Dying forest survives by crossing Mud Lake
Naturalist unearths strange case of migration by white pines
The face of nature in our city has changed over the past 50 years, just as our streets and buildings have. But few changes in nature are as bizarre as the Britannia pine forest that crossed a lake.
Ottawa naturalist Dan Brunton has been visiting the forest around Mud Lake since the mid-1960s. It is an ecological hot spot, whose combination of different soils, along with the Ottawa River and the small, warm lake, sustain some 640 types of plants and more than 100 birds.
Brunton recently compared photos taken in 1968 to the forest today. What he found was a striking change that almost no one had noticed.
The 1960s were years of change for the forest, pushed by wellintentioned efforts to slow the spread of Dutch elm disease by cutting many trees.
“But — and this is the important lesson I learned — the pine forest endured, as natural forests so often do, if given half a chance,” Brunton writes in a study in the Canadian Field-Naturalist journal. “They (pines) continued to stand tall as they had done for many decades since rising from the ashes of a 19th century fire. … At heights of over 100 feet (30 metres), the largest of these are among the tallest trees in Ottawa.”
Great horned owls nested near the top of one such tree.
But there are almost no saplings in this old pine forest. White pines reproduce best in ground cleared by forest fire, he notes, and fires have been suppressed in the city for years.
There are plenty of seeds falling, “but these rarely sprout in the dry, litter-covered ground below. All this available seed makes for fat rodents and occasionally satisfied winter finches but produces no forest renewal.”
Now the pines are showing their age. Each year a few of the forest giants die, with no young trees coming up beside them. The ice storm of 1998 killed many “and the rate of loss seems to be increasing,” he reports. There are now gaps in the canopy, which once was solid green. The new trees growing up are maples.
“It is clear that the Britannia pine grove is dying. And it is doing so at an accelerating rate,” Brunton found.
But then he found something to remind us of “the remarkable resilience of natural environments, even those we have meddled with significantly. The Britannia pine grove is migrating eastward, across Mud Lake.”
The eastern shore was once cow pasture, he reminds us. It became a scrubby area of thickets of invasive honeysuckle and buckthorn, but it hasn’t stayed that way.
High west winds have blown seeds from the white pines on the lake’s west side. Many landed in Mud Lake, but enough have crossed the lake to reach the eastern shore.
“Sprouting is much easier there in the sandy, largely litter-free soil of the glades and gaps” in the thicket areas, and “by the mid-1990s white pine seedlings had become commonly established.
“This seedling invasion was a low-key development, unfolding under our noses and apparently largely beyond our awareness,” he says.
It was only with the construction of a new walking trail past the area in 2002 that naturalists realized they had a narrow, but dense and very robust, band of healthy young white pines.
“In late 2014 one glade was found to have over 60 seedlings, each less than one metre tall. Tomorrow’s forest,” he writes.
This seedling invasion was a low-key development, unfolding under our noses and apparently largely beyond our awareness.