Old growth forests - part 1of 2

by Steve Blight

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Over the past decade or so, the term “old-growth forests” has steadily crept into the vocabulary of land managers, nature lovers and the media. This column will explore some of the benefits and features of old growth forests, and my next column will look at actions landowners can take to help create old growth conditions on their properties. Both of these columns draw heavily on two excellent extension notes on old growth forests available from the LandOwner Resource Centre in Manotick, or online at http://www.lrconline.com/EN_splash.html.

Forest professionals have spent a lot of time trying to figure out how to define old growth forests, and this debate is likely to continue for some time. However, there is quite a bit of agreement on why old growth forests are an important part of Ontario’s landscape. Typically they contain a wide variety of trees and shrubs and provide habitat for wildlife species that prefer older forests with big trees, including birds like the Cerulean Warbler and the Red-Shouldered Hawk. Old-growth forests also allow for genetic variation between members of the same species. This variation gives a species a greater chance of adapting to and surviving problems such as outbreaks of insects like gypsy moths, diseases like the butternut canker or environmental changes like pollution and global warming.

In addition, many people find large unbroken tracts of forest with large trees visually appealing and even spiritually rewarding.

Here are some characteristic features of old growth forests:

• Many old, large diameter trees. A very rough rule of thumb says that an old Sugar Maple would be one with a diameter of about 50 centimetres (20 inches) at breast height and which may be about 150 years old.

• Supercanopy trees. These are usually tall white pines that poke through the canopy, providing landmarks, nesting sites and resting places for birds as well as refuges for bear cubs escaping predators.

• Mature canopy trees forming a mostly continuous ceiling that shades the layers of the forest below.

• Small trees, saplings and shrubs of various species growing beneath the canopy, whose growth is limited by the lack of sunlight.

• Large decaying trees and branches on the ground. Together with old leaves and small branches, this coarse woody debris absorbs moisture and provides habitat for reptiles, amphibians as well as fungi and a variety of other decomposers that return nutrients to the forest soil.

• A rich ground cover, including mosses, fungi, flowers, ferns and tree seedlings forming a living layer on the forest floor.

• Pits and mounds. These are features that are formed when large trees are uprooted, for example by high winds. The pits form when the roots and clinging soil are pulled from the ground. The mounds form as the roots decay. Together, the pits and the mounds provide a great diversity of drier and wetter habitats.

• Snags and cavity trees. Snags are standing dead trees that are used by species like Great-crested Flycatchers and bats as important parts of their habitat. Cavity trees are living or dead trees with holes that animals like flying squirrels and owls use for nesting, denning and escaping. These cavities are often excavated by Pileated Woodpeckers or created by decay and broken branches.

This column has identified some of the features of old growth forests. In my next column we will look at things we can do on our own properties to restore some of these features to the forests of the Land O’Lakes while maintaining their ability to provide people with places for recreation as well as products such as fuel wood and maple syrup.

Part 1/Part 2

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Please feel free to report any observations to Lorraine Julien at naturewatching@gmail.com  or Steve Blight at natureobservations@rogers.com