Monday, September 27, 2021

Old growth trees and forests

By Larry Cornelis – President, Sydenham Field Naturalists

“Primordial – existing at or from the beginning of time, Primeval – of the earliest time in history.”

These are the words that come to my mind when walking through an old growth forest
or standing beside an old growth tree.

I have toured some impressive sites, such as Cathedral Grove on Vancouver Island and the Joyce Kilmer Memorial Forest in North Carolina.

Submitted photo

So, what makes an old growth forest or an old growth tree?

Well, obviously time, time measured in centuries.

That time results in certain characteristics that distinguish old growth forests and trees.
In eastern North America, a tree is considered old growth starting at about 150 years of
age.

By that age trees, mainly deciduous trees, exhibit certain features that help to identify
them as old growth.

Of course, the older a tree is the larger it is but the largest trees in the forest may not be the oldest when you consider different species.

Not too many soft maples or poplars live to 150+ years but they can get very large.

Basically, the fastest growing soft wood species do not live as long as the slower growing hardwoods such as ash, elm, sugar maple, oak and hickory.

Although the largest oak in the forest may not be the oldest.

It depends on genetics, soil type, moisture levels and weather/climate conditions.

Submitted photo

Some of our hardwoods can live to over 500 years old.

The characteristics that distinguish an old growth tree from younger trees are balding bark; stag-headed crown; moss on bark and size.

Balding bark is a condition that starts at approximately 150 years of age.

The bark, having been through that many seasons, becomes impacted by ranging temperatures, rain, freezing and thawing and eventual decomposition.

This causes the coarse bark of old trees to shed, leaving a smoother ‘bald’ surface that is easily observed.

This starts at the base of the tree, (the oldest part of the tree) and then goes up the
trunk with age.

The older the tree the higher the balding reaches.

A rough guess is five or six feet of balding may be 200 years old.

That’s just a guideline.

If most of the trunk appears bald/smooth it may be 350+ years old.

Stag-headed basically describes what the crown of a tree looks like after being through dozens of severe storms, both wind and ice, therefore losing branches in the crown.

The crown eventually looks open with large, crooked branches which resembles the antlers of a stag.

And moss, starting at the base of a tree grows slowly up the trunk and generally the higher the moss is found on the trunk, the older the tree.

Of course, counting growth rings is the only way to know exactly how old a tree is, and I count growth rings at every opportunity when I see that a tree has been cut down.

The characteristics of an old growth forest include the presence of extremely large trees (obviously) and an undulating topography of the forest floor.

This undulating topography is called ‘pit and mound’.

This is the result of old super canopy trees being blown over in severe windstorms.

The tree topples over pulling the roots up.

The roots bring soil with them and create a pit (which holds water and hydrates the landscape).

When the roots and trunk eventually decompose, there is a mound of soil and compost left behind.

Hence the name ‘pit and mound’.

Locally, this can be observed at Clear Creek Forest and Rondeau Provincial Park and further afield, at Backus Woods.

For more details, visit: http://www.sydenhamfieldnaturalists.ca/

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