuries, runs some 40 feet deep and is thousands of years old. Instead of hardwoods, it’s got wildflowers like golden thread and wild sarsaparilla, and trees like black spruce and larch.
It’s something completely different.
“It could be called a larch bog as much as a black spruce big,” said Moorhead, whose job includes collecting field data for the state’s Natural Diversity Wildlife Data Base.
Along with David Irvin, a DEEP forester whose territory includes the 3,300-acre Mohawk State Forest, Moorhead gave a guided tour of the bog last week.
It’s not a true bog — a place that depends only on rain and melting snow for its water.
Because some groundwater seeps into the Black Spruce site from its bedrock foundation, it is more properly called a poor fen, Moorhead said. There are also medium fens and rich fens, depending how much water and nutrients feed into the place.
Moorhead said there are only about 30 such boggy fens in the state. Run-off from development has degraded some of these places. Land trusts have protected others, like the Nature Conservancy’s Beekley Bog in Norfolk.
There are bogs that over time have become swamps as well, Moorhead said.
The Black Spruce Bog gets its protection by being surrounded by the Mohawk State Forest.
It got its origins when the glaciers retreated at the end of the last Ice Age, about 14,000 years ago.
Those retreating glaciers gouged out a depression in the bedrock at Mohawk Mountain and left a huge chunk of ice behind.
When such big ice chunks melt and connect with underground springs, they create what are called kettle ponds. But at the Black Spruce Bog, the melting water from the ice stayed in its bowl, with nothing but bedrock underneath, with no stream to replenish it and a only small watershed to feed it.
Over thousands of years vegetation grew up around the spot and falling leaves settled into the water.
Ordinarily, a mix of oxygen and microbial life breaks down that leaf matter, releasing carbon dioxide. But, Moorhead said, bogs are special places that are low in oxygen and nutrients — calcium, nitrogen, potassium and phosphorus.
Plant matter in such places accumulates faster than it decays. Over time, the bowl fills up with peat — partially decayed vegetation.
“It’s all because of its geology,” Moorhead said.
Bogs are high-acid environments. The plants that thrive in them have evolved to live there.
The two dominant trees in the bog — black spruce and larch — aren’t common in the rest of the state.
There’s also sedges — grass-like plants that aren’t true grasses — liverwort and cinnamon ferns. There is also the carpet of different species of sphagnum moss that carpets the bog. (The boardwalk that laces through the bog protects those species from heavy, ruinous human tread.)
At one time, there were also sundew and pitcher plants at the bog — plants that snare insects and feed on them. But Moorhead said that over time, as other vegetation has grown up at the bog, it’s overshadowed the sunny spots that those artful carnivores need. They’re hard to find now, he said
But there are plenty of heath plants — high-bush blueberry, black huckleberry, mountain laurel and sheep laurel (aka lambkill and calfkill, because it’s toxic to any livestock grazing on it.)
Moorhead said there is also a trio of plants at the Black Spruce Bog — mountain holly, smooth holly and viburnum — that seem to mark a place as a bog.
The Black Spruce Bog is changing, slowly over time. Moorhead said that if climate change makes the state wetter, the increased precipitation might change it as well.
Every bog is a one of a kind. Plants adapted to high-acid environments don’t thrive elsewhere. And bogs in different locations have different ecologies, with a different set of plants.
“It’s island biology,’’ Moorhead said.