Age Class Distribution Management

A forest’s age is calculated by the number of trees in each age class in a specific area, called a stand. As most forests have trees of different ages, the age of the stand is determined based on the age of the dominant trees. Forests in many areas of Canada have become younger over time because of harvesting and natural disturbances such as fire, insects, and wind damage. Some forests have grown older because of fire suppression.

As different tree species live longer and grow at different rates, what is considered a mature forest differs from species to species. An uneven-aged stand is a group of trees that differ significantly in ages.

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In addition to age, forests are also unmanaged and managed. Managed forests have been harvested, replanted and will be harvested again. Historically, and still today in many countries, managed forests have less biodiversity because usually one species of tree is planted—limiting the diversity of plants and animals that will also live in it. In Canada, a leader in forest management, timber industries replant based on the dominant species harvested. In some stands, more than one species is replanted. The silvics of the replanted species are considered. Silvics refers to the study of silviculture and what will grow best under the given conditions. A managed boreal forest is usually harvested every 70 to 100 years.

Unmanaged, or primary forests have not been harvested. As these trees grow bigger and biomass increases, the forests become more complex and biodiverse. For example, there may be more coarse woody debris, snags and fallen trees; more diversity in tree size, plant, and animal species. A forest is at its “peak” when it is the most biodiverse. Sometimes, an old-growth forest is the most biodiverse it will ever be. Other old-growth forests are made up of pyroclimactic tree species. For example, lodgepole pine are Alberta’s old-growth species. In an old-growth lodgepole pine forest there is little variance in age, and fire (or harvesting) will remove the stand entirely. As First Nations people were well aware, old-growth forests may have had more diversity, but they held little to no big game. Old-growth forests vary in age depending on the primary species; they are usually over 120 years old.
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Click each collapsible row to view more information.


Courtesy of Natural Resources Canada, https://www.nrcan.gc.ca.


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Prior to colonization, the First Nations peoples had little impact on the forests because of small population sizes and cultural beliefs. Eastern Canada went through a heavy period of deforestation in the 18th and 19th centuries because of the large number of settlers who cleared the land settlement, agricultural use, ship building, and resources. Today, Canada is working hard to protect and manage its mature forests. In general, Canada’s broadleaf and mixed wood forests tend to be younger—and the oldest forests are almost entirely coniferous boreal forests—which make up 77% of Canada’s forests. With over half of Canada’s forests having a stand age of over 80 years, we can see that much of Canada’s boreal forests have kept their structural integrity and biodiversity. Canada's oldest forests are located in wetter areas where the climate prevents forest fires. Some of these trees are over 1500 years old.


The Maritimes, Quebec, and Ontario old growth forests are made up of red spruce, while eastern hemlock, eastern white pine, eastern white cedar, yellow birch and sugar maple trees.
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Iconic old growth forests of British Columbia are made up of the Douglas fir, Sitka spruce, and western red cedar.
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To learn more about Canada’s Always Changing Boreal Forest, view this PDF.

We already know that in the past, forests were a resource, and not much thought was put into their management. Research and historical data show that population and technology growth increases deforestation. For example, 2000 years ago, forests covered about 80% of Europe. Today, with the exception of Russia, they cover about 35%. These forests were first harvested for building and heating materials, and then were unable to grow back because of agriculture and urban development. The demand increased as lumber was needed for ship building during the age of exploration, foundries, and smelters in the early Industrial Revolution. Thus, in Europe, there are very few old forests remaining. This trend can be seen throughout the world, both historically and in modern times.
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Forest cover was reduced substantially in Europe to meet demands of population growth.
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Forest Facts

Forestry evolved as the science and practice of managing forests and trees grew. By the 18th century, the deforestation of Europe was viewed as a crisis. The teaching of forestry as an applied science spread through universities in France and Germany. Systematic reforestation programmes were started in both countries.


There is concern that more demand for forest products will increase logging activities in mature forests in Canada and around the world. From the perspective of timber production, older forests are less productive than young forests because growth rates slow as trees age and timber volumes decline as trees decay. Many old-growth forests are now in protected areas and are tourist attractions.


Ancient beech forest in Germany’s Jasmund National Park — A UNESCO World Heritage Site. Some trees are over 700 years old.
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