SpruceRoots Magazine - February 2002
SpruceRoots Magazine - April 2003
THE SECRET LIFE OF SNAGS
|by Erica Thompson
The Blue Grouse looks around after a ruffle in the red mound. The moments following a bath are the most vulnerable of times. As he scuttles for cover his long squarish tail sweeps against the crumbling stump, whisking wood dust up under his blue grey belly. The irony of finding fleeting relief from parasites in the remains of a five hundred-year-old hemlock is no affair of the grouses.
The reddish brown stump is a pyre of mathematical remainders, an arrangement of cubes and columns, more like quartz or basalt than wood. The tree is gone but for the lignin which once cemented its woody chains of sugar together. There are fewer fungi able to digest the chemicals, which grant a tree its architecture.
This forest and this stump have not always been this way. At one time, the hemlock soared over one hundred feet towards the sky, sound and windfirm, able to bear the loads of many Novembers and negotiate the best that southeast gales had to offer.
Centuries ago a great wind charged down the ridge, whipping a spruce tree's crown to the ground. With the tree fell its shadow. The sky opens over the young hemlock and sunlight falls. Beyond the boundaries of bark, water begins to move upwards, soils dissolve into nutrients and the ocean arrives nearly weightless with its own contributions. For undisturbed centuries, the tree grows. Its roots stretch out in an intricate tangle of support, travelling underground, embedding rock in root. Above ground, sword ferns sip fog drip, bryophitic carpets cloak and the hemlock grows from the inside out. It's channelized bark seasoning to the deepest of browns.
As the hemlock matures, it begins to support far more life than merely its own. The bark is masked with lichens all stratums of greens. Pendulous Wing moss evolves into luxurious mats and murrelets nest in the branches of the canopy. They turn their backs on the sea at mornings' light, flying with fish in their beaks, inland to the hemlock feeding their young nesting on the protected platforms. The luminescent epiphytes growing from the old crown transmit, out across the valley, a rare and enduring blue. The colour a beacon of diversity and time.
Late one summer, a pale green seed rides an updraft and collides with the crown branches of the hemlock. The dwarf mistletoe seed is sticky with resin and holds tight to the branch between woody and waxy needle. The coming rain moistens the resin, cementing the seed in place.
Soon, a Black-capped chickadee settles down beside the sticky sweet seed. She rubs her beak against the branch, her black head plucking up and down as she tries to dislodge the fruit. The bark of the small twig tears, revealing the pale wood below. A small beak, a minute wound, bearing such consequences.
The next summer, the bark where the Chickadee pecked for the sweet seed breaks open, peeling back under an invisible pressure. Another season passes before small aerial shoots emerge from the site where the seed settled. Mistletoe blossoms from a spindle shaped swelling. After an uncommon amount of sunshine falls on the hemlock's upper branches, the next July, the dwarf mistletoe flowers for the first time. On the forest floor, a Red squirrel scuttles around, gathering purple seed cones in preparation for winter.
The perennial mistletoe continues to flourish and new infections begin bearing fruit of their own. The hemlock's infected twigs and branches begin swelling and enlarging in size. In the next half century, successive crops of mistletoe sprout from new branches disrupting the hemlock's own chemistry by diverting nutrients to the swellings. Twigs and branches begin growing in abundance where mistletoe infections take root and these unbalanced bursts of energy take on the ragged appearance of witches' brooms, so straggly compared to the elegant healthy green branches. Over the years, the infection spreads until the majority of upper branches hang low and tattered. The sickly crown begins to lean to the east, weighted down by the life it supports. Pale green seeds fall onto lower branches and new swellings appear. In December a gale shrieks down the valley sweeping the scraggly crown clean off.
A large scar rips down the centre of the trunk, cracked by the force of the splintering crown. The bark is torn back and the sapwood revealed. Before long, the wound begins to silver and Red Belt fungi claims the tree for its own. The fungus takes hold and its slow mission of decay begins in the long chains of sugar molecules that make up the nutrient rich sapwood. A Red squirrel clamours up the trunk and settles in on one of the lichen mats to eat. The woody tissue swelling out of the mistletoe is sweet and nutritious.
After a decade, a leathery conk appears where a branch fettered by witch's broom fell from the trunk. Inside the tree, heart rot begins to spread from the cracked crown throughout the trunk. The hemlock is dying from the inside out. Its heartwood is softening from the efforts of microscopic invaders. It is becoming populated.
Bare patches appear on the trunk where the bark is loosening away from the underlying cambium and needles are taking on the bronzy brown colour of decline. The upper branches are mostly gone, weakened by the witches brooms and finished by the winds, though the largest upper limb is broken to a silvering stub. The wood is mostly still hard but the rot is moving further into the sapwood creating spongy pockets.
Come spring a red capped Hairy woodpecker lands feet first on the trunk. Battening down, the surrounding forest fills with frantic drumming. The sounds of territorial claim and courtship are translated from beak to bark. The woodpecker excavates a series of exploratory holes through bark and sapwood. The woodpecker's hearing is acute allowing it to create audible maps of feeding opportunities that lay just under bark.
Bare patches appear on the trunk where the bark is loosening away from the underlying cambium and needles are taking on the bronzy brown colour of decline. The upper branches are mostly gone, weakened by the witches broom and finished by the winds, though the largest upper limb is broken to a silvering stub. The wood is mostly still hard but the rot is moving further into the sapwood creating spongy pockets.
Carpenter ants, millipedes and wood boring beetles are moving about within the tree, carving their intricate galleries and breeding chambers. Their whereabouts if the business of the Hairy woodpecker. Movement, however miniscule does not escape the this excavator. Its chisel-tipped beak mines the intricate sapwood galleries and the barbed tipped tongue snaps beetle larvae out through the rough-hewn notches. For weeks, the woodpecker carves out oval shaped cavities in the hemlock where it, its mate and offspring will feed, nest and roost for the next season. It is not until late summer that the nearly fully-grown chicks fledge.
The hemlock's needles begin falling quickly, littering the ground. Two large branches drop that winter and the mistletoe continues to spread. It has been many years since the murrelets have returned and their whereabouts is not evident. Another Black-capped chickadee takes refuge in one of the cavities abandoned by the wood-peckers. The Chickadee zips about gleaning budworms, beetles and all weevils from the remaining needles. A Nut-hatch begins to build a nest in a broken branch hole just below the breakage point.
Come winter, Keene's Long Eared Myotis bats roost under some of the last sheets of sloughing bark protected from wind and coldness on the upper bole. The decline of the hemlock does not limit the species dependent upon it.
There was little damage through winter and the hemlock did not fare badly against the gales. Red-breasted sapsuckers arrive in the spring, drilling pits in the remaining sapwood searching out food and shelter. A Black bear leaves deep scars where she ran her claws down the trunk signing her territory. The fledgling sapsuckers are loud, begging and begging for food from their cavities.
A Northern goshawk radars in on the sounds of the begging sapsuckers, making a sharp break in flight to perch on the broken branch at the top of the tree. From the silvering top limb, the goshawk hunts and succeeds. Flying back up to the perch, the raptor plucks the sapsuckers feathers from its body. Feathers rain down from the treetop. Feather piles, and whitish grey pellets the compact regurgitated remains of Stellar jays, Blue grouse, Red squirrel and Red breasted sapsuckers appear under the tree. Whitewash hits the snag.
Throughout the last sap and heart wood, the intricate galleries of the wood boring insects are choked with soil and frass, the fecal matter of micro carvers.
Chattering nuthatches take refuge within their hammock nests coveted under a sheet of the loose bark and the gravity defying feats of Brown creepers announce spring. These small cavity nesters glean the wood-peckered bark finding beetle larvae.
During the winter months, the hemlock lost three more branches to the southeast winds. There is little bark left. The tree is quite unrecognizable now. The glory of its former strength now lay in red brown dust, which cyclones out of a crack at the base of the tree in a good wind. Deer mice hide in small holes in the roots. During the fall, a Black bear sniffes about the rotten trunk, eventually settling into a winter den.
Over time, mushrooms emerge from the rotting woodsurface signals of a microscopic world of fungal threads and bacteria. Some say there may be as many as 10,000 different species of bacteria in a handful of soil.
Golden chanterelles bloom in autumn emitting apricot scents between the hemlock and spruce. The broken crown lays all sponge and moss. Fungus and insects have eaten pockets out of the wood, minute reservoirs of captured rains. A small hemlock sprouts from the ancient top, where the Black-capped chickadee once dropped a seed. In the absence of the standing hemlock, sunlight falls on the seedling, encouraging a legacy and then nearby, a Blue grouse scratches in the dust for needles and seeds. It seems like a safe time to take care of those ticks.
|SNAGS ARE CRITICAL COMPONENTS OF FOREST ECO-SYSTEMS.
In British Columbia over 90 wildlife species, or approximately 16% of the province's native birds and mammals, depend on wildlife trees for nesting, food or shelter, according to A Closer Look at Wildlife Trees by C. Steeger, J. Krebs and D. Crampton.
Snags are places with high levels of activity. Cavity nesting birds, like woodpeckers, chickadees, and small owls such as the blue-listed Queen Charlotte Northern Sawhet owl depend upon snags. Open platform nesters, such as Bald eagles and Great Blue herons build their nests in the dead tops and broken upper limbs of snags. The endangered Marbled murrelet nests in epiphyte platforms and red-listed Keene's Long Eared Myotis bats under shaggy bark. Mammals, such as the Queen Charlotte Black bear over-winter in dens located in hollowed snags. Wildlife use snags as agents in communication, territorial markings and courtship display rituals.
The foundations for evolving forests are generated in part by snags; an evolution of a self-sustaining system. Fallen snags and large limbs form nurse logs and the woody remains scattered about the last impressions of stumps provide material and nutrients for new seedlings.