Old Growth Forests: Part 2 of 2

Steve Bight | Nov 26, 2009

What landowners can do

The first column on old growth forests published on November 12 described some of the features and benefits of old growth forests. This column will look at some of things that landowners can do 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.

Typical features of old growth forests include plenty of large diameter trees of a variety of species, lots of large dead tree trunks and branches on the forest floor, smaller trees growing underneath the canopy of mature trees and a rich layer of mosses, fungi, ferns and other low-growing plants on the ground. While it may not be possible to recreate conditions exactly as they were before European settlement of our area in the 18th and 19th century, it is possible to recreate some old growth features.

The easiest approach to restoring old growth forests is to leave the forest alone for a century or two so natural processes can transform second growth forests into old-growth ecosystems. However, since landowners are generally humans, they don’t have this much time. For faster results in forests that also provide people with valuable wood products, you can take a more active approach. This involves three simple strategies: creating gaps in the forest canopy, rebuilding a rich layer of decaying organic matter on the forest floor and protecting wildlife trees and large trees from harvest.

In the past, natural events like fire, ice storms, and disease outbreaks created openings in the canopy, allowing sunlight to penetrate into the lower layers of the forest so new growth could occur. You can mimic these natural disturbances and speed the process of natural succession by creating “holes” in the canopy from time to time. Small canopy gaps (about 10 meters, or about 30 feet across) encourage the growth of shade-tolerant species like beech and sugar maple; medium gaps (up to 50 meters, or about 150 feet across) encourage mid-tolerant trees like oak and white pine, and large openings encourage shade intolerant species like birch and poplar. Canopy gaps should be separated by about 50 meters and be at least 50 meters into the stand. Trees harvested to create the gaps can provide a flow of wood products. You can increase the diversity of forests by protecting long-lived conifers like white pine and hemlock and uncommon species like hickory and black cherry from harvest so that they can provide seed for natural regeneration.

The floor of an old-growth forest is a moist, fertile, rough and varied environment, with lots of decaying wood, leaves, twigs and other organic matter. When fallen trees and other organic matter decompose on the forest floor they create habitat and return nutrients and energy to the soil. Organic matter builds up on the forest floor, retaining moisture and transforming the drier second-growth forest into a moister, old-growth environment. Decaying logs provide habitat for bacteria, fungi, mosses, ferns and wildflowers and germination sites for trees such as yellow birch and hemlock. They are also home to amphibians and reptiles. Leave at least ten fallen logs in each hectare of forest, or about four for every acre. The logs should be greater than two metres (about six feet) in length and 60 centimetres (about two feet) in diameter. If you don’t have enough, let snags fall naturally or cut down some unsafe, undesirable or unhealthy trees.

Wildlife trees are trees and shrubs that are particularly important for providing birds and mammals with food, shelter and havens from predators. Wildlife trees include cavity trees, snags and mast trees.

Cavity trees are living or dead trees with holes for nesting or denning, feeding and escaping. Leave at least six living cavity trees greater than 25 centimetres (10 inches) in each hectare of forest. Bigger cavities are better because they provide homes for a greater number of species.

Mast trees are trees whose fruit or seeds provide important food for wildlife. Some of the best mast species include oak, beech, butternut, hickory, black cherry, pin cherry, serviceberry and mountain ash. Leave at least seven mast trees in each hectare, or three per acre.

Snags are standing dead trees. Leave as many snags as possible, but aim for a minimum of four smaller snags and one larger snag that is greater than 50 centimetres (about 20 inches) in diameter in every hectare of forest.

Finally, the presence of large trees is one of the most attractive features of an old-growth forest. In each hectare, leave at least three large trees greater than 50 centimetres in diameter.

These guidelines are just a few things that can be done to help recreate old growth conditions in Land O’ Lakes forests. If you find yourself interested in learning more about this subject, I would strongly encourage you to consult the extension notes referred to in the first paragraph.

Part 1/Part 2

Please feel free to report any observations to Lorraine Julien at This email address is being protected from spambots. You need JavaScript enabled to view it.  or Steve Blight at This email address is being protected from spambots. You need JavaScript enabled to view it.