equation and elementary understanding of photosynthesis is important in grasping the larger picture.
Photosynthesis is the connection between the sun's energy and most of the biological systems on earth. Plants using the chlorophyll in their green tissues, trap the sun's energy. The energy is used to make simple sugars from carbon dioxide and water through a complex set of reactions. Oxygen is a by-product of the process.
The other part of the equation involves plant respiration.'Respiration' is commonly used to describe the macroscopic, physical of breathing in and out. In the study of plants biochemistry, the word refers to processes going on at the level of individual cells.
In this sense respiration is the breaking apart of the sugars to provide energy for growth and reproduction while releasing carbon dioxide. During the day plants take in both carbon dioxide and oxygen but give off more oxygen overall. At night, plants still take in carbon dioxide and oxygen but give off more carbon dioxide instead.
Seeing The Forest For The Trees
The boreal is an evergreen ecosystem. The most common trees are spruce, fir, larch and pine.
These are conifers or cone-bearing trees. Their needles are actually very narrow leaves which stay on the tree year-round. The needles do fall off after 3 to 7 years but only a few at a time. You'll also find poplars and birch which are deciduous, they lose their leaves in autumn.
Larch, also known as 'tamarack' is an exception to those loose rules. Tamaracks have cones but drop their needles in autumn. While rules sometimes help us understand things, nature doesn't always follow those rules.
Forests Communities
The boreal forest is a mosaic, like a patchwork quilt. The colours and textures are different types of forest. Here are just four out of the hundreds of vegetation communities which comprise the mosaic:Trembling Aspen, Black Spruce, Jack Pine, Fen / Bog
Trembling Aspen or White Poplar, Populus tremuloides, can be found its their own, but often combine with White Spruce and sometime Jack Pine and White Birch creating a mixed wood forest.
The a thin petioles of the aspen leaves connected at right angles to the leaves cause the foliage to move or 'tremble' in even light winds, hence the name Trembling Aspen. Aspen grow on soils which are moderately drained. Underneath the aspens tall shrubs such as beaked hazelnut or alder and understory vegetation like wild hairy rye, sarsaparilla, twinflower, bunchberry, cream-colored vetchling, dewberry and fireweed. As the aspen forest ages and the canopy closes, fireweed dies out.
Black Spruce, Picea mariana, often grows in harsh conditions. Soils may be frozen until midsummer and early frosts may shorten the growing season even more.
This tree is actually widely distributed. While thriving in wet sites, with its partially fire-opened cone, it invades dry or wet areas after fires.
The forest floor is covered with mosses like: feather moss, stair-step moss, fern moss and knight's plume. Wintergreen, Solomon's seal, bog cranberry,dwarf scouring rush bishop's cap, Labrador tea may be found.
Jack Pine, Pinus banksiana, can be found on rapidly drained soils. Water percolates through the large spaces into the soil.
The forest floor is carpeted in a lichen called Reindeer moss and others including blue-eyed grass, bearberry, early blue violet and alder.
If a seed source is available, a new stand of pine will regenerate following a forest fire. The Jack Pine is able to stand up to fires better then most trees because it has a thick corky bark and serotinous cones. The thick bark reduces the damage done to the tree from heat of the fire. Cones are 'serotinous'. Seeds are kept within the cone by a glue-like seal and under extreme heat the cones may slowly open and release the seeds.
Jack Pine is prone to dwarf mistletoe infestation. The mistletoe looks like a witch's broom . The tree's growth will be stunted or the tree may even be killed.
Fen landscapes are usually waterlogged and rich in organic matter. Tamarack or Larch, Larix laracina, and Black Spruce may grow in or around such sites.
At the southern edge of the boreal forest permafrost is associated only with this type of landform. The thick layer of dead organic matter or 'peat' along with an a covering of sphagnum moss mean that frost may persist year-round. Further north, the extent of permafrost becomes much greater.
Dwarf birch, swamp birch, willows and Labrador tea are common. The ground is covered with Sphagnum and feather moss, small bog cranberry, water sedges, and Northern reed grasses. Just below the surface, the fen may remain frozen until late June, so these plants must be able to survive the cold, wet conditions.
Tamaracks can withstand high water levels for short periods of time, but if the duration of flooding is extensive many trees may die.
For a complete, referenced version of the above article contact bmuir@sundogs.sk.ca
Boreal Forest & Winter Ecology Reading Suggestions
We can also suggest writings on other specific boreal forest topics or species or dog sledding.
Cary, Bob Gail de Marcken, 1999 Born To Pull, Pfeifer- Hamilton Press
Frith, S. 1997 Prince Albert National Park Trail Guide, Friends of Prince Albert National Park
Gawthrop, David 1999 Vanishing Halo - Saving The Boreal Forest
Henry, J. David 2002 Canada's Boreal Forest
Halfpenny, James C. , Roy Douglas Ozanne, Elizabeth Biesiot 1995 Winter : An Ecological Handbook
Hammond, Herb 1991 Seeing The Forest Among The Trees, Polestar Press
Johnson, D. L, Kershaw, A. MacKinnon, J. Pojar 1995 Plants of the Western Boreal Forest, Lone Pine Publ.
Lynch, Wayne 2001 The Great Northern Kingdom - Life In The Boreal Forest
Marchand, Peter 1996 Life In The Cold, University of New England Press
Pielou, E.C. 1988 The World of Northern Evergreens, Cornell Comstock
Pielou, E.C. 1991 After The Ice Age, University of Chicago Press
Pruitt, W.O. Jr. 1983 Wild Harmony - The Cycle of Life in the Northern Forest, Western Producer Prairie Books/Douglas & McIntyre
Pruitt, W.O. Jr. 1978 Boreal Ecology, Edward Arnold Publ.
Runyan, Joe. 1997 Winning Strategies For Distance Mushers, Runyan Publ.
