Friday, March 16, 2007

Tree Protection Zones

Tree Hording? Tree Protection Zones? City By-laws? Arborist reports?

(Picture: A big old healthy White Spruce in Northern Ontario. Estimated 40 feet in diameter and to be 80 to 100 years old)

In relation to my "Gone are the days" post a few weeks ago, I write this post as a brief follow up on the topic. In the Urban Landscapes, City forestry is doing their best to protect the older and mature trees that are over 30 cm in caliper size.

Tree Hording is a protective barrier that is built with plywood and 2 x 4 frames... set up to prevent construction materials, equipment, excavation activity and any other vehicles from entering a tree protection zone.

Tree protection zones are designated areas of protection for the root system of a tree. What determines how big that protection area will be? The caliper (diameter) of the tree trunk size. For instance, a 35 cm caliper tree will have a 2.4 meter radius set up around it as a protection zone.

Why protect the tree so far out? Roots are delicate! The tree acclimatizes the soil around it and adjusts the conditions in its favour for optimal growing. Imagine a 2 ton bundle of house bricks being stored on top of its roots? Or a 4 ton machine parked or driving over the root zone? Essentially the soil structure gets compacted and air spaces below the surface around the roots will be crushed.

The roots can be damaged and cause the tree to go into stress as it can no longer take up nutrients like it has always done.

(Picture: This roadway was widened and paved... causing the giant sugar maple on the right of the road to fall under stress and it eventually had to be cut down.)

So... by-laws are now in place to preserve the giants of our urban landscapes. In some places those by-laws are a slap on the wrist and in others they are a deep and hurtful pinch to the wallet.

Arborist reports are made to advise the general state or conditions of trees on a site slated for construction. The report covers how big a tree protection zone needs to be and what if any special needs or protective measures that particular tree may need to continue a long and healthy life. The report may also explain reasons for removal of a specific tree deemed hazardous or unsafe... or just simply in the way of construction progress. City forestry has the ultimate say on removal issues.

Get to know your city's by-laws regarding tree protection before you start digging or chopping!


darling24_7 said...

Very interesting.

I wonder if they take offence at my calling them tree doctors.

Learn something new every day :)

Paul said...

Actually another term for an Arborist is a "Tree Surgeon".

darling24_7 said...

Ahhh I was thinking of that too but that seemed too specific somehow. :)

I take my dogs to the Environmental Farm here in Ottawa and I love that the trees always look beautiful. Ill now marvel at whats under my feet as I walk.

Anonymous said...

How very very cool! As a botanist I am all in favor of keeping as many things green and growing as we can--Hurrah for urban forestry!